Covalent organic framework nanofiltration membrane based on thiazole connection as well as preparation method and application of covalent organic framework nanofiltration membrane

Abstract

The invention relates to a thiazole connection-based covalent organic framework nanofiltration membrane as well as a preparation method and application thereof. Amphiphilic thiamine-containing monomers and aldehyde monomers are used as interfacial polymerization monomers, and polymerization is performed on a liquid-liquid free interface to obtain the covalent organic framework nanofiltration membrane with thiazole bonds as connecting structure elements. The thiazole bond is used as a connecting element to improve the separation selectivity and acid resistance of the COF membrane, the molecule desalination selectivity of the thiazole-connected covalent organic framework nanofiltration membrane reaches 690, and the thiazole-connected covalent organic framework nanofiltration membrane can be stably stored for a long time in 12M HCl, can still stably run and be stored for a long time under the harsh conditions of mechanical stress, high temperature, strong corrosion and the like, and keeps excellent structural stability; the membrane can be used for membrane separation in a neutral environment or a strong acid environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of membrane separation, and particularly relates to a covalent organic framework nanofiltration membrane based on thiazole connection and a preparation method and application thereof. BACKGROUND

[0002] Molecular desalination and separation in a strong acid environment has wide application requirements in the new energy, chemical and pharmaceutical industries, involving acid recovery, acid purification, resource extraction and wastewater reuse and many other fields. Existing ion exchange and electrodialysis technologies generally have low efficiency, high energy consumption and poor material stability in strong acid conditions, resulting in insufficient separation selectivity and long-term durability. Membrane separation technology based on molecular size, shape difference and membrane-permeate interaction provides an ideal approach for sustainable liquid filtration due to its high energy efficiency, simple operation and miniaturization. However, the application of molecular desalination in a strong acid environment is significantly limited by the scarcity of effective membrane materials, which need to have solution processability, permeation selectivity and chemical stability.

[0003] Covalent organic framework (COF) materials, as crystalline porous materials connected by covalent bonds, have shown great potential in the field of membrane separation under harsh conditions due to their periodic and ordered pore structure, controllable chemical environment and good chemical stability. However, it still faces major challenges for COF thin films to maintain their microstructure and macrostructure in a strong acid environment. Even partial bond rupture or slight stacking separation can cause the membrane structure to collapse and ultimately lose separation selectivity. This instability is due to the inherent dynamic properties of COF materials: for example, the high nucleophilicity of reversible imine bonds makes them susceptible to proton-induced skeleton degradation; the limited π-conjugated system results in weak interlayer π-π interactions, which easily causes COF layer loosening or slipping. Although various modification strategies have been developed, including reducing the nucleophilicity of C=N bonds, enhancing intramolecular / interlayer hydrogen bonds, optimizing molecular docking and utilizing resonance stabilization, none of these methods can fundamentally change the dynamic properties of COF materials. Therefore, COF membrane materials that can withstand strong acid environments while maintaining complete mass transfer channels are still very rare.

[0004] Studies have shown that specific interactions between heteroatoms in the COF skeleton and permeants are crucial for transmembrane mass transfer. However, the nitrogen atom in the traditional imine bond is embedded inside the framework, limiting its accessibility to solvents and solutes. Although the introduction of side chain groups such as sulfonic acid groups can improve the permeation selectivity of the material, these modified groups often face the problem of insufficient chemical stability in a strong acid environment. Developing a membrane material that has high chemical stability, excellent separation selectivity and scalable preparation for acid environments is still a key scientific problem that needs to be solved in this field. SUMMARY

[0005] To solve the above technical problems, the application provides a covalent organic framework nanofiltration membrane based on thiazole connection and a preparation method and application thereof.

[0006] The technical scheme adopted by the application is: a preparation method of a covalent organic framework nanofiltration membrane based on thiazole connection, in which amphiphilic sulfur-containing amine monomers and aldehyde monomers are used as interfacial polymerization monomers, and the covalent organic framework nanofiltration membrane based on thiazole connection is obtained through liquid-liquid free interface polymerization.

[0007] Preferably, the amine monomer is 2,5-diamino-1,4-benzenedithiol dihydrochloride, and the aldehyde monomer is 1,3,5-benzene triformaldehyde or 1,3,5-tris(p-formylphenyl) benzene (TFPB).

[0008] Preferably, the molar ratio of the amine monomer to the aldehyde monomer is 1:0.4-0.9, preferably 1:0.67.

[0009] Preferably, the specific preparation method is as follows:

[0010] Step one: dissolve the amine monomer in 1-fold volume of N,N-dimethylformamide, and then add 4-fold volume of water to form a clear mixed solvent as an aqueous phase solution; dissolve the aldehyde monomer and the catalyst in an organic solvent to obtain an organic phase solution;

[0011] Step two: first inject the aqueous phase solution into a reaction container, and then inject the organic phase solution to form a stable interface, and then place the reaction container at room temperature for 2-7 days of interfacial polymerization reaction, so that the covalent organic framework nanofiltration membrane based on thiazole connection is formed at the interface.

[0012] Preferably, when the aldehyde monomer is 1,3,5-benzene triformaldehyde, the catalyst is nonanoic acid, and the organic phase solvent is mesitylene; when the aldehyde monomer is 1,3,5-tris(p-formylphenyl) benzene, the catalyst is acetic acid, and the organic phase solvent is dichloromethane.

[0013] Preferably, the concentration of the amine monomer in the aqueous phase solution is 0.5-2 mM.

[0014] Preferably, the concentration of the aldehyde monomer in the organic phase solution is 0.33-1.33 mM, and the concentration of the catalyst is 200-700 mM.

[0015] The covalent organic framework nanofiltration membrane based on thiazole connection is prepared by the preparation method of the covalent organic framework nanofiltration membrane based on thiazole connection.

[0016] The covalent organic framework nanofiltration membrane based on thiazole connection is applied to a material for membrane separation technology.

[0017] Preferably, the covalent organic framework nanofiltration membrane based on thiazole connection is used for molecular desalination, resource extraction, resource purification or wastewater recovery in a neutral environment or an acidic environment.

[0018] The thiazole-connected covalent organic framework nanofiltration membrane has the advantages and positive effects that the thiazole-connected covalent organic framework nanofiltration membrane has excellent permeation selectivity and excellent acid resistance, the obtained membrane material can still stably operate and be long-term stored under harsh conditions such as mechanical stress, high temperature and strong corrosion, and excellent structural stability is maintained, the preparation process of the thiazole-connected covalent organic framework nanofiltration membrane is simple, and the thiazole-connected covalent organic framework nanofiltration membrane has universality and scalability, and is easy to popularize in industry. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 SEM image of the thiazole-connected COF membrane;

[0020] Figure 2 XRD characterization result of the thiazole-connected COF membrane 13 C ssNMR characterization result;

[0021] Figure 3 Comparison of pure water fluxes of the thiazole-connected COF membrane and the imine-connected COF membrane;

[0022] Figure 4 Comparison of selectivity factors of the thiazole-connected COF membrane and the imine-connected COF membrane in a ceftriaxone sodium / sodium chloride binary separation system;

[0023] Figure 5 Comparison of retention rates of the thiazole-connected COF membrane and the imine-connected COF membrane for chrome black T after being soaked in 12M hydrochloric acid for different time. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described below in combination with the drawings.

[0025] The present application relates to a thiazole-connected covalent organic framework nanofiltration membrane and a preparation method and application thereof. A thiazole-connected covalent organic framework (COF) membrane is constructed by taking thiazole bond as a connecting structure unit, and by taking an amphiphilic sulfur-containing amine monomer and an aldehyde monomer as interfacial polymerization monomers, Schiff base reaction occurs at a liquid-liquid free interface, and a thiazole-connected covalent organic framework nanofiltration membrane is obtained by polymerization.

[0026] The thiazole-connected covalent organic framework nanofiltration membrane has the following specific steps:

[0027] Step one: the amphiphilic sulfur-containing amine monomer is first dissolved in 1 times volume of N,N-dimethylformamide and uniformly ultrasonically treated, 4 times volume of water is then added to form a clear mixed solvent, and a water phase solution is obtained; the concentration of the sulfur-containing amine monomer in the water phase solution is 0.5-2mM;

[0028] The aldehyde monomer and the catalyst are dissolved in an organic solvent to obtain an organic phase solution; the concentration of the aldehyde monomer in the organic phase solution is 0.33-1.33 mM, and the concentration of the catalyst is 200-700 mM; the molar ratio of the amine monomer to the aldehyde monomer is 1:0.4-0.9; preferably 1:0.67;

[0029] wherein the amine monomer is 2,5-diamino-1,4-benzenedithiol dihydrochloride (Ba), the aldehyde monomer is 1,3,5-benzene tricarboxaldehyde (Tb) or 1,3,5-tris(p-formylphenyl) benzene (TFPB); when the aldehyde monomer is 1,3,5-benzene tricarboxaldehyde, the catalyst is nonanoic acid, and the organic phase solvent is mesitylene; when the aldehyde monomer is 1,3,5-tris(p-formylphenyl) benzene, the catalyst is acetic acid, and the organic phase solvent is dichloromethane.

[0030] Step two: first inject the aqueous phase solution into the glass container, then inject the organic phase solution to form a stable interface, and then carry out interfacial polymerization reaction, and then stand still at room temperature for 3-7 days, to form a self-supporting thiazole-linked covalent organic framework nanofiltration membrane at the interface, in the form of a yellow thin film;

[0031] Step three: after the interfacial polymerization reaction is completed, the thiazole-linked covalent organic framework nanofiltration membrane at the interface is collected, washed with N,N-dimethylformamide and methanol for 3 times to remove unreacted sulfur-containing amine monomers and aldehyde monomers, and then the self-supporting thiazole-linked covalent organic framework nanofiltration membrane is transferred to a support bottom for drying for 12 hours.

[0032] As a key structural unit, the thiazole bond can realize the spatial exposure of heteroatoms and the organic combination of the fully conjugated framework structure. This structure not only enhances the bonding energy and stacking energy, but also strengthens the atomic level hydration, driving the formation of a lone pair electron network in the channel. These synergistic effects collectively improve the separation selectivity and acid resistance of the COF membrane. It is found that the molecular desalination selectivity of the prepared thiazole-linked covalent organic framework nanofiltration membrane reaches 690, and it can be stably stored in 12M HCl for a long time.

[0033] Aromatic heterocyclic thiazole is used as a linking unit to construct a fully π-conjugated COF material. Density functional theory calculations show that the thiazole bond has an intrinsic high bond energy (5.39-9.42 eV), which is significantly better than that of the imine bond (4.23-7.83 eV) and the β-ketoenamine bond (4.77-8.16 eV), and the fully π-conjugated framework can significantly improve the interlayer π-π stacking efficiency. At the same time, the thiazole bond promotes the spatial exposure of the amphiphilic heteroatoms (N, S) in the channel. These negatively charged active sites can regulate the material transmission and induce the ordered arrangement of local water molecules at the liquid-COF interface, thereby protecting the framework from proton attack. This unique thiazole-linked fully π-conjugated framework structure can simultaneously improve the separation performance and chemical stability of the COF membrane in strong acid molecular desalination.

[0034] The preparation method has universality and scalability, and can prepare a nanofiltration membrane with a diameter of more than 20 cm. The obtained membrane material can still stably operate and be long-term stored under harsh conditions such as mechanical stress, high temperature and strong corrosion, and has excellent structural stability. The thiazole-connected covalent organic framework nanofiltration membrane prepared can be used in membrane separation technology, and is used for molecular desalination, resource extraction or wastewater reuse and resource purification in a strong acid or neutral environment.

[0035] The present application will be described below in conjunction with the drawings, wherein the experimental methods of the operation steps not specifically described are performed according to the corresponding product instructions. The instruments, reagents and consumables used in the examples can be purchased from commercial companies if not specifically stated.

[0036] Example 1:

[0037]

[0038] 2,5-diamino-1,4-benzenedithiol dihydrochloride (Ba) monomer was dissolved in N,N-dimethylformamide, the concentration of Ba was 1 mM, and ultrasonic treatment was performed for 10 minutes to ensure complete dissolution. Then, 4 times the volume of ultrapure water was added to prepare an aqueous phase solution.

[0039] 1,3,5-benzene tricarboxaldehyde (Tb) monomer and nonanoic acid were dissolved in mesitylene, the concentration of Tb was 0.67 mM, and the concentration of nonanoic acid was 500 mM. Ultrasonic treatment was performed for 15 minutes to ensure complete dissolution of the components to prepare an organic phase solution.

[0040] The organic phase solution and the aqueous phase solution were sequentially injected into a reaction container, and a stable interface was formed by layering. A yellow film was formed at the interface after 3 days of reaction. After the reaction was completed, the thiazole-connected covalent organic framework nanofiltration membrane at the interface was collected, washed with N,N-dimethylformamide and methanol for 3 times to remove unreacted sulfur-containing amine monomers and aldehyde monomers, and the thiazole-connected COF membrane was transferred to a support substrate and dried for 12 h to obtain a thiazole-connected COF membrane that can be used for nanofiltration separation.

[0041] The micro-morphology and structure of the prepared thiazole-connected COF membrane were characterized, and the results are shown in FIGS. 1-2. Figure 1 Figure 2 As shown by SEM, the thiazole-connected COF membrane has a good membrane morphology, which proves that the thiazole COF unit grows in the form of a continuous film in a large area and a long range. The ssNMR graph confirms that the thiazole-connected COF membrane has the expected skeleton chemical structure, and is confirmed as a thiazole-connected structure.

[0042] Example 2:

[0043] The 2,5-diamino-1,4-benzenediithiol dihydrochloride (Ba) monomer was dissolved in N,N-dimethylformamide with a concentration of 0.5 mM, and was sonicated for 10 minutes to ensure complete dissolution. Then, 4 times volume of ultrapure water was added to prepare the aqueous phase solution.

[0044] The 1,3,5-benzene tricarboxaldehyde (Tb) monomer and nonanoic acid were dissolved in mesitylene with a concentration of 0.33 mM for Tb and 200 mM for nonanoic acid, and were sonicated for 15 minutes to ensure complete dissolution of the components to prepare the organic phase solution.

[0045] The organic phase solution and the aqueous phase solution were sequentially injected into the reaction vessel, and a stable interface was formed between the two layers. A yellow film was formed at the interface after 3 days of reaction. After the reaction was completed, the thiazole-linked covalent organic framework nanofiltration membrane at the interface was collected, washed 3 times with N,N-dimethylformamide and methanol to remove unreacted sulfur-containing amine monomers and aldehyde monomers, and the thiazole-linked COF membrane was transferred to a support substrate and dried for 12 h to obtain a thiazole-linked COF membrane that can be used for nanofiltration separation.

[0046] Example 3:

[0047] The 2,5-diamino-1,4-benzenediithiol dihydrochloride (Ba) monomer was dissolved in N,N-dimethylformamide with a concentration of 1.5 mM, and was sonicated for 10 minutes to ensure complete dissolution. Then, 4 times volume of ultrapure water was added to prepare the aqueous phase solution.

[0048] The 1,3,5-benzene tricarboxaldehyde (Tb) monomer and nonanoic acid were dissolved in mesitylene with a concentration of 1.0 mM for Tb and 400 mM for nonanoic acid, and were sonicated for 15 minutes to ensure complete dissolution of the components to prepare the organic phase solution.

[0049] The organic phase solution and the aqueous phase solution were sequentially injected into the reaction vessel, and a stable interface was formed between the two layers. A yellow film was formed at the interface after 3 days of reaction. After the reaction was completed, the thiazole-linked covalent organic framework nanofiltration membrane at the interface was collected, washed 3 times with N,N-dimethylformamide and methanol to remove unreacted sulfur-containing amine monomers and aldehyde monomers, and the thiazole-linked COF membrane was transferred to a support substrate and dried for 12 h to obtain a thiazole-linked COF membrane that can be used for nanofiltration separation.

[0050] Example 4:

[0051] The 2,5-diamino-1,4-benzenediithiol dihydrochloride (Ba) monomer was dissolved in N,N-dimethylformamide with a concentration of 2 mM, and was sonicated for 10 minutes to ensure complete dissolution. Then, 4 times volume of ultrapure water was added to prepare the aqueous phase solution.

[0052] The 1,3,5-benzene tricarboxaldehyde (Tb) monomer and nonanoic acid were dissolved in mesitylene, the concentration of Tb was 1.33 mM, the concentration of nonanoic acid was 700 mM, and the solution was ultrasonically treated for 15 minutes to ensure complete dissolution of the components to prepare an organic phase solution.

[0053] The organic phase solution and the aqueous phase solution were sequentially injected into a reaction vessel, and a stable interface was formed by layering, and a yellow film was formed at the interface after 3 days of reaction. After the reaction was completed, the thiazole-linked covalent organic framework nanofiltration membrane at the interface was collected, washed 3 times with N,N-dimethylformamide and methanol to remove unreacted sulfur-containing amine monomers and aldehyde monomers, and the thiazole-linked COF membrane was transferred to a support substrate and dried for 12 h to obtain a thiazole-linked COF membrane that can be used for nanofiltration separation.

[0054] Comparative Example:

[0055] The p-phenylenediamine (Pa) was dissolved in N,N-dimethylformamide, the concentration of Pa was 1.5 mM, and after ultrasonic treatment for 10 min, ultrapure water was added to prepare an aqueous phase solution.

[0056] The 1,3,5-benzene tricarboxaldehyde (Tb) and nonanoic acid were dissolved in mesitylene, the concentration of Tb was 1 mM, the concentration of nonanoic acid was 50 mM, and the solution was ultrasonically treated for 15 minutes to ensure complete dissolution of the components to prepare an organic phase solution.

[0057] The organic phase solution and the aqueous phase solution were sequentially injected into a reaction vessel, and a stable interface was formed by layering, and a brown film was formed at the interface after 2 days of reaction. After the reaction was completed, the self-supported imine-linked COF membrane was washed 3 times with N,N-dimethylformamide and methanol to remove unreacted sulfur-containing amine monomers and aldehyde monomers, and the self-supported imine-linked COF membrane was transferred to a support substrate and dried for 12 h to obtain an imine-linked COF membrane that can be used for nanofiltration separation.

[0058] Example 5: Comparison of performance of thiazole-linked COF membrane and imine-linked COF membrane

[0059] 5.1 Comparison of permeation performance

[0060] The pure water fluxes of the thiazole-linked COF membrane prepared in Example 1 and the imine-linked COF membrane prepared in the comparative example were compared.

[0061] The two COF membranes were respectively transferred to a polyether sulfone (PES) microfiltration membrane support substrate with a pore size of 0.22 μm, and were cut into circular or square membrane pieces suitable for the size of the membrane cell. The membrane pieces were installed in a dead-end or cross-flow filtration device, and the feed liquid was deionized water. Before testing, the membrane layer was compacted to a stable flux by applying a pressure of 2 bar for 0.5 h, and then the pure water flux was tested under a pressure of 2 bar. The results are shown in Figure 3 The test showed that the flux of the thiazole-linked COF membrane reached 95.8 LMH MPa -1, the COF membrane linked by thiazole (56.9 LMH MPa -1 ) increased by 68.4%, which proved that the permeability of the COF membrane linked by thiazole was much higher than that of the COF membrane linked by imine.

[0062] 5.2 Separation performance comparison

[0063] The separation ability of the COF membrane linked by thiazole prepared in Comparative Example 1 and the COF membrane linked by imine prepared in the Comparative Example in the ceftriaxone sodium / sodium chloride system was compared. The two COF membranes were respectively transferred to a polyether sulfone (PES) microfiltration membrane support substrate with a pore size of 0.22 μm, and were cut into circular or square membrane pieces suitable for the size of the membrane cell. The membrane pieces were installed in a dead-end or cross-flow filtration device, and the feed liquid was an aqueous solution containing ions and molecules. Before testing, the membrane layer was compacted to a stable flux under a pressure of 2 bar for 0.5 h, and then the pure water flux was tested under a pressure of 2 bar.

[0064] The test results of the molecular / salt binary system are shown in Table 2. Figure 4 As shown in Table 2, the separation factor of the COF membrane linked by thiazole in the ceftriaxone sodium / sodium chloride binary separation system reached 690.0, which was significantly better than that of the COF membrane linked by imine (the separation factor in the ceftriaxone sodium / sodium chloride binary separation system was 10.67).

[0065] 5.3 Membrane stability analysis

[0066] The stability of the COF membrane linked by thiazole prepared in Comparative Example 1 and the COF membrane linked by imine prepared in the Comparative Example was compared. Both were respectively immersed in 12M HCl, and after a period of immersion, the integrity of the COF membrane was detected, and the molecular retention rate of chrome black T was detected. The results are shown in Table 3. Figure 5 As shown in Table 3, the structure of the COF membrane linked by thiazole remained intact after being immersed in 12M HCl for 504 hours, and the molecular retention rate remained above 99.2%, indicating that the mass transfer channel remained intact under strong acid conditions. The molecular retention rate of the COF membrane linked by imine decreased significantly from 99.9% to 64.5% after being immersed in 12M HCl for 504 h, which proved that the channel structure was irreversibly damaged and lost the molecular sieving ability. The COF membrane linked by thiazole exhibited extraordinary stability compared to the COF membrane linked by imine under strong acidic conditions.

[0067] Through the above experimental comparison, the COF membrane linked by thiazole has excellent permeation selectivity and acid resistance.

[0068] Example 6:

[0069] The 2,5-diamino-1,4-benzenedithiol dihydrochloride (Ba) monomer was dissolved in N,N-dimethylformamide, the concentration of Ba was 2 mM, and it was fully dissolved by ultrasonic treatment for 10 minutes, then 4 times the volume of ultrapure water was added to prepare the aqueous phase solution.

[0070] The 1,3,5-tris(p-formylphenyl)benzene (TFPB) monomer was dissolved in dichloromethane, the concentration of TFPB was 1.33 mM, and the concentration of acetic acid was 200 mM, and the components were fully dissolved by ultrasonic treatment for 15 minutes to prepare the organic phase solution.

[0071] The organic phase solution and the aqueous phase solution were sequentially injected into the reaction container, and a stable interface was formed by layering, and a yellow film was formed at the interface after 3 days of reaction. After the reaction was completed, the thiazole-linked covalent organic framework nanofiltration membrane at the interface was collected, and unreacted sulfur-containing amine monomers and aldehyde monomers were removed by washing 3 times with N,N-dimethylformamide and methanol, and the thiazole-linked COF membrane was transferred to a support substrate and dried for 12 h to obtain a thiazole-linked COF membrane that can be used for nanofiltration separation.

[0072] The thiazole-linked COF membrane prepared has similar structural properties and performance to Example 1, and has excellent permeation selectivity and excellent acid resistance. It was detected that the prepared thiazole-linked COF membrane has a pure water flux of 1247.5 LMH / MPa, and the rejection rate of chrome black T can reach more than 95%.

[0073] The above describes the embodiments of the present application in detail, but the content described is only the preferred embodiments of the present application, and cannot be considered as limiting the scope of the implementation of the present application. Any equivalent changes and improvements made in the scope of the present application should still be attributed to the scope of the patent of the present application.

Claims

1. A method for preparing a thiazole-linked covalent organic framework nanofiltration membrane, characterized in that: Using amphiphilic sulfur-containing amine monomers and aldehyde monomers as interfacial polymerization monomers, thiazole-linked covalent organic framework nanofiltration membranes were obtained by polymerization at a liquid-liquid free interface.

2. The method for preparing a thiazole-linked covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The amine monomer is 2,5-diamino-1,4-benzenedithiol dihydrochloride, and the aldehyde monomer is 1,3,5-benzenetriformaldehyde or 1,3,5-tris(p-formylphenyl)benzene.

3. The method for preparing a thiazole-linked covalent organic framework nanofiltration membrane according to claim 2, characterized in that: The molar ratio of amine monomer to aldehyde monomer is 1:0.4-0.

9.

4. The method for preparing a thiazole-linked covalent organic framework nanofiltration membrane according to any one of claims 1-3, characterized in that: The specific preparation method is as follows: Step 1: Dissolve the amine monomer in 1 volume of N,N-dimethylformamide, and then add 4 volumes of water to form a clear mixed solvent as an aqueous solution; dissolve the aldehyde monomer and the catalyst in a homogeneous organic solvent to obtain an organic solution. Step 2: First, inject an aqueous phase solution into the reaction vessel, then inject an organic phase solution to form a stable interface. Allow the interface polymerization reaction to proceed at room temperature for 2-7 days to form a thiazole-linked covalent organic framework nanofiltration membrane at the interface.

5. The method for preparing a thiazole-linked covalent organic framework nanofiltration membrane according to claim 4, characterized in that: When the aldehyde monomer is 1,3,5-benzyltrimethylaldehyde, the catalyst is nonanoic acid, and the organic solvent is mesitylene. When the aldehyde monomer is 1,3,5-tris(p-formylphenyl)benzene, the catalyst is acetic acid, and the organic solvent is dichloromethane.

6. The method for preparing a thiazole-linked covalent organic framework nanofiltration membrane according to claim 4, characterized in that: The concentration of amine monomers in the aqueous solution is 0.5-2 mM.

7. The method for preparing a thiazole-linked covalent organic framework nanofiltration membrane according to claim 4, characterized in that: The concentration of aldehyde monomer in the organic phase solution is 0.33-1.33 mM, and the concentration of catalyst is 200-700 mM.

8. A thiazole-linked covalent organic framework nanofiltration membrane prepared by any of the preparation methods of the thiazole-linked covalent organic framework nanofiltration membrane according to any one of claims 1-7.

9. The application of the thiazole-linked covalent organic framework nanofiltration membrane as described in claim 8 in membrane separation technology materials.

10. The application according to claim 9, characterized in that: Used for molecular desalination, resource extraction, resource purification, or wastewater recycling in neutral or acidic environments.

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