A catalytic material based on a bimetallic porphyrin covalent organic framework structure and a preparation method and application thereof

Abstract

The application relates to the technical field of electrocatalytic materials, and particularly discloses a catalytic material based on a bimetallic porphyrin covalent organic framework structure and a preparation method and application thereof. By introducing specific nickel / cobalt bimetallic porphyrin units into a covalent organic framework (COF), a high-performance water electrolysis oxygen evolution reaction (OER) catalytic material is successfully prepared. By virtue of the rigid conjugated structure and strong coordination capacity of the porphyrin ring, the nickel / cobalt bimetallic active sites are highly and uniformly dispersed in the framework, and by high-temperature calcination and carbonization, a porous graphite carbon skeleton with a high specific surface area is constructed while the metal-nitrogen active center is retained, so that the conductivity, structural stability and active site availability of the material are significantly enhanced. The composite material exhibits excellent OER catalytic performance and long-term electrochemical stability in an alkaline electrolyte, and exhibits good practical application potential in the field of water electrolysis oxygen evolution.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to a catalytic material based on a bimetallic porphyrin covalent organic framework structure, its preparation method, and its application. Background Technology

[0002] The oxygen evolution reaction (OER) is a core half-reaction in new energy conversion and storage technologies such as water electrolysis for hydrogen production and metal-air batteries. This reaction is a four-electron transfer process, which has inherent problems such as slow kinetics, high reaction energy barrier and large overpotential. Its catalytic efficiency directly determines the energy utilization efficiency of the entire energy conversion system. Therefore, developing efficient, stable and low-cost OER electrocatalysts is the key to promoting the large-scale application of related technologies.

[0003] Currently, commercially available OER electrocatalysts are mainly based on noble metals such as ruthenium and iridium. However, these materials are scarce, have high preparation costs, and exhibit limited stability under strongly alkaline and high-potential catalytic conditions, making them unsuitable for industrial applications. Therefore, researchers have shifted their focus to non-noble metal-based electrocatalysts. Among these, bimetallic organic frameworks (MOFs) have become an important research direction for non-noble metal OER catalysts due to their advantages such as tunable pore structure, high specific surface area, abundant bimetallic active sites, and synergistic catalytic effects. However, the further application of bimetallic MOF electrocatalytic materials is limited by the poor electrical conductivity of the MOF structure itself, the tendency for structural collapse during catalysis, and the failure of metal active sites.

[0004] Therefore, developing a non-precious metal-based catalyst that combines high catalytic activity and long-term stability is of great significance for promoting the large-scale development of new energy conversion and storage technologies such as water electrolysis for hydrogen production and metal-air batteries. Summary of the Invention

[0005] To address the problems of poor conductivity, structural collapse during catalysis, and metal active site failure in existing bimetallic MOF electrocatalytic materials, this invention provides a catalytic material based on a bimetallic porphyrin covalent organic framework structure, its preparation method, and its applications. This invention uses 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt as organic ligands, and prepares a covalent organic framework material with terephthalaldehyde under solvothermal conditions. The covalent organic framework material is then carbonized by high-temperature calcination to obtain the catalytic material based on the bimetallic porphyrin covalent organic framework structure. This catalytic material exhibits excellent electrocatalytic activity and long-term stability, showing promising application prospects in the field of high-performance oxygen evolution electrocatalysis.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a catalytic material based on a bimetallic porphyrin covalent organic framework structure, the preparation method comprising the following steps: S1, a bimetallic porphyrin-based organic ligand and terephthalaldehyde are subjected to a solvothermal reaction in an organic solvent containing an acidic catalyst to obtain a covalent organic framework material; wherein, the bimetallic porphyrin-based organic ligand includes 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt; S2, Under an inert atmosphere, the covalent organic framework material is calcined and carbonized to obtain a catalytic material based on a bimetallic porphyrin covalent organic framework structure.

[0007] Compared to existing technologies, the method for preparing catalytic materials based on a bimetallic porphyrin covalent organic framework structure provided by this invention selects 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt as bimetallic porphyrin-based organic ligands, which are covalently assembled with terephthalaldehyde to construct a bimetallic porphyrin-based covalent organic framework (COF) with a highly ordered π-conjugated structure. The unique cyclic molecular structure of the porphyrin ring provides stable metal-N... x The coordination environment allows the nickel and cobalt bimetallic active sites to be uniformly anchored inside and on the surface of the framework, fundamentally solving the problems of easy migration, aggregation or leaching of metal sites in traditional catalysts, and greatly improving the dispersibility and intrinsic stability of active sites.

[0008] Furthermore, through a high-temperature carbonization process, while effectively preserving the original regular framework structure of the covalent organic framework material, atomically dispersed bimetallic porphyrin units are transformed into stable MN units. x -C active sites construct a highly efficient three-dimensional electron conduction network within the material, thereby significantly reducing charge transfer resistance, accelerating the kinetic rate of the OER reaction, effectively reducing the reaction overpotential, and further improving catalytic efficiency, achieving a dual improvement in active site stability and electron transport rate.

[0009] It should be noted that the 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt described in this invention can be synthesized by conventional methods using 5,10,15,20-tetra(4-aminophenyl)porphyrin and the corresponding metal salt, and this invention does not impose any special limitations.

[0010] As a specific embodiment of the present invention, the preparation method of the catalytic material based on the bimetallic porphyrin covalent organic framework structure specifically includes the following steps: S1, a bimetallic porphyrin-based organic ligand and terephthalaldehyde are dispersed in an organic solvent containing an acidic catalyst. Gases in the system are removed, and a solvothermal reaction is carried out under closed conditions. The mixture is then washed and dried to obtain a covalent organic framework material. The reaction equation is as follows:

[0011] S2, the covalent organic framework material is placed in a tube furnace and calcined and carbonized under an inert atmosphere, then cooled to obtain a catalytic material based on a bimetallic porphyrin covalent organic framework structure.

[0012] Further, in S1, the molar ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt is 1:3 to 3:1.

[0013] Preferably, in S1, the molar ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt is 1:1.

[0014] Within this ratio range, a significant electronic synergistic effect can be generated between the Ni and Co active centers, effectively regulating the overall electronic structure of the material, thereby giving the prepared catalytic material excellent catalytic activity.

[0015] Furthermore, in S1, the molar ratio of the bimetallic porphyrin-based organic ligand to terephthalaldehyde is 1:2 to 1:3.

[0016] Within the aforementioned ratio range, it is beneficial to construct a covalent framework with high integrity and periodicity, thereby improving the conductivity and structural stability of the material.

[0017] Further, in S1, the organic solvent is a mixture of mesitylene and anhydrous ethanol in a volume ratio of 1:1 to 1:3.

[0018] Preferably, in S1, the organic solvent is a mixture of mesitylene and anhydrous ethanol in a volume ratio of 1:1.

[0019] Further, in S1, the acidic catalyst is an acetic acid solution with a concentration of 3 mol / L to 8 mol / L, wherein the molar ratio of CH3COOH to the bimetallic porphyrin-based organic ligand in the acetic acid solution is 20:1 to 70:1.

[0020] Furthermore, in S1, the temperature of the solvothermal reaction is 100℃~150℃, and the reaction time is 24h~72h.

[0021] Specifically, in S1, anhydrous tetrahydrofuran and anhydrous methanol are used for washing, and then the product is dried in a vacuum drying oven at 70℃~90℃.

[0022] Furthermore, in S2, the calcination and carbonization temperature is 800℃~950℃, and the time is 3h~12h.

[0023] Within the aforementioned temperature and time range, the organic components in covalent organic framework materials can effectively undergo graphitization transformation, forming highly conductive sp... 2 The carbon network, at the same time, is sufficient to ensure that the metal-nitrogen (MN) coordination bonds in the metalloporphyrin unit are not completely destroyed, but can be stably and in situ transformed into MN with high OER activity. x -C active sites, thereby significantly improving the electron transport efficiency of the material.

[0024] Secondly, the present invention also provides a catalytic material based on a bimetallic porphyrin covalent organic framework structure, wherein the material is prepared by the preparation method of the catalytic material based on the bimetallic porphyrin covalent organic framework structure described in any one of the above claims.

[0025] Thirdly, the present invention also provides the application of the above-mentioned catalytic materials based on the bimetallic porphyrin covalent organic framework structure in the electrocatalytic oxygen evolution reaction.

[0026] This invention successfully prepared a high-performance catalytic material for the oxygen evolution reaction (OER) in water electrolysis by introducing specific nickel / cobalt bimetallic porphyrin units into a covalent organic framework (COF). Utilizing the rigid conjugated structure and strong coordination ability of the porphyrin ring, highly uniform dispersion of nickel and cobalt bimetallic active sites was achieved within the framework. High-temperature calcination and carbonization preserved the metal-nitrogen active centers while constructing a porous graphitic carbon framework with a high specific surface area, significantly enhancing the material's conductivity, structural stability, and the availability of active sites. This composite material exhibits excellent OER catalytic performance and long-term electrochemical stability in alkaline electrolytes, demonstrating promising practical application potential in the field of oxygen evolution reaction in water electrolysis.

[0027] As a specific embodiment of the present invention, the catalytic material based on the bimetallic porphyrin covalent organic framework structure prepared above is applied to the oxygen evolution reaction in water electrolysis. The specific application method is as follows: The prepared catalytic material based on a bimetallic porphyrin covalent organic framework was dispersed in a mixed solution of anhydrous methanol and Nafion solution. After thorough mixing, the suspension was drop-coated onto the surface of a rotating disk electrode and dried to obtain the working electrode. This electrode was then used in the water electrolysis oxygen evolution reaction, with KOH solution as the electrolyte.

[0028] Specifically, the concentration of the electrolyte is 0.8 mol / L to 1.2 mol / L.

[0029] In summary, this invention selects tetraaminophenylporphyrin nickel / cobalt as the reaction precursor, utilizing the porphyrin ring to react with Ni. 2+ Co 2+ The coordination effect of the bimetallic sites is atomically dispersed in the material framework and surface, significantly improving the exposure and utilization of active sites. Furthermore, by adjusting the ratio of nickel porphyrin to cobalt porphyrin, the optimal energy barrier requirement for the electrocatalytic oxygen evolution reaction (OER) is matched, further enhancing the catalytic kinetic efficiency. The catalytic material provided by this invention exhibits significantly superior OER catalytic activity compared to single-metal porphyrin covalent organic framework materials and other metal porphyrin covalent organic framework materials with different framework structures. It provides a high-performance, highly stable non-precious metal catalyst solution for clean energy technologies such as water electrolysis for hydrogen production, and has broad application prospects. Attached Figure Description

[0030] Figure 1 The PXRD patterns are of the covalent organic framework materials prepared in Examples 1-3 and Comparative Examples 1-2. Figure 2 Infrared spectra of the covalent organic framework materials, aminotetraphenylporphyrin and terephthalaldehyde prepared in Examples 1-3 and Comparative Examples 1-2; Figure 3 The solid-state carbon NMR spectrum of NiCo(1:1)@COF-366 prepared in Example 1; Figure 4 The X-ray photoelectron spectrum of NiCo(1:1)@COF-366 prepared in Example 1; where a) C 1s, b) N 1s, c) Ni 2p, d) Co 2p; Figure 5 Scanning electron microscope (a), transmission electron microscope (b), and EDS elemental mapping (cf) of NiCo(1:1)@COF-366 prepared in Example 1; Figure 6 Thermogravimetric analysis (TGA) diagrams of the covalent organic framework materials NiCo@COF-366 prepared in Examples 1-3 are shown below. Figure 7 Nitrogen adsorption-desorption isotherms (a) and pore size distribution (b) of NiCo@COF-366, the covalent organic framework materials prepared in Examples 1-3; Figure 8 Linear sweep voltammetric polarization curves and corresponding Tafel slope diagrams of the covalent organic framework material NiCo@COF-366 prepared in Examples 1-3; Figure 9 The AC impedance spectra of the covalent organic framework materials NiCo@COF-366 prepared in Examples 1-3 are shown. Figure 10Linear sweep voltammetric polarization curves and corresponding Tafel slope plots of NiCo(1:1)@COF-366 and Carbon-NiCo(1:1)@COF-366 prepared in Example 1; Figure 11 The AC impedance spectra of NiCo(1:1)@COF-366 and Carbon-NiCo(1:1)@COF-366 prepared in Example 1; Figure 12 The current density stability diagram of Carbon-NiCo(1:1)@COF-366 prepared in Example 1 is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] To better illustrate the present invention, further examples are provided below.

[0033] The preparation method of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin nickel used in the following examples is as follows: 400 mg (0.59 mmol) of 5,10,15,20-tetra(4-aminophenyl)porphyrin, 35 mL of N,N-dimethylformamide, and 15 mL of dichloromethane were added to a 100 mL round-bottom flask. 1 g (4.02 mmol) of nickel acetate tetrahydrate was added to 5 mL of methanol and dissolved by sonication. The solution was then transferred to the round-bottom flask and heated to 140 °C under a nitrogen atmosphere. The reaction was carried out at this temperature for 8 h. After the reaction was completed, the system was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was washed with methanol and dried under vacuum to obtain 367 mg of a purple solid product, with a yield of 75%.

[0034] The preparation method of 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt is as follows: 400 mg (0.59 mmol) of 5,10,15,20-tetra(4-aminophenyl)porphyrin, 35 mL of N,N-dimethylformamide, and 15 mL of dichloromethane were added to a 100 mL round-bottom flask. 1 g (4.01 mmol) of cobalt acetate tetrahydrate was added to 5 mL of methanol. After dissolving by sonication, the solution was transferred to the round-bottom flask and heated to 140 °C under nitrogen protection. The reaction was carried out at this temperature for 8 h. After the reaction was completed, the system was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was washed with methanol and dried under vacuum to obtain 350 mg of a purple solid product, with a yield of 71%.

[0035] Example 1 This embodiment provides a method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure, comprising the following steps: S1, 5,10,15,20-tetratetra(4-aminophenyl)porphyrin nickel (17.03 mg, 0.02 mmol), 5,10,15,20-tetratetra(4-aminophenyl)porphyrin cobalt (17.03 mg, 0.02 mmol), and terephthalaldehyde (10.73 mg, 0.08 mmol) were placed in a 20 mL Plyrex sealed tube, and 2 mL of anhydrous ethanol, 2 mL of anhydrous trimethylbenzene, and 0.4 mL of [unspecified substance] were added sequentially. A 6M aqueous solution of acetic acid was ultrasonically dispersed for 15 min. The solution underwent a three-stage freeze-vacuum-thaw cycle to remove gas. The solution was then flame-sealed and reacted in a 120℃ oven for 72 h. The precipitate was collected by filtration and washed three times sequentially with anhydrous tetrahydrofuran and anhydrous methanol. The precipitate was then dried in a vacuum oven at 80℃ for 12 h to obtain 32.4 mg of the covalent organic framework material NiCo(1:1)@COF-366 (reddish-purple solid powder), with a yield of 72.34%. S2, the covalent organic framework material NiCo(1:1)@COF-366 prepared above was placed in a tube furnace continuously filled with nitrogen, and then heated to 900°C at a heating rate of 5°C / min. It was then calcined and carbonized at high temperature in a nitrogen atmosphere for 9 hours and naturally cooled to room temperature to obtain the metal porphyrin-based covalent organic framework composite catalytic material, denoted as Carbon-NiCo(1:1)@COF-366.

[0036] Example 2 This embodiment provides a method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure, comprising the following steps: S1, 5,10,15,20-tetratetra(4-aminophenyl)porphyrin nickel (8.52 mg, 0.01 mmol), 5,10,15,20-tetratetra(4-aminophenyl)porphyrin cobalt (25.55 mg, 0.03 mmol), and terephthalaldehyde (10.73 mg, 0.08 mmol) were placed in a 20 mL Plyrex sealed tube, and 2 mL of anhydrous ethanol, 2 mL of anhydrous trimethylbenzene, and 0.4 mL of [unspecified substance] were added sequentially. A 6M aqueous solution of acetic acid was ultrasonically dispersed for 15 min. The solution underwent a three-stage freeze-vacuum-thaw cycle to remove gas. The solution was then flame-sealed and reacted in a 120℃ oven for 72 h. The precipitate was collected by filtration and washed three times sequentially with anhydrous tetrahydrofuran and anhydrous methanol. It was then dried in a vacuum oven at 80℃ for 12 h to obtain 31.43 mg of the covalent organic framework material NiCo(1:3)@COF-366 (reddish-purple solid powder), with a yield of 70.15%. S2, the covalent organic framework material NiCo(1:3)@COF-366 prepared above was placed in a tube furnace continuously filled with nitrogen, and then heated to 800°C at a heating rate of 5°C / min. It was then calcined and carbonized at high temperature in a nitrogen atmosphere for 12 hours and naturally cooled to room temperature to obtain the metal porphyrin-based covalent organic framework composite catalytic material, denoted as Carbon-NiCo(1:3)@COF-366.

[0037] Example 3 This embodiment provides a method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure, comprising the following steps: S1, 5,10,15,20-tetratetra(4-aminophenyl)porphyrin nickel (25.55 mg, 0.03 mmol), 5,10,15,20-tetratetra(4-aminophenyl)porphyrin cobalt (8.52 mg, 0.01 mmol), and terephthalaldehyde (10.73 mg, 0.08 mmol) were placed in a 20 mL Plyrex sealed tube, and 2 mL of anhydrous ethanol, 2 mL of anhydrous trimethylbenzene, and 0.4 mL of [unspecified substance] were added sequentially. A 6M aqueous solution of acetic acid was ultrasonically dispersed for 15 min. The solution underwent a three-stage freeze-vacuum-thaw cycle to remove gas. The solution was then flame-sealed and reacted in a 120℃ oven for 72 h. The precipitate was collected by filtration and washed three times sequentially with anhydrous tetrahydrofuran and anhydrous methanol. It was then dried in a vacuum oven at 80℃ for 12 h to obtain 31.79 mg of the covalent organic framework material NiCo(3:1)@COF-366 (reddish-purple solid powder), with a yield of 70.95%. S2, the covalent organic framework material NiCo(3:1)@COF-366 prepared above was placed in a tube furnace continuously filled with nitrogen, and then heated to 950°C at a heating rate of 5°C / min. It was then calcined and carbonized at high temperature in a nitrogen atmosphere for 3 hours and naturally cooled to room temperature to obtain the metal porphyrin-based covalent organic framework composite catalytic material, denoted as Carbon-NiCo(3:1)@COF-366.

[0038] Comparative Example 1 This comparative example provides a method for preparing a catalytic material based on a single-metal porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligand is 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel (34.06 mg, 0.04 mmol), and the single-metal covalent organic framework catalytic material Ni@COF-366 is obtained.

[0039] Comparative Example 2 This comparative example provides a method for preparing a catalytic material based on a single-metal porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligand is 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt (34.07 mg, 0.04 mmol), and the single-metal covalent organic framework catalytic material Co@COF-366 is obtained.

[0040] Comparative Example 3 This comparative example provides a method for preparing a catalytic material based on a single-metal porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligand is 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin nickel (22.14 mg, 0.02 mmol), and the single-metal covalent organic framework catalytic material TriazineNi@COF is obtained.

[0041] The preparation method of the above-mentioned 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin nickel is as follows: 620 mg (0.59 mmol) of 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin and 35 mL of N,N-dimethylformamide were added to a 100 mL round-bottom flask. 1 g (4.02 mmol) of nickel acetate tetrahydrate was added to 5 mL of methanol and dissolved by sonication. The solution was then transferred to the round-bottom flask. The reaction system was heated to 140 °C under nitrogen protection and reacted at this temperature for 12 h. After the reaction was completed, the system was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was washed with methanol and dried under vacuum to obtain 504 mg of a purple solid product, with a yield of 77%.

[0042] Comparative Example 4 This comparative example provides a method for preparing a catalytic material based on a single-metal porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligand is 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin cobalt (22.16 mg, 0.02 mmol), and the single-metal covalent organic framework catalytic material TriazineCo@COF is obtained.

[0043] The preparation method of the above-mentioned 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin cobalt is as follows: 620 mg (0.59 mmol) of 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin and 35 mL of N,N-dimethylformamide were added to a 100 mL round-bottom flask. 1 g (4.02 mmol) of cobalt acetate tetrahydrate was added to 5 mL of methanol and dissolved by sonication. The solution was then transferred to the round-bottom flask and heated to 140 °C under nitrogen protection. The reaction was carried out at this temperature for 12 h. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was washed with methanol and dried under vacuum to obtain 504 mg of a purple solid product, with a yield of 78%.

[0044] Comparative Example 5 This comparative example provides a method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligands are 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin nickel (11.06 mg, 0.01 mmol) and 5,10,15,20-tetrakis(4-(2,4-diaminotricyano)phenyl)-porphyrin cobalt (11.08 mg, 0.01 mmol), and the monometallic covalent organic framework catalytic material TriazineNiCo@COF is prepared.

[0045] The preparation methods of the above organic ligands are the same as those of Comparative Examples 3-4, and will not be repeated here.

[0046] Comparative Example 6 This comparative example provides a method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligand is 5,10,15,20-tetra(4-aminobiphenyl)porphyrin nickel (41.12 mg, 0.04 mmol), and a monometallic covalent organic framework catalytic material BiphenylNi@COF is prepared.

[0047] The preparation method of the above-mentioned 5,10,15,20-tetrakis(4-aminobiphenyl)porphyrin nickel is as follows: 578 mg (0.59 mmol) of 5,10,15,20-tetrakis(4-aminobiphenyl)porphyrin, 35 mL of N,N-dimethylformamide, and 15 mL of dichloromethane were added to a 100 mL round-bottom flask. 1 g (4.02 mmol) of nickel acetate tetrahydrate was added to 5 mL of methanol and dissolved by sonication. The solution was then transferred to the round-bottom flask and heated to 140 °C under nitrogen protection. The reaction was carried out at this temperature for 12 h. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was washed with methanol and dried under vacuum to obtain 495 mg of a purple solid product, with a yield of 81%.

[0048] Comparative Example 7 This comparative example provides a method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure. The only difference from step S1 in Example 1 is that the organic ligand is 5,10,15,20-tetra(4-aminobiphenyl)porphyrin cobalt (41.41 mg, 0.04 mmol), and a monometallic covalent organic framework catalytic material BiphenylCo@COF is prepared.

[0049] The preparation method of the above-mentioned 5,10,15,20-tetrakis(4-aminobiphenyl)porphyrin cobalt is as follows: 578 mg (0.59 mmol) of 5,10,15,20-tetrakis(4-aminobiphenyl)porphyrin and 35 mL of N,N-dimethylformamide were added to a 100 mL round-bottom flask. 1 g (4.02 mmol) of cobalt acetate tetrahydrate was added to 5 mL of methanol and dissolved by sonication. The solution was then transferred to the round-bottom flask and heated to 140 °C under nitrogen protection. The reaction was carried out at this temperature for 12 h. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was washed with methanol and dried under vacuum to obtain 482 mg of a purple solid product, with a yield of 79%.

[0050] Material characterization (1) X-ray diffraction analysis Crystallographic analysis was performed on the covalent organic framework materials prepared in Examples 1-3 and Comparative Examples 1-2, and the results are as follows: Figure 1 As shown.

[0051] As can be seen from the figure, the diffraction patterns of the five covalent organic framework materials show a high degree of consistency. Strong diffraction signals of the (110) and (001) crystal plane features were detected near 2θ of 3.5° and 26.5°, respectively. The strong diffraction peaks appearing at low angles are characteristic of the expected large unit cell parameters. The results indicate that the introduction of transition metals does not affect the crystal structure of this type of covalent organic framework material. Based on the constructed molecular configuration model of NiCo@COF-366, the theoretical diffraction pattern of its AA-type layered stacking configuration is in high agreement with the experimental data in terms of characteristic peak positions and relative intensity parameters.

[0052] (2) Infrared spectroscopy characterization like Figure 2 As shown, compared to aminotetraphenylporphyrin TAPP, the NiCo@COF-366 series of covalent organic framework catalysts exhibit better performance at 970 cm⁻¹. -1 The nitrogen-hydrogen bond of pyrrole disappears at 10¹⁰ cm⁻¹. -1 A new peak for nitrogen-metallic bonds appeared, indicating the successful recombination of cobalt and nickel. NiCo@COF-366 reached a peak at 3396 cm⁻¹. -1 (Stretching vibration peak of amino group in monomer TAPP) and 1700 cm⁻¹-1 The corresponding peak intensity at (the C=O stretching vibration peak in the terephthalaldehyde BDA monomer) essentially disappears. Meanwhile, at 1630 cm⁻¹... -1 Nearby, NiCo@COF-366 exhibited characteristic stretching vibration absorption peaks of imine C=N bonds, indicating successful condensation of the covalent organic framework material.

[0053] (3) Solid-state carbon NMR characterization Solid-state carbon NMR spectrum of NiCo(1:1)@COF-366 prepared in Example 1 ( Figure 3 In the study, the imine resonance signal at 159.5 ppm and other related resonance signals further confirmed that a highly ordered covalent assembly network was formed between the metalloporphyrin unit and the organic linker.

[0054] (4) V-ray photoelectron spectroscopy analysis X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition and electronic states of the NiCo(1:1)@COF-366 surface prepared in Example 1. Figure 4 ) was analyzed. C 1s spectrum ( Figure 4 a) Three main characteristic peaks appear, located at 284.8 eV, 285.6 eV, and 289.1 eV, respectively, which are attributed to aromatic sp² hybrid carbon (C=C), imine bond (C=N), and CN bond in porphyrin unit. The N 1s fractional spectrum was obtained simultaneously. Figure 4 b) Two characteristic signals are shown: 398.9 eV and 400.4 eV, corresponding to the nitrogen atom in the imine bond (C=N) and the metal-coordinated nitrogen atom in the porphyrin ring. The XPS spectrum of the NiCo (1:1)@COF-366 sample shows Co 2p and Ni 2p characteristic peaks, indicating that nickel and cobalt have been successfully embedded in the porphyrin structure. Ni 2p spectrum ( Figure 4 c) Two main peaks can be obtained at 855.2 eV and 874.4 eV, corresponding to the Ni 2p3 / 2 and Ni 2p1 / 2 orbital signals, respectively. (Co 2p spectrum) Figure 4 d) Two characteristic peaks appear at 797.9 eV and 784.8 eV, accompanied by typical satellite peaks, corresponding to Co. 2+ The signals of the Co 2p1 / 2 and Co 2p3 / 2 orbitals were observed. Furthermore, two additional sets of characteristic peaks for Co 2p1 / 2 and Co 2p3 / 2 were observed at 792.1 eV and 782.3 eV, presumably representing Co generated from the oxidation of cobalt. 3+ The above results confirm the successful synthesis of the NiCo@COF-366 catalyst.

[0055] (5) Morphological characteristics The surface morphology and pore structure of NiCo (1:1)@COF-366 prepared in Example 1 were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 5 ab). Analysis shows that NiCo(1:1)@COF-366 is composed of porous sheets with a size of 200-400 nm, exhibiting a granular morphology. Meanwhile, the corresponding elemental energy dispersive spectroscopy (EDS) surface distribution of NiCo(1:1)@COF-366 is shown in the figure. Figure 5 (cf) confirmed the uniform distribution of Ni, Co, C and N elements in the covalent organic framework material.

[0056] (6) Thermogravimetric analysis like Figure 6 As shown, thermogravimetric analysis (TGA) indicates that the covalent organic framework materials NiCo@COF-366 prepared in Examples 1-3 and Comparative Examples 1-2 have excellent thermal stability up to 300 °C. The mass loss that occurs before 300 °C is attributed to the evaporation of a small amount of solvent within the pores.

[0057] (7) BET test To investigate the specific surface area and pore characteristics of the covalent organic framework materials NiCo@COF-366 prepared in Examples 1-3 and Comparative Examples 1-2, nitrogen adsorption-desorption experiments were conducted at 77 K. The results are as follows: Figure 7 As shown in the figure. The results indicate that the BET specific surface area of ​​NiCo@COF-366 ranges from 954.95 to 1077.27 m². 2 Between / g ( Figure 7 a). Meanwhile, calculations using nonlocal density functional theory show that the average pore size of this series of covalent organic framework materials is 1.3 nm ( Figure 7 (b) and exhibit similar aperture distribution characteristics.

[0058] Performance testing The following is a performance study of the covalent organic framework material NiCo@COF-366 prepared in Examples 1-3 and Comparative Examples 1-7 in the electrocatalytic oxygen desorption reaction. The detailed test procedure is as follows: (1) First, polish the rotating disk electrode with alumina powder, then thoroughly clean the electrode with deionized water and anhydrous ethanol in sequence, and let it air dry naturally after cleaning. (2) Accurately weigh 5.0 mg of covalent organic framework material NiCo@COF-366, disperse it in a mixed solvent consisting of 975 μL anhydrous ethanol and 25 μL 5% perfluorosulfonic acid resin (Nafion) solution, and stir continuously for 12 h to prepare a catalyst suspension with a concentration of 5 mg / mL; use a micropipette to transfer 20 μL of the above catalyst suspension, drop it onto the surface of the pretreated rotating disk electrode, and dry it to obtain a catalyst loading of 0.5 mg / cm³. 2 Working electrode; (3) A three-electrode test system was assembled using a catalyst-supported rotating disk electrode (RDE) as the working electrode, a silver / silver chloride electrode (SCE) as the reference electrode, and a graphite rod as the counter electrode. (4) The working electrode after loading was activated by cyclic voltammetry (CV) with a scan rate of 100 mV / s. (5) After the catalyst is stable, use 1 mol / L oxygen-saturated KOH solution as electrolyte. Before each electrochemical test, bubble nitrogen gas into the electrolyte for at least 20 min to remove dissolved gas. The OER performance of the catalyst is tested by linear sweep voltammetry (LSV). The test parameters are set as follows: scan rate 5 mV / s, and potential window relative to silver / silver chloride reference electrode 0 V~0.8 V.

[0059] The results are as follows Figure 8 As shown in Figure a, Co@COF-366 of Comparative Example 2 and Ni@COF-366 of Comparative Example 1 reached 10 mA / cm² at overpotentials of 477 mV and 442 mV, respectively. 2 Current density. The NiCo (1:1)@COF-366 prepared in Example 1 achieved the same current output at an overpotential of 410 mV, which reduced the potential difference by 57 mV and 26 mV compared to the NiCo (1:3) system in Example 2 and the NiCo (3:1) system in Example 3, respectively. Meanwhile, the TriazineNi@COF, TriazineNi@COF, TriazineNiCo@COF, BiphenylNi@COF, and BiphenylNi@COF prepared in Comparative Examples 3-7 showed a current density of 10 mA / cm² under the same testing conditions. 2 The overpotentials at the current densities were 472mV, 452mV, 438mV, 468mV, and 457mV, respectively.

[0060] The above results indicate that the performance improvement of bimetallic porphyrin-based covalent organic framework materials is due to the electronic synergistic effect of the nickel-cobalt bimetallic center. The downward shift of the d-band center of the cobalt component enhances the adsorption strength of the hydroxyl oxide intermediate, while the nickel component promotes the oxygen evolution reaction kinetics by optimizing the interfacial charge transport efficiency.

[0061] like Figure 8 As shown in b, by fitting the polarization curves to the Tafel equation, the NiCo(1:1)@COF-366 system prepared in Example 1 exhibits a Tafel slope of 62 mV / dec, which is significantly lower than that of its proportional composite system and single-metal supported system. This reflects that the proportionally supported bimetallic active center can effectively regulate the energy barrier height of the oxygen evolution reaction process, especially promoting the kinetics of the formation and desorption of hydroxyl oxide intermediates.

[0062] The charge conduction mechanism at the interface between the metal covalent organic framework catalytic material and the electrolyte was investigated using electrochemical impedance spectroscopy (EIS). The results are as follows: Figure 9 As shown. The catalyst-supported working electrode was prepared using the same method, and an AC voltage of 5 mV was applied, covering a frequency range from 100 kHz to 0.1 Hz, with a 1 M KOH solution as the substrate. Experimental results show that NiCo(1:1)@COF-366 possesses the lowest interfacial charge transfer resistance (97 Ω). This impedance variation is consistent with the results of linear sweep voltammetry and Tafel curve analysis, confirming that the bimetallic synergistic effect can significantly improve the conductivity of the catalytic material while improving the charge carrier transport path.

[0063] like Figure 10 As shown, in Example 1, the high-temperature carbonized Carbon-NiCo(1:1)@COF-366 achieved a current density of 10 mA / cm² in a 1 M KOH electrolyte. 2 The required overpotential is only 325 mV, representing a 20.7% performance improvement compared to NiCo(1:1)@COF-366. This performance improvement is significantly higher than that achieved by conventional metal post-doping and morphology control strategies. After calcination, the Tafel slope of the Carbon-NiCo(1:1)@COF-366 sample was 47 mV / dec, while that of NiCo(1:1)@COF-366 was 62 mV / dec, confirming the improvement in kinetic parameters. The Carbon-NiCo@COF-366 prepared in Examples 2 and 3 achieved a current density of 10 mA / cm² in a 1 M KOH electrolyte. 2 The required overpotentials are 386mV and 405mV, respectively.

[0064] Simultaneously, analysis was conducted through EIS testing ( Figure 11 The charge transfer resistance of Carbon-NiCo(1:1)@COF-366 is 22Ω. High-temperature induced carbonization of organic ligands into graphitized sp... 2The hybrid carbon network significantly improves carrier mobility, while the partially retained ordered channels of the COF framework provide efficient transport channels for electrolyte permeation and bubble release.

[0065] like Figure 12 As shown, the electrochemical stability of the Carbon-NiCo(1:1)@COF-366 covalent organic framework composite catalyst was tested using a chronoamperometry method. The catalyst-supported working electrode was prepared using the same method, and its current stability was tested at an overpotential of 325 mV in a 1M KOH solution. Carbon-NiCo(1:1)@COF-366 maintained a stable current density output for 62,000 s. After the test time exceeded 62,000 s, the current density began to decrease. The possible reason for this degradation is that O2 bubbles generated during the oxygen evolution reaction formed a gas film layer at the catalyst / electrolyte interface, leading to a reduction in the effective area of ​​the three-phase interface.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a catalytic material based on a bimetallic porphyrin covalent organic framework structure, characterized in that, Includes the following steps: S1, a bimetallic porphyrin-based organic ligand and terephthalaldehyde are subjected to a solvothermal reaction in an organic solvent containing an acidic catalyst to obtain a covalent organic framework material; wherein, the bimetallic porphyrin-based organic ligand includes 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt; S2, Under an inert atmosphere, the covalent organic framework material is calcined and carbonized to obtain a catalytic material based on a bimetallic porphyrin covalent organic framework structure.

2. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1, characterized in that, Specifically, the steps include the following: S1, a bimetallic porphyrin-based organic ligand and terephthalaldehyde are dispersed in an organic solvent containing an acidic catalyst, the gas in the system is removed, and a solvothermal reaction is carried out under closed conditions. After washing and drying, a covalent organic framework material is obtained. S2, the covalent organic framework material is placed in a tube furnace and calcined and carbonized under an inert atmosphere, then cooled to obtain a catalytic material based on a bimetallic porphyrin covalent organic framework structure.

3. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1 or 2, characterized in that, In S1, the molar ratio of 5,10,15,20-tetra(4-aminophenyl)porphyrin nickel and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt is 1:3 to 3:

1.

4. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1 or 2, characterized in that, In S1, the molar ratio of the bimetallic porphyrin-based organic ligand to terephthalaldehyde is 1:2 to 1:

3.

5. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1 or 2, characterized in that, In S1, the organic solvent is a mixture of mesitylene and anhydrous ethanol in a volume ratio of 1:1 to 1:

3.

6. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1 or 2, characterized in that, In S1, the acidic catalyst is an acetic acid solution with a concentration of 3 mol / L to 8 mol / L, wherein the molar ratio of CH3COOH to the bimetallic porphyrin-based organic ligand in the acetic acid solution is 20:1 to 70:

1.

7. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1 or 2, characterized in that, In S1, the temperature of the solvothermal reaction is 100℃~150℃, and the reaction time is 24h~72h.

8. The method for preparing the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 1 or 2, characterized in that, In S2, the calcination and carbonization temperature is 800℃~950℃, and the time is 3h~12h.

9. A catalytic material based on a bimetallic porphyrin covalent organic framework structure, characterized in that, The catalytic material based on the bimetallic porphyrin covalent organic framework structure is prepared by any one of claims 1 to 8.

10. The application of the catalytic material based on the bimetallic porphyrin covalent organic framework structure as described in claim 9 in the electrocatalytic oxygen evolution reaction.

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