Method for lithium-mediated synthesis of ammonia by using fluorine-containing metal organic framework material

Abstract

The invention discloses a method for lithium-mediated synthesis of ammonia by using a fluorine-containing metal organic framework material, and the method comprises the following steps: preparing the fluorine-containing metal organic framework material, preparing a fluorine-containing metal organic framework electrode, reacting lithium-mediated synthesis of ammonia, and testing the performance of synthesis of ammonia. Fluorine-containing metal organic framework material lithium-mediated synthesis ammonia is carried out through fluorine-containing metal organic framework material preparation, fluorine-containing metal organic framework electrode preparation, lithium-mediated synthesis ammonia reaction and synthesis ammonia performance test, the fluorine-containing metal organic framework material is designed, and the fluorine-containing metal organic framework material is combined with the high N2 adsorption capacity of the fluorine-containing metal organic framework material and the promotion effect of fluorine atoms on lithium ion transmission. Compared with the prior art, the method has the advantages that the current efficiency and the ammonia yield of lithium-mediated ammonia synthesis are remarkably improved, efficient electrolytic ammonia synthesis can be realized at low temperature and pressure, and the reaction energy consumption and the reaction cost are reduced.

Description

Technical Field

[0001] The present invention relates to the field of ammonia synthesis, and in particular to a method for using a fluorine-containing metal organic framework material to synthesize ammonia through lithium mediation. Background Art

[0002] Ammonia, as an important chemical raw material, has a wide range of applications in agriculture, chemical industry, energy, and other fields. Currently, the Haber-Bosch process is the primary method for synthesizing ammonia in industry. This process uses nitrogen and hydrogen as raw materials, reacting under high temperature, high pressure, and an iron-based catalyst. However, the Haber-Bosch process has drawbacks such as high energy consumption and high carbon emissions, making it incompatible with current requirements for green chemistry and sustainable development.

[0003] In recent years, lithium-mediated ammonia synthesis technology has attracted widespread attention as a potential alternative method. Lithium-mediated electrochemical ammonia synthesis (Li-NRR) has attracted much attention due to its ability to react at room temperature and pressure. However, existing lithium-mediated ammonia synthesis systems have several problems. The lithium metal anode is easily passivated, resulting in low current efficiency, low nitrogen solubility, limited mass transfer, low reaction efficiency, and unstable lithium metal activity. These factors lead to low current efficiency and ammonia yield in lithium-mediated ammonia synthesis. Summary of the Invention

[0004] The object of the present invention is to provide a method for using a fluorine-containing metal organic framework material for lithium-mediated synthesis of ammonia, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for using a fluorinated metal organic framework material for lithium-mediated synthesis of ammonia, the method comprising the following steps:

[0006] S1. Preparation of fluorinated metal organic framework material: A series of preparation work is performed for the purpose of preparing an electrode material for synthesizing ammonia, and ultimately obtaining a fluorinated metal organic framework material. The preparation of the fluorinated metal organic framework material includes the following steps:

[0007] (1) Raw material selection: metal precursor, organic ligand and solvent are selected as the raw materials for preparation, the metal precursor is a suitable metal salt, the organic ligand is an organic ligand containing fluorine element, and the solvent is used to dissolve the raw materials;

[0008] (2) Raw material synthesis: metal salt and organic ligand are added to a solvent in a certain molar ratio, stirred evenly to form a mixed solution, and ultrasonicated until completely dissolved. The mixed solution is transferred to a polytetrafluoroethylene autoclave and subjected to a solvent thermal reaction at a certain temperature. After the reaction is completed, the autoclave is cooled to room temperature, and the fluorinated metal organic framework material crystals are obtained by centrifugation, washing, and drying;

[0009] (3) Material testing: X-ray diffraction technology was used to analyze the crystal structure of the prepared fluorinated metal organic framework material to determine its crystal form and crystallinity. The morphology and microstructure of the material were observed under a microscope. The specific surface area and pore size distribution of the material were determined by nitrogen adsorption-desorption experiments.

[0010] S2. Preparation of fluorinated metal organic framework electrode: The fluorinated metal organic framework material prepared in step S1 is compounded with some materials to make an electrode for electrolysis reaction. The specific steps are as follows:

[0011] (1) Electrode material composite: The prepared fluorinated metal organic framework material is mixed with lithium metal in a certain mass ratio, and composited by mechanical ball milling under the protection of inert gas. During the ball milling process, the pore structure and surface active sites of the fluorinated metal organic framework material can fully contact with the lithium metal to form a uniform composite material. The composite material of fluorinated MOF powder, conductive carbon black and polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added to form a slurry. The slurry is evenly coated on carbon paper or nickel foam current collector, dried at 80°C and pressed into sheets to prepare a working electrode;

[0012] (2) Electrode material testing: The microscopic morphology of the composite material was observed using a microscope to analyze the composite state of the fluorinated metal organic framework material and lithium metal. The element distribution of the composite material was analyzed by energy dispersive X-ray spectroscopy to confirm the dispersion state of lithium metal in the fluorinated metal organic framework material.

[0013] S3. Lithium-mediated ammonia synthesis reaction: A lithium-mediated ammonia synthesis reaction device is constructed, including an electrolytic cell structure and reaction conditions. The electrolytic cell structure includes an anode, a cathode, an electrolyte, and a diaphragm. The anode is a platinum sheet or a carbon rod, the cathode is the fluorine-containing metal-organic framework composite electrode prepared in step S2 above, the electrolyte is a 0.5M LiClO4 tetrahydrofuran solution containing 5 vol% ethanol as a proton source, and the diaphragm is a glass fiber membrane. The lithium-mediated ammonia synthesis reaction is completed under the reaction conditions to obtain synthesized ammonia;

[0014] S4. Ammonia synthesis performance test: The NH3 concentration in the electrolyte is detected by the indophenol blue method or ion chromatography method, the by-product H2 content is analyzed by gas chromatography, the Faraday efficiency is calculated, and the percentage of actual product and theoretical product is obtained, thereby obtaining the ammonia synthesis performance.

[0015] Preferably, the metal salt of the raw material in step S1 is one or more of zinc nitrate hexahydrate, copper nitrate, and cobalt nitrate.

[0016] Preferably, the organic ligand of the raw material in step S1 is a mixture of tetrafluoroterephthalic acid, perfluorobenzenetricarboxylic acid and the conventional ligand 2-methylimidazole, and the fluorine content accounts for 10%-50%.

[0017] Preferably, the solvent of the raw material in step S1 is N,N-dimethylformamide, ethanol or water.

[0018] Preferably, in the step S1, the raw material is ultrasonically treated for 10 minutes until it is completely dissolved, reacted in a polytetrafluoroethylene autoclave at 120-180° C. for 18-24 hours, the precipitate is collected by centrifugation, washed alternately with DMF and ethanol three times, and vacuum dried at 60-70° C. for 12-18 hours.

[0019] Preferably, the microscope used to observe the material in step S1 and step S2 is an electron microscope or a transmission electron microscope.

[0020] Preferably, the mechanical ball milling time in the electrode material composite in step S2 is 2-10 hours, and the ball milling speed is 200-500 rpm.

[0021] Preferably, high-purity N2 is continuously introduced during the electrolysis process in step S3 at a flow rate of 10-13 mL / min in a constant current mode and a current density of 1-10 mA / cm 2 , reaction temperature 25-60℃, normal pressure.

[0022] Preferably, the Faraday efficiency calculation formula is:

[0023]

[0024] Where n is the number of moles of NH3 produced, F is the Faraday constant, and Q is the total charge.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Through the preparation of fluorinated metal organic framework materials, the preparation of fluorinated metal organic framework electrodes, the lithium-mediated ammonia synthesis reaction, and the testing of ammonia synthesis performance, the lithium-mediated ammonia synthesis of fluorinated metal organic framework materials is carried out. The fluorinated metal organic framework materials are designed, and the current efficiency and ammonia yield of the lithium-mediated ammonia synthesis are significantly improved by combining their high N2 adsorption capacity, the promotion effect of fluorine atoms on lithium ion transport, and the ability to inhibit lithium dendrite growth. Efficient electrolytic ammonia synthesis can be achieved at lower temperatures and pressures, reducing reaction energy consumption and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] See also Figure 1 ,

[0030] Example 1

[0031] The present invention provides a method for using a fluorine-containing metal organic framework material for lithium-mediated synthesis of ammonia, the method comprising the following steps:

[0032] S1. Preparation of fluorinated metal organic framework materials: A series of preparation work is performed for the purpose of preparing electrode materials for synthesizing ammonia, and ultimately obtaining fluorinated metal organic framework materials. The preparation of fluorinated metal organic framework materials includes the following steps:

[0033] (1) Raw material selection: metal precursor, organic ligand and solvent are selected as the raw materials for preparation, the metal precursor is a suitable metal salt, the organic ligand is an organic ligand containing fluorine element, and the solvent is used to dissolve the raw materials;

[0034] (2) Raw material synthesis: metal salt and organic ligand are added to a solvent in a certain molar ratio, stirred evenly to form a mixed solution, and ultrasonicated until completely dissolved. The mixed solution is transferred to a polytetrafluoroethylene autoclave and subjected to a solvent thermal reaction at a certain temperature. After the reaction is completed, the autoclave is cooled to room temperature, and the fluorinated metal organic framework material crystals are obtained by centrifugation, washing, and drying;

[0035] (3) Material testing: X-ray diffraction technology was used to analyze the crystal structure of the prepared fluorinated metal organic framework material to determine its crystal form and crystallinity. The morphology and microstructure of the material were observed under a microscope. The specific surface area and pore size distribution of the material were determined by nitrogen adsorption-desorption experiments.

[0036] S2. Preparation of fluorinated metal organic framework electrode: The fluorinated metal organic framework material prepared in step S1 is compounded with some materials to make an electrode for electrolysis reaction. The specific steps are as follows:

[0037] (1) Electrode material composite: The prepared fluorinated metal organic framework material is mixed with lithium metal in a certain mass ratio, and composited by mechanical ball milling under the protection of inert gas. During the ball milling process, the pore structure and surface active sites of the fluorinated metal organic framework material can fully contact with the lithium metal to form a uniform composite material. The composite material of fluorinated MOF powder, conductive carbon black and polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added to form a slurry. The slurry is evenly coated on carbon paper or nickel foam current collector, dried at 80°C and pressed into sheets to prepare a working electrode;

[0038] (2) Electrode material testing: The microscopic morphology of the composite material was observed using a microscope to analyze the composite state of the fluorinated metal organic framework material and lithium metal. The element distribution of the composite material was analyzed by energy dispersive X-ray spectroscopy to confirm the dispersion state of lithium metal in the fluorinated metal organic framework material.

[0039] S3. Lithium-mediated ammonia synthesis reaction: A lithium-mediated ammonia synthesis reaction device is constructed, including an electrolytic cell structure and reaction conditions. The electrolytic cell structure includes an anode, a cathode, an electrolyte, and a diaphragm. The anode is a platinum sheet or a carbon rod, the cathode is the fluorine-containing metal-organic framework composite electrode prepared in step S2 above, the electrolyte is a 0.5M LiClO4 tetrahydrofuran solution containing 5 vol% ethanol as a proton source, and the diaphragm is a glass fiber membrane. The lithium-mediated ammonia synthesis reaction is completed under the reaction conditions to obtain synthesized ammonia;

[0040] S4. Ammonia synthesis performance test: The NH3 concentration in the electrolyte is detected by the indophenol blue method or ion chromatography method, the by-product H2 content is analyzed by gas chromatography, the Faraday efficiency is calculated, and the percentage of actual product and theoretical product is obtained, thereby obtaining the ammonia synthesis performance.

[0041] The metal salt of the raw material in step S1 is zinc nitrate hexahydrate, the organic ligand of the raw material in step S1 is tetrafluoroterephthalic acid, and the fluorine content accounts for 10%, and the solvent of the raw material in step S1 is N,N-dimethylformamide.

[0042] In step S1, the raw material synthesis is ultrasonically treated for 10 minutes until it is completely dissolved, reacted in a polytetrafluoroethylene autoclave at 120° C. for 18 hours, and the precipitate is collected by centrifugation, washed alternately with DMF and ethanol three times, and vacuum dried at 60° C. for 12 hours. The microscope used to observe the material in steps S1 and S2 is an electron microscope.

[0043] The mechanical ball milling time of the electrode material composite in step S2 is 2 hours, the ball milling speed is 200 rpm, and high-purity N2 is continuously introduced during the electrolysis process in step S3 at a flow rate of 10 mL / min, in constant current mode, and a current density of 4 mA / cm 2, reaction temperature 30℃, atmospheric pressure, the Faraday efficiency calculation formula is:

[0044]

[0045] Where n is the number of moles of NH3 produced, F is the Faraday constant, and Q is the total charge.

[0046] Example 2

[0047] The present invention provides a method for using a fluorine-containing metal organic framework material for lithium-mediated synthesis of ammonia, the method comprising the following steps:

[0048] S1. Preparation of fluorinated metal organic framework materials: A series of preparation work is performed for the purpose of preparing electrode materials for synthesizing ammonia, and ultimately obtaining fluorinated metal organic framework materials. The preparation of fluorinated metal organic framework materials includes the following steps:

[0049] (1) Raw material selection: metal precursor, organic ligand and solvent are selected as the raw materials for preparation, the metal precursor is a suitable metal salt, the organic ligand is an organic ligand containing fluorine element, and the solvent is used to dissolve the raw materials;

[0050] (2) Raw material synthesis: metal salt and organic ligand are added to a solvent in a certain molar ratio, stirred evenly to form a mixed solution, and ultrasonicated until completely dissolved. The mixed solution is transferred to a polytetrafluoroethylene autoclave and subjected to a solvent thermal reaction at a certain temperature. After the reaction is completed, the autoclave is cooled to room temperature, and the fluorinated metal organic framework material crystals are obtained by centrifugation, washing, and drying;

[0051] (3) Material testing: X-ray diffraction technology was used to analyze the crystal structure of the prepared fluorinated metal organic framework material to determine its crystal form and crystallinity. The morphology and microstructure of the material were observed under a microscope. The specific surface area and pore size distribution of the material were determined by nitrogen adsorption-desorption experiments.

[0052] S2. Preparation of fluorinated metal organic framework electrode: The fluorinated metal organic framework material prepared in step S1 is compounded with some materials to make an electrode for electrolysis reaction. The specific steps are as follows:

[0053] (1) Electrode material composite: The prepared fluorinated metal organic framework material is mixed with lithium metal in a certain mass ratio, and composited by mechanical ball milling under the protection of inert gas. During the ball milling process, the pore structure and surface active sites of the fluorinated metal organic framework material can fully contact with the lithium metal to form a uniform composite material. The composite material of fluorinated MOF powder, conductive carbon black and polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added to form a slurry. The slurry is evenly coated on carbon paper or nickel foam current collector, dried at 80°C and pressed into sheets to prepare a working electrode;

[0054] (2) Electrode material testing: The microscopic morphology of the composite material was observed using a microscope to analyze the composite state of the fluorinated metal organic framework material and lithium metal. The element distribution of the composite material was analyzed by energy dispersive X-ray spectroscopy to confirm the dispersion state of lithium metal in the fluorinated metal organic framework material.

[0055] S3. Lithium-mediated ammonia synthesis reaction: A lithium-mediated ammonia synthesis reaction device is constructed, including an electrolytic cell structure and reaction conditions. The electrolytic cell structure includes an anode, a cathode, an electrolyte, and a diaphragm. The anode is a platinum sheet or a carbon rod, the cathode is the fluorine-containing metal-organic framework composite electrode prepared in step S2 above, the electrolyte is a 0.5M LiClO4 tetrahydrofuran solution containing 5 vol% ethanol as a proton source, and the diaphragm is a glass fiber membrane. The lithium-mediated ammonia synthesis reaction is completed under the reaction conditions to obtain synthesized ammonia;

[0056] S4. Ammonia synthesis performance test: The NH3 concentration in the electrolyte is detected by the indophenol blue method or ion chromatography method, the by-product H2 content is analyzed by gas chromatography, the Faraday efficiency is calculated, and the percentage of actual product and theoretical product is obtained, thereby obtaining the ammonia synthesis performance.

[0057] The metal salt of the raw material in step S1 is copper nitrate, the organic ligand of the raw material in step S1 is perfluorobenzenetricarboxylic acid, and the fluorine content accounts for 40%, and the solvent of the raw material in step S1 is ethanol.

[0058] In step S1, the raw material synthesis was ultrasonically treated for 10 minutes until completely dissolved, reacted in a polytetrafluoroethylene autoclave at 150° C. for 20 hours, and the precipitate was collected by centrifugation, washed alternately with DMF and ethanol three times, and vacuum dried at 65° C. for 15 hours. The microscope used to observe the material in steps S1 and S2 was a transmission electron microscope.

[0059] The mechanical ball milling time for the electrode material composite in step S2 is 7 hours, the ball milling speed is 300 rpm, and high-purity N2 is continuously introduced during the electrolysis process in step S3 at a flow rate of 12 mL / min, in constant current mode, and a current density of 7 mA / cm 2 , reaction temperature 45 ° C, atmospheric pressure, the Faraday efficiency calculation formula is:

[0060]

[0061] Where n is the number of moles of NH3 produced, F is the Faraday constant, and Q is the total charge.

[0062] Example 3

[0063] The present invention provides a method for using a fluorine-containing metal organic framework material for lithium-mediated synthesis of ammonia, the method comprising the following steps:

[0064] S1. Preparation of fluorinated metal organic framework materials: A series of preparation work is performed for the purpose of preparing electrode materials for synthesizing ammonia, and ultimately obtaining fluorinated metal organic framework materials. The preparation of fluorinated metal organic framework materials includes the following steps:

[0065] (1) Raw material selection: metal precursor, organic ligand and solvent are selected as the raw materials for preparation, the metal precursor is a suitable metal salt, the organic ligand is an organic ligand containing fluorine element, and the solvent is used to dissolve the raw materials;

[0066] (2) Raw material synthesis: metal salt and organic ligand are added to a solvent in a certain molar ratio, stirred evenly to form a mixed solution, and ultrasonicated until completely dissolved. The mixed solution is transferred to a polytetrafluoroethylene autoclave and subjected to a solvent thermal reaction at a certain temperature. After the reaction is completed, the autoclave is cooled to room temperature, and the fluorinated metal organic framework material crystals are obtained by centrifugation, washing, and drying;

[0067] (3) Material testing: X-ray diffraction technology was used to analyze the crystal structure of the prepared fluorinated metal organic framework material to determine its crystal form and crystallinity. The morphology and microstructure of the material were observed under a microscope. The specific surface area and pore size distribution of the material were determined by nitrogen adsorption-desorption experiments.

[0068] S2. Preparation of fluorinated metal organic framework electrode: The fluorinated metal organic framework material prepared in step S1 is compounded with some materials to make an electrode for electrolysis reaction. The specific steps are as follows:

[0069] (1) Electrode material composite: The prepared fluorinated metal organic framework material is mixed with lithium metal in a certain mass ratio, and composited by mechanical ball milling under the protection of inert gas. During the ball milling process, the pore structure and surface active sites of the fluorinated metal organic framework material can fully contact with the lithium metal to form a uniform composite material. The composite material of fluorinated MOF powder, conductive carbon black and polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added to form a slurry. The slurry is evenly coated on carbon paper or nickel foam current collector, dried at 80°C and pressed into sheets to prepare a working electrode;

[0070] (2) Electrode material testing: The microscopic morphology of the composite material was observed using a microscope to analyze the composite state of the fluorinated metal organic framework material and lithium metal. The element distribution of the composite material was analyzed by energy dispersive X-ray spectroscopy to confirm the dispersion state of lithium metal in the fluorinated metal organic framework material.

[0071] S3. Lithium-mediated ammonia synthesis reaction: A lithium-mediated ammonia synthesis reaction device is constructed, including an electrolytic cell structure and reaction conditions. The electrolytic cell structure includes an anode, a cathode, an electrolyte, and a diaphragm. The anode is a platinum sheet or a carbon rod, the cathode is the fluorine-containing metal-organic framework composite electrode prepared in step S2 above, the electrolyte is a 0.5M LiClO4 tetrahydrofuran solution containing 5 vol% ethanol as a proton source, and the diaphragm is a glass fiber membrane. The lithium-mediated ammonia synthesis reaction is completed under the reaction conditions to obtain synthesized ammonia;

[0072] S4. Ammonia synthesis performance test: The NH3 concentration in the electrolyte is detected by the indophenol blue method or ion chromatography method, the by-product H2 content is analyzed by gas chromatography, the Faraday efficiency is calculated, and the percentage of actual product and theoretical product is obtained, thereby obtaining the ammonia synthesis performance.

[0073] The metal salt of the raw material in step S1 is a mixture of copper nitrate and cobalt nitrate, the organic ligand of the raw material in step S1 is a mixture of tetrafluoroterephthalic acid, perfluorobenzenetricarboxylic acid and the conventional ligand 2-methylimidazole, and the fluorine content accounts for 50%, and the solvent of the raw material in step S1 is water.

[0074] In step S1, the raw material synthesis is ultrasonically treated for 10 minutes until it is completely dissolved, reacted in a polytetrafluoroethylene autoclave at 180° C. for 24 hours, and the precipitate is collected by centrifugation, washed alternately with DMF and ethanol three times, and vacuum dried at 70° C. for 18 hours. The microscope used to observe the material in steps S1 and S2 is an electron microscope.

[0075] The mechanical ball milling time for the electrode material composite in step S2 is 10 hours, the ball milling speed is 500 rpm, and high-purity N2 is continuously introduced during the electrolysis process in step S3 at a flow rate of 13 mL / min, in constant current mode, and a current density of 10 mA / cm 2 , reaction temperature 60℃, atmospheric pressure, the Faraday efficiency calculation formula is:

[0076]

[0077] Where n is the number of moles of NH3 produced, F is the Faraday constant, and Q is the total charge

[0078] In specific use, the present invention provides a method for using a fluorine-containing metal organic framework material for lithium-mediated ammonia synthesis, wherein lithium-mediated ammonia synthesis of the fluorine-containing metal organic framework material is carried out through preparation of the fluorine-containing metal organic framework material, preparation of a fluorine-containing metal organic framework electrode, lithium-mediated ammonia synthesis reaction, and ammonia synthesis performance testing. The fluorine-containing metal organic framework material is designed, and its high N2 adsorption capacity, the promotion effect of fluorine atoms on lithium ion transmission, and the characteristic of inhibiting lithium dendrite growth are combined to significantly improve the current efficiency and ammonia yield of lithium-mediated ammonia synthesis, and efficient electrolytic ammonia synthesis can be achieved at lower temperature and pressure, thereby reducing reaction energy consumption and cost.

[0079] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for using a fluorinated metal organic framework material for lithium-mediated synthesis of ammonia, characterized in that: The method comprises the following steps: S1. Preparation of fluorinated metal organic framework material: A series of preparation work is performed for the purpose of preparing an electrode material for synthesizing ammonia, and ultimately obtaining a fluorinated metal organic framework material. The preparation of the fluorinated metal organic framework material includes the following steps: (1) Raw material selection: metal precursor, organic ligand and solvent are selected as the raw materials for preparation, the metal precursor is a suitable metal salt, the organic ligand is an organic ligand containing fluorine element, and the solvent is used to dissolve the raw materials; (2) Raw material synthesis: metal salt and organic ligand are added to a solvent in a certain molar ratio, stirred evenly to form a mixed solution, and ultrasonicated until completely dissolved. The mixed solution is transferred to a polytetrafluoroethylene autoclave and subjected to a solvent thermal reaction at a certain temperature. After the reaction is completed, the autoclave is cooled to room temperature, and the fluorinated metal organic framework material crystals are obtained by centrifugation, washing, and drying; (3) Material testing: X-ray diffraction technology was used to analyze the crystal structure of the prepared fluorinated metal organic framework material to determine its crystal form and crystallinity. The morphology and microstructure of the material were observed under a microscope. The specific surface area and pore size distribution of the material were determined by nitrogen adsorption-desorption experiments. S2. Preparation of fluorinated metal organic framework electrode: The fluorinated metal organic framework material prepared in step S1 is compounded with some materials to make an electrode for electrolysis reaction. The specific steps are as follows: (1) Electrode material composite: The prepared fluorinated metal organic framework material is mixed with lithium metal in a certain mass ratio, and composited by mechanical ball milling under the protection of inert gas. During the ball milling process, the pore structure and surface active sites of the fluorinated metal organic framework material can fully contact with the lithium metal to form a uniform composite material. The composite material of fluorinated MOF powder, conductive carbon black and polyvinylidene fluoride are mixed, and N-methylpyrrolidone is added to form a slurry. The slurry is evenly coated on carbon paper or nickel foam current collector, dried at 80°C and pressed into sheets to prepare a working electrode; (2) Electrode material testing: The microscopic morphology of the composite material was observed using a microscope to analyze the composite state of the fluorinated metal organic framework material and lithium metal. The element distribution of the composite material was analyzed by energy dispersive X-ray spectroscopy to confirm the dispersion state of lithium metal in the fluorinated metal organic framework material. S3. Lithium-mediated ammonia synthesis reaction: A lithium-mediated ammonia synthesis reaction device is constructed, including an electrolytic cell structure and reaction conditions. The electrolytic cell structure includes an anode, a cathode, an electrolyte, and a diaphragm. The anode is a platinum sheet or a carbon rod, the cathode is the fluorine-containing metal-organic framework composite electrode prepared in step S2 above, the electrolyte is a 0.5M LiClO4 tetrahydrofuran solution containing 5 vol% ethanol as a proton source, and the diaphragm is a glass fiber membrane. The lithium-mediated ammonia synthesis reaction is completed under the reaction conditions to obtain synthesized ammonia; S4. Ammonia synthesis performance test: The NH3 concentration in the electrolyte is detected by the indophenol blue method or ion chromatography method, the by-product H2 content is analyzed by gas chromatography, the Faraday efficiency is calculated, and the percentage of actual product and theoretical product is obtained, thereby obtaining the ammonia synthesis performance.

2. The method for using a fluorinated metal organic framework material for lithium-mediated synthesis of ammonia according to claim 1, characterized in that: The metal salt used as the raw material in step S1 is one or more of zinc nitrate hexahydrate, copper nitrate, and cobalt nitrate.

3. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: The organic ligand of the raw material in step S1 is a mixture of tetrafluoroterephthalic acid, perfluorobenzenetricarboxylic acid and a conventional ligand 2-methylimidazole, and the fluorine content accounts for 10%-50%.

4. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: The solvent of the raw materials in step S1 is N,N-dimethylformamide, ethanol or water.

5. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: In the step S1, the raw material is subjected to ultrasonic treatment for 10 minutes until it is completely dissolved, reacted in a polytetrafluoroethylene autoclave at 120-180° C. for 18-24 hours, and the precipitate is collected by centrifugation, washed alternately with DMF and ethanol three times, and vacuum dried at 60-70° C. for 12-18 hours.

6. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: The microscope used to observe the material in step S1 and step S2 is an electron microscope or a transmission electron microscope.

7. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: The mechanical ball milling time in the electrode material composite in step S2 is 2-10 hours, and the ball milling speed is 200-500 rpm.

8. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: During the electrolysis process in step S3, high-purity N2 is continuously introduced at a flow rate of 10-13 mL / min, in a constant current mode, and a current density of 1-10 mA / cm 2 , reaction temperature 25-60℃, normal pressure.

9. The method for using a fluorinated metal organic framework material for lithium-mediated ammonia synthesis according to claim 1, characterized in that: The Faraday efficiency calculation formula is: Where n is the number of moles of NH3 produced, F is the Faraday constant, and Q is the total charge.

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