A method for preparing defective MOFs mixed matrix membrane for carbon capture

Abstract

The present invention discloses a method for preparing a mixed matrix membrane of defective MOFs for carbon capture. The method adopts an in-situ synthesis strategy, utilizes the principle that metal ions can coordinate with hydroxyl groups to form a complex, uses a hydroxyl-rich functional small molecule β-cyclodextrin as a regulator, occupies the original binding site by coordinating with the metal ions, and introduces defect structures into MOFs in a competitive coordination manner. The introduction of the defect structure not only regulates the pore structure of MOFs, but also the hollow cylindrical structure of the functional small molecule itself not only provides an additional channel for gas transmission, further improving the permeability and gas screening ability; on the other hand, it exposes the metal sites, which interact with CO2; hydrogen bonds interact between the exposed carboxyl groups and the polymer, improving the interfacial compatibility; and there is good affinity between the hydroxyl groups and CO2. Under the coupling of multiple effects, a material with both high permeability and high selectivity is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of gas membrane separation and relates to a method for preparing a MOFs mixed matrix membrane for carbon capture defects. Background Art

[0002] CO2 capture, utilization, and storage technologies are currently a hot topic in research. While CO2 is the primary cause of the greenhouse effect, its storage and transportation, as a crucial industrial raw material, are also crucial issues. Traditional CO2 separation methods include cryogenic separation, pressure swing adsorption, and chemical absorption. Gas membrane separation technology is widely used due to its simplicity, stability, and sustainability. Within membrane separation technology, polymer membranes are limited by the "trade-off" phenomenon. While inorganic membranes offer excellent performance, their high cost and fragility limit their industrialization. Mixed matrix membranes (MMMs), made by blending a polymer matrix with an inorganic filler, combine the advantages of both polymer and inorganic membranes, significantly improving their gas separation performance.

[0003] The selection of inorganic fillers is crucial for improving the performance of mixed matrix membranes (MMMs). Among these inorganic fillers, metal-organic frameworks (MOFs) are widely used in gas separation, catalysis, and medicine due to their high surface area, high porosity, and regularly tunable pore size. The gas separation performance of MMMs can be effectively enhanced by selecting and modifying specific MOFs. Some researchers have modified MOFs through chemical etching and heat treatment to create hierarchical pores within them, which helps to increase gas diffusion rates. However, this method suffers from poor reproducibility and has certain structural requirements for the MOFs themselves. Alternatively, a one-step approach can be used to prepare MOFs that meet the desired specifications by selecting appropriate metal clusters and ligands. However, this approach is limited in the types of ligands and metal clusters, making it difficult to apply on a large scale. Post-modification by introducing small molecules to modulate pore structure is also a common approach. However, while this approach improves selectivity, it also sacrifices permeability, as the introduction of small molecules reduces pore size. Therefore, the goal of preparing membranes with both high permeability and high selectivity through a shorter reaction process is currently under investigation. Defect engineering is an emerging method for regulating the structure of MOFs. Compared with perfect MOFs crystals, defective MOFs will show superior performance in applications, which is attributed to the enhancement of porosity and the generation of abundant active sites. Zhong Chongli and others from Tianjin Polytechnic University invented a method for preparing Zr-based metal-organic framework-based mixed matrix membranes (CN202311832921.X). First, formic acid was used as a regulator to prepare o-UiO-66 with a defective structure. Subsequently, trifluoromethylbenzoic acid was introduced through a ligand exchange strategy. The presence of the defective structure and the introduction of trifluoromethylbenzoic acid enhanced the gas diffusion rate and separation performance. However, it is still a challenge to prepare high-performance membrane materials with both permeability and selectivity through a one-step method.

[0004] Therefore, we proposed leveraging the principle that metal ions can coordinate with hydroxyl groups to form complexes. Using β-cyclodextrin, a functional small molecule rich in hydroxyl groups, as a modulator, the coordination of hydroxyl groups with metal ions will occupy the original metal ion-ligand binding sites, introducing ligand defects into MOFs through competitive coordination. The introduction of ligand defects not only modulates the pore structure of MOFs, but also the hollow cylindrical structure of β-cyclodextrin itself provides additional channels for gas transport, thereby increasing the diffusion rate of gas molecules. Furthermore, the exposed metal sites and the presence of hydroxyl groups also enhance the adsorption capacity of CO2. Through this multi-faceted coupling effect, a membrane material with both high permeability and high selectivity was obtained. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a method for preparing a defective MOFs mixed-matrix membrane for carbon capture. Utilizing the mechanism by which metal ions can coordinate with hydroxyl groups to form a complex, the metal salt and functional molecule are first pretreated to ensure full contact between them, thereby achieving preferential coordination. Subsequently, through competitive coordination, the existing binding sites are occupied, introducing defect structures into the MOFs, constructing low-resistance CO2 mass transfer channels, and improving the gas separation performance of the membrane material. The present invention adopts an in-situ synthesis method, utilizing the principle that the hydroxyl groups on the functional small molecules can coordinate with metal ions, and introduces defect structures through competitive coordination. The introduction of the defect structure, on the one hand, regulates the pore structure of MOFs, increases its pore size and porosity, and on the other hand, the hollow cylindrical structure of the functional small molecules themselves not only provides an additional channel for gas transmission, further improving the permeability, but also the appropriate hollow pore size also improves the gas screening ability; on the other hand, the defect structure exposes abundant open metal sites in MOFs, and the interaction between the metal sites and CO2 enhances the adsorption performance of gas; there is a hydrogen bond interaction between the unreacted carboxyl groups and the polymer matrix, which effectively improves the interfacial compatibility between the two; in addition, the hydroxyl groups also have a good affinity for CO2, and the multiple effects are coupled to obtain a membrane material with both high permeability and high selectivity.

[0006] The technical solution of the present invention:

[0007] A method for preparing a defective MOFs mixed matrix membrane for carbon capture, comprising the following steps:

[0008] (1) Regulation of defect structure

[0009] First, the metal salt and the functional small molecule are pretreated: the molar ratio of the metal salt to the functional small molecule is controlled to be 1:X, X=2-16, and the two are ground in a ball mill. The grinding process allows the two to fully contact each other so that they can coordinate to achieve the purpose of competitive coordination. The parameters are set to 30Hz and the grinding time is 30min. After the grinding is completed, they are dissolved in a solvent and stirred at room temperature to completely dissolve them to obtain solution A; the molar ratio of the organic ligand to the metal salt is controlled to be 1:1, and then a certain amount of organic ligand is dissolved in a solvent and stirred at room temperature to completely dissolve them to obtain solution B; the two solutions are then mixed, stirred at room temperature for 30 minutes, and then ultrasonically treated. The mixture was evenly dispersed and bubbles were removed; the mixed solution was then transferred to a Teflon stainless steel autoclave. Due to the pretreatment of the metal salt and the functional small molecule, the two preferentially coordinated at high temperature, and then a defect structure could be introduced into the MOFs framework. MOFs were prepared by a solvothermal method with a reaction time of 24 hours; after the reaction was completed, it was allowed to cool naturally and the mixture was collected by centrifugation; the obtained powder was washed three times by centrifugation with a solvent, and finally the product was placed in an appropriate amount of ethanol for activation. After standing for 3 days, it was centrifuged and dried overnight in a vacuum at high temperature to ensure that the residual solvent in the MOFs pores was completely volatilized, and finally the activated defective MOFs were obtained for use;

[0010] (2) Preparation of gas separation membrane

[0011] First, the polymer particles and ethanol-water (mass ratio of 7:3) system were condensed, stirred and refluxed at 80°C to completely dissolve, thereby obtaining a transparent and uniform polymer solution with a mass fraction of 3%; then the prepared defective MOFs were dispersed into the polymer solution, and the addition amount of defective MOFs was controlled to be no more than 7% of the mass of the polymer particles. The resulting mixture solution was then dispersed and stirred at room temperature, and bubbles were removed by ultrasonic and static treatment; finally, the mixture was spread flat on a polytetrafluoroethylene plate, and MMMs were obtained by solvent evaporation at 50°C.

[0012] (3) Gas separation performance test

[0013] Before the gas permeation test, the MMMs were vacuum-treated at 50 °C for 12 h to remove the residual solvent. The prepared membranes were then cut to a suitable size and adhered to a copper sheet. After standing for 6 h, the gas permeation and separation performance tests of the membranes were performed.

[0014] The MOFs is NH2-UiO-66.

[0015] The metal salt is ZrCl4, and the organic ligand is 2-aminoterephthalic acid.

[0016] The solvent thermal reaction temperature is 120°C.

[0017] The vacuum drying temperature is 100°C.

[0018] The solvent includes water, N,N-dimethylformamide (DMF) and ethanol.

[0019] The functional small molecule includes β-cyclodextrin.

[0020] The polymer particles include segmented polyetheramide resin (Pebax), self-polymerized microporous polymer (PIM-1), etc.

[0021] Beneficial effects of the present invention: In view of the disadvantage that MOFs materials prepared by current defect engineering cannot have both high permeability and high selectivity, the present invention proposes to utilize the mechanism of mutual coordination between metal ions and hydroxyl groups, use functional small molecules as regulators, and coordinate hydroxyl groups with metal ions to occupy the original binding sites, and introduce defect structures into MOFs in a competitive coordination manner. On the one hand, the introduced defect structures can effectively improve the pore environment of MOFs and increase their pore size and porosity. On the other hand, the hollow cylindrical structure of the functional small molecules themselves not only provides an additional channel for gas transmission, further improving the permeability performance, but also the appropriate hollow pore size also improves the gas screening ability. On the other hand, the defect structure exposes rich metal sites in MOFs, and the metal sites have good interaction with CO2; there is hydrogen bond interaction between the exposed carboxyl groups and the polymer matrix, which effectively improves the interface descriptive properties; in addition, the good affinity between hydroxyl groups and CO2, under the coupling of multiple effects, the permeability and selectivity are jointly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XPS analysis diagram of NH2-UiO-66 and defective NH2-UiO-66 in the embodiment.

[0023] Figure 2 This is a graph showing the gas separation performance of the defective NH2-UiO-66 mixed matrix membrane when the loading amount is 5 wt.% in the embodiment. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0025] Example 1:

[0026] Preparation of defective β-CD@NUiO: Defective β-CD@NUiO was prepared using a solvothermal method. First, the metal salt and functional small molecule were pretreated. 0.233g ZrCl4 and 0.28375g β-cyclodextrin were placed in a grinder and ground at 30Hz for 30 minutes. After the two were mixed evenly, they were added to 20ml DMF solution and stirred at room temperature for 10 minutes to completely dissolve. Then, 0.181g 2-aminoterephthalic acid was slowly added to 30ml. The DMF solution was stirred at room temperature for 10 minutes. After it was completely dissolved, the two solutions were mixed together and stirred for 30 minutes to mix them evenly. Then, it was ultrasonicated for 5 minutes to remove bubbles. Then, it was transferred to a 100mL Teflon stainless steel autoclave at room temperature and reacted at 120° for 24 hours by solvent thermal method. After it was naturally cooled, the obtained product was collected by centrifugation and washed three times with water, DMF and ethanol solvents respectively. Finally, the product was placed in an appropriate amount of ethanol for activation. After standing for 3 days, it was centrifuged and separated. The obtained product was vacuum dried at 100° for 12 hours to obtain activated defective β-CD@NUiO. XPS analysis of the material showed that Figure 1 As shown in the O 1s region, the binding energy of Zr-O-Zr is blue-shifted, indicating that some Zr-O-Zr bonds of defective β-CD@NUiO are broken during synthesis, resulting in ligand defects. As the content of functional small molecules increases, the proportion of ligand deficiency also gradually increases.

[0027] Preparation of gas separation membranes: Pebax particles were mixed into ethanol-water (mass ratio of 7:3) and condensed and stirred under reflux at 80°C to completely dissolve, thereby obtaining a transparent and uniform solution with a mass fraction of 3%. Simultaneously, a certain amount of defective β-CD@NUiO was dispersed into the casting solution to prepare MMMs with a filler loading of 5%. The filler was fully dispersed by ultrasonication and stirring. The resulting mixture was stirred at room temperature for 5 hours, ultrasonicated for 3 minutes, and then allowed to stand for 2 minutes to remove bubbles. Finally, the mixture was spread on a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C.

[0028] Gas separation performance test: The prepared MMMs were vacuum treated at 50 °C for 12 h to remove the residual solvent, and then the gas permeation and separation performance of the membranes were tested.

[0029] Example 2:

[0030] Preparation of defective β-CD@NUiO: Defective β-CD@NUiO was prepared using a solvothermal method. First, the metal salt and functional small molecule were pretreated. 0.233g ZrCl4 and 0.141875g β-cyclodextrin were placed in a grinder and ground at 30Hz for 30 minutes. After the two were mixed evenly, they were added to 20ml DMF solution and stirred at room temperature for 10 minutes to completely dissolve. Then, 0.181g 2-aminoterephthalic acid was slowly added to 30ml. The product was placed in a DMF solution and stirred at room temperature for 10 minutes. After it was completely dissolved, the two solutions were mixed together and stirred for 30 minutes to mix evenly. Then, it was ultrasonicated for 5 minutes to remove bubbles. Then, it was transferred to a 100mL Teflon stainless steel autoclave at room temperature and reacted at 120° for 24 hours by a solvothermal method. After it was naturally cooled, the resulting product was collected by centrifugation and washed three times with water, DMF, and ethanol solvents respectively. Finally, the product was placed in an appropriate amount of ethanol for activation. After standing for 3 days, it was centrifuged and separated. The resulting product was vacuum dried at 100° for 12 hours to obtain activated defective β-CD@NUiO.

[0031] Preparation of gas separation membranes: Pebax particles were mixed into ethanol-water (mass ratio of 7:3) and condensed and stirred under reflux at 80°C to completely dissolve, thereby obtaining a transparent and uniform solution with a mass fraction of 3%. Simultaneously, a certain amount of defective β-CD@NUiO was dispersed into the casting solution to prepare MMMs with a filler loading of 5%. The filler was fully dispersed by ultrasonication and stirring. The resulting mixture was stirred at room temperature for 5 hours, ultrasonicated for 3 minutes, and then allowed to stand for 2 minutes to remove bubbles. Finally, the mixture was spread on a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C.

[0032] Gas separation performance test: The prepared MMMs were vacuum treated at 50 °C for 12 h to remove the residual solvent, and then the gas permeation and separation performance of the membranes were tested.

[0033] Example 3:

[0034] Preparation of defective β-CD@NUiO: Defective β-CD@NUiO was prepared by a solvothermal method. First, the metal salt and functional small molecule were pretreated. 0.233g ZrCl4 and 0.5675g β-cyclodextrin were placed in a grinder and ground at 30Hz for 30 minutes. After the two were mixed evenly, they were added to 20ml DMF solution and stirred at room temperature for 10 minutes to completely dissolve. Then, 0.181g 2-aminoterephthalic acid was slowly added to 30ml DMF solution and stirred at room temperature for 10 minutes. After it was completely dissolved, the two solutions were mixed together and stirred for 30 minutes to mix evenly. Then, ultrasonication was performed for 5 minutes to remove bubbles. The mixture was then transferred to a 100mL Teflon stainless steel autoclave at room temperature and reacted at 120°C for 24 hours via a solvothermal method. After cooling naturally, the resulting product was collected by centrifugation and washed three times with water, DMF, and ethanol solvents respectively. Finally, the product was activated in an appropriate amount of ethanol, allowed to stand for 3 days, and then centrifuged and dried in a vacuum at 100°C for 12 hours to obtain activated defective β-CD@NUiO.

[0035] Preparation of gas separation membranes: Pebax particles were mixed into ethanol-water (mass ratio of 7:3) and condensed and stirred under reflux at 80°C to completely dissolve, thereby obtaining a transparent and uniform solution with a mass fraction of 3%. Simultaneously, a certain amount of defective β-CD@NUiO was dispersed into the casting solution to prepare MMMs with a filler loading of 5%. The filler was fully dispersed by ultrasonication and stirring. The resulting mixture was stirred at room temperature for 5 hours, ultrasonicated for 3 minutes, and then allowed to stand for 2 minutes to remove bubbles. Finally, the mixture was spread on a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C.

[0036] Gas separation performance test: The prepared MMMs were vacuum treated at 50 °C for 12 h to remove the residual solvent, and then the gas permeation and separation performance of the membranes were tested.

[0037] Example 4:

[0038] Preparation of defective β-CD@NUiO: Defective β-CD@NUiO was prepared by a solvothermal method. First, the metal salt and functional small molecule were pretreated. 0.233g ZrCl4 and 1.135g β-cyclodextrin were placed in a grinder and ground at 30Hz for 30 minutes. After the two were mixed evenly, they were added to 20ml DMF solution and stirred at room temperature for 10 minutes to completely dissolve. Then, 0.181g 2-aminoterephthalic acid was slowly added to 30ml DMF solution and stirred at room temperature for 10 minutes. After it was completely dissolved, the two solutions were mixed together and stirred for 30 minutes to mix evenly. Then, ultrasonication was performed for 5 minutes to remove bubbles. The mixture was then transferred to a 100mL Teflon stainless steel autoclave at room temperature and reacted at 120°C for 24 hours via a solvothermal method. After cooling naturally, the resulting product was collected by centrifugation and washed three times with water, DMF, and ethanol solvents respectively. Finally, the product was activated in an appropriate amount of ethanol, allowed to stand for 3 days, and then centrifuged and dried in a vacuum at 100°C for 12 hours to obtain activated defective β-CD@NUiO.

[0039] Preparation of gas separation membranes: Pebax particles were mixed into ethanol-water (mass ratio of 7:3) and condensed and stirred under reflux at 80°C to completely dissolve, thereby obtaining a transparent and uniform solution with a mass fraction of 3%. Simultaneously, a certain amount of defective β-CD@NUiO was dispersed into the casting solution to prepare MMMs with a filler loading of 5%. The filler was fully dispersed by ultrasonication and stirring. The resulting mixture was stirred at room temperature for 5 hours, ultrasonicated for 3 minutes, and then allowed to stand for 2 minutes to remove bubbles. Finally, the mixture was spread on a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C.

[0040] Gas separation performance test: The prepared MMMs were vacuum treated at 50 °C for 12 h to remove the residual solvent, and then the gas permeation and separation performance of the membranes were tested.

[0041] Comparative Example 1:

[0042] Preparation of NH2-UiO-66: NH2-UiO-66 was prepared by a solvothermal method. First, 0.233g ZrCl4 was added to 20ml DMF solution and stirred at room temperature for 10min to completely dissolve it; then 0.181g 2-aminoterephthalic acid was slowly added to 30ml DMF solution and stirred at room temperature for 10min. After it was completely dissolved, the two solutions were mixed together and stirred for 30min to mix them evenly. Then, ultrasonication was performed for 5min to remove bubbles. Then, it was transferred to a 100mL Teflon stainless steel autoclave at room temperature and reacted at 120° for 24h by a solvothermal method. After it was naturally cooled, the obtained product was collected by centrifugation and washed three times with water, DMF, and ethanol solvents respectively. Finally, the product was placed in an appropriate amount of ethanol for activation. After standing for 3 days, it was centrifuged and separated. The obtained product was vacuum dried at 100° for 12h to obtain activated NH2-UiO-66.

[0043] Preparation of gas separation membranes: Pebax particles were mixed into ethanol-water (mass ratio of 7:3), condensed and stirred under reflux at 80°C for complete dissolution, thereby obtaining a transparent and uniform solution with a mass fraction of 3%. Simultaneously, a certain amount of NH2-UiO-66 was dispersed into the casting solution to prepare MMMs with a filler loading of 5%. The filler was fully dispersed by ultrasonication and stirring. The resulting mixture was stirred at room temperature for 5 hours, ultrasonicated for 3 minutes, and then allowed to stand for 2 minutes to remove bubbles. Finally, the mixture was spread on a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C.

[0044] Gas separation performance test: The prepared MMMs were vacuum treated at 50 °C for 12 h to remove the residual solvent, and then the gas permeation and separation performance of the membranes were tested.

[0045] Comparative Example 2:

[0046] Preparation of defective TA@NUiO: Defective TA@NUiO was prepared by a solvothermal method. First, 0.233g ZrCl4 and 0.4252g tannic acid were placed in a grinder and ground for 30min at 30Hz. After the two were mixed evenly, they were added to 20ml DMF solution and stirred at room temperature for 10min to completely dissolve them. Then, 0.181g 2-aminoterephthalic acid was slowly added to 30ml DMF solution and stirred at room temperature for 10min. After it was completely dissolved, the two solutions were mixed together and stirred for 30min to mix evenly. Then, ultrasonication was performed for 5min to remove bubbles. Then, the mixture was transferred to a 100mL Teflon stainless steel autoclave at room temperature and reacted at 120°C for 24h by solvothermal method. After it was naturally cooled, the obtained product was collected by centrifugation and washed three times with water, DMF, and ethanol solvents respectively. Finally, the product was placed in an appropriate amount of ethanol for activation. After standing for 3 days, it was centrifuged and separated. The obtained product was vacuum dried at 100°C for 12h to obtain activated defective TA@NUiO.

[0047] Preparation of gas separation membranes: Pebax particles were mixed into ethanol-water (mass ratio of 7:3) and condensed and stirred under reflux at 80°C to completely dissolve, thereby obtaining a transparent and uniform solution with a mass fraction of 3%. Simultaneously, a certain mass of TA@NUiO was dispersed into the casting solution to prepare MMMs with a filler loading of 5%. The filler was fully dispersed by ultrasonication and stirring. The resulting mixture was stirred at room temperature for 5 hours, ultrasonicated for 3 minutes, and then allowed to stand for 2 minutes to remove bubbles. Finally, the mixture was spread onto a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C.

[0048] Gas separation performance test: The prepared MMMs were vacuum treated at 50 °C for 12 h to remove the residual solvent, and then the gas permeation and separation performance of the membranes were tested.

[0049] At 0.3 bar and 25°C, Figure 2As shown, the gas separation performance of defective NH2-UiO-66 mixed matrix membranes is improved compared to unmodified NH2-UiO-66. This is due to the introduction of functional small molecules into the MOF framework, which modulates the pore structure of the composite material and thus improves gas separation performance. This demonstrates the feasibility of preparing defective MOFs using hydroxyl-rich functional small molecules as modulators. Compared to tannic acid, the introduction of β-cyclodextrin significantly improves gas separation performance. This is because β-cyclodextrin is not only rich in hydroxyl groups but also has a hollow cylindrical structure, which provides additional transport channels for CO2 separation. Furthermore, its suitable pore size also enhances its sieving performance. Therefore, compared to tannic acid, the use of β-cyclodextrin as a modulator increases CO2 permeability by 15.5% and CO2 / N2 selectivity by 40%, further enhancing performance. This suggests that the use of β-cyclodextrin as a modulator in preparing defective MOFs for carbon capture holds great promise. In summary, defective MOFs have broad industrial application prospects in improving membrane permeability selectivity.

[0050] The above embodiments are intended to illustrate the technical solutions of the present invention and are intended to facilitate understanding and implementation of the present invention by those familiar with the art. However, the present invention is not limited to the above embodiments. Any modifications, combinations, or simplifications that do not depart from the spirit and principles of the present invention are considered equivalent and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a mixed matrix membrane of MOFs for carbon capture defects, characterized in that: Here are the steps: (1) Regulation of defect structure First, the metal salt and the functional small molecule are pretreated: the molar ratio of the metal salt to the functional small molecule is controlled to be 1:X, X=2-16; the two are ground, dissolved in a solvent after grinding, and stirred at room temperature to completely dissolve to obtain solution A; the organic ligand is dissolved in a solvent and stirred at room temperature to completely dissolve to obtain solution B; then solution A and solution B are mixed, the molar ratio of the organic ligand to the metal salt is controlled to be 1:1, stirred at room temperature, and then ultrasonically treated to uniformly disperse and remove bubbles; the mixed solution is then transferred to an autoclave, and MOFs are prepared by a solvothermal method with a reaction time of 24 hours; after the reaction is completed, it is allowed to cool naturally and the mixture is collected by centrifugation; the obtained powder is washed three times with a solvent respectively, and finally the product is placed in ethanol for activation, allowed to stand for 3 days and then centrifuged, and the product is vacuum dried overnight at high temperature to ensure that the residual solvent in the MOFs pores is completely volatilized, and finally activated defective MOFs are obtained; (2) Preparation of gas separation membranes First, polymer particles and an ethanol-water system with a mass ratio of 7:3 were condensed, stirred, and refluxed at 80°C to completely dissolve them, obtaining a transparent, uniform polymer solution with a mass fraction of 3%. Activated defective MOFs were then dispersed into the polymer solution, with the amount of defective MOFs added controlled to not exceed 7% of the polymer particle mass. The resulting mixture was then dispersed and stirred at room temperature, and then subjected to ultrasonication and standing to remove bubbles. Finally, the mixture was spread onto a polytetrafluoroethylene plate and the MMMs were obtained by solvent evaporation at 50°C. The metal salt is ZrCl4; The organic ligand is 2-aminoterephthalic acid; The functional small molecule is beta-cyclodextrin.

2. The preparation method according to claim 1, characterized in that The MOFs is NH2-UiO-66.

3. The preparation method according to claim 1, characterized in that The solvent thermal reaction temperature is 120°C.

4. The preparation method according to claim 1, characterized in that The vacuum drying temperature is 100°C.

5. The preparation method according to claim 1, characterized in that The solvent is water, N,N-dimethylformamide and ethanol.

6. The preparation method according to claim 1, characterized in that The polymer particles are segmented polyetheramide resin or self-polymerized microporous polymer.

7. The preparation method according to claim 1, characterized in that The grinding was carried out in a grinder at 30 Hz for 30 min.

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