A two-dimensional amorphous copper-based MOF material, its preparation method and application

Abstract

This invention provides a two-dimensional amorphous copper-based MOF material, its preparation method, and its applications. The preparation method includes the following steps: reacting a mixed solution of an organic ligand, a copper salt, and an organic solvent in a closed environment to obtain the two-dimensional amorphous copper-based MOF material. The preparation method provided by this invention can directly synthesize the two-dimensional amorphous MOF material in one step without secondary processing, unlike currently commonly used preparation methods that induce crystal collapse through hydrostatic pressure, heating, mechanical stress, radiation, and discharge. Furthermore, the catalyst obtained from this two-dimensional amorphous MOF material can be used for electrocatalytic CO2 reduction, effectively increasing the carbon content of compounds including ethylene and ethanol. 2+ The product exhibits excellent catalytic activity due to its selectivity. Furthermore, the preparation process is simple to operate, the conditions are easy to control, it has wide applicability, and the yield is high.

Description

Technical Field

[0001] This invention belongs to the field of organometallic complex technology, specifically relating to a two-dimensional amorphous copper-based MOF material, its preparation method, and its application. Background Technology

[0002] In recent years, with the continuous progress of industrial civilization, the massive consumption of fossil fuels has not only triggered an energy crisis but also led to large-scale carbon dioxide emissions, exacerbating environmental problems such as the greenhouse effect and global warming. Currently, since materials that can completely replace fossil fuels cannot be found in the short term, it is necessary to develop efficient, stable, and feasible carbon dioxide conversion technologies to reduce carbon dioxide emissions. Studies have reported that copper-based catalysts can electrocatalytically reduce CO2 into a variety of widely used chemical products under mild conditions. Among these, the multi-carbon products obtained through reduction, such as ethylene and ethanol, have high economic value and energy density, but challenges remain, including the wide distribution of these products and the limited C2 content. 2+ The low product selectivity presents difficulties and challenges. Therefore, optimizing copper-based catalysts is crucial for improving product selectivity and product distribution.

[0003] Metal-organic frameworks (MOFs) are materials with a periodic porous network structure formed by the self-assembly of metal-organic ligands and metal ions through metal-ligand complexation. Due to their tunable pore structure, large specific surface area, and chemical stability, they are widely used in catalysis, pharmaceutical materials, and energy storage. Amorphous MOFs possess the common characteristics of crystalline MOFs, including excellent thermal stability, high surface area, high porosity, and tunable pore structure, while also exhibiting the unique advantages of amorphous materials, such as isotropy, absence of grain boundaries, and abundant defects and active sites. Therefore, compared to crystalline MOFs, amorphous MOFs demonstrate superior performance in catalysis.

[0004] Currently, most amorphous MOF materials are prepared by applying stress to the crystal framework. For example, physical treatments such as hydrostatic pressing and hydrostatic pressing, heating, mechanical stress (ball milling, grinding, etc.), radiation, and discharge have all been applied to crystalline MOF materials to induce their crystal structure collapse; in addition, amorphization chemical treatments can also lead to crystal failure. However, the above preparation methods are complex, generally requiring the preparation of crystalline MOF materials via solvothermal methods, followed by secondary treatment to amorphize the crystalline MOF. Furthermore, the secondary treatment process is quite difficult, often requiring specialized equipment. For example, hydrostatic pressing requires placing the crystalline MOF powder in a diamond anvil cell (DAC) and compressing the sample using a pressureless fluid, methanol-ethanol-water (MEW) isopropanol, or perfluorotripentylamine (FC-70) as a medium; while amorphization methods such as ball milling and grinding provide relatively low mechanical stress, making it difficult to destroy the crystal structure, and are time-consuming, taking up to several weeks, resulting in low efficiency. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a two-dimensional amorphous copper-based MOF material, its preparation method, and its applications. The preparation method allows for the direct one-step synthesis of amorphous MOF materials without secondary processing, and is simple, convenient, and highly efficient.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a two-dimensional amorphous copper-based MOF material, comprising the following steps:

[0008] Two-dimensional amorphous copper-based MOF materials were obtained by reacting a mixed solution of organic ligands, copper salts and organic solvents in a closed environment.

[0009] Preferably, the organic ligand is selected from any one or more of 2-hydroxyterephthalic acid, 2,3-dihydroxybenzoic acid, 2,3-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 4-hydroxybenzoic acid, or p-hydroxybiphenyl acid.

[0010] Preferably, the organic solvent is a mixed solvent of N,N-dimethylformamide and acetonitrile, wherein the volume ratio of N,N-dimethylformamide to acetonitrile is 5:1 to 1:11.

[0011] Preferably, the copper salt is selected from any one or more of Cu(NO3)2, Cu(NO3)2•3H2O, CuSO4, CuSO4•5H2O, CuCl2, CuCl2•2H2O, CuCrO4•2H2O, or CuCr2O7•2H2O.

[0012] Preferably, the molar ratio of copper to organic ligand in the copper salt is 4:1 to 1:13.

[0013] Preferably, the molar ratio of copper to organic ligand in the copper salt is 4:1 to 1:8.

[0014] Preferably, the volume ratio of N,N-dimethylformamide to acetonitrile is 3:1 to 1:6.

[0015] Preferably, the mixed solution of the organic ligand, copper salt and organic solvent is obtained by dissolving the organic ligand and copper salt in the organic solvent.

[0016] Preferably, the dissolution is carried out at a rotation speed of 50~1400 rpm.

[0017] Preferably, the pH value of the mixed solution is 1 to 6.7.

[0018] Preferably, the reaction is carried out at 2~20 °C min. -1 The temperature rises at a rate of 50~220℃.

[0019] Preferably, the reaction is kept at 50~220℃ for 6~72 h.

[0020] Preferably, the reaction is followed by a washing and drying step.

[0021] Secondly, the present invention also provides a two-dimensional amorphous copper-based MOF material prepared by the above preparation method, wherein the two-dimensional amorphous copper-based MOF material is a two-dimensional nanosheet structure.

[0022] Thirdly, the present invention also provides an application of the above-mentioned two-dimensional amorphous copper-based MOF material in electrocatalytic CO2 reduction.

[0023] Preferably, in the electrocatalytic CO2 reduction, the working electrode comprises the above-mentioned two-dimensional amorphous copper-based MOF material.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention provides a one-step method for preparing two-dimensional amorphous copper-based MOF materials. This method utilizes acetonitrile and the carboxyl and hydroxyl groups of organic ligands with metallic Cu. 2+ The competitive coordination of ions leads to the twisting and elongation of the metal-organic framework, which then reacts under high pressure and high temperature conditions to directly self-assemble into a non-periodic metal-organic framework in one step. Therefore, the preparation method provided by this invention can directly synthesize two-dimensional amorphous MOF materials in one step without secondary processing. Compared with currently commonly used preparation methods that induce crystal collapse through hydrostatic pressure, heating, mechanical stress, radiation, and discharge, the steps are simpler and easier to implement, which is conducive to promoting large-scale production.

[0026] Simultaneously, this invention applies the two-dimensional amorphous copper-based MOF material prepared according to this method to a flow cell system for electrocatalytic CO2 reduction. Test results show that, compared with existing MOF materials, the non-periodic structure of this two-dimensional amorphous copper-based MOF material exhibits superior catalytic activity. In particular, this catalyst can effectively increase the C content of ethylene, ethanol, and acetic acid. 2+ Product selectivity, C 2+ The product exhibits a Faraday efficiency as high as 68.7%, which is advantageous among MOF materials. Furthermore, the preparation process is simple to operate, the conditions are easy to control, it has wide applicability, and the yield is high. Attached Figure Description

[0027] Figure 1 The images show the XRD patterns of the copper-based MOF materials obtained in Example 1 and Comparative Examples 1-2; where a corresponds to Example 1, b corresponds to Comparative Example 1, and c corresponds to Comparative Example 2.

[0028] Figure 2 SEM image of the two-dimensional amorphous copper-based MOF material obtained in Example 1;

[0029] Figure 3 TEM image of the two-dimensional amorphous copper-based MOF material obtained in Example 1;

[0030] Figure 4 The image shows the Faraday efficiency of the electrocatalytic CO2 reduction products of the working electrode prepared using the two-dimensional amorphous Cu-based MOF material in Example 1 as the catalyst. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] To address the problems of complex procedures and low efficiency in the preparation of amorphous MOF materials using existing technologies, this invention provides a method for preparing two-dimensional amorphous copper-based MOF materials, comprising the following steps:

[0033] Two-dimensional amorphous copper-based MOF materials were obtained by reacting a mixed solution of organic ligands, copper salts and organic solvents in a closed environment.

[0034] In this invention, the mixed solution of the organic ligand, copper salt, and organic solvent is obtained by dissolving the organic ligand and copper salt in the organic solvent. The mixed solution is a clear solution. The dissolution is preferably carried out under stirring conditions, with a stirring speed of 50-1400 rpm, more preferably 300-1000 rpm, and even more preferably 600-800 rpm; the mixed solution is a strongly acidic solution with a pH value of 1-6.7, preferably 1-4.7. In some embodiments of this invention, after obtaining the mixed solution, the pH value of the reaction solution needs to be measured repeatedly to ensure that the test error is ≤0.2 before proceeding with subsequent reactions.

[0035] In this invention, the copper salt is a salt compound formed by copper ions in the +2 oxidation state and other non-metallic elements (such as oxygen, sulfur, chlorine, etc.). Specifically, in some embodiments of this invention, the copper salt is selected from any one or a mixture of several of the following in any proportion: Cu(NO3)2, Cu(NO3)2•3H2O, CuSO4, CuSO4•5H2O, CuCl2, CuCl2•2H2O, CuCrO4•2H2O, or CuCr2O7•2H2O. This invention does not impose any particular restrictions on the source of the copper salt; commercially available products are acceptable.

[0036] In this invention, the organic ligand is an organic compound that can form a coordinate bond with the central atom of a copper ion or a copper compound and the bond length is adjustable. Specifically, it can be selected from any one or more of 2-hydroxyterephthalic acid, 2,3-dihydroxybenzoic acid, 2,3-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 4-hydroxybenzoic acid, or p-hydroxybiphenyl acid, preferably 2,5-dihydroxyterephthalic acid (abbreviated as DHTA).

[0037] In some embodiments of the present invention, the molar ratio of Cu to organic ligand in the copper salt is 4:1 to 1:13, preferably 4:1 to 1:8, and more preferably 2:1 to 1:5.6.

[0038] In this invention, the organic solvent is a mixture of N,N-dimethylformamide and acetonitrile. The ratio of the two has a significant impact on the structure of the final product. If the proportion of acetonitrile is too low, there will be insufficient cyano groups provided during the coordination complexation process, which cannot adequately compete with the carboxyl and hydroxyl groups provided by DHTA, thus leading to some Cu... 2+It cannot complex with the corresponding functional groups and be directly reduced to elemental Cu. Conversely, an excessively high proportion of acetonitrile will reduce the solubility of DHTA and copper salts in the solvent, resulting in incomplete reaction of the reaction solution during hydrothermal processing. Therefore, in some embodiments of the present invention, the volume ratio of N,N-dimethylformamide to acetonitrile is 5:1 to 1:11, preferably 3:1 to 1:6, and more preferably 3:2 to 1:4.

[0039] In some embodiments of the present invention, it is preferable to disperse and dissolve the copper salt and the organic ligand separately in an organic solvent to obtain a copper salt solution and an organic ligand solution, and then slowly pour the organic ligand solution into the copper salt solution and mix thoroughly to obtain a mixed solution. The composition and amount of the copper salt and the organic ligand, as well as the dissolution parameters, are all as described above and will not be repeated here.

[0040] After obtaining the mixed solution, according to the present invention, the mixed solution is poured into a reaction vessel, preferably a polytetrafluoroethylene reaction vessel, sealed, and placed in a forced-air drying oven, and heated to the target temperature for reaction.

[0041] In some embodiments of the present invention, it is preferred to use 2~20 °C min. -1 More preferably, at 2~15 °Cmin -1 The temperature is increased to 50~220℃ at a rate of [missing information], and the reaction is maintained at this temperature for 6~72 h, preferably at 100~120℃ for 8~48 h.

[0042] According to the present invention, after the reaction is completed, the reaction vessel is naturally cooled to 10~40°C, and then slowly opened to obtain a reddish-brown precipitate.

[0043] The present invention preferably involves washing and drying the obtained reddish-brown precipitate. The washing is preferably performed using ethanol; specifically, the reddish-brown precipitate is washed with ethanol by vacuum filtration, repeated 1 to 5 times.

[0044] The drying can be carried out using methods well known to those skilled in the art. In some embodiments of the present invention, the drying is preferably vacuum drying, the drying temperature is 40~100°C, preferably 60~80°C, and the drying time is 6~48h, preferably 6~24h.

[0045] As can be seen, the preparation method of the above-mentioned two-dimensional amorphous copper-based MOF material provided by the present invention can directly synthesize two-dimensional amorphous MOF material in one step without secondary processing. Compared with the preparation methods that are commonly used at present, such as hydrostatic pressure, heating, mechanical stress, radiation and discharge to induce crystal collapse, the steps are simpler, easier to implement, and more efficient, which is conducive to promoting large-scale production.

[0046] The present invention also provides a two-dimensional amorphous copper-based MOF material prepared according to the above preparation method. The two-dimensional amorphous copper-based MOF material is a two-dimensional nanosheet structure as characterized by SEM and TEM.

[0047] The present invention also provides an application of the above-mentioned two-dimensional amorphous copper-based MOF material in electrocatalytic CO2 reduction.

[0048] Specifically, in some embodiments of the present invention, the two-dimensional amorphous copper-based MOF material is dissolved in isopropanol, and a binder of 1-7 μL / mg (where mg refers to the mass of the two-dimensional amorphous copper-based MOF material) is added, resulting in a final solution concentration of 2-17 mg / mL (referring to the concentration of the two-dimensional amorphous copper-based MOF material in isopropanol). The binder includes any one or more of Nafion solution, sodium alginate, polytetrafluoroethylene micropowder, or polyvinylidene fluoride. The solution is then uniformly coated onto the surface of a gas diffusion electrode, the coating including drop coating, spray coating, blade coating, and spin coating; and then dried at 50-90°C for 1-8 h to obtain a two-dimensional amorphous Cu-based MOF catalyst. The present invention does not impose any particular limitation on the gas diffusion electrode; any material well-known to those skilled in the art can be used, and it can be a commercially available product.

[0049] Furthermore, in the electrocatalytic CO2 reduction system, a three-electrode system is formed using the aforementioned two-dimensional amorphous Cu-based MOF catalyst as the working electrode, nickel foam as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Electrocatalytic CO2 reduction is performed in a flow cell using a constant voltage mode to obtain ethylene, ethanol, and other compounds. 2+ The product includes multiple products. The electrolyte is selected from potassium hydroxide, potassium bicarbonate, sodium bicarbonate, and potassium sulfate; the voltage range of the above constant voltage mode is -0.5 to -2 vs. RHE.

[0050] Testing revealed that the aperiodic structure of the two-dimensional amorphous Cu-based MOF catalyst exhibits superior catalytic activity. In particular, this catalyst can effectively increase the C content of various compounds, including ethylene, ethanol, and acetic acid. 2+ Product selectivity, C 2+ The product has a Faraday efficiency of up to 68.7%.

[0051] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0052] Example 1

[0053] A one-step method for preparing two-dimensional amorphous Cu-based MOF materials includes the following steps:

[0054] (1) Measure 16 mL of N,N-dimethylformamide and acetonitrile respectively, mix them thoroughly to obtain a mixed solution with a total volume of 32 mL, and divide it into two equal parts by volume. Weigh 125.5 mg of Cu(NO3)2•3H2O and 144 mg of DHTA (the molar ratio of Cu to organic ligand DHTA is 1:1.4) and dissolve them in the two mixed solutions respectively. Stir at 600 rpm for 20 min to ensure complete dissolution. These solutions are denoted as solution A (i.e., the Cu(NO3)2•3H2O solution) and solution B (i.e., the DHTA solution). Keep the stirring speed of solution A constant, slowly pour solution B into solution A to mix the two solutions thoroughly. Keep the original stirring speed constant and repeatedly measure the pH value of the solution. When the pH value of the solution is stable at 2.4 and the positive and negative error is ≤0.2, it proves that the reaction solution has become stable and can be used for later use.

[0055] (2) Pour the reaction solution into a 45 mL PTFE reactor, seal it, and place it in a forced-air drying oven. Set the heating rate to 8 °C min. -1 The reaction temperature was 120°C and the reaction time was 24 h.

[0056] (3) After the reaction is complete, allow the reactor to cool naturally to 30°C. Install the filtration apparatus, add a small amount of ethanol to the filter paper, and slowly turn on the vacuum pump to remove some of the air from the filtration flask, so that the filter paper adheres tightly to the bottom of the funnel. Pour the reacted solution into the filtration flask and begin filtration; add an appropriate amount of ethanol to the funnel to wash the precipitate on the filter paper, let it stand for 3 minutes, and then dry it; repeat this washing process 3 times to remove any remaining impurities on the precipitate. Finally, vacuum dry at 80°C for 12 hours to obtain the two-dimensional amorphous Cu-MOF material.

[0057] Example 2

[0058] A one-step method for preparing two-dimensional amorphous Cu-based MOF materials includes the following steps:

[0059] (1) Measure 19.2 mL of N,N-dimethylformamide and 12.8 mL of acetonitrile, mix them thoroughly to obtain a total volume of 32 mL, and divide the mixture into two equal parts by volume. Weigh 82.49 mg of CuSO4•5H2O and 144 mg of DHTA (the molar ratio of Cu to organic ligand DHTA is 1:2.2) and dissolve them in the two mixed solutions. Stir at 800 rpm for 60 min to ensure complete dissolution, and record them as solution A and solution B. Keep the stirring speed of solution A constant, slowly pour solution B into solution A to mix the two solutions thoroughly. Keep the original stirring speed constant and repeatedly measure the pH value of the solution. When the pH value of the solution is stable at 3.2 and the positive and negative error is ≤0.2, it proves that the reaction solution has become stable and can be used for later use.

[0060] (2) Pour the reaction solution into a 45 mL PTFE reactor, seal it, and place it in a forced-air drying oven. Set the heating rate to 8 °C min. -1 The reaction temperature was 80°C, and the reaction time was 48 h.

[0061] (3) After the reaction is complete, allow the reactor to cool naturally to 30°C. Install the filtration apparatus, add a small amount of ethanol to the filter paper, and slowly turn on the vacuum pump to remove some of the air from the filtration flask, so that the filter paper adheres tightly to the bottom of the funnel. Pour the reacted solution into the filtration flask and begin filtration; add an appropriate amount of ethanol to the funnel to wash the precipitate on the filter paper, let it stand for 3 minutes, and then dry it; repeat this washing process 3 times to remove any remaining impurities on the precipitate. Finally, vacuum dry at 80°C for 12 hours to obtain the two-dimensional amorphous Cu-MOF material.

[0062] Example 3

[0063] A one-step method for preparing two-dimensional amorphous Cu-based MOF materials includes the following steps:

[0064] (1) Measure 8 mL of N,N-dimethylformamide and 24 mL of acetonitrile, mix them thoroughly to obtain a total volume of 32 mL, and divide the mixture into two equal portions. Weigh 206.53 mg of CuCl2•2H2O and 144 mg of DHTA (the molar ratio of Cu to the organic ligand DHTA is 1:0.6) and dissolve them in the two portions of the mixture. Stir at 600 rpm for 60 min to ensure complete dissolution, and record these as solution A and solution B. Keep the stirring speed of solution A constant, slowly pour solution B into solution A to mix the two portions thoroughly. Keep the original stirring speed constant and repeatedly measure the pH value of the solution. When the pH value of the solution stabilizes at 2.67 and the positive and negative error is ≤0.2, it proves that the reaction solution has become stable and is ready for use.

[0065] (2) Pour the reaction solution into a 45 mL PTFE reactor, seal it, and place it in a forced-air drying oven. Set the heating rate to 10 °C min. -1 The reaction temperature was 100°C and the reaction time was 36 h.

[0066] (3) After the reaction is complete, allow the reactor to cool naturally to 30°C. Install the filtration apparatus, add a small amount of ethanol to the filter paper, and slowly turn on the vacuum pump to remove some of the air from the filtration flask, so that the filter paper adheres tightly to the bottom of the funnel. Pour the reacted solution into the filtration flask and begin filtration; add an appropriate amount of ethanol to the funnel to wash the precipitate on the filter paper, let it stand for 6 minutes, and then dry it; repeat this washing process 3 times to remove any remaining impurities on the precipitate. Finally, vacuum dry at 80°C for 24 hours to obtain the two-dimensional amorphous Cu-MOF material.

[0067] Example 4

[0068] A one-step method for preparing two-dimensional amorphous Cu-based MOF materials includes the following steps:

[0069] (1) Measure 16 mL of N,N-dimethylformamide and 16 mL of acetonitrile respectively, mix them thoroughly to obtain a total volume of 32 mL mixed solution, and divide it into two equal parts by volume; weigh 129.62 mg of CuSO4•5H2O and 144 mg of 2,3-dihydroxyterephthalic acid (the molar ratio of Cu to organic ligand is 1:1.4) and dissolve them in the two mixed solutions respectively, stir at 800 rpm for 60 min to ensure complete dissolution, and record them as solution A and solution B. Keep the stirring speed of solution A unchanged, slowly pour solution B into solution A to mix the two solutions thoroughly; keep the original stirring speed unchanged, repeatedly measure the pH value of the solution. When the pH value of the solution is stable at 2.4 and the positive and negative error is ≤0.2, it proves that the reaction solution has become stable and can be used for later use;

[0070] (2) Pour the reaction solution into a 45 mL PTFE reactor, seal it, and place it in a forced-air drying oven. Set the heating rate to 8 °C min. -1 The reaction temperature was 120°C and the reaction time was 48 h.

[0071] (3) After the reaction is complete, allow the reactor to cool naturally to 30°C. Install the filtration apparatus, add a small amount of ethanol to the filter paper, and slowly turn on the vacuum pump to remove some of the air from the filtration flask, so that the filter paper adheres tightly to the bottom of the funnel. Pour the reacted solution into the filtration flask and begin filtration; add an appropriate amount of ethanol to the funnel to wash the precipitate on the filter paper, let it stand for 3 minutes, and then dry it; repeat this washing process 3 times to remove any remaining impurities on the precipitate. Finally, vacuum dry at 80°C for 12 hours to obtain the two-dimensional amorphous Cu-MOF material.

[0072] Comparative Example 1

[0073] This comparative example provides a Cu-based MOF material, including the following steps:

[0074] 125.5 mg of Cu(NO3)2•3H2O and 144 mg of DHTA were dissolved in 32 mL of N,N-dimethylformamide and stirred at 800 rpm for 20 min until fully dissolved. The reaction solution was poured into a 45 mL PTFE reactor, sealed, and placed in a forced-air drying oven. The heating rate was set to 8 °C / min. -1 The reaction temperature was 120°C, and the reaction time was 24 h. After the reaction, the reactor was allowed to cool naturally to 30°C. A vacuum filtration apparatus was installed, and a small amount of ethanol was added to the filter paper. The vacuum pump was slowly turned on to remove some air from the filtration flask, ensuring the filter paper adhered tightly to the bottom of the funnel. The reacted solution was poured into the filtration flask, and filtration began. A suitable amount of ethanol was added to the funnel to wash the precipitate on the filter paper. The mixture was allowed to stand for 3 minutes, and then dried under vacuum. This washing process was repeated three times to remove any remaining impurities from the precipitate. Finally, the mixture was vacuum dried at 80°C for 12 h to obtain a two-phase mixture containing crystalline Cu (e.g., ...). Figure 1 Curve b in the figure.

[0075] Comparative Example 2

[0076] This comparative example provides a Cu-based MOF material (using 2-aminoterephthalic acid as an organic ligand), comprising the following steps:

[0077] 125.5 mg of Cu(NO3)2•3H2O and 144 mg of 2-aminoterephthalic acid were dissolved in a mixed solution containing 16 mL of N,N-dimethylformamide and 16 mL of acetonitrile. The solution was stirred at 600 rpm for 20 min until fully dissolved. The reaction mixture was poured into a 45 mL PTFE reactor, sealed, and placed in a forced-air drying oven. The heating rate was set to 8 °C / min. -1The reaction temperature was 120°C, and the reaction time was 24 h. After the reaction, the reactor was allowed to cool naturally to 30°C. The precipitate obtained after the reaction was washed with ethanol by vacuum filtration three times, and then dried under vacuum at 80°C for 12 h to obtain crystalline Cu-based MOF material (e.g., Figure 1 (Curve c in the text).

[0078] In this invention, the two-dimensional amorphous Cu-MOF materials prepared in Examples 1 to 4 above have similar structures and properties. The following uses Example 1 as an example to characterize and test the performance of the prepared two-dimensional amorphous Cu-MOF material.

[0079] XRD tests were performed on the two-dimensional amorphous Cu-MOF material obtained in Example 1 and the Cu-based MOF materials obtained in Comparative Examples 1 and 2. The results are as follows: Figure 1 As shown. Among them, Figure 1 Curve a in the figure is the XRD pattern of the two-dimensional amorphous Cu-MOF material obtained in Example 1. Figure 1 Curve b in the figure is the XRD pattern of the Cu-based MOF material obtained in Comparative Example 1. Figure 1 Curve c in the figure is the XRD pattern of the Cu-based MOF material obtained in Comparative Example 2. Figure 1 As can be seen from curve a, no diffraction peaks appear, proving that the material has an amorphous structure. Figure 1 curve a in Figure 1 Comparing curves b and c, it can be seen that the absence of acetonitrile in the organic solvent, or the use of other organic ligands, will affect the crystal structure of Cu-MOF materials.

[0080] The two-dimensional amorphous Cu-MOF material obtained in Example 1 was characterized by SEM and TEM. The results are as follows: Figures 2-3 As shown.

[0081] By SEM ( Figure 2 ) and TEM ( Figure 3 It can be observed that the prepared amorphous Cu-MOF material is a two-dimensional nanosheet.

[0082] Evaluation of electrocatalytic CO2 reduction performance:

[0083] An electrode prepared using the two-dimensional amorphous Cu-MOF material obtained in Example 1 as a catalyst was used as the working electrode. A three-electrode system was formed, with nickel foam as the counter electrode and an Ag / AgCl electrode as the reference electrode. A 1 M KOH alkaline solution was used as the electrolyte, and electrocatalytic CO2 reduction was performed in a flow cell using a constant voltage mode. The applied potential range was -0.5 to -2 vs. RHE, specifically -0.55 V, -0.75 V, -0.95 V, -1.15 V, -1.35 V, -1.55 V, -1.75 V, and -1.95 V. After electrolysis for a period of time, the reacted gases were collected using a sealed gas bag. The gaseous products were detected using gas chromatography, and the liquid products were detected using liquid nuclear magnetic resonance spectroscopy.

[0084] Figure 4 This is a Faraday efficiency diagram of the products obtained from the electrocatalytic CO2 reduction of the two-dimensional amorphous Cu-MOF material in Example 1. Analysis shows that when the electrocatalytic CO2 reduction test was conducted in the potential range of -0.55 to -1.95 V vs. RHE, the products obtained were ethylene, ethanol, acetic acid, carbon monoxide, hydrogen, formic acid, and methane. Among these, ethylene, ethanol, and acetic acid contain C... 2+ The Faraday efficiency of the product can reach 68.7%. Compared with Example 1, under the same conditions, Comparative Examples 1 and 2 mainly produced C1 products such as carbon monoxide, formic acid, and methane during electrocatalytic CO2 reduction. 2+ The product content is low, indicating that the materials obtained in Comparative Examples 1 and 2 perform worse as working electrodes than the two-dimensional amorphous Cu-MOF materials provided in the Examples.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a two-dimensional amorphous copper-based MOF material, characterized in that, Includes the following steps: Two-dimensional amorphous copper-based MOF materials were obtained by reacting a mixed solution of organic ligands, copper salts and organic solvents in a closed environment. The organic ligand is selected from any one or more of 2-hydroxyterephthalic acid, 2,3-dihydroxybenzoic acid, 2,3-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 4-hydroxybenzoic acid or p-hydroxybiphenyl acid; The molar ratio of copper to organic ligand in the copper salt is 4:1 to 1:13; The organic solvent is a mixture of N,N-dimethylformamide and acetonitrile, wherein the volume ratio of N,N-dimethylformamide to acetonitrile is 5:1 to 1:

11. The mixed solution of the organic ligand, copper salt and organic solvent is obtained by dissolving the organic ligand and copper salt in the organic solvent; The dissolution is carried out at a rotation speed of 50~1400 rpm; The pH value of the mixed solution is 1~6.7; The reaction is carried out at 2~20 °C min. -1 The temperature rises at a rate of 80~120℃; The reaction was kept at 80-120°C for 24-48 h.

2. The preparation method according to claim 1, characterized in that, The copper salt is selected from any one or more of Cu(NO3)2, Cu(NO3)2•3H2O, CuSO4, CuSO4•5H2O, CuCl2, CuCl2•2H2O, CuCrO4•2H2O, or CuCr2O7•2H2O.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of copper to organic ligand in the copper salt is 4:1 to 1:

8.

4. The preparation method according to claim 1, characterized in that, The volume ratio of N,N-dimethylformamide to acetonitrile is 3:1 to 1:

6.

5. The preparation method according to claim 1, characterized in that, The reaction is followed by washing and drying steps.

6. A two-dimensional amorphous copper-based MOF material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The two-dimensional amorphous copper-based MOF material has a two-dimensional nanosheet structure.

7. The application of the two-dimensional amorphous copper-based MOF material prepared by the preparation method of any one of claims 1 to 5 or the two-dimensional amorphous copper-based MOF material of claim 6 in electrocatalytic CO2 reduction.

8. The application according to claim 7, characterized in that, In the electrocatalytic CO2 reduction, the working electrode comprises a two-dimensional amorphous copper-based MOF material prepared by any one of claims 1 to 5 or a two-dimensional amorphous copper-based MOF material as described in claim 6.

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