Cross-linked mixed matrix membrane based on nano-composite filler and preparation method of cross-linked mixed matrix membrane

Abstract

The invention belongs to the technical field of membrane separation and carbon capture, and particularly relates to a cross-linked mixed matrix membrane based on core-shell structure composite filler as well as a preparation method and application of the cross-linked mixed matrix membrane. The invention provides the preparation method of the cross-linked mixed matrix membrane of the nano composite filler based on the core-shell structure, and the cross-linked mixed matrix membrane prepared by the method can simultaneously realize high CO2 permeability and high selectivity and shows good large-scale application potential.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation and carbon capture technology, specifically relating to a cross-linked hybrid matrix membrane based on a core-shell structure composite filler, its preparation method, and its application. Background Technology

[0002] With the rapid increase in atmospheric carbon dioxide (CO2) concentration, developing efficient carbon capture and storage technologies has become an urgent task in addressing global climate change. Among numerous separation technologies, membrane separation is considered a highly promising solution due to its advantages such as low energy consumption, high modularity, and ease of operation.

[0003] Currently, while commercially available polymer membrane materials are easy to process, their separation performance is limited by the inherent "trade-off" between permeability and selectivity, namely the Robeson upper limit, and they generally suffer from physical aging and plasticization problems. To overcome this bottleneck, self-porous polymers (PIMs) have emerged. Among them, PIM-1, due to its rigid ladder-like framework and twisted molecular structure, can generate high free volume and interconnected micropores, exhibiting extremely high CO2 permeability, and has become a research hotspot. However, the selectivity of PIM-1 membranes for gas pairs such as CO2 / N2 is still insufficient, and its loosely stacked segments lead to severe physical aging, causing separation performance to decline over time. To improve its selectivity and stability, crosslinking is considered an effective modification strategy. However, conventional crosslinking methods, such as UV crosslinking or thermal crosslinking, while improving stability, significantly sacrifice the inherent high permeability of PIM-1, with gas permeability decreasing by 50% to 85%, creating a new challenge of "gaining one at the expense of the other."

[0004] To compensate for the permeability loss caused by crosslinking, introducing porous fillers (such as metal-organic frameworks (MOFs) into the pre-crosslinked PIM-1 matrix to prepare crosslinked hybrid matrix membranes is a feasible strategy. However, this strategy faces a fundamental challenge: nanofillers are prone to agglomeration in polymers and have poor interfacial compatibility with the polymer matrix, easily forming non-selective interfacial defects. This problem is further amplified during subsequent crosslinking heat treatment, as the difference in thermal expansion coefficients between the filler and the polymer generates significant internal stress, inducing more defects. For example, KR20250059978A discloses coating the surface of MOF particles with polymer materials or surfactants to improve the interaction between the filler and the polymer matrix. However, these methods still suffer from poor compatibility and differences in thermal expansion coefficients between the filler and the coating layer, failing to fundamentally solve the problem. Therefore, the key to solving the problem lies in establishing a strong chemical bond between the filler and the polymer matrix, transforming the filler from a passive additive into an active crosslinking node. However, how to design fillers with both good compatibility and reactive functional groups to achieve a stable multi-level covalent interface remains a major challenge for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a cross-linked hybrid matrix membrane based on a core-shell structured nanocomposite filler. The cross-linked hybrid matrix membrane prepared by this method can simultaneously achieve high CO2 permeability and high selectivity, and shows good potential for large-scale application.

[0006] First, the present invention provides a cross-linked mixed matrix membrane based on nanocomposite fillers, which includes a PIM-1 polymer matrix and nanocomposite fillers blended in the polymer matrix. The nanocomposite fillers have a core-shell structure and are self-assembled by an amino-functionalized metal-organic framework material MOF-NH2 and a carboxyl-functionalized PIM-1 polymer cPIM-1 through hydrogen bonding. The polymer matrix and the nanocomposite fillers are connected by covalent bonds.

[0007] The MOF-NH2 is selected from one or more of ZIF-8-NH2, UiO-66-NH2 or MIL-125-NH2.

[0008] The shell thickness of the nanocomposite filler is 2-20 nm, and the particle size of the MOF-NH2 core is 10-1000 nm.

[0009] The mass fraction of the nanocomposite filler in the PIM-1 polymer matrix is ​​0.5-40 wt%.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned cross-linked hybrid matrix membrane based on nanocomposite fillers, comprising the following steps: (1) MOF-NH2 was prepared by using a synthesis solution containing amino organic ligands, and PIM-1 polymer was partially carboxylated by acid hydrolysis to obtain carboxylated polymer cPIM-1; (2) The MOF-NH2 and cPIM-1 are mixed in an organic solvent and self-assembled by hydrogen bonding to form a cPIM-1@MOF-NH2 composite filler with a core-shell structure; (3) The cPIM-1@MOF-NH2 composite filler is dispersed in a PIM-1 polymer solution to form a casting solution, and a mixed matrix membrane is prepared. (4) The mixed matrix membrane is heat-treated in an inert atmosphere to cause a multi-level covalent cross-linking reaction between the polymer matrix and the composite filler to form a cross-linked mixed matrix membrane.

[0011] In step (1), the amino organic ligand is selected from 2-aminobenzimidazole and 2-aminoterephthalic acid; the molar ratio of the original organic ligand to the amino organic ligand in the synthesis solution is 0-10:1; the proportion of amino ligand in the MOF-NH2 in the precursor solution is 10-100 wt%; the conversion rate of cyano groups to carboxyl groups in the carboxylated polymer cPIM-1 segment is 30%-100%, more preferably 40%-60%.

[0012] In step (2), MOF-NH2 and cPIM-1 are mixed in a mass ratio of 1-10:1, and the organic solvent is selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0013] In step (3), the mass content of cPIM-1@MOF-NH2 composite filler in the casting solution is 0.5-40 wt%. The preparation method of the mixed matrix membrane is either casting or phase inversion.

[0014] In step (4), the inert atmosphere is nitrogen, argon, or helium, wherein the oxygen concentration is controlled to be below 200 ppm; the heating procedure for the heat treatment is as follows: from room temperature at 5°C / min -1 The heating rate was increased to 200℃, held at 200℃ for 60-120 minutes, and then at 2.5℃ for 1 minute. -1 The temperature was lowered to 335°C, and finally reduced to 0.2°C for 1 minute. -1 The reaction temperature is then raised to 300-400℃ and maintained at the highest temperature for 30-720 minutes.

[0015] Finally, the present invention also provides an application of the above-mentioned cross-linked hybrid matrix membrane, the application including CO2 capture, natural gas purification and industrial separation of carbon-containing gases.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: First, this invention successfully achieves defect-free interface integration between the filler and the matrix through a core-shell structured composite filler design and a thermal crosslinking process. Specifically, the core MOF-NH2 of the nanocomposite filler is linked to the carboxyl-functionalized PIM-1 polymer cPIM-1 via hydrogen bonds. The cPIM-1 shell of the nanocomposite filler exhibits excellent initial compatibility with the PIM-1 matrix, ensuring uniform dispersion of the filler. Furthermore, the covalent bonds formed during heat treatment achieve "molecular welding," constructing a robust "filler-shell-matrix" covalent network. This establishes a strong chemical bond between the filler and the polymer matrix, transforming the filler from a passive additive into an active crosslinking node. This fundamentally solves the problems of filler agglomeration and interface defects, effectively alleviates internal stress during heat treatment, significantly improves the physicochemical stability of the crosslinked mixed matrix membrane, and extends the membrane's service life.

[0017] Secondly, the preparation method provided by this invention also synergistically optimizes the separation performance of the separation membrane, overcoming the traditional trade-off effect. The cross-linked dense polymer matrix enhances intrinsic selectivity, while the MOF core fixed by the covalent network serves as an effective molecular sieving channel, establishing a "tandem selectivity" transport mechanism, enabling gas separation performance to exceed the Robeson limit and achieving a simultaneous improvement in permeability and selectivity.

[0018] Furthermore, the preparation method provided by this invention has good universality and scalability. By adjusting the MOF type and film formation process, the performance characteristics of the membrane can be flexibly adjusted. Moreover, this method is compatible with mature processes such as dip-coating, and has successfully prepared large-area high-performance thin-film composite membranes, showing good prospects for industrial application. Attached Figure Description

[0019] Figure 1 The temperature rise program diagrams are shown for the heat treatment of the cross-linked mixed matrix membranes prepared in Examples 1-4 and Comparative Example 2. Figure 2 Transmission electron microscopy (TEM) image of the cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1. Figure 3 Fourier transform infrared (FTIR) spectrum of cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1. Figure 4 A cross-sectional scanning electron microscope image of the cross-linked hybrid matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1; Figure 5 The cross-linked molecular structure diagram of the cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1 is shown. Figure 6 A cross-sectional scanning electron microscope image of the asymmetric cross-linked hybrid matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 4; Figure 7 A cross-sectional scanning electron microscope image of the cross-linked hybrid matrix membrane based on ZIF-8-NH2 nanofiller prepared for Comparative Example 2; Figure 8 The graph shows the change in CO2 / N2 separation performance of the cross-linked mixed matrix membrane prepared in Example 1 as the loading of cPIM-1@ZIF-8-NH2 nanocomposite filler increases; Figure 9 The graph shows the change in CO2 / N2 separation performance of the crosslinked mixed matrix membrane prepared in Example 1 as crosslinking temperature and time increase; Figure 10 The figure shows a comparison of the CO2 / N2 separation performance of the cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1, the cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Comparative Example 1, and the cross-linked mixed matrix membrane based on single ZIF-8-NH2 filler prepared in Comparative Example 2. Figure 11 The figure shows the CO2 / N2 separation performance of three cross-linked mixed matrix membranes based on different nanocomposite fillers prepared in Examples 1-3. Figure 12 The image shows the CO2 / CH4 separation performance of the asymmetric cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 4. Detailed Implementation

[0020] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0021] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0022] In the following description, the PIM-1 polymer was synthesized by a low-temperature polycondensation reaction of equimolar amounts of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirodiindane (TTSBI) and 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN): TTSBI (5.1 g, 15 mmol), TFTPN (3.5 g, 15 mmol), and anhydrous N,N-dimethylformamide solvent (100 mL) were added to a 250 mL dry three-necked flask. After the monomers were dissolved, finely powdered anhydrous potassium carbonate (45 mmol, 6.22 g) was added. The reaction was stirred at 65°C under a nitrogen atmosphere for 72 hours. After the reaction was completed, the reaction solution was poured into 800 mL of water to precipitate the polymer. After filtration and drying, the polymer was dissolved in chloroform (100 mL) and then precipitated again in methanol (600 mL). This dissolution-precipitation step was repeated once. The obtained PIM-1 polymer was washed sequentially with 1,4-dioxane (120 mL), acetone (120 mL), deionized water (120 mL), and excess methanol. The final product was dried in a vacuum oven at 120°C for 24 hours.

[0023] In the following description, carboxylated PIM-1 (cPIM-1) was synthesized via acid hydrolysis. PIM-1 (1 g), deionized water (60 mL), acetic acid (20 mL), and sulfuric acid (60 mL) were added to a 250 mL round-bottom flask equipped with a condenser, and the mixture was stirred at 150°C for 36 hours. After the reaction was complete, the brownish-yellow powder was filtered and washed, then dispersed in 300 mL of deionized water. 7-8 drops of sulfuric acid were added, and the mixture was refluxed at 100°C for 12 hours. Finally, the mixture was filtered and dried under vacuum at 120°C overnight to obtain the final product.

[0024] Example 1 The method for preparing the cross-linked hybrid matrix membrane based on nanocomposite fillers includes: Synthesis of ZIF-8-NH2: 2-Methylimidazole and 2-aminobenzimidazole (total 10 mmol) were dissolved in methanol (25 mL), and zinc nitrate hexahydrate (1.25 mmol, 0.37 g) was dissolved in methanol (25 mL). The two solutions were mixed and stirred at room temperature for 3 hours. The resulting crystals were centrifuged and washed three times with methanol to remove unreacted ligands. Finally, the crystals were dried under vacuum at 60°C for 12 hours to obtain a white powder of ZIF-8-NH2. Specifically, the amount of 2-aminobenzimidazole used in the synthesis of ZIF-8-NH2 accounted for 20% of the total molar amount of the ligands.

[0025] Preparation of cPIM-1@ZIF-8-NH2 nanocomposite filler: cPIM-1 (40 mg) was dissolved in tetrahydrofuran (4 mL), and ZIF-8-NH2 (40 mg) was dispersed in tetrahydrofuran (4 mL). The mixture was stirred at room temperature for 30 minutes. After the reaction, the solid product was separated by centrifugation and washed twice with tetrahydrofuran to remove unreacted polymer. Subsequently, the cPIM-1@ZIF-8-NH2 particles were washed three times with chloroform to replace the tetrahydrofuran solvent, finally preparing a 10 mg / g solution. -1 A cPIM-1@ZIF-8-NH2 / CHCl3 dispersion was prepared to prevent particle agglomeration during drying. The cPIM-1@ZIF-8-NH2 solid powder, washed with tetrahydrofuran, was directly vacuum-dried at 60°C for characterization.

[0026] Preparation of cross-linked hybrid matrix membrane based on nanocomposite filler: PIM-1 (0.3 g) was dissolved in chloroform (10 g), and after complete dissolution, it was filtered through a PTFE filter (1 μm) to remove solid impurities. An appropriate amount of cPIM-1@ZIF-8-NH2 / CHCl3 dispersion was added according to the filling amount to form a film-forming solution, which was then thoroughly mixed on a tubular mixer. The solution was then evacuated to remove air bubbles. The final film-forming solution was poured into a flat-bottomed petri dish using a casting method, and the dish was placed in a glove bag filled with chloroform vapor. After the solvent had completely evaporated, the petri dish was removed, and the film was obtained by peeling with deionized water. After vacuum drying at 120°C for 24 hours, a self-supporting cPIM-1@ZIF-8-NH2 / PIM-1 hybrid matrix membrane was obtained. The membrane sample was sandwiched between two quartz plates in a ceramic boat and then placed in a tube furnace. Before heat treatment, the tubular furnace was evacuated three times and purged with nitrogen to reduce the oxygen concentration to below 100 ppm, followed by 100 mL min. -1 The mixed matrix membrane was heat-treated at a nitrogen flow rate; the heating procedure is as follows: Figure 1 After cooling to room temperature, a cross-linked mixed matrix membrane is obtained.

[0027] Example 2 The method in this embodiment differs from that in Embodiment 1 only in that UiO-66-NH2 is used as the MOF core of the nanocomposite filler, wherein the preparation steps of UiO-66-NH2 are as follows: ZrCl4 (3 mmol, 0.699 g) and 2-aminoterephthalic acid (3 mmol, 0.543 g) were dissolved in N,N-dimethylformamide (20 mL). The two solutions were mixed in a polytetrafluoroethylene reactor, and deionized water (2 mL) was added. After stirring for 10 minutes, the mixture was placed in an oven at 120°C for 24 hours. The resulting crystals were separated by centrifugation, washed three times with methanol to remove unreacted ligands, and dried under vacuum at 60°C overnight to obtain UiO-66-NH2 reddish-brown powder.

[0028] Example 3 The only difference between this embodiment and Embodiment 1 is that MIL-125-NH2 is used as the MOF core of the nanocomposite filler, wherein the preparation steps of MIL-125-NH2 are as follows: 2-Aminoterephthalic acid (3 mmol, 0.543 g) was dissolved in a mixed solvent of N,N-dimethylformamide and deionized water (8 mL + 8 μL). Benzoic acid (12 mmol, 1.465 g) and methanol (2 mL) were then added, and the mixture was stirred for 30 minutes until completely dissolved. The solution was transferred to a reaction vessel, and tetraisopropyl titanate (1.5 mmol, 0.426 g) was added. After stirring for another 10 minutes, the mixture was placed in an oven at 110 °C and reacted for 12 hours. The resulting crystals were separated by centrifugation, washed three times with methanol to remove unreacted ligands, and dried under vacuum at 60 °C overnight to obtain a reddish-brown powder, MIL-125-NH2.

[0029] Example 4 The difference between this embodiment and Embodiment 1 lies only in that: an asymmetric thin-film nanocomposite film is prepared using an impregnation-coating method, followed by heat treatment to form a cross-linked mixed matrix film. The specific steps are as follows: One end of the dried alumina tube was sealed with a rubber stopper to prevent the coating solution from entering the inner cavity. The alumina support was then vertically immersed in a film-forming solution with a 4 wt.% composite filler concentration for 5 seconds before being pulled out. After drying in air at room temperature for 6 hours, the coated support was vacuum-dried overnight at 120°C to obtain a cPIM-1@ZIF-8-NH2 / PIM-1 thin-film nanocomposite membrane. The membrane sample was placed in a ceramic boat and then placed in a tube furnace. Before heat treatment, the tube furnace was evacuated three times and filled with nitrogen to reduce the oxygen concentration to below 100 ppm. The furnace was then heated in 100 mL for 1 min. -1 Heat treatment of the thin-film nanocomposite film was performed under nitrogen flow rate. The heating procedure is as follows: Figure 1 After cooling to room temperature, a cross-linked mixed matrix membrane is obtained.

[0030] Comparative Example 1 The process is basically the same as in Example 1, except that the obtained self-supporting cPIM-1@ZIF-8-NH2 / PIM-1 mixed matrix membrane is not subjected to heat treatment, but its separation performance is directly tested.

[0031] Comparative Example 2 The process is basically the same as in Example 1, except that ZIF-8-NH2 nanoparticles are used as fillers to prepare the cross-linked mixed matrix membrane.

[0032] PIM-1 (0.3 g) was dissolved in chloroform (10 g), and after complete dissolution, it was filtered through a PTFE filter (1 μm) to remove solid impurities. An appropriate amount of ZIF-8-NH2 / CHCl3 dispersion was added according to the filling volume to form a film-forming solution, which was then thoroughly mixed on a tubular mixer. The solution was then evacuated to remove air bubbles. The final film-forming solution was poured into a flat-bottomed petri dish using a casting method, and the dish was placed in a glove bag filled with chloroform vapor. After the solvent had completely evaporated, the petri dish was removed, and the film was obtained by peeling with deionized water. After vacuum drying at 120°C for 24 hours, a self-supporting ZIF-8-NH2 / PIM-1 mixed matrix membrane was obtained. The membrane sample was sandwiched between two quartz plates in a ceramic boat, and then placed in a tube furnace. Before heat treatment, the tube furnace was evacuated three times and purged with nitrogen to reduce the oxygen concentration to below 100 ppm, followed by 100 mL / min. -1 The mixed matrix membrane was heat-treated at a nitrogen flow rate; the heating procedure is as follows: Figure 1 After cooling to room temperature, a cross-linked hybrid matrix membrane based on a single ZIF-8-NH2 filler is obtained.

[0033] Characterization Figure 1 The diagram shows the heat treatment process of the cross-linked mixed matrix membranes prepared in Examples 1-4. As can be seen, the process uses a segmented heating method and reduces the heating rate at high temperatures to ensure that the cross-linked mixed matrix membranes can be fully and uniformly cross-linked by heat. Figure 2 The image shows a transmission electron microscope (TEM) image of the cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1. As can be seen from the image, the ZIF-8-NH2 core has a core size of 30 nm and the cPIM-1 shell thickness is 10 nm. Figure 3 The Fourier transform infrared (FTIR) spectrum of the cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1 shows that the ZIF-8-NH2 core and the cPIM-1 shell are tightly bonded by hydrogen bonds. Figure 4The image shows a cross-sectional scanning electron microscope (SEM) image of the cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1. As can be seen from the image, a strong interface is formed between the nanocomposite filler and the PIM-1 matrix, with no defects and no agglomeration. Figure 5 The image shows the cross-linked molecular structure of the cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 1. During the heat treatment process, dual-interface covalent bonding was achieved: the pre-assembled hydrogen bonds between the ZIF-8-NH2 core and the cPIM-1 shell were transformed into strong amide bonds, while the cyano groups remaining in the cPIM-1 shell underwent a cyclization trimerization reaction with the PIM-1 matrix. Figure 6 The image shows a cross-sectional scanning electron microscope (SEM) image of the asymmetric cross-linked hybrid matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler prepared in Example 4. As can be seen from the image, the obtained membrane has a 3 μm thick selective layer tightly adhered to the outer surface of the rigid support, and no delamination was observed. Furthermore, no particle agglomeration or interface defects were observed in the membrane layer.

[0034] Figure 7 The image shows a cross-sectional scanning electron microscope (SEM) image of the cross-linked mixed matrix membrane based on ZIF-8-NH2 nanofiller prepared in Comparative Example 2. As can be seen from the image, the single ZIF-8-NH2 filler without the cPIM-1 shell exhibits severe agglomeration, and obvious cracks and pinhole defects appear between the filler and the matrix. This indicates that the cPIM-1 shell plays an important role in uniform dispersion, defect-free interface, and multi-level covalent cross-linked network.

[0035] Experiment: CO2 / N2 separation performance test The prepared cross-linked mixed matrix membrane was placed in a self-made membrane module, maintaining a pressure difference of 2 bar between the feed side and the permeate side, a test temperature of 35℃, and a gas flow rate of 50 mL / min. -1 The CO2 and N2 feed ratio is 1:1, and the downstream is purged with helium to test the separation performance of the CO2 and N2 mixture.

[0036] like Figure 8 As shown, with the increase of the loading of cPIM-1@ZIF-8-NH2 nanocomposite filler, the CO2 permeability and CO2 / N2 selectivity of the cross-linked mixed matrix membrane both increase, with the highest CO2 / N2 selectivity at a loading of 4wt%.

[0037] like Figure 9 As shown, under different heat treatment temperatures and times, the CO2 permeability of the cross-linked mixed matrix membrane decreases with increasing reaction temperature and time, and the CO2 / N2 selectivity decreases with increasing reaction temperature. The overall performance reaches its best at a reaction temperature of 360°C and a reaction time of 2 hours.

[0038] like Figure 10 As shown, the cross-linked mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler in Example 1 has better performance than the mixed matrix membrane based on cPIM-1@ZIF-8-NH2 nanocomposite filler in Comparative Example 1, and the cross-linked mixed matrix membrane based on a single ZIF-8-NH2 filler in Comparative Example 2.

[0039] like Figure 11 As shown, the three cross-linked mixed matrix membranes based on different nanocomposite fillers in Examples 1-3 all exhibited excellent CO2 / N2 separation performance, which was superior to other PIMs-based mixed matrix membranes and post-treated PIMs polymer membranes reported in other literature, and far exceeded the Robeson upper limit in 2019.

[0040] like Figure 12 As shown, the CO2 / CH4 ratio of the asymmetric cross-linked mixed matrix membrane prepared using the thin film nanocomposite membrane as the original membrane in Example 4 is also superior to that of most thin film composite (TFC) membranes and thin film nanocomposite (TFN) membranes.

[0041] Depend on Figure 11 and Figure 12 It is evident that the interfacial crosslinking strategy based on nanocomposite fillers proposed in this invention exhibits excellent universality and scalability potential. Figure 11 Breakthrough performance was achieved in three different MOF-based composite membranes, proving that this technology is applicable to metal-organic framework materials with different topologies and pore size characteristics, such as ZIF-8-NH2, UiO-66-NH2, and MIL-125-NH2. The membrane separation characteristics can be directionally controlled through precise selection of MOF fillers. Meanwhile, Figure 12 The successful preparation of the thin-film nanocomposite membrane demonstrates that the crosslinking process is compatible with the mature dip-coating-heat treatment process in industry. While maintaining excellent separation performance, it shows good potential for large-scale preparation, marking a key step towards practical application.

Claims

1. A cross-linked hybrid matrix membrane based on nanocomposite fillers, characterized in that, It includes a PIM-1 polymer matrix and a nanocomposite filler blended in the polymer matrix. The nanocomposite filler has a core-shell structure and is formed by the self-assembly of an amino-functionalized metal-organic framework material MOF-NH2 and a carboxyl-functionalized PIM-1 polymer cPIM-1 through hydrogen bonding. The polymer matrix and the nanocomposite filler are connected by covalent bonds.

2. The crosslinked hybrid matrix membrane according to claim 1, characterized in that, The MOF-NH2 is selected from one or more of ZIF-8-NH2, UiO-66-NH2 or MIL-125-NH2.

3. The cross-linked hybrid matrix membrane according to claim 1, characterized in that, The shell thickness of the nanocomposite filler is 2-20 nm, and the particle size of the MOF-NH2 core is 10-1000 nm.

4. The crosslinked hybrid matrix membrane according to claim 1, characterized in that, The mass fraction of the nanocomposite filler in the PIM-1 polymer matrix is ​​0.5-40 wt%.

5. A method for preparing a cross-linked hybrid matrix membrane based on nanocomposite fillers according to claim 1, comprising the following steps: (1) MOF-NH2 was prepared by using a synthesis solution containing amino organic ligands, and PIM-1 polymer was partially carboxylated by acid hydrolysis to obtain carboxylated polymer cPIM-1; (2) The MOF-NH2 and cPIM-1 are mixed in an organic solvent and self-assembled by hydrogen bonding to form a cPIM-1@MOF-NH2 composite filler with a core-shell structure; (3) The cPIM-1@MOF-NH2 composite filler is dispersed in a PIM-1 polymer solution to form a casting solution, and a mixed matrix membrane is prepared. (4) The mixed matrix membrane is heat-treated in an inert atmosphere to cause a multi-level covalent cross-linking reaction between the polymer matrix and the composite filler to form a cross-linked mixed matrix membrane.

6. The method according to claim 5, characterized in that, In step (1), the amino organic ligand is selected from 2-aminobenzimidazole and 2-aminoterephthalic acid; the molar ratio of the original organic ligand to the amino organic ligand in the synthesis solution is 0-10:1; the proportion of amino ligand in the MOF-NH2 in the precursor solution is 10-100 wt%; the conversion rate of cyano groups to carboxyl groups in the carboxylated polymer cPIM-1 segment is 30%-100%, more preferably 40%-60%.

7. The method according to claim 5, characterized in that, In step (2), MOF-NH2 and cPIM-1 are mixed in a mass ratio of 1-10:1, and the organic solvent is selected from tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

8. The method according to claim 5, characterized in that, In step (3), the mass content of cPIM-1@MOF-NH2 composite filler in the casting solution is 0.5-40 wt%. The preparation method of the mixed matrix membrane is either casting or phase inversion.

9. The method according to claim 5, characterized in that, In step (4), the inert atmosphere is nitrogen, argon, or helium, wherein the oxygen concentration is controlled to be below 200 ppm; the heating procedure for the heat treatment is as follows: from room temperature at 5°C / min -1 The heating rate was increased to 200℃, held at 200℃ for 60-120 minutes, and then at 2.5℃ for 1 minute. -1 The temperature was lowered to 335°C, and finally reduced to 0.2°C for 1 minute. -1 The reaction temperature is then raised to 300-400℃ and maintained at the highest temperature for 30-720 minutes.

10. An application of the crosslinked hybrid matrix membrane according to claim 1, characterized in that, The applications include CO2 capture, natural gas purification, and industrial separation of carbon-containing gases.

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