阅读说明：本技术 一种镍基金属有机骨架Ni-MOF材料及其制备方法和应用 (Nickel-based metal organic framework Ni-MOF material and preparation method and application thereof ) 是由 李舒晴 叶卓幸 郑盛润 章伟光 范军 蔡松亮 黄洁芬 刘淑娜 张新杰 于 2021-08-24 设计创作，主要内容包括：本发明公开一种镍基金属有机骨架Ni-MOF材料及其制备方法和应用。本发明的Ni-MOF材料具有螺旋形的一维孔道,不需要活化即可用于碘分子的吸附；对有机溶剂、水和碘蒸汽中的碘分子均具有较高的吸附容量；吸附碘分子后,材料同时发生无定形化,从而起到更稳定更牢固地捕获碘分子的作用。本发明的Ni-MOF材料制备简单,耗时短,产量和纯度较高。(The invention discloses a nickel-based metal organic framework Ni-MOF material and a preparation method and application thereof. The Ni-MOF material has spiral one-dimensional pore channels, and can be used for adsorption of iodine molecules without activation; the adsorption capacity to iodine molecules in organic solvent, water and iodine vapor is high; after the iodine molecules are adsorbed, the material is amorphized simultaneously, so that the effect of more stably and more firmly capturing the iodine molecules is achieved. The Ni-MOF material is simple to prepare, short in time consumption and high in yield and purity.)

1. A Ni-MOF material with a nickel-based metal organic framework is characterized in that the chemical general formula of the Ni-MOF material is [ Ni ]₂(C₂₅H₁₈N₉)₃X]_nX is a monovalent anion; said C is₂₅H₁₈N₉The ligand structure is shown as formula (I):

in each asymmetric unit of the main framework of the crystal structure of the Ni-MOF material, each ligand is connected with 4 Ni through four nitrogen atoms²⁺Coordination forms a coordination mode as shown in formula (II), two Ni²⁺Respectively coordinated with three imidazole nitrogen atoms from different ligands and three tetrazole nitrogen atoms from different ligands, and bridged with three tetrazole groups to form a dinuclear structural unit shown in formula (III), wherein the dinuclear structural unit is arranged at C₂₅H₁₈N₉Forming a three-dimensional porous framework under the connection action of the ligand;

2. the nickel-based metal organic framework Ni-MOF material of claim 1, wherein X is chloride or nitrate.

3. The nickel-based metal organic framework Ni-MOF material according to claim 1, wherein the crystals of the Ni-MOF material belong to the hexagonal system with unit cell parameters: α＝90°，β＝90°，γ＝120°。

4. a preparation method of the nickel-based metal organic framework Ni-MOF material as claimed in any one of claims 1 to 3, characterized by comprising the following steps:

s1, mixing a ligand bis- (4-imidazolyl-1-phenyl) - [4- (5-tetrazolyl) phenyl ] amine and monovalent nickel salt at normal temperature to obtain a mixture;

s2, adding N, N '-dimethylacetamide or N, N' -dimethylformamide into the mixture to obtain a suspension, and ultrasonically dispersing the suspension;

s3, heating the suspension liquid treated in the step S2 at the constant temperature of 140-160 ℃ for reaction;

and S4, after the reaction is finished, cooling and filtering to obtain the Ni-MOF material.

5. The production method according to claim 4, wherein in step S1, the molar ratio of the bis- (4-imidazolyl-1-phenyl) - [4- (5-tetrazolyl) phenyl ] amine to the monovalent nickel salt is (1:1) to (1: 1.5).

6. The method according to claim 4 or 5, wherein in step S1, the monovalent nickel salt is nickel chloride or nickel nitrate.

7. The preparation method according to claim 4, wherein in the step S2, the ultrasonic dispersion time is 15-45 min.

8. The preparation method according to claim 4, wherein in step S3, the reaction time of the heating reaction is 2 to 4 days.

9. Use of the Ni-MOF material of any one of claims 1 to 3 as an adsorbent for iodine molecules.

10. The use of claim 9, wherein the iodine molecules are iodine molecules in an organic solvent, water or solvent vapor.

Technical Field

The invention belongs to the technical field of adsorption materials. More particularly, relates to a nickel-based metal organic framework Ni-MOF material, and a preparation method and application thereof.

Background

Nuclear power is one of the effective solutions to energy demand, has the advantages of cleanliness, low consumption, high efficiency, small floor space, etc., but generates a large amount of radioactive pollutants. Radioactive iodine is one of the major radioactive contaminants in nuclear industrial wastewater, for example,¹²⁹i has a longer half-life (150 ten thousand years) and a higher yield of cracks,¹³¹i have a high activity, and they all can influence the metabolic processes in humans by bioaccumulation of the food chain. When humans are exposed to high doses of radioactive iodine, the risk of thyroid disease and even cancer is increased. Therefore, removing iodine from pollutants to improve environmental safety and guarantee life health becomes a research hotspot at present. The method for adsorbing and capturing iodine by utilizing the porous material is a promising method, but the traditional porous materials such as activated carbon, zeolite and the like have low adsorption capacity and few active adsorption sites, so that a new porous adsorption material needs to be explored and developed for adsorbing iodine.

The metal-organic framework is a porous adsorption material which is researched more at present, and is formed by assembling metal ions and organic ligands in a coordination mode, and the structure and the property of the porous material can be regulated and controlled through reasonable selection of the metal ions and the organic ligands, so that the porous material suitable for certain performance is obtained. The MOF material is one of metal-organic framework porous materials, has high specific surface area and functional sites of organic ligands, and shows more excellent adsorption performance than the traditional porous materials. At present, most of the constructed MOF materials show good reversible adsorption performance on iodine molecules, which is beneficial to the repeated use of the materials, but the MOF materials have low adsorption quantity and insufficiently firm adsorption, and are not beneficial to being used as solid adsorbents for the long-term sealing storage of the iodine molecules.

For example, cn201710148875.x discloses a zinc-MOF microporous material for efficiently capturing iodine, and a preparation method and application thereof, the material has a certain adsorption capacity on iodine, but the material still does not solve the problem that the adsorption is not firm enough and is not favorable for being used as a solid adsorbent for long-term storage of iodine molecules, the microporous material can adsorb iodine only by activation, and the synthesis process of the material is time-consuming.

Disclosure of Invention

The invention aims to solve the technical problems of poor iodine adsorption effect and weak adsorption of the existing porous MOF material and provide a nickel-based metal organic framework Ni-MOF material. The material has high adsorption quantity and firm adsorption, and can seal iodine molecules for a long time.

The invention also aims to provide a preparation method of the nickel-based metal organic framework Ni-MOF material.

The invention also aims to provide application of the nickel-based metal organic framework Ni-MOF material.

The above purpose of the invention is realized by the following technical scheme:

a Ni-MOF material with a nickel-based metal organic framework is characterized in that the chemical general formula of the Ni-MOF material is [ Ni ]₂(C₂₅H₁₈N₉)₃X]n, X are monovalent anions; said C is₂₅H₁₈N₉The ligand structure is shown as formula (I):

in each asymmetric unit of the main framework of the crystal structure of the Ni-MOF material, each ligand is connected with 4 Ni through four nitrogen atoms²⁺Coordination forms a coordination mode as shown in formula (II), two Ni²⁺Respectively coordinated with three imidazole nitrogen atoms from different ligands and three tetrazole nitrogen atoms from different ligands, and bridged with three tetrazole groups to form a dinuclear structural unit shown in formula (III), wherein the dinuclear structural unit is arranged at C₂₅H₁₈N₉Formation of three dimensions by ligand attachmentA porous frame;

preferably, X is chloride or nitrate.

Most preferably, the X is chloride ion, and when X is chloride ion, a single crystal structure is more easily obtained.

The asymmetric units of the Ni-MOF material structure contain two nickel atoms with the occupancy of 1/3, a ligand, a monovalent anion and disordered solvent molecules. The framework also has uncoordinated tetrazole N atoms, N atoms on triphenylamine units and helical one-dimensional pore channels.

Preferably, the crystals of the Ni-MOF material belong to the hexagonal system with unit cell parameters:α＝90°，β＝90°，γ＝120°。

the invention also provides a preparation method of the nickel-based metal organic framework Ni-MOF material, which comprises the following steps:

s1, mixing a ligand bis- (4-imidazolyl-1-phenyl) - [4- (5-tetrazolyl) phenyl ] amine and monovalent nickel salt at normal temperature to obtain a mixture;

s2, adding N, N '-dimethylacetamide or N, N' -dimethylformamide into the mixture to obtain a suspension, and ultrasonically dispersing the suspension;

s3, heating the suspension liquid treated in the step S2 at the constant temperature of 140-160 ℃ for reaction;

and S4, after the reaction is finished, cooling and filtering to obtain the Ni-MOF material.

Preferably, in step s1, the molar ratio of bis- (4-imidazolyl-1-phenyl) - [4- (5-tetrazolyl) phenyl ] amine to monovalent nickel salt is (1:1) to (1: 1.5).

Preferably, the monovalent nickel salt is selected from nickel chloride or nickel nitrate. Most preferably nickel chloride, a common nickel chloride being nickel chloride hexahydrate.

Preferably, in the step S2, the time of ultrasonic dispersion is 15-45 min.

Preferably, in step s2. the ultrasonic dispersion is carried out in a reaction vessel.

Preferably, in step s3, the heating reaction is carried out in a forced air drying oven.

Preferably, in the step s3, the reaction time of the heating reaction is 2 to 4 days.

Preferably, in step s4. the Ni-MOF material is in the form of purple chunks.

The invention also protects the application of the Ni-MOF material as an iodine molecule adsorbent.

Preferably, the iodine molecules are iodine molecules in an organic solvent, water or solvent vapor.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a nickel-based metal organic framework Ni-MOF material with a novel structure, which has a spiral one-dimensional pore canal, can be used for adsorption of iodine molecules without activation, is used as an iodine molecule solid adsorbent and has higher adsorption capacity on iodine molecules in organic solvents, water and iodine vapor; the experimental result shows that after the Ni-MOF material adsorbs iodine molecules, the material is simultaneously amorphized, so that the effect of more stably and more firmly capturing the iodine molecules is achieved, and the adsorbed iodine molecules can be sealed and stored for a longer time. The Ni-MOF material disclosed by the invention is simple in synthesis process and short in time consumption, and can be synthesized in only 2-4 days.

Drawings

FIG. 1 is a crystal structure diagram of the Ni-MOF material obtained in example 1.

FIG. 2 is a powder XRD of the Ni-MOF material obtained in example 1 and a simulated spectrum thereof.

FIG. 3 is a thermogram of the Ni-MOF material obtained in example 1.

FIG. 4 is a graph of the removal rate of the Ni-MOF material as an adsorbent for adsorbing iodine molecules in cyclohexane in example 2 as a function of time.

FIG. 5 is a first order kinetic fit of the adsorption of iodine molecules from cyclohexane by Ni-MOF material in example 2.

FIG. 6 is the adsorption isotherm of the Ni-MOF material in example 2 for adsorption of iodine molecules in cyclohexane.

FIG. 7 is a plot of a Lang-muir adsorption equation fit to the adsorption isotherm data for the adsorption of iodine molecules from cyclohexane by Ni-MOF material in example 2.

FIG. 8 is a graph of the adsorption amount of the Ni-MOF material to iodine molecules in iodine vapor versus time in example 4.

FIG. 9 is a PXRD pattern after adsorption of iodine molecules by the Ni-MOF material of example 5.

FIG. 10 shows the result of adsorption of iodine molecules₂Thermogravimetric plot of @ Ni-MOF material.

Detailed Description

The invention is further described with reference to the drawings and the following detailed description, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Unless otherwise indicated, reagents and materials used in the following examples are commercially available.

Example 1: preparation and characterization of Ni-MOF materials

Uniformly mixing ligand di- (4-imidazolyl-1-phenyl) - [4- (5-tetrazolyl) phenyl ] amine (0.1mmol,44.5mg) and nickel chloride hexahydrate (0.1mmol,23.8mg) at normal temperature to obtain a mixture, then adding N, N' -dimethylacetamide (11mL) into the mixture to obtain a suspension, putting the suspension into a reaction kettle lining for ultrasonic treatment for 30 minutes, putting the reaction kettle filled with the suspension into a forced air drying box, reacting for 3 days at 150 ℃, slowly cooling to room temperature, and filtering to obtain a purple blocky Ni-MOF material, namely the metal organic framework material Ni-MOF. Sufficient amounts of Ni-MOF material can be obtained by multiple repetitions.

The structural characterization results of the Ni-MOF provided in this example are as follows:

(1) single crystal X-ray diffraction measurement

Selecting proper single crystals from the obtained Ni-MOF, and collecting X-ray diffraction data on a Bruker APEX-II CCD single crystal diffractometer (Ga-Ka, graphite monochromator) at 193K. The crystal structure is solved by a direct method, the analysis and the refinement of the structure are completed by a SHELXTL-2016 program package, all non-hydrogen atoms are anisotropically refined by a full matrix least square method F2, the hydrogen atom coordinates of the organic ligand are obtained by theoretical hydrogenation, and solvent molecules in holes are removed by utilizing a PLATON/SQUEEZE program. The main crystallographic data are shown in table 1.

The single crystal X-ray diffraction result shows that the asymmetric unit of the structure contains two nickel atoms with the occupancy of 1/3, a ligand, a chloride ion and disordered solvent molecules. In the structure, two nickel ions are bridged through three tetrazole groups to form a dinuclear secondary structural unit, and the dinuclear secondary structural unit is further connected into a three-dimensional framework through two imidazole groups. In the framework, there are uncoordinated tetrazole N atoms, N atoms on triphenylamine units, and helical one-dimensional channels. The structure is shown in figure 1.

Table 1: crystallographic data and refinement parameters of Ni-MOF

^aR₁＝Σ||F_o|-|F_c||/|F_o|,^bwR₂＝[Σw(F_o ²-F_c ²)²/Σw(F_o ²)²]^1/2,where w＝1/[σ²(F_o ²)+(aP)₂+bP].P＝(F_o ²+2F_c ²)/3.

Refinement results are based on the data from squeeze processing.

(2) Powder X-ray diffraction measurement

FIG. 2 is an X-ray powder diffraction pattern of the Ni-MOF material of this example, showing that the phase purity of the synthesized product is higher as compared to the simulated spectra obtained by single crystal-X-ray.

(3) Thermogravimetric analysis

FIG. 3 is a thermogravimetric plot of the Ni-MOF material of this example, analyzed from the plot, with a weight loss of 8.8% from room temperature to around 90 ℃ due to the loss of water molecules adsorbed by the material, a weight loss between 130 ℃ and 210 ℃ due to the loss of N, N' -dimethylacetamide molecules in the pores, and the Ni-MOF material framework does not begin to decompose until after 300 ℃, demonstrating that the material is very stable.

Example 2: adsorption of iodine in cyclohexane by Ni-MOF material

Ni-MOF material (5mg) is added into cyclohexane solution of iodine (200mg/L,20mL), the mixture is stirred uniformly at room temperature, the concentration of iodine is detected by ultraviolet-visible spectrum (judged by the absorption peak intensity at 521 nm), the change of the removal rate along with time is calculated and shown in FIG. 4, the adsorption of the material to iodine is faster in the first 5 hours, the material is basically balanced after 10 hours, and the removal rate reaches 90%. The adsorption kinetics data are shown in FIG. 5, which has good linear relation and conforms to the first order kinetics equation (R)²＝0.996)。

The testing method of the adsorption isotherm comprises the following steps: soaking a Ni-MOF material (3mg) in 20mL of an iodocyclohexane solution with the concentration of 20-400 mg/L, testing the iodine concentration by an ultraviolet-visible spectrophotometer and calculating the adsorption quantity, wherein the result is shown in figure 6, the maximum adsorption quantity is 442mg/g, the result is shown in figure 7 by comparing Freundlich with the Themkin equation, and the data more accord with the Langmuir equation (R)²0.993), it was seen that the adsorption sites in the material were uniformly distributed.

Example 3: adsorption of Ni-MOF material to iodine in water

An aqueous solution with iodine concentration of 447ppM was prepared by adding potassium iodide to aid dissolution. The Ni-MOF material (30mg) was added to 10mL of a 447ppM iodine solution, stirred for 36 hours, and passed over Na₂S₂O₃And titrating the concentration of iodine molecules in water after complete adsorption by using the standard solution, and calculating the saturated adsorption quantity. The adsorption capacity of the Ni-MOF obtained by the experiment on iodine in an aqueous solution is 352 mg/g.

Example 4: adsorption of iodine from iodine vapor by Ni-MOF materials

The Ni-MOF material (30mg) was placed in a 2mL glass sample bottle, the sample bottle was placed in a 25mL glass vial, and 100mg of elemental iodine was added to the glass vial, without contacting the Ni-MOF material. The whole device is placed in an oven at 85 ℃ for heating, and the adsorption amount data is obtained by measuring the weight of the Ni-MOF material at different times. As shown in FIG. 8, the weight of the Ni-MOF material increased with time, and the adsorption equilibrium was reached after 7 hours, with an adsorption amount of 1.68g/g, corresponding to 8 iodine molecules per Ni atom.

Example 5: detection of adsorption stability of Ni-MOF material

Ni-MOF Material (I) after adsorption of iodine₂@ Ni-MOF) X-powder diffraction, the results are shown in fig. 9: the Ni-MOF shows structural transformation to an amorphous state after adsorbing iodine simple substance, which indicates that holes around the adsorbed iodine molecules collapse, thereby more stably capturing the iodine molecules.

Will I₂The @ Ni-MOF sample was washed three times with ethanol to remove iodine molecules that may be adsorbed on the surface, and after soaking 10mg of the sample in 20mL of water and methanol, respectively, for seven days, ICP and thermogravimetry were measured. Iodine concentration was measured by ICP and calculated to give only 1.8% and 7.5% iodine release in water and methanol, respectively; thermogravimetric analysis is shown in fig. 10, adsorbed iodine molecules need to be desorbed only when the temperature exceeds 130 ℃, and the fact that the Ni-MOF material prepared by the method can stably and firmly adsorb the iodine molecules is proved.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.