A triazine covalent organic framework membrane and its preparation method and application

Abstract

The present disclosure provides a triazine covalent organic framework membrane and its preparation method and application. A preparation method of a triazine covalent organic framework membrane includes: (1) soaking and washing a polyacrylonitrile ultrafiltration membrane in a strong base solution to obtain a pretreated ultrafiltration membrane; (2) soaking the pretreated ultrafiltration membrane in a 2-morpholinoethanesulfonic acid buffer solution containing N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and washing with water to obtain an activated ultrafiltration membrane; (3) soaking the activated ultrafiltration membrane in a first organic phase solution of a polyamine monomer and 1,4-dioxane, and washing with water; soaking in a second organic phase solution of a polyaldehyde monomer and 1,4-dioxane to obtain a modified ultrafiltration membrane; (4) immersing the modified ultrafiltration membrane in a mixed solution composed of a polyamine monomer, a polyaldehyde monomer, acetic acid and 1,4-dioxane, and cleaning to obtain a triazine covalent organic framework membrane. The triazine covalent organic framework membrane of the present application has good separation performance and catalytic oxidation performance.

Description

Technical Field

[0001] The present disclosure relates to the technical field of membrane material preparation, and particularly relates to a triazine covalent organic framework membrane, a preparation method thereof, and an application thereof. Background Art

[0002] Due to the characteristics of simple operation, high efficiency, energy conservation, and environmental friendliness, membrane separation technology has been widely applied in many fields such as food, medical treatment, energy, and water treatment. The core of membrane separation technology lies in the separation membrane. During the separation process, the membrane surface will inevitably be affected by pollutants in the feed liquid, resulting in membrane fouling. Membrane fouling refers to the process in which organic substances, inorganic substances, or microorganisms in the feed liquid adhere and accumulate on the membrane surface or in the membrane pores to form a fouling layer, which will cause a continuous decrease in the separation performance and permeation flux of the separation membrane and cannot be restored. After membrane fouling occurs on the separation membrane, there are mainly two obvious physical and chemical phenomena: 1. Severe concentration polarization and an obvious gel layer are generated on the membrane surface; 2. Adsorption and blockage occur on the membrane surface and in the membrane pores. Membrane fouling is one of the greatest challenges in the membrane separation process, severely restricting the application and operating cost of the separation membrane technology. In order to extend the service life of the separation membrane, chemical or physical cleaning methods are usually used to clean the separation membrane. However, excessive use of physical and chemical methods will cause irreversible harm to the separation membrane itself and further shorten the service life of the membrane. Therefore, how to effectively control the membrane fouling problem faced by the separation membrane during operation has become one of the most concerned issues for current membrane separation researchers.

[0003] Covalent organic framework materials (COFs) are mainly composed of light elements such as C, H, O, and N. They are a class of crystalline porous polymers connected by covalent bonds, with characteristics such as low mass density, high thermal stability, good physical and chemical stability, and permanent porosity. Covalent organic framework material COFs are a class of polymers that can be completely pre-designed and controllably synthesized, with characteristics such as large specific surface area, high porosity, adjustable pore size, and high physical and chemical stability, and have been widely used in many fields such as catalysis, optoelectronics, sensing, semiconductors, and adsorption. Among them, the application of triazine-based covalent organic framework materials (CTFs) in membrane separation‌ is mainly reflected in their unique structural and performance advantages. CTFs are composed of a graphite π-conjugated structure connected by nitrogen heterocycles, and have characteristics such as the composition of light elements (C, H, and N), porous structure, rich heteroatom participation, and extensive conjugated structure. These characteristics make CTFs perform excellently in the field of membrane separation. Triazine-based COFs (CTFs) are mainly synthesized by methods such as the condensation reaction between aldehydes and amidines, and cyano polycondensation. Because they contain an aromatic planar π-conjugated structure of 1,3,5-triazine rings, they have unique optoelectronic properties. However, their preparation conditions are harsh. For example, increasing the reaction degree and purification in an acidic medium will destroy the ordered arrangement of CTFs, resulting in poor crystallinity and porosity of the product, and it is difficult to prepare high-crystallinity products in large quantities. These defects limit the wide application of CTFs. Summary of the Invention

[0004] The present disclosure provides a triazine covalent organic framework membrane, a preparation method thereof, and an application, so as to solve at least one of the technical problems existing in the prior art.

[0005] According to the first aspect of the present disclosure, there is provided a triazine covalent organic framework membrane, including the following steps:

[0006] (1) Immerse a polyacrylonitrile ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, or a polyvinylidene fluoride ultrafiltration membrane in a strong alkali solution, soak and wash to obtain a pretreated ultrafiltration membrane;

[0007] (2) Immerse the pretreated ultrafiltration membrane in a 2-morpholinoethanesulfonic acid buffer solution containing N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide for activation treatment, and wash with water to obtain an activated ultrafiltration membrane;

[0008] (3) Immerse the activated ultrafiltration membrane in a first organic phase solution composed of a polyamine monomer and 1,4-dioxane, and wash with water; then immerse it in a second organic phase solution composed of a polyaldehyde monomer and 1,4-dioxane to obtain a modified ultrafiltration membrane; wherein, the molar volume ratio of the polyamine monomer to 1,4-dioxane is 0.27~0.41 mmol: 90~100 ml; the molar volume ratio of the polyaldehyde monomer to 1,4-dioxane is 0.3~0.46 mmol: 90~100 ml;

[0009] (4) Immerse the modified ultrafiltration membrane in a mixed solution composed of a polyamine monomer, a polyaldehyde monomer, acetic acid and 1,4-dioxane, and then alternately wash with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane; wherein, the molar volume ratio of the polyamine monomer, the polyaldehyde monomer, acetic acid and 1,4-dioxane is 0.27~0.41 mmol: 0.3~0.46 mmol: 4~5.5 ml: 50~200 ml.

[0010] In one possible implementation, in the step (1), the molar concentration of the strong base solution is 1~5 mol / L;

[0011] In the step (1), the strong base solution is one or a mixture of two of sodium hydroxide solution and potassium hydroxide solution;

[0012] In the step (1), when the polyacrylonitrile ultrafiltration membrane, the polyethersulfone ultrafiltration membrane or the polyvinylidene fluoride ultrafiltration membrane is immersed in the strong base solution, the immersion temperature is 40~80 °C and the time is 1~10 h.

[0013] In one possible implementation, in the step (2), the molar ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 1~100: 1~200;

[0014] In the step (2), the pH value of the 2-morpholinoethanesulfonic acid buffer solution is 6;

[0015] When the pretreated ultrafiltration membrane is activated in the 2-morpholinoethanesulfonic acid buffer solution, the required temperature is 40~80 °C and the immersion time is 1~10 h.

[0016] In one possible implementation, in the step (3), the immersion time of the activated ultrafiltration membrane in the first organic phase solution is 5~12 h and the immersion temperature is 20~60 °C;

[0017] In the step (3), the immersion time of the activated ultrafiltration membrane in the second organic phase solution is 1~12 h and the immersion temperature is 20~60 °C;

[0018] In step (4), the soaking time of the modified ultrafiltration membrane in the mixed solution is at least 48 h, and the soaking temperature is 20~60 °C.

[0019] In one embodiment, the polyamine monomer is a small molecule or polymer containing a secondary or polyamine group in the structural formula.

[0020] In one embodiment, the polyamine monomer includes 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, piperazine, p-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 1,4-diamino-2,5-divinylbenzene, 2,5-diaminopyridine, 5,5'-diamino-2,2'-bipyridine, m-phenylenediamine, o-phenylenediamine, 1,2,4,5-benzenetetramine, benzidine and its derivatives, C2-C12 alkyl linear diamine and its derivatives, urea, oxalic diamide, dithiooxalic diamide, 2,5-diaminoterephthalic acid, 2-sulfo-1,4-phenylenediamine, 2-isopropyl-1,4-phenylenediamine, 2,3,5,6-tetra(amino)benzoquinone, 4',5'-bis(4-aminophenyl)-[1,1':2',1”-terphenyl]-4,4”-diamine, 2,4-diamino-6-phenyl-1,3,5-triazine, 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin, tetra-(4-aminophenyl)ethylene, 1,2,4,5-tetra(4-aminophenyl)ethynyl)benzene, 3,3',4,4'-tetraaminobenzophenone, diethylenetriamine, dipropylenetriamine, dihexylenetriamine, melamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 2,6-diaminoanthracene, 4,4'-diaminotriphenyl, mellam, p-diaminoazobenzene, 4,4,4,4-ethanetetrayltetraaniline, 2,2-bis(4-aminophenyl)propane, hexakis(4-aminobiphenyl)benzene, pyrazine-2,5-diamine, oxalic dihydrazide, succinic dihydrazide, tetra(4-aminophenyl)methane, polyethyleneimine, polyvinylamine, or one or more of them.

[0021] In one embodiment, the polyaldehyde monomer is a small molecule containing a secondary or polyaldehyde group in the structural formula.

[0022] In one feasible embodiment, the polyaldehyde monomer includes one or more of 1,4-dicyanobenzene, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 1,3,5-tris(4-aminophenyl)triazine, 2,4,6-trichloro-1,3,5-triazine, glyoxal, glutaraldehyde, adipaldehyde, 1,3-butanedial, terephthalaldehyde, 2,5-dichloroterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,4-dialdehyde-2,5-divinylbenzene, 2,3,5,6-tetrafluoroterephthalaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 4,4'-biphenyldicarboxaldehyde, 2,2'-bipyridine-5,5'-dicarboxaldehyde, 1,4-bis(4-carboxyphenyl)benzene, 2,6-naphthalenedicarboxaldehyde, 1,10-phenanthroline-2,9-dicarboxaldehyde, 2,2'-bipyridine-4,4'-dicarboxaldehyde, 4-tert-butyl-2,6-formylphenol, 9,10-bis(4-carboxyphenyl)anthracene, benzene-1,3,5-tricarboxaldehyde, 4-hydroxymesitylene-1,3,5-tricarboxaldehyde, 2,4,6-triformylphloroglucinol, 1,3,5-tris(p-carboxyphenyl)benzene, tris(4-carboxyphenyl)amine, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 3,3',5,5'-tetraformyl-4,4'-dihydroxybiphenyl, tetrakis(4-carboxyphenyl)silane, 1,3,6,8-tetrakis(4-carboxyphenyl)perylene, and tetrakis(4-carboxyphenyl)ethylene.

[0023] According to a second aspect of the present disclosure, a triazine covalent organic framework membrane is provided, which is prepared by the preparation method described in any one of the first aspect.

[0024] According to a third aspect of the present disclosure, the application of the triazine covalent organic framework membrane in dye separation or photocatalysis is provided.

[0025] Compared with the prior art, the advantages of the present application are as follows: 1) The triazine covalent organic framework membrane prepared in the present application has good separation performance, especially the triazine covalent organic framework membrane prepared by the method of the present application has good dye separation performance. 2) The triazine covalent organic framework membrane of the present application has the advantages of good catalytic oxidation performance and stable performance. 3) The triazine covalent organic framework membrane of the present application has good rejection rate and permeability, especially the rejection rate. The triazine covalent organic framework membrane of the present application has a good rejection rate for dyes. 4) The preparation conditions of the triazine covalent organic framework membrane of the present application are mild and the applicable range is wide.

[0026] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it used to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. Description of the Drawings

[0027] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the drawings, several embodiments of the present disclosure are shown by way of example and not limitation, wherein:

[0028] In the drawings, the same or corresponding reference numerals denote the same or corresponding parts.

[0029] Figure 1 A flowchart showing the preparation method of the triazine covalent organic framework membrane according to an embodiment of the present disclosure is shown;

[0030] Figure 2 A physical photograph of the triazine covalent organic framework membrane obtained in Example 3 of the present disclosure, the modified PAN membrane obtained in Comparative Example 1, and the commercial PAN membrane is shown;

[0031] Figure 3 A scanning electron microscope image of the surface of the triazine covalent organic framework membrane obtained in Example 3 of the present disclosure is shown;

[0032] Figure 4 A scanning electron microscope image of the surface of the modified PAN membrane obtained by the preparation method of Comparative Example 1 of the present disclosure is shown;

[0033] Figure 5 A scanning electron microscope image of the surface of the commercial PAN membrane purchased in the present disclosure is shown;

[0034] Figure 6 An X-ray diffraction pattern of the triazine covalent organic framework membrane obtained by the preparation method of Example 3 of the present disclosure is shown;

[0035] Figure 7 A permeability graph of methyl orange by the triazine covalent organic framework membrane obtained by the preparation method of Example 3 of the present disclosure under visible light is shown;

[0036] Figure 8 A rejection performance graph of methyl orange by the triazine covalent organic framework membrane obtained by the preparation method of Example 3 of the present disclosure under visible light is shown;

[0037] Figure 9 A pure water permeability graph of the triazine covalent organic framework membranes obtained by the preparation methods of Examples 1-5 of the present disclosure is shown;

[0038] Figure 10 A permeability and rejection performance graph of gentian violet by the triazine covalent organic framework membranes obtained by the preparation methods of Examples 1-5 of the present disclosure is shown;

[0039] Figure 11 A pure water permeability graph of the triazine covalent organic framework membrane of Example 3, the modified PAN membrane of Comparative Example 1, and the commercial PAN membrane of the present disclosure is shown;

[0040] Figure 12 Shows the permeability and rejection performance diagrams of the triazine covalent organic framework membrane of Example 3 of the present disclosure, the modified PAN membrane of Comparative Example 1, and the commercial PAN membrane for Congo red. Detailed implementation manners

[0041] To make the objectives, features, and advantages of the present disclosure more obvious and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present disclosure.

[0042] In this application, first, the substrate (such as a polyacrylonitrile ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, or a polyvinylidene fluoride ultrafiltration membrane) is activated, and then it is respectively immersed in an organic phase solution containing a polyamine monomer and an organic phase solution containing a polyaldehyde monomer to load a "seed layer" on the surface of the substrate. Subsequently, the membrane is immersed in an organic phase solution containing both a polyamine monomer and a polyaldehyde monomer for in-situ growth to prepare a triazine covalent organic framework membrane. The triazine covalent organic framework membrane prepared in this application has advantages such as good separation performance, catalytic oxidation performance, and stable performance.

[0043] Specifically, according to the first aspect of the present disclosure, the present disclosure provides a method for preparing a triazine covalent organic framework membrane, including the following steps:

[0044] (1) Immerse and wash a polyacrylonitrile ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, or a polyvinylidene fluoride ultrafiltration membrane in a strong base solution to obtain a pretreated ultrafiltration membrane;

[0045] (2) Immerse the pretreated ultrafiltration membrane in a 2-morpholinoethanesulfonic acid buffer solution containing N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide for activation treatment and then wash with water to obtain an activated ultrafiltration membrane;

[0046] (3) First immerse the activated ultrafiltration membrane in a first organic phase solution composed of a polyamine monomer and 1,4-dioxane, and wash with water; then immerse it in a second organic phase solution composed of a polyaldehyde monomer and 1,4-dioxane to obtain a modified ultrafiltration membrane; wherein, the molar volume ratio of the polyamine monomer to 1,4-dioxane is 0.27~0.41 mmol: 90~100 ml; the molar volume ratio of the polyaldehyde monomer to 1,4-dioxane is 0.3~0.46 mmol: 90~100 ml;

[0047] (4) Immerse the modified ultrafiltration membrane in a mixed solution composed of polyamine monomers, polyaldehyde monomers, acetic acid and 1,4-dioxane, and then alternately wash with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane; wherein, the molar volume ratio of polyamine monomers, polyaldehyde monomers, acetic acid and 1,4-dioxane is 0.27 - 0.41 mmol: 0.3 - 0.46 mmol: 4 - 5.5 ml: 50 - 200 ml.

[0048] Preferably, in step (1), the molar concentration of the strong base solution is 1 - 5 mol / L;

[0049] In step (1), the strong base solution is one or a mixture of two of sodium hydroxide solution and potassium hydroxide solution;

[0050] In step (1), when the polyacrylonitrile ultrafiltration membrane, polyethersulfone ultrafiltration membrane or polyvinylidene fluoride ultrafiltration membrane is immersed in the strong base solution, the immersion temperature is 40 - 80 °C and the time is 1 - 10 h.

[0051] Preferably, in step (2), the molar ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 1 - 100: 1 - 200;

[0052] In step (2), the 2-morpholinoethanesulfonic acid buffer solution is adjusted to a pH value of 6 with hydrochloric acid solution;

[0053] When the pretreated ultrafiltration membrane is activated in the buffer solution, the required temperature is 40 - 80 °C and the immersion time is 1 - 10 h.

[0054] Preferably, in step (3), the immersion time of the activated ultrafiltration membrane in the first organic phase solution is 5 - 12 h and the immersion temperature is 20 - 60 °C;

[0055] In step (3), the immersion time of the activated ultrafiltration membrane in the second organic phase solution is 1 - 12 h and the immersion temperature is 20 - 60 °C.

[0056] Preferably, in step (3), the molar volume ratio of the polyamine monomer to 1,4-dioxane is 0.27~0.41 mmol: 90 ml, 0.27~0.41 mmol: 92 ml, 0.27~0.41 mmol: 94 ml, 0.27~0.41 mmol: 96 ml, 0.27~0.41 mmol: 98 ml, 0.27~0.41 mmol: 100 ml; the molar volume ratio of the polyaldehyde monomer to 1,4-dioxane is 0.3~0.46 mmol: 90 ml, 0.3~0.46 mmol: 92 ml, 0.3~0.46 mmol: 94 ml, 0.3~0.46 mmol: 96 ml, 0.3~0.46 mmol: 98 ml, 0.3~0.46 mmol: 100 ml.

[0057] Preferably, in step (4), the soaking time of the modified ultrafiltration membrane in the mixed solution is at least 48 h, and the soaking temperature is 20~60 °C.

[0058] Preferably, the polyamine monomer is a small molecule or polymer containing a secondary or poly-primary amine group in the structural formula.

[0059] The polyamine monomers include 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, piperazine, p-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 1,4-diamino-2,5-divinylbenzene, 2,5-diaminopyridine, 5,5'-diamino-2,2'-bipyridine, m-phenylenediamine, o-phenylenediamine, 1,2,4,5-benzenetetramine, benzidine and its derivatives, C2-C12 alkyl straight-chain diamines and their derivatives, urea, oxalyl diamide, dithiooxalyl diamide, 2,5-diaminoterephthalic acid, 2-sulfo-1,4-phenylenediamine (also known as 1,4-phenylenediamine-2-sulfonic acid), 2-isopropyl-1,4-phenylenediamine, 2,3,5,6-tetra(amino)benzoquinone, 4',5'-bis(4-aminophenyl)-[1,1':2',1''-terphenyl]-4,4''-diamine, 2,4-diamino-6-phenyl-1,3,5-triazine, 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin, tetra-(4-aminophenyl)ethylene, 1,2,4,5-tetra(4-aminophenyl)ethynyl)benzene, 3,3',4,4'-tetraaminobenzophenone, diethylenetriamine, dipropylenetriamine, dihexylenetriamine, melamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 2,6-diaminoanthracene, 4,4'-diaminotriphenyl, melamine, p-diaminoazobenzene, 4,4,4,4-ethanetetrayltetraaniline, 2,2-bis(4-aminophenyl)propane, hexakis(4-aminobiphenyl)benzene, pyrazine-2,5-diamine, oxalic dihydrazide, succinic dihydrazide, tetra(4-aminophenyl)methane, polyethyleneimine, polyvinylamine, or one or more of them.

[0060] Preferably, the polyaldehyde monomer is a small molecule containing two or more aldehyde groups in its structural formula.

[0061] The polyaldehyde monomers include 1,4-dicyanobenzene, 2,5-dimethoxybenzene-1,4-dicarbaldehyde, 1,3,5-tris(4-aminophenyl)-1,3,5-triazine, 2,4,6-trichloro-1,3,5-triazine, glyoxal, glutaraldehyde, adipaldehyde, 1,3-butanedial, terephthalaldehyde, 2,5-dichloroterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,4-dialdehyde-2,5-divinylbenzene, 2,3,5,6-tetrafluoroterephthalaldehyde, 2,5-dimethoxybenzene-1,4-dicarbaldehyde, 4,4'-biphenyldicarbaldehyde, 2,2'-bipyridine-5,5'-dicarbaldehyde, 1,4-bis(4-formylphenyl)benzene, 2,6-naphthalenedicarbaldehyde, 1,10-phenanthroline-2,9-dicarbaldehyde, 2,2'-bipyridine-4,4'-dicarbaldehyde, 4-tert-butyl-2,6-formylphenol, 9,10-bis(4-formylphenyl)anthracene, phloroglucinol tricarbaldehyde, 4-hydroxymesitylene tricarbaldehyde, 2,4,6-triformylphloroglucinol, 1,3,5-tris(p-formylphenyl)benzene, tris(4-formylphenyl)amine, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 3,3',5,5'-tetraformyl-4,4'-dihydroxybiphenyl, tetrakis(4-formylphenyl)silane, 1,3,6,8-tetrakis(4-formylphenyl)perylene, tetrakis(4-formylphenyl)ethylene, or one or more of them.

[0062] Preferably, when the polyamine monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, the mass-volume ratio of the polyamine monomer to 1,4-dioxane is 0.096 - 0.144 g:90 - 100 ml. When the polyaldehyde monomer is 2,4,6-triformylphloroglucinol, the mass-volume ratio of the polyaldehyde monomer to 1,4-dioxane is 0.064 - 0.096 g:90 - 100 ml.

[0063] According to the second aspect of the present disclosure, a triazine covalent organic framework membrane is provided, which is prepared by the preparation method described in any one of the above.

[0064] According to the third aspect of the present disclosure, an application of the triazine covalent organic framework membrane in dye separation is provided. Specifically, the use of the triazine covalent organic framework membrane in the separation of small molecule organic compounds is provided. For example, the small molecule organic compound is a dye.

[0065] According to the fourth aspect of the present disclosure, an application of the triazine covalent organic framework membrane in photocatalysis is provided. For example, the application of the triazine covalent organic framework membrane in photocatalytic dye degradation is provided.

[0066] There are no special restrictions on the sources of all raw materials in this application, and they can be commercially available ones.

[0067] The method for detecting water permeability in this application is as follows:

[0068] The rejection performance of the membrane for dyes in the dark and under visible light irradiation (50W xenon lamp) with a wavelength of 420 nm - 780 nm is tested using a cross-flow test system. The test system consists of components such as a pump, a membrane cell, pipelines, a regulating valve, a pressure and flow detector, etc. Among them, the effective membrane area for testing is 4.9 cm 2 , the test pressure is 0.5 bar, and the test temperature is 25 ± 0.5 °C.

[0069] The calculation formula for water permeability is as follows:

[0070] J = V / [A × Δt × Δp]

[0071] Among them, J is the water permeability of the membrane (L m -2 h -1 bar -1 ), V is the volume of the permeate (L), A is the effective area of the membrane (m 2 ), Δt is the permeation time (h), and Δp is the test pressure (bar).

[0072] The calculation formula for the dye rejection rate is as follows:

[0073] R = (1 - C p / C f ) × 100%

[0074] Among them, C p is the concentration of the permeate (g L -1 ), and C f is the concentration of the feed solution (g L -1 ).

[0075] The calculation formula for the dye rejection rate under light irradiation is as follows:

[0076] R = (C / C0) × 100%

[0077] Among them, C is the concentration of the permeate (g L -1 ), and C0 is the concentration of the feed solution (g L -1 ).

[0078] In the catalytic oxidation reaction system of this application, the concentration of organic pollutants is 50 ppm, and the organic pollutants include one or more combinations of gentian violet, congo red, methyl orange, and evans blue.

[0079] The following further elaborates on this application in combination with specific embodiments:

[0080] Example 1

[0081] A method for preparing a triazine covalent organic framework membrane, comprising the following steps:

[0082] Step (1): Pretreatment: Immerse a polyacrylonitrile ultrafiltration membrane in a 1 mol / L sodium hydroxide solution, place it in an oven at 60 °C for 2 hours, and then rinse it with deionized water to obtain a pretreated polyacrylonitrile ultrafiltration membrane;

[0083] Step (2): Activation treatment: Immerse the pretreated polyacrylonitrile ultrafiltration membrane in 50 ml of 2-morpholinoethanesulfonic acid buffer solution (pH = 6) containing 3.5 g of N-hydroxysuccinimide and 15 ml of 100 mM 1-ethyl-(3-dimethylaminopropyl)carbodiimide; soak it at 40 °C for 4 hours to activate it, and then rinse it with deionized water to obtain an activated ultrafiltration membrane;

[0084] Step (3): Modification treatment: First immerse the activated ultrafiltration membrane in 100 ml of 1,4-dioxane solution containing 0.096 g (0.27 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, soak it at room temperature (25 °C) for 12 hours, and then rinse it with deionized water; then immerse it in 100 ml of 1,4-dioxane solution containing 0.064 g (0.30 mmol) of 2,4,6-triformylphloroglucinol, soak it at room temperature for 1 h to obtain a modified CHPAN membrane (modified polyacrylonitrile ultrafiltration membrane);

[0085] Step (4): In-situ growth: Dissolve 0.096 g (0.27 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.064 g (0.30 mmol) of 2,4,6-triformylphloroglucinol in a mixed solution composed of 4 ml of acetic acid and 100 ml of 1,4-dioxane, then immerse the modified CHPAN membrane in this mixed solution and soak it at room temperature for 2 days, and wash it three times alternately with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane.

[0086] Figure 9 This is the pure water permeability diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 1. As can be seen from Figure 9 it, the pure water permeability of the triazine covalent organic framework membrane in Example 1 is approximately 355.4 L m -2 h -1 bar -1 .

[0087] Figure 10Permeability and retention performance diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 1 for gentian violet, as shown in Figure 10 shown, the permeability of the triazine covalent organic framework membrane of Example 1 for gentian violet is approximately 172.0 L m - 2 h -1 bar -1 , and the retention rate is 74.39%.

[0088] Example 2

[0089] A preparation method of a triazine covalent organic framework membrane, comprising the following steps:

[0090] Step (1): Pretreatment: Immerse the polyacrylonitrile ultrafiltration membrane in a 1 mol / L sodium hydroxide solution, place it in an oven at 60 °C for 2 hours, and then rinse with deionized water to obtain a pretreated polyacrylonitrile ultrafiltration membrane;

[0091] Step (2): Activation treatment: Immerse the pretreated polyacrylonitrile ultrafiltration membrane in 50 ml of 2-morpholinoethanesulfonic acid buffer solution (pH = 6), which contains 3.5 g (30.4 mmol) of N-hydroxysuccinimide and 15 ml of 100 mM 1-ethyl-(3-dimethylaminopropyl)carbodiimide; soak at 50 °C for 4 hours to activate it, and then rinse with deionized water to obtain an activated polyacrylonitrile ultrafiltration membrane;

[0092] Step (3): Modification treatment: First immerse the activated polyacrylonitrile ultrafiltration membrane in a 100 ml 1,4-dioxane solution containing 0.108 g (0.30 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, soak at room temperature for 12 hours, and then rinse with deionized water; then immerse it in a 100 ml 1,4-dioxane solution containing 0.072 g (0.34 mmol) of 2,4,6-triformylphloroglucinol, soak at room temperature for 1 h to obtain a modified CHPAN membrane (modified polyacrylonitrile ultrafiltration membrane);

[0093] Step (4): In-situ growth: Dissolve 0.108 g (0.30 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.072 g (0.34 mmol) of 2,4,6-triformylphloroglucinol in a mixed solution composed of 4.5 ml of acetic acid and 100 ml of 1,4-dioxane, immerse the CHPAN membrane and soak at room temperature for 2 days, and alternately wash it three times with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane.

[0094] Figure 9This is the pure water permeability diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 2. From Figure 9 it can be seen that the pure water permeability of the triazine covalent organic framework membrane of Example 2 is approximately 286.6 L m -2 h -1 bar -1 .

[0095] Figure 10 This is the permeability and rejection performance diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 2 for gentian violet. As Figure 10 shown, the permeability of the triazine covalent organic framework membrane of Example 2 for gentian violet is approximately 121.7 L m - 2 h -1 bar -1 , and the rejection rate is 84.85%.

[0096] Example 3

[0097] A preparation method of a triazine covalent organic framework membrane, comprising the following steps:

[0098] Step (1): Pretreatment: Immerse the polyacrylonitrile ultrafiltration membrane in a 1 mol / L sodium hydroxide solution, place it in an oven at 60 °C for 2 hours, and then rinse it with deionized water to obtain a pretreated polyacrylonitrile ultrafiltration membrane;

[0099] Step (2): Activation treatment: Immerse the pretreated polyacrylonitrile ultrafiltration membrane in a 50 ml 2-morpholinoethanesulfonic acid buffer solution (pH = 6) containing 3.5 g of N-hydroxysuccinimide and 15 ml of 100 mM 1-ethyl-(3-dimethylaminopropyl)carbodiimide; soak it at 60 °C for 4 hours to activate it, and then rinse it with deionized water to obtain an activated polyacrylonitrile ultrafiltration membrane;

[0100] Step (3): Modification treatment: First immerse the activated polyacrylonitrile ultrafiltration membrane in a 100 ml 1,4-dioxane solution containing 0.12 g (0.34 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, soak it at room temperature for 12 hours, and then rinse it with deionized water; then immerse it in a 100 ml 1,4-dioxane solution containing 0.08 g (0.38 mmol) of 2,4,6-triformylphloroglucinol, soak it at room temperature for 1 h to obtain a modified polyacrylonitrile ultrafiltration membrane (modified CHPAN membrane);

[0101] Step (4): In-situ growth: Dissolve 0.12 g (0.34 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.08 g (0.38 mmol) of 2,4,6-triformylphloroglucinol in a mixed solution composed of 5 ml of acetic acid and 100 ml of 1,4-dioxane. Immerse the modified CHPAN membrane and soak it at room temperature for 2 days. Wash it three times alternately with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane.

[0102] Figure 2 Figure 2 shows the physical photos of the triazine covalent organic framework membrane obtained by the preparation method of Example 3, the modified PAN membrane obtained by the preparation method of Comparative Example 1, and the commercial PAN membrane. It can be seen from the figure that the original commercial PAN membrane is white, yellow after modification (Comparative Example 1), and orange after in-situ growth is completed (Example 3), showing obvious color differences.

[0103] Figure 3 Figure 3 shows the scanning electron microscopy image of the surface of the triazine covalent organic framework membrane obtained by the preparation method of Example 3. It can be seen from Figure 3 that the surface of the polyacrylonitrile ultrafiltration membrane is covered with a reticular structure, indicating that the COF layer (covalent organic framework material layer) grows well.

[0104] Figure 6 Figure 4 shows the X-ray diffraction pattern of the triazine covalent organic framework membrane obtained by the preparation method of Example 3. Among them, 5.8° corresponds to the 100 crystal plane of the triazine covalent organic framework, but the characteristic peak is not obvious, which may be due to the too thin COF layer. At the same time, the growth of COF on the polyacrylonitrile ultrafiltration membrane sacrifices crystallinity. 25-27° corresponds to the 001 crystal plane, and this characteristic peak proves the π-π stacking of the COF two-dimensional layer.

[0105] Figure 7 Figure 5 shows the permeability diagram of methyl orange by the triazine covalent organic framework membrane obtained by the preparation method of Example 3 under visible light. It can be seen that within 30 minutes after turning off the light, the permeability of methyl orange of the triazine covalent organic framework membrane decreases rapidly from 300 L m -2 h - 1 bar -1 to 250 L m -2 h -1 bar -1 This indicates that the surface of the triazine covalent organic framework membrane is severely blocked by dye molecules. However, under the irradiation of visible light, the decreasing trend of the permeability of the triazine covalent organic framework membrane slows down significantly, indicating that the membrane surface blockage situation has eased. This shows that under visible light irradiation, the triazine covalent organic framework membrane has photocatalytic oxidation performance for dye molecules.

[0106] Figure 8Retention performance diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 3 herein for methyl orange. Within 30 minutes after turning off the light, the retention rate of the triazine covalent organic framework membrane for methyl orange is close to 20%, which may be due to the accumulation of dye molecules on the surface of the triazine covalent organic framework membrane, resulting in the loss of the permeability of the triazine covalent organic framework membrane. Under visible light irradiation, the retention rate of the triazine covalent organic framework membrane for methyl orange is stable at about 25%.

[0107] Figure 9 Pure water permeability diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 3 of the present invention. As can be seen from Figure 9 it, the pure water permeability of the triazine covalent organic framework membrane of Example 3 is approximately 272.6 L m -2 h -1 bar -1 .

[0108] Figure 10 Permeability and retention performance diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 3 herein for gentian violet. As shown in Figure 10 it, the permeability of the triazine covalent organic framework membrane of Example 3 for gentian violet is approximately 96.2 L m -2 h -1 bar -1 , and the retention rate is 90.42%.

[0109] Example 4

[0110] A preparation method of a triazine covalent organic framework membrane, comprising the following steps:

[0111] Step (1): Pretreatment: Immerse the polyacrylonitrile ultrafiltration membrane in a 1 mol / L sodium hydroxide solution, place it in an oven at 60 °C for 2 hours, and then rinse with deionized water to obtain a pretreated polyacrylonitrile ultrafiltration membrane;

[0112] Step (2): Activation treatment: Immerse the pretreated polyacrylonitrile ultrafiltration membrane in 50 ml of 2-morpholinoethanesulfonic acid buffer solution (pH = 6), wherein the buffer solution contains 3.5 g of N-hydroxysuccinimide and 15 ml of 100 mM 1-ethyl-(3-dimethylaminopropyl) carbodiimide; soak it at 80 °C for 4 hours to activate it, and then rinse with deionized water to obtain an activated polyacrylonitrile ultrafiltration membrane;

[0113] Step (3): Modification treatment: Immerse the activated polyacrylonitrile ultrafiltration membrane in a 100 ml 1,4-dioxane solution containing 0.132 g (0.37 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and soak for 12 hours at room temperature, then rinse with deionized water; then immerse it in a 100 ml 1,4-dioxane solution containing 0.088 g (0.42 mmol) of 2,4,6-triformylphloroglucinol and soak for 1 h at room temperature to obtain a modified CHPAN membrane (modified polyacrylonitrile ultrafiltration membrane);

[0114] Step (4): In-situ growth: Dissolve 0.132 g (0.37 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.088 g (0.42 mmol) of 2,4,6-triformylphloroglucinol in a mixed solution composed of 5.5 ml of acetic acid and 100 ml of 1,4-dioxane, immerse the modified CHPAN membrane and soak for 2 days at room temperature, and wash it three times alternately with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane.

[0115] Figure 9 This is the pure water permeability diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 4. As can be seen from Figure 9 it, the pure water permeability of the triazine covalent organic framework membrane of Example 4 is approximately 309.6 L m -2 h -1 bar -1 .

[0116] Figure 10 This is the permeability and retention performance diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 4 for gentian violet. As shown in Figure 10 it, the permeability of the triazine covalent organic framework membrane of Example 4 for gentian violet is approximately 146.5 L m - 2 h -1 bar -1 , and the rejection rate is 81.11%.

[0117] Example 5

[0118] A preparation method of a triazine covalent organic framework membrane, comprising the following steps:

[0119] Step (1): Immerse the polyacrylonitrile ultrafiltration membrane in a 1 mol / L sodium hydroxide solution, place it in an oven at 60 °C for 2 hours, and then rinse with deionized water to obtain a pretreated polyacrylonitrile ultrafiltration membrane;

[0120] Step (2): Immerse the pretreated polyacrylonitrile ultrafiltration membrane in 50 ml of 2-morpholinoethanesulfonic acid buffer solution (pH = 6), where the buffer solution contains 3.5 g of N-hydroxysuccinimide and 15 ml of 100 mM 1-ethyl-(3-dimethylaminopropyl)carbodiimide; soak at 60 °C for 4 hours to activate it, and then rinse with deionized water to obtain the activated polyacrylonitrile ultrafiltration membrane;

[0121] Step (3): Modification treatment: First, immerse the activated polyacrylonitrile ultrafiltration membrane in 100 ml of 1,4-dioxane solution containing 0.144 g (0.41 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, soak at room temperature for 12 hours, and then rinse with deionized water; then immerse it in 100 ml of 1,4-dioxane solution containing 0.096 g (0.46 mmol) of 2,4,6-triformylphloroglucinol, soak at room temperature for 1 h to obtain the modified CHPAN membrane (modified polyacrylonitrile ultrafiltration membrane);

[0122] Step (4): In-situ growth: Dissolve 0.144 g (0.41 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.096 g (0.46 mmol) of 2,4,6-triformylphloroglucinol in a mixed solution composed of 5.5 ml of acetic acid and 100 ml of 1,4-dioxane, immerse the modified CHPAN membrane and soak at room temperature for 2 days, and wash it three times alternately with deionized water and 1,4-dioxane to obtain the triazine covalent organic framework membrane.

[0123] Figure 9 This is the pure water permeability diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 5. From Figure 9 it can be seen that the pure water permeability of the Example 5-triazine covalent organic framework membrane is approximately 387.3 L m -2 h -1 bar -1 .

[0124] Figure 10 This is the permeability and retention performance diagram of the triazine covalent organic framework membrane obtained by the preparation method of Example 5 for gentian violet. As Figure 10 shown, the permeability of the Example 5-triazine covalent organic framework membrane for gentian violet is approximately 204.5 L m - 2 h -1 bar -1 , and the rejection rate is 69.6%.

[0125] Comparative Example 1

[0126] A preparation method of a modified polyacrylonitrile ultrafiltration membrane, comprising the following steps:

[0127] Step (1): Pretreatment: Immerse the polyacrylonitrile ultrafiltration membrane in a 1 mol / L sodium hydroxide solution, place it in an oven at 60 °C for 2 hours, and then rinse it with deionized water to obtain a pretreated polyacrylonitrile ultrafiltration membrane;

[0128] Step (2): Activation treatment: Immerse the pretreated polyacrylonitrile ultrafiltration membrane in 50 ml of 2-morpholinoethanesulfonic acid buffer solution (pH = 6) containing 50 mM N-hydroxysuccinimide and 100 mM 1-ethyl-(3-dimethylaminopropyl)carbodiimide; soak it at 60 °C for 4 hours to activate it, and then rinse it with deionized water to obtain an activated PAN membrane (activated polyacrylonitrile ultrafiltration membrane);

[0129] Step (3): Modification treatment: First immerse the activated PAN membrane in 100 ml of 1,4-dioxane solution containing 0.12 g of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, soak it at room temperature for 12 hours, and then rinse it with deionized water; then immerse it in 100 ml of 1,4-dioxane solution containing 0.08 g of 2,4,6-triformylphloroglucinol, soak it at room temperature for 1 h to obtain a modified polyacrylonitrile ultrafiltration membrane (denoted as "modified PAN membrane").

[0130] Figure 4 is the surface scanning electron micrograph of the modified PAN membrane obtained by the preparation method of Comparative Example 1. Compared with Figure 5 the surface scanning electron micrograph of the purchased commercial PAN membrane, it can be observed that after modification, the pores on the surface of the PAN membrane are significantly reduced, and the pore size of the pores is also significantly reduced.

[0131] Figure 11 is the pure water permeability diagram of the modified PAN membrane obtained by the preparation method of Comparative Example 1 and the commercial PAN membrane (i.e., the original PAN membrane). From Figure 11 it can be seen that the pure water permeability of the original PAN membrane is approximately 473.9 L m -2 h -1 bar -1 , and the pure water permeability of the modified PAN membrane obtained in Comparative Example 1 is approximately 412.7 L m -2 h -1 bar -1 , which is due to the high pure water permeability caused by the presence of large pores in the PAN membrane itself.

[0132] Figure 12This is a graph showing the permeability and retention performance of the modified PAN membrane obtained by the preparation method of Comparative Example 1 and the commercial PAN membrane (i.e., the original PAN membrane) for Congo red. The Congo red permeability of the original PAN membrane is 250.96 L m -2 h -1 bar -1 , and the retention rate is 60.19%. The Congo red permeability of the modified PAN membrane obtained in Comparative Example 1 is 179.62 L m -2 h -1 bar -1 , and the retention rate is 87.84%. In comparison, the Congo red permeability of the triazine covalent organic framework membrane prepared in Example 3 is 98.09 L m -2 h - 1 bar -1 , and the retention rate is as high as 99.6%. This shows that in-situ growth of the COF layer significantly improves the retention performance of the membrane, while at the same time resulting in a slight decrease in permeability.

[0133] Based on the above embodiments, the triazine covalent organic framework membrane prepared in this application has good separation performance and catalytic oxidation performance, high retention rate for dyes, and has the advantages of recyclability and low economic cost.

[0134] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added, or deleted. For example, the steps recorded in this disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved. This is not limited herein.

[0135] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this disclosure, "a plurality" means two or more unless otherwise specifically defined.

[0136] The above is only the specific implementation manner of this disclosure, but the protection scope of this disclosure is not limited thereto. Any person skilled in the art within the technical scope disclosed in this disclosure can easily think of changes or substitutions, which should all be covered within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be subject to the protection scope of the claims.

Claims

1. A preparation method of a triazine covalent organic framework membrane for dye separation or photocatalysis, characterized in that: It includes the following steps: (1) Immerse a polyacrylonitrile ultrafiltration membrane, a polyethersulfone ultrafiltration membrane or a polyvinylidene fluoride ultrafiltration membrane in a strong base solution, soak and wash to obtain a pretreated ultrafiltration membrane; (2) Immerse the pretreated ultrafiltration membrane in a 2-morpholinoethanesulfonic acid buffer solution containing N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide for activation treatment and water washing to obtain an activated ultrafiltration membrane; (3) Immerse the activated ultrafiltration membrane in a first organic phase solution composed of a polyamine monomer and 1,4-dioxane, soak and wash with water; then immerse it in a second organic phase solution composed of a polyaldehyde monomer and 1,4-dioxane to obtain a modified ultrafiltration membrane; wherein, the molar volume ratio of the polyamine monomer to 1,4-dioxane is 0.27~0.41 mmol: 90~100 ml; the molar volume ratio of the polyaldehyde monomer to 1,4-dioxane is 0.3~0.46 mmol: 90~100 ml; (4) Immerse the modified ultrafiltration membrane in a mixed solution composed of a polyamine monomer, a polyaldehyde monomer, acetic acid and 1,4-dioxane, and then alternately wash it with deionized water and 1,4-dioxane to obtain a triazine covalent organic framework membrane; wherein, the molar volume ratio of the polyamine monomer, the polyaldehyde monomer, acetic acid and 1,4-dioxane is 0.27~0.41 mmol: 0.3~0.46 mmol: 4~5.5 ml: 50~200 ml; Wherein, in the step (3), the immersion time of the activated ultrafiltration membrane in the first organic phase solution is 5~12 h and the immersion temperature is 20~60 °C; In the step (3), the immersion time of the activated ultrafiltration membrane in the second organic phase solution is 1~12 h and the immersion temperature is 20~60 °C; In the step (4), the immersion time of the modified ultrafiltration membrane in the mixed solution is at least 48 h and the immersion temperature is 20~60 °C; Wherein, the polyamine monomer in the step (3) and the step (4) is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; the polyaldehyde monomer in the step (3) and the step (4) is 2,4,6-triformylphloroglucinol.

2. The preparation method according to claim 1, characterized in that: In the step (1), the molar concentration of the strong base solution is 1~5 mol / L; In the step (1), the strong base solution is one or a mixture of two of sodium hydroxide solution and potassium hydroxide solution; In the step (1), when the polyacrylonitrile ultrafiltration membrane, the polyethersulfone ultrafiltration membrane or the polyvinylidene fluoride ultrafiltration membrane is immersed in the strong base solution, the immersion temperature is 40~80 °C and the time is 1~10 h.

3. The preparation method according to claim 1, wherein: In the step (2), the molar ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 1~100: 1~200; In the step (2), the pH value of the 2-morpholinoethanesulfonic acid buffer solution is 6; When the pretreated ultrafiltration membrane is activated in the 2-morpholinoethanesulfonic acid buffer solution, the required temperature is 40~80 °C and the immersion time is 1~10 h.

4. A triazine covalent organic framework membrane, characterized in that: It is prepared by the preparation method described in any one of claims 1-3.

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