A tin-based metal-organic framework catalyst, a preparation method thereof and application thereof in electrocatalysis of co2

Abstract

The application discloses a tin-based metal organic framework catalyst and a preparation method and application thereof in electrocatalysis of CO2, wherein the tin-based metal organic framework catalyst is a zeolitic imidazolate framework-based catalyst doped with tin elements; and metal centers of the tin-based metal organic framework catalyst are coordinated with six nitrogen atoms. Through CO2 electro-reduction test on the prepared catalyst, the results show that a 2% tin-doped Sn-N6-MOF catalyst exhibits superior activity, the selectivity of formic acid in a product can be kept above 75% in a potential range of (-1.1V to -1.4V vs. RHE), and the highest selectivity can reach 85%, and the catalyst has good stability. In the prepared catalyst, the selective CO2 conversion induced by the tin sites in the catalyst makes the catalyst have ideal performance of electro-reduction of CO2 to formic acid. The catalyst provides certain reference for research on catalyst design of MOF materials in electro-reduction of CO2 to formic acid.

Description

Technical Field

[0001] This application relates to a tin-based metal-organic framework catalyst, its preparation method, and its application in electrocatalysis of CO2, belonging to the field of electrochemical catalysis technology. Background Technology

[0002] As concerns about rising atmospheric CO2 levels intensify, the development of various CO2 reduction and conversion technologies has accelerated. Chemical, photochemical, electrochemical, and photoelectrochemical methods aim to convert CO2 into value-added chemical products / fuels and maintain a dynamic carbon cycle balance. Among these technologies, electrocatalytic reduction is one of the most attractive strategies due to its numerous advantages, including mild reaction conditions typically operating at room temperature and atmospheric pressure, recyclable electrolytes, and an environmentally friendly driving force with potential synergy with renewable electricity. However, converting CO2 into desired products via electrocatalytic processes currently faces several challenges: 1) the double bonds in CO2 are difficult to activate due to their short bond lengths; 2) the reaction kinetics are slow; and 3) some side reactions, such as the hydrogen evolution reaction (HER), may reduce Faraday efficiency.

[0003] Metal-organic frameworks (MOFs) are a class of crystalline porous materials with regular framework structures and uniform pores. These materials show great promise for applications in electrochemical CO2 reduction reactions, where their well-defined structure and tunable physical and chemical properties play a crucial role in enhancing reaction performance. Due to the specific metal-ligand periodic spacing of MOFs, the active sites are in a single-atom dispersed state, which further promotes the electroreduction of CO2. Currently, the performance of MOF materials can be improved to some extent through precursor selection, ligand doping, and metal oxide loading. The strategy of doping MOF materials with other metal element nodes to obtain ideal CO2 catalytic reduction performance is also of great interest. Tin, in particular, is widely used in the electrocatalytic reduction of CO2 to prepare formic acid and formate products. Summary of the Invention

[0004] The purpose of this invention is to provide a tin-based metal-organic framework catalyst that can be used for the electrocatalytic reduction of CO2, which exhibits high activity and high formic acid selectivity for the electrocatalytic CO2 reduction reaction.

[0005] This invention synthesizes a hexanitrogen-coordinated tin-based metal-organic framework catalyst. The catalyst of this invention is used for the electrocatalytic CO2 reduction reaction. This catalyst can effectively suppress the hydrogen evolution reaction and exhibits high activity and formic acid production stability.

[0006] One aspect of this application provides a tin-based metal-organic framework catalyst, said tin-based metal-organic framework catalyst being a tin-doped zeolite imidazole framework catalyst.

[0007] The metal center of the tin-based metal-organic framework catalyst is coordinated with six nitrogen atoms.

[0008] Optionally, the tin-based metal-organic framework catalyst has an octahedral particle morphology.

[0009] Another aspect of this application provides a method for preparing a tin-based metal-organic framework catalyst, wherein the preparation method is a combination of ion exchange, in-situ competitive coordination, and solvent-assisted linker exchange.

[0010] Optionally, the preparation method specifically includes:

[0011] (1) A methanol solution containing dimethylimidazole is added dropwise to a methanol solution containing zinc precursor and tin precursor to form solution A. Stirring is performed I, and vacuum drying is performed II to obtain the precursor of the tin-based metal-organic framework catalyst.

[0012] (2) The precursor of the tin-based metal-organic framework catalyst obtained in step (1) is mixed with methanol to form solution B, and 1H-1,2,3-triazole is added; the mixture is stirred and vacuum dried to obtain the tin-based metal-organic framework catalyst.

[0013] Optionally, the zinc precursor is selected from at least one of zinc nitrate, zinc sulfate, and zinc acetate;

[0014] The tin precursor is stannous chloride, or at least one of stannous chloride;

[0015] Optionally, the concentration of the methanol solution containing dimethylimidazole is 0.5–2.0 mol / L;

[0016] The concentration of the methanol solution containing zinc and tin precursors is 0.07–0.13 mol / L, wherein the molar ratio of zinc to tin is 99:1–19:1, based on the molar number of zinc and tin elements.

[0017] In the methanol solution containing zinc and tin precursors, Sn 2+ The molar concentration is 0–5%;

[0018] The molar ratio of dimethylimidazole to the total number of zinc-tin metal ions in solution A is 4–16:1.

[0019] Optionally, the temperature of stirring I is 20–50°C; the stirring time is 2–8 hours.

[0020] The vacuum drying temperature I is 40–80°C, and the vacuum drying time is 6–48 hours.

[0021] Optionally, the concentration of solution B is 0–20 g / L (excluding 0);

[0022] The amount of 1H-1,2,3-triazole added is 0 to 0.2 ml (excluding 0);

[0023] Optionally, the concentration of solution B is 0–12.5 g / L (excluding 0);

[0024] The amount of 1H-1,2,3-triazole added is 0 to 0.15 ml (excluding 0);

[0025] Optionally, the stirring time II is 1 to 72 hours, the vacuum drying temperature II is 40-80°C, and the vacuum drying time II is 6 to 48 hours.

[0026] As one specific embodiment, the preparation method includes:

[0027] 1) Synthesis of tin-based metal-organic framework catalysts coordinated with tetranitrogen (Sn-N4-MOF): Dimethylimidazolium was dissolved in methanol to obtain solution A, and zinc nitrate and stannous chloride were dissolved in methanol to obtain solution B. Solution A was added dropwise to solution B at a suitable temperature, and the mixture was stirred for a certain period of time while maintaining the temperature. The product was then cooled and filtered, washed three times with methanol, and dried under vacuum to obtain a solid product.

[0028] 2) Synthesis of hexanitrogen-coordinated tin-based metal-organic framework catalyst (Sn-N6-MOF): At room temperature, the solid obtained in step 1) was dispersed in methanol to obtain solution C, 1H-1,2,3-triazole was added, stirred, centrifuged, washed three times with methanol and vacuum dried, and the product was collected.

[0029] The catalyst preparation method provided in this statement has mild reaction conditions, is safe and reliable, has low equipment requirements, and all reagents used in the material preparation process are commercial products that do not require further purification. The resulting material is easy to use.

[0030] In another aspect of this application, a working electrode for electrocatalytic reduction of CO2 is provided, the working electrode comprising a substrate and a catalyst on a supported substrate;

[0031] The catalyst is selected from the tin-based metal-organic framework catalysts described above or the tin-based metal-organic framework catalysts prepared according to the preparation method described above.

[0032] Optionally, the catalyst loading on the working electrode is 0.1–2 mg / cm³. 2 ;

[0033] The substrate is selected from at least one of carbon paper, carbon cloth, and carbon felt.

[0034] Optionally, the preparation method of the working electrode includes: taking a certain amount of catalyst and adding it to a mixed solution of isopropanol, water and naphthol for ultrasonic dispersion, uniformly brushing the above solution onto carbon paper, drying it at 70°C, and using the above carbon paper as a working electrode for electrocatalytic reduction of CO2.

[0035] The isopropanol:water ratio in the isopropanol and water mixture is 1:5 to 5:1. The ratio of the catalyst to the isopropanol and water mixture is 0.5 mg to 10 mg: 1 mL. The ratio of naphthol to the isopropanol and water mixture is 1:100 to 1:10. The ultrasonic treatment time for the catalyst is 0.1 to 5 hours.

[0036] Another aspect of this application provides the application of the above-described tin-based metal-organic framework catalyst, or the tin-based metal-organic framework catalyst prepared according to the above-described preparation method, or the above-described working electrode in the electrocatalytic reduction of CO2.

[0037] The beneficial effects that this application can produce include:

[0038] 1) The catalyst of this invention is prepared by ion exchange, in-situ competitive coordination and solvent-assisted linker exchange (SALE) methods, which have low equipment requirements and safe preparation methods.

[0039] 2) The application of the catalyst synthesized in this invention to the electrochemical carbon dioxide reduction reaction is novel, providing new ideas for the design of catalysts for electrocatalytic CO2 reduction in the future.

[0040] 3) The catalyst synthesized in this invention has high activity and selectivity in the electrocatalytic reduction of carbon dioxide to formic acid.

[0041] 4) The catalyst synthesized in this invention exhibits superior activity, with the selectivity for formic acid in the product remaining above 75% in the potential range (-1.1V to -1.4V vs. RHE), reaching a maximum of 85%, and also possesses good stability. In the catalyst prepared in this invention, the selective CO2 conversion induced by tin sites in the catalyst results in ideal electroreduction performance for the production of formic acid from CO2. Attached Figure Description

[0042] Figure 1 The images show the Raman spectra of the catalysts prepared in the examples and Comparative Example 1 of this application.

[0043] Figure 2 The X-ray diffraction patterns are of the catalysts prepared in the embodiments and Comparative Example 2 of this application.

[0044] Figure 3 This is a reaction performance evaluation graph for the catalysts prepared in the examples and Comparative Example 2 of this application. Reaction conditions: room temperature, atmospheric pressure, feed gas: 20 mL / min -1CO2, 0.5M KHCO3 electrolyte. (I: Example; II: Comparative Example 2).

[0045] Figure 4 This is a reaction performance evaluation graph for the catalyst prepared in Comparative Example 1 of this application. Reaction conditions: ambient temperature, ambient pressure, feed gas: 20 mL / min -1 CO2, 0.5M KHCO3 electrolyte.

[0046] Figure 5 This is a SEM image of the catalyst prepared in the embodiments of this application. Detailed Implementation

[0047] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0048] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0049] Comparative Example 1

[0050] A hexanitrogen-coordinated MOF material (0%-Sn-N6-MOF) was synthesized using ion exchange, in-situ competitive coordination, and solvent-assisted linker exchange (SALE) methods: 30 mL of methanol solution containing 1.314 g of dimethylimidazole and 100 mL of methanol solution containing 1.194 g of zinc nitrate were mixed at 40 °C. The mixture was stirred for 4 hours under controlled temperature, cooled, filtered, washed three times with methanol, and dried under vacuum at 60 °C. 1 g of the obtained product was dispersed in 80 mL of methanol, and 0.15 mL of 1H-1,2,3-triazole was added. The mixture was stirred for 72 hours, centrifuged, washed three times with methanol, and dried under vacuum at 60 °C before collecting the product.

[0051] The obtained 0%-Sn-N6-MOF was characterized by Raman spectroscopy using a NanoWizard Raman-Atomic Force Microscopy imaging system. The test results are shown below. Figure 1

[0052] Example

[0053] A hexanitrogen-coordinated tin-doped metal-organic framework (2% Sn-N6-MOF) was synthesized using ion exchange, in-situ competitive coordination, and solvent-assisted linker exchange (SALE) methods: 30 mL of methanol solution containing 1.314 g of dimethylimidazole and 100 mL of methanol solution containing 1.166 g of zinc nitrate and 0.018 g of stannous chloride were mixed at 40 °C. The mixture was stirred for 4 hours under controlled temperature, cooled, filtered, washed three times with methanol, and dried under vacuum at 60 °C. 1 g of the obtained product was dispersed in 80 mL of methanol, and 0.15 mL of 1H-1,2,3-triazole was added. The mixture was stirred for 72 h, centrifuged, washed three times with methanol, and dried under vacuum at 60 °C before collecting the product.

[0054] The obtained 2% Sn-N6-MOF catalyst was characterized by Raman spectroscopy using a NanoWizard Raman-Atomic Force Microscopy (AFM) imaging system. The characterization results are shown below. Figure 1 ,Depend on Figure 1 It can be seen that the 2% Sn-N6-MOF catalyst only exhibits the characteristic Raman peaks of undoped tin MOF materials, rather than the Raman peaks of SnO and SnO2, indicating that the highly dispersed tin only serves as a node in the framework.

[0055] The obtained 2% Sn-N6-MOF catalyst was characterized by X-ray diffraction using an Xpert Pro-1 X-ray powder diffractometer. The test results are shown in [Figure number missing]. Figure 2 After solvent-assisted linker exchange, the metal cation in 2% Sn-N6-MOF coordinates with six nitrogen atoms from the 1H-1,2,3-triazole anion.

[0056] The obtained 2% Sn-N6-MOF catalyst was characterized by scanning electron microscopy (SEM) using a JSM-7800 field emission scanning electron microscope. The test results are shown below. Figure 5 The microstructure of the 2% Sn-N6-MOF catalyst consists of relatively uniform octahedral particles.

[0057] Comparative Example 2

[0058] A tin-doped metal-organic framework (2%-Sn-N4-MOF) with tetranitrogen coordination was synthesized using an ion exchange, in-situ competitive coordination method: 30 ml of methanol solution containing 1.314 g of dimethylimidazole and 100 ml of methanol solution containing 1.166 g of zinc nitrate and 0.018 g of stannous chloride were mixed at 40 °C. The mixture was stirred for 4 hours under controlled temperature, cooled, filtered, washed three times with methanol, and vacuum dried at 60 °C to collect the product.

[0059] Test Example: Catalyst Performance Test

[0060] The 2% Sn-N6-MOF catalyst obtained in the examples, the 0% Sn-N6-MOF catalyst obtained in Comparative Example 1, and the 2% Sn-N4-MOF catalyst obtained in Comparative Example 2 were subjected to cyclic voltammetry scans in a 0.5 mol / L KHCO3 solution under a CO2 atmosphere at a scan rate of 100 mV·s. -1 The scan range was -1.5V to 0V (vs. RHE), with 20 scan cycles. This step cleans the catalyst surface and provides some activation. Subsequently, polarization curves were measured under carbon dioxide and nitrogen atmospheres to characterize the catalyst's electrocatalytic performance, with a scan rate of 10 mV·s. -1The scanning range was -1.5 to 0 V (vs. RHE), and the reaction conditions were: ambient temperature and atmospheric pressure, with a feed gas concentration of 20 mL / min. -1 CO2 and 0.5M KHCO3 electrolyte were used. Constant voltage testing was then performed under a carbon dioxide atmosphere. The feed gas and gaseous products were analyzed online using an Agilent 7890B gas chromatograph equipped with TCD and FID detectors; the collected liquid products were detected by NMR. A calomel electrode was used as the reference electrode and a Pt sheet as the counter electrode for the above scanning range. Test results are shown in […]. Figure 3 (Where I is the 2% Sn-N6-MOF catalyst obtained in the example; II is the 2% Sn-N4-MOF catalyst obtained in Comparative Example 2) Figure 4 ,from Figure 3 It can be seen that the selectivity of the 2% Sn-N6-MOF catalyst for formic acid products initially increases and then decreases with changes in the applied potential. The highest formic acid selectivity of 85.1% is observed at an applied potential of -1.2V; in contrast, the 2% Sn-N4-MOF catalyst only exhibits approximately 55% formic acid selectivity at its dominant potential. Figure 4 It can be seen that the MOF material without tin doping only produces CO and H2 products, and no formic acid is generated, indicating that tin doping is crucial for the formation of formic acid.

[0061] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A tin-based metal-organic framework catalyst, characterized in that, The tin-based metal-organic framework catalyst is a tin-doped zeolite imidazole framework catalyst. The metal center of the tin-based metal-organic framework catalyst is coordinated with six nitrogen atoms.

2. The tin-based metal-organic framework catalyst according to claim 1, characterized in that, The tin-based metal-organic framework catalyst has an octahedral particle morphology.

3. A method for preparing a tin-based metal-organic framework catalyst, characterized in that, The preparation method includes: (1) A methanol solution containing dimethylimidazole is added dropwise to a methanol solution containing zinc precursor and tin precursor to form solution A. Stirring I and vacuum drying II are performed to obtain the precursor of the tin-based metal-organic framework catalyst. (2) The precursor of the tin-based metal-organic framework catalyst obtained in step (1) is mixed with methanol to form solution B, and 1H-1,2,3-triazole is added; stirring II and vacuum drying II are performed to obtain the tin-based metal-organic framework catalyst.

4. The preparation method according to claim 3, characterized in that, The zinc precursor is selected from at least one of zinc nitrate, zinc sulfate, and zinc acetate; The tin precursor is at least one of stannous chloride and stannous chloride.

5. The preparation method according to claim 3, characterized in that, The concentration of the methanol solution containing dimethylimidazole is 0.5~2.0 mol / L; The concentration of the methanol solution containing zinc and tin precursors is 0.07~0.13 mol / L, wherein the molar ratio of zinc to tin is 99:1~19:1, based on the molar number of zinc and tin elements. In solution A, the molar ratio of dimethylimidazole to the total number of zinc-tin metal ions is 4~16:

1.

6. The preparation method according to claim 3, characterized in that, The temperature of stirring I is 20~50℃; the stirring time is 2-8 hours; The vacuum drying temperature is 40~80℃, and the vacuum drying time is 6~48 hours.

7. The preparation method according to claim 3, characterized in that, The concentration of solution B is greater than 0 g / L and less than or equal to 20 g / L; The amount of 1H-1,2,3-triazole added is greater than 0 ml and less than or equal to 0.2 ml; The stirring time II is 1~72 hours, the vacuum drying temperature II is 40-80 ℃, and the vacuum drying time II is 6~48 hours.

8. A working electrode for electrocatalytic reduction of CO2, characterized in that, The working electrode includes a substrate and a catalyst on a supported substrate; The catalyst is selected from the tin-based metal-organic framework catalysts according to any one of claims 1 to 2 or the tin-based metal-organic framework catalysts prepared by the preparation method according to any one of claims 3 to 7.

9. The working electrode according to claim 8, characterized in that, The catalyst loading on the working electrode is 0.1~2 mg / cm³. 2 ; The substrate is selected from at least one of carbon paper, carbon cloth, and carbon felt.

10. The application of a tin-based metal-organic framework catalyst according to any one of claims 1 to 2, or a tin-based metal-organic framework catalyst prepared by the preparation method according to any one of claims 3 to 7, or a working electrode according to any one of claims 8 to 9, in the electrocatalytic reduction of CO2.

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