An anionic covalent organic framework mixed matrix membrane and a method of making and use thereof
By preparing anionic covalent organic framework hybrid matrix membranes, the interfacial compatibility problem between COF packing material and polymer matrix was solved, achieving high permeability and selectivity in gas separation performance, suitable for CO2/N2 or CO2/CH4 separation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN INST OF TECH
- Filing Date
- 2026-03-03
- Publication Date
- 2026-06-05
AI Technical Summary
Conventional COF fillers have poor interfacial compatibility with polymer matrices, and are prone to agglomeration or the formation of non-selective interfacial voids, leading to a decline in membrane performance.
An anionic covalent organic framework was prepared by reacting an imine-type covalent organic framework containing pyridine groups with bromoalkane and then exchanging it with an anionic salt. The mixture was then mixed with a polymer matrix to form a casting solution, which was dried to obtain an anionic covalent organic framework mixed matrix membrane.
Significantly improved interfacial compatibility and filler dispersibility, the membrane's CO2/CH4 separation performance exceeds the Robeson limit, making it suitable for CO2/N2 or CO2/CH4 gas separation.
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Figure CN122141482A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of gas separation membrane technology, and in particular to an anionic covalent organic framework mixed matrix membrane, its preparation method, and its application. Background Technology
[0002] Membrane separation technology has shown great potential in the field of CO2 capture and separation due to its advantages such as low energy consumption, simple operation, and environmental friendliness. Among them, hybrid matrix membranes, by dispersing inorganic or porous fillers in a polymer matrix, combine the advantages of both and are an effective strategy to overcome the limitations of the "trade-off" effect of traditional polymer membranes.
[0003] Covalent organic frameworks (COFs) are a class of crystalline porous materials formed by organic structural units linked by covalent bonds. They possess advantages such as high specific surface area, regular channels, and functionalizability, making them ideal fillers for mixed matrix membranes (MMMs). However, conventional COF fillers have poor interfacial compatibility with polymer matrices, easily leading to aggregation or the formation of non-selective interfacial voids, resulting in decreased or even deteriorated membrane performance. Summary of the Invention
[0004] The purpose of this invention is to provide an anionic covalent organic framework hybrid matrix membrane, its preparation method and application. This hybrid matrix membrane has good interfacial compatibility, high gas permeability and high selectivity, and can be used for gas separation such as CO2 / N2 or CO2 / CH4.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing anionic covalent organic framework hybrid matrix membranes, comprising the following steps: A bromine-modified covalent organic framework is obtained by mixing an imine-type covalent organic framework containing a pyridine group, a bromoalkane, and an organic solvent. The bromine-modified covalent organic framework was mixed with an anionic salt compound and water, and ion exchange was performed to obtain an anionic covalent organic framework. The anionic covalent organic framework is mixed with a polymer matrix and a dispersion solvent to obtain a casting solution; After casting the casting solution into a film, it is dried to obtain an anionic covalent organic framework mixed matrix film.
[0006] Preferably, the monomers for preparing the imine-type covalent organic framework include aldehyde ligands and amino ligands; the aldehyde ligands include one of pyromellitic methyl ether, trialdehyde phloroglucinol, and 1,3,5-tris(p-formylphenyl)benzene; The amino ligand includes one of 2,5-diaminopyridine, 5'5-diamino-2'2-bipyridine, and 4,4',4''-(pyridine-2,4,6-triyl)triphenylamine.
[0007] Preferably, the general structural formula of the bromoalkane is C1 n Br, C n Represents straight-chain alkyl groups with 2 to 20 carbon atoms.
[0008] Preferably, the molar ratio of pyridine groups to bromoalkane in the imine-type covalent organic framework is 1:1~3; the modification temperature is 40~100℃ and the time is 10~48h.
[0009] Preferably, the anion in the anionic salt compound includes Cl-. - ,Br - SiF6 - BF4 - PF6 - or NTf2 - .
[0010] Preferably, the molar ratio of pyridine groups to anionic salt compounds in the bromine-modified covalent organic framework is 1:1 to 5; the ion exchange temperature is 20 to 100°C, and the time is 2 to 48 hours.
[0011] Preferably, the polymer matrix includes polyimide, self-porous polymer (PIM-1), or polyether block amide (PEBAX).
[0012] Preferably, the mass of the anionic covalent organic framework is 5-20% of the total mass of the anionic covalent organic framework and the polymer matrix.
[0013] The present invention provides an anionic covalent organic framework mixed matrix membrane prepared by the preparation method described above, comprising a polymer matrix and an anionic covalent organic framework dispersed in the polymer matrix.
[0014] This invention provides the application of the anionic covalent organic framework hybrid matrix membrane described above in the field of gas separation, wherein the gas separation is CO2 / CH4 separation or CO2 / N2 separation.
[0015] This invention provides a method for preparing anionic covalent organic framework (COF) mixed matrix membranes. The method involves a post-modification process where an imine-type COF containing pyridine groups is reacted with a bromoalkane to obtain a bromine-modified COF. This COF is then reacted with an anionic salt via ion exchange to obtain an anionic COF. The anionic COF is then used as a filler and cast into a membrane with a polymer matrix. This invention utilizes the ionization of nitrogen (N) on the pyridine group through a quaternization reaction. Furthermore, the pyridine group has a structure similar to a benzene ring, readily forming a COF. This invention is the first to use anionic COF as a filler in a mixed matrix membrane. The ionic groups on its surface can generate stronger interactions with the polymer matrix (such as hydrogen bonding and ion-dipole interactions), significantly improving interfacial compatibility and filler dispersibility. Moreover, the structure can be adjusted by changing the side chain length and the type of exchanged anions, thereby controlling the gas separation performance.
[0016] The hybrid matrix membrane of this invention utilizes multiple non-covalent interactions, such as hydrogen bonds and ion-dipole interactions, between the anionic covalent organic framework and the polymer matrix, significantly improving the dispersibility and interfacial compatibility of the filler and effectively eliminating non-selective interfacial defects. This hybrid matrix membrane exhibits high permeability and high selectivity in CO2 / CH4 separation, exceeding the Robeson upper limit, and shows broad application prospects in natural gas purification, biogas refining, and flue gas carbon capture.
[0017] Compared with the prior art, the present invention has the following significant advantages: Excellent interfacial compatibility: Ionic sites in ionic covalent organic frameworks (iCOFs) (such as Br) - BF4 - It can form hydrogen bonds and ion-dipole interactions with C=O and -CF3 groups in the polymer matrix, effectively inhibiting filler agglomeration and eliminating interface defects.
[0018] Performance Breakthrough: By precisely controlling the side chain length and anion type of ionic covalent organic frameworks (iCOFs), the free volume and mass transfer pathway within the membrane were optimized, enabling the membrane's CO2 / CH4 separation performance to exceed the Robeson limit.
[0019] This invention can alter the adsorption capacity for CO2 by changing the type of anion, and can change the compatibility with polymers by changing the length of the carbon chain side chain. By controlling the separation performance through the side chain length and the type of anion, it provides theoretical guidance for the design of next-generation high-performance separation membranes.
[0020] This method is simple and easy to scale up. The solution casting method used is mature and reliable, easy to scale up production, and has broad prospects for industrial application. Attached Figure Description
[0021] Figure 1This is a schematic diagram of the preparation process of the anionic covalent organic framework in Example 1 of the present invention. Detailed Implementation
[0022] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.
[0023] This invention provides a method for preparing anionic covalent organic framework hybrid matrix membranes, comprising the following steps: A bromine-modified covalent organic framework is obtained by mixing an imine-type covalent organic framework containing a pyridine group, a bromoalkane, and an organic solvent. The bromine-modified covalent organic framework was mixed with an anionic salt compound and water, and ion exchange was performed to obtain an anionic covalent organic framework. The anionic covalent organic framework is mixed with a polymer matrix and a dispersion solvent to obtain a casting solution; After casting the casting solution into a film, it is dried to obtain an anionic covalent organic framework mixed matrix film.
[0024] In this invention, the monomers for preparing the pyridine-containing imine-type covalent organic framework preferably include aldehyde ligands and amino ligands; the aldehyde ligands preferably include one of pyromellitic pyrrolizaldehyde (A1), trialdehyde pyrogallol (A2), and 1,3,5-tris(p-formylphenyl)benzene (A3); the amino ligands preferably include one of 2,5-diaminopyridine (B1), 5'5-diamino-2'2-bipyridine (B2), and 4,4',4''-(pyridine-2,4,6-triyl)triphenylamine (B3), with the following specific structural formulas:
[0025] The present invention does not impose any particular limitation on the preparation method of the imine covalent organic framework (AB COF) containing pyridine groups, and it can be synthesized by the hot solvent method well known in the art.
[0026] In this invention, the preferred structural formula of the bromoalkane is C1. n Br, C n The alkyl group represents a straight-chain alkyl group with 2 to 20 carbon atoms, more preferably 8 to 12 carbon atoms, and even more preferably 5 to 10 carbon atoms; the bromoalkane is more preferably bromododecane or bromooctane.
[0027] In this invention, the organic solvent is preferably one or more of acetonitrile, ethyl acetate, toluene, ethanol, and methanol, more preferably acetonitrile or methanol. This invention does not impose a specific limit on the amount of the organic solvent used, as long as the materials are mixed evenly. When the organic solvent is two or more of the above-mentioned types, this invention does not impose a specific limit on the ratio of different types of organic solvents; any ratio is acceptable.
[0028] In this invention, the molar ratio of pyridine groups to bromoalkanes in the imine-type covalent organic framework is preferably 1:1 to 3, more preferably 1:2; the modification temperature is preferably 40 to 100°C, more preferably 60 to 80°C, and the modification time is preferably 10 to 48 hours, more preferably 20 to 24 hours.
[0029] After modification, the present invention preferably centrifuges, washes and dries the obtained product sequentially to obtain bromine-modified covalent organic frameworks (denoted as AB iCOFs), with the general formula AB-C n Br COF, where C n Represents straight-chain alkyl groups with 2 to 20 carbon atoms.
[0030] In this invention, the anion in the anionic salt compound preferably includes Cl. - ,Br - SiF6 - BF4 - PF6 - or NTf2 - The corresponding anionic salt compound is preferably NaCl, NaBr, NaSiF6, NaBF4, NaPF6, or LiNTf2.
[0031] In this invention, the molar ratio of pyridine groups to anionic salt compounds in the bromine-modified covalent organic framework is preferably 1:1 to 5, more preferably 1:2 to 3; the amount of water used in this invention is not particularly limited, and can be adjusted according to requirements to ensure uniform mixing of materials.
[0032] In this invention, the temperature of the ion exchange is preferably 20~100℃, more preferably 50~80℃, and the time is preferably 2~48h, more preferably 24~36h.
[0033] After the ion exchange is completed, the present invention preferably centrifuges the obtained product, collects the solid, washes it with water and ethanol, and dries it to obtain anionic covalent organic framework.
[0034] In this invention, the general formula for anionic covalent organic frameworks (AB-X iCOFs) is AB-C. n X COF, where X is Cl - ,Br - SiF6 - BF4 - PF6 - or NTf2 - .
[0035] In this invention, the polymer matrix preferably comprises polyimide, self-porous polymer (PIM-1), or polyether block amide (PEBAX), with the polyimide more preferably being 6FDA-DAM polyimide. This invention does not impose any particular limitation on the source of the polymer matrix; commercially available products well-known in the art are acceptable. In the embodiments of this invention, the matrix is specifically sourced from Zhengzhou Alpha Chemical Co., Ltd.
[0036] In this invention, the mass of the anionic covalent organic framework is 5-20% of the total mass of the anionic covalent organic framework and the polymer matrix, more preferably 10-15%.
[0037] In this invention, the dispersing solvent is preferably at least one of chloroform, dichloromethane, methanol, and ethanol. This invention does not have a special limitation on the amount of the dispersing solvent; it can be adjusted according to requirements to ensure uniform dispersion of the material.
[0038] This invention preferably involves dispersing anionic covalent organic frameworks in a dispersion solvent to obtain a filler dispersion, while simultaneously dispersing a polymer matrix in the same or different dispersion solvents to obtain a polymer solution. The polymer solution is then mixed with the filler dispersion in batches, followed by ultrasonication and stirring to obtain a casting solution. This casting solution is then cast into a petri dish, covered with a glass slide at room temperature for 12–48 hours to evaporate, and then dried in a vacuum oven at 50°C for 10 hours to obtain a mixed matrix membrane. This invention does not have a specific limitation on the number of batches; mixing can be performed uniformly according to procedures well-known in the art.
[0039] The present invention provides an anionic covalent organic framework mixed matrix membrane prepared by the preparation method described above, comprising a polymer matrix (continuous phase) and an anionic covalent organic framework (dispersed phase) dispersed in the polymer matrix.
[0040] This invention provides the application of the anionic covalent organic framework hybrid matrix membrane described above in the field of gas separation, wherein the gas separation is CO2 / CH4 separation or CO2 / N2 separation. This invention does not impose any particular limitation on the method of application; any method well-known in the art can be used.
[0041] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0042] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.
[0043] Example 1
[0044] like Figure 1 As shown, A2B3-C 12 Preparation of BF4 iCOF / 6FDA-DAM hybrid matrix membrane
[0045] 1) Take 0.1 mol of trialdehyde phloroglucinol (A2) and 0.1 mol of 4,4',4''-(pyridine-2,4,6-triyl)triphenylamine (B3) in a hydrothermal reactor, add 50 mL of dioxane and 50 mL of mesitylene, add 1 mL of acetic acid, and react at 120 °C for 24 h. Wash three times each with N,N-dimethylformamide, ethanol and water respectively to obtain A2B3 COF, the structural unit of which is shown below;
[0046] 2) A2B3 COF (containing 0.1 mol of pyridine groups) and 0.2 mol of bromododecane were refluxed in acetonitrile at 80°C for 24 h. After centrifugation, washing with ethanol, and drying at 80°C for 10 h, A2B3-C was obtained. 12 Br iCOF; 3) Combine A2B3-C 12 Br iCOF (containing 0.1 mol of pyridine groups) and 0.3 mol of NaBF4 were refluxed in deionized water at 80°C for 24 h for ion exchange. After the reaction, the solid was collected by centrifugation, washed with water and ethanol, and dried at 80°C for 10 h to obtain A2B3-C. 12 BF4 iCOF; 4) Take the above A2B3-C 12 BF4 iCOF (accounting for A2B3-C) 12 BF4 iCOF filler (10% of the total polymer mass) was dispersed in dichloromethane to obtain a filler dispersion. The filler dispersion was mixed with a chloroform solution (5 wt%) of 6FDA-DAM (Zhengzhou Alpha Chemical Co., Ltd.) accounting for 30% of the total volume. The mixture was ultrasonicated for 1 hour and stirred for 12 hours. The remaining 70% of the total volume of 6FDA-DAM solution was then added, and chloroform was added until the total volume remained unchanged. The mixture was ultrasonicated and stirred again to obtain a homogeneous casting solution. The casting solution was poured into an ultra-flat PTFE dish, covered with a glass slide at room temperature for 24 hours to evaporate, and then dried in a vacuum drying oven at 50°C for 10 hours to obtain a film containing 10 wt% A2B3-C. 12 BF4 iCOF hybrid matrix membrane.
[0047] According to the gas membrane separation standard (GB / T 40260-2021), the gas separation performance of the mixed matrix membrane was tested as follows: under the conditions of 0.5 MPa and 25℃, with the feed gas being CO2 / N2 in a volume ratio of 50 / 50, the membrane's CO2 permeability coefficient was 668.5 Barrer and its CO2 / N2 selectivity was 53.4.
[0048] Example 2
[0049] Preparation of A1B1-C8PF6 iCOF / PEBAX hybrid matrix membrane
[0050] 1) Take 0.1 mol of pyromellitic aldehyde (A1) and 0.15 mol of 2,5-diaminopyridine (B1) in a hydrothermal reactor, add 50 mL of dioxane and 50 mL of mesitylene, add 1 mL of acetic acid, and react at 120 °C for 24 h. Wash three times with N,N-dimethylformamide, ethanol and water respectively to obtain A1B1 COF, the structural unit of which is shown below;
[0051] 2) A1B1 COF (containing 0.1 mol of pyridine group) and 0.2 mol of bromooctane were refluxed in methanol at 60 °C for 20 h, centrifuged, washed with ethanol, and dried at 80 °C for 10 h to obtain A1B1-C8Br iCOF; 3) A1B1-C8Br iCOF (containing 0.1 mol of pyridine group) and 0.3 mol of NaPF6 were refluxed in deionized water at 100°C for 48 h to carry out ion exchange. After the reaction, the solid was collected by centrifugation, washed with water, and dried at 80°C for 10 h to obtain A1B1-C8PF6iCOF. 4) Take the above A1B1-C8PF6iCOF (accounting for 10% of the total mass of A1B1-C8PF6iCOF filler and polymer), disperse it in methanol to obtain a filler dispersion, mix the filler dispersion with 30% of the total amount of PEBAX (Zhengzhou Alpha Chemical Co., Ltd.) methanol solution (concentration 5 wt%), sonicate for 1 hour and stir for 12 hours, then add the remaining 70% of the total amount of PEBAX solution, add methanol until the total volume remains unchanged, sonicate and stir again to obtain a uniform casting solution; The casting solution was poured into an ultra-flat PTFE dish, covered with a glass slide at room temperature for 48 h to evaporate, and then dried in a vacuum drying oven at 50 °C for 10 h to obtain a mixed matrix membrane containing 10 wt% A1B1-C8PF6 iCOF.
[0052] According to the gas separation performance test of the gas membrane separation standard (GB / T 40260-2021): under the conditions of 0.5 MPa and 25℃, with the feed gas being CO2 / N2 and a volume ratio of 50 / 50, the permeability coefficient of the membrane for CO2 is 587.3 Barrer, and the selectivity of CO2 / N2 is 43.2.
[0053] Comparative Example 1
[0054] Take the A2B3 COF prepared in Example 1 (accounting for 10% of the total mass of A2B3 COF filler and polymer), disperse it in dichloromethane to obtain a filler dispersion. Mix the filler dispersion with a chloroform solution (concentration of 5 wt%) of 6FDA-DAM (Zhengzhou Alpha Chemical Co., Ltd.) accounting for 30% of the total volume. After sonication for 1 hour, stir for 12 hours. Then add the remaining 6FDA-DAM solution accounting for 70% of the total volume, and add chloroform until the total volume remains unchanged. Sonicate and stir again to obtain a uniform casting solution. The casting solution was poured into an ultra-flat PTFE dish, covered with a glass slide at room temperature for 24 hours to evaporate, and then dried in a vacuum drying oven at 50°C for 10 hours to obtain a mixed matrix membrane containing 10wt% A2B3 COF.
[0055] According to the gas membrane separation standard (GB / T 40260-2021), the gas separation performance of the mixed matrix membrane was tested as follows: under the conditions of 0.5 MPa and 25℃, with the feed gas being CO2 / N2 in a volume ratio of 50 / 50, the membrane's permeability coefficient for CO2 was 480.2 Barrer, and the CO2 / N2 selectivity was 21.4.
[0056] Comparative Example 2
[0057] Take A2B3-C prepared in Example 1 12 Br iCOF (accounting for A2B3-C) 12 Br iCOF filler (10% of the total mass of polymer) was dispersed in dichloromethane to obtain a filler dispersion. The filler dispersion was mixed with a chloroform solution (5 wt%) of 6FDA-DAM (Zhengzhou Alpha Chemical Co., Ltd.) accounting for 30% of the total volume. After sonication for 1 hour, the mixture was stirred for 12 hours. Then, the remaining 70% of the total volume of 6FDA-DAM solution was added, and chloroform was added until the total volume remained unchanged. The mixture was sonicated and stirred again to obtain a uniform casting solution. The casting solution was poured into an ultra-flat PTFE dish, covered with a glass slide at room temperature for 24 hours to evaporate, and then dried in a vacuum drying oven at 50°C for 10 hours to obtain a film containing 10 wt% A2B3-C. 12 Br iCOF hybrid matrix membrane.
[0058] According to the gas membrane separation standard (GB / T 40260-2021), the gas separation performance of the mixed matrix membrane was tested as follows: under the conditions of 0.5 MPa and 25℃, with the feed gas being CO2 / N2 in a volume ratio of 50 / 50, the membrane's CO2 permeability coefficient was 510.2 Barrer and the CO2 / N2 selectivity was 29.7.
[0059] Comparative Example 3
[0060] Take 10% of the total mass of A1B1 COF filler and polymer prepared in Example 2, disperse it in methanol to obtain a filler dispersion, mix the filler dispersion with a 5 wt% methanol solution of PEBAX (Zhengzhou Alpha Chemical Co., Ltd.), sonicate for 1 h and stir for 12 h, then add the remaining PEBAX solution, add methanol until the total volume remains unchanged, sonicate and stir again to obtain a uniform casting solution; The casting solution was poured into an ultra-flat PTFE dish, covered with a glass slide at room temperature for 48 h to evaporate, and then dried in a vacuum drying oven at 50 °C for 10 h to obtain a mixed matrix membrane containing 10 wt% A1B1 COF.
[0061] According to the gas separation performance test of the gas membrane separation standard (GB / T 40260-2021): under the conditions of 0.5 MPa and 25℃, with the feed gas being CO2 / N2 and a volume ratio of 50 / 50, the permeability coefficient of the membrane for CO2 is 347.3 Barrer, and the selectivity of CO2 / N2 is 17.8.
[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made 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.
Claims
1. A method for preparing an anionic covalent organic framework hybrid matrix membrane, characterized in that, Includes the following steps: A bromine-modified covalent organic framework is obtained by mixing an imine-type covalent organic framework containing a pyridine group, a bromoalkane, and an organic solvent. The bromine-modified covalent organic framework was mixed with an anionic salt compound and water, and ion exchange was performed to obtain an anionic covalent organic framework. The anionic covalent organic framework is mixed with a polymer matrix and a dispersion solvent to obtain a casting solution; After casting the casting solution into a film, it is dried to obtain an anionic covalent organic framework mixed matrix film.
2. The preparation method according to claim 1, characterized in that, The monomers for preparing the imine-type covalent organic framework include aldehyde ligands and amino ligands; The aldehyde ligand includes one of pyromellitic methyl ether, trialdehyde phloroglucinol, and 1,3,5-tris(p-formylphenyl)benzene; The amino ligand includes one of 2,5-diaminopyridine, 5'5-diamino-2'2-bipyridine, and 4,4',4''-(pyridine-2,4,6-triyl)triphenylamine.
3. The preparation method according to claim 1, characterized in that, The general structural formula of the bromoalkane is C. n Br, C n Represents straight-chain alkyl groups with 2 to 20 carbon atoms.
4. The preparation method according to claim 1 or 3, characterized in that, The molar ratio of pyridine groups to bromoalkanes in the imine-type covalent organic framework is 1:1~3; the modification temperature is 40~100℃ and the time is 10~48h.
5. The preparation method according to claim 1, characterized in that, The anion in the anionic salt compound includes Cl-. - ,Br - SiF6 - BF4 - PF6 - or NTf2 - .
6. The preparation method according to claim 1 or 5, characterized in that, The molar ratio of pyridine groups to anionic salt compounds in the bromine-modified covalent organic framework is 1:1 to 5; the ion exchange temperature is 20 to 100 °C, and the time is 2 to 48 h.
7. The preparation method according to claim 1, characterized in that, The polymer matrix includes polyimide, microporous polymer, or polyether block amide.
8. The preparation method according to claim 1 or 7, characterized in that, The mass of the anionic covalent organic framework is 5-20% of the total mass of the anionic covalent organic framework and the polymer matrix.
9. The anionic covalent organic framework hybrid matrix membrane prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It includes a polymer matrix and an anionic covalent organic framework dispersed in the polymer matrix.
10. The application of the anionic covalent organic framework hybrid matrix membrane of claim 9 in the field of gas separation, characterized in that, The gas separation is either CO2 / CH4 separation or CO2 / N2 separation.