Covalent organic framework composite membrane material with bionic structure design as well as preparation and application of covalent organic framework composite membrane material

Abstract

The invention belongs to the technical field of covalent organic framework separation membranes, and discloses a covalent organic framework composite membrane material with bionic structure design and preparation and application thereof, and a preparation method comprises the following steps: (1) preparing an oil phase solution and a water phase solution; (2) fixing the porous support substrate on an H-shaped diffusion cell, and adding the aqueous phase solution and the oil phase solution; (3) inserting a first electrode and a second electrode, sealing and carrying out polymerization reaction to obtain a covalent organic framework membrane; (4) washing; and (5) adding a small molecule aqueous solution capable of being combined with target ions to be separated, and obtaining the covalent organic framework composite membrane material in an electrochemical deposition mode. According to the invention, the aldehyde group monomer and the amino monomer are utilized to form the covalent organic framework membrane through interfacial polymerization, and then micromolecules capable of being combined with target ions to be separated are limited into a membrane channel in an electrochemical deposition manner, so that the ion screening performance of the covalent organic framework composite membrane can be efficiently enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of covalent organic framework separation membranes, and more specifically, relates to a covalent organic framework composite membrane material with a biomimetic structural design, and the preparation and application thereof. Background Art

[0002] Ion selective separation technology has gradually become a research hotspot in the field of resources and environment due to its key role in resource recovery, environmental governance and sustainable development. With the continuous growth of global resource demand and the increasingly severe environmental problems, traditional separation technologies are facing the problems of low processing efficiency, high cost and high energy consumption. As a separation method with high selectivity, low energy consumption and strong adaptability, ion selective separation technology has shown great potential in many resource and environmental applications. Among them, separation membrane technology, as an efficient material separation method, has been widely used in many fields such as water treatment (Yuan Chengzong. A superhydrophobic separation membrane and its preparation method CN202510279469.1), gas separation (Zhao Song. A gas separation membrane based on metal organic cages and its preparation method and application CN202510268531.7), and drug separation.

[0003] Covalent Organic Frameworks (COFs) are a new type of porous material with high specific surface area, adjustable pore size, excellent chemical stability and rich functional group modification capabilities, showing great potential in ion screening and selective separation. In particular, membrane materials prepared based on COFs not only retain the excellent properties of COFs, but also have the high efficiency of membrane separation, becoming a frontier direction of research in the field of ion selective separation and recovery. Current related research mainly focuses on the surface chemical environment and functional groups of the COF structure itself to achieve ion separation. At the same time, the preparation method of covalent organic framework membranes is relatively complicated, with slow film formation speed and difficulty in forming long-range ordered structures, resulting in uneven pores or more defects, which leads to poor separation effect and difficulty in achieving accurate ion separation. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the purpose of the present invention is to provide a covalent organic framework composite membrane material with a biomimetic structural design and its preparation and application. The covalent organic framework membrane is first formed by interfacial polymerization of aldehyde monomers and amino monomers, and then small molecules that can bind to the target ions to be separated are confined to the membrane channels by electrochemical deposition to obtain the covalent organic framework composite membrane material, which can effectively enhance the ion screening performance of the covalent organic framework composite membrane. In addition, the present invention has a simple structure and high separation efficiency, and can be widely used in fields such as seawater desalination and heavy metal recovery.

[0005] To achieve the above object, according to one aspect of the present invention, a method for preparing a covalent organic framework composite membrane material is provided, characterized in that it comprises the following steps:

[0006] (1) using an organic solvent immiscible with water as a first solvent and an aqueous phase solvent as a second solvent, dissolving an aldehyde monomer in the first solvent to obtain an oil phase solution, and dissolving an amino monomer in the second solvent to obtain an aqueous phase solution; the oil phase solution and the aqueous phase solution are immiscible with each other;

[0007] (2) fixing a porous support substrate on an H-type diffusion cell, and then adding the aqueous solution and the oil phase solution to both sides of the H-type diffusion cell, respectively; wherein the smooth surface of the porous support substrate is in direct contact with the oil phase solution;

[0008] (3) inserting a first electrode and a second electrode into the oil phase solution and the aqueous phase solution of the H-type diffusion cell obtained in step (2), respectively, and then sealing the H-type diffusion cell and applying a voltage to perform a polymerization reaction, thereby obtaining a covalent organic framework membrane on a porous support substrate; wherein the voltage is 50-120 V and the reaction time is 12-72 h;

[0009] (4) draining the aqueous phase solution and the oil phase solution in the H-type diffusion cell obtained in step (3), then adding a third solvent to both sides of the H-type diffusion cell for soaking, washing to remove residual unreacted monomers, and then draining the cell to obtain a covalent organic framework membrane; wherein the third solution is an organic solvent;

[0010] (5) adding a small molecule aqueous solution capable of binding to the target ions to be separated to both sides of the H-type diffusion cell obtained in step (4), wherein the concentration of the small molecule solution is 0.5-10 mg / mL, and obtaining a covalent organic framework composite membrane material by electrochemical deposition; wherein the electrochemical deposition time is 5-72 h, and the electrochemical applied voltage is 10-100 V.

[0011] As a further preference of the present invention, in step (1), the aldehyde monomer is any one of trimesaldehyde, 2-hydroxy-1,3,5-benzenetricarboxaldehyde, trialdehyde phloroglucinol, tris(4-formylphenyl)amine, and 1,3,5-tris(p-formylphenyl)benzene;

[0012] The amino monomer is any one of hydrated hydrazine, p-phenylenediamine, triaminoguanidine hydrochloride, 1,3,5-tris(aminomethyl)benzenetrihydrochloride, 1,3,5-triaminobenzene hydrochloride, and 1,2,4,5-benzenetetramine tetrahydrochloride;

[0013] The first solvent is any one of dichloromethane, toluene, mesitylene, and ethyl acetate, or a mixed solvent of mesitylene and ethyl acetate, or a mixed solvent of toluene and ethyl acetate;

[0014] The second solvent is any one of acetic acid solution, hydrochloric acid solution, trifluoroacetic acid, and p-toluenesulfonic acid solution;

[0015] The ratio of the molar amount of the aldehyde monomer, the molar amount of the amino monomer and the volume of the first solvent meets the requirement of (0.1-1.0) mmol: (0.2-2.0) mmol: (20-50) mL; the volume of the first solvent is equal to the volume of the second solvent.

[0016] As a further preference of the present invention, in step (2), the porous supporting substrate is one of a polyacrylonitrile substrate, a polyvinyl alcohol substrate, a polyvinylidene fluoride substrate, a polytetrafluoroethylene substrate, and an alumina substrate.

[0017] As a further preferred embodiment of the present invention, in step (1), the aldehyde monomer is dissolved in the first solvent by ultrasound; preferably, the ultrasound time is 5 to 15 minutes;

[0018] The amino monomer is dissolved in the second solvent by ultrasound; preferably, the ultrasound time is 5 to 15 minutes.

[0019] As a further preferred embodiment of the present invention, in step (4), the third solvent is any one or more of ethanol, methanol, acetone, and tetrahydrofuran.

[0020] As a further preference of the present invention, in step (5), the target ion to be separated is Na + , K + 、Li + , Ca 2+ Mg 2+ One ion or multiple ions with the same valence state;

[0021] (I) When the cations present in the system to be separated are all +1 valence ions:

[0022] i. When the target ion to be separated is Na + When the small molecule is 15-crown-5 (15C5);

[0023] ii. When the target ion to be separated is K + When the small molecule is 18-crown-6 (18C6);

[0024] iii. When the target ion to be separated is Li +When the small molecule is any one of 12-crown-4 (12C4) and benzo-12-crown-4 (DB12C4);

[0025] (II) When the cations present in the system to be separated include both +1-valent ions and +2-valent ions, the target ions to be separated are +1-valent ions, and the small molecule is any one of p-phenylenediamine, ethylenediaminetetraacetic acid, crown ether, calixarene, and cyclodextrin.

[0026] As a further preferred embodiment of the present invention, in step (5), the temperature of the electrochemical deposition is 20-40°C.

[0027] According to another aspect of the present invention, the present invention provides a covalent organic framework composite membrane material prepared by the above preparation method.

[0028] According to another aspect of the present invention, the present invention provides the use of the above-mentioned covalent organic framework composite membrane material as membrane separation.

[0029] As a further preference of the present invention, the application is specifically the application of membrane separation in the process of ion separation; preferably, the application is specifically the application in the separation between monovalent cations and the separation of monovalent ions and divalent ions.

[0030] As a further preferred embodiment of the present invention, the application is specifically for seawater desalination or extraction of lithium resources in salt lakes.

[0031] Through the above technical solutions conceived by the present invention, compared with the prior art, the covalent organic framework composite membrane material obtained by the present invention is a COF membrane with an ordered and adjustable pore interior and a positive charge prepared by electrochemical interfacial polymerization, and on this basis, small molecules are introduced by electrochemical deposition, and the molecules are fixed in the pores by electrostatic attraction, host-guest interaction and confinement effect to finally form a covalent organic framework composite membrane material. The present invention improves the pore size distribution and functionalization of the covalent organic framework membrane, and introduces small molecules that have a binding function with the target ions to be separated. While reducing the pore size of the covalent organic framework membrane to better match the size of the ions for screening, the pore structure is changed to form a conical structure. While ensuring the ion recognition and screening function, it also has an ion diffusion effect to increase the ion flux. The functional small molecule material that can identify the target ions can effectively enhance the ion screening efficiency.

[0032] The present invention forms a composite membrane by introducing a small molecule material with a target ion recognition function into the covalent organic framework membrane channel. The functional small molecule material not only effectively reduces the pore size of the covalent organic framework membrane but also enhances the ion screening performance of the covalent organic framework composite membrane. The present invention designs pore matching, and contains a covalent organic framework membrane with a positive potential point in the pore channel. On this basis, a small molecule material with a binding function to the same ion is introduced into the channel and fixed inside the pore channel, thereby regulating the pore size, pore structure and pore chemical environment of the covalent organic framework membrane, achieving effective regulation of the pore structure of the covalent organic framework membrane. At the same time, the small molecule with a binding function to the ion can efficiently enhance the ion screening performance of the covalent organic framework composite membrane.

[0033] The covalent organic framework composite membrane material obtained by the present invention can achieve precise ion separation, which is similar to the precise separation effect of biological organisms and has bionic characteristics.

[0034] Specifically, the present invention can achieve the following beneficial effects:

[0035] (1) The covalent organic framework membrane of the present invention is formed by a confined interfacial polymerization reaction under the action of an external electric field. This process makes the orientation of the entire covalent organic framework channel more orderly. At the same time, the prepared membrane material is relatively thin, which can significantly reduce the transmission resistance and thus improve the ion separation flux.

[0036] Moreover, similar to other covalent organic framework membranes in the prior art, the covalent organic framework membrane in the present invention has good mechanical strength and flexibility, stable chemical properties, high specific surface area, adjustable pore size, excellent chemical stability and rich functional group modification capabilities.

[0037] (2) In the present invention, a positively charged covalent organic framework membrane channel is composited with a small molecule material having ion recognition function. Through the confinement effect and electrostatic attraction between ions, the small molecule material is firmly fixed in the ion transmission channel, and a conical channel is formed to promote ion separation and improve the separation effect.

[0038] How to accurately introduce functional small molecules into COF channels and achieve stable loading while balancing ion selectivity and transmission efficiency is a key step in the preparation method. Traditional methods fail because small molecules are prone to aggregation, dissolution or clogging of pores. The present invention better combines small molecules with the interior of COF channels through electrochemical deposition. Under electrochemical action, the combination of small molecules with the functional groups and skeleton inside the COF channels is more stable, solving the problem of uneven distribution and stability of functional small molecules. At the same time, the present invention also optimizes the small molecule loading amount, controls the concentration of the small molecule solution to 0.5-10 mg / mL, controls the time of electrochemical deposition to 5-72h, and controls the applied voltage to 10-100V, while maintaining the COF crystallinity and maximizing the separation performance. For example, when the concentration of the small molecule solution exceeds 10 mg / mL, it will cause pore blockage (flux decreases by 50%), while when the concentration of the small molecule solution is lower than 0.5 mg / mL, it will lead to insufficient loading and reduced ion separation selectivity; when the loading time is too short, less than 5 hours, and the applied voltage is lower than 10V, the small molecules do not completely enter the COF channel, which will also lead to insufficient loading and poor ion separation effect; when the loading time is too long, higher than 72 hours, and the applied voltage is higher than 100V, it will cause pore blockage, resulting in a serious reduction in flux.

[0039] (3) The covalent organic framework separation membrane material of the present invention is particularly applicable to the precise separation of monovalent and divalent ions. Utilizing membrane separation technology, the present invention can recover monovalent metal elements and effectively remove divalent or heavy metal ions. High-value monovalent metal elements can be recovered from wastewater containing multiple metal ions. Separation membrane materials of varying sizes can be prepared and assembled into separation membrane devices to meet the needs of different application scenarios.

[0040] The present invention prepares a covalent organic framework membrane with a support membrane through interfacial polymerization under the action of electric field migration. By introducing the electric field effect during the synthesis process, the defects in the traditional covalent organic framework membrane synthesis process are reduced; through post-functionalization modification, the pore size and pore shape of the membrane are adjusted in the channel structure, thereby increasing the ion separation efficiency; at the same time, by introducing small molecules that can bind to the target ions to be separated near the inside of the pore, the overall separation efficiency of the covalent organic framework composite membrane material for different ions (especially monovalent and divalent ions) is further improved.

[0041] In summary, the present invention demonstrates a simple process and high ion separation efficiency, making it widely applicable to fields such as the recovery and separation of valuable elements. Based on the present invention, covalent organic framework membranes can be modified using different post-modified small molecules to prepare covalent organic framework composite membrane materials with biomimetic structural designs and different separation effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Surface morphology of the covalent organic framework membrane (TFP-Tag) obtained in comparative example 1 and the covalent organic framework composite membrane (TFP-Tag-EDTA) with a protein-like structure obtained in example 1; wherein, Figure 1 a in the corresponding covalent organic framework membrane (TFP-Tag) sample obtained in Example 1, Figure 1 b in the figure corresponds to the covalent organic framework composite membrane (TFP-Tag-EDTA) sample with protein-like structure design obtained in Example 1.

[0043] Figure 2 This is a Fourier transform infrared change spectrum of the raw material ethylenediaminetetraacetic acid (EDTA), the raw material triaminoguanidine hydrochloride (Tag), the raw material trimesaldehyde (TFP) used in Example 1, the covalent organic framework membrane (TFP-Tag) obtained in Comparative Example 1, and the covalent organic framework composite membrane (TFP-Tag-EDTA) with a protein-like structure design obtained in Example 1.

[0044] Figure 3 This is an XPS etching data diagram of the covalent organic framework membrane (TFP-Tag) obtained in Comparative Example 1 and the covalent organic framework composite membrane (TFP-Tag-EDTA) with a protein-like structure design obtained in Example 1.

[0045] Figure 4 This is a comparison chart of the ion selectivity of the covalent organic framework membrane (TFP-Tag) obtained in Comparative Example 1 and the covalent organic framework composite membrane (TFP-Tag-EDTA) with a protein-like structure design obtained in Example 1.

[0046] Figure 5 This is a comparison chart of the ion flux of the covalent organic framework membrane (TFP-Tag) obtained in Comparative Example 1 and the covalent organic framework composite membrane (TFP-Tag-EDTA) with a protein-like structure design obtained in Example 1. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0048] The polymer substrate used in the following embodiments is a commercially available polyacrylonitrile substrate with a molecular weight of 50,000 KDa, and a non-woven fabric on its back side (that is, the polyacrylonitrile substrate includes a non-woven fabric layer and a polyacrylonitrile layer located on the non-woven fabric layer, and the front side is the polyacrylonitrile layer, which is smooth).

[0049] Example 1

[0050] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0051] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0052] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0053] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as an electrode, and the electrode was used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution (of course, in addition to using ITO glass as a conductive material, other conductive materials such as common graphite, stainless steel, etc. can also be used to sandwich the conductive material on the platinum sheet to form an electrode as a whole). A voltage of 100 V was applied at room temperature and the reaction was carried out for 24 hours to obtain a covalent organic framework film;

[0054] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag). After washing in this step, a covalent organic framework membrane with open pores is obtained (the same below).

[0055] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at room temperature for 12 hours to obtain a covalent organic framework composite film material (TFP-Tag-EDTA).

[0056] Separation membrane performance test:

[0057] The ion selectivity test of the separation membrane is the ratio of the transmission rate of the membrane for different ions. The concentration diffusion experiment was carried out at room temperature using an H-type device. Monochloride salt was used as the feed solution and deionized water was used as the permeate side to measure the permeation rate of various metal ions. The feed side was filled with 50mL of 0.1M monochloride salt solution, and the permeate side was filled with the same volume of deionized water. Both the feed solution and the permeate were magnetically stirred to avoid concentration polarization near the membrane surface. The conductivity of the permeate chamber was recorded every 1 minute using a conductivity meter. Finally, the ion selectivity and ion flux were calculated according to the following formula:

[0058] P=(C×V) / (A×Δt)

[0059] S=P i / P j

[0060] Where P (unit: mol m -2 h -1 ) is the permeation rate, which can be obtained by the concentration of ions on the permeation side within a certain period of time (30min); A (unit: m 2 ) is the effective permeation area; Δt (unit: h) is the permeation time 0.5 h; V (unit: L) is the permeation side volume 50 mL; C (unit: mol / L) is the concentration of the monochloride salt solution on the feed side; P i and P j is the flux of two different ions; S is the ion selectivity.

[0061] The surface morphology of the samples modified with small molecules was tested, and the results were as follows: Figure 1 As shown in the figure, it is not difficult to see that the surface of the modified membrane material is smooth and defect-free. And through Fourier infrared spectroscopy ( Figure 2 ) to determine its structure, explaining the formation of its composite structure. At the same time, after XPS etching ( Figure 3 ) As the etching depth increases, the EDTA content decreases, which can further prove the conical structure of the composite film (that is, the covalent organic framework film obtained in step (4) has a one-dimensional straight-through channel, and after the small molecules are introduced in step (5), the amount of introduction is the largest near the surface; as the depth increases, the content of small molecules gradually decreases; therefore, the covalent organic framework composite film material obtained in step (5) has a conical structure channel, Figure 3 The XPS etching results shown also confirm this conclusion).

[0062] The ion selectivity test of TFP-Tag-EDTA membrane was carried out, and the results were as follows Figure 4 and Figure 5 As shown, Na + The ion flux can reach 27.8 mmol h -1 m -2 , Na + / Ca 2+ The selectivity can reach 184.8, Li + / Mg 2+ The selectivity can reach 101.9, Na + / Mg 2+ The selectivity can reach 154.

[0063] Example 2

[0064] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0065] (1) Dissolve trialdehyde phloroglucinol (28 mg) and triaminoguanidine hydrochloride (16.25 mg) in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time is 10 min;

[0066] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0067] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0068] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TP-Tag).

[0069] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at 40°C for 12 hours to obtain a covalent organic framework composite film material (TP-Tag-EDTA).

[0070] The ion selectivity of TP-Tag-EDTA membrane was tested, in which Na + The ion flux can reach 22.5 mmol h -1 m -2 , Na + / Ca 2+ Selectivity can reach 140, Li + / Mg 2+ The selectivity can reach 90, Na + / Mg 2+ The selectivity can reach 103.

[0071] Example 3

[0072] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0073] (1) 2-Hydroxy-1,3,5-benzenetricarboxaldehyde (26 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) by ultrasonication, respectively, to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0074] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0075] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0076] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (DHTA-Tag).

[0077] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at 20°C for 12 hours to obtain a covalent organic framework composite film material (DHTA-Tag-EDTA).

[0078] The ion selectivity of DHTA-Tag-EDTA membrane was tested, in which Na + The ion flux can reach 25.3 mmol h - 1 m -2 , Na + / Ca 2+ Selectivity can reach 120, Li + / Mg 2+ The selectivity can reach 80, Na + / Mg 2+ The selectivity can reach 100.

[0079] Example 4

[0080] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0081] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0082] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0083] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0084] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0085] (5) A 6 mg / mL aqueous solution of p-phenylenediamine was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 100 V was applied at room temperature for 12 h to obtain a covalent organic framework composite film material (TFP-Tag-PPA).

[0086] The ion selectivity of TFP-Tag-PPA membrane was tested, in which Na + The ion flux can reach 20.8 mmol h -1 m -2 , Na + / Ca 2+ The selectivity can reach 106, Li + / Mg 2+ The selectivity can reach 83, Na + / Mg 2+ The selectivity can reach 95%.

[0087] Example 5

[0088] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0089] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0090] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0091] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0092] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0093] (5) A 6 mg / mL aqueous solution of crown ether (18C6) was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 50 V was applied at room temperature for 72 hours to obtain a covalent organic framework composite membrane material (TFP-Tag-18C6).

[0094] The ion selectivity of TFP-Tag-18C6 membrane was tested, in which Na + The ion flux can reach 19.8 mmol h -1 m -2 , K + / Na + Selectivity can reach 2, Na + / Ca 2+ Selectivity can reach 100, Li + / Mg 2+ The selectivity can reach 60, Na + / Mg 2+ The selectivity can reach 80.

[0095] Example 6

[0096] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0097] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0098] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0099] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0100] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0101] (5) A 6 mg / mL β-cyclodextrin aqueous solution was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 50 V was applied at room temperature for 12 h to obtain a covalent organic framework composite film material (TFP-Tag-CD).

[0102] The ion selectivity of TFP-Tag-CD membrane was tested, in which Na + The ion flux can reach 15.8 mmol h -1 m -2 , Na + / Ca 2+ Selectivity can reach 60, Li + / Mg 2+ The selectivity can reach 35, Na + / Mg 2+ The selectivity can reach 40.

[0103] Example 7

[0104] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0105] (1) Trisaldehyde (25 mg) and 1,3,5-triaminobenzene hydrochloride (15 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0106] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0107] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0108] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-TA).

[0109] (5) A 10 mg / mL β-cyclodextrin aqueous solution was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 50 V was applied at room temperature for 12 h to obtain a covalent organic framework composite film material (TFP-TA-CD).

[0110] The ion selectivity of TFP-TA-CD membrane was tested, in which Na +The ion flux can reach 11.8 mmol h -1 m -2 , Na + / Ca 2+ The selectivity can reach 53, Li + / Mg 2+ The selectivity can reach 34, Na + / Mg 2+ The selectivity can reach 67.

[0111] Example 8

[0112] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0113] (1) Trisaldehyde (25 mg) and 1,3,5-tris(aminomethyl)benzenetrihydrochloride (15 mg) were dissolved in toluene (25 mL) and 3M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0114] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0115] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0116] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-PA).

[0117] (5) A 10 mg / mL β-cyclodextrin aqueous solution was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 50 V was applied at room temperature for 12 h to obtain a covalent organic framework composite membrane material (TFP-PA-CD).

[0118] The ion selectivity of TFP-TA-CD membrane was tested, in which Na + The ion flux can reach 12.8 mmol h -1 m -2 , Na + / Ca 2+ The selectivity can reach 47, Li + / Mg 2+ The selectivity can reach 38, Na + / Mg 2+The selectivity can reach 32.

[0119] Example 9

[0120] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0121] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0122] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0123] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 120 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0124] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0125] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 100 V at room temperature for 5 hours to obtain a covalent organic framework composite film material (TFP-Tag-EDTA).

[0126] The ion selectivity of TFP-Tag-EDTA membrane was tested, in which Na + The ion flux can reach 17.4 mmol h -1 m -2 , Na + / Ca 2+ Selectivity can reach 150, Li + / Mg 2+ The selectivity can reach 85, Na + / Mg 2+ The selectivity can reach 132.

[0127] Example 10

[0128] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0129] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0130] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0131] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 72 hours to obtain a covalent organic framework film;

[0132] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0133] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at room temperature for 72 hours to obtain a covalent organic framework composite film material (TFP-Tag-EDTA).

[0134] The ion selectivity of TFP-Tag-EDTA membrane was tested, in which Na + The ion flux can reach 10.1 mmol h -1 m -2 , Na + / Ca 2+ Selectivity can reach 120, Li + / Mg 2+ The selectivity can reach 74, Na + / Mg 2+ The selectivity can reach 105.

[0135] Example 11

[0136] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0137] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0138] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0139] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 72 hours to obtain a covalent organic framework film;

[0140] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0141] (5) Add 10 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at room temperature for 12 hours to obtain a covalent organic framework composite film material (TFP-Tag-EDTA).

[0142] The ion selectivity of TFP-Tag-EDTA membrane was tested, in which Na + The ion flux can reach 5.1 mmol h -1 m -2 , Na + / Ca 2+ The selectivity can reach 103, Li + / Mg 2+ The selectivity can reach 68, Na + / Mg 2+ The selectivity can reach 105.

[0143] Example 12

[0144] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0145] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0146] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0147] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 72 hours to obtain a covalent organic framework film;

[0148] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0149] (5) A 4 mg / mL aqueous solution of crown ether 15C5 was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 50 V was applied at room temperature for 12 h to obtain a covalent organic framework composite film material (TFP-Tag-15C5).

[0150] The ion selectivity of TFP-Tag-15C5 membrane was tested, in which Na + The ion flux can reach 25.1 mmol h -1 m -2 , Na + / K + The selectivity can reach 30.

[0151] Example 13

[0152] The method for preparing the covalent organic framework composite membrane material with a protein-like structure in this embodiment comprises the following steps:

[0153] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0154] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0155] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 72 hours to obtain a covalent organic framework film;

[0156] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0157] (5) A 4 mg / mL aqueous solution of crown ether DB12C4 was added to both sides of the experimental device described in step (4), and a platinum sheet and ITO glass combination were used as electrodes. A voltage of 50 V was applied at room temperature for 12 h to obtain a covalent organic framework composite film material (TFP-Tag-DB12C4).

[0158] The ion selectivity of TFP-Tag-DB12C4 membrane was tested, in which Li + The ion flux can reach 20.3 mmol h - 1 m -2 , Li + / K + The selectivity can reach 10.

[0159] Comparative Example 1

[0160] The comparative example forms an unmodified covalent organic framework membrane, which specifically includes the following steps:

[0161] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0162] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0163] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0164] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0165] The ion selectivity of TFP-Tag membrane was tested, in which Na + The ion flux is 40.1 mmol h -1 m -2 , Na + / Ca 2+ Selectivity is 4, Li + / Mg 2+ The selectivity is 2.5, Na + / Mg 2+ The selectivity is 2.8.

[0166] Comparative Example 2

[0167] In this comparative example, compared with Example 1, the reaction time at 100 V for 24 h in step (3) was changed to 10 h, which specifically includes the following steps:

[0168] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0169] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0170] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 10 h to obtain a covalent organic framework film;

[0171] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0172] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at room temperature for 12 hours to obtain a covalent organic framework composite film material.

[0173] The membrane prepared in step (5) was tested for ion selectivity, wherein Na + The ion flux is 50.2 mmol h -1 m -2 , Na + / Ca 2+ The selectivity is 10, Li + / Mg 2+ The selectivity is 6, Na + / Mg 2+ The selectivity is 8.

[0174] Comparative Example 3

[0175] In this comparative example, compared with Example 1, the reaction time at 50 V in step (5) was changed from 12 h to 4 h, which specifically includes the following steps:

[0176] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0177] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0178] (3) For the above experimental device, a platinum sheet and an ITO glass were used as electrodes, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 24 hours to obtain a covalent organic framework film;

[0179] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0180] (5) Add 6 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at room temperature for 4 hours to obtain a covalent organic framework composite film material.

[0181] The membrane prepared in step (5) was tested for ion selectivity, wherein Na + The ion flux is 30.3 mmol h -1 m -2 , Na + / Ca 2+ Selectivity is 12, Li + / Mg 2+ The selectivity is 8, Na + / Mg 2+ The selectivity is 9.

[0182] Comparative Example 4

[0183] In this comparative example, the concentration of the EDTA aqueous solution in step 4 was changed to 0.2 mg / mL, which specifically included the following steps:

[0184] (1) Trimethylenediamine (25 mg) and triaminoguanidine hydrochloride (16.25 mg) were dissolved in toluene (25 mL) and 3 M acetic acid solution (25 mL) respectively by ultrasonication to obtain mutually incompatible two-phase solutions; wherein the ultrasonication time was 10 min;

[0185] (2) The polyacrylonitrile substrate is fixed on an H-type diffusion cell, and the aqueous solution and the oil phase solution are added to both sides of the device, and the organic phase is added to the front of the basement membrane;

[0186] (3) For the above experimental device, a platinum sheet and ITO glass combination was used as an electrode, and the electrodes were used as the first electrode and the second electrode, respectively, and inserted into the oil phase solution and the aqueous phase solution, and a voltage of 100 V was applied at room temperature for 12 hours to obtain a covalent organic framework film;

[0187] (4) In the above device, the residual unreacted monomers are removed by soaking and washing with excess ethanol to obtain an ionic covalent organic framework membrane (TFP-Tag).

[0188] (5) Add 0.2 mg / mL of ethylenediaminetetraacetic acid aqueous solution to both sides of the experimental device described in step (4), use a platinum sheet and ITO glass combination as electrodes, apply a voltage of 50 V at room temperature for 12 hours to obtain a covalent organic framework composite film material.

[0189] The membrane prepared in step (5) was tested for ion selectivity, wherein Na + The ion flux is 38.6 mmol h -1 m -2 , Na + / Ca 2+ Selectivity is 18, Li + / Mg 2+ The selectivity is 12, Na + / Mg 2+ The selectivity is 16.

[0190] The above embodiments are merely examples. In addition to using polyacrylonitrile substrates as porous support substrates, polyvinyl alcohol substrates (the front side is where the polyvinyl alcohol is located, and the front side is smooth), polyvinyl fluoride substrates (the front side is where the polyvinylidene fluoride is located, and the front side is smooth), polytetrafluoroethylene substrates (the front side is where the polytetrafluoroethylene is located, and the front side is smooth), and alumina substrates (the front side is a polished alumina surface, and the front side is smooth). Based on the present invention, different specific small molecules can be selected according to actual separation needs to achieve a covalent organic framework composite membrane material with a customized ion separation effect, thereby achieving a preset separation effect; that is, step (5) of each embodiment can select the small molecule used according to the target ion to be separated (similar to the conventional definition, a small molecule refers to a compound with a molecular weight of less than 500 Daltons). For example, when the target ion to be separated is a +1 valence ion, any one of p-phenylenediamine, ethylenediaminetetraacetic acid, crown ether, calixarene, and cyclodextrin can be used as a small molecule (taking crown ether as an example, different brands of crown ethers can be further selected to separate Na + , K + 、Li + target ions).

[0191] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a covalent organic framework composite membrane material, characterized in that: The following steps are involved: (1) using an organic solvent immiscible with water as a first solvent and an aqueous phase solvent as a second solvent, dissolving an aldehyde monomer in the first solvent to obtain an oil phase solution, and dissolving an amino monomer in the second solvent to obtain an aqueous phase solution; the oil phase solution and the aqueous phase solution are immiscible with each other; (2) fixing a porous support substrate on an H-type diffusion cell, and then adding the aqueous solution and the oil phase solution to both sides of the H-type diffusion cell, respectively; wherein the smooth surface of the porous support substrate is in direct contact with the oil phase solution; (3) inserting a first electrode and a second electrode into the oil phase solution and the aqueous phase solution of the H-type diffusion cell obtained in step (2), respectively, and then sealing the H-type diffusion cell and applying a voltage to perform a polymerization reaction, thereby obtaining a covalent organic framework membrane on a porous support substrate; wherein the voltage is 50-120 V and the reaction time is 12-72 h; (4) draining the aqueous phase solution and the oil phase solution in the H-type diffusion cell obtained in step (3), then adding a third solvent to both sides of the H-type diffusion cell for soaking, washing to remove residual unreacted monomers, and then draining the cell to obtain a covalent organic framework membrane; wherein the third solution is an organic solvent; (5) adding a small molecule aqueous solution capable of binding to the target ions to be separated to both sides of the H-type diffusion cell obtained in step (4), wherein the concentration of the small molecule solution is 0.5-10 mg / mL, and obtaining a covalent organic framework composite membrane material by electrochemical deposition; wherein the electrochemical deposition time is 5-72 h, and the electrochemical applied voltage is 10-100 V.

2. The preparation method according to claim 1, wherein In step (1), the aldehyde monomer is any one of trimesaldehyde, 2-hydroxy-1,3,5-benzenetricarboxaldehyde, trialdehyde phloroglucinol, tris(4-formylphenyl)amine, and 1,3,5-tris(p-formylphenyl)benzene; The amino monomer is any one of hydrated hydrazine, p-phenylenediamine, triaminoguanidine hydrochloride, 1,3,5-tris(aminomethyl)benzenetrihydrochloride, 1,3,5-triaminobenzene hydrochloride, and 1,2,4,5-benzenetetramine tetrahydrochloride; The first solvent is any one of dichloromethane, toluene, mesitylene, and ethyl acetate, or a mixed solvent of mesitylene and ethyl acetate, or a mixed solvent of toluene and ethyl acetate; The second solvent is any one of acetic acid solution, hydrochloric acid solution, trifluoroacetic acid, and p-toluenesulfonic acid solution; The ratio of the molar amount of the aldehyde monomer, the molar amount of the amino monomer and the volume of the first solvent meets the requirement of (0.1-1.0) mmol: (0.2-2.0) mmol: (20-50) mL; the volume of the first solvent is equal to the volume of the second solvent.

3. The preparation method according to claim 1, wherein In step (2), the porous supporting substrate is one of a polyacrylonitrile substrate, a polyvinyl alcohol substrate, a polyvinylidene fluoride substrate, a polytetrafluoroethylene substrate, and an alumina substrate.

4. The preparation method according to claim 1, wherein In step (1), the aldehyde monomer is dissolved in the first solvent by ultrasound; preferably, the ultrasound time is 5 to 15 minutes; The amino monomer is dissolved in the second solvent by ultrasound; preferably, the ultrasound time is 5 to 15 minutes.

5. The preparation method according to claim 1, wherein In step (4), the third solvent is any one or more of ethanol, methanol, acetone, and tetrahydrofuran.

6. The preparation method according to claim 1, wherein In step (5), the target ion to be separated is Na + , K + 、Li + , Ca 2+ Mg 2+ One ion or multiple ions with the same valence state; (I) When the cations present in the system to be separated are all +1 valence ions: i. When the target ion to be separated is Na + When the small molecule is 15-crown-5 (15C5); ii. When the target ion to be separated is K + When the small molecule is 18-crown-6 (18C6); iii. When the target ion to be separated is Li + When the small molecule is any one of 12-crown-4 (12C4) and benzo-12-crown-4 (DB12C4); (II) When the cations present in the system to be separated include both +1-valent ions and +2-valent ions, the target ions to be separated are +1-valent ions, and the small molecule is any one of p-phenylenediamine, ethylenediaminetetraacetic acid, crown ether, calixarene, and cyclodextrin.

7. The preparation method according to claim 1, wherein In step (5), the temperature of the electrochemical deposition is 20-40°C.

8. A covalent organic framework composite membrane material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the covalent organic framework composite membrane material as claimed in claim 8 as membrane separation.

10. The use according to claim 9, characterized in that The application is specifically the application of membrane separation in the ion separation process; preferably, the application is specifically the application in the separation between monovalent cations and the separation of monovalent ions and divalent ions; More preferably, the application is specifically for seawater desalination or extraction of lithium resources in salt lakes.

Images