CO2 Separation Mixed Matrix Composite Membrane and Its Preparation Method

Abstract

This invention relates to the field of gas separation membrane material preparation, and discloses a CO2 separation mixed matrix composite membrane and its preparation method. The method includes: mixing an amino-containing MOF, a bridging ligand, a first solvent, and an optional first catalyst and carrying out a first reaction; separating a solid product from the first reaction product to obtain a pre-modified solid; mixing the pre-modified solid, a portion of an amino polymer, a second solvent, and an optional second catalyst and carrying out a second reaction; separating a solid product from the second reaction product to obtain a modified MOF; mixing the modified MOF with water to obtain a mixture; then mixing the mixture with another portion of an amino polymer and coating it onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer. The CO2 separation mixed matrix membrane exhibits significant wetting between particles and the amino polymer, without generating interfacial defects, and has a high MOF loading, resulting in excellent carbon dioxide separation performance.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane material preparation, specifically to a CO2 separation mixed matrix composite membrane and its preparation method. Background Technology

[0002] Developing energy-efficient, high-efficiency, and environmentally friendly carbon dioxide separation technologies is crucial for improving the overall economic benefits of carbon capture, utilization, and storage (CCUS) processes. Membrane separation, as a next-generation carbon capture technology, is widely recognized for its potential to significantly reduce carbon capture costs and energy consumption due to its ease of integration, operational flexibility, and low ecological footprint. However, existing commercial polymer membranes are constrained by the trade-off between permeability and selectivity, preventing the achievement of highly efficient and low-energy separation.

[0003] Hybrid matrix membranes (MMMs) are a rapidly developing type of separation membrane, proven to effectively combine the advantages of nanofillers and polymers, breaking through the performance limits of traditional polymer membranes. However, further research needs to focus on the core characteristic of the interaction between nanofillers and polymers. One of the key structural features of this type of membrane is the existence of a specific phase interface between the nanoporous material and the polymer matrix; mismatched interactions between the two components can lead to abnormal degradation of membrane performance. Metal-organic frameworks (MOFs) have many precedents in membrane separation; however, the rigidity and high crystallinity of MOFs make them prone to forming interfacial defects with the polymer matrix in hybrid matrix membranes. Therefore, further modification of MOFs is needed to make them suitable as fillers for CO2 separation hybrid matrix membranes, while ensuring that the filler exists in sufficient quantity and stably within the polymer matrix.

[0004] Numerous efforts have been made to reduce interfacial defects. Post-modification of nanofillers (mainly MOFs or COFs with active reactive sites) by introducing a third component to modulate the binary interface has proven feasible. Among these methods, grafting polymers homologous to the matrix onto the nanofillers using crosslinking agents is a convenient and representative modification approach. Therefore, exploring a universal method for preparing amine polymer-modified MOF materials using different bridging ligands is a key issue that requires further research. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of interface defects easily generated when MOF fillers are added to the existing mixed matrix membranes and the MOF loading is small. This invention provides a CO2 separation mixed matrix composite membrane and its preparation method. By changing the structure of the bridging molecules, this method can obtain amine polymer modified MOF materials with different interfacial compatibility. It can expand the range of interfacial compatibility between amine polymer modified MOF and amine polymer matrix and be used to prepare high-performance CO2 separation mixed matrix membranes.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a CO2 separation mixed matrix composite membrane, the method comprising the following steps:

[0007] (1) A MOF containing an amino group, a bridging ligand, a first solvent and an optional first catalyst are mixed and subjected to a first reaction. A solid product is separated from the product of the first reaction to obtain a pre-modified solid.

[0008] (2) The pre-modified solid obtained in step (1), a portion of the amine polymer, the second solvent and the optional second catalyst are mixed to carry out a second reaction, and the solid product is separated from the product of the second reaction to obtain the modified MOF;

[0009] (3) The modified MOF obtained in step (2) is mixed with another part of the amine polymer and coated onto the polysulfone ultrafiltration membrane containing the silicone rubber interlayer to obtain a CO2 separation mixed matrix composite membrane.

[0010] Preferably, in step (1), the MOF is selected from at least one of the UIO series MOF, the MIL series MOF and the ZIF series MOF.

[0011] Preferably, the MOF is selected from at least one of UIO-66-NH2, CAU-1(Al)-NH2, MIL-53(Al)-NH2, MIL-101(Cr)-NH2, MIL-68(In)-NH2, MIL-101(Fe)-NH2, MIL-101(Al)-NH2, MIL-125(Ti)-NH2 and ZIF-8-NH2.

[0012] Preferably, in step (1), the bridging ligand is selected from at least one of diepoxy molecules, dicarboxylic acid molecules, and dialdehyde molecules.

[0013] Preferably, the bridging ligand is selected from at least one of diepoxybutane, polyethylene glycol diglycidyl ether, oxalic acid, malonic acid, succinic acid, glutaric acid, glyoxal, terephthalaldehyde, glutaraldehyde, and 4,4-biphenyldialdehyde.

[0014] Preferably, in step (1), the molar ratio of the amino group in the MOF to the bridging ligand is 1:2-5.

[0015] Preferably, in step (1), the first solvent is a polar solvent and / or a polar solvent.

[0016] Preferably, the first solvent is selected from at least one of water, ethanol, dimethylformamide, and tetrahydrofuran.

[0017] Preferably, the first catalyst is selected from at least one of acetic acid, formic acid, and propionic acid.

[0018] Preferably, the weight ratio of the first catalyst to the first solvent is 0.01-0.5:100.

[0019] Preferably, in step (1), the conditions for the first reaction include: a reaction temperature of 40-80°C and a reaction time of 1-6 hours.

[0020] Preferably, in steps (2) and (3), the amine polymer is a branched and / or linear amine polymer.

[0021] Preferably, the amine polymer is selected from at least one of polyethyleneamine, polyethyleneimine, and polyacrylamine.

[0022] Preferably, in step (2), the weight ratio of the pre-modified solid to the portion of the amine polymer is 1-3:1.

[0023] Preferably, in step (2), the second solvent is an aqueous solution of ethanol.

[0024] Preferably, the concentration of the ethanol aqueous solution is 30-80 wt%.

[0025] Preferably, the second catalyst is selected from at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, and triethylamine.

[0026] Preferably, the weight ratio of the second catalyst to the second solvent is 0.01-0.8:100.

[0027] Preferably, in step (2), the reaction conditions are: reaction temperature of 30-60℃ and reaction time of 0.5-4h.

[0028] Preferably, in step (3), the weight ratio of the modified MOF to the other part of the amine polymer is 30-60:100.

[0029] The second aspect of the present invention discloses a CO2 separation mixed matrix composite membrane prepared by the method described above.

[0030] The method for preparing the CO2 separation mixed matrix composite membrane of the present invention uses a bridging ligand with a group that can react with -NH2 to connect an amine-containing MOF and an amine polymer. By changing the structure of the bridging ligand, amine polymer-modified MOF materials with different interfacial compatibility can be obtained, thereby expanding the range of interfacial compatibility between the amine polymer-modified MOF and the amine polymer matrix and using it to prepare a high-performance CO2 separation mixed matrix membrane. The method is simple to operate, low in cost, highly reproducible, and has good application prospects.

[0031] The CO2 separation mixed matrix membrane of the present invention has smooth particle surface morphology, uniform phase interface, no interface defects, and high MOF loading. Therefore, the CO2 separation mixed matrix membrane has excellent carbon dioxide separation performance, with a CO2 permeation rate >1491 and a CO2 / N2 selectivity >134. Attached Figure Description

[0032] Figure 1 These are atomic force microscopy images of the CO2 separation mixed matrix composite membranes prepared in Examples 1-3 and Comparative Example 1. Detailed Implementation

[0033] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] The preparation method of the CO2 separation mixed matrix composite membrane of the present invention includes the following steps:

[0036] (1) A MOF containing an amino group, a bridging ligand, a first solvent and an optional first catalyst are mixed and subjected to a first reaction. A solid product is separated from the product of the first reaction to obtain a pre-modified solid.

[0037] (2) The pre-modified solid obtained in step (1), a portion of the amine polymer, the second solvent and the optional second catalyst are mixed to carry out a second reaction, and the solid product is separated from the product of the second reaction to obtain the modified MOF;

[0038] (3) The modified MOF obtained in step (2) is mixed with another part of the amine polymer and coated onto the polysulfone ultrafiltration membrane containing the silicone rubber interlayer to obtain a CO2 separation mixed matrix composite membrane.

[0039] In this invention, in step (1), the MOF can be at least one of UIO series MOF, MIL series MOF and ZIF series MOF.

[0040] In a preferred embodiment, the MOF is at least one selected from UIO-66-NH2, CAU-1(Al)-NH2, MIL-53(Al)-NH2, MIL-101(Cr)-NH2, MIL-68(In)-NH2, MIL-101(Fe)-NH2, MIL-101(Al)-NH2, MIL-125(Ti)-NH2, and ZIF-8-NH2, with UIO-66-NH2 being the most preferred. In these preferred embodiments, when the MOF is one of the above types, the prepared modified MOF exhibits better interfacial compatibility in the CO2 separation mixed matrix composite membrane.

[0041] In this invention, in step (1), the bridging ligand can be at least one of a diepoxy molecule, a dicarboxylic acid molecule, and a dialdehyde molecule, preferably a diepoxy molecule. In this invention, when the bridging ligand is of the above-mentioned type (especially the preferred type), the prepared modified MOF exhibits excellent interfacial compatibility in the CO2 separation mixed matrix composite membrane.

[0042] In a preferred embodiment, the bridging ligand is at least one selected from the group consisting of diepoxybutane, polyethylene glycol diglycidyl ether, oxalic acid, malonic acid, succinic acid, glutaric acid, glyoxal, terephthalaldehyde, glutaraldehyde, and 4,4-biphenyldialdehyde, with diepoxybutane being the most preferred. In these preferred embodiments, when the bridging ligand is one of the above-mentioned types, the prepared modified MOF exhibits better interfacial compatibility in the CO2 separation mixed matrix composite membrane.

[0043] In the method described in this invention, in step (1), the molar ratio of the amino group in the MOF to the bridging ligand can be 1:2-5, preferably 1:2-3. In these embodiments, when the molar ratio of the amino group in the MOF to the bridging ligand is within the above range (especially the preferred range), the prepared CO2 separation mixed matrix composite membrane has better carbon dioxide selectivity.

[0044] In this invention, in step (1), the first solvent can be a polar solvent and / or a polar solvent. In a more preferred embodiment, the first solvent is at least one of water, ethanol, dimethylformamide, and tetrahydrofuran. In this invention, when the first solvent is one of the above-mentioned types (especially the preferred types), the MOF in the prepared pre-modified solid exhibits higher reactivity and grafting rate with the bridging ligand.

[0045] In this invention, the first catalyst can be at least one of acetic acid, formic acid, and propionic acid, preferably acetic acid. In this invention, when the first catalyst is one of the above-mentioned types (especially the preferred types), the MOF in the prepared pre-modified solid exhibits higher reactivity and grafting rate with the bridging ligand.

[0046] In the method described in this invention, the weight ratio of the first catalyst to the first solvent can be 0.01-0.5:100, preferably 0.1-0.5:100. In the method described in this invention, when the weight ratio of the first catalyst to the first solvent is within the above range (especially the preferred range), the pre-modified solid obtained exhibits higher reactivity and grafting rate between the MOF and the bridging ligand.

[0047] In the method described in this invention, in step (1), the conditions for the first reaction may include: a reaction temperature of 40-80°C, preferably 50-80°C; and a reaction time of 1-6 h, preferably 3-6 h. In the method described in this invention, when the conditions for the first reaction are within the above range (especially the preferred range), the MOF and the bridging ligand in the prepared pre-modified solid exhibit higher reactivity and grafting rate.

[0048] In some embodiments, the process of preparing the pre-modified solid may include: dispersing an amino-containing MOF and a bridging ligand in a first solvent, adding a first catalyst and reacting at 40-80°C for 1-6 hours, filtering the obtained reaction product and washing it with ethanol until no obvious impurities are found, removing most of the ethanol to obtain the pre-modified solid, wherein the molar ratio of the amino-containing MOF to the bridging ligand, based on the number of amino groups, is 1:2-5, and the weight ratio of the first catalyst to the first solvent is 0.01-0.5:100. When step (1) is performed according to this embodiment, the prepared CO2 separation mixed matrix composite membrane has better carbon dioxide selectivity.

[0049] In this invention, in steps (2) and (3), the amine polymer can be a branched and / or linear amine polymer. In a preferred embodiment, the amine polymer is selected from at least one of polyethyleneamine, polyethyleneimine, and polyacrylamine, preferably polyethyleneamine. In this invention, when the amine polymer is of the above-mentioned type (especially the preferred type), the prepared CO2 separation mixed matrix composite membrane has better carbon dioxide selectivity.

[0050] In the method described in this invention, in step (2), the weight ratio of the pre-modified solid to the portion of the amine polymer can be 1-3:1, preferably 1-2:1. In these embodiments, when the weight ratio of the pre-modified solid to the portion of the amine polymer is within the above range (especially the preferred range), the bridging ligand has higher reactivity and grafting rate with the amine polymer.

[0051] In this invention, in step (2), the second solvent is an aqueous ethanol solution. In a preferred embodiment, the concentration of the aqueous ethanol solution is 30-80 vol%. In this invention, when the second solvent is of the above-mentioned type (especially the preferred type), the reactivity and grafting rate of the bridging ligand with the amine polymer are higher.

[0052] In this invention, the second catalyst can be at least one selected from sodium carbonate, sodium bicarbonate, sodium hydroxide, and triethylamine, preferably sodium carbonate. In this invention, when the second catalyst is one of the above-mentioned types (especially the preferred types), the bridging ligand exhibits higher reactivity and grafting rate with the amine polymer.

[0053] In the method described in this invention, the weight ratio of the second catalyst to the second solvent can be 0.01-0.8:100, preferably 0.1-0.2:100. In these embodiments, when the weight ratio of the second catalyst to the second solvent is within the above range (especially the preferred range), the reactivity and grafting rate of the bridging ligand with the amine polymer are higher.

[0054] In the method described in this invention, in step (2), the reaction conditions can be: a reaction temperature of 30-60°C, preferably 40-60°C; and a reaction time of 0.5-4 h, preferably 2-4 h. In these embodiments, when the reaction conditions are within the above ranges (especially the preferred ranges), the bridging ligand exhibits higher reactivity and grafting rate with the amine polymer.

[0055] In some embodiments, the conditions for preparing the modified MOF may include: mixing the pre-modified solid with a portion of the amine polymer in a second solvent, adding a second catalyst, reacting at 30-60°C for 0.5-4 h, centrifuging the obtained reaction product and separating the solid product, washing the solid product with deionized water and ethanol, and vacuum drying at 60-90°C for 4-10 h to obtain the modified MOF. The weight ratio of the pre-modified solid to the portion of the amine polymer is 1-3:1, and the weight ratio of the second catalyst to the second solvent is 0.01-0.8:100. When step (2) is performed according to this embodiment, the prepared CO2 separation mixed matrix composite membrane exhibits better carbon dioxide selectivity.

[0056] In the method described in this invention, in step (3), the weight ratio of the modified MOF to the other portion of the amine polymer can be 30-60:100, preferably 30-50:100. In these embodiments, when the weight ratio of the modified MOF to the other portion of the amine polymer is within the above range (especially the preferred range), the prepared CO2 separation mixed matrix composite membrane has better carbon dioxide selectivity.

[0057] In some embodiments, the process of preparing the CO2 separation mixed matrix composite membrane may include: ultrasonically dispersing the modified MOF in deionized water, then blending the modified MOF dispersion with another portion of the amine polymer to obtain a mixture, wherein the weight ratio of the modified MOF to the other portion of the amine polymer is 30-60:100; coating the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer; and naturally drying at room temperature for 4-10 hours to obtain the CO2 separation mixed matrix composite membrane. When step (3) is performed according to this embodiment, the prepared CO2 separation mixed matrix composite membrane has better carbon dioxide selectivity.

[0058] In the CO2 separation mixed matrix composite membrane of the present invention, the modified MOF and the amine polymer matrix have excellent interfacial compatibility, and the interfacial compatibility range between the amine polymer modified MOF and the amine polymer matrix can be expanded by changing the bridging ligand structure, and can be used to prepare high-performance CO2 separation mixed matrix membranes. The particles in the CO2 separation mixed matrix membrane of the present invention have smooth surface morphology, uniform phase interface, no interfacial defects, and high MOF loading. Therefore, the CO2 separation mixed matrix membrane has excellent carbon dioxide separation performance, with a CO2 permeation rate > 1491 and a CO2 / N2 selectivity > 134.

[0059] The following examples further illustrate the CO2 separation mixed matrix composite membrane and its preparation method according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0060] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples and comparative examples are commercially available.

[0061] Example 1

[0062] (1) 1 g of UIO-66-NH2 and 0.9087 g of diepoxide (the molar ratio of UIO-66-NH2 to diepoxide based on the number of amino groups was 1:3) were dispersed in 40 mL of ethanol, and 0.064 g of acetic acid (0.2 wt%) was added as a catalyst. The reaction was carried out at 50 °C for 4 h. The resulting reaction product was filtered and washed with ethanol until no obvious impurities were found. Most of the ethanol was removed by vacuum filtration to obtain the pre-modified solid.

[0063] (2) Mix 1g of the pre-modified solid obtained in step (1) with 2g of polyethyleneamine in 40mL of an aqueous ethanol solution containing 70 vol% ethanol, and then add 0.034g of sodium carbonate (0.1wt%) as a catalyst. React the resulting reaction system at 50°C for 2h. Then centrifuge the obtained reaction product and separate the solid product. Wash the solid product with deionized water and ethanol, and vacuum dry it at 80°C for 6h to obtain the modified MOF.

[0064] (3) Disperse 1g of the modified MOF obtained in step (2) in 10mL of deionized water by ultrasonication, and then mix the modified MOF dispersion with 2.25g of polyethyleneamine to obtain a mixture (the weight ratio of the modified MOF to the polyethyleneamine is 44.44:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0065] Example 2

[0066] (1) 1 g of UIO-66-NH2 and 2.1853 g of malonic acid (the molar ratio of UIO-66-NH2 to malonic acid, based on the number of amino groups, was 1:5) were dispersed in 40 mL of dimethylformamide. 0.07584 g of acetic acid (0.2 wt%) was added as a catalyst, and the reaction was carried out at 80 °C for 6 h. The resulting reaction product was filtered and washed with ethanol until no obvious impurities were found. Most of the ethanol was removed by vacuum filtration to obtain a pre-modified solid.

[0067] (2) Mix 1g of the pre-modified solid obtained in step (1) with 2g of polyethyleneimine in 40mL of an ethanol aqueous solution containing 50vol% ethanol, and then add 0.1074g of sodium bicarbonate (0.3wt%) as a catalyst. React the resulting reaction system at 60℃ for 4h. Centrifuge the obtained reaction product and separate the solid product. Wash the solid product with deionized water and ethanol, and vacuum dry it at 80℃ for 6h to obtain the modified MOF.

[0068] (3) Disperse 1g of the modified MOF obtained in step (2) in 10mL of deionized water by ultrasonication, and then mix the modified MOF dispersion with 2.67g of polyethyleneamine to obtain a mixture (the weight ratio of the modified MOF to the polyethyleneamine is 37.5:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0069] Example 3

[0070] (1) 1 g of UIO-66-NH2 and 0.840 g of glutaraldehyde (the molar ratio of UIO-66-NH2 to glutaraldehyde based on the number of amino groups was 1:2) were dispersed in 40 mL of tetrahydrofuran, and 0.3556 g of formic acid (0.1 wt%) was added as a catalyst. The reaction was carried out at 60 °C for 3 h. The resulting reaction product was filtered and washed with ethanol until no obvious impurities were found. Most of the ethanol was removed by vacuum filtration to obtain the pre-modified solid.

[0071] (2) Mix 1g of the pre-modified solid obtained in step (1) with 3g of polyacrylamide in 40mL of an ethanol aqueous solution with an ethanol concentration of 30vol%, and add 0.0366g of sodium hydroxide (0.1wt%) as a catalyst. React the resulting reaction system at 40℃ for 3 h. Centrifuge the obtained reaction product and separate the solid product. Wash the solid product with deionized water and ethanol, and vacuum dry it at 80℃ for 6 h to obtain the modified MOF.

[0072] (3) Disperse 1g of the modified MOF obtained in step (2) in 10mL of deionized water by ultrasonication, and then mix the modified MOF dispersion with 2.43g of polyethyleneimine to obtain a mixture (the weight ratio of the modified MOF to the polyethyleneimine is 41.18:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0073] Example 4

[0074] (1) Disperse 1g of MIL-53(Al)-NH2 and 3.75g of polyethylene glycol diglycidyl ether (Mw-600g / mol) in 40mL of water (the molar ratio of NH2-MIL-53(Al) based on the number of amino groups to the amount of polyethylene glycol diglycidyl ether is 1:1.5), react at 40℃ for 1h, filter the obtained reaction product and wash it with ethanol until there are no obvious impurities, remove most of the ethanol by vacuum filtration to obtain the pre-modified solid;

[0075] (2) Mix 1g of the pre-modified solid obtained in step (1) with 1g of polyethyleneamine in 40mL of an aqueous ethanol solution containing 60vol% ethanol. React the resulting reaction system at 60℃ for 0.5h. Centrifuge the resulting reaction product and separate the solid product. Wash the solid product with deionized water and ethanol and vacuum dry it at 80℃ for 6h to obtain the modified MOF.

[0076] (3) Disperse 1g of the modified MOF obtained in step (2) in 10mL of deionized water by ultrasonication, and then mix the modified MOF dispersion with 2.25g of polyethyleneimine to obtain a mixture (the weight ratio of the modified MOF to the polyethyleneimine is 44.44:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0077] Example 5

[0078] (1) 1g of MIL-101(Cr)-NH2 and 0.79g of terephthalaldehyde (the molar ratio of MIL-101(Cr)-NH2 to terephthalaldehyde based on the number of amino groups is 1:2.5) were dispersed in 40mL of ethanol, and 0.16g of propionic acid (0.5wt%) was added as a catalyst. The reaction was carried out at 70℃ for 5h. The reaction product was filtered and washed with ethanol until there were no obvious impurities. Most of the ethanol was removed by vacuum filtration to obtain the pre-modified solid.

[0079] (2) Mix 1g of the pre-modified solid obtained in step (2) with 1g of polyacrylamide in 40mL of an aqueous ethanol solution containing 75 vol% ethanol, and then add 0.2736g of sodium carbonate (0.8wt%) as a catalyst. React the resulting reaction system at 50°C for 2h. Centrifuge the obtained reaction product and separate the solid product. Wash the solid product with deionized water and ethanol, and vacuum dry it at 80°C for 6h to obtain the modified MOF.

[0080] (4) Disperse 1g of the modified MOF obtained in step (3) in 10mL of deionized water by ultrasonication, and then mix the modified MOF dispersion with 3g of polyacrylamide to obtain a mixture (the weight ratio of the modified MOF to the polyacrylamide is 33.33:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0081] Comparative Example 1

[0082] 1g of UIO-66-NH2 was ultrasonically dispersed in 10mL of deionized water. The UIO-66-NH2 dispersion was then mixed with 6g of polyvinylamine to obtain a mixture (the weight ratio of UIO-66-NH2 to polyvinylamine was 16.67:100). The mixture was coated onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer and allowed to dry naturally at room temperature for 6 hours to obtain a CO2 separation mixed matrix composite membrane.

[0083] Comparative Example 2

[0084] (1) Mix 1g of UIO-66-NH2 and 2g of polyethyleneimine in 40mL of ethanol aqueous solution with a concentration of 50vol% ethanol. React the resulting reaction system at 60℃ for 4h. Centrifuge the obtained reaction product and separate the solid product. Wash the solid product with deionized water and ethanol, and vacuum dry at 80℃ for 6h to obtain the modified MOF.

[0085] (2) Disperse 1g of the modified MOF obtained in step (1) in 10mL of deionized water by ultrasonication, and then mix the modified MOF dispersion with 4.33g of polyethyleneamine to obtain a mixture (the weight ratio of the modified MOF to the polyethyleneamine is 23.08:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0086] Comparative Example 3

[0087] (1) 1g of UIO-66-NH2 and 0.9751g of glyoxal (the molar ratio of UIO-66-NH2 to glyoxal based on the number of amino groups is 1:4) were dispersed in 40mL of ethanol, and 0.128g of acetic acid (0.4wt%) was added as a catalyst. The reaction was carried out at 70℃ for 1h. The resulting reaction product was filtered and washed with ethanol until there were no obvious impurities. Most of the ethanol was removed by vacuum filtration to obtain the pre-modified solid.

[0088] (2) Disperse 1g of the premodified solid obtained in step (1) in 10mL of deionized water, and then mix the premodified solid dispersion with 6g of polyethyleneamine to obtain a mixture (the weight ratio of the premodified solid to the polyethyleneamine is 16.67:100). Coat the mixture onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer, and allow it to dry naturally at room temperature for 6h to obtain a CO2 separation mixed matrix composite membrane.

[0089] Comparative Example 4

[0090] 1g of MIL-53(Al)-NH2 was ultrasonically dispersed in 10mL of deionized water. The MIL-53(Al)-NH2 dispersion was then mixed with 11g of polyethyleneamine to obtain a mixture (the weight ratio of MIL-53(Al)-NH2 to polyethyleneamine was 9.09:100). The mixture was coated onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer and allowed to dry naturally at room temperature for 6 hours to obtain a CO2 separation mixed matrix composite membrane.

[0091] Comparative Example 5

[0092] 1g of MIL-101(Cr)-NH2 was ultrasonically dispersed in 10mL of deionized water. The MIL-101(Cr)-NH2 dispersion was then mixed with 16g of polyethyleneamine to obtain a mixture (the weight ratio of MIL-101(Cr)-NH2 to polyethyleneamine was 6.25:100). The mixture was then coated onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer and allowed to dry naturally at room temperature for 6 hours to obtain a CO2 separation mixed matrix composite membrane.

[0093] Comparative Example 6

[0094] This embodiment is implemented according to the method described in Example 2. The difference is that in step (3), 1g of the modified MOF obtained in step (2) is ultrasonically dispersed in 10mL of deionized water. The modified MOF dispersion is scraped onto a polysulfone ultrafiltration membrane containing a silicone rubber interlayer. After natural drying at room temperature for 6h, a CO2 separation mixed matrix composite membrane is obtained.

[0095] Test Example 1

[0096] In this test example, atomic force microscopy was used to characterize the morphology and structure of the CO2 separation mixed matrix composite membranes prepared in Examples 1-3 and Comparative Example 1. The results are as follows: Figure 1 As shown.

[0097] Depend on Figure 1As can be seen, compared with Comparative Example 1, by adopting the technical solution described in this invention, the MOF material modified by bridging ligands and amine polymers in the CO2 separation mixed matrix composite membranes prepared in Examples 1-3 have better compatibility with the matrix, thereby increasing its loading in the CO2 separation mixed matrix composite membrane; at the same time, after the MOF raw material is modified, the particle surface and amine polymer in the prepared CO2 separation mixed matrix composite membrane have a significant wetting effect, the phase interface is more uniform, and it shows excellent interfacial compatibility.

[0098] Test Example 2

[0099] In this test example, the specific surface area and pore size distribution of the modified MOF materials prepared in Examples 1-5 and Comparative Examples 1-6 were measured using a specific surface area and pore size analyzer to verify the influence of the modification method on the intrinsic properties of the materials. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102] As shown in Table 1, compared with the MOF raw materials, the specific surface area and pore size of the modified MOFs prepared in Examples 1-5 decreased slightly. The extent of this decrease was related to the characteristics of the bridging ligands. This is because the different flexibility of the bridging ligands led to differences in the aggregation state of the grafted polymers on the nanofiller surface. Strongly electropositive amine polymers tended to aggregate around the strongly negatively charged ligands in the modified MOF, rather than uniformly covering the particle surface, thus avoiding polymer pore permeation. This is beneficial for constructing high-performance CO2 separation mixed matrix membranes. Compared with Comparative Example 1, the MOF in Comparative Example 2 uniformly and reversibly adsorbed a large amount of amine polymers on its surface through hydrogen bonding, resulting in a significant decrease in specific surface area and pore size, but the improvement in compatibility with the amine polymers was relatively small. The MOF in Comparative Example 3 was only modified with small-molecule bridging ligands, which had little effect on its specific surface area and pore size, but the MOF was not modified with amine polymers, resulting in no significant improvement in compatibility. The two examples above show that steps (1) and (2) play important roles in maintaining the MOF pore structure and improving the interfacial compatibility between MOF and amine polymer, and neither can be omitted.

[0103] Test Example 3

[0104] This test example illustrates the CO2 separation performance of the CO2 separation mixed matrix composite membranes prepared in Examples 1-5 and Comparative Examples 1-6. The test example includes the following steps:

[0105] The CO2 separation mixed matrix composite membranes prepared in Examples 1-5 and Comparative Examples 1-6 were tested in a CO2 / N2 mixed gas system (CO2 to N2 volume ratio 15:85), with the feed gas pressure set at 0.20 MPa and the test temperature at 25 °C. The composition of the permeate gas was analyzed by gas chromatography calibrated using the external standard method, and the CO2 permeability and separation factor of the separation membrane were calculated. The results are shown in Table 2.

[0106] Table 2

[0107]

[0108] As shown in Table 2, compared to Comparative Examples 1-6, the CO2 separation mixed matrix composite membranes prepared in Examples 1-5 exhibit significantly improved CO2 permeability and CO2 / N2 separation factor, with CO2 permeability exceeding 1491 and CO2 / N2 separation factor exceeding 134, demonstrating superior carbon dioxide selectivity compared to existing technologies. Comparative Examples 1-5 show lower CO2 permeability and CO2 / N2 separation factor than the CO2 separation mixed matrix composite membranes prepared in Examples 1-5 due to less improved compatibility between the MOF and the amine polymer. Furthermore, Comparative Example 6, lacking the addition of an amine polymer during the preparation of its CO2 separation mixed matrix composite membrane, cannot form a uniform and defect-free separation layer and therefore does not exhibit significant CO2 separation performance.

[0109] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a CO2 separation mixed matrix composite membrane, characterized in that, The method includes the following steps: (1) Mix an amino-containing MOF, a bridging ligand, a first solvent and a first catalyst and carry out a first reaction, and separate a solid product from the first reaction product to obtain a pre-modified solid; (2) The pre-modified solid obtained in step (1), a portion of the amine polymer, the second solvent and the second catalyst are mixed to carry out a second reaction, and the solid product is separated from the product of the second reaction to obtain the modified MOF; (3) The modified MOF obtained in step (2) is mixed with another part of the amine polymer and coated onto the polysulfone ultrafiltration membrane containing the silicone rubber interlayer to obtain a CO2 separation mixed matrix composite membrane; The bridging ligand is selected from at least one of diepoxybutane, oxalic acid, malonic acid, succinic acid, glutaric acid, glyoxal, terephthalaldehyde, glutaraldehyde, and 4,4-biphenyldialdehyde. The first catalyst is selected from at least one of acetic acid, formic acid, and propionic acid; The weight ratio of the first catalyst to the first solvent is 0.01-0.5:100; The conditions for the first reaction include: a reaction temperature of 40-80℃ and a reaction time of 1-6h; The amine polymer is selected from polyethyleneimine and / or polyacrylamide; The second catalyst is selected from at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, and triethylamine; The molar ratio of the amino group in the MOF to the bridging ligand is 1:2-5; The weight ratio of the second catalyst to the second solvent is 0.01-0.8:100; The weight ratio of the pre-modified solid to the portion of the amine polymer is 1-3:1; In step (2), the reaction conditions are: reaction temperature of 30-60℃ and reaction time of 0.5-4h; The weight ratio of the modified MOF to the other portion of the amine polymer is 30-60:

100.

2. The method according to claim 1, characterized in that, In step (1), the MOF is selected from at least one of the UIO series MOF, the MIL series MOF and the ZIF series MOF.

3. The method according to claim 1 or 2, characterized in that, The MOF is selected from at least one of UIO-66-NH2, CAU-1(Al)-NH2, MIL-53(Al)-NH2, MIL-101(Cr)-NH2, MIL-68(In)-NH2, MIL-101(Fe)-NH2, MIL-101(Al)-NH2, MIL-125(Ti)-NH2 and ZIF-8-NH2.

4. The method according to claim 1, characterized in that, In step (1), the first solvent is a polar solvent.

5. The method according to claim 1 or 4, characterized in that, The first solvent is selected from at least one of water, ethanol, dimethylformamide, and tetrahydrofuran.

6. The method according to claim 1, characterized in that, In step (2), the second solvent is an aqueous solution of ethanol.

7. The method according to claim 6, characterized in that, In step (2), the concentration of the aqueous ethanol solution is 30-80 wt%.

8. A CO2 separation mixed matrix composite membrane prepared by the method according to any one of claims 1-7.

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