Metal / imino COF composite catalyst and metal / imino COF composite catalytic electrode as well as preparation method and application thereof

Abstract

The invention discloses a metal / imino COF composite catalyst, a metal / imino COF composite catalytic electrode and a preparation method and application of the metal / imino COF composite catalyst and the metal / imino COF composite catalytic electrode. The metal / imino COF composite catalyst comprises imino COF and metal nanoparticles, the mass ratio of the imino COF to the metal nanoparticles is (1-25): (75-99), and the imino COF is exfoliated imino COF. When the metal / imino COF composite catalyst disclosed by the invention is applied to the process of electrocatalytic reduction of CO2, a dynamic and synergistic interface microenvironment is constructed. An imino group in the covalent organic framework plays dual roles, on one hand, adsorption of carbon dioxide is promoted, CO2 is stabilized through electron interaction, and the CO2 is rapidly transported to a catalytic active site of the metal nano-catalyst; on the other hand, the availability of the protons is adjusted through the hydrogen bond network to adjust the proton coverage, proton collision is reduced, and generation of by-products is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic materials, in particular to a metal / imino COF composite catalyst and a metal / imino COF composite catalytic electrode as well as a preparation method and application thereof. BACKGROUND

[0002] With the development of global industrialization, the overuse of fossil energy by humans not only leads to energy shortages, but also causes the concentration of carbon dioxide (CO2) in the atmosphere to rise year by year. The rise in CO2 concentration causes a series of problems such as the greenhouse effect and environmental pollution, making the development of human society face unprecedented challenges. Before the industrial revolution, the concentration of CO2 in the atmosphere was about 280 ppm, but by 2018, the concentration of CO2 in the atmosphere had exceeded 400 ppm, reaching 411 ppm, far exceeding the safe upper limit of 350 ppm, and it is predicted that by the end of this century, the concentration of CO2 will rise to about 600 ppm. The use of renewable energy to replace existing fossil fuels to produce clean fuels and high-value chemical products is of great significance to solving current environmental problems.

[0003] Among the different products of CO2RR, the technology of converting CO2 into high-value-added products has industrial feasibility and is one of the most promising reactions in the chemical industry. Chinese patent with application number CN202311337762.6 uses alkaline steam diffusion and in-situ self-assembly method with foam copper as copper source to synthesize copper MOFs material, which can reduce carbon dioxide to ethanol product at a voltage lower than-0.4 V vs RHE, and the selectivity of carbon product is 100%. Chinese patent with application number CN202111152480.X constructs an interface environment for catalytic reduction of CO2 with coexistence of Cu and CuO nanorod and Cu nanorod supported on graphene aerogel, which produces C2H4 from CO2 at a low overpotential of-1.4 V (vs. RHE) with a Faraday efficiency of more than 50%. Chinese patent with application number CN202311461530.1 prepares a composite material of silver-imidazole complex and silver, which has a Faraday efficiency of CO of 76.5% at the optimal potential of-0.9 V (vs. RHE). +

[0004] ​Currently, most studies on CO2 reduction reactions (CO2RR) evaluate catalyst performance using high-purity CO2. However, the concentration of available CO2 feedstock in actual industrial processes is relatively low, such as 6-15% in coal-fired flue gas and approximately 15-25% in industrial furnaces. Therefore, the limited availability of CO2 severely inhibits CO2 coverage on the catalyst surface. This hinders efficient CC coupling, exacerbates the hydrogen evolution reaction in the presence of large amounts of water, and thus reduces product selectivity and overall yield. Currently, high-purity CO2 requires a series of complex steps including capture, concentration, and purification, which incurs substantial costs. Directly enriching CO2 through catalyst function and electroreducing CO2 in industrial waste gas to convert low-concentration CO2 into high-value-added chemicals eliminates a series of complex purification steps and effectively reduces energy consumption. However, direct electroreduction technology for low-concentration CO2 is still in its early stages. It not only faces numerous challenges such as high reduction overpotential, low current density, and poor product selectivity under ideal conditions, but also the significant decline in catalytic activity caused by low-concentration CO2. Therefore, direct electroreduction of low-concentration CO2 has become a major challenge in this field, and developing catalysts suitable for electrochemical reduction of low-concentration CO2 is the key to realizing the industrial application of CO2RR. Summary of the Invention

[0005] This invention addresses the shortcomings of existing electrochemical reduction methods for low-concentration CO2 with limited selectivity for the ethanol product by providing a metal / imino-COF composite catalyst and its preparation method. This invention utilizes a simple ultrasonic exfoliation and mixing method to construct a novel imino-organic covalent framework (imino-COF) composite metal nanocatalyst, enabling direct electrochemical reduction of low-concentration CO2.

[0006] The present invention also provides a metal / imino COF composite catalytic electrode using the above-mentioned metal / imino COF composite catalyst, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A metal / imino COF composite catalyst comprising imino COF and metal nanoparticles, wherein the mass ratio of imino COF to metal nanoparticles is 1~25:75~99, and the imino COF is exfoliated imino COF.

[0009] The metal in the metal nanoparticles is one of Mn, Fe, Co, Sn, Ni, Cu, Zn, Ag, Pd, Pb and Au.

[0010] The preparation method of the above-mentioned metal / imino COF composite catalyst includes the following steps:

[0011] S01: Add a certain amount of imino COF powder to a solvent to obtain an imino COF dispersion; wherein the solvent is an organic solvent or a mixture of organic solvent and water; the concentration of the imino COF dispersion in this step is not limited, as long as a dispersion can be formed.

[0012] S02: The imino-COF dispersion is subjected to ultrasonic treatment to exfoliate the imino-COF and obtain an imino-COF mixture; the power of the ultrasonic treatment is not less than 500 W, and the ultrasonic treatment time is more than 12 hours;

[0013] S03: The imino-COF mixture obtained in step S02 is centrifuged and dried to obtain the exfoliated imino-COF powder; the drying temperature is 50~70℃ and the time is not less than 10 h.

[0014] S04: Add a certain amount of the exfoliated imino COF powder and metal nanoparticles obtained in step S03 to the solvent; and perform ultrasonic composite treatment on them to obtain a mixed solution; the ultrasonic composite treatment time is not less than 1 h; the mass ratio of imino COF to metal nanoparticles is 1~25:75~99; the concentration of the mixed solution in this step is not limited, as long as it can form a dispersion.

[0015] S05: The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution obtained in step S04; the drying temperature is 50~70℃ and the time is not less than 10 h.

[0016] The solvents in steps S01 and S04 are organic solvents or a mixture of organic solvent and water (the volume ratio of organic solvent to water is 1:3 to 3:1). The solvents in steps S01 and S04 can be the same or different.

[0017] The preparation method of the above-mentioned metal / imino COF composite catalyst includes the following steps:

[0018] S11: Add imino COF powder and metal nanoparticles to a solvent and perform ultrasonic composite treatment to obtain a mixed solution; the power of the ultrasonic composite treatment is not less than 500 W, and the ultrasonic treatment time is more than 12 hours; the solvent in step S11 is an organic solvent or a mixed solution of organic solvent and water (the volume ratio of organic solvent to water is 1:3~3:1); the mass ratio of imino COF to metal nanoparticles is 1~25:75~99; the concentration of the mixed solution in this step is not limited, as long as it can form a dispersion;

[0019] S12: The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution obtained in step S11; the drying temperature is 50~70℃ and the time is 4~10 h.

[0020] A metal / imino COF composite catalytic electrode includes a conductive substrate and a catalyst layer coated on the conductive substrate. The catalyst layer is prepared by a catalyst solution, which includes the aforementioned metal / imino COF composite catalyst. The thickness of the catalyst layer is 50-200 micrometers.

[0021] The catalyst solution further includes a binder and conductive carbon black; the amount of binder added is 3% to 6% of the mass of the metal / imino COF composite catalyst; the amount of conductive carbon black added is 1% to 5% of the mass of the metal / imino COF composite catalyst.

[0022] The preparation method of the above-mentioned metal / imino COF composite catalytic electrode includes the following steps:

[0023] S1: The metal / imino COF composite catalyst is dispersed in a solvent; then a binder is added and ultrasonically dispersed to obtain a catalyst solution; wherein, the amount of binder added is 3% to 6% of the mass of the metal / imino COF composite catalyst; the solvent in step S1 is an organic solvent or a mixed solution of organic solvent and water (the volume ratio of organic solvent to water is 1:3 to 3:1).

[0024] S2: Place the conductive substrate on a heating stage, uniformly spray the catalyst solution onto the conductive substrate, and dry the substrate with the catalyst sprayed on in a vacuum drying oven to obtain a metal / imino COF composite catalytic electrode; the drying temperature in step S2 is 60~100℃; the time is not less than 3 h.

[0025] The imino COF powder is prepared using the following steps:

[0026] (1) Using dioxane and water as solvents, the monomer is dispersed in the solvent and ultrasonically mixed in a sealed Pyrex tube to obtain a mixture; the volume ratio of dioxane to water is 2:0.6; the mass-volume ratio of the monomer to the solvent is 25~35 mg / ml;

[0027] (2) The sealed Pyrex tube containing the mixture is subjected to a freeze-pump-thaw cycle degassing treatment, repeated multiple times, so that the monomer is uniformly dispersed in the solvent;

[0028] (3) The sealed Pyrex tube containing the uniformly dispersed liquid is placed in a muffle furnace and heated at a constant temperature of 120°C to obtain a precipitate. After centrifugation and washing, the precipitate is dried to obtain the imino COF powder.

[0029] In step (1), the monomer is 1,3,5-triaminoguanidine hydrochloride and trialdehyde phloroglucinol (mass ratio 3~4:2); or the monomer is 1,3,5-phenyltriamine and 3,5-tricarboxymethylbenzene (mass ratio 3~4:2); or the monomer is 2,5-diaminopyridine and terephthalaldehyde (mass ratio 3~4:2); or the monomer is 4,4'-diaminodiphenyl ether and terephthalic acid (mass ratio 3~4:2).

[0030] The catalyst solution also includes conductive carbon black, and the amount of conductive carbon black added is 1% to 5% of the mass of the metal / imino COF composite catalyst.

[0031] The conductive substrate is one or more of carbon paper, carbon cloth, metal mesh, metal foam, and metal fiber.

[0032] In step S2, the temperature of the heating table is 60~100 ℃.

[0033] The above-mentioned metal / imino COF composite catalytic electrode is used in the electrocatalytic reduction of CO2. It is particularly suitable for the electrochemical reduction of low-concentration CO2 (i.e., CO2 concentration greater than 0 and less than 100%).

[0034] The beneficial effects of this invention are as follows:

[0035] 1) The preparation method of the metal / imino COF composite catalyst of the present invention is simple, easy to operate, and has no irritating taste.

[0036] 2) This invention can directly convert low-concentration CO2 into high-value-added chemicals without CO2 capture and purification, greatly reducing energy consumption and costs.

[0037] 3) The metal / imino COF composite catalyst of the present invention can enhance the stability of the composite catalyst.

[0038] 4) The metal / imino COF composite catalyst of this invention constructs a dynamic and synergistic interfacial microenvironment when applied to the electrocatalytic reduction of CO2. The imino groups in the covalent organic framework play a dual role: on the one hand, they promote the adsorption of carbon dioxide and stabilize CO2 through electronic interactions, enabling its rapid transport to the catalytically active sites of the metal nanocatalyst; on the other hand, they regulate proton availability through the hydrogen bond network to adjust proton coverage, reduce proton collisions, and thus reduce the formation of byproducts.

[0039] 5) The metal / imino COF composite catalyst of the present invention can be effectively controlled by the added metal nanoparticles to prepare single metal catalysts of different metals.

[0040] 6) The metal / imino COF composite catalyst of the present invention exhibits excellent stability and high selectivity for ethanol, the CO2 reduction product, under low concentration CO2 conditions. Attached Figure Description

[0041] Figure 1 The graph shows the test results of the electrocatalytic reduction performance of the metal / imino COF composite catalyst prepared in Example 1 for CO2 reduction.

[0042] Figure 2 The figure shows the stability test results of the electrocatalytic reduction of CO2 by the metal / imino COF composite catalyst prepared in Example 1. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] Example 1

[0045] A method for preparing a Cu / imino-COF composite catalytic electrode includes the following steps:

[0046] Part 1: Preparation of imino-COF powder.

[0047] 1) Take a mixed solution of 2 ml dioxane and 0.6 ml water as a solvent, disperse 42 mg of 1,3,5-triaminoguanidine hydrochloride and 28 mg of trialdehyde phloroglucinol in the solvent, place them in a sealed Pyrex tube and sonicate to mix to obtain a mixed solution.

[0048] 2) The sealed Pyrex tube containing the mixture is subjected to a freeze-pump-thaw cycle for degassing, repeated multiple times, so that the monomer is uniformly dispersed in the solvent to obtain a uniform dispersion.

[0049] 3) Place the sealed Pyrex tube containing the uniformly dispersed liquid in a muffle furnace and heat it at 120°C for 24 hours to obtain precipitated imino COF powder. After washing the precipitate with DMF, water and ethanol by centrifugation, dry it (at 50°C) overnight to obtain imino COF powder.

[0050] Part 2: Preparation of metal / imino COF composite catalysts.

[0051] 4) Take 5 mg of imino COF powder and 100 mg of Cu nanoparticles, dissolve them in 20 ml of isopropanol aqueous solution (the volume ratio of isopropanol to water is 1:3), and perform ultrasonic composite treatment. The power of ultrasonic composite treatment is 800 W, and the ultrasonic treatment time is 20 hours to obtain a mixed solution.

[0052] 5) The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution; the drying temperature is 50℃ and the time is 10 h.

[0053] Part 3: Preparation of metal / imino COF composite catalytic electrode.

[0054] 6) Dissolve 100 mg Cu / imino COF powder in 10 mL of a mixture with a volume ratio of isopropanol:water = 1:3, add 5 mg Nafion D520 binder (manufacturer: Alfa Aesar) and 5 mg conductive carbon black ECP-600JD (Suzhou Shengernuo Technology Co., Ltd.), and disperse by ultrasonication to obtain the catalyst solution;

[0055] 7) The conductive substrate (SGL-39BB, thickness: 26.7 µm, size: 2.5 × 5 cm) was then placed. 2 The solution obtained in step (6) was placed on a heating platform at 90 °C and sprayed evenly onto the conductive substrate under a pressure of 1.0 MPa air pump using a spray gun. The substrate was then dried in a vacuum drying oven at 65 °C for 4 h to obtain a Cu / imino COF catalytic electrode (catalyst layer thickness is about 1 µm).

[0056] Example 2

[0057] A method for preparing an Ag / imino COF composite catalytic electrode includes the following steps:

[0058] Part 1: Preparation of imino-COF powder.

[0059] 1) Take a mixed solution of 2 ml dioxane and 0.6 ml water as a solvent, disperse 56 mg of 1,3,5-phenyltriamine and 28 mg of 3,5-tricarboxymethylbenzene in the solvent, place them in a sealed Pyrex tube and sonicate to mix to obtain a mixed solution;

[0060] 2) The sealed Pyrex tube containing the mixture is subjected to a freeze-pump-thaw cycle for degassing, repeated multiple times, so that the monomer is uniformly dispersed in the solvent to obtain a uniform dispersion.

[0061] 3) Place the sealed Pyrex tube containing the uniformly dispersed liquid in a muffle furnace and heat it at 100°C for 10 h to obtain precipitated imino COF powder. After washing the precipitate with DMF, water and ethanol by centrifugation, dry it (at 50°C) overnight to obtain imino COF powder.

[0062] Part 2: Preparation of metal / imino COF composite catalysts.

[0063] 4) Add 50 mg of imino-COF powder to 100 ml of water to obtain an imino-COF dispersion;

[0064] 5) The imino-COF dispersion is subjected to ultrasonic treatment to exfoliate the imino-COF and obtain an imino-COF mixture; the ultrasonic treatment power is 500 W and the ultrasonic treatment time is 20 h;

[0065] 6) The imino-COF mixture is centrifuged and dried to obtain the exfoliated imino-COF powder; the drying temperature is 70℃ and the time is 10 h.

[0066] 7) Add 10 mg of the exfoliated imino COF powder obtained in step 6) and 100 mg of Ag nanoparticles to 10 ml of isopropanol aqueous solution (the volume ratio of isopropanol to water is 3:1); and perform ultrasonic composite treatment on them to obtain a mixed solution; the ultrasonic composite treatment time is 1 h;

[0067] 8) The mixed solution obtained in step 7) is centrifuged, washed, and dried to obtain the metal / imino COF composite catalyst; the drying temperature is 60℃ and the time is 10 h.

[0068] Part 3: Preparation of metal / imino COF composite catalytic electrode.

[0069] 9) Dissolve 100 mg Ag / imino COF powder in 10 mL of a mixture with a volume ratio of isopropanol:water = 1:3, add 3 mg Nafion D520 binder (manufacturer: Alfa Aesar) and 1 mg conductive carbon black ECP-600JD (Suzhou Shengernuo Technology Co., Ltd.), and disperse by ultrasonication to obtain the catalyst solution;

[0070] 10) The conductive substrate (SGL-39BB, thickness: 26.7 µm, size: 2.5 × 5 cm) 2The catalyst solution obtained in step (9) was uniformly sprayed onto the conductive substrate by a spray gun under a pressure of 1.0 MPa air pump using a spraying method on a heating table at 60 ℃. The substrate was then dried in a vacuum drying oven at 100 ℃ for 3 h to obtain an Ag / imino COF catalytic electrode (catalyst layer thickness is about 1µm).

[0071] Example 3

[0072] A method for preparing a Sn / imino-COF composite catalytic electrode includes the following steps:

[0073] Part 1: Preparation of imino-COF powder.

[0074] 1) Take a mixed solution of 2 ml dioxane and 0.6 ml water as a solvent, disperse 42 mg of 2,5-diaminopyridine and 28 mg of terephthalaldehyde in the solvent, place them in a sealed Pyrex tube and sonicate to mix to obtain a mixed solution;

[0075] 2) The sealed Pyrex tube containing the mixture is subjected to a freeze-pump-thaw cycle for degassing, repeated multiple times, so that the monomer is uniformly dispersed in the solvent to obtain a uniform dispersion.

[0076] 3) Place the sealed Pyrex tube containing the uniformly dispersed liquid in a muffle furnace and heat it at 120°C for 24 h to obtain precipitated imino COF powder. After washing the precipitate with DMF, water and ethanol by centrifugation, dry it (at 50°C) overnight to obtain imino COF powder.

[0077] Part 2: Preparation of metal / imino COF composite catalysts.

[0078] 4) Take 1 mg of imino COF powder and 99 mg of Sn nanoparticles, dissolve them in 10 ml of isopropanol aqueous solution (the volume ratio of isopropanol to water is 1:3), and perform ultrasonic composite treatment. The power of ultrasonic composite treatment is 1000 W, and the ultrasonic treatment time is 15 hours to obtain a mixed solution.

[0079] 5) The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution; the drying temperature is 70℃ and the time is 4 h.

[0080] Part 3: Preparation of metal / imino COF composite catalytic electrode.

[0081] 6) Dissolve 100 mg Sn / imino COF powder in 10 mL of a mixture with a volume ratio of isopropanol:water = 1:3, add 6 mg Nafion D520 binder (manufacturer: Alfa Aesar) and 5 mg conductive carbon black ECP-600JD (Suzhou Shengernuo Technology Co., Ltd.), and disperse by ultrasonication to obtain the catalyst solution;

[0082] 7) The conductive substrate (SGL-39BB, thickness: 26.7 µm, size: 2.5 × 5 cm) was then placed. 2 The solution obtained in step (6) was placed on a heating platform at 90 °C and sprayed evenly onto the conductive substrate under a pressure of 1.0 MPa air pump using a spray gun. The substrate was then dried in a vacuum drying oven at 60 °C for 5 h to obtain a Sn / imino COF catalytic electrode (catalyst layer thickness is about 1 µm).

[0083] Example 4

[0084] A method for preparing an Au / imino COF composite catalytic electrode includes the following steps:

[0085] Part 1: Preparation of imino-COF powder.

[0086] 1) Take a mixed solution of 2 ml dioxane and 0.6 ml water as a solvent, disperse 42 mg of 4,4'-diaminodiphenyl ether and 28 mg of terephthalic acid in the solvent, place them in a sealed Pyrex tube and sonicate to mix to obtain a mixed solution;

[0087] 2) The sealed Pyrex tube containing the mixture is subjected to a freeze-pump-thaw cycle for degassing, repeated multiple times, so that the monomer is uniformly dispersed in the solvent to obtain a uniform dispersion.

[0088] 3) Place the sealed Pyrex tube containing the uniformly dispersed liquid in a muffle furnace and heat it at 120°C for 24 h to obtain precipitated imino COF powder. After washing the precipitate with DMF, water and ethanol by centrifugation, dry it (at 50°C) overnight to obtain imino COF powder.

[0089] Part 2: Preparation of metal / imino COF composite catalysts.

[0090] 4) Take 25 mg of imino COF powder and 75 mg of Au nanoparticles, dissolve them in 30 ml of ethanol aqueous solution (ethanol to water volume ratio of 1:1), and perform ultrasonic composite treatment. The power of ultrasonic composite treatment is 1000 W, and the ultrasonic treatment time is 18 hours to obtain a mixed solution.

[0091] 5) The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution; the drying temperature is 70℃ and the time is 6 h.

[0092] Part 3: Preparation of metal / imino COF composite catalytic electrode.

[0093] 6) Dissolve 100 mg Sn / imino COF powder in 10 mL of a mixture with a volume ratio of isopropanol:water = 1:3, add 5 mg Nafion D520 binder (manufacturer: Alfa Aesar) and 5 mg conductive carbon black ECP-600JD (Suzhou Shengernuo Technology Co., Ltd.), and disperse by ultrasonication to obtain the catalyst solution;

[0094] 7) The conductive substrate (SGL-39BB, thickness: 26.7 µm, size: 2.5 × 5 cm) was then placed. 2 The solution obtained in step (6) was placed on a heating platform at 100 °C and sprayed evenly onto the conductive substrate under a pressure of 1.0 MPa air pump using a spray gun. The substrate was then dried in a vacuum drying oven at 90 °C for 4 h to obtain an Au / imino COF catalytic electrode (catalyst layer thickness is about 1 µm).

[0095] The Cu / imino-COF composite catalytic electrode prepared in Example 1 was used to electrocatalyze the reduction of CO2 to ethanol in a low-concentration CO2 environment. The Faraday efficiency of ethanol was tested, and the test methods included:

[0096] The Faraday efficiency measurement device was a CHI-760E electrochemical workstation from Shanghai Chenhua Instrument Co., Ltd. The testing conditions were as follows: the Cu / imino-COF composite catalytic electrode prepared in Example 1 was used as the cathode, and an iridium-doped titanium mesh (Suzhou Shuertai Industrial Technology Co., Ltd.) was used as the anode; the reaction was carried out in an MEA electrolytic cell; the gas pressure was 1 atmosphere, and the temperature was room temperature (25℃); the anode chamber was 1 mol / L. -1 The electrolyte is KOH; CO2 gas with a volume concentration of 15% is continuously introduced into the cathode chamber at a flow rate of 20 sccm, and the electrode area is 4 cm². 2 The catalyst loading on the electrode is 1 mg cm⁻¹ -2 Electrolysis was performed by applying a constant potential of -2.4 V vs RHE (vs RHE refers to the value relative to the standard hydrogen electrode). The CO2 reduction products were analyzed by gas chromatography using a GC-2014 instrument from SHIMADZU Corporation, Japan.

[0097] Test results are as follows Figure 1 As shown. Compared to nano-copper catalysts, from Figure 1As can be seen, the Cu / imino-COF composite catalytic electrode prepared in Example 1 still exhibits excellent electrocatalytic CO2 reduction performance at low CO2 concentrations. When the CO2 gas concentration is 15%, the Faraday efficiency of electrocatalytic CO2 reduction to ethanol is higher than 50%, reaching 56%.

[0098] The stability of the Cu / imino-COF composite catalytic electrode prepared in Example 1 for electrocatalytic reduction of CO2 at room temperature was tested under a 200 mA cm⁻¹ pressure. -2 The constant current with current density was tested, and the results are as follows: Figure 2 As shown. Figure 2 This is a graph showing the electrocatalytic reduction CO2 stability test results of the Cu / imino-COF composite catalytic electrode prepared in Example 1. Figure 2 As can be seen in the MEA electrolyzer, the Cu / imino COF catalyst can achieve a reaction time of 200 mA cm⁻¹. -2 It can be stably catalyzed for 250 h at a current density without significant degradation.

[0099] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0100] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A metal / imino COF composite catalyst, characterized in that, The metal / imino COF composite catalyst comprises imino COF and metal nanoparticles, wherein the mass ratio of imino COF to metal nanoparticles is 1~25:75~99, and the imino COF is exfoliated imino COF.

2. The metal / imino COF composite catalyst according to claim 1, characterized in that, The metal in the metal nanoparticles is one of Mn, Fe, Co, Sn, Ni, Cu, Zn, Ag, Pd, Pb and Au.

3. The method for preparing the metal / imino COF composite catalyst according to claim 1 or 2, characterized in that, Includes the following steps: S01: A certain amount of imino COF powder is added to a solvent to obtain an imino COF dispersion; wherein the solvent is an organic solvent or a mixture of an organic solvent and water; S02: The imino-COF dispersion is subjected to ultrasonic treatment to exfoliate the imino-COF and obtain an imino-COF mixture; the power of the ultrasonic treatment is not less than 500W and the ultrasonic treatment time is more than 12 hours. S03: The imino-COF mixture obtained in step S02 is centrifuged and dried to obtain the exfoliated imino-COF powder; the drying temperature is 50~70℃ and the time is not less than 10 h. S04: Add a certain amount of the exfoliated imino COF powder and metal nanoparticles obtained in step S03 to a solvent; and perform ultrasonic composite treatment on them to obtain a mixed solution; the ultrasonic composite treatment time is not less than 1 h; S05: The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution obtained in step S04; the drying temperature is 50~70℃ and the time is not less than 10 h.

4. The method for preparing the metal / imino COF composite catalyst according to claim 1 or 2, characterized in that, Includes the following steps: S11: Add imino COF powder and metal nanoparticles to a solvent and perform ultrasonic composite treatment to obtain a mixed solution; the power of the ultrasonic composite treatment is not less than 500 W, and the ultrasonic treatment time is more than 12 hours. S12: The metal / imino COF composite catalyst can be obtained by centrifuging, washing and drying the mixed solution obtained in step S11; the drying temperature is 50~70℃ and the time is 4~10 h.

5. A metal / imino COF composite catalytic electrode, characterized in that, The metal / imino COF composite catalytic electrode includes a conductive substrate and a catalyst layer coated on the conductive substrate. The catalyst layer is prepared by using a catalyst solution, and the catalyst solution includes the metal / imino COF composite catalyst according to claim 1 or 2.

6. The metal / imino COF composite catalytic electrode according to claim 5, characterized in that, The catalyst solution also includes a binder and conductive carbon black; the amount of binder added is 3% to 6% of the mass of the metal / imino COF composite catalyst; the amount of conductive carbon black added is 1% to 5% of the mass of the metal / imino COF composite catalyst.

7. The method for preparing the metal / imino COF composite catalytic electrode according to any one of claims 5 or 6, characterized in that, Includes the following steps: S1: The metal / imino COF composite catalyst is dispersed in a solvent; then a binder is added and ultrasonically dispersed to obtain a catalyst solution; wherein the amount of binder added is 3% to 6% of the mass of the metal / imino COF composite catalyst; S2: Place the conductive substrate on the heating stage, uniformly spray the catalyst solution onto the conductive substrate, and dry the coated substrate in a vacuum drying oven to obtain a metal / imino COF composite catalytic electrode.

8. The method for preparing the metal / imino COF composite catalytic electrode according to claim 7, characterized in that, The catalyst solution also includes conductive carbon black, and the amount of conductive carbon black added is 1% to 5% of the mass of the metal / imino COF composite catalyst.

9. The method for preparing the metal / imino COF composite catalytic electrode according to claim 7, characterized in that, The conductive substrate is one or more of carbon paper, carbon cloth, metal mesh, metal foam, and metal fiber; In step S2, the temperature of the heating platform is 60~100 ℃.

10. The application of the metal / imino COF composite catalytic electrode according to any one of claims 5 or 6 in the electrocatalysis of CO2.

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