A method for preparing a high porosity vitrifiable MOF material

Abstract

This invention belongs to the field of metal-organic framework (MOF) functional material preparation technology, specifically relating to a method for preparing a high-porosity vitrifiable MOF material, comprising the following steps: dissolving zinc acetate dihydrate, imidazole, and 6-chlorobenzimidazole in N,N-di-n-propylformamide solvent, mixing thoroughly to obtain a homogeneous precursor solution; sealing the precursor solution and placing it in a constant-temperature oven for reaction, allowing MOF crystals to slowly nucleate and grow; after the reaction, centrifuging the reaction product, collecting the solid product, and repeatedly washing it with anhydrous methanol; drying and activating the washed product in an inert environment to obtain a vitrifiable MOF material with the target porosity. This invention uses a low-temperature solvothermal method to controllably synthesize a high-crystallinity, high-porosity vitrifiable MOF crystalline material, solving the problems of low porosity, poor glassization performance, and complex preparation processes in existing vitrifiable materials.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic framework functional material preparation technology, specifically relating to a method for preparing a high-porosity vitrifiable MOF material. Background Technology

[0002] Metal-organic frameworks (MOFs) have shown great promise for applications in gas adsorption, separation, catalysis, and energy storage due to their high specific surface area, tunable pore structure, and rich chemical functions. Among them, zeolite imidazolate frameworks (ZIF series) have become an important research focus for vitrifiable MOFs due to their high coordination stability and tunable framework flexibility.

[0003] Glass made from MOF materials is called fourth-generation glass material. It is made by heating crystalline MOF materials to above the melting temperature and then quenching them. It has the structural characteristics of short-range order and long-range disorder, which gives it the advantages of no grain boundaries, easy processing and isotropy. It is generally used to manufacture gas separation membranes, flexible functional devices and the like.

[0004] Existing glassable MOF materials are generally ZIF-62 and its derivatives, which have low porosity. During the melting process, densification often occurs, which may cause the loss of the material's pore structure. As a result, the synthesis of glassable MOF materials still faces problems such as simple framework design, difficulty in porosity control, and complex preparation process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-porosity vitrifiable MOF materials, which can controllably synthesize high-crystallinity, high-porosity vitrifiable MOF crystalline materials using a low-temperature solvothermal method, thus solving the problems of low porosity, poor vitrification performance, and complex preparation process of existing vitrifiable materials.

[0006] The specific technical solution adopted by this invention is as follows: A method for preparing a high-porosity vitrifiable MOF material includes the following steps: Zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole were dissolved in N,N-di-n-propylformamide solvent and mixed evenly to obtain a homogeneous precursor solution. The precursor solution was sealed and placed in a constant temperature oven for reaction, allowing the MOF crystals to nucleate and grow slowly. After the reaction was completed, the reaction product was centrifuged, the solid product was collected, and it was repeatedly washed with anhydrous methanol. The washing product was dried and activated in an inert environment to obtain a vitrifiable MOF material with the target porosity.

[0007] As an optional embodiment, the molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution is 2.3:0.5-0.909:0.091-0.5.

[0008] As an optional configuration, the target porosity is set to a specific surface area of ​​1500. ~3000 .

[0009] As an alternative, the N,N-di-n-propylformamide used as a solvent in the reaction has a purity higher than 95%, and zinc acetate dihydrate, imidazole, and 6-chlorobenzimidazole in the N,N-di-n-propylformamide are completely dissolved to form a clear precursor solution without precipitate.

[0010] As an alternative, the reaction temperature is set to 45℃~65℃ and the reaction time is set to 5d~10d.

[0011] As an optional approach, the centrifugation speed of the reaction product is set to 8000 r / min, and the centrifugation time is set to 5 min.

[0012] As an optional solution, the vacuum drying temperature is set to 60°C and the drying time is set to 12 hours.

[0013] As an alternative, the inert environment is configured with vacuum, nitrogen or argon, and the heating rate for drying and activation is configured to be 3K / min to 10K / min.

[0014] As an optional procedure, the dissolution, centrifugation, and washing are all performed at room temperature.

[0015] The use of a high-porosity vitrifiable MOF material, wherein the high-porosity vitrifiable MOF material is a high-porosity vitrifiable MOF material prepared according to the preparation method of the high-porosity vitrifiable MOF material, and the high-porosity vitrifiable MOF material is used for gas adsorption and separation, catalytic reaction or glass membrane preparation.

[0016] The technical effects achieved by this invention are as follows: This invention, for the first time in the preparation of metal-organic framework functional materials, uses zinc acetate dihydrate as the metal source and employs a synergistic coordination mechanism of imidazole and 6-chlorobenzimidazole dual ligands to prepare high-porosity vitrifiable MOF materials via a low-temperature solvothermal method. The preparation method has the advantages of mild conditions, controllable process, and high product crystallinity, providing a theoretical basis for the industrial-scale preparation of vitrifiable MOF materials.

[0017] This invention optimizes the synthesis process of metal-organic framework (MOF) functional materials by regulating the structural properties of the materials based on the ratio of auxiliary ligands and the reaction temperature. The resulting MOF material possesses both high porosity and excellent glass transition properties, providing a high-performance precursor for subsequent glass transition processing and functional applications. The preparation method is simple, the conditions are mild, and it is suitable for industrial production. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for preparing a high-porosity vitrifiable MOF material according to the present invention; Figure 2 (a) is a scanning electron microscope image of the vitrifiable MOF material prepared in Example 1 of the present invention; Figure 2 (b) is the present invention Figure 2 Scanning electron microscope image of MOF glass prepared from vitrifiable MOF materials; Figure 3 (a) is the present invention Figure 2 The nuclear magnetic resonance spectrum of the glassable MOF material prepared in the process; Figure 3 (b) is the present invention Figure 3 Nuclear magnetic resonance spectrum of MOF glass prepared from vitrifiable MOF materials; Figure 4 This is the invention Figure 2 X-ray diffraction patterns of vitrifiable MOF materials and prepared MOF glasses were obtained. Figure 5 This is the invention Figure 2 Thermogravimetric-differential scanning calorimetry (TGC-DSC) image of the glassable MOF material prepared in [the preparation process]; Figure 6 (a) is the present invention Figure 2 BET adsorption isotherm curves of the glassable MOF material prepared in [the original text]; Figure 6 (b) is the present invention Figure 2 BET adsorption isotherm curves of MOF glasses prepared from vitrifiable MOF materials. Detailed Implementation

[0019] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0020] Example 1: like Figures 1-6As shown, a method for preparing a high-porosity vitrifiable MOF material includes the following steps: Zinc acetate dihydrate, imidazole, and 6-chlorobenzimidazole were dissolved in N,N-di-n-propylformamide solvent in a reaction flask and mixed thoroughly to obtain a homogeneous precursor solution. The molar ratio of zinc acetate dihydrate, imidazole, and 6-chlorobenzimidazole in the solution is 2.3:0.875:0.125. The chemical formula of the N,N-di-n-propylformamide solvent is [missing information]. It is a pale yellow or grayish-yellow liquid at room temperature. Users should operate it under a portable air-purifying hood and protect their head and face. The precursor solution was sealed in a reaction flask and placed in a constant temperature oven at 55°C for 7 days to allow MOF crystals to nucleate and grow slowly. After the reaction was completed, the reaction product was centrifuged, the solid product was collected, and washed three times with anhydrous methanol, soaking the solid product for 3 hours each time. The washing product was dried and activated in an inert environment at 60°C for 12 hours to obtain a vitrifiable MOF material with the target porosity.

[0021] Specifically, the chemical formula of the vitrifiable MOF material is: , express stoichiometric coefficients, express stoichiometric coefficients.

[0022] The preparation method of this application involves using a solvothermal synthesis method to prepare a high-porosity vitrifiable MOF material, and then using the MOF material to prepare MOF glass. Simultaneously, images of the MOF material and MOF glass are taken. Figure 2 The scanning electron microscope image shown Figure 3 The nuclear magnetic resonance spectrum shown Figure 4 The X-ray diffraction pattern shown Figure 5 The thermogravimetric-differential scanning calorimetry (TGC) image of the MOF material shown is as follows: Figure 6 The BET adsorption isotherm curve shown is compared with the corresponding physical element diagram of MOF crystals obtained by the traditional hydrothermal synthesis method. It can be seen that the traditional hydrothermal synthesis method has overcome the drawbacks of loose structure, poor stability and low separation efficiency in the process of high-temperature sintering after attaching MOF crystals to a hard substrate.

[0023] In summary, this application leverages the synergistic coordination of imidazole and 6-chlorobenzimidazole dual ligands to precisely construct a regular crystalline structure, enabling the synthesis of pure-phase MOF precursor materials with high crystallinity, high specific surface area, and high pore connectivity. Compared to traditional high-temperature synthesis, the low-temperature solvothermal preparation route offers milder reaction conditions, complete crystal formation, and uniform pore structure arrangement, providing a high-quality raw material foundation for subsequent MOF glass phase transition and functionalized thin films.

[0024] See attached document Figure 2 In this embodiment, a vitrifiable MOF material and its MOF glass were prepared. Under a scanning electron microscope, the MOF crystals showed uniform nucleation, regular grains, no obvious agglomeration or defects, and high crystallinity. The pore structure of the vitrifiable MOF material was complete and orderly, without blockage or collapse, and it showed a clear trend of glass transition.

[0025] Example 2: It is basically the same as Example 1, and the similarities are the same as in Example 1. The difference is that: The molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution was 2.3:0.5:0.5. The precursor solution was sealed in a reaction flask and placed in a constant temperature oven at 55°C for 7 days to allow MOF crystals to slowly nucleate and grow.

[0026] In this embodiment, the amount of 6-chlorobenzimidazole added was increased and the amount of imidazole added was decreased. After the ratio was adjusted, the coordination ratio of the two ligands was severely unbalanced. Under scanning electron microscopy, the nucleation rate of MOF crystals varied greatly, the MOF material powder agglomerated significantly, amorphous impurities precipitated in the product, and the crystallinity was greatly reduced. The MOF material had dense defects in the pore framework, which were prone to blockage and collapse when heated. The glass transition characteristics were weak, and the melting process was accompanied by thermal decomposition of the framework, making it difficult to form a complete MOF glass.

[0027] Example 3: It is basically the same as Example 1, and the similarities are the same as in Example 1. The difference is that: The molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution was 2.3:0.75:0.25. The precursor solution was sealed in a reaction flask and placed in a constant temperature oven at 55°C for 7 days to allow MOF crystals to slowly nucleate and grow.

[0028] In this embodiment, after slightly increasing the amount of 6-chlorobenzimidazole, the coordination ratio of the two ligands changed, the nucleation rate of MOF crystals accelerated, the grain size of the reaction product was slightly refined, and slight small agglomerations appeared in some parts of the MOF material sample; the MOF material as a whole maintained a pure crystalline phase without the precipitation of impurities, and the crystallinity was slightly lower than that in Example 1; the pore structure of the MOF material was intact without collapse or blockage, but the pore volume and specific surface area were lower than the optimal ratio, and the MOF material still retained the glass transition characteristics.

[0029] Example 4: It is basically the same as Example 1, and the similarities are the same as in Example 1. The difference is that: The molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution was 2.3:0.909:0.091. The precursor solution was sealed in a reaction flask and placed in a constant temperature oven at 55°C for 7 days to allow MOF crystals to slowly nucleate and grow.

[0030] In this embodiment, after slightly reducing the amount of 6-chlorobenzimidazole, lowering the reaction temperature, and extending the reaction period, the coordination reaction rate of the system slowed down, the number of MOF crystal nuclei decreased, the crystal size increased, the crystal size of the reaction product increased slightly, the MOF material powder had excellent dispersibility and no obvious agglomeration; the MOF material maintained a high-purity crystalline phase, and the crystallinity was slightly lower than that of Example 1 but better than that of Example 3; the MOF material had a complete pore structure, but the pore volume and specific surface area were lower than the optimal sample of Example 1, the glass transition trend was obvious, but the glass transition temperature increased slightly.

[0031] Example 5: It is basically the same as Example 1, and the similarities are the same as in Example 1. The difference is that: The molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution was 2.3:0.875:0.125. The precursor solution was sealed in a reaction flask and placed in a constant temperature oven at 45°C for 10 days to allow MOF crystals to nucleate and grow slowly.

[0032] In this embodiment, the same amount of material is used as in Example 1, but the coordination ratio of the two ligands is changed, the nucleation rate of MOF crystals slows down, the grain size of the reaction product increases slightly, and slight agglomeration occurs in some parts of the MOF material powder. The reaction product is still a pure crystalline phase without the formation of impurity crystals, and the crystallinity is slightly lower than that in Example 1. The pore framework of the MOF material is intact without collapse or blockage, the specific surface area and pore volume decrease slightly, and the MOF material still has a clear glass transition trend.

[0033] Example 6: It is basically the same as Example 1, and the similarities are the same as in Example 1. The difference is that: The molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution was 2.3:0.875:0.125. The precursor solution was sealed in a reaction flask and placed in a constant temperature oven at 65°C for 5 days to allow MOF crystals to slowly nucleate and grow.

[0034] In this embodiment, the same amount of feed was used as in Example 1. After the reaction temperature was increased and the reaction time was shortened, the nucleation rate of MOF crystals was too fast, the grains were refined and the particle size distribution became wider, and the fine powder agglomeration increased. The reaction product maintained a single crystal phase structure, and the crystallinity was slightly reduced compared to Example 1. The pore structure was intact without large-area collapse. The pore volume and specific surface area were slightly lower than the optimal sample in Example 1. The glass transition characteristics were retained, but the glass transition temperature increased slightly.

[0035] Based on the preparation methods of Examples 1 to 6, quantitative samples were taken and numbered sequentially according to the order of the examples. The morphological characteristics, specific surface area and melting point of the samples under a scanning electron microscope were recorded respectively. The characteristics of the samples obtained in different examples are recorded as shown in Table 1 below.

[0036] Table 1. Characteristics of samples obtained from different embodiments

[0037] In summary, the optimal sample obtained by the preparation method of a high-porosity vitrifiable MOF material provided in Example 1 of this application possesses excellent porosity (specific surface area as high as 2800). It also has high thermal stability and meets the key indicator that the melting point is lower than the decomposition temperature, making it suitable as a base material for MOF glasses. This property gives the best sample great potential as an adsorption and separation material and a high-porosity glass material to cope with different scenarios such as catalysis, separation, and energy storage.

[0038] The use of a high-porosity vitrifiable MOF material, wherein the high-porosity vitrifiable MOF material is prepared according to the preparation method provided in Examples 1 to 6, and the high-porosity vitrifiable MOF material is used for gas adsorption and separation, catalytic reaction or glass membrane preparation.

[0039] The MOF material obtained by the preparation method of a high-porosity vitrifiable MOF material provided in Example 1 of this application can be used for gas adsorption and separation, catalytic reaction or glass membrane preparation.

[0040] The above description is merely an optional embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A method for preparing a high-porosity vitrifiable MOF material, characterized in that, Includes the following steps: Zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole were dissolved in N,N-di-n-propylformamide solvent and mixed evenly to obtain a homogeneous precursor solution. The precursor solution was sealed and placed in a constant temperature oven for reaction, allowing the MOF crystals to nucleate and grow slowly. After the reaction was completed, the reaction product was centrifuged, the solid product was collected, and it was repeatedly washed with anhydrous methanol. The washing product was dried and activated in an inert environment to obtain a vitrifiable MOF material with the target porosity.

2. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The molar ratio of zinc acetate dihydrate, imidazole and 6-chlorobenzimidazole in the solution is 2.3:0.5-0.909:0.091-0.

5.

3. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The target porosity is set to a specific surface area of ​​1500. ~3000 .

4. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The N,N-di-n-propylformamide used as a solvent in the reaction has a purity higher than 95%. The zinc acetate dihydrate, imidazole, and 6-chlorobenzimidazole in the N,N-di-n-propylformamide are completely dissolved to form a clear precursor solution without precipitate.

5. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The reaction temperature was set to 45℃~65℃, and the reaction time was set to 5d~10d.

6. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The centrifugation speed of the reaction product was set to 8000 r / min, and the centrifugation time was set to 5 min.

7. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The vacuum drying temperature is set to 60℃ and the drying time is set to 12h.

8. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The inert environment is configured as a vacuum, nitrogen, or argon, and the heating rate for drying and activation is configured as 3K / min to 10K / min.

9. The method for preparing a high-porosity vitrifiable MOF material according to claim 1, characterized in that: The dissolution, centrifugation, and washing were all performed at room temperature.

10. An application of a high-porosity vitrifiable MOF material, characterized in that: The high-porosity vitrifiable MOF material is prepared by the preparation method according to any one of claims 1-9, and the high-porosity vitrifiable MOF material is used for gas adsorption and separation, catalytic reaction or glass membrane preparation.

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