A harsh environment resistant covalent organic framework membrane and its preparation method and application

Abstract

The application belongs to the technical field of membrane separation, and discloses a novel harsh environment resistant covalent organic framework membrane, a preparation method and application thereof, and comprises the following steps: preparing an aqueous phase and an oil phase solution for interfacial catalytic polymerization; coating the aqueous phase on a base film to perform catalyst coating; performing interfacial catalytic polymerization on the film by using the oil phase; performing heat treatment on the film after interfacial catalytic polymerization to obtain the novel harsh environment resistant covalent organic framework membrane; and applying the membrane to dye removal and dye / salt separation, especially to harsh acid / alkali / organic solvent environment. The application has the advantages that the membrane layer has good uniformity, can resist harsh acid / alkali / organic solvent environment, has excellent performance in dye separation, and has significant industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a harsh environment-resistant covalent organic framework membrane and a preparation method and application thereof. BACKGROUND

[0002] As a kind of crystalline porous material, covalent organic frameworks (COFs) have been widely applied in water treatment in recent years due to their ordered structure of monolayer, adjustable pore size, good chemical stability, high porosity and easy functionalization. The strong covalent bond makes COFs have good stability in water and organic solvents. Imine type (C=N) COFs have been widely reported in recent years due to their good water stability. Wang (Langmuir, 36 (2020) 10970-8) mixed COF monomers and catalyst in a PAN solution, and synthesized a TpEB-PAN membrane by a simple in-situ growth method, which can effectively improve the water permeability and protein barrier property of ultrafiltration membranes. Wang (J. Membr. Sci, 566 (2018) 197-204) optimized the preparation method, and synthesized a TpPa COF membrane directly on a polymer substrate by a traditional interfacial polymerization process of polyamide membranes, and studied its application in dye removal, and can resist 2 mol / L hydrochloric acid and sodium hydroxide environment.

[0003] Although traditional nanofiltration membranes such as polyelectrolyte, sulfonated polyether sulfone, polyether sulfone and polyamide are widely used in dye wastewater treatment, these nanofiltration membranes are not resistant to some harsh acid / alkali and organic solvents, which seriously affects their separation efficiency. Although conventional covalent organic framework membranes can resist some acid and alkali environments and organic solvent environments, harsh acid and alkali environments still limit their application range. Hydrazine type COFs (C=N-N) formed by hydrazine or hydrazine-containing compounds and aldehyde have enough resistance to hydrolysis, and the long pair of electrons of adjacent N atoms can be delocalized, which reduces the electrophilicity and has better chemical stability than imine type COFs. The currently reported hydrazone type COFs are mostly prepared by a solvothermal method, although they have excellent stability, the difficult-to-dissolve and difficult-to-process powders prepared by the method still limit their application.

[0004] In recent years, in-situ growth, interfacial polymerization, layer-by-layer accumulation and chemical stripping and other relatively simple synthesis strategies can effectively expand the application range. Therefore, it is necessary to use a simple method to synthesize a harsh environment-resistant hydrazone type covalent organic framework nanofiltration membrane. The conventional interfacial polymerization method for preparing COF membranes often uses acetic acid as a catalyst, which can accelerate the reaction rate and make it difficult for COFs with poor crystallinity to form a film. SUMMARY

[0005] In view of the problem that conventional nanofiltration membranes are difficult to withstand harsh environments, the application provides a method for preparing a harsh environment-resistant covalent organic framework membrane, and the harsh environment-resistant covalent organic framework membrane prepared by the method can effectively withstand environments of 9 mol / L sodium hydroxide, 2 mol / L hydrochloric acid, dioxane, acetone, methanol and ethanol, has good chemical stability, and maintains good separation performance.

[0006] The technical scheme of the application is as follows:

[0007] A method for preparing a novel harsh environment-resistant covalent organic framework membrane, comprising the following specific steps:

[0008] (1) preparing a precursor solution: preparing an aqueous solution containing a catalyst and an oil phase solution containing a reaction monomer, wherein the catalyst is p-toluenesulfonic acid, and the reaction monomer is dimethoxy terephthaldehyde and 2,4,6-trihydroxybenzene-1,3,5-trimethyl formaldehyde.

[0009] (2) coating the membrane with a catalyst: pouring the aqueous solution onto the surface of the base membrane, and removing excess water by suction filtration to obtain a primary surface treatment membrane.

[0010] (3) interfacial catalytic polymerization of the membrane: pouring the oil phase solution onto the surface of the primary surface treatment membrane, and performing interfacial catalytic polymerization to obtain a secondary surface treatment membrane.

[0011] (4) heat treatment of the membrane: placing the secondary surface treatment membrane in an oven for heat treatment to further enhance the crosslinking degree through interfacial polymerization, and obtaining a novel harsh environment-resistant covalent organic framework membrane with a uniform yellow surface.

[0012] Further, the novel harsh environment-resistant covalent organic framework membrane of step (4) needs to be soaked in deionized water for 12 h before testing.

[0013] The thickness of the covalent organic framework membrane layer is 200-400 µm.

[0014] In step (4), the heat treatment temperature is 30-80 ℃, and the heat treatment time is 10-60 min.

[0015] In step (3), the oil phase solution is poured onto the surface of the primary surface treatment membrane, and the excess oil phase solution is poured out after standing for 10-100 min. Preferably, the standing time is 20-60 min.

[0016] The aqueous solution and the oil phase solution are subjected to ultrasonic treatment for 20-30 min.

[0017] The aqueous phase solution comprises 10 mL of p-toluenesulfonic acid with a molar concentration of 0.01 mol / L to 0.10 mol / L, and the rest is deionized water. Preferably, the concentration of p-toluenesulfonic acid is 0.03 mol / L to 0.05 mol / L.

[0018] The oil phase solution comprises 10 mL of dimethoxyterephthaldehyde monomer with a molar concentration of 0.5 to 2.0 mmol / L and 0.1 to 1.0 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer, and the rest is n-hexane. Preferably, the concentration of dimethoxyterephthaldehyde monomer is 1.0 to 1.2 mmol / L and the concentration of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer is 0.7 to 0.8 mmol / L.

[0019] The bottom film needs to be soaked in deionized water for 12 hours before use.

[0020] The bottom film is a nylon film or a polyethylene film.

[0021] Based on the same inventive concept, the present application also protects a novel harsh environment resistant covalent organic framework film prepared by the novel harsh environment resistant covalent organic framework film preparation method described above, which is used for dye removal experiments of 50 ppm aqueous Congo red solution, and has a flux of 90 to 120 Lh -1 m -2 bar -1 , a Congo red rejection rate of 99% to 99.7%, and a flux of 85 to 125 h -1 m -2 bar -1 , a Congo red rejection rate of 98% to 99.5%.

[0022] The present application prepares a covalent organic framework film by an interfacial catalytic polymerization method. The catalyst p-toluenesulfonic acid forms hydrogen bonds with the COFs monomers, which can slow down the reaction rate and reduce the defects of the film. In addition, the synergistic effect of stable hydrazone bonds and irreversible beta-ketoenamine structures makes the COFs form a double stable structure, which can maintain excellent performance in harsh acid / strong base and organic solvent environments. The present application proposes a harsh environment resistant covalent organic framework film preparation method, which overcomes the difficulty of high stability covalent organic framework film formation, expands the application range of hydrazone covalent organic framework, and provides a reliable choice for dye separation nanofiltration in harsh environments.

[0023] The above technical solution has the following advantages:

[0024] This invention provides a covalent organic framework membrane resistant to harsh environments via interfacial catalytic polymerization. The process is simple, exhibits excellent separation performance and good membrane uniformity, and demonstrates superior chemical stability compared to polyamide nanofiltration membranes and covalent organic framework nanofiltration membranes in the field. It can withstand harsh environments including 9 mol / L sodium hydroxide, 2 mol / L hydrochloric acid, dioxane, acetone, methanol, and ethanol, while requiring less reagent and resulting in lower production costs. In contrast, conventional polyamide nanofiltration membranes in the field are intolerant to strong alkalis and organic solvents. Conventional covalent organic framework membranes are intolerant to 9 mol / L strong alkali environments but generally tolerate 2 mol / L acids, 2 mol / L alkalis, and organic solvents. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image (surface view) of the novel environmentally resistant covalent organic framework membrane in Example 1.

[0026] Figure 2 This is a scanning electron microscope (SEM) image (cross-sectional view) of the novel environmentally resistant covalent organic framework membrane in Example 1. Detailed Implementation

[0027] The following provides a specific implementation method for preparing a novel covalent organic framework membrane resistant to harsh environments according to the present invention.

[0028] Example 1

[0029] A novel method for preparing covalent organic framework membranes resistant to harsh environments includes the following steps:

[0030] (1) Use nylon film as the base film, soak it in deionized water for 12 hours, and then use it after drying until there are no obvious water droplets on the surface.

[0031] (2) Prepare an aqueous phase solution containing the catalyst and an oil phase solution containing the reactants. The aqueous phase solution contains 10 mL of 0.05 mol / L p-toluenesulfonic acid, and the remainder is deionized water. The oil phase solution contains 10 mL of 1.2 mmol / L dimethoxyterephthalohydrazide monomer and 0.8 mmol / L 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde monomer, and the remainder is n-hexane. Both the aqueous and oil phase solutions are subjected to ultrasonic treatment for 30 min.

[0032] (3) Pour the aqueous solution onto the surface of the bottom membrane and remove excess water by filtration to obtain a primary surface treatment membrane, and fix the membrane to a stainless steel hoop.

[0033] (4) Pour the oil phase solution onto the surface of the primary surface treatment film, let it stand for 60 minutes to carry out the interfacial catalytic polymerization reaction, remove the oil phase solution, and obtain the secondary surface treatment film.

[0034] (5) The secondary surface treatment film is placed in an oven for heat treatment, the heating temperature is 60℃, and the heating time is 30 min, so as to further interface polymerization to enhance the crosslinking degree, and a new type of harsh environment resistant covalent organic framework film with a yellow and uniform surface is obtained.

[0035] (6) The new type of harsh environment resistant covalent organic framework film prepared in step (5) is soaked in deionized water for 12 h to remove unreacted monomers, and a dye removal test is performed.

[0036] Example 2

[0037] A new type of harsh environment resistant covalent organic framework film preparation method comprises the following steps:

[0038] (1) A nylon film is used as a base film, soaked in deionized water for 12 h, and then used after being dried until no obvious water droplets are present on the surface.

[0039] (2) An aqueous solution containing a catalyst and an oil phase solution containing reaction monomers are prepared, wherein the aqueous solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.03 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxy terephthaldehyde monomer with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer, and the rest is n-hexane. The aqueous solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0040] (3) The aqueous solution is poured onto the surface of the base film, and the excess water is removed by suction filtration to obtain a primary surface treatment film, and the film is fixed on a stainless steel hoop.

[0041] (4) The oil phase solution is poured onto the surface of the primary surface treatment film, and the interface catalytic polymerization reaction is carried out after standing for 60 min, and the oil phase solution is removed to obtain a secondary surface treatment film.

[0042] (5) The secondary surface treatment film is placed in an oven for heat treatment, the heating temperature is 60℃, and the heating time is 30 min, so as to further interface polymerization to enhance the crosslinking degree, and a new type of harsh environment resistant covalent organic framework film with a yellow and uniform surface is obtained.

[0043] (6) The new type of harsh environment resistant covalent organic framework film prepared in step (5) is soaked in deionized water for 12 h to remove unreacted monomers, and a dye removal test is performed.

[0044] Example 3

[0045] A new type of harsh environment resistant covalent organic framework film preparation method comprises the following steps:

[0046] (1) take nylon film as the base film, soak in deionized water for 12 h, and use after the surface is dried without obvious water droplets;

[0047] (2) prepare a water phase solution containing a catalyst and an oil phase solution containing a reaction monomer, wherein the water phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxyterephthaldehyde monomer with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer, and the rest is n-hexane. The water phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0048] (3) pour the water phase solution on the surface of the base film, and remove the excess water by suction filtration to obtain a first surface treatment film, and fix the film on a stainless steel hoop;

[0049] (4) pour the oil phase solution on the surface of the first surface treatment film, stand for 20 min for interfacial catalytic polymerization, remove the oil phase solution, and obtain a second surface treatment film.

[0050] (5) put the second surface treatment film into an oven for heat treatment, the heating temperature is 60℃, and the heating time is 30 min, further interfacial polymerization is carried out to enhance the crosslinking degree, and a new type of harsh environment resistant covalent organic framework film with yellow and uniform surface is obtained.

[0051] (6) soak the new type of harsh environment resistant covalent organic framework film prepared in step (5) in deionized water for 12 h to remove unreacted monomers, and perform a dye removal test.

[0052] Example 4

[0053] A method for preparing a new type of harsh environment resistant covalent organic framework film, comprising the following steps:

[0054] (1) take nylon film as the base film, soak in deionized water for 12 h, and use after the surface is dried without obvious water droplets;

[0055] (2) prepare a water phase solution containing a catalyst and an oil phase solution containing a reaction monomer, wherein the water phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxyterephthaldehyde monomer with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer, and the rest is n-hexane. The water phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0056] (3) Pour the water phase solution on the surface of the bottom membrane, and remove the excess water by suction filtration to obtain a primary surface treatment membrane, and fix the membrane on a stainless steel hoop;

[0057] (4) Pour the oil phase solution on the surface of the primary surface treatment membrane, stand for 60 min for interfacial catalytic polymerization, and remove the oil phase solution to obtain a secondary surface treatment membrane.

[0058] (5) Put the secondary surface treatment membrane into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 30 min, further interfacial polymerization enhances the crosslinking degree, and a novel harsh environment resistant covalent organic framework membrane with yellow and uniform surface is obtained.

[0059] (6) Soak the novel harsh environment resistant covalent organic framework membrane prepared in step (5) in deionized water for 12 h to remove unreacted monomers, and perform a dye removal test.

[0060] Example 5

[0061] A novel harsh environment resistant covalent organic framework membrane preparation method comprises the following steps:

[0062] (1) Soak a nylon membrane as a bottom membrane in deionized water for 12 h, and use after drying until there is no obvious water droplets on the surface.

[0063] (2) Prepare a water phase solution containing a catalyst and an oil phase solution containing a reaction monomer, wherein the water phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxy terephthaldehyde monomer with a molar concentration of 1.2 mmol / L and 0.6 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer, and the rest is n-hexane. The water phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0064] (3) Pour the water phase solution on the surface of the bottom membrane, and remove the excess water by suction filtration to obtain a primary surface treatment membrane, and fix the membrane on a stainless steel hoop;

[0065] (4) Pour the oil phase solution on the surface of the primary surface treatment membrane, stand for 60 min for interfacial catalytic polymerization, and remove the oil phase solution to obtain a secondary surface treatment membrane.

[0066] (5) Put the secondary surface treatment membrane into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 30 min, further interfacial polymerization enhances the crosslinking degree, and a novel harsh environment resistant covalent organic framework membrane with yellow and uniform surface is obtained.

[0067] (6) The novel harsh environment resistant covalent organic framework membrane prepared in step (5) is soaked in deionized water for 12 h to remove unreacted monomers, and a dye removal test is performed.

[0068] Example 6

[0069] A method for preparing a novel harsh environment resistant covalent organic framework membrane, comprising the following steps:

[0070] (1) A nylon membrane is used as a base membrane, soaked in deionized water for 12 h, and then used after being dried until no obvious water droplets are present on the surface;

[0071] (2) An aqueous solution containing a catalyst and an oil phase solution containing reaction monomers are prepared, wherein the aqueous solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest of the substance is deionized water; the oil phase solution contains 10 mL of dimethoxy terephthaldehyde monomers with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomers, and the rest of the substance is n-hexane. The aqueous solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0072] (3) The aqueous solution is poured onto the surface of the base membrane, and the excess water is removed by suction filtration to obtain a first surface treatment membrane, and the membrane is fixed on a stainless steel hoop;

[0073] (4) The oil phase solution is poured onto the surface of the first surface treatment membrane, and an interfacial catalytic polymerization reaction is carried out after standing for 60 min. The oil phase solution is removed to obtain a second surface treatment membrane.

[0074] (5) The second surface treatment membrane is placed in an oven for heat treatment at a heating temperature of 60°C for 30 min to further enhance the cross-linking degree through interfacial polymerization, and a novel harsh environment resistant covalent organic framework membrane with a yellow and uniform surface is obtained.

[0075] (6) The novel harsh environment resistant covalent organic framework membrane prepared in step (5) is soaked in a 9 mol / L sodium hydroxide solution for 5 d, washed with deionized water, and then subjected to a dye removal test.

[0076] Example 7

[0077] A method for preparing a novel harsh environment resistant covalent organic framework membrane, comprising the following steps:

[0078] (1) A nylon membrane is used as a base membrane, soaked in deionized water for 12 h, and then used after being dried until no obvious water droplets are present on the surface;

[0079] (2) Preparation of the aqueous phase solution containing the catalyst and the oil phase solution containing the reaction monomers, wherein the aqueous phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxyterephthaldehyde monomers with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomers, and the rest is n-hexane. The aqueous phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0080] (3) Pouring the aqueous phase solution on the surface of the base film, and removing the excess water by suction filtration to obtain a primary surface treatment film, and fixing the film on a stainless steel hoop;

[0081] (4) Pouring the oil phase solution on the surface of the primary surface treatment film, standing for 60 min for interfacial catalytic polymerization, and removing the oil phase solution to obtain a secondary surface treatment film.

[0082] (5) Placing the secondary surface treatment film into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 30 min, further interfacial polymerization is carried out to enhance the crosslinking degree, and a novel harsh environment resistant covalent organic framework film with a yellow uniform surface is obtained.

[0083] (6) Soaking the novel harsh environment resistant covalent organic framework film prepared in step (5) in a 2 mol / L hydrochloric acid solution for 5 d, washing with deionized water, and then performing dye removal test.

[0084] Example 8

[0085] A novel harsh environment resistant covalent organic framework film preparation method, comprising the following steps:

[0086] (1) Using a nylon film as a base film, soaking in deionized water for 12 h, and then using after the surface is dried without obvious water droplets;

[0087] (2) Preparation of the aqueous phase solution containing the catalyst and the oil phase solution containing the reaction monomers, wherein the aqueous phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxyterephthaldehyde monomers with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomers, and the rest is n-hexane. The aqueous phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0088] (3) Pouring the aqueous phase solution on the surface of the base film, and removing the excess water by suction filtration to obtain a primary surface treatment film, and fixing the film on a stainless steel hoop;

[0089] (4) Pouring the oil phase solution on the surface of the primary surface treatment film, standing for 60 min for interfacial catalytic polymerization, removing the oil phase solution, to obtain a secondary surface treatment film.

[0090] (5) Placing the secondary surface treatment film into an oven for heat treatment, heating temperature is 60℃, heating time is 30 min, further interfacial polymerization to enhance the crosslinking degree, to obtain a new type of harsh environment resistant covalent organic framework film with yellow and uniform surface.

[0091] (6) Soaking the new type of harsh environment resistant covalent organic framework film prepared in step (5) in acetone for 5 d, rinsing with ethanol, and then performing dye removal test.

[0092] Example 9

[0093] A method for preparing a new type of harsh environment resistant covalent organic framework film, comprising the following steps:

[0094] (1) Soaking a nylon film as a base film in deionized water for 12 h, and then using it after drying until no obvious water droplets are present on the surface.

[0095] (2) Preparing a water phase solution containing a catalyst and an oil phase solution containing a reaction monomer, wherein the water phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil phase solution contains 10 mL of dimethoxy terephthaldehyde monomer with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomer, and the rest is n-hexane. The water phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0096] (3) Pouring the water phase solution on the surface of the base film, and removing excess water by suction filtration to obtain a primary surface treatment film, and fixing the film on a stainless steel hoop.

[0097] (4) Pouring the oil phase solution on the surface of the primary surface treatment film, standing for 60 min for interfacial catalytic polymerization, removing the oil phase solution, to obtain a secondary surface treatment film.

[0098] (5) Placing the secondary surface treatment film into an oven for heat treatment, heating temperature is 60℃, heating time is 30 min, further interfacial polymerization to enhance the crosslinking degree, to obtain a new type of harsh environment resistant covalent organic framework film with yellow and uniform surface.

[0099] (6) Soaking the new type of harsh environment resistant covalent organic framework film prepared in step (5) in acetone for 5 d, rinsing with ethanol, and then performing dye removal test.

[0100] Example 10

[0101] A method for preparing a novel harsh environment-resistant covalent organic framework membrane, comprising the following steps:

[0102] (1) Using a nylon membrane as a base membrane, soaking it in deionized water for 12 hours, and then using it after the surface is dried and no obvious water droplets are present;

[0103] (2) Preparing a water-phase solution containing a catalyst and an oil-phase solution containing reaction monomers, wherein the water-phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil-phase solution contains 10 mL of dimethoxyterephthaldehyde monomers with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomers, and the rest is n-hexane. The water-phase solution and the oil-phase solution are subjected to ultrasonic treatment for 30 min.

[0104] (3) Pouring the water-phase solution onto the surface of the base membrane, and removing excess water by suction filtration to obtain a first surface treatment membrane, and fixing the membrane on a stainless steel hoop;

[0105] (4) Pouring the oil-phase solution onto the surface of the first surface treatment membrane, and standing for 60 min for interfacial catalytic polymerization, and removing the oil-phase solution to obtain a second surface treatment membrane.

[0106] (5) Placing the second surface treatment membrane into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 30 min, further interfacial polymerization is performed to enhance the crosslinking degree, and a novel harsh environment-resistant covalent organic framework membrane with a yellow and uniform surface is obtained.

[0107] (6) Soaking the novel harsh environment-resistant covalent organic framework membrane prepared in step (5) in methanol for 5 days, washing it with ethanol, and then performing dye removal testing.

[0108] Example 11

[0109] A method for preparing a novel harsh environment-resistant covalent organic framework membrane, comprising the following steps:

[0110] (1) Using a nylon membrane as a base membrane, soaking it in deionized water for 12 hours, and then using it after the surface is dried and no obvious water droplets are present;

[0111] (2) Preparing a water-phase solution containing a catalyst and an oil-phase solution containing reaction monomers, wherein the water-phase solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L, and the rest is deionized water; the oil-phase solution contains 10 mL of dimethoxyterephthaldehyde monomers with a molar concentration of 1.2 mmol / L and 0.8 mmol / L of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde monomers, and the rest is n-hexane. The water-phase solution and the oil-phase solution are subjected to ultrasonic treatment for 30 min.

[0112] (3) Pour the water phase solution on the surface of the base film, and remove the excess water by suction filtration to obtain a primary surface treatment film, and fix the film on a stainless steel hoop;

[0113] (4) Pour the oil phase solution on the surface of the primary surface treatment film, and stand for 60 min for interfacial catalytic polymerization, and remove the oil phase solution to obtain a secondary surface treatment film.

[0114] (5) Put the secondary surface treatment film into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 30 min, further interfacial polymerization is carried out to enhance the crosslinking degree, and a novel harsh environment resistant covalent organic framework film with yellow and uniform surface is obtained.

[0115] (6) Soak the novel harsh environment resistant covalent organic framework film prepared in step (5) in ethanol for 5 d, and perform dye removal test.

[0116] The novel harsh environment resistant covalent organic framework films prepared in Examples 1-11 are subjected to dye removal performance test, and the performance indexes are as shown in Table 1. Figure 1

[0117] Comparative Example 1

[0118] A polyamide nanofiltration membrane preparation method, the main difference from Example 6 is that the water phase solution is piperazine solution, and the oil phase solution is trimesoyl chloride solution, and no catalyst is needed, and the method specifically comprises the following steps:

[0119] (1) A nylon film is used as a base film, which is soaked in deionized water for 12 h, and then used after being dried until no obvious water droplets are present on the surface.

[0120] (2) Prepare a water phase solution and an oil phase solution, wherein the water phase solution comprises 10 mL of anhydrous piperazine with a molar concentration of 70 mmol / L, and the rest is deionized water; the oil phase solution comprises 10 mL of trimesoyl chloride with a molar concentration of 0.8 mmol / L, and the rest is n-hexane. The water phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0121] (3) Pour the water phase solution on the surface of the base film, and remove the excess water by suction filtration to obtain a primary surface treatment film, and fix the film on a stainless steel hoop;

[0122] (4) Pour the oil phase solution on the surface of the primary surface treatment film, and stand for 5 s for interfacial polymerization, and remove the oil phase solution to obtain a secondary surface treatment film.

[0123] ​(5) The secondary surface treatment film is placed into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 1 min, to further interface polymerization to enhance the cross-linking degree, to obtain a polyamide nanofiltration membrane.

[0124] (6) The harsh environment resistant covalent organic framework film prepared in step (5) is soaked in a 2 mol / L sodium hydroxide solution for 1 d for dye removal test.

[0125] Comparative Example 2

[0126] A covalent organic framework film preparation method, which mainly differs from Example 6 in that the aqueous solution is an acetic acid and p-phenylenediamine (Pa) solution, and the oil phase solution is a 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde (Tp) solution, and specifically comprises the following steps:

[0127] (1) The nylon film is used as a base film, soaked in deionized water for 12 h, and then used after being dried until no obvious water droplets are present on the surface.

[0128] (2) The aqueous solution and the oil phase solution are prepared, wherein the aqueous solution contains 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L and 20 mmol / L of p-phenylenediamine, and the rest of the substances are deionized water; the oil phase solution contains 10 mL of triformylphloroglucinol with a molar concentration of 0.8 mmol / L, and the rest of the substances are n-hexane. The aqueous solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0129] (3) The aqueous solution is poured onto the surface of the base film, and the excess water is removed by suction filtration to obtain a primary surface treatment film, and the film is fixed on a stainless steel hoop.

[0130] (4) The oil phase solution is poured onto the surface of the primary surface treatment film, and the interface polymerization reaction is allowed to proceed for 10 min, and then the oil phase solution is removed to obtain a secondary surface treatment film.

[0131] (5) The secondary surface treatment film is placed into an oven for heat treatment, the heating temperature is 60°C, and the heating time is 3 min, to further interface polymerization to enhance the cross-linking degree, to obtain an orange-yellow TpPa covalent organic framework nanofiltration membrane.

[0132] (6) The harsh environment resistant covalent organic framework film prepared in step (5) is soaked in a 2 mol / L sodium hydroxide solution for 5 d for dye removal test.

[0133] Comparative Example 3

[0134] A covalent organic framework film preparation method, which mainly differs from Example 6 in that the aqueous solution is an acetic acid and p-phenylenediamine (Pa) solution, and the oil phase solution is a 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde (Tp) solution, and specifically comprises the following steps:

[0135] (1) The nylon film is used as the base film, soaked in deionized water for 12 h, and then used after being dried until no obvious water droplets are present on the surface;

[0136] (2) The aqueous phase solution and the oil phase solution are prepared, wherein the aqueous phase solution comprises 10 mL of p-toluenesulfonic acid with a molar concentration of 0.05 mol / L and 20 mmol / L of p-phenylenediamine, and the rest is deionized water; the oil phase solution comprises 10 mL of triformylchloride with a molar concentration of 0.8 mmol / L, and the rest is n-hexane. The aqueous phase solution and the oil phase solution are subjected to ultrasonic treatment for 30 min.

[0137] (3) The aqueous phase solution is poured onto the surface of the base film, and the excess water is removed by suction filtration to obtain a first surface treatment film, and the film is fixed on a stainless steel hoop;

[0138] (4) The oil phase solution is poured onto the surface of the first surface treatment film, and the interface polymerization reaction is allowed to proceed for 10 min, and then the oil phase solution is removed to obtain a second surface treatment film.

[0139] (5) The second surface treatment film is placed in an oven for heat treatment, the heating temperature is 60°C, and the heating time is 3 min, further interface polymerization is performed to enhance the crosslinking degree, and an orange-yellow TpPa covalent organic framework nanofiltration membrane is obtained.

[0140] (6) The harsh environment-resistant covalent organic framework membrane prepared in step (5) is soaked in a 5 mol / L sodium hydroxide solution for 5 d for dye removal test.

[0141] Table 1, harsh environment-resistant covalent organic framework membranes prepared in Examples 1-11

[0142]

[0143] Table 2, performance indicators of conventional nanofiltration membranes prepared in Comparative Examples 1-2, (soaking environment 2 mol / L and 5 mol / L sodium hydroxide, not resistant to 9 mol / L strong alkali environment, the membrane is directly damaged with 9 mol / L.)

[0144]

[0145] The above only describes the preferred embodiments of the present application, but not a limitation thereof, it should be noted that those skilled in the art can make modifications to the foregoing embodiments without departing from the concept of the present application, and these improvements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing a harsh environment resistant covalent organic framework membrane, characterized in that, The method comprises the following steps: (1) preparing a precursor solution: preparing a water phase solution containing a catalyst and an oil phase solution containing a reaction monomer, wherein the catalyst is p-toluenesulfonic acid, and the reaction monomer is dimethoxyterephthalic dihydrazide and 2,4,6-trihydroxybenzene-1,3,5-trimethyl formaldehyde; (2) coating the film with the catalyst: pouring the water phase solution on the surface of the base film, and removing the excess water by suction filtration to obtain a primary surface treatment film; (3) interfacial catalytic polymerization of the film: pouring the oil phase solution on the surface of the primary surface treatment film, and performing interfacial catalytic polymerization to obtain a secondary surface treatment film; (4) heat treatment of the film: placing the secondary surface treatment film in an oven for heat treatment to further enhance the crosslinking degree by interfacial polymerization, thereby obtaining a surface yellow uniform harsh environment resistant covalent organic framework film.

2. The method of claim 1, wherein the method is performed in a harsh environment. The harsh environment resistant covalent organic framework film of step (4) needs to be soaked in deionized water for 12 hours before testing.

3. The method of claim 1, wherein the method is performed in a harsh environment. The thickness of the covalent organic framework film layer is 100-300 nm.

4. The method of claim 1, wherein the method is performed in a harsh environment. In step (4), the heat treatment temperature is 30 to 80 O C, and the heat treatment time is 10 to 60 min.

5. The method of claim 1, wherein: In step (3), the oil phase solution is poured on the surface of the primary surface treatment film, and the excess oil phase solution is poured out after standing for 10-100 min.

6. The method of claim 1, wherein: The water phase solution contains 10 mL of p-toluenesulfonic acid with a substance concentration of 0.01-0.10 mol / L, and the rest is deionized water.

7. The method of claim 1, wherein the method is performed in a harsh environment. The oil phase solution contains 10 mL of dimethoxyterephthalic dihydrazide monomer with a substance concentration of 0.5-2.0 mmol / L and 0.1-1.0 mol / L of 2,4,6-trihydroxybenzene-1,3,5-trimethyl formaldehyde monomer, and the rest is n-hexane.

8. A harsh environment resistant covalent organic framework film prepared by the method of any one of claims 1-7.

9. The harsh environment resistant covalent organic framework film of claim 8, wherein: The harsh environment resistant covalent organic framework membrane is used for dye removal experiment of 50ppm Congo red aqueous solution, and the flux thereof is 90-120L h under the condition that the test pressure is 0.1MPa -1 m -2 bar -1 The Congo red rejection rate is 99%-99.7%; when the membrane is soaked in 9mol / L sodium hydroxide, 2mol / L hydrochloric acid, dioxane, acetone, methanol and ethanol respectively for 5 days, the flux thereof is 85-125h - 1 m -2 bar -1 The Congo red rejection rate is 98%-99.5%.

10. The harsh environment resistant covalent organic framework film of claim 8 for use in the field of dye removal.

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