A catalytic material, method of preparation and use in electrocatalytic reduction of carbon dioxide

Abstract

The application relates to the technical field of metal-based-organic framework catalysts, in particular to a catalytic material, a preparation method and application in electrocatalytic carbon dioxide reduction, wherein after a divalent copper salt and a BIBT organic ligand are mixed in a solvent, a Cu-BIBT catalytic material is prepared through a temperature rising-constant temperature-temperature falling process control, the material can keep a stable copper-based metal-organic framework structure under strong alkali conditions (pH=14), has strong electrocatalytic CO2RR and electron transfer capacity, and can promote the generation of C2 + products in the electrocatalytic CO2RR, and greatly reduces the difficulty of generating C2 + products in the electrocatalytic CO2RR.

Description

Technical Field

[0001] This invention relates to the field of metal-based organic framework catalyst technology, and more particularly to a catalytic material, its preparation method, and its application in electrocatalytic carbon dioxide reduction, specifically a copper-based organic framework catalytic material, its preparation method, and its application in electrocatalytic carbon dioxide reduction. Background Technology

[0002] Electrocatalytic carbon dioxide reduction (CO2RR) is a catalytic reaction that converts CO2 into valuable fuels or chemicals, including C1 products and C2 products. + The products, of which C1 products mainly include CO, HCOO / HCOOH, CH4 and CH3OH; C2 products + The main products include: CH3COOH, C2H4, C2H5OH, C2H6, and n-C3H7OH. In recent years, due to C2... + The product has attracted widespread attention due to its high energy density, broad market application prospects, and good compatibility with existing energy infrastructure. However, achieving efficient and highly selective C2 generation remains a challenge. + However, the product faces significant challenges: ① The kinetic energy barrier of the C-C coupling step is high, making it difficult to form C-C bonds; ② Hydrogen evolution reaction is very likely to occur during the reaction, which reduces the Faraday efficiency of the target product and results in a low formation rate of the target product.

[0003] Metal-based catalysts are among the few that can catalyze the generation of C2. + Catalytic materials for the products have been extensively studied. For example, JXUST-301D, disclosed in Wu XY, Li ZY, Zhang ML, et al. In Situ Synthesis of Copper-Based Metal–Organic Frameworks with Ligand Defects for Electrochemical Reduction of CO2 into C2 Products[J]. Inorganic Chemistry, 2024, 63: 19897–19905, can achieve a Faradaic efficiency of 56% in weakly alkaline electrolyte (0.01M KOH) or neutral electrolyte (1M KCL), with a reaction potential of -1.0V vs. RHE.

[0004] For example, the Cu-PzH disclosed in Wang R, Liu J, Huang Q, et al. Partial Coordination-Perturbed Bi-Copper Sites for Selective Electroreduction of CO2 to Hydrocarbons[J]. Angewandte Chemie International Edition, 2021, 60: 19829-19835, has a Faradaic efficiency of 60% at pH 14 (1M KOH) and a reaction potential of -1.0V vs. RHE, but its structural stability is poor.

[0005] For example, Lu YF, Dong LZ, Liu J, Yang, et al. Predesign of Catalytically Active Sites via Stable Coordination Cluster Model System for Electroreduction of CO2 to Ethylene[J]. Angewandte Chemie International Edition, 2021, 60: 26210-26217 discloses that Cu3-Br achieves a Faraday efficiency of 55.01% in 0.5 M KOH environment, with a reaction potential of -1.1 V vs. RHE.

[0006] Another example: Meng X, Huang H, Zhang X, et al. Steering C–C Coupling by HollowCu2O@C / N Nanoreactors for Highly Efficient Electroreduction of CO2to C2 + The Cu2O@C / N reaction disclosed in Products[J]. Advanced Functional Materials, 2024, 34: 2312719 achieves a Faraday efficiency of 59.2% in a 0.1 MkOH environment with a reaction potential of -0.9 V vs. RHE.

[0007] For example, the Cu-adeMOF disclosed in Yang F, Chen A, Deng PL, et al. Highly Efficient Electroconversion of Carbon Dioxide into Hydrocarbons by Cathodized Copper-Organic Frameworks[J]. Chemical Science, 2019, 10: 7975-7981 achieves a Faraday efficiency of 45% in 0.1 MkOH environment, with a reaction potential of -1.4 V vs. RHE.

[0008] It is evident that these existing metal-based catalysts are used to catalyze the generation of C2. + When used as catalytic materials, these products can, to some extent, weaken the hydrogen evolution reaction and improve the formation efficiency of the target product. However, these metal-based catalysts are all difficult to maintain high structural stability in strongly alkaline environments. Therefore, some researchers have conducted research on copper-based catalysts in the prior art. For example, patent application number 202311090438.9 discloses a method for preparing and applying copper metal-organic frameworks. This method uses a three-system solute composed of CuCl2·2H2O, H2NIA (5-(1,3-dioxy-1H-benzoquinoline-2(3H)-yl)isophthalic acid), and BIBT (4,7-bis(1H-imidazol-1-yl)-2,1,3-benzothiadiazole) to ultrasonically dissolve the solute and solvent into a mixture, and then prepares a copper-based catalyst by hydrothermal reaction and cooling to room temperature. The catalyst showed no structural damage after static soaking in solutions with pH values ​​of 2 to 12 for 24 hours, exhibiting good pH stability. However, whether this copper-based catalyst can maintain good pH stability in a strongly alkaline environment (pH=14) and whether it has superior Faraday efficiency has not been studied or disclosed. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a catalytic material, its preparation method, and its application in electrocatalytic carbon dioxide reduction. Through the control of specific organic ligands and process parameters, a catalytic material with a stable structure and high selectivity for electrocatalytic CO2 reduction to C2 is synthesized under strongly alkaline conditions at pH=14. + The product is a Cu-BIBT catalyst.

[0010] The specific technical solution is as follows:

[0011] One of the objectives of this invention is to provide a method for preparing a catalytic material, wherein the catalytic material is a copper-based metal-organic framework catalytic material, comprising the following steps:

[0012] (1) Mix divalent copper salt, BIBT and solvent to obtain a mixture;

[0013] (2) Heat the mixture to 100-140℃, react at a constant temperature for 70-80h, and then cool it to 20-40℃ to obtain crystals;

[0014] (3) The crystals are washed and dried to obtain a copper-based metal-organic framework catalytic material; the solvent is an aqueous solution of acetonitrile, and the volume ratio of acetonitrile to water is 4:3; the molar ratio of the divalent copper salt to the BIBT is 0.04-0.06:0.02-0.04, and the molar volume ratio (mmol / mL) of the divalent copper salt to acetonitrile is 1-1.5:80; the heating time is 12h, and the cooling time is 36h.

[0015] Preferably, the divalent copper salt is at least one selected from copper nitrate, copper chloride, and copper sulfate. More preferably, it is copper nitrate.

[0016] Preferably, the molar ratio of the divalent copper salt to the BIBT is 0.05:0.025, and the molar volume ratio (mmol / mL) of the divalent copper salt to acetonitrile is 1:80.

[0017] Preferably, the isothermal reaction time is 72 hours.

[0018] Preferably, the temperature of the isothermal reaction is 120°C, and the cooling is reduced to 30°C.

[0019] Preferably, the washing is performed using ethanol. The amount of ethanol used in each washing is a mixture of crystals and ethanol at a mass-to-volume ratio of 1:5, followed by filtration.

[0020] Preferably, the drying process is carried out at 60°C for 12 hours.

[0021] The second objective of this invention is to provide a catalytic material prepared by the above method, which can electrocatalyze the reduction of CO2 to C2 in an electrolyte with pH=14. + The product has a Faraday efficiency of ≥59.8%.

[0022] The third objective of this invention is to provide the application of the catalytic material prepared by the above method in electrocatalytic carbon dioxide reduction.

[0023] In a specific application, the catalytic material is placed in a liquid-phase flow cell as a catalyst; CO2 is reduced to C2 in a KOH solution with pH=14 and a potential of -0.8~-1.0V vs. RHE. + The product has a Faraday efficiency of ≥59.8%.

[0024] More preferably, CO2 is reduced to C2 at a potential of -1.0V vs. RHE.+ The product has a Faraday efficiency of 67%.

[0025] Compared with the prior art, the technical effects of this invention are reflected in:

[0026] This invention creates a Cu-BIBT catalytic material by mixing divalent copper salts and BIBT organic ligands in a solvent and then controlling the process through heating-isothermal-cooling. This material maintains a stable copper-based metal-organic framework structure under strongly alkaline conditions (pH=14) and exhibits strong electrocatalytic CO2RR and electron transfer capabilities, as well as strong ability to control C2+ in electrocatalytic CO2RR. + The product exhibits high selectivity, significantly reducing C2 in electrocatalytic CO2RR. + Difficulty in generating the product. Attached Figure Description

[0027] In order to enable those skilled in the art to fully understand the technical solution of the present invention, the following description is made in conjunction with the technical solution content and the accompanying drawings.

[0028] Figure 1 A schematic diagram of the reaction process for synthesizing the catalytic material for this invention.

[0029] Figure 2 A schematic diagram of the crystal structure of the catalytic material obtained in Example 1 of this invention.

[0030] Figure 3 Fourier transform infrared spectra of the catalytic material and BIBT ligand obtained in Example 1 of this invention.

[0031] Figure 4 Powder diffraction (PXRD) pattern of the catalytic material obtained in Example 1 of this invention.

[0032] Figure 5 A schematic diagram of the spatial coordination configuration of the catalytic material obtained in Example 1 of this invention.

[0033] Figure 6 Powder diffraction (PXRD) pattern of the catalytic material obtained in Example 1 of this invention for pH stability testing.

[0034] Figure 7 The catalytic material obtained in Example 1 of this invention was used as a catalyst in C2 at a potential of -0.8 to -1.1 V vs. RHE. + Faraday efficiency diagram of the product. Detailed Implementation

[0035] To facilitate a correct understanding of the present invention by those skilled in the art, and to enable them to fully understand the technical content of the present invention, the technical solution of the present invention will be further described below in conjunction with specific embodiments. However, this description does not limit the scope of protection claimed by the present invention. Those skilled in the art should not limit the scope of protection of the present invention to the following description. Any equivalent substitutions or changes made by those skilled in the art or those familiar with the art based on the present invention, and based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0036] In particular, the embodiments described below are only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments within a reasonable scope obtained by those skilled in the art based on the embodiments of the present invention without creative effort are part of the present invention.

[0037] This invention creates a method based on existing electrocatalytic reduction of CO2 to C2 under strongly alkaline conditions. + To address the technical problems of low catalyst selectivity and poor stability of the product, a method for preparing a catalytic material is provided. The catalytic material is a copper-based metal-organic framework catalytic material, comprising the following steps:

[0038] (1) Mix divalent copper salt, BIBT (4,7-bis(1H-imidazol-1-yl)-2,1,3-benzothiadiazole) and solvent to obtain a mixture; the mixture should be mixed evenly, either in a high-temperature resistant glass bottle or in other high-temperature resistant mixing equipment. During the mixing process, it can be directly stirred and mixed evenly, or it can be mixed evenly by ultrasonic treatment.

[0039] (2) Heat the mixture to 100-140℃, for example: 100℃, 110℃, 120℃, 130℃ or 140℃, and keep it at a constant temperature for 70-80h, for example: 70h, 72h, 75h, 77h, 79h or 80h, and then cool it down to 20-40℃, for example: 20℃, 22℃, 25℃, 30℃, 35℃, 37℃ or 40℃, to obtain crystals; Before heating, the container containing the mixture in step (1) needs to be sealed, and then the temperature is raised. Through the heating-keeping-cooling process, the copper salt and BIBT organic ligand are promoted to self-assemble through coordination bonds to form a highly ordered porous crystal material.

[0040] (3) The crystals are washed and dried to obtain a copper-based metal-organic framework catalytic material; the crystals obtained in step (2) are washed with ethanol and then dried to obtain the catalyst material; this material can efficiently electrocatalyze the reduction of CO2 to C2.+ Furthermore, this catalytic material maintains structural stability under strongly alkaline conditions (pH=14 or 1M KOH) and exhibits strong electrocatalytic CO2RR and electron transfer capabilities, with high selectivity for electrocatalytic CO2RR products.

[0041] Currently, in existing electrocatalytic CO2RR processes, the reduction products are mostly single-carbon (C1) substances such as CO, HCOOH, and CH4, and C2 is generated through electrocatalytic CO2RR. + The products (e.g., ethanol, ethylene, etc.) require a stable *CO intermediate and promote C-C coupling. This necessitates that two carbon atoms (usually from two different CO2 molecules or their activated intermediates) approach each other on the catalyst surface and form new C-C bonds. This process is kinetically very difficult, leading to C2... + The selectivity of the products is much lower than that of single-carbon (C1) substances, making the electrocatalytic CO2RR technology for the preparation of C2... + The difficulty in producing the product is significantly greater than that in preparing single-carbon (C1) substances. Therefore, this invention, through the aforementioned preparation process and the selection and control of ligands and parameters, synthesizes a material that is structurally stable in an electrolysis system at pH=14, and can suppress side reactions such as hydrogen evolution. It successfully constructs a locally alkaline microenvironment on the catalyst surface, thereby achieving efficient and highly selective C-C coupling, thus providing a solution to the problem of C2… + This study provides new insights into the challenges of product selectivity and catalyst structural stability under strong alkaline conditions.

[0042] In some embodiments of the present invention, the divalent copper salt used is at least one of copper nitrate, copper chloride, and copper sulfate.

[0043] In certain embodiments of this invention, the solvent is an aqueous solution of acetonitrile, and the volume ratio of acetonitrile to water is 4:3; the molar ratio of the divalent copper salt to the BIBT is 0.04-0.06:0.02-0.04, for example: 2:1, 5:2, 3:1, 4:3, 5:3, 10:5, 1:1, 5:4, or 3:2, etc., and the molar volume ratio (mmol / mL) of the divalent copper salt to acetonitrile is 1-1.5:80, for example: 1:80, 1.2:80, 1.3:80, or 1.5:80, etc.; the heating time is 12 hours, and the cooling time is 36 hours.

[0044] In some embodiments of the present invention, the molar ratio of the divalent copper salt to the BIBT is 0.05:0.025, and the molar volume ratio (mmol / mL) of the divalent copper salt to acetonitrile is 1:80.

[0045] In some embodiments of the present invention, the isothermal reaction time is 72 hours.

[0046] In some embodiments of the present invention, the temperature of the isothermal reaction is 120°C, and the cooling is reduced to 30°C.

[0047] In some embodiments of the present invention, the washing is performed using ethanol. Each wash uses a mixture of crystals and ethanol at a mass-to-volume ratio of 1:5, followed by filtration.

[0048] In some embodiments of the present invention, the drying is performed at 60°C for 12 hours.

[0049] Following the above process steps, process parameters, and ligand selection, a copper-based organic framework catalytic material was prepared. This material can electrocatalyze the reduction of CO2 to C2 in an electrolyte at pH 14. + The product yield has a Faraday efficiency ≥ 59.8%. Specifically, its application in electrocatalytic carbon dioxide reduction involves placing the catalytic material as a catalyst in a liquid-phase flow cell; reducing CO2 to C2 in a KOH solution at pH 14 and a potential of -0.8 to -1.0 V vs. RHE. + The product has a Faraday efficiency ≥ 59.8%. For example... Figure 7 The relationship between potential and Faraday efficiency is shown.

[0050] In order to better verify the technical effects that the technical solution of this invention can bring, the inventors of this invention have carried out the following research.

[0051] Example 1

[0052] 0.05 mmol of Cu(NO3)2•3H2O, 0.025 mmol of BIBT, 4 mL of acetonitrile, and 3 mL of water were added to a heat-resistant glass bottle. The mixture was ultrasonically treated (35 Hz) and stirred until homogeneous, yielding a homogeneous mixture. After sealing the glass bottle, the temperature was first raised to 120 °C for 12 h and maintained at this temperature for 72 h. Then, the temperature was lowered to 30 °C for 36 h to obtain crystals. The crystals were washed with ethanol and dried at 60 °C for 12 h to obtain the Cu-BIBT catalyst. The synthesis reaction process is as follows: Figure 1 As shown, the crystal structure of this catalytic material is as follows: Figure 2 As shown.

[0053] The Cu-BIBT catalyst material obtained in the above examples was tested and found to be:

[0054] like Figure 3 The mid-infrared spectrum shows that metallic Cu coordinates with the BIBT ligand.

[0055] like Figure 4As shown, the powder X-ray diffraction experiment shows that the catalytic material obtained in the above example is crystallized in an orthorhombic crystal system with the following cell parameters: a=14.7125(3) Å, b=16.4137(3) Å, c=7.64512(13) Å, α=γ=β=90°, V=1846.19(6), Z=4.

[0056] like Figure 5 , Figure 6 As shown, the catalytic material obtained in the above embodiments has a three-coordinate asymmetric structure and good acid-base stability. It exhibits excellent stability under alkaline conditions, offering unique advantages, primarily in its inhibition of the hydrogen evolution reaction, promotion of CC coupling, and improved application performance. Specifically, when the catalytic material obtained in the above embodiments is used in electrocatalytic CO2RR under alkaline conditions, it promotes the initial activation of carbon dioxide and proton-coupled electron transfer, inhibiting the hydrogen evolution reaction to some extent, allowing more electrons to be used for carbon dioxide reduction, thereby improving the Faraday efficiency of electrocatalytic CO2RR. Simultaneously, the alkaline environment (pH=14) helps stabilize the key *CO intermediate and increases the *CO coverage on the catalyst surface. Higher *CO coverage creates favorable conditions for CC coupling, thus improving the stability of C2+. + Product selectivity.

[0057] Specifically, when applying the catalytic material obtained in the above embodiments to electrocatalytic CO2RR and testing its electrocatalytic performance, the following procedures were followed:

[0058] The catalytic material obtained in the above embodiments was placed as a catalyst in a liquid-phase flow cell. The electrolyte was a KOH solution (pH=14), and the potential range was as follows: Figure 7 The value varies within the range of -0.8 to -1.1, indicating the electrocatalytic CO2RR to C2 generation process. + The products (e.g., ethylene, ethanol, acetic acid) were compared with existing catalytic materials (prepared according to publicly available technical solutions), and the results are as follows: Figure 7 As shown in the figure and in Table 1 below.

[0059] Table 1. Performance comparison of different catalytic materials as catalysts

[0060] Catalytic materials Electric potential (V vs. RHE) <![CDATA[Faraday efficiency C2 + (%)]]> electrolyte This invention Cu-BIBT -0.8 64 1M KOH This invention Cu-BIBT -0.9 59.8 1M KOH This invention Cu-BIBT -1.0 67 1M KOH This invention Cu-BIBT -1.1 43 1M KOH JXUST-301D -1.0 56 1 M KCl and 0.01 M KOH Cu-PzH -1.0 60 1 M KOH <![CDATA[Cu3-Br]]> -1.1 55.01 0.5MKOH <![CDATA[H-Cu2O@C / N]]> -0.9 59.2 <![CDATA[0.1MKHCO3]]> Cu-ade MOF -1.4 45 <![CDATA[0.1MKHCO3]]>

[0061] According to Table 1 and Figure 7 As shown: Under the reaction conditions of a liquid-phase flow cell and an electrolyte of KOH at pH=14, the electrocatalytic CO2RR reaction produces C2. +During the product process, a Faraday efficiency of ≥59.8% can be achieved at a potential of -0.8 to -1.0V vs. RHE, especially at -1.0V vs. RHE, where the Faraday efficiency reaches 67%. Furthermore, testing showed that at -1.0V vs. RHE, C2... + The product current density reached 322 mA·cm -2 Therefore, the Cu-BIBT catalytic material of the present invention has good electron transfer capability and good carbon dioxide reduction activity.

[0062] For any other matters not covered in this invention, they can be addressed by referring to existing technologies or common knowledge known to those skilled in the art, and by using conventional technical means.

Claims

1. A method for preparing a catalytic material, wherein the catalytic material is a copper-based metal-organic framework catalytic material, characterized in that, Includes the following steps: (1) Mix divalent copper salt, BIBT and solvent to obtain a mixture; (2) Heat the mixture to 100-140℃, react at a constant temperature for 70-80h, and then cool it to 20-40℃ to obtain crystals; (3) The crystals are washed and dried to obtain copper-based metal-organic framework catalytic materials; The solvent is an aqueous solution of acetonitrile, and the volume ratio of acetonitrile to water is 4:3; the molar ratio of the divalent copper salt to the BIBT is 0.04-0.06:0.02-0.04, and the molar volume ratio (mmol / mL) of the divalent copper salt to acetonitrile is 1-1.5:80; the heating time is 12 h, and the cooling time is 36 h.

2. The method for preparing the catalytic material as described in claim 1, characterized in that, The divalent copper salt is at least one of copper nitrate, copper chloride, and copper sulfate.

3. The method for preparing the catalytic material as described in claim 1, characterized in that, The molar ratio of the divalent copper salt to the BIBT is 0.05:0.025, and the molar volume ratio (mmol / mL) of the divalent copper salt to acetonitrile is 1:

80.

4. The method for preparing the catalytic material as described in claim 1, characterized in that, The isothermal reaction time is 72 hours.

5. The method for preparing the catalytic material as described in claim 1 or 4, characterized in that, The isothermal reaction is carried out at a temperature of 120°C, and the cooling is carried out at a temperature of 30°C.

6. The method for preparing the catalytic material as described in claim 1, characterized in that, The washing process uses ethanol, and the drying process is carried out at 60°C for 12 hours.

7. The catalytic material prepared by the method according to any one of claims 1-6, characterized in that, Capable of electrocatalytically reducing CO2 to C2 in an electrolyte solution with pH=14. + The product has a Faraday efficiency of ≥59.8%.

8. The application of the catalytic material prepared by the method according to any one of claims 1-6 in electrocatalytic carbon dioxide reduction.

9. The application as described in claim 8, characterized in that, The catalytic material was placed in a liquid-phase flow cell as a catalyst; CO2 was reduced to C2 in a KOH solution with pH=14 and a potential of -0.8~-1.0V vs. RHE. + The product has a Faraday efficiency of ≥59.8%.

10. The application as described in claim 8 or 9, characterized in that, The reduction of CO2 to C2 is performed at a potential of -1.0V vs. RHE. + The product has a Faraday efficiency of 67%.

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