Triazine covalent organic framework photocatalytic composite film, and preparation method and application thereof

Abstract

This invention discloses a triazine covalent organic framework (COFs) photocatalytic composite membrane, its preparation method, and its applications. The preparation method includes: preparing amino-functionalized fluoropolymer film materials and titanium carbide materials separately; mixing them with organic monomers, organic solvents, and acid catalysts to carry out a condensation reaction to obtain the triazine covalent organic framework photocatalytic composite membrane. The triazine covalent organic framework photocatalytic composite membrane prepared by this invention has advantages such as high bonding strength, high photocatalytic activity, stable physicochemical properties, strong pollutant interception capacity, simple recovery, and long service life. It is a novel COFs composite membrane material with dual functions of photocatalysis and filtration, and can be used as a photocatalyst and filter membrane in water treatment devices. It can be widely used in the field of water treatment, maintaining stability under high temperature, strong acid, and strong alkali conditions and achieving efficient removal of organic pollutants in water. It has high application value and good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, and relates to a photocatalytic composite membrane, its preparation method and application, specifically a triazine covalent organic framework photocatalytic composite membrane, its preparation method and application. Background Technology

[0002] Covalent organic frameworks (COFs) are crystalline network materials composed of symmetrical organic monomers linked by strong covalent bonds. They possess advantages such as large specific surface area, low density, high porosity, controllable physicochemical properties, ease of functionalization, and diverse synthesis strategies, exhibiting excellent performance in numerous fields and attracting considerable attention from researchers. However, existing COF membrane materials suffer from problems such as poor charge separation efficiency, low conductivity, irregular morphology, weak processability, poor mechanical strength of the film morphology, uneven thickness and low crystallinity of self-supporting films, poor bonding strength, and unstable chemical properties. These issues significantly limit the widespread application of COF membrane materials. Furthermore, while titanium carbide is introduced into existing COF composites to improve conductivity, these materials are mostly powders and cannot be used in water treatment. Furthermore, existing COFs composite membrane materials, obtained only through vacuum filtration, suffer from drawbacks such as low bonding strength, poor photocatalytic activity, poor stability, and poor pollutant interception capacity. This makes them unsuitable for removing organic pollutants from water bodies, and their tendency to disintegrate and enter the water during use can easily lead to secondary pollution. Therefore, obtaining a covalent organic framework photocatalytic composite membrane with high bonding strength, high photocatalytic activity, stable physicochemical properties, strong pollutant interception capacity, and long service life is of great significance for the effective removal of pollutants from wastewater. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a triazine covalent organic framework photocatalytic composite membrane with high bonding strength, high photocatalytic activity, stable physicochemical properties, strong pollutant interception ability, and long service life, as well as its preparation method and application.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a triazine covalent organic framework photocatalytic composite film includes the following steps:

[0006] S1. Amination treatment is performed on fluoropolymer film material and titanium carbide material respectively to obtain amino-functionalized fluoropolymer film material and amino-functionalized titanium carbide material.

[0007] S2. The amino-functionalized fluoropolymer film material, amino-functionalized titanium carbide material, organic monomer, organic solvent and acid catalyst obtained in step S1 are mixed and subjected to condensation reaction to obtain triazine covalent organic framework photocatalytic composite film.

[0008] A further improvement to the above preparation method involves amination of the fluoropolymer material, including the following steps:

[0009] (a1) A mixed solution A is used to treat the surface of a fluoropolymer film material; the mixed solution A is obtained by mixing hydrogen peroxide and sulfuric acid;

[0010] (a2) The surface-treated fluoropolymer film material and mixed solution B are mixed and subjected to a freeze-pump-thaw cycle for degassing; the mixed solution B is obtained by mixing toluene and tri-aminopropyltriethoxysilane;

[0011] (a3) The fluoropolymer film material after being degassed by the freezing-pumping-thawing cycle is heated to 110°C to carry out an amination reaction to obtain an amino-functionalized fluoropolymer film material.

[0012] In a further improvement to the above preparation method, in step (a1), the volume ratio of hydrogen peroxide to sulfuric acid in the mixed solution A is 1:1; the mass fraction of hydrogen peroxide is 30%; the fluoropolymer film material is a polytetrafluoroethylene film or a polyvinylidene fluoride film; the pore size of the fluoropolymer film material is 0.1 μm to 0.22 μm; and the surface treatment time is 20 min.

[0013] In a further improvement to the above preparation method, in step (a2), the volume ratio of toluene to tri-aminopropyltriethoxysilane in the mixed solution B is 10:1; the number of times the freeze-pump-thaw cycle degasses is 3.

[0014] In a further improvement to the above preparation method, in step (a3), the amination reaction time is 2 hours.

[0015] The above preparation method is further improved by subjecting the titanium carbide material to amination treatment, which includes the following steps: mixing the titanium carbide material and mixed solution C, stirring, washing, and freeze-drying to obtain the amination-functionalized titanium carbide material; wherein the mixed solution C is obtained by mixing tri-aminopropyltriethoxysilane, ethanol, and water.

[0016] In a further improvement to the above preparation method, the ratio of the titanium carbide material, tri-aminopropyltriethoxysilane, ethanol, and water is 240 mg: 1.6 mL: 90 mL: 30 mL; during the amination treatment of the titanium carbide material, the stirring is carried out under an inert atmosphere for 24 hours; the washing solution used in the washing process is an ethanol / water mixture; the volume ratio of ethanol to water in the ethanol / water mixture is 3:1; the titanium carbide material is prepared by the following method: placing titanium aluminum carbide in a hydrochloric acid / lithium fluoride mixture, stirring at 500 rpm to 600 rpm for 24 hours, washing, sonicating, centrifuging, and freeze-drying to obtain the titanium carbide material; the hydrochloric acid / lithium fluoride mixture is prepared by the following method: mixing lithium fluoride and hydrochloric acid, stirring at 500 rpm to 600 rpm for 30 minutes to obtain the hydrochloric acid / lithium fluoride mixture; the ratio of lithium fluoride to hydrochloric acid is 1.5 g: 10 mL.

[0017] In a further improvement to the above preparation method, in step S2, the organic monomers are 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine; the mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde to 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine is 39.3:35.4; the mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde to amino-functionalized titanium carbide material is 39.3:0 to 8, but the amount of amino-functionalized titanium carbide material is not zero; the organic solvent, acid catalyst, 4,4′,4″- The ratio of (1,3,5-triazine-2,4,6-trimethyl)tribenzaldehyde was 14 mL : 1.4 mL : 39.3 mg.

[0018] In a further improvement to the above preparation method, the mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde to amino-functionalized titanium carbide material is 39.3:1-3; the organic solvent is a mixture of 1,4-dioxane and mesitylene; the volume ratio of 1,4-dioxane and mesitylene in the mixture is 1:1; the acid catalyst is an acetic acid solution; and the concentration of the acetic acid solution is 3M.

[0019] The above preparation method can be further improved by step S2 as follows:

[0020] S2-1. Mix amino-functionalized fluoropolymer film material, organic solvent, and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde, sonicate for 5 min, add acid catalyst, sonicate for 5 min, add 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine, sonicate for 5 min, add amino-functionalized titanium carbide material, sonicate for 5 min, and obtain a mixture;

[0021] S2-2. Argon gas is bubbled through the mixture for 10-15 minutes to degas it. The mixture is then heated to 120°C for condensation reaction for 72 hours. After washing, filtering, and drying, a triazine covalent organic framework photocatalytic composite membrane is obtained.

[0022] As a general technical concept, the present invention also provides a method for preparing a triazine covalent organic framework photocatalytic composite membrane, wherein the triazine covalent organic framework photocatalytic composite membrane uses a fluoropolymer film as a support layer, a sheet-like titanium carbide material is fixed on the support layer, and triazine covalent organic framework fibers are grown on the surface of the sheet-like titanium carbide material; the thickness of the triazine covalent organic framework photocatalytic composite membrane is 200 μm to 500 μm.

[0023] As a general technical concept, the present invention also provides an application of the above-mentioned triazine covalent organic framework photocatalytic composite membrane in a water treatment device.

[0024] In a further improvement to the above application, the water treatment device uses the triazine covalent organic framework photocatalytic composite membrane as both a photocatalyst and a filter membrane.

[0025] In a further improvement to the above application, the water treatment device includes a membrane module; the membrane module includes a lower module, and the lower module is provided with a reaction chamber; the triazine covalent organic framework photocatalytic composite membrane is horizontally laid in the reaction chamber, and the side of the triazine covalent organic framework photocatalytic composite membrane with sheet-like titanium carbide material fixed is facing the light direction.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) In view of the shortcomings of existing COFs membrane materials, such as low bonding strength, poor photocatalytic activity, poor stability, and poor ability to intercept pollutants, which makes it difficult to apply them to the field of water treatment, this invention creatively provides a method for preparing a triazine covalent organic framework photocatalytic composite membrane. First, the fluoropolymer film material and the titanium carbide material are aminated to graft amino groups onto the fluoropolymer film material and the titanium carbide material. Then, the amino-functionalized fluoropolymer film material, the amino-functionalized titanium carbide material, organic monomers, organic solvents, and acid catalysts are mixed and subjected to a condensation reaction. During this reaction, the organic monomers establish strong bonding with the amino-functionalized fluoropolymer film material and the amino-functionalized titanium carbide material through Schiff base reaction and form covalent bonds. At the same time, the organic monomers undergo an imine condensation reaction to form covalent organic framework fibers, thereby enabling the titanium carbide material and the covalent organic framework fibers to be stably fixed on the surface of the fluoropolymer film material and finally forming a dense (few defects) composite membrane with a porous structure. Compared to conventional COF membrane materials, the triazine covalent organic framework photocatalytic composite membrane prepared in this invention uses a fluoropolymer film as a support layer, with a porous powdery solid composed of sheet-like titanium carbide and triazine covalent organic framework fibers fixed on its surface. On one hand, because the fluoropolymer film neither self-degrades under continuous light irradiation nor chemically interacts with reactive oxygen species (ROS), and because it possesses very high strength and remains stable under high temperature, strong acid, and strong alkali conditions, fixing the sheet-like titanium carbide and triazine covalent organic framework fibers onto the fluoropolymer film through covalent bond interactions not only improves the strength and applicability of the photocatalytic composite membrane but also ensures its long-term stability, thus extending its service life. On the other hand, because the fluoropolymer film has micron-sized pores, and the porous powdery solid composed of sheet-like titanium carbide and triazine covalent organic framework fibers has uniform nanoscale pores... Therefore, the photocatalytic composite membrane composed of these materials has a suitable pore structure, achieving a water flux at the nanofiltration level. While possessing a high water flux, it can also effectively retain pollutants and has high mass transfer efficiency, thus improving filtration efficiency and effect. More importantly, the porous powder solid composed of sheet-like titanium carbide and triazine covalent organic framework fibers is a porous material. It can provide more reactive sites, absorb more light sources, and promote the generation of more photogenerated charges by the triazine covalent organic framework fibers, which is beneficial to improving the photocatalytic activity of the photocatalytic composite membrane. Moreover, by uniformly growing the triazine covalent organic framework fibers on the sheet-like titanium carbide, the high electrical conductivity of the sheet-like titanium carbide can also be used to improve the electron transfer capacity, thereby promoting the rapid separation and transfer of photogenerated electrons and holes and generating more active species. These active species can then be used to achieve efficient degradation of pollutants, enabling continuous degradation of pollutants and achieving near-zero emissions.The triazine covalent organic framework photocatalytic composite membrane prepared by this invention has advantages such as high bonding strength, high photocatalytic activity, stable physicochemical properties, strong pollutant interception capacity, simple recovery, and long service life. It is a novel COFs composite membrane material with dual functions of photocatalysis and filtration, which can be widely used in the field of water treatment. It can remain stable under high temperature, strong acid, and strong alkali conditions and can achieve efficient removal of pollutants in water. It has high application value and good application prospects.

[0028] (2) In the preparation method of the present invention, amino-functionalized fluoropolymer film material, organic solvent, 4,4′,4″-(1,3,5-triazine-2,4,6-trimethyl)tribenzaldehyde, acid catalyst, 4,4′,4″-(1,3,5-triazine-2,4,6-trimethyl)triphenylamine and amino-functionalized titanium carbide material are added in sequence. This not only helps to uniformly form a porous powder solid composed of sheet-like titanium carbide and triazine covalent organic framework fiber on the surface of the fluoropolymer film, but also helps to improve the bonding strength between sheet-like titanium carbide, triazine covalent organic framework fiber and fluoropolymer film, thereby obtaining a triazine covalent organic framework photocatalytic composite film with higher photocatalytic activity, better stability, better filtration performance and more ordered structure.

[0029] (3) In the preparation method of the present invention, the initial organic ligand (4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde, 4,4′,4″-(1, The following factors are crucial: the dosage of 3,5-triazine-2,4,6-trimethyltriphenylamine, organic solvent, acid catalyst, condensation reaction temperature and time, the grafting conditions of amino groups in the pretreatment of the fluoropolymer membrane, and the amination treatment conditions and methods of titanium carbide. Slight changes can lead to the inability of the triazine covalent organic framework and titanium carbide to form a strong bond with the fluoropolymer membrane, thus failing to obtain a photocatalytic composite membrane. This is because: the covalent organic framework essentially undergoes a nucleation-growth process, and the nucleation and growth rates need to be precisely controlled during the reaction to obtain high-quality covalent organic framework crystals. In addition, the grafting of amino groups onto the fluoropolymer membrane requires extremely stringent oxygen-free conditions. The dosage of tri-aminopropyltriethoxysilane is a key factor in determining whether a single layer of ordered amino functional groups can be formed on the surface of the fluoropolymer membrane. The etching and amino functionalization reaction conditions of titanium carbide determine whether it will be oxidized to titanium dioxide. Each step is critical, and only by controlling each step can a triazine covalent organic framework photocatalytic composite membrane with high bonding strength and uniform loading be obtained.

[0030] (4) The present invention also provides an application of a triazine covalent organic framework photocatalytic composite membrane in a water treatment device. Using the triazine covalent organic framework photocatalytic composite membrane of the present invention as a photocatalyst and filter membrane in a water treatment device, pollutants in the water can be effectively removed by applying a light source during the filtration process. At the same time, it can continuously degrade pollutants in the water and achieve near-zero discharge, which plays an important role in promoting the efficient treatment of water pollution problems. Attached Figure Description

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0032] Figure 1 The triazine covalent organic framework photocatalytic composite film (2.8 NTCM) and amino-functionalized titanium carbide (NH2-Ti3C2T) prepared in Example 1 of this invention are examples of the photocatalytic composite film prepared in Example 1 of this invention. x SEM images of the triazine covalent organic framework photocatalytic membrane (PCM) prepared in Comparative Example 1, where (a) is NH2-Ti3C2T x (b) is PCM, (c) is 2.8NTCM.

[0033] Figure 2 The triazine covalent organic framework photocatalytic composite film (2.8 NTCM) and amino-functionalized titanium carbide (NH2-Ti3C2T) prepared in Example 1 of this invention are examples of the photocatalytic composite film prepared in Example 1 of this invention. x TEM images of the triazine covalent organic framework photocatalytic membrane (PCM) prepared in Comparative Example 1, where (a) is NH2-Ti3C2T x (b) is PCM, and (c) is 2.8NTCM.

[0034] Figure 3 The triazine covalent organic framework photocatalytic composite film (2.8 NTCM) and amino-functionalized titanium carbide (NH2-Ti3C2T) prepared in Example 1 of this invention are examples of the photocatalytic composite film prepared in Example 1 of this invention. x X-ray diffraction patterns of the triazine covalent organic framework photocatalytic membrane (PCM) prepared in Comparative Example 1.

[0035] Figure 4 The images show the UV-Vis diffuse reflectance of the triazine covalent organic framework photocatalytic composite film (2.8NTCM) prepared in Example 1 of this invention and the triazine covalent organic framework photocatalytic film (PCM) prepared in Comparative Example 1.

[0036] Figure 5 The attached diagram shows the nitrogen adsorption-desorption process and pore size distribution of the triazine covalent organic framework photocatalytic composite membrane (2.8NTCM) prepared in Example 1 of this invention.

[0037] Figure 6 This is a schematic diagram of the water treatment device constructed based on a triazine covalent organic framework photocatalytic composite membrane in Embodiment 2 of the present invention.

[0038] Figure 7 This is a graph showing the degradation effect of different materials on norfloxacin in a single-flow mode in Example 3 of the present invention.

[0039] Figure 8 The graph shows the degradation effect of triazine covalent organic framework photocatalytic composite membranes (1.8 NTCM, 2.8 NTCM, 3 NTCM, 4 NTCM, 5 NTCM, 6 NTCM, 8 NTCM) and triazine covalent organic framework photocatalytic membranes (PCM) on norfloxacin in single-flow mode in Example 3 of the present invention.

[0040] Legend:

[0041] 1. Membrane module; 101. Lower module; 102. Upper module; 103. Reaction chamber; 104. Triazine covalent organic framework photocatalytic composite membrane; 105. Transparent layer; 106. Bolt; 107. Rubber gasket; 108. Inlet; 109. Outlet; 2. Wastewater storage tank; 3. Water pump; 4. Light source. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0043] The materials and instruments used in the following examples are all commercially available.

[0044] Example 1:

[0045] A method for preparing a triazine covalent organic framework photocatalytic composite film includes the following steps:

[0046] (1) Select a circular polytetrafluoroethylene membrane with a diameter of 50 mm, a pore size of 0.1 μm and a thickness of 0.16 mm. Treat the surface with H2O2 (30%): H2SO4 (15 mL: 15 mL) for 20 min at room temperature. Add 40 mL of anhydrous toluene and 4 mL of tri-aminopropyltriethoxysilane to a Pyrex tube and perform three freeze-pump-thaw cycles for degassing. That is, freeze it with liquid nitrogen, then use an oil pump to remove the gas from the frozen mixture, and then introduce nitrogen to thaw it. Repeat this process 3 times. Then, vacuum seal it and heat it at 110 °C for 2 h. After the process is completed, take it out and cool it.

[0047] (2) The reaction product in step (1) was washed twice with ethanol and deionized water (10 mL each time), filtered with a 0.22 μm organic filter membrane, and then dried at 100 °C for 2 h under vacuum to obtain an amino-functionalized polytetrafluoroethylene membrane, denoted as NH2-PTFE.

[0048] (3) Weigh 1.5g of lithium fluoride and add it to a 100mL reactor containing 10mL of hydrochloric acid (37% concentrated hydrochloric acid). Stir for 30min at 35℃ and 500rpm. Weigh 1.5g of titanium aluminum carbide (commercially available, Ti3AlC2T) x Add the solution to the above solution, stir at 35℃ and 500 rpm for 24 h, wash three times with 1M hydrochloric acid solution, wash with deionized water until the pH value of the supernatant is greater than 6, wash twice with anhydrous ethanol, sonicate in an inert atmosphere (high-purity argon) and water for 4 h, centrifuge at 3500 rpm for 1 h, take the supernatant for freeze drying, weigh it, and then perform amino functionalization.

[0049] (4) Weigh the freeze-dried titanium carbide from step (3), mix it with titanium carbide:tri-aminopropyltriethoxysilane:ethanol:deionized water in a ratio of 240 mg:1.6 mL:90 mL:30 mL, stir for 24 h at room temperature and 500 rpm under an inert gas (high-purity argon) atmosphere. After stirring, wash three times with a mixture of ethanol / water (ethanol:water volume ratio of 3:1), wash three times with deionized water, and freeze-dry to obtain amino-functionalized titanium carbide, denoted as NH2-Ti3C2T. x .

[0050] (5) Add 7 mL of 1,4-dioxane, 7 mL of mesitylene, and one sheet of amino-functionalized polytetrafluoroethylene membrane (NH2-PTFE) obtained in step (2) to the reaction vessel in sequence. Weigh 39.3 mg of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylaldehyde and add it to the reaction vessel. Sonicate for 5 min. Add 1.4 mL of acetic acid and sonicate for 5 min. Mix well. Weigh 35.4 mg of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine and add it to the reaction vessel. Sonicate for 5 min and mix well. Add 2.8 mg of amino-functionalized titanium carbide (NH2-Ti3C2T). x The mixture was ultrasonically mixed for 5 minutes to obtain a homogeneous mixture. It was then degassed by argon bubbling for 15 minutes, sealed, and heated to 120°C for a condensation reaction for 72 hours. After the reaction was completed, it was removed and cooled.

[0051] (6) The reaction product in step (5) was washed twice with tetrahydrofuran and acetone (20 mL each time), filtered through a 0.22 μm organic filter membrane, and then dried at 60 °C for 8 h under vacuum to obtain a triazine covalent organic framework photocatalytic composite membrane, denoted as NH2-Ti3C2T x -TFPT-TAPT-COF Membrane, abbreviated as 2.8NTCM.

[0052] In this embodiment, the prepared triazine covalent organic framework photocatalytic composite film uses a fluoropolymer film as a support layer, on which sheet-like titanium carbide material is fixed, and triazine covalent organic framework fibers are grown on the surface of the sheet-like titanium carbide material; the thickness of the triazine covalent organic framework photocatalytic composite film is 350 μm.

[0053] In this invention, titanium carbide (NH2-Ti3C2T) with different amino functionalizations was also investigated. x A triazine covalent organic framework photocatalytic composite film was prepared under the specified dosage conditions, wherein the amino-functionalized titanium carbide (NH2-Ti3C2T) x The dosages were 1.8 mg, 3 mg, 4 mg, 5 mg, 6 mg, and 8 mg in sequence, with other conditions being the same as in Example 1.

[0054] When amino-functionalized titanium carbide (NH2-Ti3C2T) x The dosages were 1.8 mg, 3 mg, 4 mg, 5 mg, 6 mg, and 8 mg, respectively, and the resulting triazine covalent organic framework photocatalytic composite membranes were abbreviated as: 1.8 NTCM, 3 NTCM, 4 NTCM, 5 NTCM, 6 NTCM, and 8 NTCM.

[0055] Comparative Example 1

[0056] A method for preparing a triazine covalent organic framework photocatalytic film is basically the same as that in Example 1, except that amino-functionalized titanium carbide (NH2-Ti3C2T) is not added in Comparative Example 1. x ).

[0057] The triazine covalent organic framework photocatalytic membrane prepared in Comparative Example 1 is denoted as TFPT-TAPT-COF Membrane, or PCM for short.

[0058] Figure 1 The triazine covalent organic framework photocatalytic composite film (2.8 NTCM) and amino-functionalized titanium carbide (NH2-Ti3C2T) prepared in Example 1 of this invention are examples of the photocatalytic composite film prepared in Example 1 of this invention. x SEM images of the triazine covalent organic framework photocatalytic membrane (PCM) prepared in Comparative Example 1, where (a) is NH2-Ti3C2T x(b) is PCM, (c) is 2.8 NTCM. From Figure 1 It is known that the triazine covalent organic framework photocatalytic composite film (2.8 NTCM) of this invention has a typical fibrous network structure, while the amino-functionalized titanium carbide (NH2-Ti3C2T) x The triazine covalent organic framework photocatalytic composite film (2.8 NTCm) exhibits a sheet-like morphology, while the COF fiber-like structure shows regular growth on the sheet-like aminated titanium carbide (NH2-Ti3C2T). x superior.

[0059] Figure 2 The triazine covalent organic framework photocatalytic composite film (2.8 NTCM) and amino-functionalized titanium carbide (NH2-Ti3C2T) prepared in Example 1 of this invention are examples of the photocatalytic composite film prepared in Example 1 of this invention. x TEM images of the triazine covalent organic framework photocatalytic membrane (PCM) prepared in Comparative Example 1, where (a) is NH2-Ti3C2T x (b) is PCM, and (c) is 2.8 NTCM. From Figure 2 It can be seen that the triazine covalent organic framework photocatalytic membrane (PCM) exhibits a regular hexagonal structure along the c-axis; while the amino-functionalized NH2-Ti3C2T x It is coupled to COF by forming an imine bond.

[0060] Figure 3 The triazine covalent organic framework photocatalytic composite film (2.8 NTCM) and amino-functionalized titanium carbide (NH2-Ti3C2T) prepared in Example 1 of this invention are examples of the photocatalytic composite film prepared in Example 1 of this invention. x X-ray diffraction patterns of the triazine covalent organic framework photocatalytic membrane (PCM) prepared in Comparative Example 1. Figure 3 It can be seen that both the triazine covalent organic framework photocatalytic composite film (2.8NTCM) and the triazine covalent organic framework photocatalytic film (PCM) contain the characteristic peak (100) of the covalent organic framework, which is consistent with the crystal structure of COFs materials. This indicates that the main body of both materials is a covalent organic framework, and the addition of amino-functionalized titanium carbide does not affect the long-range ordered structure of the triazine covalent organic framework photocatalytic film.

[0061] Figure 4 The images show the UV-Vis diffuse reflectance of the triazine covalent organic framework photocatalytic composite film (2.8NTCM) prepared in Example 1 of this invention and the triazine covalent organic framework photocatalytic film (PCM) prepared in Comparative Example 1. Figure 4It is known that, compared with the triazine covalent organic framework photocatalytic membrane (PCM), the triazine covalent organic framework photocatalytic composite membrane (2.8NTCM) of the present invention has a strong absorption capacity in the visible light range. In other words, by introducing titanium carbide, the photocatalytic performance and light energy utilization of the photocatalyst under visible light can be improved, and it has a suitable band gap.

[0062] Figure 5 The attached diagram shows the nitrogen adsorption-desorption process and pore size distribution of the triazine covalent organic framework photocatalytic composite membrane (2.8 NTCM) prepared in Example 1 of this invention. Figure 5 It is known that the pore size of the triazine covalent organic framework photocatalytic composite membrane (2.8 NTCM) is 2.145 nm. Analytical calculations show that the specific surface area of ​​the triazine covalent organic framework photocatalytic composite membrane (2.8 NTCM) is 716.1001 m². 2 g 1 The pore volume is 0.384 cm³. 3 g -1 As can be seen, the triazine covalent organic framework photocatalytic composite membrane (2.8 NTCM) of this invention has a large specific surface area. A large specific surface area is beneficial for increasing the contact area between the photocatalyst and pollutants, and for increasing the reaction sites and adsorption sites. Furthermore, the triazine covalent organic framework photocatalytic composite membrane (2.8 NTCM) can also achieve a large water flux, with a water flux of 58.95 L·m at 0.02 MPa. -2 ·h -1 .

[0063] Example 2

[0064] The application of a triazine covalent organic framework photocatalytic composite membrane in a water treatment device is specifically described in that the triazine covalent organic framework photocatalytic composite membrane prepared in Example 1 is used as a photocatalyst and a filter membrane to construct a water treatment device.

[0065] like Figure 6As shown, in this embodiment, the water treatment device includes a membrane module 1, which includes a lower module 101 and an upper module 102. The lower module 101 has a reaction chamber 103. A triazine covalent organic framework photocatalytic composite membrane 104 is horizontally laid at the bottom of the reaction chamber 103, with the side of the triazine covalent organic framework photocatalytic composite membrane 104 with sheet-like titanium carbide material facing the light direction. A light-transmitting layer 105 is located between the lower module 101 and the upper module 102, wherein the lower module 101 and the upper module 102 are fixed by bolts 106. Together, a sealed reaction chamber 103 is formed between the lower module 101 and the upper module 102; a rubber gasket 107 is provided between the upper module 102 and the light-transmitting layer 105, located around the light-transmitting layer 105; a rubber gasket 107 is provided between the triazine covalent organic framework photocatalytic composite membrane 104 and the light-transmitting layer 105, located around the triazine covalent organic framework photocatalytic composite membrane 104, the light-transmitting layer being quartz glass; a water inlet 108 is provided on the upper module 102, and a water outlet 109 is provided on the lower module 101.

[0066] like Figure 6 As shown, in this embodiment, the water treatment device also includes a wastewater storage tank 2, which is connected to the inlet 108 of the membrane module 1 via a pipe, and a water pump 3 is provided on the pipe between the wastewater storage tank 2 and the inlet 108.

[0067] like Figure 6 As shown, in this embodiment, the water treatment device further includes a light source 4, which is disposed above the light-transmitting layer 105 and is used to provide illumination to the triazine covalent organic framework photocatalytic composite membrane 104. Specifically, in this embodiment, the light source is a xenon lamp.

[0068] In this embodiment, the membrane module 1 is made of 316 stainless steel, and the light-transmitting layer is quartz glass, allowing light to be transmitted to the triazine covalent organic framework photocatalytic composite membrane 104 (the membrane has an area of ​​19.63 cm²). 2 The area of ​​) is 7.06 cm². 2A xenon lamp is placed directly above the quartz window. The device operates in dead-end filtration mode with single-flow capability. Flow rate and membrane pressure are controlled by a water pump, and pressure is displayed on a pressure gauge. The liquid before passing through the membrane is the feed solution, and the liquid after passing through the membrane is the permeate. Fresh solution is continuously introduced at every moment of the experiment. The solution remaining after the photodegradation experiment is not reused. The collected permeate sample is directly collected in a 2 mL bottle and refrigerated before ultra-high performance liquid chromatography (UHPLC) analysis. The remaining permeate is collected on a balance to check the flow rate throughout the experiment. The experimental procedure is as follows: air is purged from the system, and the system is filled with feed solution as a preparation step for each experiment. Adsorption occurs in the dark, followed by degradation under xenon lamp illumination. The conditions for pollutant degradation are continuously optimized by selecting operating parameters during operation.

[0069] Example 3

[0070] The removal efficiency of the triazine covalent organic framework photocatalytic composite membrane for organic pollutants in water was investigated. Specifically, the triazine covalent organic framework photocatalytic composite membrane prepared in Example 1 was used to degrade norfloxacin wastewater, including the following steps:

[0071] (1) Triazine covalent organic framework photocatalytic composite membranes (1.8 NTCM, 2.8 NTCM, 3 NTCM, 4 NTCM, 5 NTCM, 6 NTCM, 8 NTCM) were respectively fixed on such... Figure 6 The water treatment apparatus shown, but not limited to, is as follows: Figure 6 In the apparatus shown, other water treatment devices can also be used to immobilize triazine covalent organic framework photocatalytic composite membranes and to treat wastewater.

[0072] (2) Add 1L of norfloxacin solution with a concentration of 5mg / L to wastewater storage tank 2. Feed 100mL at a flow rate of 3mL / min without light to reach adsorption equilibrium. Then change the flow rate to 1mL / min and turn on the light source at the same time. Under simulated sunlight (70 mW / cm²), 2 The solution of norfloxacin was photocatalytically reacted and filtered by a triazine covalent organic framework photocatalytic composite membrane under irradiation. The continuous feed was 400 mL, and the total feed was 500 mL, which completed the degradation of norfloxacin in the water.

[0073] Control group 1: Untreated polytetrafluoroethylene membrane was used directly as the filter membrane, and other conditions were the same.

[0074] Control group 2: The triazine covalent organic framework photocatalytic membrane was replaced with a triazine covalent organic framework photocatalytic composite membrane, with other conditions being the same.

[0075] The liquid before passing through the membrane is the feed liquid, and the liquid after passing through the membrane is the permeate. Two mL of permeate was collected at different flow rates (0, 20, 40, 60, 100, 108, 123, 158, 174, 200, 220, 248, 274, 300, 320, 340, 374, 400, 425, 450, 475, and 500 mL). The samples were filtered through a 0.22 μm filter, and the absorbance of the filtrate was measured by liquid chromatography to determine the concentration of norfloxacin after adsorption and illumination, thus obtaining different concentrations of NH₂-Ti₃C₂T₂. x The adsorption and photocatalytic degradation effects of the triazine covalent organic framework photocatalytic composite membrane on norfloxacin were studied. The degradation effect was evaluated by the amount and rate of pollutant removal. The results are as follows: Figure 7 and Figure 8 As shown.

[0076] Figure 7 This is a graph showing the degradation effect of different materials on norfloxacin in a single-flow mode in Example 3 of the present invention. Figure 8 This image shows the degradation effect of triazine covalent organic framework photocatalytic composite membranes (1.8 NTCM, 2.8 NTCM, 3 NTCM, 4 NTCM, 5 NTCM, 6 NTCM, 8 NTCM) and triazine covalent organic framework photocatalytic membranes (PCM) on norfloxacin in a single-flow mode, as described in Example 3 of this invention. Figure 7 and Figure 8 It can be seen that after passing through 100 mL to reach the adsorption equilibrium of the dark reaction and then passing through 400 mL under light conditions, the loadings of NH2-Ti3C2T were 1.8 mg, 2.8 mg, 3 mg, 4 mg, 5 mg, 6 mg, and 8 mg. x The removal rates of norfloxacin by the triazine covalent organic framework photocatalytic composite membrane (NTCM) were 84.4%, 95.2%, 72.4%, 59.8%, 74.1%, 74.8%, and 58.3%, respectively. In addition, the removal rate of norfloxacin by the triazine covalent organic framework photocatalytic membrane (PCM) was 57.3%. It is evident that, compared to the unsupported NH2-Ti3C2T... x The triazine covalent organic framework photocatalytic membrane (PCM) of this invention, by loading titanium carbide, can significantly improve the removal efficiency of organic pollutants in water. In particular, the loading of 2.8 mg NH2-Ti3C2T... x The triazine covalent organic framework photocatalytic composite membrane (2.8 NTCM) exhibits better photocatalytic activity, indicating that the triazine covalent organic framework photocatalytic composite membrane of the present invention has the strongest electron transfer capability and the best photocatalytic degradation effect.

[0077] As can be seen from the above results, the triazine covalent organic framework photocatalytic composite membrane prepared by this invention has the advantages of high bonding strength, high photocatalytic activity, stable physicochemical properties, strong pollutant interception capacity, simple recovery, and long service life. It is a novel COFs composite membrane material with dual functions of photocatalysis and filtration, which can be widely used in the field of water treatment. It can remain stable under high temperature, strong acid, and strong alkali conditions and can achieve efficient removal of pollutants in water. It has high application value and good application prospects.

[0078] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a triazine covalent organic framework photocatalytic composite film, characterized in that, Includes the following steps: S1. Amination treatment is performed on fluoropolymer film material and titanium carbide material respectively to obtain amino-functionalized fluoropolymer film material and amino-functionalized titanium carbide material. S2. The amino-functionalized fluoropolymer film material, amino-functionalized titanium carbide material, organic monomer, organic solvent, and acid catalyst obtained in step S1 are mixed and subjected to a condensation reaction at 120°C for 72 hours to obtain a triazine covalent organic framework photocatalytic composite film; the organic monomer is 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine; the mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde to 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine is 39.3∶35.4; the mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine to triphenylamine is 39.3∶35.

4. The mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triaryl)benzaldehyde to amino-functionalized titanium carbide material is 39.3:0-8, but the amount of amino-functionalized titanium carbide material is not 0; the ratio of the organic solvent, acid catalyst, and 4,4′,4″-(1,3,5-triazine-2,4,6-triaryl)benzaldehyde is 14 mL:1.4 mL:39.3 mg. Amination treatment of fluoropolymer materials includes the following steps: (a1) A mixed solution A is used to treat the surface of a fluoropolymer film material; the mixed solution A is obtained by mixing hydrogen peroxide and sulfuric acid; the volume ratio of hydrogen peroxide to sulfuric acid in the mixed solution A is 1:1; the mass fraction of hydrogen peroxide is 30%; the fluoropolymer film material is a polytetrafluoroethylene film or a polyvinylidene fluoride film; the pore size of the fluoropolymer film material is 0.1 μm to 0.22 μm; the surface treatment time is 20 min. (a2) The surface-treated fluoropolymer film material and mixed solution B are mixed and subjected to freeze-pump-thaw cycle degassing; the mixed solution B is obtained by mixing toluene and tri-aminopropyltriethoxysilane; the volume ratio of toluene and tri-aminopropyltriethoxysilane in the mixed solution B is 10:1; the freeze-pump-thaw cycle degassing is performed 3 times; (a3) The fluoropolymer film material after being degassed by the freezing-pumping-thawing cycle is heated to 110°C to carry out an amination reaction to obtain an amino-functionalized fluoropolymer film material; the amination reaction time is 2 hours. The amination treatment of titanium carbide material includes the following steps: mixing titanium carbide material and mixed solution C, stirring, washing, and freeze-drying to obtain amino-functionalized titanium carbide material; wherein mixed solution C is obtained by mixing tri-aminopropyltriethoxysilane, ethanol, and water; and wherein the ratio of titanium carbide material, tri-aminopropyltriethoxysilane, ethanol, and water is 240 mg: 1.6 mL: 90 mL:

30. mL; During the amination treatment of the titanium carbide material, the stirring is carried out under an inert atmosphere for 24 hours, and the washing solution used in the washing process is an ethanol / water mixture; the volume ratio of ethanol to water in the ethanol / water mixture is 3:1; The titanium carbide material is prepared by the following method: placing titanium aluminum carbide in a hydrochloric acid / lithium fluoride mixture, stirring at 500 rpm to 600 rpm for 24 hours, washing, sonicating, centrifuging, and freeze-drying to obtain the titanium carbide material; The hydrochloric acid / lithium fluoride mixture is prepared by the following method: mixing lithium fluoride and hydrochloric acid, stirring at 500 rpm to 600 rpm for 30 minutes to obtain the hydrochloric acid / lithium fluoride mixture; the ratio of lithium fluoride to hydrochloric acid is 1.5 g: 10 mL.

2. The production method according to claim 1, characterized by, The mass ratio of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde to amino-functionalized titanium carbide material is 39.3:1 to 3; the organic solvent is a mixture of 1,4-dioxane and mesitylene; the volume ratio of 1,4-dioxane and mesitylene in the mixture of 1,4-dioxane and mesitylene is 1:1; the acid catalyst is an acetic acid solution; the concentration of the acetic acid solution is 3M.

3. The preparation method according to claim 1, characterized in that, Step S2 is as follows: S2-1. Mix amino-functionalized fluoropolymer film material, organic solvent, and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde, sonicate for 5 min, add acid catalyst, sonicate for 5 min, add 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine, sonicate for 5 min, add amino-functionalized titanium carbide material, sonicate for 5 min, and obtain a mixture; S2-2. Argon gas is bubbled through the mixture for 10-15 minutes to degas it. The mixture is then heated to carry out a condensation reaction. After washing, filtering, and drying, a triazine covalent organic framework photocatalytic composite membrane is obtained.

4. A triazine covalent organic framework photocatalytic composite membrane prepared by any one of claims 1 to 3, characterized in that, The triazine covalent organic framework photocatalytic composite membrane uses a fluoropolymer film as a support layer, on which sheet-like titanium carbide material is fixed, and triazine covalent organic framework fibers are grown on the surface of the sheet-like titanium carbide material; the thickness of the triazine covalent organic framework photocatalytic composite membrane is 200 μm to 500 μm.

5. The application of the triazine covalent organic framework photocatalytic composite membrane as described in claim 4 in a water treatment device.

6. The application according to claim 5, characterized in that, The water treatment device uses the triazine covalent organic framework photocatalytic composite membrane as both a photocatalyst and a filter membrane.

7. The application according to claim 6, characterized in that, The water treatment device includes a membrane module; the membrane module includes a lower module, and the lower module is provided with a reaction chamber; the triazine covalent organic framework photocatalytic composite membrane is horizontally laid in the reaction chamber, and the side of the triazine covalent organic framework photocatalytic composite membrane with sheet-like titanium carbide material fixed is facing the light direction.

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