Membrane electrode solid electrolyte for electrochemical reduction of CO2 to synthesize pure liquid products and its applications

Abstract

The application relates to the technical field of new energy materials, in particular to a membrane electrode solid electrolyte for synthesizing pure liquid products through electrochemical reduction of CO2 and application thereof. The application discloses a preparation method of a modified MOF-based membrane electrode solid electrolyte, which comprises the following steps: preparing MOF crystals by using zinc nitrate and 2-methyl imidazole, and then performing washing and drying treatment to obtain MOF powder; preparing a polymer prepolymer by using tetrafluoroethylene, perfluoro (vinyl ether), a comonomer and a free radical initiator, and then performing heat treatment to obtain polymer slurry; and performing film forming treatment on a MOF modified mixture obtained by uniformly mixing the MOF powder and the polymer slurry to obtain the modified MOF-based membrane electrode solid electrolyte. The modified MOF-based membrane electrode solid electrolyte can be used for synthesizing pure liquid products through electrochemical reduction of CO2.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to a membrane electrode solid electrolyte (modified MOF-based membrane electrode solid electrolyte) for electrochemical reduction of CO2 to synthesize pure liquid products. Background Technology

[0002] With the acceleration of global industrialization, the massive use of fossil fuels has led to a sharp increase in carbon dioxide (CO2) emissions, triggering serious greenhouse effect and climate change problems. Converting CO2 into valuable chemicals or fuels not only helps reduce greenhouse gas emissions but also provides a sustainable carbon source for the chemical industry. Electrochemical CO2 reduction technology, with its advantages of operating at ambient temperature and pressure, high adjustability, and high product selectivity, has become a cutting-edge field of research and application.

[0003] Electrochemical reduction of CO2 (CO2RR) is a process that converts CO2 into various products (such as formic acid, carbon monoxide, methanol, and ethylene) through electrochemical methods. It involves complex reaction mechanisms and multi-step electron transfer reactions. Traditional electrochemical CO2 reduction technologies mainly employ liquid electrolytes, with gas-liquid interface reactions occurring in H-type electrolytic cells. The CO2 reduction rate is limited by its dissolution rate in the electrolyte, and the current density is generally below -100 mA / cm². -2 To address the gas diffusion problem, a hydrophobic gas diffusion layer is used as the working electrode in a flowing electrolyzer, enabling CO2 reduction at the solid-liquid-gas three-phase liquid interface, thereby increasing the current density to -200 mA / cm². -2 However, the three-phase interface is easily disrupted, making it difficult to maintain the stability of the reaction system.

[0004] To overcome the aforementioned problems, research on solid electrolytes and membrane electrode reactors has gradually emerged. Solid electrolytes possess high ionic conductivity, good mechanical properties, and excellent electrochemical stability, effectively solving the leakage and corrosion problems of liquid electrolytes. Membrane electrode reactors, by combining a catalyst layer and an ion conductor, achieve efficient interfacial mass transfer and charge transport, contributing to improving the rate and selectivity of CO2 reduction reactions. Li et al. (Nature, 2020, 577(7791):509-513) conducted stability tests on CO2 reduction in a membrane electrode electrolyzer. Under a total current of -600 mA, FE... C2H4 The CO2 reduction efficiency reached 64% and remained stable for 190 hours. Although the membrane electrode electrolyzer exhibits better stability compared to a flow electrolyzer, prolonged operation in alkaline anolyte leads to cations in the electrolyte crossing the anion exchange membrane, combining with carbonate ions on the catalyst surface to form salts, which are then deposited at the cathode, thus reducing the CO2 reduction performance. Furthermore, the CO2 reduction products exhibit varying phases, posing a significant challenge to the selectivity of individual products.

[0005] In summary, current electrolytes still face some challenges in the application of electrochemical CO2 reduction and regeneration (CO2RR). Existing technologies mainly use liquid electrolytes, and the products obtained are multiphase with poor selectivity. Against this backdrop, developing a highly efficient and stable MOF (Metal-Organic Frameworks) modified polymer solid electrolyte system for the electrochemical reduction of CO2 to synthesize pure liquid products is particularly important. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-efficiency and stable membrane electrode solid electrolyte system and its application. The present invention achieves a high-efficiency and stable CO2 reduction reaction by optimizing the material selection of the membrane electrode solid electrolyte system.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing a modified MOF-based membrane electrode solid electrolyte (a MOF-based membrane electrode solid electrolyte for electrochemical reduction of CO2 to synthesize pure liquid products), comprising the following steps:

[0008] 1) Dissolve zinc nitrate (zinc nitrate hexahydrate) in methanol to obtain a zinc nitrate solution with a concentration of 0.02M to 0.06M; dissolve 2-methylimidazole in methanol to obtain a 2-methylimidazole solution with a concentration of 0.04M to 0.12M; the molar ratio of zinc nitrate to 2-methylimidazole is 1:2.

[0009] Add 2-methylimidazole solution dropwise to zinc nitrate solution (dropwise time is about 8 to 12 minutes), stir and mix (stirring time is 20 to 40 minutes), and let stand at room temperature for 12 to 24 hours to form MOF crystals;

[0010] The MOF crystals were washed with ethanol (to remove residual reactants—zinc nitrate and 2-methylimidazole, as well as the solvent methanol); the washed MOF crystals were then vacuum dried (in a vacuum drying oven at 60±10℃ for 12±1h) to obtain MOF powder.

[0011] Note: MOF crystals can be separated by centrifugation or filtration;

[0012] 2) Add tetrafluoroethylene and perfluoroethylene ether to the reactor, then add comonomer and free radical initiator to start the polymerization reaction. The polymerization temperature is 70±10℃ and the reaction time is 8±0.5h.

[0013] The polymer prepolymer obtained from the polymerization reaction is heat-treated (to enhance the interaction and stability between its chain segments) to obtain a polymer; then the obtained polymer is dissolved in a solvent to obtain a polymer slurry (for subsequent physical mixing and film formation processes), wherein the polymer concentration in the polymer slurry is 10-20 wt%.

[0014] The molar ratio of tetrafluoroethylene to perfluoroethylene ether is 1:1.

[0015] The molar ratio of tetrafluoroethylene to comonomer is 1:0.1.

[0016] The molar ratio of tetrafluoroethylene to free radical initiator is 1:0.05.

[0017] 3) Add the MOF powder obtained in step 1) to the polymer slurry (polymer matrix) obtained in step 2) and mix evenly to obtain the MOF modified mixture.

[0018] MOF powder: polymer = 10-20 wt%;

[0019] 4) The MOF-modified mixture is coated onto a pre-cleaned substrate to form a thin film; then dried (to remove the solvent), and then dried at 80±10℃ for 12±1h to cure the film (i.e., to completely cure and form a robust solid electrolyte film). Finally, the film is separated from the substrate to obtain the modified MOF-based membrane electrode solid electrolyte.

[0020] Note: Drying can be carried out in a fume hood, allowing the solvent (N-methyl-2-pyrrolidone and any solvent left over from the pretreatment of the substrate) to evaporate slowly until constant weight is achieved, which takes about 1 hour.

[0021] As an improvement to the preparation method of the modified MOF-based membrane electrode solid electrolyte of the present invention, in step 2):

[0022] The comonomer is fluorosulfonic acid, and the free radical initiator is ammonium persulfate;

[0023] The heat treatment was performed by heating at 150±10℃ for 2±0.1h.

[0024] The solvent is NMP (N-methyl-2-pyrrolidone).

[0025] As a further improvement to the preparation method of the modified MOF-based membrane electrode solid electrolyte of the present invention, the uniform mixing in step 3) is to be stirred or ultrasonic treatment (stirring time is about 1 ± 0.2 hours, ultrasonic treatment time is 30 ± 5 minutes).

[0026] As a further improvement to the preparation method of the modified MOF-based film electrode solid electrolyte of the present invention, in step 4), the coating is carried out by spin coating, the spin coater speed is set to 1800-2200 rpm, and the coating time is 25-35 seconds.

[0027] As a further improvement to the preparation method of the modified MOF-based film electrode solid electrolyte of the present invention, in step 4): the substrate is a glass substrate or a silicon substrate, and the substrate is rinsed with acetone, isopropanol and deionized water in sequence to obtain a pre-cleaned substrate.

[0028] As a further improvement to the preparation method of the modified MOF-based membrane electrode solid electrolyte of the present invention, in step 1), the concentration of zinc nitrate solution is 0.02M to 0.04M, and the concentration of 2-methylimidazole solution is 0.04M to 0.08M.

[0029] The present invention also provides the use of the modified MOF-based membrane electrode solid electrolyte prepared by the above method: for CO2 reduction, that is, for electrochemical reduction of CO2 to synthesize pure liquid products.

[0030] As an improvement to the use of the present invention: the modified MOF-based membrane electrode solid electrolyte is sandwiched between the cathode (Ag) and the anode (Pt) to ensure that the modified MOF-based membrane electrode solid electrolyte is in close contact with the electrode; CO2 is electrochemically reduced to formate ions at the cathode.

[0031] The steps for CO2 reduction using the above electrolyte are as follows:

[0032] 1) Sandwich the electrolyte membrane between the cathode (Ag) and the anode (Pt), ensuring tight contact between the membrane and the electrode. Connect the CO2 gas injection system to the gas diffusion electrode (GDE) on the cathode side, and use a gas flow controller to adjust the CO2 flow rate to 20 sccm.

[0033] 2) Place the electrolytic cell in a constant temperature water bath or incubator, setting the temperature to 25±2℃. Connect the cathode and anode to the electrochemical workstation, setting the potential scan range to -1.0V to 0V (relative to the standard hydrogen electrode, SHE), and the scan rate to 10mV / s. Begin introducing CO2 gas, allowing it to pass through the GDE into the cathode chamber, and maintain a stable flow rate. Apply a constant potential to initiate the electrolysis reaction, with a reaction time of 2±0.2h.

[0034] 3) After the reaction is complete, collect the liquid sample in the cathode chamber and analyze it using a mass spectrometer or gas chromatograph.

[0035] The technical advantages of this invention are:

[0036] 1) MOF-based materials have high surface area and abundant pore structure, which improves ion transport efficiency and reduces membrane resistance, thereby improving electrochemical reaction efficiency.

[0037] 2) The MOF and polymer matrix (polymer slurry) are resistant to chemical corrosion and degradation, enhance the mechanical strength of the membrane, and ensure stable use over a long period of time.

[0038] 3) The channels and functional groups of MOF selectively adsorb and transport specific ions or molecules, improving the efficiency of CO2 reduction reaction and the purity of products. Attached Figure Description

[0039] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Figure 1 A schematic diagram of a membrane electrode electrolyzer for the electrochemical reduction of CO2;

[0041] In the diagram: 1. Cathode flow channel plate; 2. Cathode GDE; 3. Solid electrolyte; 4. Anode GDE; 5. Anode flow channel plate. Detailed Implementation

[0042] The embodiments of the present invention will be described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes.

[0043] In this invention:

[0044] Zinc nitrate hexahydrate, also known as zinc nitrate hexahydrate.

[0045] Fluorosulfuric acid, also known as fluorosulfonic acid.

[0046] Example 1: Preparation of solid electrolyte thin films

[0047] 1) Weigh 0.002 mol of zinc nitrate hexahydrate and dissolve it in 100 mL of methanol to obtain a 0.02 M zinc nitrate solution;

[0048] Weigh 0.004 mol of 2-methylimidazole and dissolve it in 100 mL of methanol to obtain a 0.04 M 2-methylimidazole solution.

[0049] Under stirring, 2-methylimidazole solution was slowly added dropwise to zinc nitrate solution (dropwise time was about 10 minutes). After the addition was completed, the mixture was mechanically stirred for 30 minutes. Then the mixture was allowed to stand at room temperature for 12 hours to promote the formation of MOF crystals.

[0050] After the above settling period, the mixture was filtered, and the resulting filter residue (MOF crystals) was washed with ethanol to remove residual reactants (including zinc nitrate and 2-methylimidazole) and solvent (methanol). The washed MOF crystals were then dried in a vacuum drying oven at 60°C for 12 hours to obtain MOF powder (pure MOF powder).

[0051] 2) Add 0.1 mol tetrafluoroethylene and 0.1 mol perfluoroethylene ether to the reactor, add 0.01 mol fluorosulfonic acid as a comonomer, and use 0.005 mol free radical initiator (such as ammonium persulfate) to start the polymerization reaction. The reaction temperature is controlled at 70℃ and the reaction time is 8h to form a polymer prepolymer.

[0052] The polymer prepolymer was heat-treated by heating at 150°C for 2 hours to enhance the intersegmental interactions and stability, thus obtaining the polymer.

[0053] The obtained polymer was dissolved in NMP (N-methyl-2-pyrrolidone) to prepare a polymer slurry with a concentration of 10 wt%, which was used for subsequent physical mixing and film formation processes.

[0054] 3) Gradually add the MOF powder obtained in step 1) to the polymer slurry obtained in step 2) (addition time is about 5 minutes); the amount of MOF powder added is 10 wt% of the polymer mass, and then stir for 1 hour or sonicate for 30 minutes, so that the MOF is uniformly dispersed in the polymer matrix (polymer slurry) to form MOF modified mixture.

[0055] 4) Rinse the glass substrate or silicon substrate sequentially with acetone, isopropanol, and deionized water to obtain a pre-cleaned glass substrate or silicon substrate.

[0056] The MOF-modified mixture obtained in step 3) was uniformly coated onto a pre-cleaned glass or silicon substrate using a spin coater. The spin coater speed was set to 2000 rpm, and the coating time was 30 seconds. The coated substrate was placed in a fume hood to allow the solvent (N-methyl-2-pyrrolidone and any solvent left over from the substrate pretreatment) to evaporate slowly, approximately 1 hour (until the mass of the substrate and the coating material no longer decreased). The coated substrate was then dried in an oven at 80°C for 12 hours to completely cure and form a robust solid electrolyte film. Finally, the film was separated from the substrate phase to obtain the membrane electrode solid electrolyte (approximately 100 μm thick).

[0057] Experiment 1: CO2 Reduction Using Electrolytes

[0058] Figure 1The schematic diagram of the membrane electrode electrolyzer device for electrochemical reduction of CO2 of the present invention can be referred to as “A Visual Cathode Flow Channel Plate Structure and Electrolyzer Structure” in 202311778869.4, which includes a cathode flow channel plate 1, a cathode GDE (cathode gas diffusion layer) 2, a solid electrolyte 3, an anode GDE (anode gas diffusion layer) 4, and an anode flow channel plate 5.

[0059] A cathode flow channel is provided in the cathode flow channel plate 1, an anode flow channel is provided in the anode flow channel plate 5, a membrane electrode solid electrolyte 3 is provided between the cathode GDE2 and the anode GDE4, the cathode flow channel plate 1 is provided on the outer side of the cathode GDE2, and the anode flow channel plate 5 is provided on the outer side of the anode GDE4.

[0060] The cathode (Ag) includes a cathode flow channel plate 1 and a cathode GDE2, and its catalytically active material is Ag; the anode (Pt) includes an anode flow channel plate 1 and an anode GDE2, and its catalytically active material is Pt. An electrolyte membrane (i.e., the membrane electrode solid electrolyte 3) is sandwiched between the cathode (Ag) and the anode (Pt) to ensure close contact between the membrane and the electrode.

[0061] Its working process is as follows:

[0062] 1) The CO2 gas injection system passes through the cathode flow channel plate 1 to the gas diffusion electrode (cathode GDE2) on the cathode side, and uses a gas flow controller to adjust the CO2 flow rate to 20 sccm.

[0063] 2) Place the entire membrane electrode electrolysis cell apparatus in a constant temperature water bath or incubator, setting the temperature to 25℃. Connect the cathode GDE2 and anode GDE4 to the electrochemical workstation, setting the potential scan range to -1.0V to 0V and the scan rate to 10mV / s. Start the CO2 gas flow, allowing it to enter the cathode chamber and maintaining a stable flow rate. Apply a constant potential to initiate the electrolysis reaction. During electrolysis, CO2 is continuously introduced to maintain a stable concentration. CO2 is electrochemically reduced to formate ions at the cathode.

[0064] 3) After the reaction time (2 hours), stop the CO2 inflow and collect the product sample from the cathode. Perform quantitative analysis using mass spectrometry or gas chromatography. The Faraday efficiency of the liquid product is 98%. The product purity is 99%.

[0065] Faraday efficiency calculation formula:

[0066] In the above formula, n is the number of moles of the target product formic acid (HCOOH), which can be quantitatively obtained by mass spectrometry or gas chromatography. F is the Faraday constant, approximately 96485 C / mol. z is the number of electrons required for the formation of the target product in the electrochemical reaction. Q is the total charge, equal to the current I multiplied by the time t, i.e., Q = I × t.

[0067] Product purity calculation formula: Purity = mass of target product (HCOOH) / total mass of all collected products × 100%.

[0068] Example 2, compared to Example 1, makes the following changes:

[0069] Weigh 0.004 mol of zinc nitrate hexahydrate and dissolve it in 100 mL of methanol to obtain a 0.04 M zinc nitrate solution.

[0070] Weigh 0.008 mol of 2-methylimidazole and dissolve it in 100 mL of methanol to obtain 100 mL of methanol with a concentration of 0.08 M.

[0071] The rest is the same as in Example 1.

[0072] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 97.6%, and the product purity was 98%.

[0073] Example 3: The following changes are made compared to Example 1:

[0074] The settling time in step 1) was changed from 12h to 24h, and the rest was the same as in Example 1.

[0075] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 96.8%, and the product purity was 97%.

[0076] Example 4: The following changes are made compared to Example 1:

[0077] Change "preparing a polymer slurry with a concentration of 10 wt%" in step 2) to "preparing a polymer slurry with a concentration of 20 wt%"; the rest is the same as in Example 1.

[0078] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 97.2%, and the product purity was 97%.

[0079] Example 5: The following changes are made compared to Example 1:

[0080] In step 3), the statement "the amount of MOF powder added is 10 wt% of the polymer mass" is changed to "the amount of MOF powder added is 20 wt% of the polymer mass", and the rest is the same as in Example 1.

[0081] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1, and the Faraday efficiency of the liquid product was 95.9%. The product purity was 95%.

[0082] Comparative Example 1, compared to Example 1, is modified as follows:

[0083] Cancel step 2);

[0084] Step 3) is changed to: The MOF powder obtained in step 1) is gradually added to NMP, and the amount of NMP is the same as in Example 1; then the mixture is stirred for 1 hour to form a 10 wt% MOF solution.

[0085] In step 4): spin coating is performed using the above MOF solution, and the rest is the same as in Example 1.

[0086] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 64.2%, and the product purity was 64%.

[0087] Comparative Example 2, compared to Example 1, made the following changes:

[0088] Change "preparing a polymer slurry with a concentration of 10 wt%" in step 2) to "preparing a polymer slurry with a concentration of 1 wt%";

[0089] Change "the amount of MOF powder added is 10 wt% of the polymer mass" in step 3) to "the amount of MOF powder added is 2 wt% of the polymer mass", and the rest is the same as in Example 1.

[0090] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 61.8%, and the product purity was 55%.

[0091] Comparative Example 3, compared to Example 1, made the following changes:

[0092] The phrase "weighing zinc nitrate hexahydrate (0.002 mol) and dissolving it in 100 mL of methanol to obtain a zinc nitrate solution with a concentration of 0.02 M" in step 1) is changed to "weighing zinc nitrate hexahydrate (0.001 mol) and dissolving it in 100 mL of methanol to obtain a zinc nitrate solution with a concentration of 0.01 M", and the rest is the same as in Example 1.

[0093] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 61.5%, and the product purity was 63%.

[0094] Comparative Example 4, compared to Example 1, made the following changes:

[0095] Change "the reaction temperature is controlled at 70°C" in step 2) to "the reaction temperature is controlled at 40°C", and the rest is the same as in Example 1.

[0096] The resulting electrolyte membrane was subjected to CO2 reduction according to Experiment 1. The Faraday efficiency of the liquid product was 48.3%, and the product purity was 39%.

[0097] Experiment 2, Stability Test:

[0098] The membrane electrode solid electrolytes obtained from all the above cases were subjected to the following stability test: a constant potential electrolysis experiment was conducted with the voltage set at -1.0V as in Experiment 1, and the electrolysis time when the current dropped to 80% of the initial current value was recorded, which is the stability time.

[0099] Experiment 3: Mechanical Strength of the Membrane

[0100] The mechanical strength of the membrane electrode solid electrolytes obtained from all the above cases was tested using a tensile testing machine. Test parameters were set, and the samples were stretched at a constant rate (5 mm / min). Stress and strain data were recorded, and the fracture strength of the samples was measured.

[0101] Tensile strength calculation formula:

[0102] Where F is the breaking load, and A is the cross-sectional area (5mm²). 2 )

[0103] Experiment 4: The membrane electrode solid electrolytes obtained from all the above cases were subjected to the following membrane resistance test: The electrochemical workstation was set to electrochemical impedance spectroscopy (EIS) mode, the frequency range of EIS measurement was set to 1Hz to 1MHz, the amplitude was 10mV, the impedance spectrum data were collected at room temperature, and the resistance value R of the sample was obtained by fitting the Nyquist plot or Bode plot.

[0104] The results of experiments 2-4 above are shown in Table 1 below:

[0105] Table 1. Stability, mechanical strength, and membrane resistance of different solid electrolyte membranes

[0106] Experiment 2 (Stability h) Experiment 3 (Tensive Strength in MPa) Experiment 4 (Membrane resistance Ω·cm) Example 1 250 30 50 Example 2 220 28 55 Example 3 210 27 60 Example 4 230 29 53 Example 5 240 28 52 Comparative Example 1 100 15 200 Comparative Example 2 110 22 365 Comparative Example 3 120 21 268 Comparative Example 4 115 23 272

[0107] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a solid electrolyte for a modified MOF-based membrane electrode, characterized in that... Includes the following steps: 1) Dissolve zinc nitrate in methanol to obtain a zinc nitrate solution with a concentration of 0.02M~0.06M; dissolve 2-methylimidazole in methanol to obtain a 2-methylimidazole solution with a concentration of 0.04M~0.12M; the molar ratio of zinc nitrate to 2-methylimidazole is 1:

2. Add 2-methylimidazole solution dropwise to zinc nitrate solution, stir and mix, and let stand at room temperature for 12-24 h to form MOF crystals; The MOF crystals were washed with ethanol; the washed MOF crystals were then dried under vacuum to obtain MOF powder. 2) Add tetrafluoroethylene and perfluoroethylene ether to the reactor, then add comonomer and free radical initiator to start the polymerization reaction. The polymerization temperature is 70±10℃ and the reaction time is 8±0.5 h. The polymer prepolymer obtained from the polymerization reaction is heat-treated to obtain a polymer; then the obtained polymer is dissolved in a solvent to obtain a polymer slurry, wherein the polymer concentration in the polymer slurry is 10-20 wt%. The molar ratio of tetrafluoroethylene to perfluoroethylene ether is 1:

1. The molar ratio of tetrafluoroethylene to comonomer is 1:0.

1. The molar ratio of tetrafluoroethylene to free radical initiator is 1:0.

05. The comonomer is fluorosulfonic acid; 3) Add the MOF powder obtained in step 1) to the polymer slurry obtained in step 2) and mix them evenly to obtain the MOF modified mixture; MOF powder: polymer = 10~20 wt%; 4) The MOF-modified mixture is coated onto a pre-cleaned substrate to form a thin film; then dried, and then cured at 80±10℃ for 12±1h. Finally, the film is separated from the substrate to obtain the modified MOF-based membrane electrode solid electrolyte.

2. The method for preparing the modified MOF-based membrane electrode solid electrolyte according to claim 1, characterized in that... In step 2): The free radical initiator is ammonium persulfate; The heat treatment was performed by heating at 150±10℃ for 2±0.1 h. The solvent is N-methyl-2-pyrrolidone.

3. The method for preparing the modified MOF-based membrane electrode solid electrolyte according to claim 2, characterized in that: The uniform mixing in step 3) is achieved by stirring or ultrasonic treatment.

4. The method for preparing the modified MOF-based membrane electrode solid electrolyte according to claim 2 or 3, characterized in that... In step 4), the coating is done by spin coating, the spin coater speed is set to 1800~2200 rpm, and the coating time is 25~35 seconds.

5. The method for preparing the modified MOF-based membrane electrode solid electrolyte according to claim 4, characterized in that... In step 4), the substrate is a glass substrate or a silicon substrate. The substrate is rinsed with acetone, isopropanol and deionized water in sequence to obtain a pre-cleaned substrate.

6. The method for preparing the modified MOF-based membrane electrode solid electrolyte according to claim 5, characterized in that... In step 1): The concentration of zinc nitrate solution is 0.02M~0.04M, and the concentration of 2-methylimidazole solution is 0.04M~0.08M.

7. The use of the modified MOF-based membrane electrode solid electrolyte prepared by any one of claims 1 to 6, characterized in that: Used for CO2 reduction.

8. The use according to claim 7, characterized in that: The solid electrolyte of the modified MOF-based membrane electrode is sandwiched between the cathode Ag and the anode Pt to ensure close contact between the solid electrolyte and the electrode; CO2 is electrochemically reduced to formate ions at the cathode.

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