Preparation method of defective MOF-based self-microporous polymer mixed matrix membrane for efficient separation of propylene and propane

Abstract

The present invention belongs to the technical field of gas separation membranes and discloses a method for preparing a defective MOF-based self-microporous polymer mixed matrix membrane for efficient propylene and propane separation. A defective MOF with a hollow nanoframe structure is prepared by acid etching the MOF, and the mixed matrix membrane is prepared with a self-microporous polymer containing electron-donating groups. The open metal sites in the defective MOF are coordinated with the self-microporous polymer to improve interfacial compatibility, while the open metal sites in the defective MOF are also utilized to enhance propylene adsorption. The membrane material prepared by the present invention exhibits excellent propylene and propane separation performance and is expected to find promising applications in this field.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane preparation and application, and discloses a method for preparing a defective MOF-based self-microporous polymer mixed matrix membrane for efficient separation of propylene and propane. Background Art

[0002] Propylene is one of the world's largest chemical products and an important basic chemical raw material. Currently, the separation of propylene and propane mainly relies on cryogenic separation technology, but this technology has high energy consumption and a complex separation process. Since propylene and propane have only slight differences in physical and chemical properties (boiling points are -47.6℃ and -42.1℃ respectively; van der Waals diameters are and ), making separation difficult. According to statistics, the purification of propylene and ethylene alone accounts for 0.3% of global energy consumption, making it an energy-intensive separation process (Sholl, DS and RP Lively (2016). "Seven chemicals separations to change the world." Nature 532(7600):435-437.). Therefore, the development of low-energy, high-efficiency separation technologies is of great significance.

[0003] Membrane separation technology, as an efficient and low-energy separation method, shows great application potential due to its small footprint and simple operation. Microporous polymers (such as high-free-volume polyimides and self-microporous polymers) are very promising membrane materials for propylene / propane separation, but their separation performance is limited by the trade-off between gas permeability and selectivity. To solve this problem, mixed matrix membranes (MMMs) came into being. They are composed of a flexible or semi-rigid polymer phase and a dispersed rigid high-performance filler phase (such as metal-organic framework MOF). Through synergistic optimization, the separation performance is significantly improved. Despite this, MMMs still face the problem of insufficient interfacial compatibility. Therefore, improving interfacial compatibility becomes the key to optimizing the performance of MMMs.

[0004] Defect engineering in MOFs is an emerging approach that modulates the pore structure and adsorption properties of materials by introducing ligand or metal cluster defects. For example, acid-base post-treatment can introduce defects in MOFs through acid / base treatment. Studies by Vermoortele et al. have shown that post-synthesis removal of modulators can result in a large number of coordinatively unsaturated metal sites (Vermoortele, F., et al. (2013)).

[0005] "Synthesis Modulation as a Tool To Increase the Catalytic Activity of Metal-Organic Frameworks: The Unique Case of UiO-66(Zr). Journal of the American Chemical Society 135(31): 11465-11468.). This method not only enhances porosity but also creates abundant open metal sites. However, in order to introduce the unique advantages of defective MOFs into propylene / propane gas membrane separation, it is necessary to select a suitable etching strategy, consider the impact of defective MOFs on the mixed matrix membrane and the desired separation gas, and balance the effect of etching degree on permeability and selectivity to optimize gas separation performance.

[0006] Based on this, the present invention proposes a simple and efficient strategy: preparing defective MOFs by acid-etching MOFs and blending them with self-microporous polymers containing electron-donating groups to create high-performance mixed matrix membranes. The open metal sites in the defective MOFs enhance propylene adsorption capacity while also coordinating with the self-microporous polymers, significantly improving interfacial compatibility. Experimental results demonstrate that the defective MOF-based MMMs surpass the 2003 upper limit for propylene / propane separation, demonstrating excellent separation performance. Summary of the Invention

[0007] In order to solve the problems of poor interfacial compatibility and insufficient propylene-propane separation performance of existing mixed matrix membranes, the present invention proposes a defective MOF-based self-microporous polymer mixed matrix membrane for efficient propylene-propane separation and a preparation method thereof.

[0008] The main content of this invention is to prepare a defective MOF-based self-microporous polymer mixed matrix membrane by acid-etching MOF and blending it with a self-microporous polymer containing electron-donating groups. The open metal sites in the defective MOF enhance propylene adsorption capacity and, at the same time, coordinate with the self-microporous polymer containing electron-donating groups, significantly improving interfacial compatibility. The prepared defective MOF-based self-microporous polymer mixed matrix membrane exhibits excellent propylene and propane separation performance.

[0009] The technical solution of the present invention:

[0010] A method for preparing a defective MOF-based self-microporous polymer mixed matrix membrane for efficient separation of propylene and propane, comprising the following steps:

[0011] (1) Synthesis of MOF: Metal salt A and 2-methylimidazole are dispersed in a reaction medium, and the metal salt A solution is quickly poured into the 2-methylimidazole solution for stirring and reacting to obtain a milky white suspension; the suspension is centrifuged using a centrifuge, and then washed and centrifuged several times for purification, and dried in a vacuum oven to obtain MOF nanoparticles;

[0012] Wherein, metal salt A is zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate;

[0013] The reaction medium is methanol and / or ethanol;

[0014] The molar ratio of metal salt A to 2-methylimidazole is 1:2-16;

[0015] The reaction temperature is 25°C;

[0016] The centrifuge speed was 10000 rpm and the centrifugation time was 10 min;

[0017] The solvent used for washing was methanol;

[0018] The drying temperature is 80°C and the drying time is 24h;

[0019] (2) Acid etching of MOF: dissolving acid A in solvent A to obtain a colorless transparent solution; dispersing the MOF nanoparticles synthesized in step (1) in solvent A, and obtaining a uniform MOF suspension after ultrasonication; blending the colorless transparent solution with the MOF suspension, stirring the mixture at a certain temperature, collecting the mixture by centrifugation, washing the mixture with solvent A, centrifuging the mixture several times, and drying the mixture in a vacuum oven to obtain defective MOF particles after etching;

[0020] Wherein, acid A is one or a mixture of two or more of cyanuric acid, citric acid, glycine, gallic acid, and methyl gallate;

[0021] Solvent A is methanol and / or ethanol;

[0022] The molar ratio of acid A to MOF nanoparticles is 1:1-8;

[0023] The reaction time is 12-36 hours, and the reaction temperature is 25-80°C;

[0024] The centrifuge speed was 10000 rpm and the centrifugation time was 10 min;

[0025] The drying temperature is 80°C and the drying time is 24h;

[0026] (3) Synthesis of amidoxime-based PIM-1 (AO-PIM-1): First, unmodified PIM-1 polymer was synthesized. 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane, tetrafluoroterephthalonitrile and anhydrous potassium carbonate were added to a mixed solution of solvent B and solvent C. After stirring at room temperature to fully disperse, the mixture was reacted at a certain temperature under the atmosphere of protective gas A. After the reaction was completed, the product was washed with solvent A, dissolved in solvent D and allowed to stand, and then solvent A was added to precipitate. The obtained polymer was washed with deionized water and finally dried in a vacuum oven to obtain a purified PIM-1 polymer. Subsequently, the synthesized PIM-1 polymer was dissolved in solvent E and heated to dissolve under an atmosphere of protective gas A. After the temperature was gradually raised to the reaction temperature, a 50 wt% aqueous solution of hydroxylamine was added dropwise to carry out a reflux reaction. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into solvent A for precipitation, vacuum filtered and washed with solvent A, and finally dried in a vacuum oven to obtain a flocculent or powdery AO-PIM-1 polymer.

[0027] The molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane, tetrafluoroterephthalonitrile and anhydrous potassium carbonate is 1:1:3; solvent B and solvent C are N,N-dimethylacetamide (DMAC) and toluene, respectively, with a mass ratio of 2:1;

[0028] Solvent D is chloroform; Solvent E is tetrahydrofuran;

[0029] Protective gas A is nitrogen;

[0030] The reaction temperature of PIM-1 was 155°C and the reaction time was 60 min;

[0031] The drying temperature of PIM-1 was 120°C and the drying time was 24 h;

[0032] The reaction temperature of AO-PIM-1 was 69 °C and the reaction time was 2 h;

[0033] The drop rate of the hydroxylamine aqueous solution was 1 mL / min;

[0034] The drying temperature of AO-PIM-1 was 120°C and the drying time was 24 h;

[0035] (4) Preparation of AO-PIM-1 membrane: AO-PIM-1 polymer was dissolved in solvent F to prepare a casting solution, stirred to fully dissolve, filtered through a microporous membrane filter, and then ultrasonically defoamed. The solution was then placed in an oven at a certain temperature to evaporate the solvent and form a membrane;

[0036] Wherein, solvent F is N,N-dimethylformamide and / or N,N-dimethylacetamide;

[0037] The mass fraction of AO-PIM-1 polymer in the casting solution is 2-5 wt%;

[0038] The stirring time is 12-24h, and the ultrasonic time is 20min;

[0039] The solvent's evaporation temperature is 50°C and its evaporation time is 24h;

[0040] (5) Preparation of DMMM: The defective MOF synthesized in step (2) is activated in a vacuum drying oven and ultrasonically dispersed in solvent H to obtain a defective MOF dispersion; AO-PIM-1 is dissolved in solvent F; the AO-PIM-1 solution filtered through a microporous membrane filter is blended with the defective MOF dispersion, and the AO-PIM-1 solution is added to the defective MOF dispersion twice to prepare a casting solution, which is initially dispersed by ultrasound, stirred to be fully dispersed, and then ultrasonically defoamed. After standing, the solution is poured into a culture dish and allowed to stand in an oven at a certain temperature to volatilize the solvent to form a film;

[0041] Among them, the ultrasound time was 30 min;

[0042] The stirring time is 12-24 hours and the standing time is 2 hours;

[0043] The oven temperature is 50°C and the volatilization time is 24h.

[0044] Compared to existing technologies, the present invention offers significant advantages. Compared to other mixed-matrix membranes, the present invention utilizes acid-etched MOFs to prepare defective MOFs. The open metal sites within the defective MOFs enhance propylene adsorption capacity and, at the same time, coordinate with the self-microporous polymer containing electron-donating groups, significantly improving interfacial compatibility. The resulting defective MOF-based self-microporous polymer mixed-matrix membrane exhibits excellent propylene and propane separation performance, offering advantages such as a simple preparation method and significant results. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1(a) is a schematic diagram of the preparation of defective ZIF-8-based AO-PIM-1 mixed matrix membrane;

[0046] Figure 1(b) is the upper limit graph of the defective ZIF-8-based AO-PIM-1 mixed matrix membrane for propylene and propane separation performance.

[0047] Figure 2 is a comparison of the SEM images of ZIF-8 (a) and DZIF-8 (b). The SEM image of DZIF-8 shows a hollow nanoframe structure, indicating that the etching was successful.

[0048] Figure 3This is a comparison of the BET diagrams of ZIF-8 and DZIF-8. The hysteresis loop presented by DZIF-8 is wider and more extensive, showing the hysteresis loop characteristics of the microporous-mesoporous material after etching, which is confirmed by the SEM diagram. DETAILED DESCRIPTION

[0049] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0050] Gas separation performance test: The method used for the gas separation performance test in the present invention is a constant volume pressure method, with a test temperature of 35° C. and a test pressure of 0.2 MPa.

[0051] Example 1

[0052] (1) Synthesis of AO-PIM-1 polymer: First, the PIM-1 polymer was synthesized by adding 3.4 g of TTSBI (0.01 mol), 2.0 g of TFTPN (0.01 mol), and 4.15 g of anhydrous K2CO3 (0.03 mol) to a three-necked flask. Then, 20 mL of anhydrous DMAC and 10 mL of toluene were added and mechanically stirred at room temperature for about 20 min. The mixture was reacted at 155°C under a nitrogen atmosphere for 60 min. After the reaction, the product was initially washed in methanol, then dissolved in chloroform and allowed to stand for 12 h. Methanol was then added for reprecipitation and washing. Then, a light yellow solid was obtained by vacuum filtration and drying, and then washed with deionized water to remove residual salts. Finally, the purified PIM-1 product was obtained by vacuum filtration and vacuum drying at 120°C for 24 h. Next, an amidoxime-modified AO-PIM-1 polymer was synthesized. 1.0 g of PIM-1 was added to a three-necked flask, followed by dissolution in 65 mL of THF (bp 66°C). The polymer was heated to 65°C under an inert nitrogen atmosphere. Once the polymer was completely dissolved, the temperature was raised to 69°C and maintained for a period of time. Then, 10 mL of a 50 wt% aqueous hydroxylamine solution was added dropwise to the polymer solution using a constant pressure dropping funnel. A precipitate formed in the solution and redissolved after 20 minutes. The reaction mixture was refluxed at 69°C for 2 hours. After the reaction was complete, the turbid solution was cooled to room temperature and poured into ethanol for precipitation. The precipitate was vacuum filtered, washed three times with 200 mL of ethanol, and dried in an oven at 110°C for 3 hours to obtain a flocculent or powdery AO-PIM-1 product.

[0053] (2) Synthesis of defective ZIF-8 etched by cyanuric acid: 2.98 g Zn(NO3)2·6H2O (0.01 mol) and 6.56 g 2-methylimidazole (0.08 mol) were dissolved in 100 mL methanol, and then the Zn(NO3)2·6H2O methanol solution was quickly poured into the 2-methylimidazole methanol solution and stirred for 1 h. The resulting suspension was milky white and then centrifuged at 25°C (10,000 rpm, 10 min), washed with methanol and centrifuged three times, and dried in vacuum at 80°C for 24 h to collect ZIF-8 nanoparticles. 0.12 g cyanuric acid was dissolved in 100 mL ethanol with stirring at 60°C for 30 min to form a colorless, transparent, and homogeneous solution. 0.12 g ZIF-8 powder (average diameter ~100 nm) was added to 20 mL ethanol and the ZIF-8 was dispersed by ultrasonic oscillation to obtain a homogeneous suspension. Defective ZIF-8 (DZIF-8) with varying degrees of etching were prepared by mixing a cyanuric acid solution with a ZIF-8 suspension and ultrasonically dispersing the mixture. The resulting suspension was then stirred at 60°C for 12 or 24 hours. After the reaction, the etched DZIF-8 was collected by centrifugation, washed several times with anhydrous ethanol, and finally dried under vacuum at 80°C for 24 hours.

[0054] (3) Preparation of 5 wt% defective ZIF-8-based mixed matrix membrane: DZIF-8 etched with cyanuric acid was activated in a vacuum drying oven at 150°C for 3 h. Subsequently, 0.01 g of DZIF-8 was dispersed in 4.8 g of N,N-dimethylformamide using ultrasound. AO-PIM-1 (0.19 g) solution dissolved in N,N-dimethylformamide (5.0 g) was filtered through a 10 μm filter membrane to remove impurities. During the blending process, 50% of the AO-PIM-1 solution was added to the DZIF-8 dispersion for priming and ultrasonic treatment for 30 min. The remaining 50% of the AO-PIM-1 solution was then added to the mixed solution, stirred for 12 h, ultrasonically degassed for 30 min, and allowed to stand for 2 h. Finally, the mixed solution was placed in a glass culture dish and allowed to stand in a 50°C oven for 24 h to evaporate the solvent and form a membrane.

[0055] Example 2

[0056] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0057] (2) Synthesis of defective ZIF-8 etched by cyanuric acid: The method is consistent with step (2) in Example 1.

[0058] (3) Preparation of 10 wt% defective ZIF-8-based mixed matrix membrane: the amount of DZIF-8 used was 0.02 g, the amount of AO-PIM-1 used was 0.18 g, and the other methods were the same as step (3) in Example 1.

[0059] Example 3

[0060] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0061] (2) Synthesis of defective ZIF-8 etched by cyanuric acid: The method is consistent with step (2) in Example 1.

[0062] (3) Preparation of 15 wt% defective ZIF-8-based mixed matrix membrane: the amount of DZIF-8 used was 0.03 g, the amount of AO-PIM-1 used was 0.17 g, and the other methods were the same as step (3) in Example 1.

[0063] Example 4

[0064] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0065] (2) Synthesis of defective ZIF-8 etched by citric acid: ZIF-8 was synthesized according to step (2) in Example 1. 0.12 g of ZIF-8 powder (average diameter ~100 nm) was added to 20 mL of methanol and the ZIF-8 was dispersed by ultrasonic oscillation to obtain a uniform suspension. 0.14 g of citric acid was dissolved in 100 mL of ethanol and stirred at room temperature for 30 min to form a colorless, transparent, uniform solution. The citric acid solution was blended with the ZIF-8 suspension and ultrasonically dispersed. The resulting suspension was stirred at room temperature for 12 or 24 h to prepare defective ZIF-8 (DZIF-8) with different etching degrees. After the reaction was completed, the etched DZIF-8 was collected by centrifugation, washed several times with anhydrous methanol, and finally dried in vacuum at 80°C for 24 hours before collection.

[0066] (3) Preparation of 5, 10, and 15 wt% defective ZIF-8-based mixed matrix membranes: The filler used in the preparation of 5, 10, and 15 wt% DMMM is DZIF-8 etched with citric acid. The amounts of polymer and filler required for the preparation of 5, 10, and 15 wt% DMMM are referred to Examples 1, 2, and 3, respectively. The other preparation methods are the same.

[0067] Example 5

[0068] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0069] (2) Synthesis of glycine-etched defective ZIF-8: The amount of glycine used was 0.36 g, and the other synthesis steps were consistent with step (2) in Example 4.

[0070] (3) Preparation of 5, 10, and 15 wt% defective ZIF-8-based mixed matrix membranes: The filler used in the preparation of 5, 10, and 15 wt% DMMM is glycine-etched DZIF-8. The amounts of polymer and filler required for the preparation of 5, 10, and 15 wt% DMMM are referred to Examples 1, 2, and 3, respectively. The other preparation methods are the same.

[0071] Example 6

[0072] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0073] (2) Synthesis of gallic acid-etched defective ZIF-8: The amount of gallic acid used was 0.16 g, and the other synthesis steps were consistent with step (2) in Example 4.

[0074] (3) Preparation of 5, 10, and 15 wt% defective ZIF-8-based mixed matrix membranes: The filler used in the preparation of 5, 10, and 15 wt% DMMM is DZIF-8 etched with gallic acid. The amounts of polymer and filler required for the preparation of 5, 10, and 15 wt% DMMM are referred to Examples 1, 2, and 3, respectively. The other preparation methods are the same.

[0075] Example 7

[0076] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0077] (2) Synthesis of defective ZIF-8 etched with methyl gallate: The amount of methyl gallate used was 0.15 g, and the other synthesis steps were consistent with step (2) in Example 4.

[0078] (3) Preparation of 5, 10, and 15 wt% defective ZIF-8-based mixed matrix membranes: The filler used in the preparation of 5, 10, and 15 wt% DMMM is DZIF-8 etched with methyl gallate. The amounts of polymer and filler required for the preparation of 5, 10, and 15 wt% DMMM are referred to Examples 1, 2, and 3, respectively. The other preparation methods are the same.

[0079] Comparative Example 1

[0080] (1) Synthesis of PIM-1: The method is consistent with the synthesis of PIM-1 in step (1) of Example 1.

[0081] (2) Preparation of PIM-1 membrane: 0.2 g of PIM-1 was dissolved in 9.8 g of chloroform to prepare a 2 wt% casting solution. The solution was stirred for 24 h and filtered through a 10 μm filter membrane. The solution was then ultrasonicated for 20 min to defoam and allowed to stand for 2 h. Finally, the solution was poured into a glass culture dish and allowed to stand at room temperature for 24 h to evaporate the solvent and form a membrane.

[0082] Comparative Example 2

[0083] (1) Synthesis of AO-PIM-1: The method is consistent with the synthesis of AO-PIM-1 in step (1) of Example 1.

[0084] (2) Preparation of AO-PIM-1 membrane: 0.2 g of AO-PIM-1 was dissolved in 9.8 g of N,N-dimethylformamide to prepare a 2 wt% casting solution. The solution was stirred for 24 h and filtered through a 10 μm filter membrane. The solution was then ultrasonicated for 20 min to defoam and allowed to stand for 2 h. Finally, the solution was poured into a glass culture dish and allowed to stand in an oven at 50 °C for 24 h to evaporate the solvent and form a membrane.

[0085] Comparative Example 3

[0086] (1) Synthesis of AO-PIM-1 polymer: The method is consistent with step (1) in Example 1.

[0087] (2) Synthesis of ZIF-8: ZIF-8 was synthesized according to step (2) in Example 1.

[0088] (3) Preparation of 10 wt% ZIF-8-based mixed matrix membrane: ZIF-8 was activated in a vacuum drying oven at 150°C for 3 h. Subsequently, 0.02 g ZIF-8 was dispersed in 4.8 g N,N-dimethylformamide using ultrasound. AO-PIM-1 (0.18 g) solution dissolved in N,N-dimethylformamide (5.0 g) was filtered through a 10 μm filter membrane to remove impurities. During the blending process, 50% AO-PIM-1 solution was added to the ZIF-8 dispersion for priming and ultrasonic treatment for 30 min. The remaining 50% AO-PIM-1 solution was then added to the mixed solution, stirred for 12 h, ultrasonically degassed for 30 min, and allowed to stand for 2 h. Finally, the mixed solution was placed in a glass culture dish and allowed to stand in a 50°C oven for 24 h to evaporate the solvent and form a membrane.

[0089] The propylene propane permeability and selectivity of the gas separation membranes prepared by Control Examples 1-3 and Examples 1-3 are shown in Table 1. By comparing the Control Examples with the Examples, it can be found that the DMMMs (5%, 10%, 15%) prepared by Examples 1-3 exhibited more excellent separation performance. Specifically, compared with the AO-PIM-1 base membrane, DZIF-8 performed more significantly than ZIF-8 in improving membrane selectivity, but the permeability decreased. This may be because the amidoxime groups in AO-PIM-1 coordinated with the metal sites exposed by DZIF-8, greatly enhancing the interfacial interaction between the two phases, thereby improving the gas screening performance, but also increasing the resistance of the gas channel, resulting in a decrease in permeability. In addition, the metal sites exposed by DZIF-8 provide additional propylene adsorption sites, further enhancing the selectivity of DMMMs. Specifically, compared with AO-PIM-1, the permeability of 10% DMMMs decreased by 55% and the selectivity increased by 200%; compared with 10% MMMs, the permeability decreased by 64% and the selectivity increased by 114%.

[0090] Table 1 shows the propylene propane permeability and selectivity of the gas separation membranes prepared in the control example and the example.

[0091]

Claims

1. A method for preparing a defective MOF-based self-microporous polymer mixed matrix membrane for efficient separation of propylene and propane, characterized in that: Here are the steps: (1) Synthesis of MOFs; Disperse metal salt A and 2-methylimidazole in the reaction medium respectively, quickly pour the metal salt A solution into the 2-methylimidazole solution and stir to react to obtain a milky white suspension; The mixture was centrifuged, washed, and centrifuged several times for purification, and dried in a vacuum oven to obtain MOF nanoparticles. Wherein, metal salt A is zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate; (2) Acid etching of MOF: Acid A is dissolved in solvent A to obtain a colorless transparent solution; the MOF nanoparticles synthesized in step (1) are dispersed in solvent A, and a uniform MOF suspension is obtained after ultrasonication; the colorless transparent solution is blended with the MOF suspension, stirred for reaction at a certain temperature, collected by centrifugation, washed with solvent A, centrifuged several times, and dried in a vacuum oven to obtain defective MOF particles after etching; Wherein, acid A is one or a mixture of two or more of cyanuric acid, citric acid, glycine, gallic acid, and methyl gallate; (3) Synthesis of amidoxime-based PIM-1: 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane, tetrafluoroterephthalonitrile and anhydrous potassium carbonate were added to a mixed solution of solvent B and solvent C, stirred at room temperature to fully disperse, and then reacted at a certain temperature under the atmosphere of protective gas A; after the reaction, the product was washed with solvent A, dissolved in solvent D and allowed to stand, and then solvent A was added to precipitate, and then washed with deionized water, and finally vacuum dried in a vacuum oven to obtain a purified PIM-1 polymer; the synthesized PIM-1 polymer was dissolved in solvent E, heated to dissolve under the atmosphere of protective gas A, and after the temperature gradually rose to the reaction temperature, 50 wt% hydroxylamine aqueous solution, and reflux reaction; after the reaction is completed, cool to room temperature, pour the reactant into solvent A for precipitation, vacuum filter and wash with solvent A, and finally vacuum dry in a vacuum oven to obtain flocculent or powdery AO-PIM-1 polymer; (4) Preparation of DMMM: The defective MOF synthesized in step (2) is activated in a vacuum drying oven and ultrasonically dispersed in solvent H to obtain a defective MOF dispersion; AO-PIM-1 is dissolved in solvent F; the AO-PIM-1 solution filtered through a microporous membrane filter is blended with the defective MOF dispersion, and the AO-PIM-1 solution is added to the defective MOF dispersion twice to prepare a casting solution, which is initially dispersed by ultrasound, stirred to be fully dispersed, and then ultrasonically defoamed. After standing, the solution is poured into a culture dish and allowed to stand in an oven at a certain temperature to volatilize the solvent to form a film.

2. The preparation method according to claim 1, characterized in that The specific process of synthesizing MOF in step (1) is as follows: The reaction medium is methanol and / or ethanol; The molar ratio of metal salt A to 2-methylimidazole is 1:2-16; The reaction temperature is 25°C; The centrifuge speed was 10,000 rpm and the centrifugation time was 10 min; The solvent used for washing was methanol; The drying temperature was 80°C and the drying time was 24 h.

3. The preparation method according to claim 1, characterized in that In step (2), Solvent A is methanol and / or ethanol; The molar ratio of acid A to MOF nanoparticles is 1:1-8; The reaction time is 12-36 h, and the reaction temperature is 25-80°C; The centrifuge speed was 10,000 rpm and the centrifugation time was 10 min; The drying temperature was 80°C and the drying time was 24 h.

4. The preparation method according to claim 1, characterized in that In step (3), The molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane, tetrafluoroterephthalonitrile and anhydrous potassium carbonate is 1:1:3; solvent B and solvent C are N,N-dimethylacetamide and toluene, respectively, with a mass ratio of 2:1; Solvent D is chloroform; Solvent E is tetrahydrofuran; Protective gas A is nitrogen; The reaction temperature for synthesizing the PIM-1 polymer was 155°C and the reaction time was 60 min; The drying temperature of PIM-1 for synthesizing PIM-1 polymer was 120 °C and the drying time was 24 h; The reaction temperature for synthesizing AO-PIM-1 polymer was 69 °C and the reaction time was 2 h; The drop rate of the hydroxylamine aqueous solution was 1 mL / min; The drying temperature of AO-PIM-1 was 120°C and the drying time was 24 h.

5. The preparation method according to claim 1, characterized in that In step (4), Wherein, solvent F is N,N-dimethylformamide and / or N,N-dimethylacetamide; The mass fraction of AO-PIM-1 polymer in the casting solution is 2-5 wt%; The stirring time is 12-24 h, and the ultrasonic time is 20 min; The solvent evaporation temperature is 50 °C and the evaporation time is 24 h.

6. The preparation method according to claim 1, characterized in that In step (4), Among them, the ultrasound time was 30 min; The stirring time is 12-24 h, and the standing time is 2 h; The oven temperature was 50 °C and the volatilization time was 24 h.

Images