Synthesis method and application of a polyazacyclo-copper material

Abstract

This invention provides a method for synthesizing polynitrogen heterocyclic carbene copper materials and their applications, overcoming the shortcomings of existing methods that produce polynitrogen heterocyclic carbene copper complexes with mostly irregular morphologies. This invention achieves the controllable construction of rod-shaped, sheet-like, and spherical polynitrogen heterocyclic carbene copper materials through a universal method. Firstly, molecules with benzyl bromide groups are used as linkers, imidazole molecules as monomers, and acetonitrile or 1,4-dioxane as solvent I. Through the coordination between different types of linkers, monomers, and solvent I, the growth rates v in the x, y, and z directions are effectively controlled during the quaternization and self-assembly process of the linkers and monomers. x v y v z It is possible to controllably prepare polyimide salts in the form of rods, sheets, or spheres; then, under the protection of an inert atmosphere, using the polyimide salt as a backbone, the imidazole salt is deprotonated and coordinated with the copper salt under alkaline conditions to controllably construct rod-shaped, sheet-shaped, or spherical polyazo heterocyclic carbene copper materials.

Description

Technical Field

[0001] This invention belongs to the field of novel electrocatalytic materials technology, specifically relating to a method for synthesizing polynitrogen heterocyclic carbene copper materials and their applications. Background Technology

[0002] The efficient removal of alkyne impurities from olefin feedstocks is a prerequisite for promoting the high-end development of downstream polyolefin products. Under the "dual carbon" strategy, electrocatalytic alkyne semi-hydrogenation, which utilizes clean and renewable electricity as a driving force and water as a hydrogen source under ambient temperature and pressure, is a promising olefin impurity removal technology.

[0003] Catalytic materials, as the core component of electrocatalytic semi-hydrogenation systems, play a crucial role in suppressing side reactions and promoting the semi-hydrogenation of alkynes to alkenes. Currently, copper-based catalysts are the main materials used in electrocatalytic alkyne semi-hydrogenation, with copper-based molecular catalysts attracting widespread attention due to their well-defined structures and precisely tunable reaction pathways. However, molecular catalysts typically operate at relatively low current densities (<200 mA / cm²). 2 Electrocatalysis is required. Therefore, there is an urgent need to construct copper-based molecular catalytic materials for the electrocatalytic semi-hydrogenation of alkynes at high current densities.

[0004] Polynitrogen heterocyclic carbene copper complexes possess advantages such as strong electron-donating properties, strong metal affinity, and good conjugation stability, enabling them to firmly coordinate copper sites through metal-carbon bonds. They hold promise for stable and efficient catalysis at high current densities. However, most currently prepared polynitrogen heterocyclic carbene copper complexes exhibit irregular morphologies. The electrocatalytic performance of these irregularly shaped complexes as catalytic materials cannot meet the increasingly demanding performance requirements and remains to be improved.

[0005] Based on this, the present invention provides a method for synthesizing polynitrogen heterocyclic carbene copper materials with high electrocatalytic performance and controllable morphology. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing methods that produce polynitrogen heterocyclic carbene copper complexes with mostly irregular morphologies. This invention provides a method for synthesizing polynitrogen heterocyclic carbene copper materials and their applications. This method enables controllable construction of polynitrogen heterocyclic carbene copper materials, has broad applicability, and the prepared polynitrogen heterocyclic carbene copper materials can achieve high current densities (500 mA / cm²). 2 Highly efficient electrocatalytic semi-hydrogenation of alkynes to alkenes.

[0007] To achieve the above objectives, the technical solution provided by this invention is:

[0008] A method for synthesizing a polynitrogen heterocyclic carbene copper material, characterized by the following steps:

[0009] 1) Using molecules with benzyl bromide groups as linkers, imidazole molecules as monomers, and acetonitrile or 1,4-dioxane as solvent I, the growth rates v in three different directions (x, y, z) are effectively controlled during the quaternization and self-assembly process of linkers and monomers through the coordination between different types of linkers, monomers, and solvent I. x v y v z Polyimide salts in rod, flake, or spherical form can be controlled to be prepared.

[0010] When v x >>v y =v z When v is present, rod-shaped polyimide salts are formed; when v is present, rod-shaped polyimide salts are formed. x ≥v y >>v z When v x =v y =v z At this time, spherical polyimide salts are formed;

[0011] 2) Under an inert atmosphere, using the polyimidazolium salt obtained in step 1) as a framework, the imidazolium salt is deprotonated and coordinated with the copper salt under alkaline conditions to controllably construct rod-shaped, sheet-shaped or spherical polyazo-heterocyclic carbene copper materials.

[0012] The purpose of using alkaline conditions here is to perform deprotonation without affecting the skeletal structure. The base used in the alkaline conditions is potassium carbonate, potassium tert-butoxide, or 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0013] Furthermore, in step 1), when preparing the rod-shaped polyimide salt:

[0014] The linker is 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), the monomer is 1,3,5-triimidazolylbenzene, solvent I is acetonitrile, and the reaction temperature is 50-120℃;

[0015] When preparing sheet-like polyimide salts:

[0016] The linker is 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), the monomer is di(1H-imidazol-1-yl)methane, solvent I is 1,4-dioxane, and the reaction temperature is 50-120℃;

[0017] When preparing spherical polyimide salts:

[0018] The linker is 1,3,5-tris(4-bromomethylphenyl)benzene, the monomer is 1,3,5-triimidazolylbenzene or di(1H-imidazo-1-yl)methane, solvent I is acetonitrile or 1,4-dioxane, and the reaction temperature is 50-120℃.

[0019] The reaction temperature should be selected between 50-120℃. If the temperature is too high, the reaction will be too fast and irregular products will be formed; if the temperature is too low, it will not be conducive to the quaternization reaction.

[0020] Further, in step 1), the molar ratio of the linker to the monomer is 1:1 to 2:3;

[0021] The ratio of the raw material to solvent I is 1:20-200, mmol / mL; the amount of raw material here refers to the total amount of linker and monomer.

[0022] The reaction time is 15–48 hours.

[0023] Furthermore, in step 2), solvent II used is tetrahydrofuran, methanol, or acetone;

[0024] The copper salts used are copper halides, cuprous halides, or copper nitrates;

[0025] The ratio of copper salt, solvent II, and alkali used is 9:50:5, mmol / mL / mmol;

[0026] The reaction temperature is 25–50℃;

[0027] The reaction time is 24–48 hours;

[0028] The inert atmosphere is nitrogen or argon.

[0029] The present invention also provides a polynitrogen heterocyclic carbene copper material with controllable morphology prepared by the above synthesis method, the morphology of which can be rod-shaped, sheet-shaped or spherical.

[0030] Furthermore, this invention also provides the application of the above-mentioned morphology-controllable polynitrogen heterocyclic carbene copper material as a catalyst in the electrocatalytic preparation of olefins from alkynes.

[0031] Based on the above applications, the present invention also provides a method for preparing olefins, which is characterized by including the following steps:

[0032] S1. The polynitrogen heterocyclic carbene copper material with controllable morphology prepared by the above synthesis method is uniformly dispersed in solvent III as a catalyst material to obtain a catalyst material slurry;

[0033] S2. The catalytic material slurry obtained in S1 is uniformly coated onto the gas diffusion layer (the gas diffusion layer is placed on a flat plate material), and after being fully dried, it is used as a cathode for later use.

[0034] S3. The cathode and anode obtained in S2 are matched to form an electrolytic cell, and the cathode electrolyte and the anode electrolyte are isolated by an ion exchange membrane. The alkyne raw material is subjected to an electrocatalytic semi-hydrogenation reaction to prepare olefins.

[0035] Further, in S1, the solvent III is water, ethanol, isopropanol, acetone, or a mixture of water and ethanol, isopropanol, or acetone in any proportion;

[0036] The ratio of the catalytic material to solvent III is 1–100:0.2–50, mg / mL.

[0037] Furthermore, in S2, the gas diffusion layer is 5% polytetrafluoroethylene, which is placed on a flat plate material, the material of which is carbon fiber paper, carbon fiber woven fabric, non-woven fabric or carbon black paper.

[0038] The catalytic material slurry is uniformly coated onto the gas diffusion layer by spraying.

[0039] In S3, the anode is prepared by loading the anode material onto the anode current collector through spraying, dipping, or electrodeposition; the anode material is a non-precious metal (Fe, Co, Ni, etc.) or its alloy or composite; the anode current collector is a copper current collector, a nickel current collector, a titanium current collector, carbon paper, or carbon cloth; alternatively, nickel plates, nickel sheets, or nickel foam can be used directly as the anode, and the thickness of the nickel plate, nickel sheet, or nickel foam is 0.05–1.0 mm.

[0040] The alkyne feedstock is either gaseous or liquid.

[0041] Among them, the gaseous alkyne raw materials are acetylene, propyne or butyne;

[0042] Liquid alkyne feedstock is a liquid compound containing a carbon triple bond.

[0043] Furthermore, in the S3 electrocatalytic process, gaseous alkyne feedstock enters from the gas chamber inlet of the electrolytic cell, and olefins are collected from the gas chamber outlet;

[0044] Alternatively, the liquid alkyne feedstock and the cathode electrolyte are mixed and introduced into the cathode chamber inlet, while the olefins are collected from the cathode chamber outlet; wherein the liquid alkyne feedstock and the cathode electrolyte are mixed at a volume ratio of 1:1 to 1:199.

[0045] During electrocatalysis, the flow rate of the gaseous alkyne feedstock is 1–100 sccm, the flow rate of the cathode electrolyte is 1–100 sccm, and the flow rate of the anolyte is 1–100 sccm.

[0046] The flow rate of the liquid after mixing the liquid alkyne feedstock with the cathode electrolyte is 1–100 sccm, and the flow rate of the anolyte is 1–100 sccm.

[0047] Furthermore, the cathode electrolyte and anolyte are acidic, neutral, or alkaline liquid electrolytes, or solid electrolytes, such as: 0.01–5M hydrochloric acid, 0.01–5M sulfuric acid, 0.01–5M KCl solution, 0.01–10M KHCO3 solution, or 0.01–10M KOH solution.

[0048] The advantages of this invention are:

[0049] 1. This invention achieves the controllable construction of rod-shaped, sheet-shaped, and spherical polynitrogen heterocyclic carbene copper materials through a universal method. First, using molecules with benzyl bromide groups as linkers, imidazole molecules as monomers, and acetonitrile or 1,4-dioxane as solvents, rod-shaped, sheet-shaped, and spherical polyimidazolium salts are controllably synthesized through the coordination between different types of linkers, monomers, and solvents during the quaternization and self-assembly process of the linkers and monomers. Then, under an inert atmosphere (argon or nitrogen), the polyimidazolium salts synthesized in an alkaline environment are deprotonated in situ and coordinated with copper to prepare rod-shaped, sheet-shaped, and spherical polynitrogen heterocyclic carbene copper. This material is a polymer with controllable morphology, which is significantly different from commercial carbene copper.

[0050] 2. This invention further applies the controllable construction of polynitrogen heterocyclic carbene copper. A gas diffusion electrolyzer is assembled using a gas diffusion electrode supported on polynitrogen heterocyclic carbene copper catalyst material as the cathode, a non-noble metal-based catalyst material as the anode, and an ion exchange membrane (anion exchange membrane) or a proton exchange membrane as the separator between the cathode and anode. Electrochemical performance tests confirm that the polynitrogen heterocyclic carbene copper catalyst material of this invention can achieve highly efficient electrocatalytic acetylene semi-hydrogenation, significantly superior to other molecular-based catalyst materials. The current density of electrocatalysis with other molecular catalyst materials is <200 mA / cm². 2 Compared to other materials, the polynitrogen heterocyclic carbene copper material prepared in this invention can achieve high current densities (500 mA / cm²). 2 This invention enables highly efficient electrocatalytic semi-hydrogenation of alkynes to alkenes. More importantly, the polynitrogen heterocyclic carbene copper catalyst developed in this invention possesses a clear and simple structure, which is a crucial foundation for further clarifying the active center and reaction mechanism of polynitrogen heterocyclic carbene copper catalysts in electrocatalysis. It also provides new insights for the widespread application of polynitrogen heterocyclic carbene copper materials in electrocatalysis. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating the universal preparation method of the polynitrogen heterocyclic carbene copper material of the present invention.

[0052] Figure 2 The synthetic route diagram for rod-shaped IOP-NHC Cu;

[0053] Figure 3 Synthetic route diagram for rod-shaped PIS-1-NHC Cu;

[0054] Figure 4 Synthetic route diagram for sheet-like PIS-2-NHC Cu;

[0055] Figure 5 Synthetic route diagram for spherical POP-NHC Cu;

[0056] Figure 6 Scanning electron microscope (SEM) images of rod-shaped, sheet-shaped, and spherical polynitrogen heterocyclic carbene copper materials; where a represents rod-shaped, b represents sheet-shaped, c represents spherical, and d represents irregular morphology.

[0057] Figure 7 Rod-shaped polyimide salts and rod-shaped polyazo heterocyclic carbene copper 13 C solid NMR.

[0058] Figure 8 The figures show the polarization curves and Faraday efficiency distributions of rod-shaped polynitrogen heterocyclic carbene copper as the cathode material; where a is the polarization curve and b is the Faraday efficiency distribution. Detailed Implementation

[0059] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0060] This invention provides a universal preparation method for polynitrogen heterocyclic carbene copper catalytic materials, such as... Figure 1 As shown, it includes the following steps:

[0061] 1) Using molecules with benzyl bromide groups as linkers, imidazole molecules as monomers, and acetonitrile or 1,4-dioxane as solvent I, the growth rates v in three different directions (x, y, z) are effectively controlled during the quaternization and self-assembly process of linkers and monomers through the coordination between different types of linkers, monomers, and solvent I. x v y v z Polyimide salts in rod, flake, or spherical form can be controlled to be prepared.

[0062] When v x >>v y =v z When v is present, rod-shaped polyimide salts are formed; when v is present, rod-shaped polyimide salts are formed. x ≥v y >>v z When v x =v y =v z At this time, spherical polyimide salts are formed;

[0063] 2) Under an inert atmosphere, using the polyimidazolium salt obtained in step 1) as the backbone, the imidazolium salt is deprotonated and coordinated with the copper salt under alkaline conditions to controllably construct rod-shaped, sheet-shaped or spherical polyazo-heterocyclic carbene copper materials; the base used in the alkaline conditions is potassium carbonate, potassium tert-butoxide or 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0064] The following examples demonstrate how this method can be used to construct polynitrogen heterocyclic carbene copper materials with controllable morphologies, including rod-shaped (IOP-NHC Cu, PIS-1-NHC Cu), sheet-shaped (PIS-2-NHCCu), and spherical (POP-NHC Cu) materials. Using a gas diffusion electrode loaded with polynitrogen heterocyclic carbene copper catalytic material as the cathode, highly efficient electrocatalytic semi-hydrogenation of alkynes under high current density was achieved.

[0065] The synthesis of the above-mentioned rod-shaped polynitrogen heterocyclic carbene copper (IOP-NHC Cu) is as follows: Figure 2 As shown:

[0066] 0.0588 g of 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), 2.0276 g of 1,3,5-triimidazolylbenzene (TImB), and 40 mL of acetonitrile (CH3CN) were added to a flask. The reaction temperature was controlled at 100 °C and the reaction was carried out for 24 h. The product was centrifuged three times with acetonitrile and dried under vacuum to obtain white rod-shaped polyimidazolium salt (IOP).

[0067] Weigh 20 mg of polyimidazolium salt (IOP), 15 mg of copper chloride dihydrate (CuCl2·2H2O) and 5 mg of potassium tert-butoxide and add them sequentially to 5 mL of anhydrous methanol. Stir at room temperature for 24 h under argon protection. Centrifuge the resulting product three times with methanol and dry it under vacuum to obtain rod-shaped IOP-NHC Cu.

[0068] The synthesis of the above-mentioned rod-shaped polynitrogen heterocyclic carbene copper (PIS-1-NHC Cu) is as follows: Figure 3 As shown:

[0069] At 85°C, 2 mL of acetonitrile solution containing 0.0222 g of bis(1H-imidazol-1-yl)methane (BIM) was added to 3 mL of acetonitrile solution containing 0.0588 g of 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT). The mixture was stirred for 15 h, and the product was collected by centrifugation. The product was then dried under vacuum to obtain white linear (can be considered as rod-shaped) polyimidazolium salt (PIS-1).

[0070] Take 20 mg PIS-1, 15 mg copper chloride dihydrate (CuCl2·2H2O) and 5 mg potassium tert-butoxide and add them sequentially to 5 mL of anhydrous methanol. Stir at room temperature for 24 h under argon protection. Centrifuge the obtained product three times with methanol and dry it under vacuum to obtain rod-shaped PIS-1-NHC Cu.

[0071] The synthesis of the above-mentioned sheet-like polynitrogen heterocyclic carbene copper (PIS-2-NHC Cu) is as follows: Figure 4 As shown:

[0072] At 85°C, 2 mL of a 1,4-dioxane solution containing 0.0222 g of bis(1H-imidazol-1-yl)methane (BIM) was added to 3 mL of a 1,4-dioxane solution containing 0.0588 g of 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT) and stirred for 24 h. The product was collected by centrifugation and dried under vacuum to obtain a sheet-like white polyimidazolium salt (PIS-2).

[0073] 20 mg PIS-2, 15 mg copper chloride dihydrate (CuCl2·2H2O) and 5 mg potassium tert-butoxide were added sequentially to 5 mL of anhydrous methanol. The mixture was stirred at room temperature for 24 h under argon protection. The resulting product was centrifuged three times with methanol and dried under vacuum to obtain flake-like PIS-2-NHC Cu.

[0074] The synthesis of the above-mentioned spherical polynitrogen heterocyclic carbene copper (POP-NHC Cu) is as follows: Figure 5 As shown:

[0075] 0.0588 g of 1,3,5-tris(4-bromomethylphenyl)benzene (BbbT), 0.0276 g of 1,3,5-triimidazolylbenzene (TImB), and 40 mL of acetonitrile (CH3CN) were added to a flask. Under argon protection, the reaction temperature was controlled at 100 °C and the reaction was carried out for 24 h. The product was centrifuged three times with 15 mL of acetonitrile and dried under vacuum to obtain white spherical polyimidazolium salt (POP).

[0076] 20 mg POP, 15 mg copper chloride dihydrate (CuCl2·2H2O) and 5 mg potassium tert-butoxide were added sequentially to 5 mL of anhydrous methanol. The mixture was stirred at room temperature for 24 h under argon protection. The resulting product was centrifuged three times with 15 mL of methanol and dried under vacuum to obtain spherical POP-NHC Cu.

[0077] like Figure 6 As shown, this method can be used to obtain morphologically controllable a-rod-shaped, b-sheet-shaped, and c-spherical polynitrogen heterocyclic carbene copper.

[0078] like Figure 7As shown, compared to polyimidazolium salts (IOP), polynitrogen heterocyclic carbene copper (IOP-NHC Cu) has a higher C content. 13 The solid-state NMR spectrum showed a characteristic peak of carbene carbon-copper bond at 184 ppm, indicating the successful synthesis of polynitrogen heterocyclic carbene copper.

[0079] In addition, the present invention can also prepare the target product according to other coordination methods between the linker, monomer and solvent I given above, and can obtain polynitrogen heterocyclic carbene copper materials of the corresponding shape.

[0080] Comparative example:

[0081] 0.0588 g of 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), 0.0276 g of 1,3,5-triimidazolylbenzene (TImB), and 20 mL of 1,4-dioxane were added to a flask. The reaction temperature was controlled at 100 °C under argon protection, and the reaction was carried out for 24 h. The product was centrifuged three times with 15 mL of 1,4-dioxane and dried under vacuum to obtain an irregularly shaped polyimidazolium salt (IOP-1).

[0082] 10 mg IOP-1, 5 mg copper chloride dihydrate (CuCl2·2H2O), and 3 mg potassium tert-butoxide were sequentially added to 5 mL of anhydrous methanol. The mixture was stirred at room temperature for 24 h under argon protection. The resulting product was centrifuged three times with 15 mL of methanol and dried under vacuum to obtain IOP-1-NHC Cu with an irregular morphology. Figure 6 As shown in d.

[0083] It is evident that the polynitrogen heterocyclic carbene copper catalyst needs to be constructed in a controllable manner according to the aforementioned coordination method.

[0084] To verify the performance of the above-mentioned products, the present invention conducted the following application tests on the catalytic material according to the following process parameters:

[0085] Preparation of the cathode electrode:

[0086] Accurately weigh a certain mass (1-100 mg) of the catalyst powder (rod-shaped, sheet-shaped, and spherical polynitrogen heterocyclic carbene copper material) synthesized above, disperse it in a certain volume (0.2-50 mL) of solvent (the solvent is water, ethanol, isopropanol, acetone, or a mixture of water and ethanol, isopropanol, or acetone in any proportion) to obtain a catalyst slurry;

[0087] A gas diffusion layer (5% polytetrafluoroethylene) was placed on a flat plate. A certain volume (50–500 μL) of catalyst slurry was accurately measured and uniformly sprayed onto the gas diffusion layer. After thorough drying, a gas diffusion electrode loaded with polynitrogen heterocyclic carbene copper was prepared as the cathode, with a catalyst loading of 0.1–10 mg / cm³.2 .

[0088] The aforementioned flat panel materials include, but are not limited to: carbon paper (such as carbon fiber paper), carbon cloth (carbon fiber woven cloth), non-woven fabric, or carbon black paper, etc.

[0089] Preparation of the anode electrode:

[0090] Anodes are prepared by loading non-precious metals (Fe, Co, Ni, etc.) or their alloys or composites onto an anode current collector through methods such as spraying, impregnation, or electrodeposition; or, nickel plates, nickel sheets, or nickel foam are used directly as anodes.

[0091] Anode current collectors include, but are not limited to: copper current collectors, nickel current collectors, titanium current collectors, carbon paper, carbon cloth, etc.

[0092] Assembly and electrochemical performance testing of a gas diffusion electrolyzer:

[0093] Assembly of a gas diffusion electrolyzer:

[0094] A gas diffusion electrode supported on polynitrogen heterocyclic carbene copper catalyst, prepared as described above, is used as the cathode and matched with the aforementioned non-noble metal-based anode. The cathode electrolyte and anolyte are separated by an anion / cation exchange membrane. The feedstock can be either gaseous or liquid alkyne. In the electrocatalytic semi-hydrogenation of alkynes, gaseous alkyne feedstock enters from the gas chamber inlet of the electrolytic cell, and olefins (i.e., the semi-hydrogenation products of alkynes) are collected from the gas chamber outlet. The flow rate of the gaseous alkyne feedstock is 1–100 sccm, the flow rate of the cathode electrolyte is 1–100 sccm, and the flow rate of the anolyte is 1–100 sccm. Liquid alkyne feedstock and cathode electrolyte are mixed and then enter from the cathode chamber inlet, and olefins (i.e., the semi-hydrogenation products of alkynes) are collected from the cathode chamber outlet. The liquid alkyne feedstock and cathode electrolyte are mixed at a volume ratio of 1:1 to 1:199, and the flow rate of the mixed liquid is 1–100 sccm, and the flow rate of the anolyte is 1–100 sccm.

[0095] The gaseous alkyne feedstock is acetylene, propyne, or butyne, or a gaseous mixture of the aforementioned gases with other substances (gaseous olefins, inert gases, etc.);

[0096] Liquid alkyne feedstocks are liquid compounds containing carbon-carbon triple bonds, or liquid mixtures thereof with other substances (such as liquid olefins).

[0097] The cathode electrolyte and anolyte are acidic, neutral, or alkaline liquid electrolytes or solid electrolytes, such as 0.01–5M hydrochloric acid, 0.01–5M sulfuric acid, 0.01–5M KCl solution, 0.01–10M KHCO3 solution, or 0.01–10M KOH solution.

[0098] The electrochemical performance of the electrocatalytic alkyne semi-hydrogenation reaction was tested using an electrochemical workstation. Cyclic voltammetry and linear voltammetry were used to test the catalyst's reactivity, while potentiostatic or galvanostatic methods combined with gas chromatography were used to test the selectivity and stability of the semi-hydrogenation products of the catalyst.

[0099] The following section focuses on specific alkyne compounds, selecting appropriate catalytic materials, and testing the electrocatalytic alkyne semi-hydrogenation performance (activity, Faraday efficiency, and other performance indicators) of the catalytic materials.

[0100]

Example 1

[0101] (1) Carbon paper coated with a certain mass of rod-shaped polyazo heterocyclic carbene copper (IOP-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0102] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0103] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0104] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0105]

Example 2

[0106] (1) Carbon paper coated with a certain mass of rod-shaped polyazo heterocyclic carbene copper (IOP-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0107] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0108] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0109] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 300 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0110]

Example 3

[0111] (1) Carbon paper coated with a certain mass of rod-shaped polyazo heterocyclic carbene copper (PIS-1-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0112] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0113] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0114] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0115]

Example 4

[0116] (1) Carbon paper coated with a certain mass of rod-shaped polyazo heterocyclic carbene copper (PIS-1-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0117] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0118] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0119] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 300 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0120]

Example 5

[0121] (1) Carbon paper coated with a certain mass of sheet-like polyazo heterocyclic carbene copper (PIS-2-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0122] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0123] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0124] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0125]

Example 6

[0126] (1) Carbon paper coated with a certain mass of sheet-like polyazo heterocyclic carbene copper (PIS-2-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0127] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0128] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0129] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 300 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0130]

Example 7

[0131] (1) Carbon paper coated with a certain mass of spherical polyazo heterocyclic carbene copper (POP-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0132] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0133] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0134] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 500 mA / cm². 2Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0135]

Example 8

[0136] (1) Carbon paper coated with a certain mass of spherical polyazo heterocyclic carbene copper (POP-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0137] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0138] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0139] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 300 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0140]

Example 9

[0141] (1) Carbon paper coated with a certain mass of spherical polynitrogen heterocyclic carbene copper (TOP-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0142] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0143] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0144] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0145]

Example 10

[0146] (1) Carbon paper coated with a certain mass of spherical polynitrogen heterocyclic carbene copper (TOP-NHC Cu) was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0147] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0148] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0149] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 300 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0150] Comparative Example 1

[0151] (1) Add 0.0588 g of 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), 0.0276 g of 1,3,5-triimidazolylbenzene (TImB) and 20 mL of 1,4-dioxane to a flask. Under argon protection, control the reaction temperature at 100 °C and react for 24 h. Centrifuge the product three times with 1,4-dioxane and dry it under vacuum to obtain polyimidazolium salt (IOP-1) with irregular morphology.

[0152] Weigh 10 mg of the irregularly shaped IOP-1, 10 mg of copper chloride dihydrate (CuCl2·2H2O) and 3 mg of potassium tert-butoxide and add them sequentially to 5 mL of anhydrous methanol. Stir at room temperature for 24 h under argon protection. Centrifuge the product three times with methanol and dry it under vacuum to obtain the irregularly shaped IOP-1-NHC Cu.

[0153] (2) Carbon paper coated with a certain mass of IOP-1-NHC Cu was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0154] (3) The flow rate of the reaction gas was controlled to be 30 sccm using a gas mass flow meter. The composition of the alkyne compound raw material used in the experiment was: acetylene.

[0155] (4) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0156] (5) The electrocatalytic acetylene semi-hydrogenation performance of the catalyst material was tested using cyclic voltammetry and linear sweep voltammetry at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0157] Comparative Example 2

[0158] (1) Carbon paper coated with a certain mass of rod-shaped polyimidazolium salt (IOP) is used as the cathode of the electrolytic cell; commercial foamed nickel is used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte are 1M KOH solutions, and the cathode and anode are separated by anion exchange membrane.

[0159] (2) The flow rate of the reaction gas was controlled at 30 sccm using a gas mass flow meter. The raw material of the alkyne compound used in the experiment was acetylene.

[0160] (3) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0161] (4) Cyclic voltammetry and linear sweep voltammetry tests were performed on the electrocatalytic acetylene semi-hydrogenation performance of the catalyst material using an electrochemical workstation at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0162] Comparative Example 3

[0163] (1) Weigh 20 mg of rod-shaped polyimidazolium salt (IOP) and 15 mg of copper chloride dihydrate (CuCl2·2H2O) and add them to 5 mL of anhydrous methanol. Stir at room temperature for 24 h under argon protection. Centrifuge the product three times with methanol and dry it under vacuum to obtain rod-shaped polyimidazolium salt copper (IOP-Cu).

[0164] (2) Carbon paper coated with a certain mass of IOP-Cu was used as the cathode of the electrolytic cell; commercial foamed nickel was used as the anode of the electrolytic cell; both the cathode electrolyte and the anode electrolyte were 1M KOH solutions, and the cathode and anode were separated by anion exchange membrane.

[0165] (3) The flow rate of the reaction gas was controlled to be 30 sccm using a gas mass flow meter. The composition of the alkyne compound raw material used in the experiment was: acetylene.

[0166] (4) Use a peristaltic pump to control the flow rate of the cathode electrolyte and the anode electrolyte to 4 sccm.

[0167] (5) The electrocatalytic acetylene semi-hydrogenation performance of the catalyst material was tested using cyclic voltammetry and linear sweep voltammetry at 500 mA / cm². 2 Under current, the types and contents of gaseous products were analyzed by online gas chromatography, and their Faraday efficiency was calculated.

[0168] The specific evaluation results are shown in Table 1 below.

[0169] Table 1

[0170]

[0171]

[0172]

[0173] Table 1 shows a comparison of the electrocatalytic performance of the polynitrogen heterocyclic carbene copper material and the molecular-based catalytic material obtained in this invention. Under the same test conditions, at 500 mA / cm 2 At specific current densities, the ethylene Faradaic efficiency of polynitrogen heterocyclic carbene copper materials (rod-shaped IOP-NHC Cu: 96%; sheet-shaped PIS-2-NHC Cu: 91.4%; spherical TOP-NHC-Cu: 92%) is generally higher than that of other molecular-based catalytic materials (irregularly shaped IOP-1-NHC Cu: 69%; IOP-Cu: 76%). Figure 8 As shown, rod-shaped polynitrogen heterocyclic carbene copper at 100-500 mA / cm 2 Ethylene Faradaic efficiency greater than 95% can be achieved across the entire current density range, with the highest efficiency achieved at a current density of 300 mA / cm². 2 At this time, the ethylene Faradaic efficiency can reach 99%. Meanwhile, the current density used in the electrocatalysis of polynitrogen heterocyclic carbene copper material is significantly higher than the values ​​reported in existing literature. Furthermore, at the same current density, the application potential of polynitrogen heterocyclic carbene copper material is generally lower than that of other molecular-based catalytic materials, saving energy while ensuring ethylene yield. The polynitrogen heterocyclic carbene copper material developed in this invention has a well-defined structure, which lays a good foundation for studying the electrocatalytic active center and reaction mechanism, and also provides new ideas for the application of polynitrogen heterocyclic carbene copper material in the field of electrocatalysis.

[0174] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing a polynitrogen heterocyclic carbene copper material, characterized in that, Includes the following steps: 1) Using molecules with benzyl bromide groups as linkers, imidazole molecules as monomers, and acetonitrile or 1,4-dioxane as solvent I, the growth rates v in three different directions (x, y, z) are effectively controlled during the quaternization and self-assembly process of linkers and monomers through the coordination between different types of linkers, monomers, and solvent I. x v y v z Polyimide salts in rod, flake, or spherical form can be controlled to be prepared. When v x >>v y =v z When v is present, rod-shaped polyimide salts are formed; when v is present, rod-shaped polyimide salts are formed. x ≥v y >>v z When v x =v y =v z At this time, spherical polyimide salts are formed; When preparing rod-shaped polyimide salts: The linker is 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), the monomer is 1,3,5-triimidazolylbenzene, solvent I is acetonitrile, and the reaction temperature is 50-120℃; When preparing sheet-like polyimide salts: The linker is 2,4,6-tris(4-bromomethylphenyl)-1,3,5-triazine (TBPT), the monomer is di(1H-imidazol-1-yl)methane, solvent I is 1,4-dioxane, and the reaction temperature is 50-120℃; When preparing spherical polyimide salts: The linker is 1,3,5-tris(4-bromomethylphenyl)benzene, the monomer is 1,3,5-triimidazolylbenzene or di(1H-imidazo-1-yl)methane, solvent I is acetonitrile or 1,4-dioxane, and the reaction temperature is 50-120℃; The molar ratio of the linker to the monomer is 1:1 to 2:3; The ratio of the raw material to solvent I is 1:20-200 mmol / mL; the amount of raw material here refers to the total amount of linker and monomer. 2) Under an inert atmosphere, using the polyimidazolium salt obtained in step 1) as a framework, the imidazolium salt is deprotonated and coordinated with the copper salt under alkaline conditions to controllably construct rod-shaped, sheet-shaped or spherical polyazo-heterocyclic carbene copper materials. The base used in the alkaline conditions is potassium carbonate, potassium tert-butoxide, or 1,8-diazabicyclo[5.4.0]undec-7-ene.

2. The synthesis method according to claim 1, characterized in that: Step 1), the reaction time is 15-48 hours; In step 2), solvent II used is tetrahydrofuran, methanol, or acetone; The copper salts used are copper halides, cuprous halides, or copper nitrates; The ratio of copper salt, solvent II, and alkali used is 9:50:5 mmol / mL / mmol; The reaction temperature is 25–50℃; The reaction time is 24–48 hours; The inert atmosphere is nitrogen or argon.

3. A polynitrogen heterocyclic carbene copper material with controllable morphology construction, characterized in that: The product is prepared by any of the synthesis methods described in claims 1-2, and its morphology is rod-shaped, sheet-shaped, or spherical.

4. The application of the polynitrogen heterocyclic carbene copper material with controllable morphology as described in claim 3 as a catalyst in the electrocatalytic preparation of olefins from alkynes.

5. A method for preparing an olefin, characterized in that, Includes the following steps: S1. The polynitrogen heterocyclic carbene copper material with controllable morphology prepared by any of the synthesis methods described in claims 1-2 is uniformly dispersed in solvent III as a catalyst material to obtain a catalyst material slurry; S2. The catalyst slurry obtained in S1 is uniformly coated on the gas diffusion layer and dried thoroughly before being used as a cathode. S3. The cathode and anode obtained in S2 are matched to form an electrolytic cell, and the cathode electrolyte and the anode electrolyte are isolated by an ion exchange membrane or a proton exchange membrane. The alkyne raw material is subjected to an electrocatalytic semi-hydrogenation reaction to prepare olefins.

6. The preparation method according to claim 5, characterized in that: In S1, solvent III is water, ethanol, isopropanol, acetone, or a mixture of water and ethanol, isopropanol, or acetone in any proportion; The ratio of the catalytic material to solvent III is 1–100: 0.2–50 mg / mL.

7. The preparation method according to claim 5 or 6, characterized in that: In S2, the gas diffusion layer is 5% polytetrafluoroethylene, which is placed on a flat plate material. The flat plate material is made of carbon fiber paper, carbon fiber woven fabric, non-woven fabric or carbon black paper. The catalytic material slurry is uniformly coated onto the gas diffusion layer by spraying. In S3, the anode is prepared by loading the anode material onto the anode current collector through spraying, dipping, or electrodeposition; the anode material is a non-precious metal or its alloy or composite; the anode current collector is a copper current collector, a nickel current collector, a titanium current collector, carbon paper, or carbon cloth; The alkyne feedstock is either gaseous or liquid. Among them, the gaseous alkyne raw materials are acetylene, propyne or butyne; Liquid alkyne feedstock is a liquid compound containing a carbon triple bond.

8. The preparation method according to claim 7, characterized in that: In the S3 electrocatalytic process, gaseous alkynes enter from the gas chamber inlet of the electrolytic cell, and olefins are collected from the gas chamber outlet. Alternatively, the liquid alkyne feedstock and the cathode electrolyte are mixed and introduced into the cathode chamber inlet, while the olefins are collected from the cathode chamber outlet; wherein the liquid alkyne feedstock and the cathode electrolyte are mixed at a volume ratio of 1:1 to 1:

199. During electrocatalysis, the flow rate of the gaseous alkyne feedstock is 1–100 sccm, the flow rate of the cathode electrolyte is 1–100 sccm, and the flow rate of the anolyte is 1–100 sccm.

9. The preparation method according to claim 8, characterized in that: The cathode electrolyte and anolyte are 0.01–5 M hydrochloric acid, 0.01–5 M sulfuric acid, 0.01–5 M KCl solution, 0.01–10 M KHCO3 solution, or 0.01–10 M KOH solution.

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