Mixed matrix membrane based on preformed covalent organic framework network as well as preparation method and application of mixed matrix membrane

Abstract

The invention belongs to the technical field of gas separation membranes, and relates to a mixed matrix membrane based on a preformed covalent organic framework network, and a preparation method and application thereof. The mixed matrix membrane comprises a COF network, a polyimide polymer and a self-supported flexible substrate, and the mixed matrix membrane is MATT-COFTD-x; the polymer is polyimide Matrimid5218, and the 3D interconnection COF network is a COFTD (Chip On Fiber Transfer Device) network; the COF network is prepared by reacting an aldehyde monomer and an amino monomer on the surface of the SiO2 / Si substrate through a liquid-solid interfacial polymerization method. According to the prepared mixed matrix membrane, filler agglomeration is eliminated, a continuous 3D interconnected COF network is provided, ultra-fast gas transmission is allowed, high permeability and high selectivity are achieved, and meanwhile stable high performance is still kept under the conditions of high pressure, different H2 / CH4 mixing ratios and the like.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane technology, and relates to a hybrid matrix membrane based on a preformed covalent organic framework network, its preparation method, and its application. Background Technology

[0002] Hydrogen energy is a key strategic direction for the global energy system's transition to sustainable development in the 21st century. As a high-energy-density, zero-carbon-emission secondary energy source, it plays an irreplaceable role in achieving carbon neutrality and ensuring national energy security. However, the key issue currently limiting the large-scale application of hydrogen energy lies in the safe and efficient storage and transportation of H2. Utilizing existing natural gas pipelines for H2 / CH4 mixed transportation is considered an important route for achieving large-scale H2 transportation. However, after reaching the end-user, H2 needs to be efficiently separated from the mixture to meet the purity requirements of the end-use application. Therefore, developing efficient hydrogen separation technologies is of significant practical importance.

[0003] Membrane separation technology, as an energy-saving and environmentally friendly separation method, has gradually attracted widespread attention. Currently, polymer membranes are the mainstream membrane materials used in industry for H2 / CH4 separation, but their separation performance is limited by the trade-off between permeability and selectivity. Hybrid matrix membranes, by introducing dispersed fillers into a polymer matrix, combine the good processability of polymers with the excellent gas separation characteristics of fillers, showing promising prospects for industrial applications. Current research has used metal-organic frameworks, zeolites, and graphene oxide as fillers to prepare hybrid matrix membranes for H2 / CH4 separation. However, commonly used inorganic fillers have poor compatibility with polymer matrices, easily forming non-selective voids and interfacial defects within the membrane, thus affecting separation performance. Therefore, how to construct a uniformly distributed and highly interconnected filler phase in a hybrid matrix membrane to fully utilize the separation performance of the filler remains a key problem to be solved in current technology.

[0004] Compared to pressure swing absorption (PSA) technology, membrane technology for terminal separation in hydrogen transportation via natural gas pipelines offers advantages such as lower energy consumption, easier operation, and less environmental pollution. However, current membrane technologies, particularly polymer membranes based on dissolution-diffusion mechanisms, suffer from a trade-off effect where permeability and selectivity are difficult to balance, making them unsuitable for meeting separation requirements. Furthermore, most polymer membranes experience significant performance degradation under high pressure due to plasticization. While polymer membranes based on transport-enhancing mechanisms exhibit excellent performance at low pressures, their performance declines sharply with increasing pressure. Inorganic separation membranes such as zeolite membranes and carbon molecular sieve membranes, despite their excellent molecular sieving properties and high-pressure operational stability, are prone to blockage of mass transfer channels due to impurity adsorption and condensation when separating complex materials in natural gas-to-hydrogen pipelines, leading to significant performance degradation. Additionally, the inherent structural rigidity and fabrication stress of these materials hinder large-scale, defect-free fabrication. While blending fillers with polymers to create mixed-matrix membranes can balance processability and separation performance, the poor compatibility between commonly used inorganic fillers and polymers leads to filler agglomeration and sedimentation, limiting the improvement of mixed-matrix membrane separation performance. Summary of the Invention

[0005] This invention addresses the problems existing in the terminal separation of hydrogen transportation via traditional natural gas pipelines by proposing a hybrid matrix membrane based on a preformed covalent organic framework network, its preparation method, and its application.

[0006] This invention provides a hybrid matrix membrane based on a pre-formed COF network, which is used for terminal separation in hydrogen transportation via natural gas pipelines. The "pre-formed packing network" used in this invention solves the bottleneck problem of packing agglomeration in hybrid matrix membranes, and its continuous 3D interconnected COF network provides an ultra-fast gas transport channel. The membrane prepared by this invention can be used in H2 / CH4 separation processes, exhibiting high separation performance and stability.

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution: A hybrid matrix membrane based on a preformed COF network, the hybrid matrix membrane comprising a COF network, a polyimide polymer, and a self-supporting flexible substrate, wherein the hybrid matrix membrane is MAT-COF. TD -x; the polymer is polyimide Matrimid® 5218, and the 3D interconnected COF network is COF. TD The COF network is prepared by reacting aldehyde monomers and amino monomers on the surface of a SiO2 / Si substrate via liquid-solid interface polymerization.

[0008] Preferably, the aldehyde monomer is 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (DHBDA); the amino monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TTA); and the catalyst used in the liquid-solid interface polymerization reaction is scandium trifluoromethanesulfonate (Sc(OTf)3).

[0009] This invention proposes a method for preparing the above-mentioned hybrid matrix membrane based on a pre-formed COF network, the steps of which are as follows: (1) After cleaning the SiO2 / Si substrate, oxygen plasma treatment was performed, and then it was stored in an argon atmosphere to obtain substrate M.

[0010] (2) Add 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde to ethyl acetate and mix evenly to obtain mixture A; add scandium trifluoromethanesulfonate to deionized water and disperse evenly to obtain dispersion B; slowly add mixture A to dispersion B, then vertically immerse substrate M and allow it to stand for reaction to prepare 3D interconnected COF network on SiO2 / Si substrate.

[0011] (3) The polyimide dispersion is dropped onto the 3D interconnected COF network, and the Mayer rod is pushed to scrape across the COF surface to allow the polymer to penetrate into the COF network. The mixture is left to stand to evaporate the residual solvent and obtain the substrate N.

[0012] (4) The substrate N was placed in a hydrofluoric acid solution and allowed to stand so that the SiO2 layer was etched by HF, causing the mixed matrix film to detach. The detached film was then rinsed three times with deionized water. The rinsed film was then removed and dried to prepare MAT-COF. TD -x membrane.

[0013] Preferably, in step (1), the SiO2 / Si substrate is cleaned sequentially with deionized water, acetone and ethanol, and then treated for 25-35 seconds under conditions of oxygen flow rate of 50-70 sccm and plasma power of 90-110 W.

[0014] Preferably, in step (2), the concentration of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine in mixture A is 0.0005-0.005 mol / L, and the concentration of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde is 0.001-0.003 mol / L; the concentration of scandium trifluoromethanesulfonate in dispersion B is 0.0005-0.001 mol / L; the substrate M is vertically immersed and allowed to stand for 3-5 days; and the standing reaction temperature is 25-35℃.

[0015] Preferably, in step (3), the mass fraction of the polyimide dispersion is 1-5%, the solvent is chloroform, the polyimide is Matrimid® 5218, and the standing time after leveling is 5-10h.

[0016] Preferably, in step (4), the mass fraction of the hydrofluoric acid solution is 0.5-1%; the drying temperature is 70-85℃; and the drying time is at least 12h.

[0017] This invention proposes the application of the hybrid matrix membrane based on the preformed COF network prepared by the above method in H2 / CH4 gas separation.

[0018] The self-supporting COF scaffold in the hybrid matrix membrane based on the pre-formed COF network avoids the problems of filler aggregation and sedimentation during solvent evaporation. The 3D interconnected structure of the COF network is achieved through monomer selection and control of synthesis concentration, temperature, and other conditions, providing continuous mass transfer channels within the polymer and allowing for ultra-fast gas transport, followed by polymer casting. The polymer thickness is controlled using the Mayer rod coating method, thereby regulating the membrane's separation performance. Due to the excellent compatibility between the polymer and the COF network filler, and the establishment of continuous transport channels within the hybrid matrix membrane, H2 permeability is significantly enhanced while maintaining high H2 / CH4 separation selectivity. The efficient H2 / CH4 separation process is achieved based on the differences in dissolution and diffusion of gas molecules within the continuous transport channels; based on COF... TD The fully organic network structure exhibits strong compatibility with polymers, effectively eliminating interfacial defects. Therefore, the membrane possesses excellent high-pressure separation stability and anti-plasticity; it also maintains excellent performance under different feed gas compositions. Based on COF... TD The membrane of the network has excellent flexibility, exhibiting superior toughness and anti-aging properties.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are as follows: The hybrid matrix membrane based on a pre-formed COF network prepared in this invention eliminates filler agglomeration and provides a continuous 3D interconnected COF network, allowing for ultra-fast gas transport. It exhibits high permeability and high selectivity, while maintaining stable high performance under high pressure and different H2 / CH4 mixing ratios, achieving efficient H2 / CH4 separation. The hybrid matrix membrane based on a pre-formed COF network described in this invention combines high separation performance with strong stability. Attached Figure Description

[0020] Figure 1 It is COF TD Surface electron microscope image.

[0021] Figure 2 It is COF TDCross-sectional electron microscope image.

[0022] Figure 3 It is COF TP Surface electron microscope image.

[0023] Figure 4 It is COF TB Surface electron microscope image. Detailed Implementation

[0024] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0025] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0026] Example 1 This embodiment provides MAT-COF TD - The specific preparation process of the mixed matrix membrane: The SiO2 / Si substrate (Beijing TopV Technology Co., Ltd., catalog number TopV, 4-inch, oxide layer thickness 300nm) was cut into 5cm×2cm pieces. The SiO2 / Si substrate was first washed twice with deionized water, acetone and ethanol respectively, with a volume of about 5mL each time. It was then placed in ethanol and sonicated for 30min. After that, the SiO2 / Si substrate was dried with nitrogen and stored in a clean petri dish. The treated SiO2 / Si substrate was placed in a ceramic boat and then treated with oxygen plasma for 30s under the conditions of oxygen flow rate of 60 sccm and plasma power of 100W. After treatment, it was stored under Ar atmosphere. COF was prepared on a SiO2 / Si substrate by liquid-solid interfacial polymerization using TTA (Jilin Zhongke Science & Technology Co., Ltd., CAS: 14544-47-9, catalog number YSZC175) and DHBDA (Jilin Zhongke Science & Technology Co., Ltd., CAS: 1951-36-6, catalog number YSZC090) as monomers under the action of catalyst Sc(OTf)3 (Shanghai Aladdin Biochemical Technology Co., Ltd., CAS: 144026-79-9, catalog number S106648) as catalyst. TDThe specific procedure involves adding 0.135 mmol of TTA and 0.202 mmol of DHBDA to 90 mL of ethyl acetate, followed by sonication at room temperature for 10 min to prepare a mixture of TTA and DHBDA in ethyl acetate. Then, the Sc(OTf)3 catalyst is added to 30 mL of deionized water and gently shaken to ensure complete mixing, resulting in an aqueous dispersion with a concentration of 0.0008 mmol / mL.

[0027] Then, a mixture of ethyl acetate from the two monomers was slowly added dropwise to the surface of the Sc(OTf)3 aqueous dispersion, keeping the ethyl acetate phase on top. The treated SiO2 / Si substrate was vertically immersed into this biphase system and allowed to stand at 30 °C for 4 days. After standing, the surface of the SiO2 / Si substrate was exposed to the organic phase, forming an orange COF network. After the reaction, the SiO2 / Si substrate with COF growth was washed three times with ethyl acetate and ethanol, respectively, and then vacuum dried at 60 °C for 12 h to obtain the COF network on the SiO2 / Si substrate.

[0028] Matrimid® 5218 (BASF, USA, molecular weight 40,000, CAS No.: 104983-64-4) was dissolved in chloroform and stirred at 700 rpm at 25°C until a transparent brownish-yellow solution was obtained, preparing a 4 wt.% Matrimid® 5218 dispersion. Then, an appropriate amount (approximately 8 mL) was dropped onto a SiO2 / Si substrate with a COF network, ensuring the 4 wt.% Matrimid® 5218 dispersion completely covered the COF network. TD The network, at a constant speed, pushes the Mayer rod (Japanese OSP coating rod, L60-OSP-1.5) across the COF. TD Surface, allowing polymers to penetrate COF TD Immediately cover the contents with a petri dish to slow down solvent evaporation and let stand at room temperature for 8 hours.

[0029] The coated SiO2 / Si substrate was placed in a plastic petri dish containing 0.5 wt.% HF solution. HF etched the SiO2 layer, causing the mixed matrix film to detach. After etching for 30 minutes, the detached film was rinsed three times with approximately 100 mL of deionized water each time. The rinsed film was then removed and dried at 80 °C for 12 hours to obtain MAT-COF. TD -Ⅳ Hybrid matrix membrane.

[0030] For MAT-COF TD -Ⅳ The mixed matrix membrane was imaged by electron microscopy, and the results are as follows: Figure 1 and Figure 2 As shown in the figure, COF can be seen TDIt exhibits a distinct network structure on the SiO2 / Si substrate, without any agglomeration.

[0031] Four membranes were prepared using the method described in this embodiment, denoted as membranes P1-P4, and their performance was verified as follows.

[0032] 1. MAT-COF TD -Ⅳ Mixed matrix membrane (P1) was used in the H2 / CH4 separation system at 25°C and feed gas pressure of 1 bar. The CO2 permeability was 366.7 Barrer and the H2 / CH4 separation selectivity was 100.2.

[0033] 2. Using MAT-COF TD -Ⅳ Mixed matrix membrane (P2): When the feed pressure was increased from 1 bar to 10 bar, the H2 / CH4 separation factor (121.2-105.7) decreased by only 12.7%, and no plasticization was observed at 10 bar. This indicates that the membrane has excellent high-pressure separation stability and anti-plasticization properties, combined with COF TD The interfacial interaction between the network and the polymer effectively limits the swelling of the polymer chains under high pressure.

[0034] 3. Use MAT-COF TD -Ⅳ Mixed matrix membrane (P3), at 25°C, when the volume percentage of feed gas H2 / CH4 was increased from 10 / 90 to 90 / 10, the H2 permeability (305-278 Barrer) and H2 / CH4 separation factor (113.5-92.8) decreased by 8.8% and 18.0%, respectively, indicating that MAT-COF TD -IV hybrid matrix membranes maintain excellent performance under different feed gas compositions.

[0035] 4. Use MAT-COF TD -Ⅳ Mixed matrix membrane (P4), under 25℃ and feed gas pressure of 1 bar, underwent a 100-h stability test. The H2 permeability decreased by only 1.8%, while the H2 / CH4 separation factor (145.1-253) increased slightly, indicating that the MAT-COF... TD -Ⅳ hybrid matrix membranes exhibit excellent long-term stability. Based on COF TD The membrane of the network has excellent flexibility, MAT-COF TD -IV hybrid matrix membranes can be bent on PAN substrates, indicating that COF TD Networks help to significantly enhance the flexibility of hybrid matrix membranes.

[0036] Example 2 This embodiment provides MAT-COF TD-The specific preparation process of the mixed matrix membrane is the same as in Example 1, unless otherwise specified in this embodiment and the following embodiments. The SiO2 / Si substrate was cut into 5cm × 2cm pieces. It was first washed twice with deionized water, acetone, and ethanol sequentially, and then sonicated in ethanol for 30 min. Afterward, the SiO2 / Si substrate was dried with nitrogen and stored in a clean petri dish. The treated SiO2 / Si substrate was placed in a ceramic boat and treated with oxygen plasma at an oxygen flow rate of 50 sccm and a plasma power of 100 W for 30 s. After treatment, it was stored under an Ar atmosphere. 0.27 mmol TTA and 0.202 mmol DHBDA were dissolved in 90 mL of ethyl acetate and sonicated at room temperature for 10 min to prepare a mixture of TTA and DHBDA in ethyl acetate. Then, Sc(OTf)3 was added to 30 mL of deionized water and gently shaken to completely disperse it, preparing a dispersion with a concentration of 0.0008 mmol / mL.

[0037] The ethyl acetate mixture was then slowly added dropwise to the surface of the Sc(OTf)3 aqueous dispersion, keeping the ethyl acetate phase on top. The treated SiO2 / Si substrate was vertically immersed in the biphase system and allowed to stand at 30 °C for 4 days. After standing, the surface of the SiO2 / Si substrate was exposed to the organic phase, forming an orange COF network. After the reaction, the SiO2 / Si substrate with COF growth was washed three times with ethyl acetate and ethanol, respectively, and then vacuum dried at 60 °C for 12 h to obtain a COF network on the SiO2 / Si substrate.

[0038] Matrimid® 5218 was dissolved in chloroform and stirred at 700 rpm at 25°C until a transparent brownish-yellow solution was obtained, preparing a 4 wt.% Matrimid® 5218 solution. Then, 8 mL of this solution was dropped onto a SiO2 / Si substrate with a COF network, ensuring the 4 wt.% Matrimid® 5218 solution completely covered the COF network. TD The network, with a constant speed, propels the Mayer rod across the COF. TD Surface, allowing polymers to penetrate COF TD Immediately cover the container with a petri dish to slow down solvent evaporation and let it stand for 8 hours.

[0039] The coated SiO2 / Si substrate was placed in a plastic petri dish containing 0.5 wt.% HF solution. HF etched the SiO2 layer, causing the mixed matrix film to detach. After etching for 30 minutes, the detached film was rinsed three times with deionized water. The rinsed film was then removed and dried at 80 °C for 12 hours to obtain MAT-COF. TD -Ⅳ Hybrid matrix membrane.

[0040] The hybrid membrane prepared in this embodiment was used in an H2 / CH4 separation system at 25°C and a feed gas pressure of 1 bar. The CO2 permeability was 347.3 Barrer and the H2 / CH4 separation selectivity was 95.1.

[0041] Example 3 This embodiment provides MAT-COF TD -IV. Specific preparation process of the mixed matrix membrane. SiO2 / Si substrates were cut into 5 cm × 2 cm pieces. The SiO2 / Si substrates were first washed twice sequentially with deionized water, acetone, and ethanol, and then sonicated in ethanol for 30 min. Afterward, the SiO2 / Si substrates were dried with nitrogen for 10 min and stored in a clean petri dish. The treated SiO2 / Si substrates were placed in a ceramic boat and treated with oxygen plasma at an oxygen flow rate of 70 sccm and a plasma power of 100 W for 30 s. After treatment, they were stored under an Ar atmosphere. 0.405 mmol TTA and 0.202 mmol DHBDA were dissolved in 90 mL of ethyl acetate and then sonicated at room temperature for 10 min to prepare an ethyl acetate mixture of TTA and DHBDA. Then, Sc(OTf)3 was added to 30 mL of deionized water and gently shaken to completely disperse it, obtaining an aqueous dispersion of Sc(OTf)3 with a concentration of 0.0008 mmol / mL.

[0042] The ethyl acetate mixture was then slowly added dropwise to the surface of the Sc(OTf)3 aqueous dispersion, keeping the ethyl acetate phase on top. The treated SiO2 / Si substrate was vertically immersed in the biphase system and allowed to stand at 30 °C for 4 days. After standing, the surface of the SiO2 / Si substrate was exposed to the organic phase, forming an orange COF network. After the reaction, the SiO2 / Si substrate with COF growth was washed three times alternately with ethyl acetate and ethanol, and then vacuum dried at 60 °C for 12 h to obtain the COF network on the SiO2 / Si substrate.

[0043] Matrimid® 5218 was added to chloroform and stirred at 700 rpm for 10 min at 25°C to obtain a transparent brownish-yellow dispersion, thus preparing a 4 wt.% Matrimid® 5218 dispersion. Then, 10 mL was dropped onto a SiO2 / Si substrate with a COF network, ensuring the 4 wt.% Matrimid® 5218 dispersion completely covered the COF. TD The network, with a constant speed, propels the Mayer rod across the COF. TD Surface, allowing polymers to penetrate COF TD Immediately cover the container with a petri dish to slow down solvent evaporation and let it stand for 8 hours.

[0044] The coated SiO2 / Si substrate was placed in a plastic petri dish containing 0.5 wt.% HF solution. HF etched the SiO2 layer, causing the mixed matrix film to detach. After etching for 30 minutes, the detached film was rinsed three times with deionized water. The rinsed film was then removed and dried at 80 °C for 12 hours to obtain MAT-COF. TD -Ⅳ Hybrid matrix membrane.

[0045] The mixed matrix membrane prepared in this embodiment was used in an H2 / CH4 separation system. Under the conditions of 25°C and feed gas pressure of 1 bar, the CO2 permeability was 346.3 Barrer and the H2 / CH4 separation selectivity was 98.1.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that the DHBDA monomer was replaced with an equimolar amount of terephthalaldehyde (Shanghai Aladdin Biochemical Technology Co., Ltd., CAS: 623-27-8, catalog number P105980). The remaining preparation process and amounts of substances remained unchanged from Example 1. Testing revealed that the membrane prepared in this comparative example formed a cluster-like structure and could not form a COF network structure. Figure 3 As shown.

[0047] Comparative Example 2 The difference between this comparative example and Example 1 is that 0.27 mmol TTA and 0.202 mmol DHBDA were dissolved in 26 mL of a 1,4-dioxane / trimethylbenzene (volume ratio 1:1) mixed solution. The rest of the preparation process remained unchanged from Example 1. Testing revealed that the membrane prepared in this comparative example formed a tightly packed granular structure and could not form a COF network structure. Figure 4 As shown.

[0048] Comparative Example 3 The difference between this comparative example and Example 1 is that the concentration of the Matrimid® 5218 dispersion is 2 wt.%, while the rest of the preparation process remains unchanged from Example 1. When the membrane prepared in this comparative example was used in an H2 / CH4 separation system, at 25°C and a feed gas pressure of 1 bar, the H2 permeation flux was 897.3 Barrer, and the selectivity was 7.9.

[0049] Comparative Example 4 The difference between this comparative example and Example 1 is that the concentration of Matrimid® 5218 dispersion is 5 wt.%, while the rest of the preparation process remains unchanged from Example 1. The membrane prepared in this comparative example was used in an H2 / CH4 separation system. Under the conditions of 25°C and feed gas pressure of 1 bar, the H2 permeation flux was 175.9 Barrer and the selectivity was 126.0.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A hybrid matrix membrane based on a pre-formed COF network, characterized in that, The hybrid matrix membrane comprises a COF network, a polyimide polymer, and a self-supporting flexible substrate; the COF network is prepared by reacting aldehyde monomers and amino monomers on the surface of a SiO2 / Si substrate via liquid-solid interface polymerization.

2. The hybrid matrix membrane based on a pre-formed COF network according to claim 1, characterized in that, The aldehyde monomer is 2,5-dihydroxy-1,4-benzenedicarboxaldehyde; the amino monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; and the catalyst used in the liquid-solid interface polymerization reaction is scandium trifluoromethanesulfonate.

3. The method for preparing a hybrid matrix membrane based on a pre-formed COF network as described in claim 1 or 2, characterized in that, The steps are as follows: (1) After cleaning the SiO2 / Si substrate, oxygen plasma treatment was performed, and then it was stored in an argon atmosphere to obtain substrate M; (2) 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde were added to ethyl acetate and mixed evenly to obtain mixture A; scandium trifluoromethanesulfonate was added to deionized water and dispersed evenly to obtain dispersion B; mixture A was slowly added dropwise to dispersion B, and then substrate M was vertically immersed and allowed to stand for reaction to prepare 3D interconnected COF network on SiO2 / Si substrate; (3) The polyimide dispersion was dropped onto the 3D interconnected COF network, leveled, and allowed to stand to obtain the substrate N; (4) Place the substrate N in a hydrofluoric acid solution and let it stand to react, so that the mixed matrix membrane is detached. Then rinse the detached membrane with deionized water and dry it.

4. The method for preparing a hybrid matrix membrane based on a pre-formed COF network according to claim 3, characterized in that, In step (1), the SiO2 / Si substrate is cleaned sequentially with deionized water, acetone and ethanol, and then treated for 25-35 seconds under conditions of oxygen flow rate of 50-70 sccm and plasma power of 90-110 W.

5. The method for preparing a hybrid matrix membrane based on a pre-formed COF network according to claim 3, characterized in that, In step (2), the concentration of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine in mixture A is 0.0005-0.005 mol / L, and the concentration of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde is 0.001-0.003 mol / L; the concentration of scandium trifluoromethanesulfonate in dispersion B is 0.0005-0.001 mol / L; after vertical immersion of substrate M, the static reaction time is 3-5 days, and the static reaction temperature is 25-35℃.

6. The method for preparing a hybrid matrix membrane based on a pre-formed COF network according to claim 3, characterized in that, In step (3), the mass fraction of the polyimide dispersion is 1-5%, the solvent is chloroform, the polyimide is Matrimid® 5218, and the standing time after leveling is 5-10h.

7. The method for preparing a hybrid matrix membrane based on a pre-formed COF network according to claim 3, characterized in that, In step (4), the hydrofluoric acid solution has a mass fraction of 0.5-1%, the drying temperature is 70-85℃, and the drying time is at least 12 hours.

8. The application of the hybrid matrix membrane based on the preformed COF network prepared by any one of claims 4-7 in gas separation.

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