A high-temperature-resistant composite covalent organic framework humidifying membrane and a preparation method thereof

Abstract

The application discloses a high-temperature-resistant composite covalent organic framework humidification membrane and a preparation method thereof. The membrane comprises a membrane matrix composed of a covalent organic framework crystalline layer and a polysulfone material. The application couples a non-solvent phase separation process with a vapor assisted crystallization process, which is an important attempt to improve the high-temperature resistance of the humidification membrane by using a crystalline porous skin layer. The prepared composite covalent organic framework humidification membrane is formed by in-situ vapor composition on the surface of the membrane, which can be firmly anchored on the surface of the membrane matrix, thereby giving the membrane high temperature resistance and high application stability. The crystalline layer can be designed in terms of its pore size and hydrophilicity to realize precise screening of water vapor and air, thereby giving the composite covalent organic framework high water vapor / air selectivity. The finger-shaped pore structure of the membrane matrix has high porosity, which can strengthen the permeability of water vapor in the membrane.

Description

Technical Field

[0001] This invention belongs to the field of novel separation membrane material technology, and relates to the development of membrane materials for use in the field of proton exchange membrane water management in fuel cells. Specifically, it relates to a high-temperature resistant composite covalent organic framework humidifying membrane and its preparation method. Background Technology

[0002] The upstream hydrogen energy industry aligns with my country's energy transition needs, while the downstream new energy vehicle market is experiencing rapid growth. Both upstream and downstream sectors represent promising blue ocean markets. Most hydrogen fuel cells are proton exchange membrane fuel cells, and the hydration state of the proton exchange membrane plays a decisive role in the fuel cell's performance and lifespan. Therefore, the reactant gases entering the fuel cell stack must be humidified, making membrane humidifiers the mainstream solution currently used in hydrogen fuel cell vehicles.

[0003] Currently, most membrane humidifiers internationally use polysulfone membranes (such as polyethersulfone, polysulfone, and polyphenylsulfone) as the polymer matrix. By optimizing process routes and in-situ material strengthening, the hydrophilicity, temperature resistance, and mechanical properties of the humidifier membrane material are modified to achieve targeted design and wide-ranging application of humidifier products. However, the development of high-temperature resistant humidifier membrane materials remains a bottleneck. This is mainly because under high-temperature conditions, the increased movement of polymer chain segments within the humidifier membrane leads to membrane structure collapse and increased mass transfer resistance. High temperatures weaken intermolecular interactions within the humidifier membrane, reducing its mechanical properties and making it prone to breakage and internal leakage under airflow impact. High-temperature operating conditions also cause the decomposition or performance degradation of polymers, pore-forming agents, and reinforcing agents within the humidifier membrane, thereby inhibiting the membrane's humidification efficiency. Therefore, high-temperature resistant humidifier membranes face extremely challenging scientific and technological advancements, and the development of high-performance high-temperature resistant humidifier membranes has become a cutting-edge technology and a major demand in the field. Summary of the Invention

[0004] To address the above, this invention provides a high-temperature resistant composite covalent organic framework humidifying membrane and its preparation method. The method combines a covalent organic framework with a traditional polymer, coupling a non-solvent phase separation process with a steam-assisted crystallization process to design a composite humidifying membrane structure. A high-temperature resistant covalent organic framework crystal layer is constructed on the surface of a polymer matrix, thus solving the problems in existing technologies such as the mutual restriction between water vapor / air selectivity and water vapor permeability under high-temperature conditions, and poor application stability.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for preparing a composite covalent organic framework humidifying membrane includes the following steps:

[0007] (1) Disperse polysulfone materials, polyvinylpyrrolidone, and polyethylene glycol in an organic solvent to obtain a casting solution;

[0008] (2) Prepare an organic solvent / water mixture with a volume fraction of 40% to 90% as a coagulation bath;

[0009] (3) The casting solution from step (1) is scraped onto a glass plate, left to stand, then transferred to a coagulation bath for immersion, and then dried at 25-120°C for 1-72 hours to obtain the membrane matrix.

[0010] (4) Prepare organic solution A with a mass concentration of 0.1% to 0.5% of covalent organic framework aldehyde monomer, immerse the membrane matrix in organic solution A, keep it at 25 to 60°C for 10 to 30 seconds, and then let it stand at room temperature for 4 to 8 hours.

[0011] (5) Prepare an organic solution B containing 0.15% to 0.75% covalent organic framework amino monomers, transfer the organic solution B to a heating vessel, and fix the membrane matrix at the top of the heating vessel with the membrane matrix surface facing down; reset the nitrogen gas in the heating vessel, set the heating vessel temperature to 80 to 150°C, and obtain a high-temperature resistant composite covalent organic framework humidifying membrane.

[0012] Further, in step (1), the polysulfone material includes one or more combinations of polysulfone, polyethersulfone, polyphenylsulfone, sulfonated polysulfone, sulfonated polyethersulfone, and sulfonated polyphenylsulfone;

[0013] In step (1), the organic solvent is any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, and N-methylpyrrolidone.

[0014] In step (2), the organic solvent is any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, and N-methylpyrrolidone.

[0015] Further, in step (1), the mass concentration of polysulfone materials in the casting solution is 14% to 22%, the mass concentration of polyvinylpyrrolidone is 0.2% to 5%, and the mass concentration of polyethylene glycol is 0.2% to 5%.

[0016] Further, in step (4), the covalent organic framework aldehyde monomer is one of pyromellitic aldehyde and trialdehyde phloroglucinol; in step (5), the covalent organic framework amino monomer is one of diaminobenzenesulfonic acid and diaminobenzoic acid.

[0017] Furthermore, in step (4), the organic solvent used in the organic solution A is any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, and N-methylpyrrolidone;

[0018] In step (5), the organic solvent used in the organic solution B is any one of methanol, ethanol, toluene, or dichloromethane.

[0019] Furthermore, in step (3), the standing time is 5-15 seconds and the soaking time is 5-15 minutes.

[0020] Further, in step (5), the rotation speed of the worktable at the top of the membrane is set to 1-20 r / s, and the evaporation time is set to 1-48 h.

[0021] A high-temperature resistant composite covalent organic framework humidifying membrane is prepared by any one of the preparation methods described in this invention.

[0022] Furthermore, the high-temperature resistant composite covalent organic framework humidifying membrane comprises the following components: a covalent organic framework crystalline layer and a matrix composed of a polysulfone material; wherein, the covalent organic framework crystalline layer is uniformly distributed on the outer surface of the matrix, forming a high-temperature resistant crystalline skin with a thickness of 100-200 nm and a roughness of 60-80 nm; the polysulfone matrix has a finger-like pore structure in cross-section, forming a composite covalent organic framework humidifying membrane with a thickness of 100-300 μm.

[0023] Furthermore, in the aforementioned composite covalent organic framework humidifying membrane, the material of the covalent organic framework crystalline layer is any one of the following: pyromellitic aldehyde-p-phenylenediamine, pyromellitic aldehyde-2,5-diaminobenzenesulfonic acid, pyromellitic aldehyde-2,5-diaminobenzoic acid, pyromellitic aldehyde-2,5-diaminophosphonic acid, trialdehyde-phloroglucinol-p-phenylenediamine, trialdehyde-phloroglucinol-2,5-diaminobenzenesulfonic acid, trialdehyde-phloroglucinol-2,5-diaminobenzoic acid, and trialdehyde-phloroglucinol-2,5-diaminophosphonic acid.

[0024] Furthermore, the present invention relates to the application of the high-temperature resistant composite covalent organic framework humidifying membrane in the water management process of fuel cell proton exchange membranes.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] The high-temperature resistant composite covalent organic framework humidifying membrane prepared in this invention comprises the following components: a covalent organic framework crystalline layer and a membrane matrix composed of a polysulfone material; wherein the covalent organic framework crystalline layer is uniformly distributed on the outer surface of the membrane matrix, forming a crystalline skin layer with a thickness of 100–200 nm and a roughness of 5–20 nm; the polysulfone matrix has a finger-like pore structure in cross-section, thus forming the composite covalent organic framework humidifying membrane. This invention couples a solvent-free phase separation process with a steam-assisted crystallization process, representing an important attempt to improve the high-temperature resistance of humidifying membranes using a crystalline porous skin layer. The prepared composite covalent organic framework humidification membrane exhibits high temperature resistance and application stability because the covalent organic framework is formed in situ on the membrane surface by vapor composition. The crystalline layer, with its pore size and hydrophilic design, enables precise sieving of water vapor and air, giving the composite covalent organic framework high water vapor / air selectivity. The finger-like pore structure of the membrane matrix, with its well-developed porosity, enhances the permeability of water vapor within the membrane. Therefore, the high-temperature resistant composite covalent organic framework humidification membrane disclosed in this invention is stable and efficient in the water management process of proton exchange membranes in fuel cells. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart illustrating the preparation method of the high-temperature resistant composite covalent organic framework humidifying membrane of the present invention.

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the high-temperature resistant composite covalent organic framework humidifying membrane of Embodiment 1 of the present invention, wherein... Figure 2 a is a cross-sectional morphology diagram of the membrane. Figure 2 b is a topographic image of the outer surface of the membrane. Figure 2 c represents the surface roughness diagram of the membrane.

[0029] Figure 3 This is a scanning electron microscope (SEM) image of the high-temperature resistant composite covalent organic framework humidifying membrane of Embodiment 2 of the present invention, wherein... Figure 3 a is a cross-sectional morphology diagram of the membrane. Figure 3 b is a topographic image of the outer surface of the membrane. Figure 3 c represents the surface roughness diagram of the membrane.

[0030] Figure 4 This is a scanning electron microscope image of the composite covalent organic framework membrane of Comparative Example 1 of the present invention, wherein... Figure 4 a is a cross-sectional morphology diagram of the membrane. Figure 4 b is a topographic image of the outer surface of the membrane. Figure 4 c represents the surface roughness diagram of the membrane.

[0031] Figure 5 This is a scanning electron microscope image of the composite covalent organic framework membrane of Comparative Example 2 of the present invention, wherein... Figure 5 a is a cross-sectional morphology diagram of the membrane. Figure 5 b is a topographic image of the outer surface of the membrane. Figure 5 c represents the surface roughness diagram of the membrane. Detailed Implementation

[0032] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0033] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0034] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0035] Table 1 Chinese meanings

[0036]

[0037]

[0038] The structural formula of the trialdehyde-resorcinol used in this embodiment is as follows:

[0039]

[0040] Membrane humidifiers are a key component of hydrogen-powered heavy-duty trucks, used to maintain the high-temperature and high-humidity operating conditions of the battery stack. However, the humidification membrane, which is the "chip" of this device, faces challenges such as low humidification efficiency, poor application stability, and insufficient impact resistance, thus limiting the development of this field to some extent.

[0041] To address the aforementioned issues, the applicant provides a high-temperature resistant composite covalent organic framework humidifying membrane and its preparation method, which couples a non-solvent phase separation process with a steam-assisted crystallization process. This represents an important attempt to enhance the high-temperature resistance of humidifying membranes using a crystalline porous skin layer. The prepared composite covalent organic framework humidifying membrane, because the covalent organic framework is formed in situ on the membrane surface by vapor composition, can be stably anchored to the membrane matrix surface, giving the membrane high temperature resistance and high application stability. The crystalline layer, through its pore size and hydrophilic design, can achieve precise sieving of water vapor and air, giving the composite covalent organic framework high water vapor / air selectivity. The finger-like pore structure of the membrane matrix has a well-developed porosity, enhancing the permeability of water vapor within the membrane.

[0042] The high-temperature resistant composite covalent organic framework humidifying membrane of the present invention comprises the following components: a covalent organic framework crystalline layer and a membrane matrix composed of polysulfone materials.

[0043] Specifically, the covalent organic framework crystalline layer of the present invention is uniformly distributed on the outer surface of the membrane, forming a high-temperature resistant crystalline skin with a thickness of 100-200 nm and a roughness of 60-80 nm; the polysulfone matrix of the present invention has a double-layer finger-like pore structure in cross section, forming a high-temperature resistant composite covalent organic framework humidifying membrane with a thickness of 100-300 μm and a tensile strength of 8-10 MPa.

[0044] In one embodiment, the material of the covalent organic framework crystalline layer of the present invention is any one of the following: triphenylmethane-p-phenylenediamine (TFB-PPA), pyromellitic trimethylmethane-2,5-diaminobenzenesulfonic acid (TFB-PPA-SO3H), pyromellitic trimethylmethane-2,5-diaminobenzoic acid (TFB-PPA-CO2H), pyromellitic trimethylmethane-2,5-diaminobenzenephosphonic acid (TFB-PPA-PO4H2), trialdehyde-resorcinol-p-phenylenediamine (TP-PPA), trialdehyde-resorcinol-2,5-diaminobenzenesulfonic acid (TP-PPA-SO3H), trialdehyde-resorcinol-2,5-diaminobenzoic acid (TP-PPA-CO2H), and trialdehyde-resorcinol-2,5-diaminobenzenephosphonic acid (TP-PPA-PO4H2).

[0045] In one embodiment, the polysulfone material of the present invention includes one or more combinations of polysulfone, polyethersulfone, polyphenylsulfone, sulfonated polysulfone, sulfonated polyethersulfone, and sulfonated polyphenylsulfone.

[0046] The applicant also provided a method for preparing the aforementioned high-temperature resistant composite covalent organic framework humidifying membrane, such as... Figure 1 As shown, Figure 1 This is a schematic flowchart of one embodiment of the preparation method of a high-temperature resistant composite covalent organic framework humidifying membrane according to the present invention.

[0047] S100. Polysulfone materials, polyvinylpyrrolidone, and polyethylene glycol are dispersed in one or more organic solvents of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, and N-methylpyrrolidone to obtain a casting solution with a polysulfone material mass concentration of 14% to 22%, a polyvinylpyrrolidone mass concentration of 0.2% to 5%, and a polyethylene glycol mass concentration of 0.2% to 5%.

[0048] The role of organic solvents is to fully dissolve polysulfone materials.

[0049] S200: Prepare an organic solvent / water mixture with a volume fraction of 40% to 90% as a coagulation bath, wherein the organic solvent is any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, or N-methylpyrrolidone.

[0050] S300, then a flat sheet membrane was prepared by a non-solvent phase separation method, and dried at 25-120℃ for 1-72h to obtain the membrane matrix on the outer surface.

[0051] S400, prepare organic solution A with a mass concentration of 0.1% to 0.5% of covalent organic framework aldehyde monomer, using any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, or N-methylpyrrolidone; immerse the membrane matrix in organic solution A and maintain it at 25 to 60°C for 10 to 30 seconds, then remove it and let it stand at room temperature for 4 to 8 hours.

[0052] S500: Prepare an organic solution B containing 0.15%–0.75% (w / w) of a covalent organic framework amino monomer. The solvent used can be any one of methanol, ethanol, toluene, or dichloromethane. Transfer organic solution B to a heating vessel, and fix the membrane matrix at the top of the vessel with the membrane matrix surface facing down. Refill the heating vessel with nitrogen gas, set the heating vessel temperature to 80–150°C, set the rotation speed of the worktable at the top of the membrane to 1–20 r / s, and set the evaporation time to 1–48 h. Through the diffusion, contact, and reaction of organic vapor B on the surface of the membrane matrix, a high-temperature resistant composite covalent organic framework humidifying membrane can be obtained on the worktable.

[0053] Example 1

[0054] A high-temperature resistant composite covalent organic framework humidifying membrane is prepared using the following steps:

[0055] (1) Weigh 45g of polyethersulfone, 1.5g of polyvinylpyrrolidone, 1.5g of polyethylene glycol and 252g of N-methylpyrrolidone, add them to the mixing tank in sequence, and mechanically stir at 50°C for 12h at a stirring speed of 100rpm. After standing for 12h to remove bubbles, the casting solution is obtained.

[0056] (2) Prepare a mixture of N-methylpyrrolidone / water with a volume fraction of 40% and transfer it to a coagulation bath furnace at 20°C as a coagulation bath.

[0057] (3) The casting solution is scraped onto a glass plate, left to stand for 10 seconds, then transferred to a coagulation bath and soaked for 10 minutes. After being removed, it is dried at 50°C for 24 hours to obtain the membrane matrix.

[0058] (4) Prepare a 0.1% mass concentration dimethylformamide solution A of pyromellitic aldehyde, immerse the membrane matrix in organic solution A, keep it at 25°C for 10s, take it out and let it stand at room temperature for 8h.

[0059] (5) Prepare an ethanol solution B of 0.15% (w / w) of 2,5-diaminobenzenesulfonic acid. Transfer solution B to a heating vessel and fix the membrane matrix at the top of the vessel with the membrane matrix surface facing down. Refill the heating vessel with nitrogen, set the heating vessel temperature to 80°C, set the rotation speed of the worktable at the top of the membrane to 10 r / s, and set the evaporation time to 1 h. As the organic vapor B diffuses, contacts, and reacts on the surface of the membrane matrix, a high-temperature resistant composite covalent organic framework humidifying membrane is obtained on the worktable.

[0060] Example 2

[0061] A high-temperature resistant composite covalent organic framework humidifying membrane is prepared using the following steps:

[0062] (1) Weigh 50g of polyphenylsulfone, 5g of polyvinylpyrrolidone, 10g of polyethylene glycol and 235g of dimethylformamide, add them to the mixing tank in sequence, and mechanically stir at 50℃ for 12h at a stirring speed of 100rpm. After standing for 12h to remove bubbles, the casting solution is obtained.

[0063] (2) Prepare a mixture of N-methylpyrrolidone / water with a volume fraction of 40% and transfer it to a coagulation bath furnace at 20°C as a coagulation bath.

[0064] (3) The casting solution is scraped onto a glass plate, left to stand for 10 seconds, then transferred to a coagulation bath and soaked for 10 minutes. After being removed, it is dried at 50°C for 24 hours to obtain the membrane matrix.

[0065] (4) Prepare a 0.1% dimethylformamide solution A of trialdehyde resorcinol, immerse the membrane matrix in the organic solution A, keep it at 25°C for 15s, and then let it stand at room temperature for 24h.

[0066] (5) Prepare a methanol solution B containing 0.15% diaminobenzoic acid by mass. Transfer solution B to a heating vessel and fix the membrane substrate at the top of the vessel with the substrate surface facing down. Refill the heating vessel with nitrogen, set the temperature to 90°C, the rotation speed of the worktable at the top of the membrane to 10 r / s, and the evaporation time to 1.5 h. As the organic vapor B diffuses, contacts, and reacts on the surface of the membrane substrate, a high-temperature resistant composite covalent organic framework humidifying membrane can be obtained on the worktable.

[0067] Comparative Example 1

[0068] A composite covalent organic framework membrane is prepared using the following steps:

[0069] The steps of preparing the raw materials for the membrane matrix, forming in the coagulation bath, soaking the membrane matrix in solution A, and steam-assisted assembly in solution B are the same as in Example 1. The only change is the treatment conditions after the membrane matrix is ​​removed from the coagulation bath. That is, the membrane matrix is ​​soaked in the coagulation bath for 10 minutes, then removed and air-dried at 20°C for 0.5 hours. Subsequently, it is steam-assisted assembled to obtain a composite covalent organic framework membrane.

[0070] Comparative Example 2

[0071] A composite covalent organic framework membrane is prepared using the following steps:

[0072] The preparation of raw materials for the membrane matrix, the coagulation bath molding and drying process, the soaking of the membrane matrix in solution A, and the preparation of solution B are the same as in Example 1. Only the temperature of the steam-assisted assembly process is changed, that is, the temperature of the heating kettle is set to 200°C, the rotation speed of the top worktable of the membrane is set to 10 r / s, and the evaporation time is set to 1 h. Subsequently, a composite covalent organic framework membrane is obtained.

[0073] Comparative Example 3

[0074] A polysulfone membrane is prepared using the following steps:

[0075] 45g of polyethersulfone, 1.5g of polyvinylpyrrolidone, 1.5g of polyethylene glycol, and 252g of N-methylpyrrolidone were weighed and added sequentially to a mixing tank. The mixture was mechanically stirred at 50℃ for 12 hours at 100 rpm. After standing for 12 hours to remove bubbles, a casting solution was obtained. A 40% (v / v) N-methylpyrrolidone / water mixture was prepared and transferred to a 20℃ coagulation bath. The casting solution was coated onto a glass plate, allowed to stand for 10 seconds, and then immersed in the coagulation bath for 10 minutes. After removal, it was dried at 50℃ for 24 hours to obtain a polysulfone membrane. This comparative example only prepared the membrane matrix.

[0076] Comparative Example 4

[0077] A composite covalent organic framework membrane is prepared using the following steps:

[0078] (1) Weigh 50g of polyphenylsulfone, 5g of polyvinylpyrrolidone, 10g of polyethylene glycol and 235g of dimethylformamide, add them to the mixing tank in sequence, and mechanically stir at 50℃ for 12h at a stirring speed of 100rpm. After standing for 12h to remove bubbles, the casting solution is obtained.

[0079] (2) Prepare a mixture of N-methylpyrrolidone / water with a volume fraction of 40% and transfer it to a coagulation bath furnace at 20°C as a coagulation bath.

[0080] (3) The casting solution is scraped onto a glass plate, left to stand for 10 seconds, then transferred to a coagulation bath and soaked for 10 minutes. After being removed, it is dried at 50°C for 24 hours to obtain the membrane matrix.

[0081] (4) Prepare a 1% (w / w) dimethylformamide solution A of trialdehyde phloroglucinol, immerse the membrane matrix in the organic solution A, keep it at 25°C for 15s, and then let it stand at room temperature for 24h.

[0082] (5) Prepare a 1.5% (w / w) methanol solution B of diaminobenzoic acid. Transfer solution B to a heating vessel and fix the membrane substrate at the top of the vessel with the substrate surface facing down. Refill the heating vessel with nitrogen, set the heating vessel temperature to 90°C, set the rotation speed of the worktable at the top of the membrane to 10 r / s, and set the evaporation time to 1.5 h. As the organic vapor B diffuses, contacts, and reacts on the surface of the membrane substrate, a high-temperature resistant composite covalent organic framework humidifying membrane can be obtained on the worktable.

[0083] The main difference from Example 2 is the concentration of solutions A and B in steps (4)-(5).

[0084] Example of effect 1:

[0085] The high-temperature resistant composite covalent organic framework humidifying membrane prepared in Example 1 was characterized and analyzed by scanning electron microscopy and atomic force microscopy, and the results were obtained. Figure 2 . Figure 2 These are scanning electron microscope (SEM) and atomic force microscope (AFM) images of the high-temperature resistant composite covalent organic framework humidifying membrane of Embodiment 1 of the present invention. Figure 2 As shown, the high-temperature resistant composite covalent organic framework humidifying membrane prepared in Example 1 has a double-layer structure with a skin thickness of 165 nm, a smooth membrane surface with a roughness of 8.2 nm, and a matrix with a finger-like pore structure.

[0086] Example 2:

[0087] The high-temperature resistant composite covalent organic framework humidifying membrane prepared in Example 2 was characterized and analyzed by scanning electron microscopy and atomic force microscopy, and the results were obtained. Figure 3 . Figure 3 These are scanning electron microscope (SEM) and atomic force microscope (AFM) images of the high-temperature resistant composite covalent organic framework humidifying membrane of Embodiment 2 of the present invention. Figure 3 As shown, the high-temperature resistant composite covalent organic framework humidifying membrane prepared in Example 2 has a double-layer structure with a skin thickness of 180 nm, a smooth membrane surface with a roughness of 10.8 nm, and a matrix with a finger-like pore structure.

[0088] Example of effect 3:

[0089] The high-temperature resistant composite covalent organic framework humidifying membrane prepared in Comparative Example 1 was characterized and analyzed by scanning electron microscopy and atomic force microscopy, and the results were obtained. Figure 4 . Figure 4 These are scanning electron microscope (SEM) and atomic force microscope (AFM) images of the composite covalent organic framework membrane prepared in Comparative Example 1 of this invention. Figure 4 As shown, the composite covalent organic framework membrane prepared in Comparative Example 1 has a bilayer structure with a skin layer thickness of approximately 50 nm, protruding particles on the membrane surface, a roughness of 27.4 nm, and a matrix with a finger-like pore structure.

[0090] Example of effect 4:

[0091] The high-temperature resistant composite covalent organic framework humidifying membrane prepared in Comparative Example 2 was characterized and analyzed by scanning electron microscopy and atomic force microscopy, and the results were obtained. Figure 5 . Figure 5 These are scanning electron microscope (SEM) and atomic force microscope (AFM) images of the composite covalent organic framework membrane prepared in Comparative Example 2 of this invention. Figure 5 As shown, the composite covalent organic framework membrane prepared in Comparative Example 2 has a bilayer structure with a skin layer thickness of approximately 100 nm. The membrane surface exhibits a discontinuous cluster particle morphology with a roughness of 50.3 nm, and the matrix has a finger-like pore structure.

[0092] The results of Examples 1-4 show that the membrane matrix treatment process before steam-assisted assembly and the evaporation process during steam-assisted assembly have a particularly critical impact on the structure of the composite covalent organic framework membrane. If the membrane matrix surface is not sufficiently dried, as in Comparative Example 1, the residual liquid on its surface and in the internal pores will affect the continuous contact between the aldehyde monomer in solution A and the amino monomer in solution B, resulting in a thin and uneven covalent organic framework skin. If the evaporation rate of solution B is too fast, as in Comparative Example 2, it will cause the aldehyde monomer and amino monomer on the matrix surface to contact too quickly in a short time, making it difficult to match the time of crystalline reaction and formation, resulting in a loose covalent organic framework skin with high roughness.

[0093] Example 5:

[0094] The membranes prepared in Examples 1, 2, 3, and 4 were encapsulated into membrane modules using epoxy resin AB glue. Water vapor or air at 1 bar was introduced into the membrane modules, and the gas flow rate was monitored using a soap membrane flow meter. The water vapor permeability and water vapor / air selectivity of each fiber membrane were calculated. At the same time, the water vapor permeability of the fiber membrane after continuous water vapor introduction into the membrane module at 120°C for 200 h was investigated. The data in the table below are as follows.

[0095] Table 1 Comparison of membrane performance in the examples and comparative examples

[0096]

[0097] As shown in the table above, the water vapor / air selectivity of the high-temperature resistant composite covalent organic framework humidifying membranes prepared in Examples 1 and 2 is significantly higher than that of the membranes in Comparative Examples 3 and 4. Specifically, the water vapor / air selectivity of the high-temperature resistant composite covalent organic framework humidifying membrane prepared in Example 2 is as high as 1853, approximately 3 to 8 times that of the comparative membranes, while its water vapor permeability is 0.15 g / min. -1 cm -2 MPa -1 The permeability decay was less than 7% after 200 hours of durability at 120℃; the water vapor permeability of the composite membrane prepared in Example 1 was 0.17 g min. -1 cm -2 MPa -1 Furthermore, the permeability decrease after durability is less than 12%, demonstrating excellent high-temperature humidification performance of the composite covalent organic framework humidifying membranes prepared in Examples 1 and 2. This is mainly due to the special structure of the high-temperature resistant composite covalent organic framework humidifying membranes prepared in Examples 1 and 2. These membranes use a covalent organic framework crystalline layer as the outer skin, fully utilizing its regular and rigid channel structure to precisely sieve water vapor and air molecules, giving the membrane high water vapor / air selectivity, maintaining it within the range of 1620–1850°C. The well-developed microporous structure of the polysulfone porous layer within the membrane enhances the transmembrane transport of water vapor molecules, giving the membrane high water vapor permeability, reaching 0.15–0.17 g / min. -1 cm -2 MPa -1 However, in Comparative Example 3, the absence of a covalent organic framework crystal layer led to the reaction concentration of the covalent organic framework material in Comparative Example 4 exceeding the critical value, making it difficult to form a continuous and stable crystalline layer on the membrane surface, thus inhibiting the performance of the composite membrane.

[0098] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing a composite covalent organic framework humidification membrane, characterized in that, The method comprises the following steps: (1) dispersing polysulfone material, polyvinylpyrrolidone and polyethylene glycol in an organic solvent to obtain a casting solution; (2) preparing an organic solvent / water mixture with a volume fraction of 40%-90% as a coagulation bath; (3) coating the casting solution of step (1) on a glass plate, then transferring it to the coagulation bath after standing, and drying it at 25-120°C for 1-72 h after taking it out to obtain a membrane matrix; (4) preparing an organic solution A of covalent organic framework aldehyde monomer with a mass concentration of 0.1%-0.5%, immersing the membrane matrix in the organic solution A, and keeping it at 25-60°C for 10-30 s, then taking it out and standing at room temperature for 4-8 h; (5) preparing an organic solution B of covalent organic framework amino monomer with a mass concentration of 0.15%-0.75%, transferring the organic solution B to a heating kettle, fixing the membrane matrix on the top of the heating kettle with the surface of the membrane matrix facing downward, resetting nitrogen in the heating kettle, and setting the temperature of the heating kettle to 80-150°C to obtain a high-temperature-resistant composite covalent organic framework humidification membrane.

2. The method according to claim 1, wherein in step (1), the polysulfone material comprises one or more of polysulfone, polyethersulfone, polyphenylsulfone, sulfonated polysulfone, sulfonated polyethersulfone, and sulfonated polyphenylsulfone; and in the casting solution, the mass concentration of the polysulfone material is 14%-22%, the mass concentration of polyvinylpyrrolidone is 0.2%-5%, and the mass concentration of polyethylene glycol is 0.2%-5%.

4. The method according to claim 1, wherein in step (4), the covalent organic framework aldehyde monomer is one of triformylphloroglucinol and trimesaldehyde; and in step (5), the covalent organic framework amino monomer is one of diamino benzenesulfonic acid and diamino benzoic acid. Step (1), the organic solvent is dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, N - any one of methylpyrrolidone; Step (2), the organic solvent is dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, N - any one of methylpyrrolidone.

3. The preparation method according to claim 1, characterized in that, 5. The method according to claim 1, wherein in step (4), the organic solvent used in the organic solution A is any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, carbon tetrachloride, and N-methyl pyrrolidone; and in step (5), the organic solvent used in the organic solution B is any one of methanol, ethanol, toluene, and dichloromethane.

6. The method according to claim 1, wherein in step (3), the standing time is 5-15 s, and the soaking time is 5-15 min; and in step (5), the rotation speed of the workbench on the top of the membrane is set to 1-20 r / s, and the evaporation time is set to 1-48 h. The method is prepared according to any one of claims 1-6. The method comprises the following components: a matrix composed of a covalent organic framework crystalline layer and a polysulfone material; wherein the covalent organic framework crystalline layer is uniformly distributed on the outer surface of the matrix, forming a high-temperature-resistant crystalline skin layer with a thickness of 100-200 nm and a roughness of 60-80 nm; and the matrix composed of the polysulfone material has a finger-like pore structure in cross-section, forming a composite covalent organic framework humidification membrane with a thickness of 100-300 μm. ​ ​ ​ ​ ​ 7. A high temperature resistant composite type covalent organic framework humidification membrane, characterized in that, ​ 8. The high temperature resistant composite-type covalent organic framework humidification membrane of claim 7, wherein, ​ ​ 9. The composite covalent organic framework humidification membrane of claim 8, wherein, The material of the covalent organic framework crystalline layer is any one of triformylphloroglucinol-p-phenylenediamine, triformylphloroglucinol-2,5-diaminobenzenesulfonic acid, triformylphloroglucinol-2,5-diaminobenzoic acid, triformylphloroglucinol-2,5-diaminobenzenephosphonic acid, triformophloroglucinol-p-phenylenediamine, triformylphloroglucinol-2,5-diaminobenzenesulfonic acid, triformylphloroglucinol-2,5-diaminobenzoic acid, and triformylphloroglucinol-2,5-diaminobenzenephosphonic acid.

10. Use of the high-temperature resistant composite covalent organic framework humidifying membrane according to any one of claims 7 to 9 in the water management process of a fuel cell proton exchange membrane.

Images