A defect-free c-pims / mofs composite membrane with uniform distribution, a preparation method and applications thereof

Abstract

The application relates to a uniformly-distributed defect-free c-PIMs / MOFs composite membrane, a preparation method and application thereof, and belongs to the technical field of gas separation membrane technology. The application is a homogeneous membrane which comprises a modified PIMs matrix and MOFs nanoparticles, wherein the MOFs nanoparticles are uniformly embedded in the modified PIMs matrix and are composed of modified PIMs chain segment structures and MOFs and PIMs crosslinking structures; the PIMs matrix in the composite membrane has continuous cavities, and the MOFs have regular channels. First, a modified polymer PIMs is prepared; second, a MOFs seed solution is prepared; finally, a c-PIMs / MOFs composite membrane is prepared by solvent evaporation method and heat treatment of a PIMs / MOFs casting solution. The application is based on the solvent evaporation concept, the gas separation performance and long-term stability of the PIMs composite membrane are improved by optimizing the solvent evaporation conditions and regulating the interface compatibility between the PIMs and the MOFs; the interface compatibility between the PIMs and the MOFs can be improved, non-selective defects can be avoided, and the formation of the defect-free composite membrane can be promoted; selective and rapid transmission of the gas can be realized, and the preparation of the uniformly-distributed defect-free composite membrane can be further realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of gas separation membrane separation technology, and relates to a preparation method of a uniformly distributed defect-free c-PIMs / MOFs composite membrane. BACKGROUND

[0002] With the intensification of global climate change, carbon dioxide (CO2) capture and storage (CCS) technology has been increasingly valued. Industrial production and energy consumption are the main sources of CO2 emissions, and developing efficient CO2 capture technology has become an important measure to cope with climate change. Membrane separation technology is more attractive than traditional chemical absorption methods due to its low energy consumption, simple operation and environmental friendliness. In particular, self-polymerization microporous polymer membranes (PIMs) have become a research hotspot because their gas permeability is much higher than that of commercial polymer membranes.

[0003] In the process of improving the performance of PIMs membranes, combining nanofillers into the PIMs matrix to prepare mixed matrix membranes (MMMs) is an effective strategy to combine the excellent selectivity of nanofillers and the high gas permeability of PIMs. Metal-organic frameworks (MOFs) have shown excellent selectivity in gas separation due to their adjustable pore size, highly porous structure and controllable chemical composition. However, the agglomeration and deposition of MOF nanoparticles, as well as their poor interfacial compatibility with the PIMs matrix, result in non-selective voids and pores in the membrane, which seriously affect the gas separation performance of the membrane. Therefore, researchers have proposed various methods to adjust the surface chemical properties of MOFs, use interfacial agents, and geometrically regulate MOFs. However, achieving uniform dispersion of high loadings of MOFs in the PIMs matrix remains a challenge.

[0004] To solve the above problems, the present application uses a solvent evaporation method to prepare a uniformly distributed defect-free PIMs-MOFs mixed matrix membrane. By heat-treating the PIMs-MOFs casting solution, the growth environment of MOFs is regulated by constructing nanolimited spaces in the membrane. This method optimizes the distribution of MOF nanoparticles in the PIMs polymer matrix and improves the interfacial compatibility between PIMs and MOFs, thereby improving the gas separation performance of PIMs membranes. SUMMARY

[0005] The application aims to provide a c-PIMs / MOFs composite membrane with uniform distribution and no defects, solve the problem that it is difficult to prepare a high-performance aging-resistant PIMs membrane in the prior art, and provide a preparation method of the c-PIMs / MOFs composite membrane with uniform distribution and no defects.

[0006] In order to achieve the above-mentioned application purposes, the technical scheme of the application is as follows:

[0007] A c-PIMs / MOFs composite membrane with uniform distribution and no defects, the composite membrane is a homogeneous membrane, comprising a modified PIMs matrix and MOFs nanoparticles, wherein the MOFs nanoparticles are uniformly embedded in the modified PIMs matrix, and are specifically composed of a modified PIMs chain segment structure and a MOFs and PIMs cross-linking structure composite. The continuous cavities in the PIMs matrix and the regular pores in the MOFs in the composite membrane serve as gas selective transmission channels, the PIMs matrix and the MOFs nanoparticles have excellent interfacial compatibility, and the composite membrane has good gas separation performance and long-term stability.

[0008] Further, the thickness of the c-PIMs / MOFs composite membrane material is 50-150 μm.

[0009] A preparation method of a c-PIMs / MOFs composite membrane material with uniform distribution and no defects, the preparation method first prepares a modified polymer PIMs. Secondly, a MOFs seed solution is prepared. Finally, a PIMs / MOFs casting solution is heat-treated by a solvent evaporation method to construct a polymer chain limited space to control the growth space and distribution state of MOFs and prepare a c-PIMs / MOFs composite membrane. The casting solution of the composite membrane comprises modified PIMs, MOFs nanoparticles and a solvent; wherein the molar concentration ratio of the metal salt of the MOFs nanoparticles to the PIMs is 0.05-1. The preparation method comprises the following steps:

[0010] First step: preparing a modified polymer PIMs;

[0011] Step 1.1) Preparation of polymer PIM-1: Under nitrogen (N2) atmosphere, the reaction monomer 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane (TTSBI) was dissolved with tetrafluoroterephthalonitrile (TFTPN) and anhydrous potassium carbonate (K2CO3) in solvent A, and the mixture was poured into a three-necked flask and reacted at a temperature of 65-160℃ for 0.5-72h. The reaction mechanism of this step is: aromatic tetrol monomer TTSBI undergoes aromatic nucleophilic substitution reaction with fluorine-containing compound TFTPN under the catalysis of K2CO3 to form a high molecular weight soluble microporous polymer PIM-1. After the reaction is completed, the solution is cooled to room temperature and gradually poured into methanol to precipitate a fluorescent yellow solid. The obtained solid is dissolved in chloroform, and the solution is again poured into methanol for precipitation to obtain a polymer solid. This process is repeated several times to ensure the purity and high molecular weight of the polymer. The filtered polymer solid is poured into deionized water and stirred at 100℃ for 4h to completely remove the residual K2CO3. The collected yellow polymer is vacuum dried to obtain polymer PIM-1.

[0012] Step 1.2) Preparation of modified polymer PIMs;

[0013] The polymer PIM-1 obtained in step 1.1) is dissolved in solvent B under N2 atmosphere, and then modified solution A is added to the reaction solution, which is refluxed at 25-155℃ for 0.5-72h. After cooling to room temperature, the mixture is poured into solvent C to obtain a light yellow powder by filtration. The polymer product is washed with 500mL of ethanol for several times and then vacuum dried to obtain the modified polymer PIMs.

[0014] In step 1.1), 7.36g of TTSBI corresponds to the addition of 4-8g of TFTPN, 6.91-13.82g of K2CO3. The vacuum drying temperature is 60-120℃, and the time is 24-72h.

[0015] In step 1.1), the solvent A is one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide.

[0016] In step 1.2), the solvent B is one of tetrahydrofuran, deionized water, dichloromethane; and the solvent C is one or more of deionized water, methanol, ethanol.

[0017] In step 1.2), the modified solution A is one of hydroxylamine aqueous solution, concentrated sulfuric acid, chlorosulfonic acid.

[0018] The modified polymer PIMs in step 1.2) is one of amidoxime PIMs (AOPIM-1), carboxylic PIMs (PIM-COOH) and sulfonated PIMs (SPIM-1). Among them:

[0019] When the solvent B is tetrahydrofuran and the modified solution A is hydroxylamine aqueous solution, the obtained modified PIMs is AOPIM-1; when the solvent B is deionized water and the modified solution A is concentrated sulfuric acid, the obtained modified PIMs is PIM-COOH; when the solvent B is dichloromethane and the modified solution A is chlorosulfonic acid, the obtained modified PIMs is SPIM-1.

[0020] Second step: preparing MOFs seed solution;

[0021] Step 2.1) At room temperature, the metal salt is added to the solvent D to form a uniform metal salt solution under ultrasonic treatment at room temperature, and the concentration of the metal salt dispersion liquid is 0.05-3 g / L; the organic ligand is added to the solvent E to form a uniform organic ligand solution under ultrasonic treatment at room temperature, and the concentration of the organic ligand dispersion liquid is 0.05-36 g / L.

[0022] Step 2.2) The metal salt dispersion liquid and the organic ligand dispersion liquid obtained in step 2.1) are mixed, and the reaction mixture is poured into a three-necked flask, heated at 30-140℃ for 2-24h, and naturally cooled to room temperature to obtain the MOFs seed solution. In every 3 mL of the metal salt dispersion liquid, 3-60 mL of the organic ligand dispersion liquid is added.

[0023] In step 2.1), the solvent D is one of N,N-dimethylformamide, N-methylpyrrolidone and chloroform, and the solvent E is one of N,N-dimethylformamide, N-methylpyrrolidone and chloroform.

[0024] In step 2.1), the metal salt is one of zinc nitrate hexahydrate, zirconium chloride and copper nitrate trihydrate. The organic ligand is one of imidazole diformaldehyde, 2-amino terephthalic acid and trimesic acid.

[0025] In step 2.2), the MOFs in the obtained seed solution are one of ZIF-90, UiO-66-NH2 and HKUST-1. Among them: when the metal salt is zinc nitrate hexahydrate and the organic ligand is imidazole diformaldehyde, the obtained MOFs is ZIF-90; when the metal salt is zirconium chloride and the organic ligand is 2-amino terephthalic acid, the obtained MOFs is UiO-66-NH2; when the metal salt is copper nitrate trihydrate and the organic ligand is trimesic acid, the obtained MOFs is HKUST-1.

[0026] Step 3: Preparation of c-PIMs / MOFs composite membrane

[0027] The c-PIMs / MOFs composite membrane is prepared by heat treatment of the c-PIMs / MOFs composite membrane by solvent evaporation method, as follows:

[0028] Under N2 atmosphere, the MOFs seed solution obtained in Step 2 and the modified polymer PIMs obtained in Step 1 are dissolved in solvent F and poured into a three-necked flask, and stirred vigorously at a temperature of 50-200℃ for 1-12h to form a uniform PIMs / MOFs dispersion, wherein the molar concentration ratio of metal salt ions in the MOFs seed solution to PIMs is 0.05-1:1. Subsequently, the PIMs / MOFs dispersion is ultrasonically treated for 60-120min to remove bubbles. Finally, the PIMs / MOFs dispersion is cast into a super-flat quartz dish and placed in an oven, and after the solvent F is completely evaporated, the membrane is peeled off from the quartz dish and immersed in methanol for 24-48h to eliminate residual metal salts and ligands. The obtained c-PIMs / MOFs composite membrane is vacuum dried.

[0029] The reaction mechanism of this step is that the polymer and MOFs seed solution are mixed thoroughly and placed in a heating system, and the continuous evaporation of the solvent in the casting solution can concentrate the polymer chains. The limited space between the chains can limit the growth of MOFs, promote the formation of small-size MOF fillers and enhance the interfacial compatibility between PIMs-MOFs. In addition, the cross-linking reaction between MOFs and the polymer matrix can anchor the growth sites of MOFs and promote their uniform distribution in the membrane. The addition of MOFs can increase the gas selective permeation path in the membrane and improve the gas separation performance of the composite membrane. In this step: based on the solvent evaporation concept, the gas separation performance and long-term stability of the PIMs composite membrane are improved by optimizing the solvent evaporation conditions and regulating the interfacial compatibility between PIMs-MOFs. By regulating the evaporation rate of the solvent, the polymer and MOF filler can form good contact at the phase interface, enhancing the interaction and thus improving the interfacial compatibility between PIMs-MOFs, effectively avoiding non-selective defects and promoting the formation of defect-free composite membranes.

[0030] In the third step, the N2 purging speed is 5-30L / min. The oven temperature is 30-120℃, and the time is 24-72h. The solvent F is one of N,N-dimethylformamide, N-methyl pyrrolidone and chloroform. The vacuum drying temperature is 60-120℃, and the time is 24-72h.

[0031] The application of the uniform distribution defect-free c-PIMs / MOFs composite membrane material is used in gas separation, salt differential power generation, ion exchange and the like.

[0032] The beneficial effects of the present application are:

[0033] (1) The present application adopts solvent evaporation method to construct limited space between polymer chains to promote uniform distribution of small size MOFs particles. Specifically: in a high temperature environment, as the solvent in the PIMs-MOFs casting solution evaporates continuously, the limited space formed between the polymer chains limits the growth of MOFs, preventing it from aggregating into large particles, thereby promoting the formation of small size fillers. The dense polymer chain segment provides physical support for MOFs particles, preventing them from settling to the bottom due to gravity. In addition, the cross-linking bond between PIMs segment and MOFs particle helps to anchor the growth site of MOFs, further promoting the uniform dispersion of MOFs particles in the polymer matrix.

[0034] (2) Improve the crystallization growth efficiency of MOFs crystal particles in the membrane by MOFs pre-nucleation. Specifically: MOFs pre-nucleation can introduce MOFs growth sites in the PIMs-MOFs casting solution. In addition, by adjusting the pre-nucleation conditions, the growth rate of the crystal can be controlled, thereby improving the crystallinity and uniformity of MOFs in the PIMs-MOFs casting solution.

[0035] (3) Construction of defect-free PIMs-MOFs interface in the membrane. Specifically: by adjusting the evaporation rate of the solvent, the polymer and MOFs filler can form good contact at the interface, enhancing the interaction, thereby improving the interfacial compatibility between PIMs-MOFs, effectively avoiding non-selective defects, and promoting the formation of defect-free composite membranes.

[0036] (4) Functionalized MOFs have higher CO2 adsorption capacity, in addition, its unique microporous structure reduces the migration resistance of gas molecules in the membrane, further improving the gas separation performance of the composite membrane. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a scanning electron microscope image of c-AOPIM / ZIF-90 of Example 1.

[0038] Figure 2 is a scanning electron microscope image of c-PIM-COOH / UiO-66-NH2 of Example 2.

[0039] Figure 3 is a scanning electron microscope image of c-SPIM-1 / HKUST-1 of Example 3.

[0040] Figure 4 is a scanning electron microscope image of AOPIM / ZIF-90 of Comparative Example 1.

[0041] Figure 5are the Fourier transform infrared spectrograms of c-AOPIM / ZIF-90, AOPIM-1 and ZIF-90 of Example 1.

[0042] Figure 6 are the gas separation performance diagrams of Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in combination with examples. It should be understood that the technical solutions of the present application are described in detail below through examples, but the protection scope of the present application is not limited thereto.

[0044] Example 1: The method of the present application comprises the following steps:

[0045] First step: preparation of modified polymer PIMs;

[0046] 1.1) Preparation of polymer PIM-1: under N2 atmosphere, the reaction monomer TTSBI is dissolved in solvent A together with TFTPN and anhydrous K2CO3, and the mixture is poured into a three-necked flask and reacted at a temperature of 65℃ for 72h. After the reaction is completed, the solution is cooled to room temperature and gradually poured into methanol to precipitate a fluorescent yellow solid. The obtained solid is dissolved in chloroform, and the solution is again poured into methanol for precipitation to obtain a polymer solid. This process is repeated multiple times to ensure the purity and quality of the polymer. The filtered polymer solid is poured into deionized water and stirred at 100℃ for 4h to completely remove residual K2CO3. The collected yellow polymer is vacuum dried to obtain polymer PIM-1.

[0047] 1.2) Preparation of modified polymer PIMs;

[0048] The polymer PIM-1 obtained in step 1.1) is dissolved in solvent B under N2 atmosphere, and then modified solution A is added to the reaction solution, which is refluxed at 65℃ for 0.5h. After cooling to room temperature, the mixture is poured into solvent C to obtain a light yellow powder by filtration. The polymer product is washed with 500mL of ethanol multiple times and then vacuum dried to obtain the modified polymer PIMs.

[0049] In step 1.1), 7.36g of TTSBI of step 1.1) corresponds to the addition of 4g of TFTPN, 6.91g of K2CO3. The vacuum drying temperature is 60℃, and the time is 24h.

[0050] In step 1.1), the solvent A is N-methyl pyrrolidone.

[0051] In step 1.2), the solvent B is tetrahydrofuran; and solvent C is a mixture of ethanol and deionized water.

[0052] In the step 1.2), the modified solution A is a hydroxylamine aqueous solution.

[0053] In the step 1.2), the modified polymer PIMs is AOPIM-1.

[0054] Second step: preparing MOFs seed solution;

[0055] 2.1) At room temperature, the metal salt is added into the solvent D to form a uniform metal salt solution by ultrasonic treatment at room temperature, and a metal salt dispersion solution with a concentration of 0.05 g / L is prepared; the organic ligand is added into the solvent E to form a uniform organic ligand solution by ultrasonic treatment at room temperature, and an organic ligand dispersion solution with a concentration of 0.05 g / L is prepared.

[0056] 2.2) The metal salt dispersion solution and the organic ligand dispersion solution obtained in step 2.1) are mixed, and the reaction mixture is poured into a three-necked flask and heated at 30℃ for 24 h, and then naturally cooled to room temperature to obtain a MOFs seed solution. In the metal salt dispersion solution, 3 mL of the organic ligand dispersion solution is added for every 3 mL of the metal salt dispersion solution.

[0057] In the step 2.1), the solvent D is N,N-dimethylformamide, and the solvent E is N,N-dimethylformamide.

[0058] In the step 2.1), the metal salt is zinc nitrate hexahydrate, and the organic ligand is imidazole dimethylaldehyde.

[0059] In the step 2.2), the MOFs is ZIF-90.

[0060] Third step: preparing c-PIMs / MOFs composite membrane;

[0061] 3.1) The c-PIMs / MOFs composite membrane is heat treated by solvent evaporation method, specifically as follows:

[0062] The ZIF-90 seed solution from the second step and the AOPIM-1 solution from the first step were dissolved in solvent F and poured into a three-neck flask under N2 atmosphere and stirred vigorously at 200 °C for 1 h to form a homogeneous AOPIM-1 / ZIF-90 dispersion, where the molar ratio of metal salt ions to PIMs in the MOFs seed solution was 0.05:1. Subsequently, the AOPIM-1 / ZIF-90 dispersion was sonicated for 60 min to remove air bubbles. Finally, the AOPIM-1 / ZIF-90 dispersion was cast into a super flat quartz dish and placed in an oven, and the film was peeled off from the quartz dish after the solvent F was completely evaporated and immersed in methanol for 24 h to eliminate residual metal salts and ligands. The resulting composite film was vacuum dried and labeled as "c-AOPIM-1 / ZIF-90".

[0063] In the step 3.1), the N2 purging speed is 5 L / min.

[0064] In the step 3.1), the oven temperature is 120 °C and the time is 24 h.

[0065] In the step 3.1), the solvent F is N,N-dimethylformamide. The vacuum drying temperature is 120 °C and the time is 24 h.

[0066] In Example 1, the ZIF-90 crystals in the c-AOPIM-1 / ZIF-90 composite film are uniformly distributed in the AOPIM-1 matrix, the interface between the ZIF-90 crystals and the AOPIM-1 matrix has good compatibility, and no non-selective defect holes appear. The size of the ZIF-90 nanoparticles is about 150 nm, which indicates that the inter-chain confinement significantly limits the growth space of the ZIF-90 nanocrystals. In addition, the interaction between the amino groups in the AOPIM-1 segment and the aldehyde groups in the ZIF-90 promotes the uniform distribution of the ZIF-90 nanocrystals, realizing the composite structure of the defect-free c-AOPIM-1 / ZIF-90.

[0067] Example 2: The method of the present application comprises the following steps:

[0068] Step 1: Preparation of modified polymer PIMs;

[0069] 1.1) Preparation of polymer PIM-1: under N2 atmosphere, the reaction monomer TTSBI is dissolved with TFTPN and anhydrous K2CO3 in solvent A, and the mixture is poured into a three-necked flask, and reacted at a temperature of 120℃ for 4h. After the reaction is completed, the solution is cooled to room temperature and gradually poured into methanol to precipitate a fluorescent yellow solid. The obtained solid is dissolved in chloroform, and the solution is again poured into methanol for precipitation to obtain a polymer solid. This process is repeated several times to ensure the purity and quality of the polymer. The filtered polymer solid is poured into deionized water and stirred at 100℃ for 4h to completely remove residual K2CO3. The collected yellow polymer is vacuum dried to obtain polymer PIM-1.

[0070] 1.2) Preparation of modified polymer PIMs;

[0071] The polymer PIM-1 obtained in step 1.1) is dissolved in solvent B under N2 atmosphere, and then modified solution A is added to the reaction solution, and refluxed at 155℃ for 72h. After cooling to room temperature, the mixture is poured into solvent C to obtain a light yellow powder by filtration. The polymer product is washed with 500mL of ethanol several times and vacuum dried to obtain the modified polymer PIMs.

[0072] In step 1.1), 7.36g of TTSBI of step 1.1) corresponds to the addition of 6g of TFTPN, 10.37g of K2CO3. The vacuum drying temperature is 90℃, and the time is 36h.

[0073] In step 1.1), the solvent A is N,N-dimethylformamide.

[0074] In step 1.2), the solvent B is deionized water; and solvent C is deionized water.

[0075] In step 1.2), the modified solution A is concentrated sulfuric acid.

[0076] In step 1.2), the modified polymer PIMs is PIM-COOH.

[0077] Second step: preparation of MOFs seed solution;

[0078] 2.1) At room temperature, the metal salt is added to solvent D to form a uniform metal salt solution under ultrasonic conditions at room temperature, and a metal salt dispersion solution with a concentration of 1g / L is prepared; the organic ligand is added to solvent E to form a uniform organic ligand solution under ultrasonic conditions at room temperature, and an organic ligand dispersion solution with a concentration of 5g / L is prepared.

[0079] 2.2) Mix the metal salt dispersion and organic ligand dispersion obtained in step 2.1), pour the reaction mixture into a three-necked flask, heat at 120 °C for 12 h, and cool to room temperature naturally to obtain a MOFs seed solution. The organic ligand dispersion of 30 mL is added to every 3 mL of the metal salt dispersion.

[0080] In step 2.1), the solvent D is N-methylpyrrolidone, and the solvent E is N-methylpyrrolidone.

[0081] In step 2.1), the metal salt is zirconium chloride. The organic ligand is 2-aminoterephthalic acid.

[0082] In step 2.2), the MOFs are UiO-66-NH2.

[0083] Third step: preparation of c-PIMs / MOFs composite membrane;

[0084] 3.1) heat-treat the c-PIMs / MOFs composite membrane by solvent evaporation method, specifically as follows:

[0085] Under N2atmosphere, dissolve the UiO-66-NH2seed solution obtained in the second step and the PIM-COOH obtained in the first step in solvent F and pour into a three-necked flask, and form a uniform PIM-COOH / UiO-66-NH2dispersion under the condition of stirring at 100 °C for 6 h, wherein the molar ratio of metal salt ions in the MOFs seed solution to PIMs is 0.3:1. Then, ultrasonically treat the PIM-COOH / UiO-66-NH2dispersion for 90 min to remove air bubbles. Finally, cast the PIM-COOH / UiO-66-NH2dispersion into a super-flat quartz plate and place in an oven, and after the solvent F is completely evaporated, peel the membrane from the quartz plate, and immerse in methanol for 36 h to eliminate residual metal salt and ligand. Vacuum-dry the obtained composite membrane and mark it as “c-PIM-COOH / UiO-66-NH2”.

[0086] In step 3.1), the N2purge rate is 15 L / min.

[0087] In step 3.1), the oven temperature is 90 °C, and the time is 48 h.

[0088] In step 3.1), the solvent F is N-methylpyrrolidone. The vacuum-drying temperature is 90 °C, and the time is 48 h.

[0089] In Example 2, the UiO-66-NH2crystals in the c-PIM-COOH / UiO-66-NH2 composite film are uniformly distributed in the PIM-COOH matrix, the interface compatibility between the UiO-66-NH2crystals and the PIM-COOH matrix is good, and no non-selective defect holes appear. The size of the UiO-66-NH2nanoparticles is about 300 nm, which indicates that the chain confinement significantly limits the growth space of the UiO-66-NH2nanocrystals. In addition, the interaction between the carboxyl groups in the PIM-COOH segment and the amino groups in the UiO-66-NH2promotes the uniform distribution of the UiO-66-NH2nanocrystals, achieving a defect-free c-PIM-COOH / UiO-66-NH2 composite structure.

[0090] Example 3: The method of the present application comprises the following steps:

[0091] First step: preparation of modified polymer PIMs;

[0092] 1.1) Preparation of polymer PIM-1: under N2atmosphere, the reaction monomer TTSBI is dissolved with TFTPN and anhydrous K2CO3 in solvent A, and the mixture is poured into a three-necked flask and reacted at a temperature of 160℃ for 0.5h. After the reaction is completed, the solution is cooled to room temperature and gradually poured into methanol to precipitate a fluorescent yellow solid. The obtained solid is dissolved in chloroform, and the solution is again poured into methanol for precipitation to obtain a polymer solid. This process is repeated several times to ensure the purity and quality of the polymer. The filtered polymer solid is poured into deionized water and stirred at 100℃ for 4h to completely remove residual K2CO3. The collected yellow polymer is vacuum dried to obtain polymer PIM-1.

[0093] 1.2) Preparation of modified polymer PIMs;

[0094] The polymer PIM-1 obtained in step 1.1) is dissolved in solvent B under N2atmosphere, and then modified solution A is added to the reaction solution, which is refluxed at 25℃ for 9h. After cooling to room temperature, the mixture is poured into solvent C to obtain a light yellow powder by filtration. The polymer product is washed with 500mL of ethanol several times and then vacuum dried to obtain the modified polymer PIMs.

[0095] In step 1.1), 8g of TFTPN and 13.82g of K2CO3 are added for every 7.36g of TTSBI in step 1.1). The vacuum drying temperature is 120℃, and the time is 72h.

[0096] In step 1.1), the solvent A is N,N-dimethylacetamide.

[0097] In the step 1.2), the solvent B is dichloromethane; the solvent C is methanol.

[0098] In the step 1.2), the modified solution A is chlorosulfonic acid.

[0099] In the step 1.2), the modified polymer PIMs is SPIM-1.

[0100] Second step: preparing MOFs seed solution;

[0101] 2.1) At room temperature, the metal salt is added into the solvent D to form a uniform metal salt solution by ultrasonic treatment at room temperature, and a metal salt dispersion solution with a concentration of 3g / L is prepared; the organic ligand is added into the solvent E to form a uniform organic ligand solution by ultrasonic treatment at room temperature, and an organic ligand dispersion solution with a concentration of 36g / L is prepared.

[0102] 2.2) The metal salt dispersion solution and the organic ligand dispersion solution obtained in step 2.1) are mixed, and the reaction mixture is poured into a three-necked flask and heated at 140℃ for 2h, and then naturally cooled to room temperature to obtain the MOFs seed solution. In the metal salt dispersion solution, 60mL of the organic ligand dispersion solution is added for every 3mL of the metal salt dispersion solution.

[0103] In the step 2.1), the solvent D is chloroform, and the solvent E is chloroform.

[0104] In the step 2.1), the metal salt is copper nitrate trihydrate, and the organic ligand is trimesic acid.

[0105] In the step 2.2), the MOFs is HKUST-1.

[0106] Third step: preparing c-PIMs / MOFs composite membrane;

[0107] 3.1) The c-PIMs / MOFs composite membrane is heat treated by solvent evaporation method, specifically as follows:

[0108] The HKUST-1 seed solution obtained in the second step and the SPIM-1 solution obtained in the first step were dissolved in solvent F and poured into a three-necked flask under N2 atmosphere and stirred vigorously at a temperature of 50°C for 12 h to form a homogeneous SPIM-1 / HKUST-1 dispersion, wherein the molar ratio of metal salt ions to PIMs in the HKUST-1 seed solution was 1:1. Subsequently, the SPIM-1 / HKUST-1 dispersion was ultrasonically treated for 120 min to remove air bubbles. Finally, the SPIM-1 / HKUST-1 dispersion was cast into a super-flat quartz dish and placed in an oven, and after the solvent F was completely evaporated, the film was peeled off from the quartz dish and immersed in methanol for 48 h to eliminate residual metal salts and ligands. The resulting composite film was vacuum dried and labeled as "c-SPIM-1 / HKUST-1".

[0109] In the step 3.1), the N2 purging speed is 30 L / min.

[0110] In the step 3.1), the oven temperature is 30°C, and the time is 72 h.

[0111] In the step 3.1), the solvent F is chloroform. The vacuum drying temperature is 60°C, and the time is 72 h.

[0112] In Example 2, the HKUST-1 crystals in the c-SPIM-1 / HKUST-1 composite film are uniformly distributed in the SPIM-1 matrix, the interface compatibility between the HKUST-1 crystals and the SPIM-1 matrix is good, and no non-selective defect holes appear. The size of the HKUST-1 nanoparticles is about 500 nm, which indicates that the inter-chain confinement significantly limits the growth space of the HKUST-1 nanocrystals. In addition, the interaction between the sulfonic acid groups in the SPIM-1 segment and the hydroxyl groups in the HKUST-1 promotes the uniform distribution of the HKUST-1 nanocrystals, realizing the composite structure of the defect-free c-SPIM-1 / HKUST-1.

[0113] Comparative Example 1: Compared with Example 1, the difference is that it is not prepared by the solvent evaporation method, and other conditions are the same as those in Example 1.

[0114] The specific steps are as follows:

[0115] First step: preparation of modified polymer PIMs;

[0116] 1.1) Preparation of polymer PIM-1: under N2 atmosphere, the reaction monomer TTSBI is dissolved with TFTPN and anhydrous K2CO3 in solvent A, and the mixture is poured into a three-necked flask, and reacted at a temperature of 65℃ for 72h. After the reaction is completed, the solution is cooled to room temperature and gradually poured into methanol to precipitate a fluorescent yellow solid. The obtained solid is dissolved in chloroform, and the solution is again poured into methanol for precipitation to obtain a polymer solid. This process is repeated several times to ensure the purity and quality of the polymer. The filtered polymer solid is poured into deionized water and stirred at 100℃ for 4h to completely remove residual K2CO3. The collected yellow polymer is vacuum dried to obtain polymer PIM-1.

[0117] 1.2) Preparation of modified polymer PIMs;

[0118] The polymer PIM-1 obtained in step 1.1) is dissolved in solvent B under N2 atmosphere, and then the modified solution A is added to the reaction solution, and refluxed at 65℃ for 0.5h. After cooling to room temperature, the mixture is poured into solvent C to obtain a light yellow powder by filtration. The polymer product is washed with 500mL of ethanol several times and vacuum dried to obtain the modified polymer PIMs.

[0119] In step 1.1), 7.36g of TTSBI of step 1.1) corresponds to the addition of 4g of TFTPN, 6.91g of K2CO3. The vacuum drying temperature is 60℃, and the time is 24h.

[0120] In step 1.1), the solvent A is N-methylpyrrolidone.

[0121] In step 1.2), the solvent B is tetrahydrofuran; and the solvent C is a mixture of ethanol and deionized water.

[0122] In step 1.2), the modified solution A is an aqueous hydroxylamine solution.

[0123] In step 1.2), the modified polymer PIMs is AOPIM-1.

[0124] Second step: preparation of MOFs seed solution;

[0125] 2.1) At room temperature, the metal salt is added to solvent D to form a uniform metal salt solution under ultrasonic condition at room temperature, and the concentration is configured to be 0.05g / L of metal salt dispersion liquid; the organic ligand is added to solvent E to form a uniform organic ligand solution under ultrasonic condition at room temperature, and the concentration is configured to be 0.05g / L of organic ligand dispersion liquid.

[0126] 2.2) Mix the metal salt dispersion and organic ligand dispersion obtained in step 2.1), pour the reaction mixture into a three-necked flask, heat at 30 °C for 24 h, and cool to room temperature naturally to obtain a MOFs seed solution. The organic ligand dispersion of 3 mL is added to every 3 mL of the metal salt dispersion.

[0127] In step 2.1), the solvent D is N,N-dimethylformamide, and the solvent E is N,N- dimethylformamide.

[0128] In step 2.1), the metal salt is zinc nitrate hexahydrate, and the organic ligand is imidazole dimethylaldehyde.

[0129] In step 2.2), the MOFs are ZIF-90.

[0130] Third step: preparation of PIMs / MOFs composite membrane;

[0131] 3.1) heat treatment of PIMs / MOFs composite membrane by solvent evaporation method, specifically as follows:

[0132] Under N2 atmosphere, the ZIF-90 seed solution obtained in the second step and the AOPIM-1 obtained in the first step are dissolved in solvent F and poured into a sample bottle and stirred vigorously for 1 h to form a uniform AOPIM-1 / ZIF-90 dispersion, wherein the molar ratio of metal salt ions in the MOFs seed solution to PIMs is 0.05:1. Subsequently, the AOPIM-1 / ZIF-90 dispersion is ultrasonically treated for 60 min to remove bubbles. Finally, the AOPIM-1 / ZIF-90 dispersion is cast into a super-flat quartz plate and placed in an oven, and after the solvent F is completely evaporated, the membrane is peeled off from the quartz plate and immersed in methanol for 24 h. The obtained composite membrane is vacuum dried and labeled as “AOPIM-1 / ZIF-90”.

[0133] In step 3.1), the N2 blowing speed is 5 L / min.

[0134] In step 3.1), the oven temperature is 120 °C, and the time is 24 h.

[0135] In step 3.1), the solvent F is N,N-dimethylformamide. The vacuum drying temperature is 120 °C, and the time is 24 h.

[0136] In Comparative Example 1, the ZIF-90 crystals in the AOPIM-1 / ZIF-90 composite membrane mainly distributed at the bottom of the AOPIM-1 matrix, and the size of the ZIF-90 nanoparticles was about 1 μm. This indicates that in the low-viscosity casting solution, the sparsely arranged polymer segments are difficult to support the nanoparticles, so the large-size ZIF-90 is deposited at the bottom of the composite membrane under the action of gravity.

[0137] The c-PIMs / MOFs composite membranes prepared in the above examples were subjected to CO2, N2, CH4flux tests, and the results are shown in the following table:

[0138] Table 1. Gas separation performance of examples and comparative examples

[0139]

[0140] As can be seen from the data in Table 1, the c-PIMs / MOFs composite membranes obtained by the present application have good gas separation performance. By comparing Examples 1-3 treated by the solvent evaporation method with Comparative Example 1 not treated by the solvent evaporation method, it can be seen that the CO2fluxes in Examples 1-3 are all above 1509.48 Barrer, and are all improved to a certain extent relative to Comparative Example 1. This is because the uniform distribution of MOFs in the composite membrane provides a fast gas transmission path, so that the gas molecules can more easily pass through the composite membrane. The ideal selectivity of CO2 / N2and CO2 / CH4in Examples 1-3 is increased by nearly 1.3-3.6 times relative to Comparative Example 1. This is because after the solvent evaporation treatment, the interfacial compatibility between the MOFs nanoparticles and the polymer matrix is improved, and the interfacial defects are reduced, which helps to improve the selective permeation of gas molecules. The combination of the solvent evaporation method and the MOFs anchoring growth can construct a confinement between the polymer segments, thereby avoiding the excessive growth of the MOFs crystals and promoting the formation of smaller nanoparticles, which helps to reduce the interfacial defects in the membrane. The interaction between the MOFs particles and the polymer segments effectively anchors the growth sites of the MOFs, and promotes the uniform distribution of the MOFs particles in the membrane. In addition, the microporous structure of the MOFs in the membrane provides an additional selective gas transmission channel, which significantly improves the separation efficiency of CO2gas. Therefore, this improved solvent evaporation method as a synthesis technique has significant potential to construct a uniformly distributed and defect-free separation membrane in various polymers.

[0141] The method is based on the concept of solvent evaporation, by optimizing the solvent evaporation conditions and regulating the interfacial compatibility between PIMs-MOFs, the gas separation performance and long-term stability of PIMs composite membrane are improved. In a high temperature environment, as the solvent in the PIMs-MOFs casting solution evaporates continuously, the confined space formed between the polymer chains limits the growth of MOFs, preventing them from aggregating into large particles, thereby promoting the formation of small size fillers. The dense polymer chain segment provides physical support for MOFs particles, preventing them from settling to the bottom due to gravity. By pre-nucleating MOFs, MOFs growth sites can be introduced into the PIMs-MOFs casting solution. In addition, by adjusting the pre-nucleation conditions, the growth rate of the crystal can be controlled, thereby improving the crystallinity and uniformity of MOFs in the PIMs-MOFs casting solution. The cross-linking bond between PIMs segment and MOFs particle helps to anchor the growth site of MOFs, further promoting the uniform dispersion of MOFs particles in the polymer matrix. By adjusting the evaporation rate of the solvent, the polymer and MOFs filler can form good contact at the phase interface, enhancing the interaction, thereby improving the interfacial compatibility between PIMs-MOFs, effectively avoiding non-selective defects, and promoting the formation of defect-free composite membranes. Therefore, the defect-free PIMs-MOFs cross-linked structure provides an efficient gas separation mass transfer path in the composite membrane, realizing the selective and rapid transfer of gas, thereby further realizing the preparation of uniformly distributed and defect-free composite membranes.

[0142] The above-described embodiments only express the implementation of the present application, but cannot be interpreted as limiting the scope of the patent of the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application.

Claims

1. A uniformly distributed, defect-free c-PIMs / MOFs composite membrane, characterized in that, The composite membrane is a homogeneous membrane comprising a modified PIMs matrix and MOF nanoparticles, wherein the MOF nanoparticles are uniformly embedded in the modified PIMs matrix, specifically composed of a modified PIMs segment structure and a cross-linked structure of MOFs and PIMs; the composite membrane has continuous cavities within the PIMs matrix and regular channels within the MOFs. Includes the following steps: Step 1: Preparation of modified polymer PIMs; Step 1.1) Preparation of polymer PIM-1: Under an inert atmosphere, the reactive monomers 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI), tetrafluoroterephthalonitrile (TFTPN), and anhydrous potassium carbonate (K2CO3) were dissolved in solvent A and reacted at 65~160 °C for 0.5~72 h. After the reaction was completed, post-treatment was performed to obtain polymer PIM-1. Step 1.2) Preparation of modified polymer PIMs; The polymer PIM-1 obtained in step 1.1) is dissolved in solvent B under an inert atmosphere, and then modified solution A, which is concentrated sulfuric acid or chlorosulfonic acid, is added. The mixture is refluxed at 25~155 °C for 0.5~72 h. After cooling to room temperature, the mixture is poured into solvent C to obtain a light yellow powder. After vacuum drying, the modified polymer PIMs is obtained. Step 2: Prepare MOF seed solution; Step 2.1) At room temperature, add the metal salt to solvent D to prepare a metal salt dispersion with a concentration of 0.05~3 g / L; add the organic ligand to solvent E to prepare an organic ligand dispersion with a concentration of 0.05~36 g / L; the metal salt is zinc nitrate hexahydrate or copper nitrate trihydrate; the organic ligand is imidazole dicarboxaldehyde or trimellitic acid; Step 2.2) Mix the metal salt dispersion and organic ligand dispersion obtained in Step 2.1), heat at 30~140 °C for 2~24 h, and cool naturally to room temperature to obtain MOF seed solution; add 3~60 mL of organic ligand dispersion to every 3 mL of metal salt dispersion; the MOFs in the obtained seed solution are ZIF-90 or HKUST-1; Step 3: Heat-treat the c-PIMs / MOFs composite membrane using a solvent evaporation method, as detailed below: Under an inert atmosphere, the MOFs seed solution from the second step is dissolved and mixed with the modified polymer PIMs from the first step, and stirred vigorously at 50~200 °C for 1~12 h to form a uniform PIMs / MOFs dispersion, which is then subjected to ultrasonic treatment. The molar ratio of metal salt ions to PIMs in the MOFs seed solution is 0.05~1:

1. The PIMs / MOFs dispersion is used as a casting solution for casting and oven drying. After the solvent F is completely evaporated, the film is peeled off and vacuum dried to obtain the c-PIMs / MOFs composite film.

2. The uniformly distributed, defect-free c-PIMs / MOFs composite membrane according to claim 1, characterized in that, The thickness of the c-PIMs / MOFs composite membrane material is 50-150 μm.

3. The uniformly distributed, defect-free c-PIMs / MOFs composite membrane according to claim 1, characterized in that, In the first step described above: In step 1.1), for every 7.36 g of TTSBI, 4~8 g of TFTPN and 6.91~13.82 g of K2CO3 are added. In step 1.2), solvent B is deionized water or dichloromethane; In step 1.2), the modified polymer PIMs obtained are carboxylated PIMs or sulfonated PIMs.

4. The uniformly distributed, defect-free c-PIMs / MOFs composite membrane according to claim 3, characterized in that, When solvent B is deionized water and modified solution A is concentrated sulfuric acid, the obtained modified PIMs are PIM-COOH; when solvent B is dichloromethane and modified solution A is chlorosulfonic acid, the obtained modified PIMs are SPIM-1.

5. The uniformly distributed, defect-free c-PIMs / MOFs composite membrane according to claim 1, characterized in that: In step 1.1), solvent A is one of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; the vacuum drying temperature is 60~120 °C, and the time is 24~72 h. In step 1.2), solvent C is one or more of deionized water, methanol, and ethanol; The post-processing in step 1.1) is as follows: after cooling the reaction solution to room temperature, methanol is poured in to obtain a precipitate. The precipitate is dissolved and then methanol is poured in again to remove the precipitate. This process is repeated several times and then filtered to obtain a polymer solid. The solid is then poured into deionized water, stirred, filtered, and vacuum dried to obtain polymer PIM-1. In step 2.1), solvent D is one of N,N-dimethylformamide, N-methylpyrrolidone, and chloroform, and solvent E is one of N,N-dimethylformamide, N-methylpyrrolidone, and chloroform. In the third step, the inert atmosphere is N2 with a purging rate of 5-30 L / min; the oven drying temperature is 30-120 °C for 24-72 h; the solvent F is one of N,N-dimethylformamide, N-methylpyrrolidone, and chloroform; and the vacuum drying temperature is 60-120 °C for 24-72 h.

6. An application of the uniformly distributed, defect-free c-PIMs / MOFs composite membrane according to claim 1 or 2, characterized in that, Used in gas separation, salinity gradient power generation, and ion exchange systems.

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