Nanocomposite and method for preparing same

文档序号：834706 发布日期：2021-03-30 浏览：29次中文

阅读说明：本技术 纳米复合材料及其制备方法 (Nanocomposite and method for preparing same ) 是由王铁胜斯托扬·K·斯莫科夫傅强高丽君于 2019-08-08 设计创作，主要内容包括：本发明涉及制备客体@纳米多孔主体材料的方法,以及根据这些方法制备的客体@纳米多孔主体材料。根据本发明的方法包括以下步骤：在反应环境中使一种或多种试剂和目标客体前体渗透纳米多孔主体材料以发生反应,从而在纳米多孔主体材料的孔内形成目标客体物质。所述试剂包括氧化还原试剂和/或pH调节剂。通过分析适当的电化学势与pH值关系图并仔细选择适当的试剂并控制工艺条件以从选定的目标客体前体中制备出所需的目标客体颗粒,由于与已知方法相比通常可以使用更温和的反应条件,因此这种形成客体的合成策略比已知方法更加灵活和通用。(The invention relates to a method for preparing an object @ nano porous host material, and the object @ nano porous host material prepared according to the method. The method according to the invention comprises the following steps: one or more reagents and a target guest precursor are caused to permeate the nanoporous host material in a reaction environment to react to form a target guest species within the pores of the nanoporous host material. The reagent includes a redox reagent and/or a pH adjusting agent. This guest-forming synthesis strategy is more flexible and versatile than known methods, since milder reaction conditions can generally be used compared to known methods, by analyzing appropriate electrochemical potential versus pH diagrams and carefully selecting appropriate reagents and controlling process conditions to produce the desired target guest particles from the selected target guest precursors.)

1. A method for preparing a guest @ nanoporous host material, comprising the steps of:

providing a nanoporous host material comprising a plurality of pores interconnected by pore windows;

selecting a target guest substance on a graph of the relation between the electrochemical potential and the pH value;

determining a suitable target guest precursor by determining a phase on the plot of electrochemical potential versus pH;

selecting one or more suitable reagents;

infiltrating the agent into the nanoporous host material to form an agent @ nanoporous host material, or infiltrating the target guest precursor into the nanoporous host material to form a precursor @ nanoporous host material; and

allowing said target guest precursor to permeate said reagent @ nanoporous host material in a reaction environment or allowing said one or more suitable reagents to permeate said precursor @ nanoporous host material to react to form said target guest species within the pores of said nanoporous host material;

wherein one or more of the reagents comprises:

(i) a redox reagent selected to modulate an electrochemical potential of the reaction environment by Δ E, wherein Δ E is determined as a difference in electrochemical potentials operable to change the electrochemical potential of the reaction environment from a stable region of the target guest precursor on the electrochemical potential versus pH plot to a stable region of the target guest species on the electrochemical potential versus pH plot; and/or

(ii) A pH adjuster selected to adjust a pH of the reaction environment by a Δ pH, wherein the Δ pH is determined as a difference in pH, operable to move the pH of the reaction environment from a stable region of the target guest precursor on the electrochemical potential versus pH plot to a stable region of the target guest species on the electrochemical potential versus pH plot.

2. A method for preparing a guest @ nanoporous host material, comprising the steps of:

providing a nanoporous host material comprising a plurality of pores interconnected by pore windows, and selecting a target guest substance for the nanoporous host material, the target guest substance being capable of being plotted on a graph of an associated electrochemical potential versus pH;

providing a suitable target guest precursor, said target guest precursor being a phase that can be plotted on said electrochemical potential versus pH;

providing one or more suitable reagents;

allowing said target guest precursor to permeate said reagent @ nanoporous host material or allowing said one or more suitable reagents to permeate said precursor @ nanoporous host material in a reaction environment to react to form said target guest species within the pores of said nanoporous host material;

wherein one or more of the reagents comprises:

(i) a redox reagent that modulates an electrochemical potential of the reaction environment by Δ E, wherein Δ E is determined as a difference in electrochemical potential operable to change the electrochemical potential of the reaction environment from a stable region of the target guest precursor on the electrochemical potential versus pH plot to a stable region of the target guest species on the electrochemical potential versus pH plot; and/or

(ii) A pH adjuster that adjusts the pH of the reaction environment by a Δ pH, wherein the Δ pH is determined as a difference in pH, operable to move the pH of the reaction environment from a stable region of the target guest precursor on the electrochemical potential versus pH graph to a stable region of the target guest species on the electrochemical potential versus pH graph.

3. The method according to claim 1 or 2, wherein said method comprises performing a temperature controlled desorption step to at least partially desorb reagent molecules from the outer surface of said reagent @ nanoporous host material or said precursor @ nanoporous host material.

4. A method for preparing a guest @ nanoporous host material, comprising the steps of:

providing a nanoporous host material comprising a plurality of pores interconnected by pore windows;

selecting a target guest substance and determining a suitable target guest precursor;

selecting one or more suitable reagents, including a redox reagent and/or a pH adjusting agent;

performing a temperature-controlled desorption step to cause at least partial desorption of reagent molecules from the outer surface of said reagent @ nanoporous host material or said precursor @ nanoporous host material; and

the target guest species is then formed within the pores of the nanoporous host material by infiltrating the agent @ nanoporous host material with the target guest precursor or infiltrating the precursor @ nanoporous host material with the one or more suitable agents to react the target guest precursor with the agent.

5. The method of any one of the preceding claims, wherein the nanoporous host material is a mesoporous or microporous material.

6. The method of any one of the preceding claims, wherein the nanoporous host material is selected from the group consisting of: metal organic framework materials, covalent organic framework materials, zeolites, porous silica, silicones, activated carbon, carbon nanotubes, or microporous polymer materials.

7. The method of any one of the preceding claims, wherein the one or more suitable reagents comprise both a redox reagent and a pH adjusting agent.

8. The method of any one of the preceding claims, wherein one or more of the reagents is hydrophobic.

9. The method of claim 5, wherein the step of infiltrating the nanoporous host material with the agent to form an agent @ nanoporous host material and infiltrating the agent @ nanoporous host material with the target guest precursor is performed in an aqueous solution.

10. The method of any one of the preceding claims, wherein the target guest substance and target guest precursor are based on a target element selected from the group consisting of: be, B, Mg, Al, Si, P, S, Ca, Ga, Ge, As, Se, Sr, In, Sn, Sb, Te, Ba, Tl, Pb, Bi, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, W, Re, Os, Ir, Pt, Au, Hg, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr, Ds, Ra, Rf, Db, Sg, Bh, Hs, Mt, Ds, Cn, Fl or Lv.

11. The method of claim 7, wherein the target guest substance and target guest precursor are based on a target element selected from the group consisting of: transition metals, rare earth elements, alkaline earth metals, post-transition metals, metalloids or non-metals, preferably transition metals or rare earth elements.

12. The method of any one of claims 3 to 11, wherein the temperature-controlled desorption step comprises: heating said reagent @ nanoporous host material or said precursor @ nanoporous host material at a temperature of from 20 ℃ to 300 ℃.

13. The method of any one of claims 3 to 12, wherein the temperature-controlled desorption step comprises: the reagent @ nanoporous host material or the precursor @ nanoporous host material is heated for 1 second to 48 hours, optionally 10 minutes to 2 hours.

14. The method according to any one of claims 3 to 13, wherein the temperature controlled desorption step is carried out at a pressure below atmospheric pressure.

15. A guest @ nanoporous host material prepared according to the process of any one of claims 1 to 14.

16. Use of the guest @ nanoporous host material of claim 15 as a catalyst.

17. A guest @ nanoporous host material prepared by infiltrating a nanoporous host material with one or more reagents and a target guest precursor in a reaction environment to react to form a target guest species within pores of the nanoporous host material;

wherein one or more of the reagents comprises:

(i) a redox reagent that modulates an electrochemical potential of the reaction environment by Δ E, where Δ E is determined as a difference in electrochemical potentials operable to change the electrochemical potential of the reaction environment from a stable region of the target guest precursor to a stable region of the target guest species; and/or

(ii) A pH adjuster to adjust a pH of the reaction environment by a Δ pH, wherein the Δ pH is determined as a difference in pH operable to move the pH of the reaction environment from a stable region of the target guest precursor to a stable region of the target guest species.

Technical Field

The invention relates to a nanocomposite and a preparation method thereof. In particular, but not exclusively, to guest @ nanoporous host materials and methods of making the same.

Background

In a nanoporous host^[1-4](e.g., inorganic porous materials)^[4,5]Metal Organic Polyhedrons (MOP)^[6,7]Metal Organic Framework (MOF)^[1-4]Zeolite, porous Silica (SiO)₂) Organosilicates, activated carbon, etc.) to form a composite material, generally denoted by the term "guest @ nanoporous host material", is a known strategy for preparing functional nanocomposites. This strategy allows for highly active and stable heterogeneous catalysts, as well as robust photo/electroluminescent materials with tunable band structures under quantum confinement. This is theoretically achieved because the growth of the guest entity is limited and incorporation is prevented^[8-14]。

The term "X @ Y" is used generally within the art and in this disclosure to express the concept of X being inside Y. Thus, the term "guest @ nanoporous host material" refers to a nanoporous host material that includes a guest compound within (within the pores of) the nanoporous host material. Alternative notation/terminology used to denote the same concept includes "nanoporous host materialsGuest ".

Much work has been done in this area. Taking the Ru-based guest @ nanoporous materials as an example, since the early 1990 s, many combinations have been realized, such as:

ru @ Y type zeolite^[15]

·[email protected]^[16]

Perruthenate @ MCM-41 (mesoporous silica)^[17]

·RuO₂@ faujasite^[18]

Ru-organic Complex @ MOF^[19–21]

Meanwhile, several metal @ MOF systems have been investigated, particularly for CO oxidation, such as:

·[email protected]^[22]

·[email protected]^[23]

·Co₃O₄@ZIF-8^[24]

·[email protected][Ce(BTC)(H₂O)]·DMF^[25](wherein BTC is 1,3, 5-benzenetricarboxylic acidCarboxylic acid and DMF is dimethylformamide).

Metal Organic Frameworks (MOFs) are host matrices with a highly diverse chemical structure, topology and pore structure, but are less chemically and thermally stable. It is generally believed that forming a guest (especially including oxides, hydroxides, sulfides, nitrides, and phosphides) that is much larger than the pores (also commonly referred to as windows) in a MOF host (and certain other nanoporous hosts) is a challenging, sometimes even impossible, task. In situations where it is desirable to form an object larger than the aperture window, it is often referred to in the art as a "bottle-in-bottle" assembly. The usual "bottled boat" method is by solution-based, gas-phase or mechanical mixing impregnation followed by thermal decomposition/irradiation decomposition or with strong reducing agents (e.g. hydrazine (N)₂H₄)、NaBH₄Or H₂) A redox reaction occurs to load the metal salt and organometallic precursor into the open-celled framework of the preformed host material^[8-14]。

Disclosure of Invention

Part of the insight of the inventors is to find that one problem in current bottle-ship systems is poor controllability when growing nano-entities (guests) within a nanoporous host. In most cases, the metal matrix guest portion is deposited in large amounts on the outer surface of the host material along the bonding route after assembly^[13]. Since the behavior of the object may be very different when confined in the nanocavity^[12]Thus, depositing guests inside and outside the nanoporous body can significantly increase the bias and uncertainty in the characterization and exploration of the confined and induced behavioral changes. In addition, significant loading of the exterior of the host material may be detrimental to the performance of such materials (e.g., catalysts).

In addition, the use of strong reducing agents and the reaction conditions required to form these guests in currently known methods risks damaging or destroying the nanoporous host structure. This is especially a problem for metastable MOF host materials.

The present invention has been devised in view of the above considerations.

By reviewingSystems (e.g. Metal-H)₂O and metal-H₂S) Pourbaix diagram (electrochemical potential-pH diagram)^[26,27]The present inventors have recognized that when the electrochemical potential and/or pH of the reaction environment is selected to match the reaction requirements, it may be determined from a suitable precursor (e.g., in the case of metal-H)₂Oxoanions (M) of the O system_xO_y ^z-) And in metal-H₂Sulfur metal anion (M) in S system_xS_y ^z-) ) preparing an insoluble guest. In the present disclosure, "reaction environment" generally refers to the environment in which the reaction occurs. The reaction environment may most often be a liquid environment, such as in an aqueous or other solution, but other reaction environments, such as a gaseous environment, are also contemplated.

The Pourbaix plot indicates the stability of a particular available oxidation state of a composition (e.g., a metal) in terms of electrochemical potential versus pH. At a particular combination of pH and electrochemical potential, the stable phase can be determined from the Pourbaix diagram. The Pourbaix map is constructed according to calculations based on the Nernst equation, as described below in relation to FIG. 33.

The present inventors have realized that this synthesis strategy for forming a guest is more flexible and versatile than known methods, since milder reaction conditions can generally be used compared to known methods, by analyzing appropriate electrochemical potential-pH diagrams and carefully selecting appropriate reagents and controlling process conditions to produce the desired target guest particles from the selected target guest precursors.

Furthermore, the inventors have also realized that by performing an additional temperature control step during the preparation method, guest compounds can be incorporated into the cavities of the nanoporous body in a more controllable manner than known methods.

Accordingly, in a first aspect, there is provided a process for the preparation of a guest @ nanoporous host material, comprising the steps of:

providing a nanoporous host material comprising a plurality of pores interconnected by pore windows;

selecting a target guest substance on a graph of the relation between the electrochemical potential and the pH value;

determining a suitable target guest precursor by determining a phase on the plot of electrochemical potential versus pH;

selecting one or more suitable reagents;

wherein one or more of the reagents comprises:

One or more suitable agents may first be infiltrated into the nanoporous host material to form the agent @ nanoporous host material, and then the target guest precursor may be infiltrated into the agent @ nanoporous host material. Alternatively, the target guest precursor may first be infiltrated into the nanoporous host material to form the precursor @ nanoporous host material, and then one or more agents may be infiltrated into the precursor @ nanoporous host material. The order of permeation of the target guest precursor and the agent may affect the final properties, e.g., morphology, of the guest @ nanoporous host material.

In a second aspect, there is provided a method of making a guest @ nanoporous host material, comprising the steps of:

providing a suitable target guest precursor, said target guest precursor being a phase that can be plotted on said electrochemical potential versus pH;

providing one or more suitable reagents;

wherein one or more of the reagents comprises:

As described above in relation to the first aspect, the nanoporous host material may first be infiltrated with one or more suitable agents to form the agent @ nanoporous host material, and then the target guest precursor may be infiltrated with the agent @ nanoporous host material. Alternatively, the target guest precursor may first be infiltrated into the nanoporous host material to form the precursor @ nanoporous host material, and then one or more agents may be infiltrated into the precursor @ nanoporous host material.

In a third aspect, there is provided a guest @ nanoporous host material prepared by infiltrating a nanoporous host material with one or more reagents and a target guest precursor in a reaction environment to react to form a target guest species within pores of the nanoporous host material;

wherein one or more of the reagents comprises:

As described above with respect to the first and second aspects, the nanoporous host material may first be infiltrated with one or more suitable agents to form the agent @ nanoporous host material, and then the target guest precursor may be infiltrated with the agent @ nanoporous host material. Alternatively, the target guest precursor may first be infiltrated into the nanoporous host material to form the precursor @ nanoporous host material, and then one or more agents may be infiltrated into the precursor @ nanoporous host material. The above strategy has the particular advantage that it is possible to operate under relatively mild conditions without the need for the host to have a specific chemical functionality/specific material chemistry (e.g. chemical functionality/use of ionic host materials)^[28,29]In advance of formation ofA range of guest species are formed within nanoporous hosts (e.g., MOFs and zeolites). In other words, these reactions can be carried out without grafting, wherein the chemical precursor is chemically bonded to the functionalizable portion of the host material. This is because the selection of redox reagents and/or pH adjusters according to the desired Δ E and/or Δ pH allows the preparation of the target guest substance without the use of harsh redox reagents, such as hydrazine or NaBH₄。

The relevant electrochemical potential versus pH diagram is that of a suitable system, taking into account the certainty of the target guest substance and the proposed reaction environment. The graph of electrochemical potential versus pH may be a Pourbaix graph. For example, when the guest substance of interest is a metal oxide (e.g., RuO)₂) And the proposed reaction environment is an aqueous solution, the metal-H₂The graph of the electrochemical potential versus pH for the O system is a Pourbaix graph. However, the present invention is not necessarily limited to any particular system. Theoretically, the principles presented herein are generally applicable to any target guest/reaction environment combination that can provide a plot of electrochemical potential versus pH. Campbell, J.A.&Whiteker,R.A.“A periodic table based on potential-pH diagrams”.J.Chem.Educ.46,90(1969)^[27]Some examples of electrochemical potential vs pH plots for a range of different systems are described in (a).

The term "stability region" is used herein to describe the boundary region of the associated electrochemical potential versus pH plot in which the indicated species is stable. Referring to FIG. 33, there is shown Ru-H₂Pourbaix diagram of O system, wherein the target guest substance is RuO₂The target guest precursor is RuO₄ ^-The stable region of the target guest substance is labeled "RuO₂·2H₂A region of O'. The stable region of the target guest precursor is labeled "RuO₄ ^-"is used herein. May then be removed from the RuO by a dehydration process₂·2H₂Obtaining RuO from O₂. Thus, since any substance is stable in any particular system over electrochemical potentials and pH ranges, Δ E and Δ pH may have respective readings, as understood by the skilled artisanA range of values.

In a fourth aspect, there is provided a method of making a guest @ nanoporous host material, comprising the steps of:

providing a nanoporous host material comprising a plurality of pores interconnected by pore windows;

selecting a target guest substance and determining a suitable target guest precursor;

selecting one or more suitable reagents, including a redox reagent and/or a pH adjusting agent;

As mentioned above, one may first infiltrate one or more suitable agents into the nanoporous host material to form the agent @ nanoporous host material and then infiltrate the target guest precursor into the agent @ nanoporous host material. Alternatively, the target guest precursor may first be infiltrated into the nanoporous host material to form the precursor @ nanoporous host material, and then one or more agents may be infiltrated into the precursor @ nanoporous host material.

By desorbing the reagent or precursor molecule from the outer surface of the reagent @ nanoporous host material or precursor @ nanoporous host material, the surface loading of the target guest species on the host material can be reduced. In addition, the method can also better control the inclusion of the guest in the host material than existing methods, thereby allowing the amount of guest loading in the host to be adjusted. Desorption may be the desorption of some or all of the reagent or precursor molecules from the outer surface of the reagent @ nanoporous host or precursor @ nanoporous host material. Preferably, more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the reagent or precursor molecules may be desorbed from the outer surface of the host material. In some cases, up to 100% of the reagent or precursor molecules may be desorbed from the outer surface of the nanoporous host material. The extent of desorption may be measured using any suitable technique, for example by thermogravimetric analysis (TGA). The extent of desorption can be determined either (i) directly from the weight mass loss versus temperature curve or (ii) from the area under the differential weight curve versus temperature curve.

The term "nanoporous material" as generally used herein refers to a material having a pore size of 100nm or less. Preferably, the nanoporous material is a mesoporous or microporous material. Mesoporous materials, as defined by IUPAC, are materials that contain pores and have a cavity diameter between 2 and 50 nm. Typical mesoporous materials include, for example, porous silica, silicones, and activated carbon. Microporous materials are materials that contain pores and have a cavity diameter of less than 2 nm. Examples of microporous materials include, for example, zeolites, metal organic framework materials, and covalent organic framework materials. The consistency of the nanoporous material is not particularly limited, but is preferably selected to be stable with respect to the metal precursor throughout the proposed synthesis method. Different nanoporous host materials can be selected depending on the particular application in which the guest @ nanoporous host material is used. Preferably, the nanoporous host material is selected from: MOF (also known as Porous Coordination Polymer (PCP)) materials, COF materials, zeolites, porous silica, silicones, activated carbon, carbon nanotubes, or microporous polymeric materials (e.g., intrinsically microporous Polymers (PIMs), Conjugated Microporous Polymers (CMP)). Preferably, the pore size of the nanoporous material is 0.5nm to 10 nm. Most preferably, the nanoporous host material is a MOF material or a zeolite.

As used herein, "permeate" or "impregnate" means that the substance penetrates or enters the pores of the nanoporous host material. Some or all of the pores of the nanoporous host material may be infiltrated with an osmotic agent. Thus, the diameter of the species that permeates into the nanoporous host material (e.g., the target guest precursor, and any other reagents needed to form the target guest species within the pores) should be no greater than the diameter of the pore size of the nanoporous material (sometimes referred to as the "window"). The target guest species itself need not have a diameter that allows permeation because the target guest species is formed in situ within the pores. In practice, the diameter of the target guest substance is preferably larger than the diameter of the pores. Once the target guest substance is formed in situ, it is prevented from leaving the pores of the host material.

Furthermore, the substances that penetrate into the nanoporous host material (e.g., the target guest precursor, and any other reagents needed to form the target guest substance within the pores) should be in a fluid state, i.e., should be a gas, liquid, or solution. The substance may naturally be present in a fluid state under the process conditions (i.e. as a gas or liquid under the process conditions) or may be placed in a mobile state by dissolving the substance in a suitable solvent prior to the permeation step. The appropriate solvent will depend on the exact nature of the osmotic agent. For example, suitable solvents may include: water or other aqueous solutions; organic solvents (aromatics (e.g., benzene and toluene), alcohols (e.g., methanol, ethanol), esters, ethers, ketones (e.g., acetone), amines, nitrated halohydrocarbons, dimethylformamide, dimethylsulfoxide); or ionic liquids (ionic liquids based on ammonium, imidazolium, phosphonium, pyridinium, pyrrolidinium, sulfonium cations).

For certain nanoporous materials (e.g., MOFs), at least some of the pores may have different diameters in different directions. In this case, the diameter of the guest substance is preferably not substantially larger than the diameter of the pores in at least one direction. Furthermore, it is noted herein that certain nanoporous materials (e.g., MOFs) may have structural flexibility such that substances slightly larger than the pores may still be accommodated into the pores through the pores. Preferably, the pore diameter is 0.5nm to 10 nm.

The size of the pores of the nanoporous host material may be determined by the crystal structure, for example using single crystal X-ray diffraction methods well known to those skilled in the art. Some examples are shown in fig. 2 of Jiao et al (2016) and fig. 2 of Ma and Balbuena (2012). Or may be determined in a manner well known to the skilled person by means of, for example, SEM or micro-computer tomography (micro-CT).

Where the permeant is an ion, the diameter of the permeant (e.g., the target guest precursor or agent) can be determined based on the effective ionic radius while taking into account the ionic center and the solvating shell. Depending in part on the solvent. The effective ionic radius may be determined according to the method disclosed in Michov (2013), referred to herein as the motor radius. As described in N.Y. Chen et al, where the osmotic agent is non-ionic, the diameter may be defined as the "critical Molecular diameter," i.e., the diameter of a cylinder that can circumscribe the molecule in the most favorable equilibrium configuration, see N.Y. Chen et al (1994), "Molecular Transport and Reaction in Zeolites: Design and Application of Shape Selective Catalysis". John Wiley & Sons, Inc., channel 5.1.2, page 133.

The target guest substance is not particularly limited. Preferred target guest materials are metal-containing materials. The target guest substance may be based on a target element selected from the periodic table, except for elements of the rare gas group (group 0). Preferably, the target guest substance is based on a target element selected from the group consisting of: be, B, Mg, Al, Si, P, S, Ca, Ga, Ge, As, Se, Sr, In, Sn, Sb, Te, Ba, Tl, Pb, Bi, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, W, Re, Os, Ir, Pt, Au, Hg, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr, Ds, Ra, Rf, Db, Sg, Bh, Hs, Mt, Ds, Cn, Fl and Lv. These target elements can be classified into the following categories: transition metals, rare earth elements, alkaline earth metals, post-transition metals, metalloids or non-metals (see, e.g., https:// www.livescience.com/28507-element-groups.

More preferably, the target guest substance is based on a target element selected from transition metals or rare earth elements. Rare earth elements are particularly preferred due to their photoelectric (e.g., phosphorescent) properties and magnetic properties. The target guest species may be, for example, a metal, metal alloy, oxide (including hydrous oxide), hydroxide, sulfide, nitride, or phosphide. Preferably, the target guest species is a metal or metal alloy, or an oxide, hydroxide, or sulfide species.

The target guest precursor is also not particularly limited, but it must be a suitable precursor of the target guest substance. Thus, the target guest precursor may also be based on a target element selected from the periodic table, in addition to elements of the rare gas group (group 0). Preferably, the target guest substance is based on a target element selected from the group consisting of: be, B, Mg, Al, Si, P, S, Ca, Ga, Ge, As, Se, Sr, In, Sn, Sb, Te, Ba, Tl, Pb, Bi, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, W, Re, Os, Ir, Pt, Au, Hg, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr, Ds, Ra, Rf, Db, Sg, Bh, Hs, Mt, Ds, Cn, Fl and Lv. More preferably, the target guest substance is based on a target element selected from transition metals or rare earth elements. Rare earth elements are particularly preferred due to their photoelectric (e.g., phosphorescent) properties and magnetic properties. The target guest precursor is preferably an ionic species. Preferably, the target guest precursor is, for example, an oxyanion (A)_xO_y ^z-) Cation (A)^x+) (e.g., halides, sulfates, etc.), H_xA_yO_z ^n-、A_x(OH)_y ^z-、A_xS_y ^z-、H_xA_yS_z ^n-、A_x(SH)_y ^z-And H_xA_yO_zS_m ^n-Where A is the target element and x, y, z, m and n are numbers including 0. Preferably, the target guest precursor is soluble in an aqueous solution. The target guest precursor is soluble in other solvents. For example, the target guest precursors may be soluble in organic solvents, including, but not limited to, aromatics (e.g., benzene and toluene), alcohols (e.g., methanol, ethanol), esters, ethers, ketones (e.g., acetone), amines, nitrated halohydrocarbons, dimethylformamide, dimethyl formamideA sulfoxide base). The target guest precursor may be dissolved in the ionic liquid, including but not limited to: ionic liquids based on ammonium, imidazolium, phosphonium, pyridinium, pyrrolidinium, sulfonium cations.

The one or more suitable reagents may comprise both a redox reagent and a pH adjuster. In some cases, one reagent may act as both a redox reagent and a pH adjuster.

The pH adjusting agent may be generally defined as a proton (H)⁺) Any species of acceptor or donor, and may be, for example, an acid or a base. The pH adjusting agent may be selected to control the pH of the reaction environment within a stable region of the target guest substance on a plot of electrochemical potential versus pH value associated with the reaction environment, taking into account the electrochemical potential of the reaction environment. In other words, the pH adjusting agent may be selected to adjust the pH of the reaction environment by a Δ pH, where the Δ pH is determined as the difference between the pH of the stable region of the target guest substance and the stable region of the target guest precursor. The pH adjusting agent may be an organic acid or an organic base. Examples of the organic base include: pyridine, alkylamine, imidazole, benzimidazole, histidine, guanidine, phosphazene base and hydroxide. Examples of the organic acid include: formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caprylic acid, oxalic acid, lactic acid, malic acid, citric acid, benzoic acid, carbonic acid, phenol, uric acid, and taurine.

The redox reagent may be selected to control the electrochemical potential of the reaction environment within a stable region of the target guest substance on a plot of the electrochemical potential versus pH value associated with the reaction environment, taking into account the pH of the reaction environment. In other words, the redox reagent may be selected to modulate the electrochemical potential of the reaction environment by Δ E, where Δ E is determined as a difference in electrochemical potential operable to change the electrochemical potential of the reaction environment from a stable region of the target guest precursor to a stable region of the target guest species. The redox reagent may be an oxidizing agent or a reducing agent. The Δ E of the redox reagent can be determined using, for example, standard electrochemical cyclic voltammetry tests, in which the redox potential of a particular half-cell reaction is measured.

Preferably, one or more of the agents is hydrophobic. This may be particularly advantageous when the agent is caused to penetrate the nanoporous host material to form the agent @ nanoporous host material, and the step of causing the guest precursor of interest to penetrate the agent @ nanoporous host material is carried out in an aqueous solution, as the agent will tend to remain in the pores of the nanoporous host, rather than leaching out. This helps control the loading of the target guest in the nanoporous host material. However, it is not necessary that one or more of the reagents be hydrophobic. In some cases, none of the reagents are hydrophobic. In some cases, one or more of the agents may alternatively or additionally be hydrophilic.

The temperature controlled desorption step may comprise heating the reagent @ nanoporous host material or precursor @ nanoporous host material at a temperature, for example, from above 20 ℃ to below 500 ℃. The upper limit of the temperature-controlled desorption step is mainly controlled by the thermal stability and the decomposition temperature of the host material. For example, for MOF host materials, the upper temperature limit may be about 250 ℃ to 300 ℃. However, it may be higher for the zeolite host material. Preferably, the temperature controlled desorption step is carried out at a temperature of from 20 ℃ to 300 ℃. More preferably, the temperature controlled desorption step is carried out at a temperature of from 50 ℃ to 250 ℃. Most preferably, the temperature controlled desorption step is carried out at a temperature of from 100 ℃ to 150 ℃. The use of higher temperatures allows greater desorption of the agent from the outer surface of the nanoporous host material. However, this may also promote desorption of the reagent from the interior of the pores of the nanoporous host material, particularly in the peripheral regions of the host material. Therefore, an appropriate temperature should be selected to balance these two factors.

The temperature controlled desorption step may comprise heating the reagent @ nanoporous host or precursor @ nanoporous host material, for example, for 1 second to 48 hours, for example, for 10 minutes to 2 hours. The temperature controlled desorption step may comprise heating the reagent @ nanoporous host or precursor @ nanoporous host material from 1 second or more, 10 seconds or more, 1 minute or more, 10 minutes or more, or 1 hour or more to 48 hours or less, 36 hours or less, 24 hours or less, 12 hours or less, 4 hours or less, or 2 hours or less. The precise amount of time required for the temperature-controlled desorption step is not particularly limited. Preferably, the length of time chosen should be long enough to allow satisfactory desorption of molecules to occur outside the host, while also being short enough to prevent significant loss of molecules from occurring within the host. It should be noted that: generally, (i) for the same molecule, the higher the temperature, the shorter the time; (ii) at the same temperature, the smaller the molecule, the shorter the time; (iii) at the same temperature, the weaker the attractive interaction of the molecule with the host, the shorter the time.

The pressure at which the temperature-controlled desorption step is performed may also affect the extent of desorption. Although it is preferred to perform this step at ambient pressure, in some cases it may be advantageous to perform the temperature controlled desorption step at low pressure to assist desorption. Low pressure is defined herein as any pressure below atmospheric pressure (101325 Pa).

Performing a temperature controlled desorption step can result in greater desorption of the reagent or precursor from the outer surface of the nanoporous host material. However, this may also promote desorption of the reagent or precursor from the interior of the pores of the nanoporous host material, particularly in the peripheral regions of the host material. Therefore, this step should be performed for an appropriate length of time to balance these two factors.

The temperature-controlled desorption step can be carried out in an inert atmosphere, for example in N₂In an atmosphere or in an Ar atmosphere. This helps to ensure that the reagent @ nanoporous host material or precursor @ nanoporous host material does not undergo any unwanted chemical reactions during this step.

In a fifth aspect, there is provided a guest @ nanoporous host material prepared according to the method of the first, second or fourth aspect above.

In a sixth aspect, there is provided the use of the guest @ nanoporous host material of the fifth aspect as a catalyst.

The invention includes the described aspects and combinations of preferred or optional features unless combinations are explicitly not allowed or should be explicitly avoided.

Drawings

Examples and experiments to illustrate the principles of the present invention will now be discussed with reference to the accompanying drawings, in which:

fig. 1a (i), fig. 1a (ii), fig. 1b and fig. 1c together provide a microstructure and preparation profile of a material according to an embodiment of the invention and a material for comparison.

FIG. 2 shows (a) HR-TGA normalized weight vs. temperature curves and (b) the differential of weight loss (weight loss with increasing temperature) vs. temperature curves for dry MOF, DE @ MOF, tBMP/DE @ MOF (tBMP excess) and tBMP/DE @ MOF (tBMP excess) after treatment at about 120 ℃.

FIG. 3 shows HR-TGA results (differential of weight loss versus temperature curve) for tBMP/DE @ MOF-808-P with different tBMP: MOF-808-P mass ratios.

FIG. 4 shows (a) the Ru element weight fraction as measured by ICP-OES, indicating adjustable guest loading; (b) from RuO₂Measurement of the weight fraction (wt%) of Ru in @ MOF-808-P₂Adsorption; (c) a computer generated structural model of MOF-808-P showing primary and secondary pore structures; (d) cumulative pore volume for pore width for each sample.

FIG. 5 shows a graph based on the reference^[30]Simulated MOF-808, synthetic MOF-808-P, dried MOF-808-P, and synthetic RuO of₂The PXRD pattern for @ MOF-808-P.

FIG. 7 shows a graph based on the reference^[31]The simulated structure and octahedral morphology of MOF-808 as described in (1).

FIG. 8 shows the synthesized RuO₂The X-ray photoelectron Spectroscopy (XPS) survey of @ MOF-808-P.

FIG. 9 shows the synthesized RuO₂XPS Ru 3P of @ MOF-808-P_3/2Spectrum of light.

FIG. 11 shows (a) high resolution DF-STEM (HR-DF-STEM) images; (b) in the same wayThe highlighting in the image hasDiffraction-striped particles (about 1.5nm in diameter); (c) simulated RuO₂An XRD spectrum; and (d) RuO₂Two potential diffraction planes, d spacing of

FIGS. 12 (a) and (b) show Ru/SiO at different magnifications₂HRTEM image contrast of the material.

FIG. 13 shows Ru/SiO₂(Next, a simulated Ru peak is provided) and oxidized forms thereof (RuO)₂/SiO₂) (above, simulated RuO is provided₂Peaks) XRD pattern.

FIG. 14 shows RuO before and after CO adsorption at 30 ℃₂/SiO₂(Red) and RuO₂In situ X-ray absorption Spectroscopy results of @ MOF-808-P (blue) (Ru foil and RuO)₂As a reference sample).

FIG. 15 shows in situ DRIFTS spectra of MOF-808-P treated in reaction gas and then in Ar at 30 ℃.

FIG. 16 shows MOF-808-P, tBMP @ MOF-808-P and RuO₂CO Oxidation test of @ MOF-808-P.

FIG. 17 shows the use of O at 30 ℃₂Activated RuO₂/SiO₂And RuO₂Stability test with @ MOF-808-P (test conditions: 400L/g)_RuH, 15mg catalyst).

Figure 18 shows the extended DRIFTS results of figure 31 (d).

FIG. 20 shows RuO₂CO Oxidation test of @ MOF-808-P, in standard O₂After activation, the test (stage 1) was carried out by treatment with 10 v/v% steam at 100 ℃ for 60 minutesAfter which the test is carried out again (stage 2).

FIG. 21 shows preliminary XRD results for manganese oxide (MnOx) in DUT-67 MOF.

FIG. 22 shows preliminary SEM-EDX results for manganese oxide (MnOx) in DUT-67 MOF.

FIG. 23 shows RuO in zeolite Y from Alfa Aesar₂Preliminary XRD results of (a).

FIG. 24 shows RuO in zeolite Y from Alfa Aesar₂Preliminary SEM-EDX results of (1).

FIG. 25 shows preliminary XRD results for manganese oxide (MnOx) in MOF-808-P.

FIG. 26 shows preliminary SEM-EDX results for manganese oxide (MnOx) in MOF-808-P.

FIG. 27 shows Pourbaix plots of Pt ([ Pt ]]＝10^-2mol kg^-1(total aqueous mixture)).

FIG. 28 shows Pourbaix plot of Pd ([ Pd ]]＝10^-2mol kg^-1(total aqueous mixture)).

FIG. 29 shows DR-STEM images of Pd @ MOF-808-P and its corresponding STEM-EDS spectra for Zr and Pd.

FIG. 30 shows a PXRD pattern for MOF-808-P and Pd-loaded MOF-808-P (i.e., Pd @ MOF-808-P).

FIG. 31 shows O₂Activated RuO₂/SiO₂(blue) and RuO₂CO and O in @ MOF-808-P (Red) and RuO₂Characteristics and profiles of the interaction of the guest.

FIG. 32 shows Ru/SiO activated with Ar₂Or O₂Activated RuO₂/SiO₂And RuO₂CO Oxidation catalytic Performance Profile of @ MOF-808-P: (a) 15mg of catalyst was used at 2000L/g_RuA CO conversion curve at Weight Hourly Space Velocity (WHSV)/h, (b) an Arrhenius diagram and a calculated apparent activation energy (Ea), and (c) quantitative analysis of chemisorbed CO at-50 ℃ (to prevent CO formation during measurement)₂) And conversion frequency (TOF, conversion per unit time per unit site), (d) use of O at 100 ℃. (ii)₂Activated RuO₂/SiO₂And RuO₂@MOF-808-P(2000L/g_RuH, 15mg of catalyst) was carried outAnd (5) testing the stability.

FIG. 33 shows Ru-H₂Pourbaix diagram of O system, indicated by RuO₄ ^-Formation of aqueous RuO₂ ^[26,27]。

Detailed description of the invention

Aspects and embodiments of the invention will now be discussed with reference to the drawings. Other aspects and embodiments will be apparent to those skilled in the art. All documents mentioned herein are incorporated herein by reference.

1. Summary and summary

Summary of the disclosure the following disclosure of preferred embodiments of the invention: the Pourbaix synthesis method disclosed herein combines position control of the guest precursor with theoretical predictive synthesis, and is based on various reactions that can be synthesized from the element-H₂O, element-H₂S, element-H₂O-H₂S system or even expanded element-NH₃And element-PH₃Pourbaix class diagram of architecture (e.g., Ru-H as shown in FIG. 33₂O system diagram showing the result of RuO₄ ^-Formation of aqueous RuO₂ ^[26,27]) To obtain a versatile synthesis strategy for a variety of active catalyst guests, such as metals, metal alloys, oxides, hydroxides, sulfides, nitrides, and phosphides. The function of such guest need not be limited to a catalyst. Alternative functions include the use in optoelectronic materials such as Light Emitting Diodes (LEDs), lasers, scintillators, and photosensors. The inventors suggest that this rational approach to generic guest function in any MOF host not only could be applied, but could be a fundamental research platform to limit both function and host-guest interactions.

In particular, the proposed method provides in a preferred embodiment the guest RuO₂Method of catalyst confinement in MOF bulk, resulting in RuO at low temperatures₂An apparently abnormal CO/O adsorption behavior and a pronounced CO oxidation behavior. In particular, in RuO₂In @ MOF-808-P, it was observed that (i) when CO and O were present₂Adsorption on RuO₂When on the surface of the object, knotThe resultant interaction is significantly reduced; (ii) inhibiting the formation of dense CO domains, especially at temperatures of 150 deg.C or less. Thus, the regulation of adsorption caused by this limitation renders RuO, which is normally susceptible to deactivation at low temperatures due to surface passivation₂Keep activity in CO oxidation reaction (conversion rate after continuous reaction for 12 hours)>97%). In general, it has been demonstrated that techniques for controllably incorporating a guest into any nanoporous host allow for the study of a variety of host-guest systems with surprising functionality.

Other further results indicate that similar advantages, particularly those resulting from improved loading control, are more generally obtained for guest @ nanoporous host materials prepared according to the method of the invention.

Fig. 1 provides a microstructure and preparation overview of materials according to embodiments of the invention and materials for comparison. FIG. 1(a) shows the synthesis of RuO in the cavities/pores of a preformed MOF-808-P using the hydrophobic reducing agent 2-tert-butyl-4-methylphenol (tBMP)₂Schematic representation of (a). The complete process will be discussed below, but in brief, a pre-formed MOF material (MOF-808-P) is provided and impregnated with a selected redox reagent (here tBMP in ether, DE, solvent). Optionally, a temperature-controlled selective desorption is carried out. The tBMP @ MOF material was then used with perruthenate ions (RuO) in aqueous solution₄ ^-) Infiltration to form RuO as target guest material in situ₂. FIG. 1a (ii) provides the illustrated key information used in FIG. 1a (i).

As shown in FIG. 1(b), RuO can be controlled using temperature-controlled tBMP molecular selective desorption₂To reduce and/or eliminate RuO on the outer surface of the MOF₂Is performed. Dark field scanning transmission electron microscopy (DF-STEM) image right side shows particles outside (above) MOF crystals and clean MOF crystal edges (below). Furthermore, even without using temperature selective desorption, RuO formed on the outer surface, as compared with other known methods₂The particles also have a unique structure-they form a spherical "shell". This is due to tBMP and KRuO during the synthesis₄Hydrophobic interaction of aqueous solutions.

FIG. 1(c) shows the guest as supported in MOF (i.e., RuO)₂) Measured N₂Adsorption isotherms. The results show that the amount of guest is related to the amount of tBMP loaded in the MOF, which is controlled by the relative amounts of tBMP and the volatile diethyl ether solvent used to carry the tBMP. In parentheses are given relative to synthetic RuO₂The relative Ru weight percent of @ MOF-808-P was calculated by inductively coupled plasma emission spectrometry (ICP-OES).

₂Experiment and characterization of 2 RuO @ MOF-808-P

₂2.1 rational design of RuO @ MOF-808-P

In a first example, RuO₂Synthesized within the MOF. This process is schematically illustrated in fig. 1a (i) - (ii). According to the Ru-based Pourbaix diagram^[27,32]Selecting perruthenate and potassium perruthenate (KRuO)₄) As a precursor. As shown in the Pourbaix diagram of FIG. 33, it can be reduced to form aqueous RuO₂. Selecting a water-resistant MOF, i.e. MOF-808-P^[30]KRuO can be used as the main component₄The aqueous solution is subjected to precursor impregnation. Based on { Zr with spn topology₆O₈Cluster, MOF-808-P [ Zr ]₆O₅(OH)₃(BTC)₂(HCOO)₅(H₂O)₂BTC ═ 1,3, 5-benzenetricarboxylic acid ester]Due to its water stability, 3D open porosity and relatively large cavity and pore diameters (respectively of the order ofAnd) Providing a useful nanoporous body. Due to the slave RuO₄ ^-(aq) Domain formation RuO₂·2H₂O(RuO₂Preform of (b) is only about 0.2V (as Ru-H of fig. 33)₂O Pourbaix diagram), so a small lipid, tBMP (chemical properties similar to the well-known antioxidant lipid, Butylated Hydroxytoluene (BHT) was chosen^[33,34]) About 0.3V is required for partial curing) because it is sufficient to maintain RuO in a controlled pH range (in this case, the measured value is from about pH 8.5 to about pH 5.5 before and after the reaction)₄ ^-Reduction to RuO₂·2H₂And O. tBMP is hydrophobic (i.e. immiscible with water).

And usually the metal precursor is introduced first^[8,9,13]Unlike the conventional "bottled ship" method of achieving metal @ MOF, we first loaded a solution of tBMP in Diethyl Ether (DE) so that we could use a temperature-controlled selective desorption method (which will be discussed in more detail below)^[35,36]) To remove all DE and tBMP on the outer surface of the MOF (see fig. 2, discussed further below). Since tBMP is hydrophobic, with KRuO₄(aq) solution impregnation and tBMP with KRuO₄Reaction, resulting in hydrophobic-hydrophilic interaction restriction, resulting in tBMP staying inside. Thus produced aqueous RuO₂Clusters/particles are trapped inside the MOF. The product was washed with water and ethanol. Then dehydrated under nitrogen at about 200 ℃ to obtain synthetic RuO₂@ MOF-808-P. Meanwhile, KRuO can be controlled₄Mass ratio to MOF-808-P to adjust RuO₂And confirmed by nitrogen adsorption measurements and inductively coupled plasma emission spectroscopy (ICP-OES) (see fig. 4 discussed below). More detailed experimental procedures are provided below.

2.2 materials

1,3, 5-benzenetricarboxylic acid (H)₃BTC，ACROS Organics^TM98%), zirconium oxychloride octahydrate (ZrOCl)₂·8H₂O，ACROS Organics^TM98 +%), N-dimethylformamide (DMF, Fisher Scientific, 99.7 +%, HPLC), formic acid (HCOOH, Fisher Scientific, 98 +%), absolute ethanol (C)₂H₅OH, Fisher Scientific, 99.5 +%, HPLC), Milli-Q water, 2-tert-butyl-4-methylphenol (tBMP, ACROS Organics)^TM99%), diethyl ether (DE, ACROS Organics)^TM99 +%, ACS reagent, anhydrous), potassium perruthenate (VII) (KRuO₄Alfa Aesar, 97%) andpolyamide membrane filter (0.2 μm), Y-type zeolite (Alfa Aesar, Si: Al: 80: 1).

2.3 preparation of MOF-808-P

MOF-808-P [ Zr ] was synthesized based on the MOF reported by Furukawa et al₆O₅(OH)₃(BTC)₂(HCOO)₅(H₂O)₂BTC ═ 1,3, 5-benzenetricarboxylic acid ester]^[31]. Detailed protocols can be found in Jiang et al, report 2014^[37]. Briefly, 0.467g H is first placed₃BTC and 2.16g ZrOCl₂·8H₂O was dissolved in DMF/HCOOH solvent (100ml DMF +100ml HCOOH). The solution was kept at 130 ℃ for 48 hours. The MOF particles formed were collected, washed 3 times with DMF and washed in Milli-Q^TMKept in water for 3 days. The washed MOF particles (slurry) were collected by filtration and dried gently at 50 ℃ to remove most of the water. It was further dried at 150 ℃ under a stream of dry nitrogen for about 3 hours. After drying, the MOF structure remained as shown by powder X-ray diffraction (PXRD) (fig. 5).

2.4 tBMP impregnation and temperature-controlled selective desorption

To impregnate tBMP in MOF-808-P, MOF was immersed in tBMP solution (DE as solvent). The amount of tBMP is controlled to have an adjustable guest loading relative to the MOF used (see fig. 3 and 4). For example, to obtain a sample for CO oxidation catalysis, 50mg tBMP (in 1000. mu.l DE) was mixed with 500mg MOF-808-P. The prepared tBMP/DE @ MOF-808-P is called tBMP/DE @ MOF-808-P (2:20), wherein 2:20 is the mass ratio of tBMP to MOF-808-P in the process of impregnating the tBMP. Then the prepared tBMP/DE @ MOF-808-P is added in N₂The stream was heated at 120. + -. 5 ℃ for about 1 hour to remove the DE and tBMP from the exterior of the MOF. This is a temperature-controlled selective desorption process that has been developed based on experience with polymer formation in MOFs^[35,36]The process is further explained by high resolution thermogravimetric analysis (HR-TGA), as shown in figure 2.

FIG. 2 shows dry MOF, DE @ MOF, tBMP/DE @ MOFHR-TGA curves of (tBMP excess) and tBMP/DE @ MOF (tBMP excess) after treatment at about 120 ℃: the normalized weight versus temperature curve (upper) and the derivative of the weight loss (weight loss with increasing temperature) versus temperature curve (lower). The step-down in the upper graph and the peak in the lower graph may indicate multiple desorption/decomposition events, respectively. The desorption temperature of tBMP outside the MOF is lower than that inside the MOF because the interaction is stronger when the molecules are trapped inside the nanoporous body. This is in agreement with the previously observed analogous systems for the preparation of the polymers @ MOF^[35,36]. Thus, when the prepared tBMP/DE @ MOF-808-P is treated at about 120 ℃, most of the DE (volatile solvent for tBMP) and tBMP (outside the MOF) can be removed. In this way, only the tBMPs inside the MOF body can remain after treatment, i.e., tBMP @ MOF-808-P.

After treatment, the sample became tBMP @ MOF-808-P. Samples with different guest loadings were prepared to demonstrate the loading strength (see figure 4). Their corresponding HR-TGA results are given in FIG. 3.

FIG. 3 shows HR-TGA results (differential of weight loss versus temperature curve) for tBMP/DE @ MOF-808-P with different tBMP: MOF-808-P mass ratios. When the mass ratio of tBMP to MOF-808-P reaches 4:20 [ i.e., tBMP/DE @ MOF-808-P (4:20) ], the maximum loading of tBMP inside MOF has been reached. This can be seen by: (i) there was a distinct peak at about 100 ℃ (tBMP desorption outside MOF) and (ii) a peak similar to tBMP/DE @ MOF-808-P (3:20) at about 200 ℃ (tBMP desorption inside MOF).

₂2.5 RuO formation inside MOF-808-P

The prepared tBMP @ MOF-808-P was collected and reweighed. Preparation of KRuO based on the Mass of tBMP @ MOF-808-P₄Solutions (aqueous solutions, [ KRuO)₄]20mM) to hold n (KRuO)₄) N (tBMP) (i.e., the molar ratio) is at least 2: 1. Here we overestimate the tBMP quantity by assuming that all tBMP added initially is already loaded into the MOF. By reacting tBMP @ MOF-808-P with KRuO₄Solution mixing to form aqueous RuO in MOF₂. Since tBMP is immiscible with the aqueous solution, tBMP will be trapped in the MOF during the reaction. At the same time, the user can select the desired position,KRuO uptake by partially filled MOF bodies₄Solution and containing tBMP-KRuO therein₄And (4) carrying out oxidation-reduction reaction.

During the reaction, KRuO₄Reduction to RuO₂And tBMP is oxidized to its oxidized derivative, similar to the oxidation of BHT^[33,34]. Liquid chromatography-mass spectrometry (LC-MS) analysis confirmed the presence of the ketone derivative. We kept the reaction for about 4 hours. After the reaction, the product was collected by filtration (the filtrate remained yellow, indicating that some KRuO remained after the reaction₄) And washed with excess ethanol followed by water. Then dried at 120 ℃ to obtain the synthesized RuO₂@ MOF-808-P. After synthesis, white MOF-808-P became nearly black RuO₂@ MOF-808-P. At the same time, we verified that MOF-808-P itself does not interact with KRuO₄Reaction, since MOF-808-P remained white and KRuO after mixing₄There was no change in color in the solution. We confirmed that MOF-808-P was stable throughout the sample preparation process because there was no significant change in PXRD pattern, as described in FIG. 5 below. Synthetic RuO₂@ MOF-808-P is stable in air and can be stored under ambient conditions.

FIG. 4 shows the reaction by ICP-OES and N₂Adjustable guest loading determined from adsorption measurements: (a) by changing tBMP and KRuO added₄[n(KRuO₄) N (tBMP) is maintained at about 2:1]We can achieve different guest loadings as can be seen from the ICP-OES measured elemental weight fraction of Ru. (b) We observed that when more guest was incorporated (i.e., RuO)₂) (from ICP-OES), synthetic RuO₂N of @ MOF-808-P₂Accessible surface area reduction (from N)₂Adsorption measurements). N during adsorption measurements when more pores in the MOF are heavily filled with guest₂Less space is available. Thus, the measured surface area decreases and the measured pore volume also decreases, which is shown in (c) and (d). The parentheses in the sample label in (d) indicate the weight fraction of Ru element measured by ICP-OES.

FIG. 5 shows a graph based on the reference^[37]Simulated MOF-808, synthetic MOF-808-P, dried MOF-808-P, and synthetic RuO of₂@MPXRD pattern OF-808-P. Incorporation of RuO₂The structure of the MOF is then preserved. Does not show RuO₂Peak of crystal, indicating RuO₂The particles are very small (<3nm)^[22]。

FIG. 6 shows the synthesized RuO₂A (a) Scanning Electron Microscope (SEM) image of @ MOF-808-P; and (b) an associated energy dispersive X-ray energy spectrum (SEM-EDS) ensemble spectrum and (C) Zr, (e) Ru, (d) C and (f) O. The loading of the Ru-based guest in the Zr-based MOF host was verified. Since the sample powder is immobilized on the carbon tape, a relatively strong C signal is observed in the background.

FIG. 7 shows a graph based on the reference^[31]The simulated structure and octahedral morphology of MOF-808 as described in (1). The simulation structure shown in FIG. 7(a) was generated using Mercury (https:// www.ccdc.cam.ac.uk/sources/csd-system/components/marcuring /). FIG. 7(b) shows the synthesized RuO₂The (b) dark field scanning transmission electron microscope (DF-STEM) image of @ MOF-808-P; and (c) Zr and (d) Ru. The contrast of the Zr-based host and Ru-based guest is similar because Zr and Ru interact with electrons similarly. Relative EDS signal intensity is provided to show the elemental 2D distribution. The high intensity areas are indicated by white arrows. The loading of the Ru-based guest in the Zr-based MOF host was further verified. It can be seen that Zr is present in the greatest amount in the central portion of the MOF crystal, while Ru is present in the greatest amount in the peripheral regions of the MOF crystal.

FIG. 8 shows a synthetic RuO₂The X-ray photoelectron Spectroscopy (XPS) survey of @ MOF-808-P. Further validation of Ru (from RuO)₂Guest), Zr (from MOF-808-P host), O (from guest and host), and C (mainly from host).

FIG. 9 shows the synthesized RuO₂XPS Ru 3P of @ MOF-808-P_3/2Spectrum (at 3 p)_3/2Photoelectron spectra on spin orbitals that can indicate ruthenium electrons). Synthetic RuO₂@ MOF-808-P with Ru at about 463.2eV^IV(+4) is mainly^[38,39]. We also observed shoulders with higher binding energy, which is likely to be the formation of aqueous RuO during sample storage or after exposure to air₂Object (Presence-OH)^[38,40]。

FIG. 10 shows Ru foil, anhydrous RuO₂And synthetic RuO₂Fourier Transform (FT) K of X-ray absorbing Fine Structure (XAFS) of Ru K boundary (about 22.1keV) @ MOF-808-P²The weighted χ (k) function results are obtained by ex situ X-ray absorption spectroscopy (XAS). In RuO₂In the @ MOF-808-P material, the apparent Ru-O pair can be identified as the peak just below 2R, but there is no peak in the metal Ru that corresponds to the Ru-Ru pair (probably the Ru foil sample peaked just below 3R). And reference RuO₂In contrast, in RuO₂The shift of the edge peak can be observed in @ MOF-808-P. This may be due to the presence of C (organic ligand from MOF) in the vicinity of Ru^[41]。

FIG. 11 shows (a) high resolution DF-STEM (HR-DF-STEM) images; (b) highlighting in the same image hasDiffraction-striped particles (about 1.5nm in diameter); (c) simulated RuO₂An XRD spectrum; and (d) RuO₂Two potential diffraction planes, d spacing ofThe contrast of the Zr-based host and Ru-based guest is similar because Zr and Ru interact with electrons similarly. The presence of small particles is consistent with the PXRD pattern of fig. 5, since PXRD does not show very small particles^[22]. At the same time, the pitch of the diffraction fringesWith RuO₂D in (1)_(011),(101)Or/and d_(200),(020)The plane matching is good.

₂2.6 characterization method of RuO @ MOF-808-P

HR-TGA: TGA was performed with a TA Instruments Q500 thermogravimetric analyzer. The sample was heated from room temperature to 900 ℃ (i.e., high resolution mode) according to the mass loss adjustment rate per unit temperature change in Ar.

Nitrogen adsorption measurement: n passage at 77K Using Autosorb and Nova Quantachrome apparatus₂The samples were analyzed by adsorption. The sample was degassed under vacuum at 120 ℃ overnight. Pore structure and surface area were calculated by the software novawin (quantachrome) using different estimates of the surface (Brunauer Emmett Teller and density function theory). Assuming the geometry of the slit and cylindrical hole, the Pore Size Distribution (PSD) is calculated from the isotherm adsorption line using the quenched solid model QSDFT. Ravikovitch et al^[42]The quenched solid state functional theory (QSDFT) is described.

PXRD: powder XRD patterns were collected on Bruker D8 ADVANCE using Ni 0.012 filters (2 theta between 3.5 ° and 80 ° step size 0.04 °) between the X-ray source and the sample. The samples were evenly distributed on a silicon disc supported by a circular support. During the measurement, the holder and the disc were rotated (30 rpm). The illumination area was fixed so that the exposure area formed a circle (16 mm diameter) with rotation.

Scanning Electron Microscope (SEM) and its associated energy dispersive X-ray energy spectrum (SEM-EDS): using FEI Nova NanoSEM with secondary electron detector and EDS detector^TMSecondary electron SEM (SE-SEM) images and energy dispersive spectroscopy (SEM-EDS) spectra (electron acceleration voltage: 15kV) were obtained.

Dark field scanning transmission electron microscope (DF-STEM) and its associated energy dispersive X-ray energy spectrum (STEM-EDS): STEM images were acquired on a FEI Osiris, the apparatus operated at a voltage of 200keV, equipped with a Bright Field (BF) and Annular Dark Field (ADF) detector. Energy dispersive spectra were recorded simultaneously on four Bruker silicon drift detectors. The diffraction patterns were recorded on a Gatan UltraScan1000XP CCD camera. STEM samples were prepared by drop casting 100. mu.l of sample suspension (ground sample powder dispersed in ethanol) onto a carbon mesh.

X-ray photoelectron spectroscopy (XPS): x-ray photoelectron spectra were acquired using a monochromatic AlK α 1X-ray source (hv ═ 1486.6eV) with a SPECS PHOIBOS 150 electron energy analyzer, with a total energy resolution of 500 meV. Measurements were performed using a monochromatic AlK α X-ray source (1486.6 eV). To eliminate charging effects during the measurement, a low energy electron flood gun with appropriate energy is used. All spectra were calibrated at 284.8eV C1 s. To analyze the Ru 2p3/2 spectrum, the linear background was subtracted.

Ectopic X-ray absorption spectrum (XAS): the measurement of the X-ray absorption spectrum was performed on the BL14W1 beam line of the shanghai synchrotron radiation apparatus (SSRF). The spectrum at the Ru K edge was recorded in transmission mode. Samples were coated on carbon tape or in plastic sample bags for characterization.

ICP-OES: the metal loading of Ru was measured in all samples by inductively coupled plasma emission spectrometer (7300DV, Perkin Elmer). The catalyst (5-10mg) was digested by microwave dissolution in aqua regia and HF solution.

LC-MS: accurate mass measurements of BMP oxidation products were made by coupling an Accela Liquid Chromatography (LC) system to a Waters 50mm BEH C18 column connected to a Q-active Plus mass spectrometer. For each test, 100 μ L samples were analyzed using a 20 minute gradient of (a) water and (B) acetonitrile, each containing 0.1% formic acid. The flow rate of the mobile phase was 400. mu.m/min. After 1 minute at 90% a isocratic, the gradient was moved from 90% to 5% a for 10 minutes, then held at 5% for 2 minutes, then returned to the original condition within 2 minutes, and then held for another 5 minutes for column regeneration. For both electrospray and atmospheric pressure ionization, ionization was performed at the positive and negative electrodes. At a temperature of 350 ℃, the atomization airflow is 70L/h, and the drying airflow is 450L/h. Data collection and analysis were performed using Xcalibur v 2.0 software from Thermo Scientific.

₂ ₂Experiment and characterization of 3 RuO/SiO comparative reference material

₂ ₂3.1 experiment with RuO/SiO

Sample preparation

Using RuCl₃RuO supported on commercial silica particles (non-porous) was prepared by a conventional impregnation method as a precursor (Mimeos Chemicals, Tianjin, China)₂NPs (Qingdao ocean chemical company)^[42]. The nominal loading of Ru in the catalyst was maintained at 10 wt%. Fresh catalyst (RuCl)₃Attached to SiO₂On the granule) Drying in an oven at 63 deg.C overnight, and then drying with H at 250 deg.C₂Reduction (70ml/min) for 2h (in Ru/SiO₂Form provisioning). Before carrying out the catalytic activity test, the catalyst was treated with O at 250 deg.C₂(30ml/min) Oxidation for 1h (as RuO)₂/SiO₂Is provided in the form of (a).

Method for characterizing materials

TEM: RuO was obtained on a JEM-2100 microscope operating at an accelerating voltage of 200kV₂/SiO₂TEM image of (a). TEM samples were prepared by drop casting 100. mu.l of sample suspension (the milled sample powder dispersed in ethanol) onto a copper mesh.

PXRD: use of Cu Ka on an Empyrean diffractometerThe radiation source collects RuO at 40kV and 40mA and at a scan rate of 12 °/min₂/SiO₂PXRD pattern of (a).

3.2 supporting characterization results

FIGS. 12 (a) and (b) show Ru/SiO at different magnifications₂HRTEM image of material. Ru nanoparticles are uniformly distributed on SiO₂The average diameter of the support is from about 3 μm to about 5 μm on the surface thereof.

FIG. 13 shows Ru/SiO₂(Next, a simulated Ru peak is provided) and oxidized forms thereof (RuO)₂/SiO₂) (above, simulated RuO is provided₂Peaks) XRD pattern. The results show that O is carried out at 250 ℃₂After oxidation, the metallic Ru is oxidized to RuO₂. The peak at 23 ℃ is attributed to amorphous SiO₂。

4 experimental and supporting results of surface adsorption and CO Oxidation tests

In heterogeneous catalysis, both the surface structure and the adsorption of molecules on the catalyst surface have a significant impact on the catalytic performance. One of the typical reactions that help to understand the importance of molecular interactions with metal-containing catalysts is CO oxidation, which is also one of the main goals of respiratory protection and air purification. In thatRuO due to surface passivation at low temperature₂The surface is generally considered to be a poor catalyst for CO oxidation. In that<At a temperature of 150 ℃, the main mechanism of oxidation is the Langmuir-Hinshelwood process^[43-46]Wherein adsorbed CO is dissociated with O₂The substances (i.e. O atoms) combine to produce CO₂. However, CO and O species are in RuO₂The adsorption of which causes them to bind strongly and form tightly packed CO and O domains, the limited surface desorption and diffusion of these two species leading to low catalytic activity^[46]. However, the material prepared according to the invention is such that RuO is a solid₂Are controllably encapsulated in the cavities of MOF-808-P and exhibit unusual molecular adsorption behavior and enhanced low temperature catalyst activity. For reference, we prepared silica-supported RuO₂Catalyst (RuO)₂/SiO₂) The catalyst is synthesized by a conventional impregnation method^[47]And discussed above in connection with fig. 12 and 13. Characterization of restricted and unrestricted RuO by diffuse reflection Fourier transform Infrared Spectroscopy (DRIFTS) and Temperature Programmed Reduction (TPR)₂And (3) a nano catalyst. RuO₂/SiO₂And RuO₂The @ MOF-808-P samples all contained about 10 wt% Ru.

4.1 general characterization methods in this section

In-situ XAS: in-situ XAS measurements were also made on SSRF BL14W1 beam lines. The spectra were recorded in transmission mode. By RuO₂@ MOF-808-P and Ru/SiO₂Samples were prepared as self-supporting pellets and processed directly in an in situ sample cell made of quartz. The heating element is wrapped around the sample cell so that the sample can be heated at different temperatures. The temperature was controlled by a type K thermocouple in contact with the sample cell. Prior to XAS measurements, samples were tested with 20 v/v% O₂+80 v/v% He activation at 150 ℃ for 10 min (RuO)₂@ MOF-808-P) or activation at 250 ℃ for 1h (RuO)₂/SiO₂) And cooled to 30 ℃ under argon. First collecting O₂Spectrum of the activated sample. Mixing O with₂The comparative spectra were collected after the activated samples were treated with a gas stream of 5 v/v% CO +95 v/v% He for 30 minutes at 30 ℃.

In-situ diffuse reflectance fourier transform infrared spectroscopy (in-situ DRIFTS): in situ DRIFTS spectra were recorded on a BRUKER tesser 27 spectrometer equipped with a diffuse reflecting accessory (Praying Mantis) and a reaction chamber (operating temperature-150 ℃ to 600 ℃). The powder samples were loaded into sample cups. The sample temperature was controlled by a heater and measured by two thermocouples, one in the sample cup and one in the sampling station. The flow rate through the reaction chamber is controlled by a mass flow controller.

For FIG. 31b, 5 v/v% CO +95 v/v% He was used. The samples were first exposed to 5% CO at room temperature and then reduced to-50 ℃ by liquid nitrogen and held for 2h (RuO)₂@ MOF-808-P) or 1h (RuO)₂/SiO₂) Until no change in the infrared spectrum was observed. The gas was then switched to Ar gas at room temperature and the sample temperature was increased to the target temperature. After 10 minutes of reaching each target temperature, the corresponding DRIFTS spectra were collected.

For FIGS. 31c and 31d, the samples were taken at 20 v/v% O prior to taking the DRIFTS₂+80 v/v% Ar Pre-treatment at 150 ℃ for 10 min (RuO)₂@ MOF-808-P) or pretreatment at 250 ℃ for 1h (RuO)₂/SiO₂) And cooled to room temperature in Ar. To adsorb the reaction gas (1 v/v% CO +20 v/v% O)₂+79 v/v% He), first O₂The activated sample was exposed to the reaction gas for 30 minutes at room temperature. It was heated to the target temperature (i.e., 30 ℃, 100 ℃ and 150 ℃) in Ar for 10 minutes and then the DRIFTS spectra were collected.

Using 4cm^-1Spectral resolution DRIFT spectra were recorded and 32 scans were accumulated.

Temperature Programmed Reduction (TPR): the temperature-programmed reduction was carried out by a microparticle chemisorption analyzer (Auto Chem 2910) equipped with a mass spectrometer (MS, Omnistar). With 20 v/v% O₂+80 v/v% Ar samples were pretreated at 150 ℃ for 10 min (RuO)₂@ MOF-808-P) or pretreatment at 250 ℃ for 1h (RuO)₂/SiO₂) And then changed to helium. After cooling to 45 ℃ in He, the treated sample was exposed to 5 v/v% CO +95 v/v% He for 30 minutes. The sample was then heated from 45 ℃ to 800 ℃ at a ramp rate of 10 ℃. The product was analyzed by online mass spectrometry.

CO pulse chemical adsorption: CO pulse chemisorption was performed using a particulate chemisorption analyzer (Auto Chem 2920). With 20 v/v% O₂+80 v/v% Ar samples (30mg) were pretreated at 150 ℃ for 10 min (RuO)₂@ MOF-808-P) or pretreatment at 250 ℃ for 1h (RuO)₂/SiO₂) And then changed to helium. After cooling to-50 ℃ in He, the treated sample was exposed to a CO pulse consisting of 5 v/v% CO in equilibrium with He. The flow rate of all gases was set to 30 ml/min. The CO concentration was measured using a thermal conductivity detector.

4.2 CO Oxidation test

The catalyst was loaded into a fixed bed microreactor. RuO before catalytic activity₂@ MOF-808-P and Ru/SiO₂The catalyst was exposed to O at a flow rate of 30ml/min₂(O₂Activated) or Ar (Ar activated) gas, and treated at 150 ℃ for 10 minutes (activated RuO formation), respectively₂@ MOF-808-P) and treatment at 250 deg.C for 1 hour (formation of activated RuO)₂/SiO₂). After cooling to room temperature in argon (30ml/min), the gas flow was switched to a specific Weight Hourly Space Velocity (WHSV) of the reaction gas (1% CO, 20% O in equilibrium with He)₂And 1% N₂). WHSV of FIG. 3a was 2000Lg_Ru ^-1h^-1. The catalytic performance study was conducted by programming the temperature at a rate of 1 deg.C/min or holding at a specific temperature for 12 hours. Use is provided withAn on-line micro gas chromatograph (Agilent GC-490) of a molecular sieve column and Thermal Conductivity Detector (TCD) analyzed the gas products. For the apparent activation energy measurement, the CO oxidation reaction was performed within a kinetic confinement zone, where CO conversion was less than 25% using a larger WHSV.

For the stability test (results are shown in fig. 31(d)), the catalyst was treated with 100 ℃ water and 30mg of the catalyst was loaded into a fixed-bed microreactor. RuO was tested prior to activity testing₂Reaction gases for the @ MOF-808-P catalyst (1% CO and 20% O)₂And He) at 150 c for 10 minutes. In thatAfter cooling to room temperature under argon, the gas was switched to WHSV 400Lg_Ru ^-1h^-1The reaction gas of (2) was subjected to an activity test. The catalyst was then treated with 10% water, with water injected with a syringe pump (LEAD flud, TYD03) for 1h at 100 ℃. The line from the pump to the reactor was heated at high temperature. After the catalyst was treated with water, the catalyst was exposed to argon gas at 120 ℃ for 60 minutes. The activity test is carried out at a temperature of 30 ℃ to 100 ℃ at a heating rate of 0.5 ℃/min. The gas products were analyzed by an on-line gas chromatograph (Agilent GC 6890) equipped with packed columns PQ200 and TCD. Before product analysis, the water was ice-cooled.

4.3 supporting the results

FIG. 14 shows RuO before and after CO adsorption at 30 ℃₂/SiO₂(Red) and RuO₂In situ X-ray absorption Spectroscopy results of @ MOF-808-P (blue) (Ru foil and RuO)₂As a reference sample). XANES indicates that RuO₂/SiO₂And RuO₂Both the @ MOF-808-P are partially reduced after CO adsorption, as can be seen from the slope change of the near-edge region (highlighted in grey). We speculate that RuO is performed at 30 deg.C₂The oxygen bridge in (1) is replaced by CO. However, in surface reduction, RuO₂@ MOF-808-P to RuO₂/SiO₂More reduction is performed. The results show that by limiting RuO₂Ru-O interactions can be attenuated in MOFs. Furthermore, it also supports our STEM/TEM results, namely RuO encapsulated in MOF₂(FIG. 11) is smaller than SiO₂Loaded RuO₂(FIG. 12) due to RuO in MOF₂Has a higher surface area to volume ratio.

FIG. 15 shows in situ DRIFTS spectra of MOF-808-P treated in reaction gas and then in Ar at 30 ℃. The processing conditions are the same as those discussed with respect to fig. 31. There was no peak in the IR spectrum, indicating that MOF-808-P did not adsorb CO molecules under this condition.

FIG. 16 shows MOF-808-P, tBMP @ MOF-808-P and RuO₂CO Oxidation test of @ MOF-808-P. Both MOF-808-P and tBMP @ MOF-808-P were inactive to CO oxidation. The negative conversion observed for tBMP @ MOF-808-P is likely due to tBMP being removed from the MOFAnd (4) desorbing. Activating the catalyst at 120 ℃ for 1 hour by using Ar gas; the mass of the catalyst is as follows: 25.8mg, WHSV 120.93Lg_Ru ^-1h^-1。

FIG. 17 shows the use of O at 30 ℃₂Activated RuO₂/SiO₂And RuO₂Stability test with @ MOF-808-P (test conditions: 400L/g)_RuH, 15mg catalyst). The results are consistent with those at 100 ℃ in FIG. 32(d) discussed below. RuO₂The gradual deactivation of @ MOF-808-P at 30 ℃ is probably due to the formation of surface carbonates, as can be seen from the DRIFTS results discussed below^[43]。

Figure 18 shows the extended DRIFTS results of figure 31(d) discussed below. At 30 ℃, a peak characteristic indicative of carbonate formation can be seen.

FIG. 19 shows the synthesized RuO₂@ MOF-808-P with various treatments/tests (treatment with water vapor at 100 ℃; after 3 cycles of complete CO conversion; with O at 150 ℃)₂After activation) of RuO₂The PXRD pattern of @ MOF-808-P. From the similarity of the peak shape and the peak distribution, it can be seen that most of the structure is retained after treatment/testing. The PXRD experimental setup was the same as that mentioned in section 2.6 above.

FIG. 20 shows RuO₂Test for CO Oxidation of @ MOF-808-P, in which the standard O mentioned in section 4.2 above₂The test was carried out after activation (stage 1) and again after treatment with 10 v/v% steam at 100 ℃ for 60 minutes (stage 2). The mass of the catalyst is as follows: 30mg, WHSV 400L g_Ru ^-1·h^-1. After water treatment at high temperature, the catalytic activity is not reduced. The results show RuO₂The @ MOF-808-P catalyst has high water resistance.

TABLE 1 comparison of the performance of CO oxidation reactions with other guest @ MOF systems or Ru matrix systems.

FIG. 31 shows O₂Activated RuO₂/SiO₂(blue) and RuO₂CO and O in @ MOF-808-P (Red) and RuO₂Characteristics of the interaction of the guest. The experimental details of fig. 31 are given in section 4.1 above. Fig. 31(a) shows the CO Temperature Programmed Reduction (TPR) results, performed by pre-oxidizing the sample in equilibrium in a CO gas stream, followed by gradual heating to find the lowest temperature at which the surface lattice oxygen is in the active state. The results show that RuO₂The Ru-O binding interaction in @ MOF-808-P is significantly attenuated-the reaction peak ratio RuO₂/SiO₂(-240 ℃) is sharper and at lower temperatures (about 160 ℃). The results are further confirmed by in situ XANES spectroscopy, which shows RuO at 30 deg.C₂@ MOF-808-P to RuO₂/SiO₂It was more significantly reduced by 5% CO (FIG. 14), i.e., O was more easily replaced by CO.

FIG. 31(b-d) shows the change in DRIFTS peak intensity for (b) CO desorption, and (c) RuO₂/SiO₂And (d) with a reactive gas (1 v/v% CO, 20 v/v% O)₂And 79 v/v% O₂He) treated RuO₂The DRIFTS results for @ MOF-808-P. With RuO₂(110) The surface is an example to help us explain the DRIFTS results. These results indicate that the reaction with RuO₂/SiO₂MOF-limited RuO surface contrast₂The Ru-Co interaction at the surface is weaker. In RuO₂At 150 ℃ above @ MOF-808-P, the monodentate CO molecule desorbs (2055 cm)^-1The peak at (D)) disappeared and was negligible in FIG. 31(d)), while for RuO₂/SiO₂The 70% intensity of the corresponding peak remained unchanged (at 2076 cm)^-1Fig. 31 (c)). Because of their weaker interactions, both O and CO are more easily bound from RuO within the MOF₂And (5) removing the surface.

The DRIFTS feature also reveals the accumulation of adsorbed substances-in RuO₂/SiO₂Closely packed CO adsorption domains are observed, whereas in RuO₂Not observed in @ MOF-808-P (FIGS. 31(c), (d)), which enables general communicationActivity was obtained over Langmuir-Hinshelwood. The DRIFTS spectra were obtained as described in section 4.1 above. For RuO₂/SiO₂(FIG. 31c), we found three bands in the DRIFTS spectrum at 30 ℃ (2132, 2076 and 2027 cm)^-1). 2132cm can be added^-1And 2076cm^-1The band at (A) is assigned to a mono-coordinated CO molecule, of which 2132cm^-1The band at (A) is due to loosely coordinated CO and 2076cm^-1The main band of (A) is due to closely packed CO domains which are resistant to CO oxidation at low temperatures^[45]. At 2027cm^-1Due to adsorption on the RuO₂Bridging CO molecule with stronger bonding force on two adjacent oxygen vacancies^[45,46]. For RuO₂@ MOF-808-P (FIG. 31(d)), we did not observe close packing of CO. At 2055cm^-1The broadening peak at (A) is due to loosely adsorbed CO and at about 2005cm^-1The peak at (A) is due to bridging CO, similar to RuO₂/SiO₂The sample is 2027cm^-1At the shoulder, but less adjacent adsorbed O-neighborhood is likely. Control experiments with pure MOF showed no CO adsorption (no similar peak features in MOF-808-P spectra, fig. 15).

Table 2: RuO₂/SiO₂And RuO₂The DRIFTS absorption band of @ MOF-808-P and its indications.

By mixing RuO₂Confinement within the MOF cavity, (i) a decrease in the interaction between O/CO and the catalyst surface; (ii) the formation of tightly packed CO domains is inhibited. Therefore, the adsorbed CO is more easily oxidized. The temperature dependent DRIFTS results in the reaction gas (fig. 31(c), fig. 31(d)) further reflect this: at low temperature (about 100 ℃) in RuO₂Presence of O on @ MOF-808-P catalyst₂Can almost eliminate CO molecules even at about>CO molecules are still adsorbed to RuO at 150 DEG C₂/SiO₂The above. They are capable of modulating RuO contained in the MOF chamber₂On the surface of CO and O speciesAdsorption, which prompted us to compare by RuO respectively₂@ MOF-808-P and RuO₂/SiO₂Catalytic CO oxidation rate.

FIG. 32 shows the use of Ar or O₂Activated RuO₂/SiO₂And RuO₂CO Oxidation catalytic Performance Profile of @ MOF-808-P: (a) 15mg of catalyst was used at 2000L/g_RuCO conversion curve at Weight Hourly Space Velocity (WHSV) (from left to right: O)₂Activated RuO₂@ MOF-808-P, Ar activated RuO₂@MOF-808-P，O₂Activated RuO₂/SiO₂Ar activated Ru/SiO₂) (b) Arrhenius plot and calculated apparent activation energy (Ea) (right to left: o is₂Activated RuO₂@ MOF-808-P, Ar activated RuO₂@MOF-808-P，O₂Activated RuO₂/SiO₂Ar activated Ru/SiO₂) And (c) quantitative analysis of chemisorbed CO at-50 ℃ (to prevent CO formation during measurement)₂) And conversion frequency (TOF, conversion per unit time per unit site), (d) use of O at 100 ℃. (ii)₂Activated RuO₂/SiO₂And RuO₂@MOF-808-P(2000L/g_RuH, 15mg catalyst) were tested for stability. The experimental details of fig. 32 have been given in section 4.2 above.

Under all reaction conditions shown in FIG. 32, with RuO₂/SiO₂Catalyst comparison, RuO prepared according to the invention₂The @ MOF-808-P catalyst exhibited excellent performance (5% vs. no conversion at 30 ℃ C.; 100% vs. conversion at about 65 ℃ C.; 100% conversion only at about 150 ℃ C.). From these results, we calculated the apparent activation energies of the two samples, E_a86kJ/mol and E_a145kJ/mol, and limited catalyst activation energy at measured RuO₂Low end of activation energy^[43]. Theoretically, RuO₂@ MOF-808-P has a higher switching frequency (TOF) (FIG. 32(c)) due to the presence of only loosely packed CO molecules (Table 1)^[57]. It should also be noted that the catalyst is at O compared to after Ar activation₂After activation, better CO → CO is realized₂Conversion (FIG. 32(a)), indicating RuO₂Is an active surface structure (figure 13) and an oxygen-enriched surface, is more beneficial to the chemical adsorption of CO (figure 32(c))^[58]。RuO₂Higher CO chemisorption obtained in @ MOF-808-P with smaller RuO formation within MOF₂The nanoentities (i.e. higher surface to volume ratio) are consistent, which is supported by the TEM results shown in fig. 11 and 12. As a control, we demonstrated that MOF-808-P and tBMP @ MOF-808-P were inactive to CO oxidation, as shown in FIG. 16, described above.

The above results indicate that RuO₂@ MOF-808-P is a unique low temperature CO oxidation catalyst. At only 100 ℃ and 2000L/g_RuH CO flow, after 12 hours it still has>95% conversion capacity, while under the same conditions, RuO₂/SiO₂Complete inactivation occurred within 20 min (FIG. 32 (d)). This is consistent with our CO-TPR and DRIFTS results. We propose, for RuO₂/SiO₂The catalyst, when exposed to a continuous feed of reactant gas at low temperature, forms tightly packed surface CO and O domains, preventing CO-O binding (fig. 31(c)) leading to rapid deactivation at 100 ℃ (fig. 32 (d)). By mixing RuO₂Confined in the cavities of the MOF (i.e., RuO)₂@ MOF-808-P), we reacted adsorbed CO with adsorbed O and easily desorbed at low temperature due to the reduced interaction of CO and O (fig. 31 (d)). Furthermore, near room temperature (30 ℃), we have also observed a completely different CO → CO₂Conversion performance (FIGS. 17 and 18), wherein RuO₂/SiO₂The catalyst was completely deactivated after 12 minutes, while the constrained catalyst still had after 2 hours>40% conversion and easy regeneration. This is advantageous for room temperature based CO removal, as potential interaction with water may be important. RuO activated by treatment even with water vapor at 100 deg.C₂@ MOF-808-P, we demonstrated that (i) the MOF structure is largely retained (FIG. 19), and (ii) RuO₂@ MOF-808-P retained its high activity (FIG. 20), a challenge for recent MOF-based catalyst development^[11]。

5 some preliminary results for other guest @ nanoporous host materials obtained using our strategy

FIGS. 21 and 22 show preliminary XRD and SEM-EDX results for manganese oxide (MnOx) in another Zr-based MOF, DUT-67MOF (i.e., MnOx @ DUT-67)^[59]. The method for preparing this material is as described above for the preparation of RuO₂@ MOF-808-P, with the exception of RuO₄ ^-By MnO₄ ^-Instead, MOF-808-P is replaced by DUT-67. The precursor solution was 20mM KMnO₄An aqueous solution.

In addition to using tBMP as a redox reagent to produce MnOx @ DUT-67, the inventors also obtained MnOx @ DUT-67 using EDOT (3, 4-ethylenedioxythiophene) as a reducing agent. In both cases, DE was used to dissolve tBMP or EDOT (50 mg of EDOT or tBMP in 1000. mu. lDE). The temperature of the temperature-controlled selective desorption step was 120 ℃.

FIGS. 23 and 24 show RuO in zeolite Y from Alfa Aesar₂Some preliminary XRD and SEM-EDX results. The method for preparing this material is as above for the preparation of RuO₂@ MOF-808-P, except that MOF-808-P is replaced by a Y-type zeolite.

FIGS. 25 and 26 show some preliminary XRD and SEM-EDX results for manganese oxide (MnOx) (i.e., MnOx @ MOF-808-P) in another Zr-based MOF, i.e., MOF-808-P. The method for preparing this material is as described above in relation to RuO₂@ MOF-808-P, with the exception of RuO₄ ^-By MnO₄ ^-Instead (the precursor solution was 20mM KMnO₄An aqueous solution).

All of the above materials were prepared using the methods mentioned in this work to demonstrate the general applicability of the guest incorporation concept to a range of nanoporous materials. Reference may be made to section 2.6 above for a related characterization method.

As a further demonstration, the Material Project software was used^60-62(https:// material project. org /) a Pourbaix diagram was constructed and used to predict the potential conditions required to prepare the guest @ nanoporous host material of Pt and Pd in MOF (Pt/Pd @ MOF). FIG. 27 shows Pourbaix plots of Pt ([ Pt ]]＝10^-2mol kg^-1(total aqueous mixture)), fig. 28 shows a Pourbaix map of Pd ([ Pd)]＝10^-2mol kg^-1(total aqueous mixture)). Both Pourbaix maps use Material Project software^60-62And (5) constructing.

In short, since no stable Pt was observed on the Pourbaix plot of Pt in FIG. 27²⁺Therefore, it is difficult to incorporate Pt²⁺For bulk (e.g. MOF) impregnation. The inventors believe that additional stabilization with ligands is required in the Pt precursor. For example, it may be necessary to use a Pt precursor (e.g., [ Pt (NH) ]₃)₄]Cl₂Instead of PtCl₂) Preparation of Pt @ MOF by solution synthesis, where additional NH is required₃To stabilize the Pt (II) salt⁹。

In contrast, Pd is according to the poirbaix plot of Pd shown in fig. 28²⁺Precursors that are easier to use as flow precursors to impregnate MOFs, especially at low pH conditions (even at fairly high Pd²⁺Concentration 10^-2mol·kg^-110mM, stable Pd at low pH²⁺Phase). As experimental verification, 0.106g Pd (NO) is added₃)₂·H₂O is stabilized at 20ml HNO₃(solution, 0.1M). Pd if the pH is not changed²⁺Can be easily reduced to Pd⁰Nevertheless, if the pH rises significantly, the Δ E_{Reduction of}And may exceed 0.5V. Since the pH after the reaction is likely to be higher than that of acidic Pd²⁺Solutions (i.e., precursor solutions), thus using NaBH₄Pd can be used as a reducing agent (standard reduction potential of-1.24V relative to SHE)²⁺Fully reduced to Pd⁰Regardless of pH changes. To prepare NaBH₄(aq) solution, 0.15g NaBH₄(excess) was dissolved in 280ml of Milli-Q water at pH of about 8. Since the redox reaction will be at a pH slightly less than 8 (due to NaBH)₄Excess) occurs under aqueous conditions, and thus MOF-808-P is selected as the host.

To load Pd into the MOF-808-P (i.e., to form Pd @ MOF-808-P), Pd (NO) is loaded₃)₂The solution was impregnated in dry MOF-808-P. Then Pd (NO)₃)₂(aq) @ MOF-808-P and prepared NaBH₄The solution was reacted at room temperature for 10 minutes. A black suspension was observed after the reaction,shows that metallic Pd is formed⁰. The product was collected by centrifugation, washed with water and ethanol. It was then dried in a vacuum oven for 24 hours at room temperature.

FIG. 29 shows DR-STEM images of Pd @ MOF-808-P and its corresponding STEM-EDS spectra for Zr and Pd. As shown in fig. 29, since the load control step is not performed, the metal Pd is⁰Both within the MOF and on its outer surface. Some Pd particles will accumulate on the outer surface of the MOF (without MOF pore limitation). FIG. 30 shows a PXRD pattern for MOF-808-P and Pd-loaded MOF-808-P (i.e., Pd @ MOF-808-P). Using CuK α on a Rigaku D/Max 2500 diffractometer Radiation source and at 1 deg.min^-1The scanning rate of (c) collects PXRD results. For Pd @ MOF-808-P, the presence of large Pd particles (Pd) can be confirmed by the peak at about 40 ℃ in the PXRD pattern⁰) As shown in fig. 30. Meanwhile, the PXRD pattern also verifies that the MOF structure is reserved in the whole synthesis process. Thus, Pd @ MOF-808-P can also be prepared according to the methods of the present invention.

₂6 Pourbaix diagram for constructing Ru-HO system

Ru-H₂The Pourbaix diagram for the O system is shown in fig. 33. For simplicity, FIG. 33 shows only Ru-H₂The O Pourbaix plot shows a portion of the pH between 5 and 10. The formation of several other Ru-containing compounds than metallic Ru is thermodynamically favored in this pH range, namely: h₂RuO₅(solution), RuO₄ ^-(solution) Ru₂O₅(insoluble solid), RuO₂·2H₂O (insoluble solids) and Ru (OH)₃·H₂O (insoluble solids). Here, we assume that the concentration of the insoluble Ru-containing compound in the aqueous solution is 0M.

According to Povar&Spinu^[32]As a result of the detailed description, we can construct Ru-H₂Pourbaix diagram for O system (pH 5-10, C)_Ru ⁰20 mM). Our pH range may involve 6 different half-cell reduction reactions (standard electrode potentials, E)⁰)：

Ru(OH)₃·H₂O+3H⁺+3e^-＝Ru+4H₂O,E₁ ⁰0.631V type (S1)

RuO₂·2H₂O+H⁺+e^-＝Ru(OH)₃·H₂O,E₂ ⁰0.777V type (S2)

Ru₂O₅+3H₂O+2H⁺+2e^-＝2RuO₂·2H₂O,E₃ ⁰As 1.168V (S3)

2RuO₄ ^-+6H⁺+4e^-＝Ru₂O₅+3H₂O,E₄ ⁰1.701V type (S4)

2H₂RuO₅+6H⁺+6e^-＝Ru₂O₅+5H₂O,E₅ ⁰As 1.466V (S5)

H₂RuO₅+e^-＝RuO₄ ^-+H₂O,E₆ ⁰0.996V type (S6)

According to the nernst equation of the electrochemical half-cell reduction reaction, the potential E can be effectively written as:

wherein R is a gas constant (about 8.314J. K)^-1·mol^-1) T is temperature, in K, z is the number of electrons transferred in the half-cell reaction, and F is the Faraday constant (about 96485℃ mol.)^-1)。

In addition to this, the present invention is,

ln[H⁺]≈2.303log[H⁺]2.303pH (S8)

Thus, for feedingC of fixed_Ru ⁰(in our case, C_Ru ⁰20mM), the relationship between E and pH can be established S1-S6.

E₆＝E₆ ⁰Formula (S14)

The Ru-H was then constructed using the above E vs pH relationship₂O system (pH 5-10, C)_Ru ⁰20mM) simplified Pourbaix diagram. Meanwhile, there are triple points of disproportionation:

6RuO₄ ^-+H₂O+6H⁺＝Ru₂O₅+4H₂RuO₅formula (S15)

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments outlined above, many equivalent modifications and variations will be apparent to those skilled in the art in light of the teachings herein. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanation provided herein is intended to aid the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the words "comprise" and "contain" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" with respect to a numerical value is optional and refers to, for example, +/-10%.

Reference to the literature

Numerous publications are cited above to more fully describe and disclose the present invention and the state of the art. The following provides a complete citation of these references. Each of the following references is incorporated herein in its entirety.

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