阅读说明：本技术 用于氢储存的具有混合配体的基于锌的金属有机骨架(zit) (Zinc-based metal organic frameworks with mixed ligands for hydrogen storage (ZIT) ) 是由 塔潘·贝拉 阿马尔迪普·辛格 卡拉达尔·塞瓦尔 克里斯托弗·贾亚拉杰 乌米什·斯里瓦斯塔瓦 于 2021-06-24 设计创作，主要内容包括：本发明涉及通过简单且经济的溶剂热法合成新的具有1,3,5-苯三羧酸(BTC)和2-甲基咪唑(mIm)的混合有机配体的基于Zn(II)的金属有机骨架。合成的MOF具有长方体形态,具有高表面积(1248m～(2)/g),能够在-10℃至25℃温度和100巴压力下吸附氢。新的MOF的氢吸附能力在23重量百分比至0.2重量百分比的范围内。(The present invention relates to a novel zn (ii) -based metal-organic framework with mixed organic ligands of 1,3, 5-benzenetricarboxylic acid (BTC) and 2-methylimidazole (mIm) synthesized by a simple and economical solvothermal method. The synthesized MOF has a rectangular parallelepiped morphology with a high surface area (1248 m) 2 Per g) capable of adsorbing hydrogen at a temperature of-10 ℃ to 25 ℃ and a pressure of 100 bar. The hydrogen sorption capacity of the new MOFs ranged from 23 to 0.2 weight percent.)

1. A zinc-based metal-organic framework having mixed ligands, wherein the mixed ligands comprise a combination of 1,3, 5-benzenetricarboxylic acid (BTC) and 2-methylimidazole (mIm).

2. The zinc-based metal-organic framework of claim 1, wherein the zinc-based metal-organic framework has a rectangular parallelepiped morphology.

3. The zinc-based metal-organic framework of claim 1, wherein zinc ion is tetracoordinated to one 2-methylimidazolium ion and three 1,3, 5-benzenetricarboxylic acid ions.

4. The zinc-based metal-organic framework of claim 1, wherein the zinc-based metal-organic framework adsorbs hydrogen at-10 ℃ to 25 ℃.

5. The zinc-based metal-organic framework of claim 4, wherein the zinc-based metal-organic framework adsorbs hydrogen at-10 ℃ to 10 ℃.

6. The zinc-based metal organic framework of claim 1, wherein the zinc-based metal organic framework has a high thermal stability in the range of 430 ℃ to 470 ℃.

7. The zinc-based metal-organic framework of claim 1, wherein the zinc-based metal-organic framework has 1248m²Large surface area in g.

8. A method for synthesizing a zinc-based metal-organic framework, wherein the method comprises the steps of:

preparing a zinc metal precursor solution by adding at least one zinc metal precursor in an organic solvent;

preparing an organic ligand solution by adding at least one organic ligand in the organic solvent;

mixing the zinc metal precursor solution, the organic ligand solution, and the organic solvent to obtain a reaction mixture;

heating the reaction mixture at 100 ℃ to 140 ℃ for 12 hours to 48 hours to obtain a precipitate of the zinc-based metal-organic framework;

filtering, washing the precipitate of the zinc-based metal organic framework;

purifying the precipitate of zinc-based metal organic framework; and

the purified precipitate was dried in an oven at 100 ℃ for 12 to 15 hours.

9. The method of claim 8, wherein the at least one zinc metal precursor is selected from one of zinc acetate dihydrate, zinc nitrate hexahydrate, or a combination thereof.

10. The method of claim 8, wherein the at least one organic ligand is selected from one of 1,3, 5-benzenetricarboxylic acid, 2-methylimidazole, or a combination thereof.

11. The method of claim 8, wherein the organic solvent is a combination of Dimethylformamide (DMF) and ethanol.

12. The method of claim 8, wherein the washing of the precipitate comprises washing with an organic detergent, washing with distilled water, or a combination.

13. The process according to claim 12, wherein the organic detergent is selected from Dimethylformamide (DMF), Dichloromethane (DCM), ethanol, or mixtures thereof.

Technical Field

The present invention relates to zinc-based Metal Organic Frameworks (MOFs) and their synthesis. In particular, the present invention relates to a novel zn (ii) based metal organic framework (ZIT) based on mixed organic ligands of 1,3, 5-benzenetricarboxylic acid (BTC) and 2-methylimidazole (mIm). Wherein the Zn (II) -based metal organic framework (ZIT) is synthesized by a simple and economical solvothermal method.

Background

Metal Organic Frameworks (MOFs) are an emerging class of hybrid materials with organic flexible scaffolds and topologies of traditional materials such as zeolites, active carbonates. The Metal Organic Framework (MOF) is mainly composed of metal ions and organic ligands, forming a one-dimensional, two-dimensional or three-dimensional structure. The diverse shape and morphology of Metal Organic Frameworks (MOFs) have a significant impact on their performance and use in many technical fields, such as storage, catalysis, etc.

Various types of MOFs have been reported in the literature, such MOFs having different morphologies depending on their synthesis conditions. In addition, the choice of metal and organic ligand linkers plays an important role in determining the properties of the MOF material.

Recently, many potential industrial applications of MOFs have been identified, thus leading to the commercial synthesis of such MOF materials. Therefore, there is a need to develop efficient methodologies, since the synthesis of MOFs is a demanding research area, which mainly involves thermal, solvothermal or hydrothermal routes. However, due to the high efficiency in single crystal formation, solvothermal synthesis of MOFs remains an option. Furthermore, the scale-up of MOF preparation has another commercial importance, and the development of efficient and environmentally friendly synthetic methods is a clear advantage.

Furthermore, during the last two decades, a wide range of MOFs and their applications have been identified, among others, in the technical field of hydrogen storage.However, to date, none of the identified MOFs have achieved the united states department of energy (US DOE) with respect to H₂The target of absorption. Furthermore, as seen in a number of literature and review articles, most MOFs are employed for absorbing H at liquid nitrogen temperatures and high pressures₂。

US2009/0185972a1 discloses a hydrogen storage system for storing hydrogen at elevated pressures and cryogenic temperatures.

WO2010058123 discloses a process for the hydrothermal preparation of crystalline porous aluminium carboxylates with metal-organic frameworks. EP1070538 discloses metal-organic polymers for gas separation and purification. Furthermore, a scale-up method for the preparation of MOFs is disclosed in US 20090042000.

In order to develop better adsorbents for gas adsorption, several strategies have been employed in the synthesis of mixed ligand-based MOFs. In addition, U.S. patent No. 8916722 describes complex mixed ligand open framework materials. Us patent No. 0171107 relates to a process for preparing a porous metal-organic framework comprising two organic compounds coordinated to at least one metal ion, wherein one organic compound is an optionally substituted mono-, bi-or polycyclic saturated or unsaturated hydrocarbon and the other organic compound is derived from a dicarboxylic, tricarboxylic or tetracarboxylic acid.

US2006/0252641a1 discloses hydrogen storage materials comprising a MOF comprising a plurality of charged multidentate linking ligands and a plurality of metal clusters having at least one open metal site for storing molecular hydrogen.

However, despite considerable improvements in the state of the art of MOFs using solvothermal and hydrothermal methods, few reports have been made on mixed ligand-based MOFs and methods for their synthesis for large-scale industrial production.

Furthermore, the overall cost is also important for large-scale industrial production of such mixed ligand-based MOF materials.

Furthermore, to date, there has been no report of mixed ligand-based MOF materials for efficient storage of H at-10 ℃ to 25 ℃₂The ability of the cell to perform.

In addition, it is thermally stableIt is also such mixed ligand-based MOF materials for efficient storage of H₂And not doing so in so great deal of work on such highly thermally stable mixed ligand-based MOF materials.

The purpose of the invention is as follows:

it is an object of the present invention to provide Metal Organic Frameworks (MOFs) for efficient storage of hydrogen at-10 ℃ to 25 ℃.

The main object of the present invention is to provide a novel zinc-based metal organic framework (Zn-MOF) with mixed ligands, wherein said Zn-MOF has a cuboid morphology, a large surface area and a high thermal stability.

The main object of the present invention is the synthesis of novel zinc-based metal organic frameworks (Zn-MOFs) with mixed ligands by solvothermal methods.

It is another object of the invention to synthesize a zinc-based metal organic framework (Zn-MOF) with mixed ligands, wherein the Zn-MOF is capable of storing H maximally at-10 ℃ to 10 ℃₂。

It is another object of the present invention to synthesize zinc-based metal organic frameworks (Zn-MOFs) with mixed ligands, especially a combination of two different kinds of mixed ligands.

Disclosure of Invention

The prior art shows for efficient H₂Synthesis of MOFs based on a single ligand system for storage purposes. However, the combination of two different kinds of mixed ligands, such as trimesic acid (BTC) and 2-methylimidazole (mIm), to make new MOFs has not been disclosed.

Accordingly, the present invention relates to zinc-based metal organic frameworks (Zn-MOFs) having mixed ligands comprising a combination of 1,3, 5-benzenetricarboxylic acid (BTC) and 2-methylimidazole (mIm).

Furthermore, the present invention relates to the synthesis of novel mixed ligand Zn-MOFs having a cuboid morphology capable of adsorbing hydrogen at-10 ℃ to 25 ℃. The novel mixed ligand Zn-MOF of the invention comprises zinc ions which are tetracoordinated to one 2-methylimidazole ion and three 1,3, 5-benzenetricarboxylic acid ions.

Furthermore, the invention relates to compositions having high thermal stability (4)30 ℃ to 470 ℃) and a large surface area (1248m²Synthesis of novel mixed ligands Zn-MOF of/g).

The novel mixed ligand Zn-MOFs of the present invention are synthesized by solvothermal methods. In the solvothermal method, a metal precursor and an organic ligand are heated in an organic solvent for Metal Organic Framework (MOF) crystal generation. First, a zinc metal precursor solution and an organic ligand solution are prepared by adding at least one zinc metal precursor and at least one organic ligand in an organic solvent. The zinc metal precursor solution, organic ligand solution and organic solvent are then mixed to obtain a reaction mixture. The reaction mixture is then heated at 100 ℃ to 140 ℃ for 12 hours to 48 hours to obtain a precipitate of a zinc-based Metal Organic Framework (MOF). The precipitate of zinc-based Metal Organic Framework (MOF) is then filtered and washed. Purifying the precipitate of zinc-based Metal Organic Framework (MOF), and then drying the purified precipitate in an oven at 100 ℃ for 12 to 15 hours.

The novel mixed ligand Zn-MOF of the invention adsorbs hydrogen at-10 ℃ to 25 ℃ and enables maximum storage of H at-10 ℃ to 10 ℃₂。

Drawings

To further clarify the advantages and aspects of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that the drawings in accordance with the present invention depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope.

FIG. 1: single X-ray structures of Zn-MOFs are depicted;

FIG. 2: a stacking diagram of Zn-MOFs is depicted, revealing pore sizes between cavities;

FIG. 3: a stacking diagram of Zn-MOF is depicted;

FIG. 4: SEM images of Zn-MOF are depicted;

FIG. 5: the XRD pattern of Zn-MOF is depicted;

FIG. 6: the TGA curve of Zn-MOF is depicted;

fig. 7 (a): h2 adsorption/desorption isotherms of Zn-MOF at 0 ℃ are depicted; and

fig. 7 (b): the H2 adsorption/desorption isotherm of Zn-MOF at Room Temperature (RT) is depicted.

Detailed Description

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to specific embodiments of the invention that are further illustrated in the drawings and specific language will be used to describe the same. The foregoing general description and the following detailed description are explanatory of the disclosure, and are not intended to be restrictive. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated construction, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The methods and examples provided herein are illustrative only and are not intended to be limiting.

Zinc-based metal organic frameworks (Zn-MOFs) having mixed ligands selected from the group consisting of 1,3, 5-benzenetricarboxylic acid (BTC) and 2-methylimidazole (mIm) combinations are disclosed. The zinc-based metal organic framework (Zn-MOF) has a rectangular parallelepiped morphology.

Furthermore, the Zn-MOFs of the present invention are three-dimensional structures comprising as Secondary Building Units (SBU) tetrahedral Zn (ii) which in turn is built up from mixed ligands, i.e. 2-methylimidazole and 1,3, 5-benzenetri-carboxylate ions.

As shown in fig. 1, the Zn ion unit is coordinated by one 2-methylimidazole and three monodentate chelating 1,3, 5-benzenetri-carboxylate ions.

The zinc (Zn) ion being tetra-coordinated, wherein ZnO₃The cells have a distorted tetrahedral geometry. The zinc (Zn) ion as a secondary building block (SBU) is bridged by a fully deprotonated 1,3, 5-benzenetricarboxylate anion and 2-methylimidazole to produce a three-dimensional hierarchical arrangement.

Furthermore, in solid state form, the zinc-based metal organic framework (Zn-MOF) forms square cells along the "ab" planeWherein the cells have an average size of(FIG. 2). Wherein each cell is predominantly available to the host molecule. Furthermore, the theoretical porosity of the evacuated Zn-MOF, calculated from PLATON, is 15.8% and the radius of the probe is(FIG. 3).

In addition, the zinc-based metal organic frameworks of the present invention adsorb hydrogen at-10 ℃ to 25 ℃. In particular, the zinc-based metal organic frameworks of the present invention adsorb hydrogen at-10 ℃ to 10 ℃. The hydrogen adsorption capacity of the novel zinc-based metal organic framework of the present invention ranges from 23 weight percent to 0.2 weight percent.

Table 1 as provided herein below shows a comparative study of hydrogen adsorption between literature reported MOFs and zinc-based metal organic frameworks (Zn-MOFs) as prepared and disclosed in the present invention. With a literature report of 7.1 to 7.5 wt% H at-196 deg.C₂The zinc-based metal organic framework (Zn-MOF) of the invention exhibits H at 0 ℃ in comparison to absorbed MOFs, which are difficult to maintain and therefore involve higher operating costs₂The absorption was 23% by weight (easy to maintain and therefore economical, handling advantages).

TABLE-1

In addition, the zinc-based metal organic framework of the present invention has high thermal stability in the range of 430 ℃ to 470 ℃.

Furthermore, the zinc-based metal-organic framework of the invention has 1248m²Large surface area in g.

In addition, various methods have been developed for synthesizing MOFs using metal precursors and corresponding organic ligands. Improved solvothermal methods using these precursors have been used to form MOF crystals. Solvothermal synthesis is a method of heating metal precursors and organic ligands in an organic solvent for MOF crystal formation. In modified solvothermal synthesis, the solution with MOF precursors is typically held at a predetermined equilibrium temperature for an extended period of time to induce crystallization.

Furthermore, solvothermal processes are generally slow, but provide a uniform and reproducible material. Furthermore, many publications on the Synthesis method by solvothermal methods are reported in the literature, such as "" scientific Synthesis and Design of New materials "," Yaghi et al, Nature 423(2003)705- "Solvo-thermal Synthesis, structure, and properties of metal organic precursors from a partially fluorinated link", "Patchful et al, 2011 family and template-free solution-thermal Synthesis of meso/macroporous metal-organic frameworks" Zhang et al, RSC adv.,2018,8,33059, 33064.

Thus, the novel mixed ligand Zn-MOFs of the present invention are synthesized by a simple and economical solvothermal method. In the solvothermal method, a zinc (Zn) metal precursor and an organic ligand are heated in an organic solvent for Metal Organic Framework (MOF) crystal formation.

In accordance with a principal embodiment, the present invention provides a method for synthesizing a novel mixed ligand Zn-MOF having a cuboid morphology, a large surface area, and high thermal stability.

First, a zinc metal precursor solution and an organic ligand solution are prepared by adding at least one zinc metal precursor and at least one organic ligand in an organic solvent. The zinc metal precursor solution, organic ligand solution and organic solvent are then mixed to obtain a reaction mixture. The reaction mixture is then heated at 100 ℃ to 140 ℃ for 12 hours to 48 hours to obtain a precipitate of a zinc-based Metal Organic Framework (MOF). The precipitate of zinc-based Metal Organic Framework (MOF) is then filtered and washed. Purifying the precipitate of zinc-based Metal Organic Framework (MOF), and then drying the purified precipitate in an oven at 100 ℃ for 12 to 15 hours.

The at least one zinc (Zn) metal precursor is selected from one of zinc acetate dihydrate, zinc nitrate hexahydrate, or a combination thereof. The at least one organic ligand is selected from one of benzene-1, 3, 5-tricarboxylic acid, N-methylimidazole, or a combination thereof. The organic solvent is a combination of Dimethylformamide (DMF) and ethanol.

The washing of the precipitate includes washing with an organic detergent, washing with distilled water, or a combination. Wherein the organic detergent is selected from Dimethylformamide (DMF), Dichloromethane (DCM), ethanol or a mixture thereof.

Further, in the present invention, a solvent mixture of Dimethylformamide (DMF) and ethanol is used instead of conventional Dimethylformamide (DMF), which greatly simplifies the post-treatment process with high recovery rate. When the solvent mixture is Dimethylformamide (DMF) and ethanol, the product yield is 50% to 70%. However, when Dimethylformamide (DMF) was used only as a solvent, the product yield was 40% to 50%.

Furthermore, a Scanning Electron Microscope (SEM) image of Zn-MOF as synthesized by the solvothermal method of the present invention is presented in fig. 4. Wherein, Scanning Electron Microscope (SEM) images of Zn-MOF showed that the particles were cubic in the range of 0.6 to 1.2 μm (fig. 4). Furthermore, some cubes have missing corners, instead appearing as perfect cubes, on which the micro rod array covers the entire face. Furthermore, FIG. 5 shows an X-ray diffraction pattern of Zn-MOF as disclosed and prepared in the present invention. Furthermore, fig. 6 shows a thermogravimetric analysis (TGA) curve of Zn-MOFs as disclosed and prepared in the present invention. Furthermore, fig. 7(a) shows the H2 adsorption/desorption isotherm of Zn-MOF at 0 ℃, and fig. 7(B) shows the H2 adsorption/desorption isotherm of Zn-MOF at Room Temperature (RT), however, Zn-MOF-a (2 nd cycle), Zn-MOF-B (3 rd cycle), and Zn-MOF-C (4 th cycle).

Solvothermal synthesis of Zn-MOF production

Example-1:

the zinc (Zn) metal precursor solution is prepared by dissolving 2 to 5 grams of zinc acetate dihydrate in 10 to 30mL of Dimethylformamide (DMF). Similarly, an organic ligand solution was prepared by dissolving 2 to 5 grams of benzene-1, 3, 5-tricarboxylic acid (BTC) and 0.2 to 1 gram of 2-methylimidazole (mIm) in 10 to 30mL of Dimethylformamide (DMF). Thereafter, willThe obtained zinc (Zn) metal precursor solution and the organic ligand solution are sonicated for 10 to 30 minutes. Thereafter, the zinc (Zn) metal precursor solution was transferred to a round-bottom flask, and then an organic ligand solution of benzene-1, 3, 5-tricarboxylic acid (BTC) and 2-methylimidazole (mIm) was added dropwise thereto to obtain a reaction mixture. Further, 30mL to 50mL of Dimethylformamide (DMF) was added to the reaction mixture. The resulting reaction mixture is then heated at 100 ℃ to 140 ℃ for 12 hours to 48 hours. The reaction precipitate obtained was filtered and washed with Dimethylformamide (DMF) and then with ethanol/H₂And washing the O mixture. In addition, the reaction precipitate was kept solvent-exchanged by adding Dichloromethane (DCM) at intervals of 12 to 36 hours and then performing solvent decantation. This process was continued 3 times over a week to remove excess Dimethylformamide (DMF) solvent. Finally, the reaction precipitate was dried in an oven at 100 ℃ overnight.

The invention has the technical advantages that:

the present invention provides a number of advantages over the prior art. Zn-MOF as prepared in the present invention requires low cost materials, thus making feasible large-scale industrial production of Zn-MOF. Furthermore, Zn-MOFs as prepared in the present invention are highly thermally stable, i.e. in the range of 430 ℃ to 470 ℃. Furthermore, Zn-MOFs as prepared in the present invention are directed to H at-10 ℃ to 10 ℃ when compared to other prior art MOFs that show storage at cryogenic temperatures₂The absorption capacity is more efficient. Since the temperature range-10 ℃ to 10 ℃ is close to room temperature, the temperature range can be maintained when compared to the low temperature.