Preparation and application of hourglass type covalent organic framework composite membrane

Abstract

The invention provides a preparation method of an hourglass type covalent organic framework (COF) composite membrane, and belongs to the field of gas membrane separation. According to the method, covalent organic framework nanosheets with different pore diameters and charge characteristics are utilized to construct the COF composite membrane with a unique hourglass structure through a vacuum-assisted layer-by-layer assembly technology, so that precise regulation and control on H2 and CO2 gas transmission behaviors are realized, and the prepared composite membrane shows remarkable H2 / CO2 separation selectivity and high permeation flux, and has a good application prospect. The chemical stability, the thermal stability and the mechanical flexibility are excellent. The invention provides a novel solution for efficient gas separation and energy storage application.

Description

Technical Field

[0001] The invention relates to the preparation and application of an "hourglass-shaped" covalent organic framework composite membrane, and belongs to the technical field of gas separation membranes. Background Art

[0002] With the continuous advancement of industrialization, the demand for the separation of hydrogen (H2) and carbon dioxide (CO2) gases has increased dramatically. As a clean energy with great potential, hydrogen has shown broad application prospects in many fields such as fuel cell technology and chemical synthesis; and the capture and storage of carbon dioxide has become one of the key strategies to mitigate the greenhouse effect and promote the realization of carbon neutrality goals. In this context, membrane separation technology stands out with its excellent performance. It not only significantly improves the separation efficiency and reduces energy consumption, but also has the advantages of simple operation and superior cost-effectiveness. Compared with traditional separation methods, such as chemical absorption and cryogenic distillation, membrane separation technology is more in line with the core needs of modern industry for high efficiency, environmental protection and sustainable development, and provides a greener and more economical solution for hydrogen purification and carbon dioxide emission reduction.

[0003] Covalent organic framework (COF) membrane materials have shown great application potential in the field of gas separation due to their highly ordered crystal structure, ultra-high specific surface area, and excellent chemical and thermal stability. COF membranes can achieve highly selective separation of specific molecules by regulating the pore structure, and are widely used in organic solvent nanofiltration, dye desalination, and seawater desalination. However, due to the large pore size of COF membranes, their gas separation selectivity is low, resulting in the inability to effectively screen gas molecules of different sizes, limiting their application in efficient gas separation. Traditional methods mostly modify the COF pores to reduce the pore size, but there are difficulties such as high difficulty in synthesis and great challenges in membrane preparation. How to simply optimize the pore size and structural design to improve separation performance is a key challenge facing COF membranes in the field of gas separation. Summary of the invention

[0004] In view of the limitations of current technologies, the present invention proposes an "hourglass-shaped" covalent organic framework composite membrane for realizing H2 / CO2. The preparation method of the present invention is not only simple and easy to operate but also highly controllable. The prepared membrane exhibits excellent separation efficiency and operational stability in the H2 / CO2 separation task.

[0005] The present invention is achieved through the following technical scheme: preparation and application of an "hourglass-shaped" covalent organic framework composite membrane. The membrane material is composed of covalent organic framework nanosheets with different pore sizes and different charge characteristics, and a vacuum-assisted self-assembly method is used to achieve layer-by-layer stacking assembly. The entire preparation process is simple and easy to control.

[0006] The "hourglass-shaped" covalent organic framework composite membrane described in the present invention specifically includes a variety of sulfonic acid COF nanosheets, such as TpPa-SO3H, TpBd-SO3H, NABAPa-SO3H, TFPBPa-SO3H and CABPTZPa-SO3H, all of which are prepared by a single-phase method; at the same time, the membrane also includes amino COF nanosheets, including TpTGCl, ACOF and TpTG, which are prepared by an interfacial polymerization method. Among them, TpBd-SO3H and TpTGCl nanosheets are preferred.

[0007] Step 1) Preparation of sulfonic acid TpBd-SO3H COF nanosheet dispersion: dissolving a certain proportion of 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde in a dimethyl sulfoxide solution and ultrasonically dispersing it, which is recorded as an aldehyde monomer solution; dissolving a certain proportion of 4,4-diamino-3,3'-biphenyldisulfonic acid in dimethyl sulfoxide and ultrasonically dispersing it, which is recorded as an amine monomer solution; finally, adding the aldehyde monomer solution to the amine monomer solution and mixing them evenly, reacting at 80° C. for 15 days to obtain an orange-yellow solution, and dialyzing with a 30,000 Da dialysis bag for 2 days to obtain a uniformly dispersed orange-yellow colloidal solution, i.e., a sulfonic acid TpBd-SO3HCOF nanosheet dispersion. Preparation of amino TpTGClCOF nanosheet dispersion: 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde was dissolved in a 3M acetic acid aqueous solution in a certain proportion and ultrasonically dispersed, which was recorded as the bottom solution; triaminoguanidine salt was dissolved in a mixed solution of mesitylene and dioxane in a certain proportion and ultrasonically dispersed, which was recorded as the top solution; finally, the top solution was slowly added to the surface of the bottom solution, and the reaction was allowed to stand at 40°C for 3 days to obtain a light yellow solution, which was dialyzed with a 30000Da dialysis bag for 2 days to obtain a uniformly dispersed light yellow colloidal solution, i.e., amino TpTGCl COF nanosheet dispersion.

[0008] Step 2) Dilution of an "hourglass-shaped" covalent organic framework composite membrane nanosheet: dilute the dispersion prepared in step 1) with deionized water to obtain a concentration of 0.2 mg mL -1 Dispersions of covalent organic frameworks with different pore sizes and different charges.

[0009] Step 3) Preparation of an "hourglass-shaped" covalent organic framework composite membrane: The dispersion obtained in step 2) is filtered layer by layer onto the surface of the polyacrylonitrile porous membrane by a vacuum-assisted self-assembly method, and then dried at 30°C for 24 hours to obtain an "hourglass-shaped" covalent organic framework composite membrane.

[0010] The prepared hourglass-shaped covalent organic framework composite membrane was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 4105.8-1421.5 GPU (1 GPU = 1×10 -6 cm3 (STP)cm -2 s - 2 cmHg -1 ), H2 / CO2 selectivity is 6-21.

[0011] Compared with the prior art, the advantages of the present invention are:

[0012] By using covalent organic framework (COF) nanosheets with different pore sizes and different charges, gas separation membranes can be prepared by vacuum filtration layer by layer, which can achieve high permeability and high selectivity at the same time. Large pores provide fast gas permeation channels, small pores enhance the molecular sieving effect, and form a dense and uniform membrane structure through orderly stacking, significantly reducing gas leakage. In addition, the synergistic effect of multifunctional nanosheets optimizes the gas diffusion path and interaction. Combined with the high porosity and mechanical stability of COF, this method has the advantages of structural controllability, environmental friendliness, and low energy consumption, providing an innovative solution for efficient gas separation technology.

[0013] The membrane preparation process of the present invention is simple and controllable, the membrane structure is stable, and it has good applicability, and can be extended to covalent organic framework (COF) materials with other topological structures. When the composite membrane prepared by the present invention is applied to the H2 / CO2 separation system, it exhibits excellent high permeability and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a scanning electron microscope image of covalent organic framework nanosheets with different pore sizes and different charges prepared in Example 1 of the present invention;

[0015] Figure 2 is a surface electron microscope image of the membrane 1 prepared in Example 1 of the present invention;

[0016] Figure 3 is a cross-sectional electron microscope image of the membrane 1 prepared in Example 1 of the present invention;

[0017] Figure 4 is a surface electron microscope image of the membrane 2 prepared in Example 2 of the present invention;

[0018] Figure 5 is a cross-sectional electron microscope image of the membrane 2 prepared in Example 2 of the present invention;

[0019] Figure 6 is a surface electron microscope image of the membrane 3 prepared in Example 3 of the present invention;

[0020] Figure 7 is a cross-sectional electron microscope image of the membrane 3 prepared in Example 3 of the present invention;

[0021] Figure 8 is a surface electron microscope image of the membrane 4 prepared in Example 4 of the present invention;

[0022] Fig. 9 is a cross-sectional electron microscope image of the membrane 4 prepared in Example 4 of the present invention;

[0023] Fig.10 is a surface electron microscope image of the membrane 5 prepared in Example 5 of the present invention;

[0024] Fig.11 is a cross-sectional electron microscope image of the membrane 5 prepared in Example 5 of the present invention;

[0025] Fig.12 is a surface electron microscope image of the membrane 6 prepared in Comparative Example 1 of the present invention;

[0026] Fig.13 is a cross-sectional electron micrograph of the membrane 6 prepared in Comparative Example 1 of the present invention;

[0027] Fig.14 is a surface electron microscope image of the membrane 7 prepared in Comparative Example 2 of the present invention;

[0028] Fig.15 is a cross-sectional electron micrograph of the membrane 7 prepared in Comparative Example 2 of the present invention;

[0029] Fig.16 It is a comparison of H2 permeation rate and H2 / CO2 selectivity of membranes 1-5 of the present invention and comparative membranes 6 and 7;

[0030] Fig.17 It is a schematic diagram of the "hourglass-shaped" covalent organic framework composite membrane of the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing an "hourglass-shaped" covalent organic framework composite membrane for H2 / CO2 separation. The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0032] The "hourglass-shaped" covalent organic framework composite membrane of the present invention comprises sulfonic acid COF nanosheets, such as TpPa-SO3H, TpBd-SO3H, NABAPa-SO3H, TFPBPa-SO3H and CABPTZPa-SO3H, which are prepared by a single-phase method; and the membrane also comprises amino COF nanosheets, including TpTGCl, ACOF and TpTG, which are prepared by an interfacial polymerization method. Among them, TpBd-SO3H and TpTGCl nanosheets are preferred.

[0033] Example 1: Preparation of an "hourglass-shaped" covalent organic framework composite membrane, the steps are as follows:

[0034] Step 1) Preparation of sulfonic acid TpBd-SO3H COF nanosheet dispersion: 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde (10.3 mg) was dissolved in dimethyl sulfoxide solution and ultrasonically dispersed, which was recorded as aldehyde monomer solution; 4,4-diamino-3,3'-biphenyldisulfonic acid (4.6 mg) was dissolved in dimethyl sulfoxide and ultrasonically dispersed, which was recorded as amine monomer solution; finally, the aldehyde monomer solution was added to the amine monomer solution and mixed evenly, and reacted at 80° C. for 15 days to obtain an orange-yellow solution, which was dialyzed with a 30000Da dialysis bag for 2 days to obtain a uniformly dispersed orange-yellow colloidal solution, i.e., sulfonic acid TpBd-SO3HCOF nanosheet dispersion. Preparation of amino TpTGClCOF nanosheet dispersion: 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde (28 mg) was dissolved in a 3M acetic acid aqueous solution and ultrasonically dispersed, which was recorded as the bottom solution; aminoguanidine salt (21 mg) was dissolved in a mixed solution of mesitylene and dioxane and ultrasonically dispersed, which was recorded as the top solution; finally, the top solution was slowly added to the surface of the bottom solution, and the reaction was allowed to stand at 40°C for 3 days to obtain a light yellow solution, which was dialyzed with a 30000Da dialysis bag for 2 days to obtain a uniformly dispersed light yellow colloidal solution, i.e., amino TpTGCl COF nanosheet dispersion.

[0035] Step 2) Preparation of an "hourglass-shaped" covalent organic framework composite membrane: dilute 1 mL of the covalent organic framework dispersion obtained in step 1 to 10 mL, and prepare a dispersion of covalent organic framework nanosheets with different pore sizes and different charges at a certain concentration; wherein the scanning electron microscope image of the COF nanosheet is as follows Figure 1 shown.

[0036] Step 3) A method for preparing an "hourglass-shaped" covalent organic framework composite membrane: The dispersion obtained in step 2 is deposited on the surface of porous polyacrylonitrile by vacuum-assisted layer-by-layer self-assembly to construct a covalent organic framework composite membrane with an "hourglass-shaped" structure. The specific steps are as follows: first, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ), and then a layer of amino COF nanosheet dispersion (0.1 mg mL -1 ), and finally, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ). Subsequently, the film was dried at 30° C. for 24 hours to obtain a covalent organic framework film with a thickness of 70 nm, which was recorded as Film 1. Figure 2 The surface morphology of the display film 1, Figure 3 This is a scanning electron microscope image of the cross section of membrane 1.

[0037] The "hourglass-shaped" covalent organic framework composite membrane (membrane 1) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 4105.8GPU and the H2 / CO2 selectivity was 8.

[0038] Example 2: Preparation of an "hourglass-shaped" covalent organic framework composite membrane, the steps are as follows:

[0039] Step 1) preparing a dispersion of covalent organic framework nanosheets with different pore sizes and different charges; the preparation process is basically the same as that of Example 1.

[0040] Step 2) Preparation of an "hourglass-shaped" covalent organic framework composite membrane: dilute 1 mL of the covalent organic framework dispersion obtained in step 1 to 10 mL, and prepare dispersions of covalent organic framework nanosheets with different pore sizes and different pore sizes at a certain concentration.

[0041] Step 3) A method for preparing an "hourglass-shaped" covalent organic framework composite membrane: The preparation process is basically the same as that in Example 1, except that: first, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ), and then a layer of amino COF nanosheet dispersion (0.2 mg mL -1 ), and finally, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ). Subsequently, the film was dried at 30° C. for 24 hours to obtain a covalent organic framework film with a thickness of 105 nm, which was recorded as Film 1. Figure 4 The surface morphology of the display film 2, Figure 5 This is a cross-sectional scanning electron microscope image of membrane 2.

[0042] The "hourglass-shaped" covalent organic framework composite membrane (membrane 2) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 3245.6GPU and the H2 / CO2 selectivity was 11.

[0043] Example 3: Preparation of an "hourglass-shaped" covalent organic framework composite membrane, the steps are as follows:

[0044] Step 1) preparing a dispersion of covalent organic framework nanosheets with different pore sizes and different charges; the preparation process is basically the same as that of Example 1.

[0045] Step 2) Preparation of an "hourglass-shaped" covalent organic framework composite membrane: dilute 1 mL of the covalent organic framework dispersion obtained in step 1 to 10 mL, and prepare dispersions of covalent organic framework nanosheets with different pore sizes and different pore sizes at a certain concentration.

[0046] Step 3) A method for preparing an "hourglass-shaped" covalent organic framework composite membrane: The preparation process is basically the same as that in Example 1, except that: first, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ), and then a layer of amino COF nanosheet dispersion (0.3 mg mL -1 ), and finally, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ). Subsequently, the film was dried at 30° C. for 24 hours to obtain a covalent organic framework film with a thickness of 200 nm, which was recorded as Film 1. Figure 6 The surface morphology of the display film 3, Figure 7 This is a cross-sectional scanning electron microscope image of membrane 3.

[0047] The "hourglass-shaped" covalent organic framework composite membrane (membrane 3) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 2933.7 GPU and the H2 / CO2 selectivity was 19.

[0048] Example 4: Preparation of an "hourglass-shaped" covalent organic framework composite membrane, the steps are as follows:

[0049] Step 1) preparing a dispersion of covalent organic framework nanosheets with different pore sizes and different charges; the preparation process is basically the same as that of Example 1.

[0050] Step 2) Preparation of an "hourglass-shaped" covalent organic framework composite membrane: dilute 1 mL of the covalent organic framework dispersion obtained in step 1 to 10 mL, and prepare a covalent organic framework nanosheet dispersion with different pore sizes and different charges at a certain concentration.

[0051] Step 3) A method for preparing an "hourglass-shaped" covalent organic framework composite membrane: The preparation process is basically the same as that in Example 1, except that: first, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ), and then a layer of amino COF nanosheet dispersion (0.4 mg mL -1 ), and finally, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ). Subsequently, the film was dried at 30° C. for 24 hours to obtain a covalent organic framework film with a thickness of 500 nm, which was recorded as Film 1. Figure 8 The surface morphology of the display film 4, Fig. 9 This is a cross-sectional scanning electron microscope image of membrane 4.

[0052] The "hourglass-shaped" covalent organic framework composite membrane (membrane 4) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 2105.9 GPU and the H2 / CO2 selectivity was 20.

[0053] Example 5: Preparation of an "hourglass-shaped" covalent organic framework composite membrane, the steps are as follows:

[0054] Step 1) preparing a dispersion of covalent organic framework nanosheets with different pore sizes and different charges; the preparation process is basically the same as that of Example 1.

[0055] Step 2) Preparation of an "hourglass-shaped" covalent organic framework composite membrane: dilute 1 mL of the covalent organic framework dispersion obtained in step 1 to 10 mL, and prepare covalent organic framework nanosheet dispersions with different pore sizes at a certain concentration.

[0056] Step 3) A method for preparing an "hourglass-shaped" covalent organic framework composite membrane: The preparation process is basically the same as that in Example 1, except that: first, a layer of sulfonic acid COF nanosheet dispersion (0.1 mg mL -1 ), and then a layer of amino COF nanosheet dispersion (0.5 mg mL -1 ), and finally filter a layer of sulfonic acid COF dispersion (0.1 mg mL -1 ). Subsequently, the film was dried at 30° C. for 24 hours to obtain a covalent organic framework film with a thickness of 900 nm, which was recorded as Film 1. Fig.10 The surface morphology of the display film 5, Fig.11 This is a cross-sectional scanning electron microscope image of membrane 5.

[0057] The "hourglass-shaped" covalent organic framework composite membrane (membrane 5) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 1843.6 GPU and the H2 / CO2 selectivity was 21.

[0058] Comparative Example 1: Preparation of a sulfonic acid covalent organic framework, the steps include preparing a sulfonic acid COF nanosheet dispersion and preparing a COF film, as follows:

[0058] Step 1) preparing a covalent organic framework nanosheet dispersion: similar to step 1 of Example 1, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde (10.3 mg) was dissolved in a dimethyl sulfoxide solution and ultrasonically dispersed, which was recorded as an aldehyde monomer solution; 4,4-diamino-3,3'-biphenyldisulfonic acid (4.6 mg) was dissolved in dimethyl sulfoxide and ultrasonically dispersed, which was recorded as an amine monomer solution; finally, the aldehyde monomer solution was added to the amine monomer solution and mixed evenly, and the mixture was reacted at 80° C. for 15 days to obtain an orange-yellow solution, which was dialyzed with a 30,000 Da dialysis bag for 2 days to obtain a uniformly dispersed orange-yellow colloidal solution, i.e., a sulfonic acid TpBd-SO3H COF nanosheet dispersion.

[0059] Step 2) Preparation of a covalent organic framework dispersion: 1 mL of the covalent organic framework dispersion obtained in step 1 is diluted to 10 mL to prepare a covalent organic framework nanosheet dispersion having a certain concentration.

[0060] Step 3) Preparation of covalent organic framework membrane: The dispersion obtained in step 2 is deposited on the surface of porous polyacrylonitrile by vacuum assisted self-assembly to form a covalent organic framework membrane, and dried at 30°C for 24 hours to obtain a covalent organic framework membrane with a thickness of 100 nm, which is recorded as membrane 6. Fig.12 The surface morphology of the display film 6, Fig.13 This is a cross-sectional scanning electron microscope image of membrane 6.

[0061] The "hourglass-shaped" covalent organic framework composite membrane (membrane 6) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 3159.9 GPU and the H2 / CO2 selectivity was 6.

[0062] Comparative Example 2: Preparation of an amino covalent organic framework, the steps including preparation of an amino COF nanosheet dispersion and preparation of a COF film, as follows:

[0063] Step 1) Preparation of a covalent organic framework nanosheet dispersion: Similar to step 1 of Example 1, preparation of an amino TpTGCl COF nanosheet dispersion: 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde (28 mg) was dissolved in a 3M acetic acid aqueous solution and ultrasonically dispersed, which was recorded as a bottom solution; aminoguanidine salt (21 mg) was dissolved in a mixed solution of mesitylene and dioxane and ultrasonically dispersed, which was recorded as a top solution; finally, the top solution was slowly added to the surface of the bottom solution, and the reaction was allowed to stand at 40° C. for 3 days to obtain a light yellow solution, which was dialyzed for 2 days using a 30,000 Da dialysis bag to obtain a uniformly dispersed light yellow colloidal solution, i.e., an amino TpTGCl COF nanosheet dispersion.

[0064] Step 2) Preparation of a covalent organic framework dispersion: 1 mL of the covalent organic framework dispersion obtained in step 1 is diluted to 10 mL to prepare a covalent organic framework nanosheet dispersion having a certain concentration.

[0065] Step 3) Preparation of covalent organic framework membrane: The dispersion obtained in step 2 is deposited on the surface of porous polyacrylonitrile by vacuum assisted self-assembly to form a covalent organic framework membrane, and dried at 30°C for 24 hours to obtain a covalent organic framework membrane with a thickness of 94 nm, which is recorded as membrane 7. Fig.14 The surface morphology of the display film 7, Fig.14 This is a scanning electron microscope image of the cross section of membrane 7.

[0066] The amino covalent organic framework composite (membrane 7) prepared by the above invention was used for H2 / CO2 separation. Under the conditions of operating temperature of 25°C and pressure of 1 bar, the H2 permeation rate was 1421.5 GPU and the H2 / CO2 selectivity was 7.

[0067] By comparing the embodiments and comparative examples, it can be seen that the present invention provides a gas separation membrane of an "hourglass-shaped" covalent organic framework (COF) nanosheet and a preparation method thereof. Through layer-by-layer vacuum filtration technology, large-pore and small-pore COF nanosheets are stacked in order to form a dense membrane structure with high permeability and high selectivity. Large-pore nanosheets provide fast gas permeation channels, and small-pore nanosheets enhance the molecular sieving effect while reducing gas leakage channels. The synergistic effect of multifunctional nanosheets further optimizes gas diffusion paths and molecular interactions. The membrane has high porosity, excellent mechanical stability and structural controllability, can significantly reduce the energy consumption of the gas separation process, and meets environmentally friendly requirements. Its preparation method is simple and controllable, can be extended to COF materials with different topological structures, is suitable for a variety of gas separation systems, and especially exhibits excellent performance in H2 / CO2 separation, and has broad application prospects. Fig.16 It is a comparison chart of H2 permeation flux and H2 / CO2 selectivity performance of membranes 1-5 and the comparison membrane. Fig.17 It is a schematic diagram of the "hourglass-shaped" covalent organic framework composite membrane of the present invention.

[0068] Although the present invention is described in detail above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments. These embodiments are only illustrative descriptions, not restrictive definitions. Under the enlightenment of the present invention, those of ordinary skill in the art can still make various deformations or improvements without departing from the core idea of ​​the present invention, and these deformations and improvements all belong to the protection scope of the present invention.

Claims

1. Preparation and application of an "hourglass-shaped" covalent organic framework composite membrane, characterized in that: The steps include: (1) Preparation of covalent organic framework nanosheets with different pore sizes and different charges: (2) Preparation of "hourglass-shaped" covalent organic framework composite membranes by vacuum-assisted self-assembly; (3) The "hourglass-shaped" covalent organic framework composite membrane is used for H2 / CO2 separation.

2. The technology according to claim 1, wherein precise regulation of the transport of H2 and CO2 molecules is achieved by optimizing the content and arrangement of covalent organic framework nanosheets, thereby improving the selectivity and permeation flux of H2 / CO2 separation.

3. The technology according to claim 1 and 2, wherein the preparation of COF nanosheets adopts a single-phase method and an interfacial polymerization method respectively. It comprises the following steps: - Preparation of sulfonic acid covalent organic framework nanosheets: dissolve aldehyde monomer and amine monomer in dimethyl sulfoxide solution respectively, slowly add dropwise to mix, react at 80°C for 7 days to obtain sulfonic acid covalent organic framework nanosheets; - Preparation of amino covalent organic framework: dissolve amine monomer in 3M acetic acid aqueous solution, dissolve aldehyde monomer in a mixed solution of mesitylene and dioxane, slowly add dropwise to mix, and react at 40°C for 3 days to obtain amino covalent organic framework nanosheets. .

4. The preparation method according to claim 3, wherein the final concentration of the prepared covalent organic framework nanosheet colloidal solution is 0.02 mg mL -1 and diluted to an appropriate concentration with deionized water.

5. The method for preparing covalent organic framework membranes with different pore sizes and different charges according to claim 4, characterized in that: Nanosheet colloidal solutions with different pore sizes and different charges are deposited on the surface of a porous support membrane by vacuum-assisted self-assembly. The porous support membrane is one of a variety of commercial ultrafiltration membranes such as polyacrylonitrile, polyethersulfone, polypropylene and polytetrafluoroethylene, preferably polyacrylonitrile.

6. According to the method of claims 1-5, the use of the "hourglass-shaped" covalent organic framework composite membrane in H2 / CO2 separation is characterized in that: When the test conditions are 25°C and 1 bar, the H2 permeation flux of the membrane is 4105.8-1421.5 GPU (1 GPU = 1×10 -6 cm 3 (STP)cm -2 s -2 cmHg -1 ), H2 / CO2 selectivity is 6-21.

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