Copper-doped ionic COF material Cu (at) TVPT-COF, preparation method thereof and application of copper-doped ionic COF material Cu (at) TVPT-COF in electrochemical nitrate reduction

Abstract

The invention relates to a copper-doped ionic COF material Cu (at) TVPT-COF, a preparation method thereof and application of the copper-doped ionic COF material Cu (at) TVPT-COF in electrochemical nitrate reduction. The preparation method comprises the following steps: mixing N, N '-disubstituted-4, 4'-bipyridine cation salt with 2, 4, 6-tri (4-aminophenyl)-1, 3, 5-triazine, carrying out freezing and thawing-circulating degassing, carrying out a reaction, washing, and drying to obtain the TVPT-COF. The preparation method comprises the following steps: dissolving copper sulfate and TVPT-COF in tetrahydrofuran, and reacting in a high-pressure reaction kettle; and centrifuging, collecting the precipitate, washing and drying to obtain the Cu-coated TVPT-COF. The COF material which is convenient to synthesize, stable in structure and good in catalytic performance is obtained. The material is prepared into a reduction electrode. The electrode is used for producing ammonia through electro-catalysis of nitrate reduction, reaches 95.92% of Faraday efficiency under-0.5 V vs.RHE, reaches the highest ammonia nitrogen yield of 202.97 mmol h <-1 > g <-1 >, and has excellent nitrate reduction catalytic activity. The catalyst has a wide application prospect in the field of catalysis.

Description

Technical Field

[0001] The patent of this invention belongs to the field of electrocatalysis, and relates to a copper-doped ionic COF material Cu@TVPT-COF, a preparation method thereof, and an application in electrochemical nitrate reduction. Background Art

[0002] With the increasing severity of global environmental problems, especially the intensification of water pollution, nitrogen oxides (NO x ) and its derivatives have become an important research topic. Nitrate ions (NO3-), as a common water pollutant, usually come from the discharge of agricultural, industrial wastewater and urban sewage. Traditional treatment methods such as biodegradation and chemical reduction often have defects such as low efficiency, high cost and secondary pollution to the environment. Therefore, the development of efficient and green electrochemical methods to reduce nitrate ions has become one of the current research hotspots.

[0003] In recent years, metal-doped organic frameworks (COFs) have gradually attracted widespread attention due to their excellent structural stability, adjustable porosity and good conductivity. COFs materials have a highly ordered pore structure that can provide a large number of reaction sites, thereby improving the efficiency of electrochemical reactions. Among many metals, copper has become the focus of research due to its good catalytic performance and relatively low cost.

[0004] Copper-doped ionic COF materials can effectively promote the electrochemical reduction reaction of nitrate ions. The presence of copper can not only enhance the conductivity of the material, but also promote the reduction process of nitrate through its unique catalytic properties. In addition, the organic framework of the COF material can provide a stable support to prevent the aggregation of metal particles, thereby maintaining good catalytic activity.

[0005] In order to further improve the performance of the electrode, researchers can also use other methods to modify the material. For example, by doping other metal ions or introducing conductive materials (such as carbon nanotubes, graphene, etc.), the conductivity and stability of the electrode can be improved. In addition, adjusting the synthesis conditions (such as reaction temperature, time, solvent, etc.) can also optimize the microstructure of the material, thereby improving its catalytic performance in electrochemical reactions.

[0006] In the application of electrochemical nitrate reduction, copper-doped ionic COF materials have shown good catalytic activity and selectivity. Studies have shown that under appropriate potentials, nitrate ions can be effectively reduced to harmless substances such as nitrogen or ammonia. This process can not only reduce nitrogen pollution in water bodies, but also provide new ideas for the recycling of nitrogen resources.

[0007] In summary, the research on copper-doped ionic COF material electrodes has important theoretical significance and practical application value. By optimizing the preparation method and modification means of the material, its performance in electrochemical nitrate reduction can be further improved, providing an effective solution for water pollution control. Through in-depth research on this electrode, it is expected to achieve efficient removal of nitrates in water bodies and make positive contributions to environmental protection. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a Cu@TVPT-COF electrode with stable structure, simple preparation method, high catalytic efficiency and good selectivity, and its application in electrocatalytic nitrate reduction.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is: a copper-doped ionic COF material Cu@TVPT-COF, with Cu as the central metal atom and the ionic COF material as the matrix to obtain Cu@TVPT-COF.

[0010] The preparation method of the above-mentioned copper-doped ionic COF material Cu@TVPT-COF is as follows:

[0011] 1) Mixing N,N'-disubstituted-4,4'-bipyridinium cationic salt TVN and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine TAPT, dissolving in ethanol / water, reacting after three freeze-thaw-cycle degassing, washing with ethanol and water six times, filtering and drying to obtain ionic COF material TVPT-COF;

[0012] 2) Dissolve copper sulfate and TVPT-COF in tetrahydrofuran (THF), mix and stir evenly, transfer to a high-pressure reactor for reaction, collect the precipitate by centrifugation, wash with ethanol several times, and dry to obtain Cu@TVPT-COF.

[0013] In the above-mentioned method for preparing the copper-doped ionic COF material Cu@TVPT-COF, in step 1), the molar ratio of TAPT and TVN is 5:3, and the volume ratio of ethanol:water is 4:1.

[0014] In the above-mentioned method for preparing the copper-doped ionic COF material Cu@TVPT-COF, in step 1), the reaction is carried out at 120° C. for 72 hours.

[0015] In the above-mentioned method for preparing the copper-doped ionic COF material Cu@TVPT-COF, in step 2), the mass ratio of copper sulfate:TVPT-COF=2:1.

[0016] In the above-mentioned method for preparing the copper-doped ionic COF material Cu@TVPT-COF, in step 2), the reaction conditions are 120° C. for 36 hours.

[0017] A Cu@TVPT-COF electrode is prepared by the following method: the Cu@TVPT-COF, acetylene black, naphthol film solution, isopropanol, and ultrapure water are drop-coated on carbon cloth after ultrasonic treatment and dried to obtain a Cu@TVPT-COF electrode.

[0018] Application of the above-mentioned Cu@TVPT-COF electrode in electrochemical nitrate reduction.

[0019] In the above application, the Cu@TVPT-COF electrode is used as the working electrode, the counter electrode is a platinum electrode, the reference electrode is an Ag / AgCl reference electrode, and the cathode electrolyte and the anode electrolyte are both 0.1M KNO3 solution and 1M KOH solution.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention uses simple, green and readily available raw materials to synthesize Cu@TVPT-COF through a simple hydrothermal method. The mixed ink is loaded on the carbon cloth, and the obtained material has a stable structure and simple synthesis operation.

[0022] 2. The catalyst synthesized by the present invention is used for electrocatalytic nitrate reduction, achieving a Faradaic efficiency of 95.92% at -0.5 V vs. RHE and a maximum of 202.97 mmol h -1 g -1 Ammonia nitrogen yield.

[0023] 3. The raw materials used in the present invention are simple and easy to obtain, the operation steps are simple and feasible, the material exhibits excellent and stable electrocatalytic performance, and has good application prospects in the field of electrocatalytic reduction of nitrate to produce ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the FT-IR spectra of the TVPT-COF material prepared in Example 1 and the two raw materials.

[0025] Figure 2 It is the synthesis and molecular formula of the TVPT-COF material in Example 1.

[0026] Figure 3 This is a diagram of the electrochemical test experimental setup in Example 2 using Cu@TVPT-COF as the working electrode.

[0027] Figure 4This is a UV-vis absorption spectrum of the Faraday efficiency and ammonia nitrogen content in the electrolyte detected by the indophenol blue method in Example 2.

[0028] Figure 5 It is the ammonia nitrogen standard curve of the ammonia nitrogen content and Faraday efficiency in the electrolyte detected by the indophenol blue method in Example 2.

[0029] Figure 6 This is a diagram of the ammonia nitrogen yield and Faraday efficiency of the Cu@TVPT-COF electrode material in Example 2.

[0030] Figure 7 It is the XRD spectra of Cu@TVPT-COF and TVPT-COF materials prepared in Example 1 and the two raw materials. DETAILED DESCRIPTION

[0031] Example 1 Preparation of Cu@TVPT-COF material electrode

[0032] (I) The preparation method is as follows:

[0033] 1) Pretreatment of carbon cloth: Cut a rectangular carbon cloth into 1 cm × 2 cm size and soak it in acetone, ethanol, concentrated nitric acid, ethanol, and acetone in turn, ultrasonically treat for 30 min each time, wash it with ultrapure water several times, and dry it in a vacuum drying oven at 60°C for 72 hours.

[0034] 2) Preparation method of Cu@TVPT-COF material: 35.441 mg TAPT and 37.4 mg TVN were mixed in a Pyrex test tube, dissolved in 3 mL ethanol / water (4:1), reacted at 120°C for 72 h after three freeze-thaw-cycle degassing, washed and filtered six times with ethanol and water, and dried to obtain the ionic COF material TVPT-COF.

[0035] 3) Weigh 80 mg of copper sulfate and 40 mg of TVPT-COF material and dissolve them in 20 ml of THF. Stir evenly and transfer to a polytetrafluoroethylene-lined stainless steel autoclave to react at 120°C for 36 hours. After the high-temperature reaction, cool to room temperature, collect the precipitate by centrifugation, wash three times with ethanol, vacuum dry at 60°C for 48 hours, and grind into powder to obtain Cu@TVPT-COF material.

[0036] 4) Preparation method of Cu@TVPT-COF electrode: Use 3mgCu@TVPT-COF catalyst powder, 3mg acetylene black, 40ul naphthol film solution, 200ul isopropanol, 20ul ultrapure water, and disperse evenly by ultrasonication for 60min. Use a 1mL syringe to drop 10-13 drops of ink on the carbon cloth, weigh it after drying, and calculate the catalyst loading according to the mass difference of the carbon cloth before and after.

[0037] (II) Test results

[0038] Figure 1 is the powder FT-IR spectrum of the TVPT-COF material prepared in Example 1. Figure 1 It can be seen that TVPT-COF material has a wavelength of 2200 cm -1 、3800cm -1 、3321.29cm -1 No raw material peaks appeared at any of the sites, indicating that the materials were successfully synthesized and the reactions were carried out according to the experimental design. Figure 2 The diagram is a reaction diagram of the preparation of TVPT-COF in Example 1 and the chemical structures of the raw materials and products. Figure 7 The XRD patterns of Cu@TVPT-COF and TVPT-COF materials prepared in Example 1 and the two raw materials are shown in FIG. Figure 7 It can be seen that the TVPT-COF material prepared in Example 1 does not have the characteristic peaks of the raw materials, proving that the reaction of TAPT and TVN proceeds as designed in the experiment. By comparing TVPT-COF and Cu@TVPT-COF, it can be seen that copper sulfate is successfully incorporated into TVPT-COF.

[0039] Example 2 Application of Cu@TVPT-COF material electrode in electrocatalytic nitrate reduction

[0040] Test method: The prepared Cu@TVPT-COF electrode was used as the working electrode.

[0041] The electrolytic cell used in the experiment was an H-type electrolytic cell, the Nafion117 membrane was a proton exchange membrane, the Cu@TVPT-COF electrode prepared in Example 1 was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, the platinum electrode was used as the counter electrode, and the cathode electrolyte and the anode electrolyte were both 35ml 0.1M KNO3 solution and 35ml 1M KOH solution. The experimental potential was set to -0.3~-0.7V vs.RHE, the IT test time was 1h, and the indophenol blue method was used to detect the ammonia nitrogen content in the electrolyte to calculate the yield and Faraday efficiency.

[0042] Figure 3 This is a diagram of an electrochemical experimental test device, using an H-type electrolytic cell and a three-electrode system for testing.

[0043] Figure 4 , Figure 5 This is the UV-vis absorption spectrum and standard curve of the indophenol blue method used in the experiment to detect the Faraday efficiency and ammonia nitrogen content in the electrolyte. As shown in the figure, five standard curve concentrations were set in the experiment, ranging from 0.0, 0.2, 0.4, 0.8, and 1.2ug ml -1 , R of the standard curve measured experimentally 2It reaches 0.99909, with high credibility, and can be used as an external standard curve. Figure 6 The electrode was used to electrocatalyze nitrate with a Faradaic efficiency of 95.92% at -0.5 V vs. RHE and a maximum of 202.97 mmol h -1 g -1 Ammonia nitrogen yield.

[0044] In summary, the Cu@TVPT-COF electrode material of the present invention has a high ammonia nitrogen yield and Faraday efficiency, and also has good electrocatalytic stability. Therefore, the Cu@TVPT-COF material has an ideal development and application prospect in the field of electrocatalytic nitrate reduction.

[0045] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any person skilled in the art can use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A copper-doped ionic COF material Cu@TVPT-COF, characterized in that: Cu@TVPT-COF was obtained with Cu as the central metal atom and ionic COF material as the matrix.

2. The method for preparing the copper-doped ionic COF material Cu@TVPT-COF according to claim 1, characterized in that: Here’s how: 1) Mixing N,N'-disubstituted-4,4'-bipyridinium cationic salt TVN and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine TAPT, dissolving in ethanol / water, reacting after three freeze-thaw-cycle degassing, washing with ethanol and water six times, filtering and drying to obtain ionic COF material TVPT-COF; 2) Dissolve copper sulfate and TVPT-COF in tetrahydrofuran (THF), mix and stir evenly, transfer to a high-pressure reactor for reaction, collect the precipitate by centrifugation, wash with ethanol several times, and dry to obtain Cu@TVPT-COF.

3. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 1), the molar ratio of TAPT to TVN is 5:3, and the volume ratio of ethanol to water is 4:

1.

4. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 1), the reaction is carried out at 120° C. for 72 hours.

5. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 2), the mass ratio of copper sulfate to TVPT-COF is 2:

1.

6. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 2), the reaction is carried out at 120° C. for 36 hours.

7. A Cu@TVPT-COF electrode according to claim 1, characterized in that: The preparation method is as follows: the Cu@TVPT-COF described in claim 1, acetylene black, naphthol film solution, isopropanol, and ultrapure water are drop-coated on carbon cloth after ultrasonic treatment, and dried to obtain a Cu@TVPT-COF electrode.

8. Use of the Cu@TVPT-COF electrode according to claim 7 in electrochemical nitrate reduction.

9. The use according to claim 8, characterized in that: The Cu@TVPT-COF electrode described in claim 7 is used as a working electrode, the counter electrode is a platinum sheet electrode, the reference electrode is an Ag / AgCl reference electrode, and the cathode electrolyte and the anode electrolyte are both 0.1M KNO3 solution and 1M KOH solution.

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