MOF (Metal Organic Framework) crystal-glass composite membrane for gas separation as well as preparation method and application of MOF crystal-glass composite membrane

Abstract

The invention belongs to the field of film preparation, and particularly relates to an MOF crystal-glass composite film and a preparation method and application thereof. The invention provides an MOF (Metal Organic Framework) crystal-glass composite film for gas separation as well as a preparation method and application of the MOF crystal-glass composite film, aiming at overcoming the defects in the prior art, including the problems of high preparation cost, poorer mechanical property, grain boundary defects and the like of a traditional MOF film. According to the technical scheme provided by the invention, a unique MOF crystal-glass composite structure is introduced, so that efficient gas separation performance is realized, and meanwhile, the preparation complexity and cost are remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the field of membrane preparation, and specifically relates to a MOF crystal-glass composite membrane and a preparation method and application thereof. Background Art

[0002] As an efficient means of gas capture and purification, membrane separation technology has been widely used in the fields of chemical industry, petroleum and natural gas, environmental protection, etc., due to its significant advantages such as low energy consumption, simple operation, high cost-effectiveness and small footprint. In recent years, various membrane materials have been developed, including polymer membranes, mixed matrix membranes, zeolite membranes and metal-organic framework (MOF) membranes. Among them, MOF membranes have become one of the important candidates for gas separation membrane materials due to their ultra-high specific surface area, structural diversity and adjustable pore properties. However, the practical application of pure MOF membranes still faces multiple challenges. First, its preparation cost is high, which limits the feasibility of large-scale application; second, due to the brittleness of MOF materials themselves, its mechanical strength is low and it is difficult to withstand high-pressure operations in complex industrial environments; in addition, MOF membranes are prone to grain boundary defects during the preparation process, which not only affects its gas separation selectivity, but also weakens the overall stability of the membrane. These problems have seriously hindered the widespread application of MOF membranes in industrial gas separation. In order to overcome the above limitations, mixed matrix membranes (MMMs) have gradually become a research hotspot. By filling MOF materials into polymer matrices, mixed matrix membranes combine the flexibility and film-forming properties of polymers with the high gas separation performance of MOF materials, showing great potential for improving gas separation efficiency. However, due to the significant differences in the physical and chemical properties of MOF and polymers, the compatibility between the two is poor, and defects are easily generated at the interface, resulting in decreased selectivity and mechanical properties of mixed matrix membranes. In addition, the filling amount of MOF in the polymer matrix is ​​limited, and high filling amounts often lead to poor processability of the membrane, further restricting the improvement of the performance of mixed matrix membranes.

[0003] As an emerging type of metal-organic coordination material, MOF glass has attracted increasing attention in the field of gas separation membranes due to its solid-liquid phase transition characteristics and unique pore structure. MOF glass can be melted into a liquid state at a specific temperature and transformed into a glass state by quenching and cooling, thereby effectively overcoming the grain boundary defects of traditional MOF membranes and giving them excellent processing properties. This unique property makes MOF glass show great potential in the preparation of high-performance gas separation membranes. However, the porosity of MOF glass often decreases significantly during the melting process, thereby weakening the gas flux and limiting its separation performance. Therefore, optimizing the pore structure of MOF glass to improve its gas separation performance is still one of the key issues that need to be solved urgently.

[0004] Although some studies have attempted to improve the pore structure of MOF glass and prepare MOF crystal-glass composite membranes by introducing porous materials, existing research has mainly focused on the ZIF (zeolite imidazolate framework) series of materials. This type of MOF glass usually requires a higher operating temperature (over 400°C) during the membrane preparation process. On the one hand, the higher operating temperature will lead to significant energy consumption and increased preparation costs. On the other hand, the high temperature environment will also affect the stability of the porous material to a certain extent, thereby further affecting the performance of the composite membrane. Therefore, the development of MOF crystal-glass composite membrane preparation technology suitable for low temperature conditions is not only an effective way to deal with the energy consumption and material stability problems of traditional high-temperature processes, but also provides a broader prospect for the research and application of new functional separation membranes. Summary of the invention

[0005] The present invention aims to provide a method for preparing a MOF crystal-glass composite membrane for gas separation to overcome the deficiencies in the prior art, including the high preparation cost, poor mechanical properties and grain boundary defects of traditional MOF membranes. The technical solution of the present invention achieves high-efficiency gas separation performance by introducing a unique MOF crystal-glass composite structure, while significantly reducing the preparation complexity and cost.

[0006] Specifically, the present invention provides a MOF crystal-glass composite membrane for gas separation, wherein the MOF crystal-glass composite membrane comprises MOF glass as a continuous phase and non-melting MOF crystals as a dispersed phase, wherein the mass ratio of the MOF glass to the MOF crystals is 1~80:99~20, and the MOF glass is formed by heating and melting MOF particles having a melting temperature of 130~200°C and then rapidly quenching and cooling.

[0007] Preferably, the non-melting MOF crystal is any one of zirconium-based MOF, M-MOF-74 series, M-HKUST-1 series or M-SIFSIX-3.

[0008] Preferably, the zirconium-based MOF is UiO-66 or MOF-801, M of the M-MOF-74 is Mg, Zn, Ni, Co, or Cu, M of the M-HKUST-1 is Zn, Cu, Fe, or Cr, and M of the M-SIFSIX-3 is Zn, Ni, Co, Cu, or Fe.

[0009] Preferably, the MOF particles are ZnCP_BIm, CoCP_2-CH 3 -BIm, CuCP_BIm, ZnCP_5-NH 2 -BIm, CuCP_BIm, CoCP_2-CH 3 -One of BIm.

[0010] Preferably, the MOF glass consists of imidazole ligands, a metal source and an acid.

[0011] Preferably, the molar ratio of the imidazole ligand, the metal source and the acid is 1-3:1-3:3.

[0012] Preferably, the metal source is selected from one or more of zinc oxide, zinc hydroxide, cobalt oxide, copper oxide, zinc acetate, cobalt acetate, copper acetate or their hydrates; the imidazole ligand is selected from one or more of benzimidazole, 2-methylbenzimidazole, 5,6-dimethylbenzimidazole, 5-methylbenzimidazole, 5-aminobenzimidazole, 5-chlorobenzimidazole or 2-ethylbenzimidazole; the acid is one or both of phosphoric acid and nitric acid.

[0013] The present invention also provides a method for preparing a MOF crystal-glass composite membrane for gas separation, which comprises the following steps: (a) preparing MOF particles that are meltable and capable of forming a glassy state by a solid-phase reaction of a precursor mixture capable of generating MOF glass; (b) uniformly mixing the MOF particles and the non-melting MOF crystals in a predetermined ratio, and pressing them into a sheet having self-supporting properties; (c) heat treating the thin film at 130-200° C. to melt the MOF particles into a liquid state and realize a glass transition during cooling, thereby finally obtaining a self-supporting MOF crystal-glass composite film.

[0014] Preferably, the solid phase reaction in step (a) is simple grinding or ball milling; and the pressing in step (b) is mechanical tableting.

[0015] Preferably, the heat treatment time in step (c) is 0.1-1 h, and the cooling is selected from natural cooling or rapid quenching.

[0016] The MOF crystal-glass composite membrane for gas separation prepared by the present invention can be used in gas separation, and the gas separation system includes H 2 / CO 2 , CO 2 / N 2 and N 2 / CH 4 .

[0017] Compared with the prior art, the present invention has the following advantages: First, the present invention provides a method for preparing MOF crystal-glass composite membrane at a relatively low temperature (130~200℃). On the one hand, low-temperature preparation can significantly reduce energy consumption and improve the economy and sustainability of the preparation process; on the other hand, the lower operating temperature can avoid the damage of high temperature to the porous material and ensure that the performance of the composite membrane is not destroyed.

[0018] Secondly, the introduction of the non-melting MOF crystals of the present invention significantly improves the porosity of the membrane and enhances the flux performance of gas separation; the presence of MOF glass effectively improves the interfacial compatibility of the membrane, making the structure of the membrane more compact and stable, and significantly improving the mechanical strength and operational stability of the membrane. By rationally designing the composite structure of MOF crystals and glass, the membrane greatly optimizes the gas separation flux performance without sacrificing selectivity, showing a wide potential for multi-component gas separation.

[0019] Finally, the present invention can flexibly adjust the types and ratios of MOF glass and MOF crystals to meet different gas separation requirements, providing a new solution for the development of efficient and low-cost separation membrane materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the X-ray diffraction pattern of ZnCP_BIm synthesized in Example 1 of the present invention; Figure 2 This is a differential scanning calorimetry-thermogravimetric analysis diagram of ZnCP_BIm synthesized in Example 1 of the present invention; Figure 3 This is a differential scanning calorimetry diagram of the composite of meltable ZnCP_BIm and infusible UiO-66 in Examples 1-3 of the present invention; Figure 4 This is the X-ray diffraction diagram of the ZnCP_BIm glass and the unmeltable UiO-66 composite in Example 1-3 of the present invention; Figure 5 The gas permeation rate and selectivity of the composite membrane samples in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention will now be described in detail. These descriptions are not intended to limit the scope of the present invention, but are intended to provide more specific descriptions and explanations of certain aspects, features, and embodiments of the present invention.

[0022] Without departing from the spirit and scope of the present invention, the specific embodiments described in this specification may be subjected to various improvements and changes, which will be apparent to those skilled in the art. Based on the contents of this specification, the technician can also easily obtain other embodiments. Therefore, the description and embodiments of the present invention are only examples and should not be regarded as limitations of the present invention.

[0023] Embodiment 1 First, 219.5 mg zinc acetate dihydrate, 236.28 mg BIm, 210 μL phosphoric acid (mass concentration 85%) and an appropriate amount of ethanol were placed in a mortar and ground for 20 minutes. The resulting solid was placed in a 100 °C vacuum oven and dried for 10 hours to obtain ZnCP_BIm material. The structure of ZnCP_BIm and its sample after 200 °C was obtained by X-ray diffraction ( Figure 1 ), differential scanning calorimetry-thermogravimetric analysis results show that its melting point is about 130°C and the decomposition temperature is 200°C ( Figure 2 Then, 90 mg and 10 mg (mass ratio of 9:1) of ZnCP_BIm and UiO-66 powder were mixed and pressed into tablets to prepare discs with a diameter of 7 mm and a thickness of about 350 μm. The differential scanning calorimetry results are shown in Figure 3 As shown, an endothermic peak appears at about 130 °C. Finally, the obtained disc was placed in a furnace at 190 °C for calcination for 60 min. After cooling, a composite film composed of ZnCP_BIm glass and UiO-66 crystals was obtained, marked as sample 1, and its structure was obtained by X-ray diffraction ( Figure 4 ), UiO-66 exists in the composite membrane. The membrane performance is obtained by pure gas testing, and the test pressure difference is 1 bar ( Figure 5 ).

[0024] Embodiment 2 First, 81.4 mg zinc oxide, 236.28 mg BIm, 210 µL phosphoric acid (mass concentration 85%) and an appropriate amount of ethanol were placed in a mortar and ground for 20 minutes. The resulting solid was placed in a 100 °C vacuum oven and dried for 10 hours to obtain the ZnCP_BIm material. Then, 70 mg and 30 mg (mass ratio of 7:3) of ZnCP_BIm and UiO-66 powders were mixed and pressed to prepare a disc with a diameter of 7 mm and a thickness of about 350 μm. The differential scanning calorimetry results are shown in Figure 2. Figure 3 As shown, an endothermic peak appears at about 130 °C. Finally, the obtained disc was placed in a furnace at 200 °C for calcination for 15 min. After cooling, a composite film composed of ZnCP_BIm glass and UiO-66 crystals was obtained, marked as sample 2, and its structure was obtained by X-ray diffraction ( Figure 4 ), UiO-66 exists in the composite membrane, and the membrane performance is obtained by pure gas testing with a test pressure difference of 1 bar ( Figure 5 ).

[0025] Embodiment 3 First, 99.4 mg zinc hydroxide, 236.28 mg BIm, 210 µL phosphoric acid (85%) and an appropriate amount of ethanol were placed in a mortar and ground for 20 minutes. The resulting solid was placed in a 100 °C vacuum oven and dried for 10 hours to obtain the ZnCP_BIm material. Then, 50 mg and 50 mg of ZnCP_BIm and UiO-66 powders were mixed and pressed to prepare a disc with a diameter of 7 mm and a thickness of about 350 μm. The differential scanning calorimetry results are shown in Figure 2. Figure 3 As shown, an endothermic peak appears at about 130 °C. Finally, the obtained disc was placed in a furnace at 200 °C for calcination for 60 min. After cooling, a composite film composed of ZnCP_BIm glass and UiO-66 crystals was obtained, marked as sample 3, and its structure was obtained by X-ray diffraction ( Figure 4 ), UiO-66 exists in the composite membrane, and the membrane performance is obtained by pure gas testing with a test pressure difference of 1 bar ( Figure 5 ).

[0026] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A MOF crystal-glass composite membrane for gas separation, characterized in that: The MOF crystal-glass composite film includes MOF glass as a continuous phase and non-melting MOF crystals as a dispersed phase, the mass ratio of the MOF glass to the MOF crystals is 1~80:99~20, and the MOF glass is formed by heating and melting MOF particles with a melting temperature of 130~200°C and then rapidly quenching and cooling.

2. The MOF crystal-glass composite film according to claim 1, characterized in that: The non-melting MOF crystal is any one of zirconium-based MOF, M-MOF-74 series, M-HKUST-1 series or M-SIFSIX-3.

3. The MOF crystal-glass composite film according to claim 2, characterized in that: The zirconium-based MOF is UiO-66 or MOF-801, the M of the M-MOF-74 is Mg, Zn, Ni, Co, or Cu, the M of the M-HKUST-1 is Zn, Cu, Fe, or Cr, and the M of the M-SIFSIX-3 is Zn, Ni, Co, Cu, or Fe.

4. The MOF crystal-glass composite film according to claim 1, characterized in that: The MOF glass consists of imidazole ligands, metal sources and acid.

5. The MOF crystal-glass composite film according to claim 4, characterized in that: The molar ratio of the imidazole ligand, the metal source and the acid is 1-3:1-3:

3.

6. The MOF crystal-glass composite film according to claim 4, characterized in that: The metal source is selected from one or more of zinc oxide, zinc hydroxide, cobalt oxide, copper oxide, zinc acetate, cobalt acetate, copper acetate or their hydrates; the imidazole ligand is selected from one or more of benzimidazole, 2-methylbenzimidazole, 5,6-dimethylbenzimidazole, 5-methylbenzimidazole, 5-aminobenzimidazole, 5-chlorobenzimidazole or 2-ethylbenzimidazole; the acid is one or both of phosphoric acid and nitric acid.

7. A method for preparing a MOF crystal-glass composite membrane for gas separation as claimed in claim 1, comprising the following steps: (a) preparing MOF particles that are meltable and capable of forming a glassy state by a solid-phase reaction of a precursor mixture capable of generating MOF glass; (b) uniformly mixing the MOF particles and the non-melting MOF crystals in a predetermined ratio, and pressing them into a sheet having self-supporting properties; (c) heat treating the thin film at 130-200° C. to melt the MOF particles into a liquid state and realize a glass transition during cooling, thereby finally obtaining a self-supporting MOF crystal-glass composite film.

8. The preparation method according to claim 7, characterized in that: The solid phase reaction in step (a) is simple grinding or ball milling; the pressing in step (b) is mechanical tablet pressing.

9. The preparation method according to claim 7, characterized in that: The heat treatment time in step (c) is 0.1-1 h, and the cooling is selected from natural cooling or rapid quenching.

10. The MOF crystal-glass composite membrane for gas separation according to claim 1 is used in gas separation, and the gas separation system includes H2 / CO2, CO2 / N2 and N2 / CH4.

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