Preparation method of COFs / PAN oil-water separation microporous membrane with underwater superamphiphobicity

Abstract

The present invention discloses a method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity, comprising the following steps: 1) preparing a suspension of COFs nanospheres and a hydrophilic PAN-based microporous membrane; 2) preparing the COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity. In the present invention, the combination of the hydrophilic PAN-based microporous membrane and the hydrophobic COFs nanospheres imparts intermediate wetting ability to the membrane, and the loading of the COFs nanospheres increases the roughness and micro / nanostructure of the COFs / PAN oil-water separation microporous membrane, which can enhance the capillary effect of the membrane surface. Simultaneously, when water or oil is pre-wetted, the water or oil molecules can be trapped in the pores of the COFs or adsorbed on the surface of the COFs. Therefore, the combined action of the loading of the COFs nanospheres and the PAN-based microporous membrane imparts underwater super-amphiphobicity to the COFs / PAN oil-water separation microporous membrane.

Description

Technical Field

[0001] The invention belongs to the technical field of oil-water separation membranes, and in particular is a method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity. Background Art

[0002] Developing cost-effective strategies for treating oily wastewater and rationally recycling it is not only beneficial to economic and social development, but also to the environment and human health. Membrane separation technology has attracted increasing attention due to its environmental friendliness, high efficiency, environmental friendliness, ease of operation, and ability to effectively treat wastewater containing surfactants and emulsified oils.

[0003] The document with application number 202111310919.7 discloses a full-cellulose composite membrane for oil-water separation and its preparation method and application, which is composited by fusing regenerated cellulose with a porous reinforced cellulose substrate to construct a full-cellulose network. The composite membrane has hydrophilic-underwater superoleophobic wetting properties, which can achieve separation of oil-water mixture and oil-in-water emulsion. The document with application number 202111509211.4 discloses a preparation method and application of a hydrogel / polyvinylidene fluoride (PVDF) composite oil-water separation membrane, which first grafts methacrylic acid glycidyl ether onto an alkalized PVDF membrane, and then applies a gel prepolymer consisting of aminated sodium lignin sulfonate, hyperbranched polyamide, and a cross-linking agent polyethylene glycol diglycidyl ether to the grafted PVDF membrane. After heating and cross-linking, a hydrogel / PVDF composite membrane is formed, and the hydrogel layer has excellent super-hydrophilic-underwater super-oleophobicity, which can be used for the separation of oil-in-water emulsions. The single wettability of these oil-water separation membranes limits their ability to separate only a single type of oil-water emulsion, severely restricting their application in treating diverse oily wastewaters, increasing separation costs and complicating the process. To expand the scope of their application, membranes with switchable surface wettability are urgently needed.

[0004] Document No. 201911177599.5 self-assembles and deposits multilayer cobalt hydroxide nanosheets on the surface of a stainless steel mesh using electrodeposition technology to obtain an emulsion separation membrane with superhydrophilic / underwater superoleophobic properties, which can be used to separate oil-in-water emulsions. Subsequently, through fluorosilane surface modification, it can be intelligently converted into a superhydrophobic / underwater superoleophilic membrane to achieve the separation of oil-in-water emulsions. However, its surface wettability change is irreversible. On-demand separation of oil-water separation membranes with switchable surface wettability requires complex external stimuli, such as changes in process and transmembrane direction, which seriously restricts the large-scale application of oil-water separation membranes with switchable surface wettability. Therefore, there is an urgent need to develop an oil-water separation membrane material with simple process, high separation efficiency, and rapid switching of surface wettability. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide a method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super amphiphobicity.

[0006] The technical solution of the present invention to solve the technical problem is to provide a method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity, characterized in that the method comprises the following steps:

[0007] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0008] Preparation of COFs nanosphere suspension: adding amino monomer and aldehyde monomer to a composite solvent and dissolving them to form a homogeneous solution; then adding a catalyst and allowing the COFs nanospheres to fully grow to obtain a uniformly dispersed COFs nanosphere suspension;

[0009] Preparation of a hydrophilic PAN-based microporous membrane: First, a meltable PAN terpolymer is prepared by emulsion polymerization; then, the meltable PAN terpolymer is mixed with a composite diluent, and then heated to completely dissolve the meltable PAN terpolymer. After degassing, a casting solution is obtained; the casting solution is then rolled into a shape, and then cured and formed, and the composite diluent is removed to obtain a hydrophilic PAN-based microporous membrane;

[0010] 2) Preparation of a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A hydrophilic PAN-based microporous membrane was immersed in a suspension of COFs nanospheres, causing π-π stacking of the benzene rings in the PAN-based microporous membrane with those in the COFs nanospheres. After removal, the membrane was washed with detergent to remove the residual COFs nanosphere suspension on the surface, and then dried to remove the residual detergent, resulting in a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The present invention directly prepares uniform, crystalline COF nanospheres with a size between 40 and 400 nm in solution, and the size of the COF nanospheres can be controlled by catalyst concentration, reaction temperature, and reaction time. Compared with COFs prepared by solvothermal methods, the reaction conditions are milder and the reaction process is more rapid. Moreover, the prepared COF nanosphere suspension can be directly used in subsequent experiments, avoiding the disadvantage of COF microcrystalline powder prepared by conventional methods, which is difficult to directly process and utilize.

[0013] (2) The meltable PAN terpolymer prepared by the emulsion polymerization method of the present invention has a mass average molecular weight of 40,000 to 100,000 and a melt index of 2 to 20 g / 10 min. The meltable PAN terpolymer can be used to prepare a PAN-based microporous membrane through the TIPS method. The PAN-based microporous membrane exhibits a bicontinuous network structure, has high porosity, uniform pore size distribution, excellent mechanical properties, and good permeability. Compared with conventional PAN membranes, the hydrophilic properties of the PAN-based microporous membrane are more excellent and can reach super hydrophilicity. The TIPS method can greatly reduce the use of solvents, making the preparation process more environmentally friendly, highly efficient, and easy to scale up.

[0014] (3) The COFs nanospheres prepared by the present invention have higher hydrophobicity than COFs prepared by conventional methods, and the COFs nanospheres are bound to the hydrophilic PAN-based microporous membrane through π-π conjugation. The interaction between the COFs nanospheres and the PAN-based microporous membrane can prevent the COFs nanospheres from falling off during the application process.

[0015] (4) The combination of the hydrophilic PAN-based microporous membrane and the hydrophobic COFs nanospheres in the present invention gives the membrane intermediate wetting ability, and the loading of COFs nanospheres increases the roughness and micro / nanostructure of the COFs / PAN oil-water separation microporous membrane, which can lead to an enhanced capillary effect on the membrane surface. At the same time, when water or oil is pre-wetted, water or oil molecules can be trapped in the pores of COFs or adsorbed on the surface of COFs. Therefore, the combined effect of the loading of COFs nanospheres and the PAN-based microporous membrane gives the COFs / PAN oil-water separation microporous membrane underwater superamphiphobicity.

[0016] (5) The COFs / PAN oil-water separation microporous membrane prepared in the present invention only needs to be pre-wetted with water or oil to form a hydration layer or an oil-hydration layer on the membrane surface, which can quickly switch the surface wettability and prevent the invasion of oil and water droplets, so that the microporous membrane has the characteristics of underwater superoleophobicity or oil-under-water superhydrophobicity, thereby realizing efficient separation of water-in-oil or oil-in-water emulsions.

[0017] (6) The preparation process of the present invention is simple and the process is controllable. The prepared COFs / PAN oil-water separation microporous membrane has good separation performance for different types of emulsions, has potential application prospects in the field of oil-water separation, and can be suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an SEM image of COFs nanospheres prepared in Example 1 of the present invention;

[0019] Figure 2 This is the XRD curve of COFs nanospheres prepared in Example 1 of the present invention;

[0020] Figure 3 FT-IR curve of COFs nanospheres prepared in Example 1 of the present invention;

[0021] Figure 4 This is an SEM image of the COFs / PAN oil-water separation microporous membrane prepared in Example 1 of the present invention;

[0022] Figure 5 This is an SEM image of the PAN-based microporous membrane prepared in Comparative Example 1 of the present invention;

[0023] Figure 6 This is an SEM image of the COFs / PAN oil-water separation microporous membrane prepared in Comparative Example 2 of the present invention;

[0024] Figure 7 The submerged contact angle of the COFs / PAN oil-water separation microporous membrane prepared in Example 1 of the present invention;

[0025] Figure 8 The submerged contact angle of the PAN-based microporous membrane prepared in Comparative Example 1 of the present invention;

[0026] Figure 9 The separation performance of the COFs / PAN oil-water separation microporous membrane prepared in Example 1 of the present invention for oil-in-water emulsion;

[0027] Figure 10 The separation performance of the COFs / PAN oil-water separation microporous membrane prepared in Example 1 of the present invention for oil-in-water emulsion;

[0028] Figure 11 These are optical photographs of the emulsions before and after separation of oil-in-water and water-in-oil emulsions by the COFs / PAN oil-water separation microporous membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention and do not limit the scope of protection of the claims of the present invention.

[0030] The present invention provides a method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0031] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0032] Preparation of COFs nanosphere suspension: amino monomer and aldehyde monomer are added to a composite solvent and dissolved by ultrasonication to form a homogeneous solution; a catalyst is then added and the solution is allowed to stand to allow the COFs nanospheres to fully grow, thereby obtaining a uniformly dispersed COFs nanosphere suspension;

[0033] Preparation of a hydrophilic PAN-based microporous membrane: First, a meltable PAN terpolymer is prepared by emulsion polymerization; then, the meltable PAN terpolymer is mixed with a composite diluent, and then heated to completely dissolve the meltable PAN terpolymer. After degassing, a casting solution is obtained; the casting solution is then poured into a preheated mold for calendering, and then cured at room temperature. The composite diluent is then removed to obtain a hydrophilic PAN-based microporous membrane (hereinafter referred to as a PAN-based microporous membrane);

[0034] Preferably, in step 1), the amino monomer is 1,3,5-tris(4-aminophenyl)benzene, p-phenylenediamine or benzidine (preferably 1,3,5-tris(4-aminophenyl)benzene); the aldehyde monomer is terephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 1,3,5-triformylphloroglucinol or benzene-1,3,5-tricarbaldehyde (preferably terephthalaldehyde, 2,5-dihydroxyterephthalaldehyde or 2,5-dimethoxyterephthalaldehyde).

[0035] Preferably, in step 1), the composite solvent consists of a main solvent and a co-solvent, the main solvent accounts for 50-100% of the volume of the composite solvent; the main solvent is water, ethanol, acetonitrile, dichloromethane, dioxane or mesitylene (preferably dichloromethane or acetonitrile); the co-solvent is acetonitrile, methyl acetate, ethyl acetate, n-butanol or ethanol (preferably ethanol).

[0036] Preferably, in step 1), the catalyst is glacial acetic acid, trifluoroacetic acid, scandium trifluoromethanesulfonate, p-toluenesulfonic acid or a transition metal nitrate (preferably glacial acetic acid or trifluoroacetic acid); the transition metal nitrate is iron nitrate, zinc nitrate, nickel nitrate, cobalt nitrate, manganese nitrate or copper nitrate.

[0037] Preferably, in step 1), the molar ratio of the amino group in the amino monomer: the aldehyde group in the aldehyde monomer is 1:1; the concentrations of the amino monomer and the aldehyde monomer are both 0.1 to 5 mmol / L (preferably 0.1 to 3 mmol / L); and the concentration of the catalyst is 0.01 to 2 mmol / L (preferably 0.01 to 1 mmol / L).

[0038] Preferably, in step 1), the standing temperature is 10 to 60° C., and the standing time is 12 to 72 hours.

[0039] Preferably, in step 1), the particle size of the COFs nanospheres ranges from 40 to 400 nm.

[0040] Preferably, in step 1), the meltable PAN terpolymer component is: 80-90 mol% of the first reactive monomer, 5-20 mol% of the second reactive monomer and 0.5-2 mol% of the third reactive monomer; the first reactive monomer is acrylonitrile, the second reactive monomer is methyl acrylate, acrylic acid or vinyl imidazole, and the third reactive monomer is 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone or stearyl benzophenone. Preferably, the first reactive monomer is acrylonitrile (AN), the second reactive monomer is methyl acrylate (MA), and the third reactive monomer is 4-acryloyloxybenzophenone (ABP). The molar ratio of AN:MA:ABP is 85:14:1, and the obtained meltable PAN terpolymer is poly(acrylonitrile-methyl acrylate-4-acryloyloxybenzophenone) (P(AN-MA-ABP)).

[0041] Preferably, in step 1), the specific process for preparing the meltable PAN terpolymer by emulsion polymerization is as follows: 100-300 mL of deionized water, 1-8 g of emulsifier, and 1-5 mL of chain transfer agent are added to a reaction vessel (preferably a three-necked flask), then nitrogen is passed through for 0.5-2 h, 10-50 mL of a mixed solution of three reaction monomers is added, and after heating to 40-80° C., 20-40 mL of an initiator solution is added. After starting the reaction, 30-90 mL of the mixed solution of the three reaction monomers is added dropwise to the reaction vessel. After reacting for 2-4 h, 30-80 mL of the initiator solution is added and the reaction is continued for 0.5-2 h. Finally, the reaction solution is poured into a 10-100 g / L magnesium sulfate solution for demulsification, allowed to stand, filtered, and dried to obtain the meltable PAN terpolymer.

[0042] The emulsifier is OP-10 and / or sodium lauryl sulfate; the chain transfer agent is dodecyl mercaptan; and the initiator solution is 1-5 g / L sodium persulfate solution, potassium persulfate solution or ammonium persulfate solution.

[0043] Preferably, in step 1), the composite diluent is composed of a main diluent and a secondary diluent, the main diluent accounts for 50-100% of the mass of the composite diluent; the main diluent is caprolactam, ethylene carbonate, diphenyl sulfone, diphenyl carbonate, dimethyl sulfoxide, cyclohexyl pyrrolidone or diphenyl ethyl ketone; the secondary diluent is polyvinyl alcohol, polyethylene glycol, glycerol, triacetin, polyethylene glycol monomethyl ether, dibutyl sebacate, dimethyl phthalate or acetamide.

[0044] Preferably, in step 1), the meltable PAN terpolymer accounts for 15 to 35% of the mass of the composite diluent.

[0045] Preferably, in step 1), the oxygen-free environment is preferably an inert gas environment, more preferably a nitrogen environment.

[0046] Preferably, in step 1), the method for removing the composite diluent is soaking in deionized water.

[0047] Preferably, in step 1), the heating reaction is carried out at 130-190° C. in an oxygen-free environment for 1-4 hours.

[0048] 2) Preparation of a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A hydrophilic PAN-based microporous membrane is immersed in a suspension of COFs nanospheres, so that the benzene rings in the PAN-based microporous membrane and the benzene rings of the COFs nanospheres undergo π-π stacking, resulting in interaction between the COFs nanospheres and the PAN-based microporous membrane, thereby preventing the COFs nanospheres from falling off during application; after being removed, the membrane is washed with detergent to remove the residual COFs nanosphere suspension on the surface, and then dried to remove the residual detergent, thereby obtaining a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity (referred to as COFs / PAN oil-water separation microporous membrane).

[0049] Preferably, in step 2), the immersion temperature is 10-60° C., and the immersion time is 0.5-12 h (preferably 1-5 h).

[0050] Preferably, in step 2), the method for removing the COFs nanosphere suspension remaining on the surface is to first wash with ethanol and then wash with deionized water.

[0051] The test method in the embodiment is:

[0052] Underwater superamphiphobicity test: Immerse the prepared sample in oil or water. After it is completely wetted, drop a 2μL droplet (water droplet or oil droplet) on the membrane surface. When the droplet stabilizes, record the contact angle at this time, which is the underwater water contact angle under oil and the underwater oil contact angle under water.

[0053] Oil-water separation performance test:

[0054] At 0.04 MPa, the oil-water emulsion separation experiment was carried out by terminal filtration. The flux and efficiency of oil-water separation were calculated using Formula 1 and Formula 2:

[0055]

[0056] Separation efficiency=(1-c / c0)×100% (2)

[0058] In formulas (1) and (2), J w , V, A, t, ΔP, c0 and c are the flux of the membrane (L / m 2 ·h·bar), volume of filtrate (L), effective membrane area (m 2), run time (h), transmembrane pressure (bar), the content of the dispersed phase in the emulsion, and the content of the dispersed phase in the corresponding filtrate. For water-in-oil and oil-in-water emulsions, the water content and oil content in the emulsions were measured using a Karl Fischer titrator and a total organic carbon analyzer (Shimadzu TOC-L CPN), respectively.

[0059] Example 1

[0060] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0061] Preparation of COFs nanosphere suspension: 2 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 3 mmol / L 2,5-dimethoxyterephthalaldehyde were added to a mixed solvent consisting of 500 mL of dichloromethane and 400 mL of ethanol. After ultrasonic dissolution, 0.05 mmol / L trifluoroacetic acid was added, and the mixture was allowed to stand at 20°C for 48 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0062] Preparation of a hydrophilic PAN-based microporous membrane: 8 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (35 g of caprolactam and 5 g of glycerol), heated to 180°C under nitrogen, reacted for 2 h, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0063] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 20°C for 4 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0064] Depend on Figure 1 It can be seen that the COFs nanospheres of Example 1 exhibit a uniform spherical structure with a size range of 50 to 70 nm.

[0065] Depend on Figure 2 It can be seen that the characteristic diffraction peaks at 2.7°, 4.8°, 5.6°, 7.4°, 9.7° and 25.2° correspond to the (100), (110), (200), (210), (220) and (001) crystal planes of COFs nanospheres, respectively. Figure 3 It can be seen that at 1612cm -1 An obvious COFs stretching vibration peak (C=N) appears at . Figure 2 and Figure 3 This demonstrates the successful synthesis of COFs.

[0066] Depend on Figure 4 It can be seen that the surface of the COFs / PAN oil-water separation microporous membrane is evenly covered with COFs nanospheres, compared with the PAN-based microporous membrane of Comparative Example 1 ( Figure 5 ), demonstrating the successful preparation of COFs / PAN microporous membrane for oil-water separation.

[0067] Depend on Figure 7 It can be seen that the underwater oil contact angle of the COFs / PAN oil-water separation microporous membrane is 153.2°, and the underwater water contact angle of the oil is 163.0°. Therefore, the COFs / PAN oil-water separation microporous membrane has underwater superamphiphobicity.

[0068] Depend on Figure 9 and Figure 10 It can be seen that the separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifier are 5746L / m -2 h bar, 98.6% and 8133L / m -2 h bar, more than 98.0%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1200L / m -2 h bar, 98.2% and 2100L / m -2 ·h·bar, more than 97.4%.

[0069] Depend on Figure 11 It can be seen that no droplets were found in the filtrate after separation, indicating its excellent separation performance.

[0070] Comparative Example 1

[0071] Only the preparation steps of the hydrophilic PAN-based microporous membrane in Example 1 were used to prepare the hydrophilic PAN-based microporous membrane, specifically: 8 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (including 35 g of caprolactam and 5 g of propylene glycol), heated to 180°C under nitrogen protection, reacted for 2 hours, and degassed to obtain a casting liquid; the casting liquid was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent to obtain a hydrophilic PAN-based microporous membrane.

[0072] After testing, Figure 5 It can be seen that Comparative Example 1 presents a typical bicontinuous network structure. The hydrophilic PAN-based microporous membrane of Comparative Example 1 has an underwater oil contact angle of 82.6° and an underwater water contact angle of 98.2°. Therefore, the PAN-based microporous membrane does not have underwater superamphiphobicity. Figure 8 As shown. For the separation flux and separation efficiency of water-in-oil and oil-in-water emulsions without emulsifier, they are 3412L / m -2h bar, 42.1% and 3514 L / m -2 h·bar, 43.1% or more, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 814L / m -2 h bar, 25.4% and 1049 L / m -2 h·bar, 21.5% or more. Therefore, PAN-based microporous membranes do not have the ability to separate oil and water.

[0073] Comparative Example 2

[0074] Comparative Example 2 is exactly the same as step 1) of Example 1, and the only difference from step 2) of Example 1 is that the immersion time is 13 hours. Specifically:

[0075] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0076] Preparation of COFs nanosphere suspension: 2 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 3 mmol / L 2,5-dimethoxyterephthalaldehyde were added to a mixed solvent consisting of 500 mL of dichloromethane and 400 mL of ethanol. After ultrasonic dissolution, 0.05 mmol / L trifluoroacetic acid was added, and the mixture was allowed to stand at 20°C for 48 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0077] Preparation of a hydrophilic PAN-based microporous membrane: 8 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (35 g of caprolactam and 5 g of glycerol), heated to 180°C under nitrogen, reacted for 2 h, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0078] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 20°C for 13 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0079] After testing, the contact angle of oil under water in comparative example 2 was 167.8°, and the contact angle of water under oil was 172.4°, so it has underwater super-amphiphobicity. The separation flux and separation efficiency of oil-in-water and water-in-oil emulsions without emulsifier were 2487 L / m -2 h bar, 99.5% and 3175L / m -2h bar, more than 99.6%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 387L / m -2 h bar, 99.8% and 475L / m -2 ·h·bar, more than 99.4%. Excessive loading of COFs nanospheres seriously blocks the pores of PAN-based microporous membranes, such as Figure 6 As shown, the separation flux is seriously reduced.

[0080] Comparative Example 3

[0081] COFs powder was prepared according to the literature "Xu H, Gao J, Jiang D. Nature Chemistry, 2015, 7: 905-12", and the preparation of the hydrophilic PAN-based microporous membrane in step 1) of Example 1 and step 2) of Example 1 were adopted, specifically:

[0082] 1) Preparation of COFs powder dispersion: In a 10mL Pyrex tube, 0.08mmol of 1,3,5-tris(4-aminophenyl)benzene, 0.12mmol of 2,5-dimethoxyterephthalaldehyde, 0.1mL of catalyst (glacial acetic acid), and 1mL of a mixed solvent (0.5mL of n-butanol and 0.5mL of o-dichlorobenzene) were added. The mixture was then degassed through three freeze-pump-thaw cycles, sealed with a flame, and heated at 120°C for three days. The precipitate was collected by centrifugation, washed with THF, and subjected to Soxhlet extraction with THF for one day. The powder was collected and vacuum-extracted at 120°C for 12 hours to obtain COFs powder. The COFs were then dispersed in a mixed solvent consisting of 500mL of dichloromethane and 400mL of ethanol and sonicated for 4 hours to obtain a COFs powder dispersion.

[0083] Preparation of a hydrophilic PAN-based microporous membrane: 8 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (35 g of caprolactam and 5 g of glycerol), heated to 180°C under nitrogen, reacted for 2 h, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0084] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 20°C for 4 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0085] Testing revealed that a uniformly dispersed COF powder dispersion could not be obtained in step 1). After 5 minutes of standing, the COF powder settled. Furthermore, the COFs failed to firmly bond to the PAN-based microporous membrane and fell off after washing with ethanol and deionized water. Therefore, the prepared sample lacked submerged superamphiphobicity, indicating that large COF powders were unable to bind to the PAN-based microporous membrane through π-π stacking.

[0086] Example 2

[0087] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0088] Preparation of COFs nanosphere suspension: 1.5 mmol / L p-phenylenediamine and 1.0 mmol / L 1,3,5-triformylphloroglucinol were added to 500 mL of acetonitrile, dissolved by ultrasonication, and then 1.00 mmol / L glacial acetic acid was added. The mixture was then allowed to stand at 30°C for 48 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0089] Preparation of a hydrophilic PAN-based microporous membrane: 10 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (30 g of diphenyl carbonate and 10 g of polyvinyl alcohol), heated to 130°C under inert gas protection, reacted for 1 hour, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0090] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 30°C for 10 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0091] The test showed that the sample's underwater oil contact angle was 147.2°, and the oil-water contact angle was 157.3°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifiers were 4286 L / m -2 h bar, 96.8% and 7418 L / m -2 h bar, more than 95.2%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1052L / m -2 h bar, 96.4% and 1742 L / m -2 ·h·bar, more than 95.0%.

[0092] Example 3

[0093] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0094] Preparation of COFs nanosphere suspension: 5 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 1.0 mmol / L terephthalaldehyde were added to 500 mL of ethanol, dissolved by ultrasonication, and then 0.01 mmol / L scandium trifluoromethanesulfonate was added. The mixture was then allowed to stand at 50°C for 24 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0095] Preparation of a hydrophilic PAN-based microporous membrane: 15 g of P(AN-MA-ABP) was added to 60 g of a composite diluent (40 g of diphenyl sulfone and 20 g of dibutyl sebacate), heated to 130°C under inert gas protection, reacted for 2 h, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0096] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 50°C for 0.5 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0097] The test showed that the sample's underwater oil contact angle was 164.1° and the oil-water contact angle was 158.2°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifiers were 5871 L / m -2 h bar, 96.4% and 6247 L / m -2 h·bar, more than 94.5%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1387L / m -2 h bar, 95.9% and 1587L / m -2 ·h·bar, more than 94.2%.

[0098] Example 4

[0099] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0100] Preparation of COFs nanosphere suspension: 0.15 mmol / L benzidine and 0.1 mmol / L benzene-1,3,5-tricarbaldehyde were added to a mixed solvent consisting of 500 mL of water and 500 mL of acetonitrile. After ultrasonic dissolution, 2 mmol / L nickel nitrate was added and the mixture was allowed to stand at 25°C for 36 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0101] Preparation of a hydrophilic PAN-based microporous membrane: 15 g of P(AN-MA-ABP) was added to 45 g of a composite diluent (40 g of dimethyl sulfoxide and 5 g of acetamide), heated to 150°C under inert gas protection, reacted for 4 hours, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0102] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 25°C for 8 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0103] The test showed that the sample's underwater oil contact angle was 147.5° and the oil-water contact angle was 150.7°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifiers were 5417 L / m -2 h bar, 95.7% and 6840L / m -2 h bar, more than 97.5%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 907L / m -2 h bar, 98.8% and 1087L / m -2 ·h·bar, more than 97.4%.

[0104] Example 5

[0105] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0106] Preparation of COFs nanosphere suspension: 0.2 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 0.2 mmol / L 1,3,5-triformylphloroglucinol were added to 500 mL of dichloromethane, ultrasonically dissolved, and then 0.75 mmol / L glacial acetic acid was added. The mixture was then allowed to stand at 30°C for 48 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0107] Preparation of a hydrophilic PAN-based microporous membrane: 10 g of P(AN-MA-ABP) was added to 40 g of cyclohexylpyrrolidone, heated to 160°C under inert gas, reacted for 4 hours, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0108] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 30°C for 6 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0109] The test showed that the sample's underwater oil contact angle was 167.4° and the oil-water contact angle was 162.7°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifiers were 5457 L / m -2 h bar, 96.9% and 7415L / m -2 h bar, more than 97.2%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1354L / m -2 h bar, 95.9% and 1749 L / m -2 ·h·bar, more than 96.7%.

[0110] Example 6

[0111] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0112] Preparation of COFs nanosphere suspension: 0.75 mmol / L p-phenylenediamine (Pa) and 0.5 mmol / L benzene-1,3,5-tricarbaldehyde were added to a composite solvent consisting of 300 mL of water and 200 mL of ethyl acetate. After ultrasonic dissolution, 0.4 mmol / L of glacial acetic acid was added, and the mixture was allowed to stand at 30°C for 64 h to obtain a uniformly dispersed COFs nanosphere suspension.

[0113] Preparation of a hydrophilic PAN-based microporous membrane: 15 g of P(AN-MA-ABP) was added to 45 g of a composite diluent (including 25 g of caprolactam and 20 g of triacetin), heated to 140°C under inert gas protection, reacted for 4 hours, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent to obtain a hydrophilic PAN-based microporous membrane.

[0114] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 30°C for 10 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0115] The test showed that the sample's underwater oil contact angle was 142.9° and the oil-water contact angle was 138.9°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifier were 4878 L / m -2 h bar, 97.5% and 6410L / m -2 h·bar, more than 96.1%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1176L / m -2 h bar, 97.5% and 1743 L / m -2 ·h·bar, more than 95.7%.

[0116] Example 7

[0117] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0118] Preparation of COFs nanosphere suspension: 3 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 4.5 mmol / L 2,5-dihydroxyterephthalaldehyde were added to a mixed solvent consisting of 500 mL ethanol and 100 mL methyl acetate. After ultrasonic dissolution, 1 mmol / L p-toluenesulfonic acid was added, and the mixture was allowed to stand at 40°C for 36 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0119] Preparation of a hydrophilic PAN-based microporous membrane: 10 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (35 g of benzoyl ethyl ketone and 5 g of glycerol), heated to 180°C under inert gas protection, reacted for 1 hour, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0120] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 40°C for 2 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0121] The test showed that the sample's underwater oil contact angle was 150.4° and the oil-water contact angle was 147.8°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifier were 5875 L / m -2 h bar, 97.2% and 6481L / m -2 h·bar, more than 96.4%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1387L / m -2 h bar, 96.4% and 2044 L / m -2 ·h·bar, more than 95.8%.

[0122] Example 8

[0123] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0124] Preparation of COFs nanosphere suspension: 0.8 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 1.2 mmol / L terephthalaldehyde were added to 500 mL of dioxane, dissolved by ultrasonication, and then 0.01 mmol / L trifluoroacetic acid was added. The mixture was then allowed to stand at 10°C for 72 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0125] Preparation of a hydrophilic PAN-based microporous membrane: 10 g of P(AN-MA-ABP) was added to 40 g of a composite diluent (35 g of caprolactam and 5 g of dimethyl phthalate), heated to 150°C under inert gas protection, reacted for 3 h, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0126] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 10°C for 12 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0127] The test showed that the sample's underwater oil contact angle was 164.8° and the oil-water contact angle was 170.1°, indicating that the sample has underwater super-amphiphobicity. The separation flux and separation efficiency of the water-in-oil and oil-in-water emulsions without emulsifier were 6472 L / m -2 h bar, 98.7% and 7120L / m -2h bar, more than 97.8%, the separation flux and separation efficiency of water-in-oil and water-in-oil emulsions containing emulsifiers are 1375L / m -2 h bar, 96.8% and 1987L / m -2 ·h·bar, more than 97.5%.

[0128] Example 9

[0129] Steps 1) and 2) of Example 1 are adopted and their implementation steps are amplified, and the amplification ratio is 10 times that of Example 1. Specifically:

[0130] 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane;

[0131] Preparation of COFs nanosphere suspension: 2 mmol / L 1,3,5-tris(4-aminophenyl)benzene and 3 mmol / L 2,5-dimethoxyterephthalaldehyde were added to a mixed solvent consisting of 5000 mL of dichloromethane and 4000 mL of ethanol. After ultrasonic dissolution, 0.05 mmol / L trifluoroacetic acid was added, and the mixture was allowed to stand at 20°C for 48 hours to obtain a uniformly dispersed COFs nanosphere suspension.

[0132] Preparation of a hydrophilic PAN-based microporous membrane: 80 g of P(AN-MA-ABP) was added to 400 g of a composite diluent (350 g of caprolactam and 50 g of glycerol), heated to 180°C under inert gas protection, reacted for 2 h, and degassed to obtain a casting solution. The casting solution was then poured into a preheated mold for calendering, then cured at room temperature, and then immersed in deionized water to remove the composite diluent, thereby obtaining a hydrophilic PAN-based microporous membrane.

[0133] 2) Preparation of COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A PAN-based microporous membrane was immersed in a suspension of COFs nanospheres at 20°C for 4 h. After removal, the membrane was washed with ethanol, then with deionized water, and then dried to obtain a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

[0134] After testing, the COFs / PAN oil-water separation microporous membrane after scaled-up production of Example 1 can still efficiently and accurately separate various types of oil-water emulsions, which shows that this method is suitable for large-scale industrial production.

[0135] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a COFs / PAN oil-water separation microporous membrane with underwater superamphiphobicity, characterized in that: The method comprises the following steps: 1) Preparation of COFs nanosphere suspension and hydrophilic PAN-based microporous membrane; Preparation of COFs nanosphere suspension: adding amino monomer and aldehyde monomer to a composite solvent and dissolving them to form a homogeneous solution; then adding a catalyst and allowing the COFs nanospheres to fully grow to obtain a uniformly dispersed COFs nanosphere suspension; Preparation of a hydrophilic PAN-based microporous membrane: First, a meltable PAN terpolymer is prepared by emulsion polymerization; then, the meltable PAN terpolymer is mixed with a composite diluent, and then heated to completely dissolve the meltable PAN terpolymer. After degassing, a casting solution is obtained; the casting solution is then rolled into a shape, and then cured and formed, and the composite diluent is removed to obtain a hydrophilic PAN-based microporous membrane; 2) Preparation of a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity: A hydrophilic PAN-based microporous membrane was immersed in a suspension of COFs nanospheres, causing π-π stacking of the benzene rings in the PAN-based microporous membrane with those in the COFs nanospheres. After removal, the membrane was washed with detergent to remove the residual COFs nanosphere suspension on the surface, and then dried to remove the residual detergent, resulting in a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity.

2. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 1, characterized in that: In step 1), the amino monomer is 1,3,5-tris(4-aminophenyl)benzene, p-phenylenediamine or benzidine; the aldehyde monomer is terephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 1,3,5-triformylphloroglucinol or benzene-1,3,5-tricarbaldehyde; The composite solvent consists of a main solvent and a co-solvent, wherein the main solvent accounts for 50-100% of the volume of the composite solvent; the main solvent is water, ethanol, acetonitrile, dichloromethane, dioxane or mesitylene; the co-solvent is acetonitrile, methyl acetate, ethyl acetate, n-butanol or ethanol; The catalyst is glacial acetic acid, trifluoroacetic acid, scandium trifluoromethanesulfonate, p-toluenesulfonic acid or transition metal nitrate; the transition metal nitrate is iron nitrate, zinc nitrate, nickel nitrate, cobalt nitrate, manganese nitrate or copper nitrate.

3. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 1, characterized in that: In step 1), the molar ratio of amino groups in the amino monomer to aldehyde groups in the aldehyde monomer is 1:1; the concentrations of the amino monomer and the aldehyde monomer are both 0.1 to 5 mmol / L; and the concentration of the catalyst is 0.01 to 2 mmol / L.

4. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 1, characterized in that: In step 1), the standing temperature is 10-60° C., and the standing time is 12-72 hours; the particle size of the COFs nanoparticles ranges from 40 to 400 nm.

5. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 1, characterized in that: In step 1), the meltable PAN terpolymer component is: 80-90 mol% of a first reactive monomer, 5-20 mol% of a second reactive monomer, and 0.5-2 mol% of a third reactive monomer; the first reactive monomer is acrylonitrile, the second reactive monomer is methyl acrylate, acrylic acid or vinyl imidazole, and the third reactive monomer is 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone or stearyl benzophenone.

6. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 5, characterized in that: In step 1), the specific process for preparing the meltable PAN terpolymer by emulsion polymerization is as follows: 100-300 mL of deionized water, 1-8 g of emulsifier, and 1-5 mL of chain transfer agent are added to a reaction vessel, then nitrogen is passed through for 0.5-2 h, 10-50 mL of a mixed solution of three reaction monomers is added, and after heating to 40-80° C., 20-40 mL of an initiator solution is added. After starting the reaction, 30-90 mL of the mixed solution of the three reaction monomers is added dropwise to the reaction vessel. After reacting for 2-4 h, 30-80 mL of the initiator solution is added and the reaction is continued for 0.5-2 h. Finally, the reaction solution is poured into a 10-100 g / L magnesium sulfate solution for demulsification, allowed to stand, filtered, and dried to obtain the meltable PAN terpolymer. The emulsifier is OP-10 and / or sodium lauryl sulfate; the chain transfer agent is dodecyl mercaptan; and the initiator solution is 1-5 g / L sodium persulfate solution, potassium persulfate solution or ammonium persulfate solution.

7. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 1, characterized in that: In step 1), the composite diluent is composed of a main diluent and a secondary diluent, the main diluent accounts for 50-100% of the mass of the composite diluent; the main diluent is caprolactam, ethylene carbonate, diphenyl sulfone, diphenyl carbonate, dimethyl sulfoxide, cyclohexyl pyrrolidone or diphenyl ethyl ketone; the secondary diluent is polyvinyl alcohol, polyethylene glycol, glycerol, triacetin, polyethylene glycol monomethyl ether, dibutyl sebacate, dimethyl phthalate or acetamide.

8. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super-amphiphobicity according to claim 1, characterized in that: In step 1), the meltable PAN terpolymer accounts for 15-35% of the mass of the composite diluent.

9. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super amphiphobicity according to claim 1, characterized in that: In step 1), the heating reaction condition is to react at 130-190° C. in an oxygen-free environment for 1-4 hours.

10. The method for preparing a COFs / PAN oil-water separation microporous membrane with underwater super amphiphobicity according to claim 1, characterized in that: In step 2), the immersion temperature is 10 to 60° C., and the immersion time is 0.5 to 12 hours; The method for removing the residual COFs nanosphere suspension on the surface is to first wash it with ethanol and then with deionized water.

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