Metal organic framework gel hybrid matrix membrane, its preparation method and application

Abstract

The application provides a metal organic framework gel mixed matrix membrane for gas separation and a preparation method and application thereof, and belongs to the field of gas membrane separation. The metal organic framework gel mixed matrix membrane comprises a polymer matrix and a metal organic framework gel. The metal organic framework gel is composed of discrete nanoparticles of crystalline metal organic frameworks through non-covalent interaction force (mainly van der Waals force). The metal organic framework gel has a head-to-tail 3D interconnected gel network structure, higher flexibility and better dispersibility and stability in a solution. Therefore, the metal organic framework gel is more easily uniformly distributed in the polymer matrix and forms a continuous channel, and the H2 permeation speed is accelerated. The metal organic framework gel mixed matrix membrane provided by the application has high H2 permeation coefficient and H2 / CH4 selectivity, and is suitable for H2 gas separation.

Description

Technical Field

[0001] This invention belongs to the field of gas membrane separation, specifically relating to a metal-organic framework gel hybrid matrix membrane, its preparation method, and its application in H2 separation. Background Technology

[0002] Hydrogen is widely used in numerous industrial applications, such as fuel cells, petrochemicals, and semiconductor manufacturing. Impurities in impure hydrogen can damage equipment; for example, in fuel cells, impurities can damage the electrodes, thus reducing battery performance. Therefore, hydrogen purification is essential to ensure product quality, long equipment lifespan, and operational safety.

[0003] Membrane technology is widely recognized as a highly efficient method for H2 purification, offering advantages such as low energy consumption, cost-effectiveness, and environmental friendliness. Currently, pure polymer membranes remain the mainstream in gas separation. However, a "trade-off" effect exists between gas permeability and selectivity: membranes with high permeability have low selectivity, and vice versa. To address this "trade-off" effect, mixed matrix membranes (MMMs) have emerged, combining polymers with porous or non-porous packing materials to improve gas separation efficiency. However, mixed matrix membranes also present significant challenges. For example, the packing material may aggregate within the polymer due to its strong self-influence, creating irregular voids within the membrane and thus affecting its separation performance.

[0004] This invention addresses the problems of poor filler dispersion, easy agglomeration, and insufficient membrane performance improvement in traditional mixed matrix membrane formation processes. It employs a novel metal-organic framework gel (MOF gel) as a filler, added to a polymer to prepare a mixed matrix membrane. The MOF gel is primarily composed of discrete nanoparticles of crystalline MOF connected by non-covalent forces. Compared to traditional bulk MOF crystals, MOF gel is a 3D interconnected gel network structure with interconnected ends, exhibiting higher flexibility and better dispersibility and stability in solution. Therefore, MOF gel is more easily and uniformly distributed in the polymer matrix, forming continuous channels. Compared to pure polymer membranes and MOF mixed matrix membranes, MOF gel mixed matrix membranes show greater H2 permeability and significantly improved H2 / CH4 selectivity. Therefore, developing MOF gel mixed matrix membranes is beneficial for enhancing H2 purification efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a metal-organic framework gel hybrid matrix membrane, which enhances the uniformity of the filler in the hybrid matrix membrane and improves the H2 purification performance.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] Step (1): Prepare a 0.1–0.4 mol / L metal ion solution using methanol as the solvent, according to Zn 2+ A solution was prepared by mixing imidazole and triethylamine in a molar ratio of 1:8:8, stirring thoroughly, centrifuging, and washing the unreacted ligands three times with methanol to obtain a metal-organic framework gel.

[0008] Step (2): Dissolve an appropriate amount of polymer in an organic solvent to obtain a polymer solution;

[0009] Step (3): Using the same organic solvent as the polymer, replace the metal-organic framework gel three times to ensure that the metal-organic framework gel is evenly distributed in the same organic solvent as the polymer. Add the polymer solution dropwise to the metal-organic framework gel, sonicate and stir until the two are evenly mixed to form a casting film mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate it at room temperature for 1-4 days. Then, soak the membrane in methanol for 1-2 days. Finally, place the membrane in a vacuum oven at 80°C and dry it for 24 hours to obtain the metal-organic framework gel mixed matrix membrane.

[0010] In step (1) of this invention, the metal ions may be selected from Zn. 2+ or Co 2+ wait.

[0011] In step (2) of this invention, the polymer can be selected from polyimide, polysulfone, polyvinylidene fluoride, polyether block polyimide, self-polymerizing microporous polymer, etc.

[0012] In step (3) of this invention, the content of the metal-organic framework gel is 1 to 40 wt% of the mass of the metal-organic framework gel mixed matrix membrane.

[0013] In step (3) of this invention, the total mass concentration of the polymer and metal-organic framework gel in the casting mixture solution is 3 wt%.

[0014] Preferably, the solvent of the casting film mixing solution is selected from chloroform, ethanol-water mixture, and N,N-dimethylformamide.

[0015] In step (3) of the invention, the stirring time is 4 to 28 hours.

[0016] In step (3) of the present invention, the vacuum treatment temperature is 80-120°C and the treatment time is 24-48h.

[0017] According to one aspect of the present invention, an application of the above-described metal-organic framework gel hybrid matrix membrane in gas separation is provided.

[0018] Optionally, the metal-organic framework gel hybrid matrix membrane is used in the separation of gas mixtures containing H2.

[0019] Preferably, the gas contains at least one of N2 and CH4.

[0020] In this application, a gas mixture at a certain pressure comes into contact with one side of the metal-organic framework gel-mixed matrix membrane, thereby causing H2 to permeate the metal-organic framework gel-mixed matrix membrane to achieve gas separation.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The metal-organic framework gel-polymer matrix membrane provided by this invention comprises a polymer matrix and a metal-organic framework gel. The metal-organic framework gel exhibits good dispersibility in the mixed matrix membrane, readily forms continuous channels, demonstrates high H2 gas permeability, and simultaneously improves H2 / CH4 selectivity.

[0023] The film-forming method provided by this invention is simple and easy to implement, has a wide range of applications, and has good prospects for practical application. Attached Figure Description

[0024] Figure 1 Transmission electron microscopy (TEM) images of ZIF-8 gels (ZIF-8gel) from Examples 1-4.

[0025] Figure 2 The image shows a transmission electron microscope (TEM) image of ZIF-8 from Comparative Examples 2-5.

[0026] Figure 3 The image shows a cross-sectional electron microscope image of the membrane prepared in Example 1.

[0027] Figure 4 The image shows a cross-sectional electron microscope image of the membrane prepared in Example 2.

[0028] Figure 5 The image shows a cross-sectional electron microscope image of the membrane prepared in Example 3.

[0029] Figure 6 The image shows a cross-sectional electron microscope image of the membrane prepared in Example 4.

[0030] Figure 7 This is a cross-sectional electron microscope image of the membrane prepared in Comparative Example 1.

[0031] Figure 8 This is a cross-sectional electron microscope image of the membrane prepared in Comparative Example 2.

[0032] Figure 9 This is a cross-sectional electron microscope image of the membrane prepared in Comparative Example 3.

[0033] Figure 10 This is a cross-sectional electron microscope image of the membrane prepared in Comparative Example 4.

[0034] Figure 11 Photographs comparing the films prepared in Example 1 and Comparative Example 2.

[0035] Figure 12 The growth rate of H2 permeability and H2 / CH4 selectivity in Examples 1-4 and Comparative Examples 2-5 Detailed Implementation

[0036] The technical solution of the present invention will be further described below through several specific embodiments, but this does not limit the present application. Any variations or implementations that do not depart from the content and scope of the present invention should be included within the technical scope of the present invention.

[0037] Example 1:

[0038] Step (1): Prepare a 0.4 mol / L metal ion solution using methanol as the solvent, according to Zn 2+ A solution was prepared by mixing 2-methylimidazole and triethylamine in a molar ratio of 1:8:8, stirring thoroughly, centrifuging, and washing the unreacted ligands three times with methanol to obtain ZIF-8 gel.

[0039] Step (2): Dissolve 0.2g of self-porous polymer (PIM-1) in chloroform to obtain a PIM-1 solution;

[0040] Step (3): Replace ZIF-8gel three times with chloroform to ensure uniform distribution of ZIF-8gel in chloroform. Add PIM-1 solution dropwise to the chloroform solution containing 0.03g ZIF-8gel, sonicate and stir for 24h until the two are evenly mixed to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry for 24h to obtain a 13.0wt% ZIF-8gel / PIM-1 mixed matrix membrane.

[0041] Example 2:

[0042] Steps (1)-(2) are the same as in Example 1.

[0043] Step (3): Replace ZIF-8gel three times with chloroform to ensure uniform distribution of ZIF-8gel in the chloroform. Add PIM-1 solution dropwise to the chloroform solution containing 0.06g ZIF-8gel, sonicate and stir for 24h until the two are evenly mixed to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry for 24h to obtain a 23.0wt% ZIF-8gel / PIM-1 mixed matrix membrane.

[0044] Example 3:

[0045] Steps (1)-(2) are the same as in Example 1.

[0046] Step (3): Replace ZIF-8gel three times with chloroform to ensure uniform distribution of ZIF-8gel in the chloroform. Add PIM-1 solution dropwise to the chloroform solution containing 0.09g ZIF-8gel, sonicate and stir for 24h until the two are evenly mixed to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry for 24h to obtain a 31.0wt% ZIF-8gel / PIM-1 mixed matrix membrane.

[0047] Example 4:

[0048] Steps (1)-(2) are the same as in Example 1.

[0049] Step (3): Replace ZIF-8gel three times with chloroform to ensure uniform distribution of ZIF-8gel in the chloroform. Add PIM-1 solution dropwise to the chloroform solution containing 0.12g ZIF-8gel, sonicate and stir for 24h until the two are evenly mixed to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry for 24h to obtain a 37.5wt% ZIF-8gel / PIM-1 mixed matrix membrane.

[0050] Comparative Example 1:

[0051] Step (1): Dissolve 0.2g of PIM-1 in chloroform and stir at room temperature for 24h to form a casting solution. Pour the solution into a smooth and flat round glass petri dish and slowly evaporate at room temperature for 2 days. Then soak the membrane in methanol for 1 day and finally dry the membrane in a vacuum oven at 80℃ for 24h to obtain a pure PIM-1 membrane.

[0052] Comparative Example 2

[0053] Step (1): Prepare a 0.4 mol / L metal ion solution using methanol as the solvent, according to Zn 2+ A solution of 2-methylimidazole was prepared at a molar ratio of 1:8, stirred until homogeneous, centrifuged, and the unreacted ligand was washed three times with methanol to obtain ZIF-8.

[0054] Step (2): Dissolve 0.2g of PIM-1 in chloroform to obtain a PIM-1 solution;

[0055] Step (3): Displace ZIF-8 three times with chloroform to disperse it in the chloroform solution. Add PIM-1 solution dropwise to the chloroform solution containing 0.03g ZIF-8, sonicate and stir for 24h until the two are mixed evenly to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate it at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry it for 24h to obtain a 13.0wt% ZIF-8 / PIM-1 mixed matrix membrane.

[0056] Comparative Example 3

[0057] Steps (1)-(2) are the same as in Comparative Example 2.

[0058] Step (3): Displace ZIF-8 three times with chloroform to disperse it in the chloroform solution. Add PIM-1 solution dropwise to the chloroform solution containing 0.06g ZIF-8, sonicate and stir for 24h until the two are mixed evenly to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate it at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry it for 24h to obtain a 23.0wt% ZIF-8 / PIM-1 mixed matrix membrane.

[0059] Comparative Example 4

[0060] Steps (1)-(2) are the same as in Comparative Example 2.

[0061] Step (3): Displace ZIF-8 three times with chloroform to disperse it in the chloroform solution. Add PIM-1 solution dropwise to the chloroform solution containing 0.09g ZIF-8, sonicate and stir for 24h until the two are mixed evenly to form a casting mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate it at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry it for 24h to obtain a 31.0wt% ZIF-8 / PIM-1 mixed matrix membrane.

[0062] Comparative Example 5

[0063] Steps (1)-(2) are the same as in Comparative Example 2.

[0064] Step (3): Displace ZIF-8 three times with chloroform to disperse it in the chloroform solution. Add PIM-1 solution dropwise to the chloroform solution containing 0.12g ZIF-8, sonicate and stir for 24h until the two are mixed evenly to form a casting film mixture solution. Pour the mixture into a smooth and flat round glass petri dish and slowly evaporate it at room temperature for 2 days. Then soak the membrane in methanol for 1 day. Finally, place the membrane in a vacuum oven at 80℃ and dry it for 24h to obtain a 37.5wt% ZIF-8 / PIM-1 mixed matrix membrane.

[0065] The H2 permeability coefficient and selectivity of the mixed matrix membranes in Examples 1-4 and Comparative Examples 1-5 under conditions of 0.1 MPa and 35 °C with H2 / CH4 gas mixture are shown in Table 1.

[0066] Table 1

[0067]

[0068] Table 1 shows that incorporating ZIF-8gel and ZIF-8 into the PIM-1 matrix simultaneously enhances H2 permeability and H2 / CH4 selectivity. Notably, the ZIF-8gel / PIM-1 hybrid matrix membrane exhibits a more significant improvement in H2 performance compared to the ZIF-8 / PIM-1 hybrid matrix membrane. This phenomenon is attributed to the 3D interconnected gel network structure of ZIF-8gel, which can form continuous channels in the PIM-1 matrix, enhancing H2 transport even at low MOF loadings. H2 permeability continuously increases with increasing MOF loading. The H2 permeability coefficient of the ZIF-8gel / PIM-1 hybrid matrix membrane increases from 3801 Barrer to 7290 Barrer in the range of 0–37.5 wt%. When using low ZIF-8gel loadings (<31.0 wt%), the H2 / CH4 selectivity gradually increases. The selectivity reaches a maximum of 6.78 when the ZIF-8gel loading increases to 31.0 wt%. This indicates that ZIF-8gel effectively improves the selectivity for H2 / CH4. When using a high ZIF-8gel loading (>37.5 wt%), ZIF-8gel may generate some defects in the PIM-1 matrix, leading to a decrease in H2 / CH4 selectivity, but it is still higher than that of the pure PIM-1 membrane. In summary, compared with pure polymer membranes and ZIF-8 mixed matrix membranes, ZIF-8gel mixed matrix membranes have a larger H2 permeability coefficient and significantly improved H2 / CH4 selectivity. Therefore, developing MOF gel mixed matrix membranes is beneficial for enhancing H2 purification efficiency.

[0069] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A metal-organic framework gel hybrid matrix membrane, characterized in that, The metal-organic framework gel hybrid matrix membrane comprises a polymer matrix and a metal-organic framework gel; The metal-organic framework gel is composed of discrete nanoparticles of crystalline metal-organic frameworks through non-covalent interactions. The metal-organic framework gels were selected from zinc-based metal-organic framework gels and cobalt-based metal-organic framework gels.

2. The metal-organic framework gel hybrid matrix membrane according to claim 1, characterized in that, The zinc-based metal-organic framework gel is ZIF-8; The cobalt-based metal-organic framework gel selected is ZIF-67.

3. The metal-organic framework gel hybrid matrix membrane according to claim 1, characterized in that, The content of the metal-organic framework gel is 1 wt% to 40 wt% of the mass of the metal-organic framework gel mixed matrix membrane.

4. The metal-organic framework gel hybrid matrix membrane according to claim 1, characterized in that, The polymer matrix is ​​selected from at least one of polyimide, polysulfone, polyvinylidene fluoride, polyether block polyimide, and self-polymerizing microporous polymer.

5. A method for preparing a metal-organic framework gel hybrid matrix membrane according to any one of claims 1 to 4, characterized in that, A casting mixture containing polymer and metal-organic framework gel is formed into a film, and then subjected to vacuum treatment to obtain the metal-organic framework gel mixed matrix film.

6. The preparation method according to claim 5, characterized in that, The casting film mixture solution is obtained by stirring and mixing a solution containing polymer and a metal-organic framework gel b. The stirring time is 4 to 28 hours.

7. The preparation method according to claim 5, characterized in that, The total mass concentration of the polymer and metal-organic framework gel in the casting mixture solution is 3 wt%. The solvent of the casting mixture is selected from at least one of chloroform, ethanol-water mixture, and N,N-dimethylformamide.

8. The preparation method according to claim 5, characterized in that, The vacuum treatment is carried out at a temperature of 80–120°C for a duration of 24–48 h.

9. The application of a metal-organic framework gel hybrid matrix membrane according to any one of claims 1 to 4, or a metal-organic framework gel hybrid matrix membrane prepared by the preparation method according to any one of claims 5 to 8, in gas separation.

10. The application according to claim 9, characterized in that, Application of the metal-organic framework gel hybrid matrix membrane in the separation of gas mixtures containing H2; The gas contains at least one of N2 and CH4.

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