A method for preparing N3-Cu-O1@COF photocatalyst and its application

Abstract

This invention discloses a method for preparing N3-Cu-O1@COF photocatalyst and its application. The catalyst uses 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde as reactants, which are polymerized into a highly ordered covalent organic framework precursor through an aldehyde-amine condensation reaction. The prepared covalent organic framework precursor and solutions of different Cu salts are impregnated to obtain a Cu single-atom photocatalyst N3-Cu-O1@COF with a precise N3-Cu-O1 coordination environment. This invention prepares a single-atom Cu photocatalyst through a two-step solvothermal and impregnation method. The active single-atom Cu sites in the obtained photocatalyst have a well-defined N3-Cu-O1 coordination microenvironment, which can optimize the electron distribution around Cu and promote the separation and transfer of photogenerated carriers. The Cu atoms at the single-atom sites of the photocatalyst are uniformly fixed on the one-dimensional pore walls of the covalent organic framework, which can promote sufficient contact between the catalyst and pollutant molecules in the water and improve the efficiency of photocatalytic pollutant degradation.

Description

Technical Field

[0001] This invention relates to a method for preparing N3-Cu-O1@COF photocatalyst and its application, specifically to a method for preparing a single-atom photocatalyst N3-Cu-O1@COF with a precise N3-Cu-O1 unsaturated coordination environment and its application in the degradation of tetracycline in water, belonging to the field of catalyst preparation and application technology. Background Art

[0002] The unregulated production and use of antibiotics have caused serious water pollution problems. With increasing public awareness of environmental protection and stricter regulations, developing efficient and green methods for removing trace antibiotics from water is imperative. Driven by the goal of "pollution reduction and carbon reduction," photocatalysis has shown great potential for pollutant removal. Currently, many Cu-based supported semiconductor materials are being used in photocatalytic water pollutant degradation research; however, they generally face problems such as uneven surface active components and difficulty in determining their binding mechanisms, leading to difficulties in controlling catalyst performance through microenvironment and unclear mechanisms. For example, Huang et al. (Environ. Sci. Technol. 2023, 57, 9096−9104) reported that while traditional methods for preparing supported semiconductor catalysts (such as coating and impregnation) can easily achieve high loading of active components, the active components tend to aggregate into clumps during catalyst preparation, and the binders used in the preparation process can coat the active components, hindering their contact with reactants, thus leading to a series of problems such as low catalytic activity and unclear catalytic mechanisms. Zhang et al. (Nature Communications, 2024, 15, 537) reported that heterojunctions have attracted attention in recent years due to their ability to rapidly separate photogenerated electrons and holes; however, their limited contact area of ​​active components and uneven distribution of active sites not only restrict further improvement of photocatalyst performance but also pose difficulties for studying clear structure-activity relationships at the molecular level. Liu et al. (Small, 2023, 19, 2300289) reported that although the synergistic effect of single-atom catalysts (SACs) has been demonstrated, the reaction mechanisms for improving reversible oxygen reduction (ORR) and oxygen evolution reaction (OER) remain unclear, and the precise synthesis and identification of SACs in specific reactions remain ambiguous. Therefore, the precise construction of DACs with high ORR and OER still faces many challenges.

[0003] Compared to traditional inorganic supported semiconductor materials, covalent organic frameworks possess highly designable building blocks, precise molecular structures, and significant crystallinity, making them promising for the precise design of coordination environments for active metal sites. Therefore, leveraging the unique structural advantages of covalent organic frameworks, this study attempts to construct a single-atom metal site catalyst with a precise N3-Cu-O1 unsaturated coordination environment, optimize the electron distribution of the active Cu sites, promote the separation and transfer of photogenerated carriers, and improve the degradation efficiency of tetracycline, a typical antibiotic molecule in the aqueous environment. Summary of the Invention

[0004] This invention aims to provide an N3-Cu-O1@COF photocatalyst and apply it to the removal of tetracycline pollutants in aquatic environments. By precisely designing a covalent organic framework substrate structure and coordinating the introduction of Cu active single-atom sites, a single-atom photocatalyst with a precise N3-Cu-O1 coordination microenvironment is prepared for the efficient removal of antibiotic pollutants in aquatic environments.

[0005] This invention selects 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde as monomers to precisely construct N / O chelate sites in the framework. With the help of the strong binding force of N / O to Cu, the precise coordination of Cu atoms on the covalent organic framework substrate can be achieved.

[0006] The Cu single-atom covalent organic framework photocatalyst provided by this invention uses 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde as reactants, and polymerizes them into a highly ordered covalent organic framework precursor through an aldehyde-amine condensation reaction. The prepared covalent organic framework precursor and solutions of different Cu salts are impregnated to obtain a Cu single-atom photocatalyst N3-Cu-O1@COF with a precise N3-Cu-O1 coordination environment.

[0007] This invention provides a method for preparing the above-mentioned N3-Cu-O1@COF photocatalyst, the specific steps of which are as follows:

[0008] (1) Add 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and acid in a volume ratio of 3~5:3~5:1.

[0009] (2) Use a common oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 100~120 ℃ for 3~5 days.

[0010] (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder.

[0011] (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor.

[0012] (5) Weigh out Cu salt and place it in a beaker, add DMF, and disperse it by sonication to form a Cu salt solution for later use;

[0013] (6) Weigh out the COF precursor and Cu salt solution, and stir the reaction under argon protection for 24 hours with a magnetic stirrer.

[0014] (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder.

[0015] (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF.

[0016] The molecular structural formula of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine described in this invention is as follows:

[0017]

[0018] The polyaldehyde-substituted functional monomers described in this invention are functional monomers with the following structural formulas:

[0019]

[0020] In the above preparation method, the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde is 1:1~2.

[0021] The acid solution described in this invention is one of 3 M-6 M acetic acid or 0.01 M-0.02 M trifluoromethanesulfonic acid.

[0022] The Cu salt solution system described in this invention is one of Cu(OAc)2 / DMF (10~50 mg / 50 mL) or CuCl2 / DMF (10~50 mg / 50 mL) solution, with a solution concentration of 0.2~1 g / L.

[0023] The mass ratio of the COF precursor to the copper salt in this invention is 1:0.5~2.

[0024] This invention provides the application of the N3-Cu-O1@COF photocatalyst obtained by the above preparation method in the degradation of tetracycline in water.

[0025] In the above application, the photocatalytic degradation behavior of tetracycline molecules by the photocatalyst was evaluated by monitoring the residual tetracycline concentration in the catalytic reaction system at specific time points using a UV-Vis spectrophotometer. Specifically, 5 mg of catalyst was ultrasonically dispersed in 10 mL of a 10 mg / L aqueous solution of tetracycline molecules. A 300 W xenon lamp with a wavelength cutoff filter (λ ≥ 420 nm) was used as the light source. Before light radiation, the suspension was stirred in the dark for 1 h to allow adsorption saturation between the catalyst and tetracycline molecules. Then, the xenon lamp was turned on, and the photocatalytic reaction process began. During the degradation process, small amounts of the suspension were taken out at time intervals and immediately filtered through a Millipore filter to remove the catalyst. The residual concentration of erythromycin molecules in the reaction system was analyzed using a UV-Vis spectrophotometer.

[0026] The beneficial effects of this invention are:

[0027] (1) The present invention prepares a single-atom Cu photocatalyst by a two-step method of solvothermal and impregnation. The operation is simple, the method is controllable and easy to repeat, and it is an effective method for simple and rapid preparation of single-atom catalysts.

[0028] (2) The active single-atom site Cu in the photocatalyst prepared by the present invention has a clear N3-Cu-O1 coordination microenvironment, which can optimize the electron distribution around Cu and promote the separation and transfer of photogenerated carriers;

[0029] (3) The Cu atoms at the single-atom sites of the photocatalyst prepared by the present invention are uniformly fixed on the one-dimensional pore walls of the covalent organic framework, which can promote the full contact between the catalyst and pollutant molecules in the water and improve the photocatalytic degradation efficiency of pollutants. Attached Figure Description

[0030] Figure 1 The infrared spectrum of Example 1;

[0031] Figure 2 The ultraviolet spectrum of Example 2;

[0032] Figure 3 This is a bandgap location diagram for Example 3;

[0033] Figure 4 The photocurrent diagram is shown in Example 3.

[0034] Figure 5 The scan and transmission images are from Example 4;

[0035] Figure 6 This is a synchrotron radiation diagram of Example 4;

[0036] Figure 7 The XRD pattern is shown in Example 5.

[0037] Figure 8 The image shows the liquid UV spectrum of the TC solution in Example 6;

[0038] Figure 9 The graph shows the photocatalytic degradation performance of Example 6;

[0039] Figure 10 This is a schematic diagram illustrating the synthesis principle of the present invention. Detailed Implementation

[0040] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments.

[0041] Example 1: COF:CuCl2 (wt%) = 2:1, acid solution used was 6 M acetic acid.

[0042] (1) Add 0.03 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.03 mmol of 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and 6M acetic acid in a volume ratio of 5:5:1 to a total volume of 2.2 mL.

[0043] (2) Use a common oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 120 ℃ and let it stand for 3 days.

[0044] (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder.

[0045] (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor.

[0046] (5) Weigh 2.5 mg of CuCl2 and place it in a beaker. Add 10 mL of DMF and disperse by sonication. Set aside for later use.

[0047] (6) Weigh 5 mg of COF precursor and add it to the above Cu salt solution. Under argon protection, stir the mixture with a magnetic stirrer for 1 day.

[0048] (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder.

[0049] (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF(0.5).

[0050] The material obtained in (8) was subjected to infrared characterization analysis, and its spectrum is shown in the attached figure. Figure 1 As shown, the results indicate that N3-Cu-O1@COF(0.5) generates a C=N stretching vibration band (1605 cm⁻¹). -1 However, the N-H vibration peak of TTA (3319 cm⁻¹) -1 The C-O characteristic peak of DHTA (1709 cm⁻¹) and DHTA -1 The disappearance of the α-amine condensation reaction confirms the successful execution of the aldehyde-amine condensation reaction in the preparation of the covalent organic framework.

[0051] Example 2: COF:CuCl2 (wt%) = 1:1, acid solution used was 6 M acetic acid.

[0052] (1) Add 0.03 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.03 mmol of 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and 6M acetic acid in a volume ratio of 5:5:1 to a total volume of 2.2 mL.

[0053] (2) Use a common oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 120 ℃ and let it stand for 3 days.

[0054] (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder.

[0055] (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor.

[0056] (5) Weigh 5 mg of CuCl2 and place it in a beaker. Add 10 mL of DMF and disperse by sonication. Set aside for later use.

[0057] (6) Weigh 5 mg of COF precursor and add it to the above Cu salt solution. Under argon protection, stir the mixture with a magnetic stirrer for 1 day.

[0058] (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder.

[0059] (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF(1).

[0060] The material obtained in (8) was characterized by ultraviolet absorption spectroscopy, and its spectrum is shown in the attached figure. Figure 2 As shown, the prepared N3-Cu-O1@COF(1) photocatalyst has a wide range of visible light absorption in the wavelength range of 200-800 nm.

[0061] Example 3: COF:CuCl2 (wt%) = 1:2, acid solution used was 6 M

[0062] (1) Add 0.03 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.03 mmol of 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and 6M acetic acid in a volume ratio of 5:5:1 to a total volume of 2.2 mL.

[0063] (2) Use a common oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 120 ℃ and let it stand for 3 days.

[0064] (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder.

[0065] (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor.

[0066] (5) Weigh 5 mg of CuCl2 and place it in a beaker. Add 10 mL of DMF and disperse by sonication. Set aside for later use.

[0067] (6) Weigh 2.5 mg of COF precursor and add it to the above Cu salt solution. Under argon protection, stir the mixture with a magnetic stirrer for 1 day.

[0068] (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder.

[0069] (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF(2).

[0070] The band gap position of the material obtained in (8) was analyzed, and its spectrum is shown in the attached figure. Figure 3As shown in the spectrum, the conduction band position is more negative than that of the 1e (+0.33 V vs. NHE) redox reaction pathway, indicating that the band position of the prepared material can drive the generation of free radicals with strong oxidizing power.

[0071] The material obtained in (8) was characterized by photocurrent analysis, and its spectrum is shown in the attached figure. Figure 4 As shown, N3-Cu-O1@COF(2) has a high photocurrent density, indicating that it has efficient photocurrent conversion capability and charge separation efficiency.

[0072] Example 4: COF:Cu(OAc)2 (wt%) = 1:2, acid solution used was 3 M acetic acid.

[0073] (1) Add 0.03 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.03 mmol of 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and 3 M acetic acid in a volume ratio of 5:5:1 to a total volume of 2.2 mL.

[0074] (2) Use a common oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 120 ℃ and let it stand for 3 days.

[0075] (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder.

[0076] (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor.

[0077] (5) Weigh 5 mg of Cu(OAc)2 and place it in a beaker. Add 10 mL of DMF, disperse by sonication, and set aside for later use.

[0078] (6) Weigh 2.5 mg of COF precursor and add it to the above Cu salt solution. Under argon protection, stir the mixture with a magnetic stirrer for 1 day.

[0079] (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder.

[0080] (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF(3).

[0081] The morphology of the material obtained in (8) was analyzed by scanning (a) and transmission characterization (b), and its spectrum is shown in the attached figure. Figure 5 As shown, N3-Cu-O1@COF(3) exhibits a uniform nanowire structure. Isolated Cu atomic sites distributed on the COF matrix (marked with red circles) can be easily observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) at atomic resolution.

[0082] Synchrotron radiation characterization analysis of the material obtained in (8) is shown in the attached spectrum. Figure 6 As shown, in the X-ray absorption near-edge structure (XANES) spectrum, the binding energy of N3-Cu-O1@COF(3) is higher than that of Cu, but lower than that of CuO. N is less electronegative than O, therefore N3-Cu-O1@COF(3) represents an intermediate binding energy that coordinates with both N and O.

[0083] Example 5: COF:Cu(OAc)2 (wt%) = 1:2, the acid solution used is 0.01 M trifluoromethanesulfonic acid.

[0084] (1) Add 0.03 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 0.03 mmol of 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and 0.01 M trifluoromethanesulfonic acid in a volume ratio of 5:5:1 to a total volume of 2.2 mL.

[0085] (2) Use a common oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 120 ℃ and let it stand for 3 days.

[0086] (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder.

[0087] (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor.

[0088] (5) Weigh 5 mg of Cu(OAc)2 and place it in a beaker. Add 10 mL of DMF, disperse by sonication, and set aside for later use.

[0089] (6) Weigh 2.5 mg of COF precursor and add it to the above Cu salt solution. Under argon protection, stir the mixture with a magnetic stirrer for 1 day.

[0090] (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder.

[0091] (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF (4).

[0092] The XRD characterization analysis of the material obtained in (8) is shown in the attached spectrum. Figure 7 As shown. The results show that a strong diffraction peak appears near 2θ=1.1º (100 crystal plane) while no impurity peaks appear, indicating that the prepared N3-Cu-O1@COF(4) material has good crystallinity. This also indicates that the material has a regular and ordered pore structure, which is conducive to the transport of photocharge and can improve the photocatalytic activity of the material.

[0093] Example 6: Photoelectric properties of the catalyst and its efficiency in degrading tetracycline

[0094] Five mg of the photocatalyst prepared in Example 3 was ultrasonically dispersed in 10 mL of a 10 mg / L tetracycline aqueous solution. A 300 W xenon lamp with a wavelength cutoff filter (λ ≥ 420 nm) was used as the light source. Before light radiation, the suspension was stirred in the dark for 1 hour to allow adsorption saturation between the catalyst and tetracycline molecules. Then, the xenon lamp was turned on, and the photocatalytic reaction began. During the degradation process, small amounts of the suspension were taken out at time intervals and immediately filtered through a Millipore filter to remove the catalyst. The residual concentration of erythromycin molecules in the reaction system was analyzed using a UV-Vis spectrophotometer.

[0095] from Figure 8 It can be seen that TC exhibits typical absorption peaks at approximately 275 nm and 364 nm. Before photocatalytic testing, the sample adsorbed TC under dark conditions for 60 minutes until it reached a stable state. Under light irradiation, N3-Cu-O1@COF(2) achieved a 98% degradation efficiency of tetracycline in water within 30 minutes; Figure 9 As shown.

[0096] Figure 10 The following is a schematic diagram illustrating the synthesis principle of this invention (using CuCl2 as an example). A two-step method was employed to synthesize single-atom copper catalysts with different coordination microenvironments. First, a highly ordered covalent organic framework precursor was polymerized via an aldehyde-amine condensation reaction. Subsequently, the prepared covalent organic framework precursor and a CuCl2 / DMF solution system were impregnated to obtain a Cu single-atom photocatalyst N3-Cu-O1@COF with a precise N3-Cu-O1 coordination environment. Because the N sites on the imine bonds and the hydroxyl groups on the DHTA in the covalent organic framework precursor can chelate with copper ions to form a stable coordination structure, Cu atoms are uniformly fixed on the one-dimensional pore walls of the covalent organic framework.

Claims

1. A method for preparing an N3-Cu-O1@COF photocatalyst, characterized in that: Using 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde as reactants, they were polymerized into a highly ordered covalent organic framework precursor via an aldehyde-amine condensation reaction. The prepared covalent organic framework precursor and solutions of different Cu salts were impregnated to obtain a Cu single-atom photocatalyst N3-Cu-O1@COF with a precise N3-Cu-O1 coordination environment. The specific steps for preparing the N3-Cu-O1@COF photocatalyst are as follows: (1) Add 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde to a heat-resistant glass tube; then add a mixed solution of 1,4-dioxane, mesitylene and acid in a volume ratio of 3~5:3~5:

1. (2) Use an oil pump to remove air from the reaction system, seal it, and put the glass tube into an oven at 100~120 ℃ for 3~5 days. (3) After the glass tube is removed and cooled to room temperature, the product is removed, filtered, washed with acetone, and dried to obtain a solid powder. (4) Then place it in a Soxhlet extraction apparatus and heat it to 100 °C. When the extraction solution is colorless and transparent, take out the product and dry it in a vacuum oven at 100 °C to obtain the COF precursor. (5) Weigh out Cu salt and place it in a beaker, add DMF, and disperse it by sonication to form a Cu salt solution for later use; (6) Weigh the COF precursor and Cu salt solution, and stir the reaction under argon protection with a magnetic stirrer for 24 hours; the mass ratio of the COF precursor to Cu salt is 1:0.5~2. (7) Take out the product, filter it, wash it repeatedly with deionized water, and dry it to obtain a solid powder. (8) The washed and filtered product was placed in a petri dish and dried in a vacuum drying oven at 60 °C for 12 h to obtain N3-Cu-O1@COF.

2. The preparation method of the N3-Cu-O1@COF photocatalyst according to claim 1, characterized in that: The molecular structural formula of the 2,4,6-tris(4-aminophenyl)-1,3,5-triazine is as follows: ； The structural formula of the 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde is as follows: 。 3. The preparation method of the N3-Cu-O1@COF photocatalyst according to claim 1, characterized in that: The molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 3,3'-dihydroxy-[1,1'-biphenyl]-4,4'-dicarboxaldehyde is 1:1~2.

4. The preparation method of the N3-Cu-O1@COF photocatalyst according to claim 1, characterized in that: In step (1), the acid solution is one of 3 M-6 M acetic acid or 0.01 M-0.02 M trifluoromethanesulfonic acid.

5. The preparation method of the N3-Cu-O1@COF photocatalyst according to claim 1, characterized in that: In step (5), the Cu salt solution system is either Cu(OAc)2 / DMF or CuCl2 / DMF solution, and the solution concentration is 0.2~1g / L.

6. The application of the N3-Cu-O1@COF photocatalyst prepared by any one of claims 1 to 5 in the degradation of tetracycline in water.

7. The application according to claim 6, characterized in that... The specific method is as follows: 5 mg of catalyst is ultrasonically dispersed into 10 mL of 10 mg / L tetracycline molecule aqueous solution; a 300 W xenon lamp with a wavelength cutoff filter is used as the light source; before light radiation, the suspension is stirred in the dark for 1 h to allow the catalyst and tetracycline molecules to reach adsorption saturation; then the xenon lamp is turned on, and the photocatalytic reaction process begins.

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