Metal phthalocyanine covalent organic framework material, preparation method thereof and application thereof in electrocatalytic oxygen reduction

Abstract

This invention provides a metal phthalocyanine covalent organic framework material, its preparation method, and its application in electrocatalytic oxygen reduction. Compared with existing technologies, this invention mixes metal phthalocyanine with small organic molecules, cycles through freezing, vacuum, and thawing, and then reacts under sealed conditions to obtain the metal phthalocyanine covalent organic framework material. By selecting different building blocks, this invention achieves molecular-level control of the microenvironment near the catalytic site, thereby regulating the electronic structure and ionic environment of the catalytic site to suit the target catalytic application. Simultaneously, the one-dimensional ordered pore structure of the covalent organic framework improves carrier transport. Furthermore, by combining it with functionalized carbon nanotube materials, the conductivity and accessibility of the catalytic site are further enhanced.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to metal phthalocyanine covalent organic framework materials, their preparation methods, and their application in electrocatalytic oxygen reduction. Background Technology

[0002] Electrocatalytic oxygen reduction (ORR) is a crucial step in novel energy storage and conversion systems such as fuel cells and metal-air batteries. Developing efficient and durable ORR electrocatalysts is considered a key technology for the development of various clean energy devices. Pt-based materials are the best available ORR catalysts due to their superior catalytic activity and stability. However, their high cost and limited resource reserves restrict their large-scale application, driving significant development of non-precious metal ORR catalysts.

[0003] Currently, materials containing metal-nitrogen-carbon (M-N4-C) active sites are considered the most promising ORR catalysts to replace Pt. Transition metal phthalocyanines, as typical M-N4-C materials, have attracted considerable interest from researchers, with iron phthalocyanine (FePc) exhibiting the highest ORR catalytic activity. However, current research on these materials still faces some key challenges, such as the tendency of FePc to aggregate, poor conductivity, and durability.

[0004] Chinese patent CN 111193035 A, published on May 10, 2024, discloses a method for preparing an oxygen reduction electrocatalyst using a composite material of defective graphene and iron phthalocyanine with strong π-π conjugation. The disclosed technical solution is as follows: using defective graphene and iron phthalocyanine as raw materials, an electrocatalyst with excellent oxygen reduction activity was successfully prepared. However, it does not disclose how to solve the problem of FePc easy aggregation. Summary of the Invention

[0005] The purpose of this invention is to provide a metal phthalocyanine covalent organic framework material and its preparation method. The method involves mixing metal phthalocyanine with small organic molecules, cycling through freeze-vacuum and thaw cycles, and then reacting under sealed conditions to obtain the metal phthalocyanine covalent organic framework material. This invention achieves molecular-level control of the microenvironment near the catalytic site by selecting different building blocks (small organic molecules), thereby regulating the electronic structure and ionic environment of the catalytic site to suit the target catalytic application and effectively preventing the aggregation of catalytic sites. Simultaneously, the one-dimensional ordered pore structure of the covalent organic framework improves carrier transport. Furthermore, by combining it with functionalized carbon nanotube materials, the conductivity and accessibility of the catalytic site are further enhanced.

[0006] Another objective of this invention is to provide the application of metal phthalocyanine covalent organic framework materials in electrocatalytic oxygen reduction. This invention optimizes the electrocatalytic oxygen reduction performance by using covalent organic frameworks with tunable microenvironment near the catalytic site and their composite strategy with carbon nanotubes.

[0007] The specific technical solution of this invention is as follows:

[0008] The preparation method of metal phthalocyanine covalent organic framework materials is as follows:

[0009] Metal phthalocyanine, small organic molecules, solvent and catalyst are mixed and then reacted under sealed conditions after a freeze-vacuum-thaw cycle to obtain metal phthalocyanine covalent organic framework materials.

[0010] Preferably, the preparation method is as follows:

[0011] Metal phthalocyanine and small organic molecules are added to a solvent, and the mixture is sonicated to obtain a suspension. A catalyst is then added, and the mixture is subjected to a freeze-vacuum-thaw cycle before being reacted under sealed conditions to obtain a metal phthalocyanine covalent organic framework material.

[0012] The molar ratio of the metal phthalocyanine to the small organic molecule is 1-3:1-3; preferably 1:1, 1:2, 1:3, 2:1 or 3:1; more preferably 1:2;

[0013] The metal phthalocyanine is MPc-16X, wherein M is any one of Fe, Co, Ni or Cu, and X is any one of F or Cl;

[0014] The organic small molecule is any one of 9,10-dimethyl-2,3,6,7-tetrahydroxyanthracene (THDMA), 1,2,4,5-phenyltetraol (THB), 1,2,4,5-phenyltetramine tetrahydrochloride (TTH), or 2,5-diamino-1,4-phenyldithiophene dihydrochloride (DBD).

[0015] The concentration of the metal phthalocyanine in the solvent is 0.01 mol / L;

[0016] The catalyst is any one of ammonia, trimethylamine, or triethylamine; preferably triethylamine.

[0017] The solvent is mesitylene or dioxane;

[0018] More preferably, when the solvent is mesitylene, the catalyst is triethylamine; when the solvent is dioxane, the catalyst is ammonia, trimethylamine or triethylamine.

[0019] The most preferred catalyst is triethylamine when the solvent is dioxane.

[0020] The ratio of metal phthalocyanine to catalyst is 0.001 mmol / μL;

[0021] The freezing-vacuum-thawing cycle involves placing the mixed solution in a container, freezing it in liquid nitrogen, evacuating it to a vacuum, and then thawing it. This process is repeated three times to maintain a vacuum in the system.

[0022] The reaction is carried out under sealed conditions at a temperature of 60℃-160℃ for 3-7 days; preferably, the reaction is carried out at 120℃ for 3 days.

[0023] Furthermore, after the reaction was completed, the product was filtered, washed, and then extracted to obtain a metal phthalocyanine covalent organic framework material.

[0024] The preparation method also incorporates carbon nanotube materials;

[0025] The ratio of the metal phthalocyanine to the added carbon nanotube material is 0.001 mmol / mg;

[0026] The carbon nanotube material is any one of single-walled carbon nanotubes, multi-walled carbon nanotubes, short multi-walled carbon nanotubes, carboxyl-functionalized carbon multi-walled nanotubes, amino-functionalized multi-walled carbon nanotubes, or hydroxyl-functionalized multi-walled carbon nanotubes; preferably, amino-functionalized multi-walled carbon nanotubes.

[0027] The metal phthalocyanine covalent organic framework material prepared by adding carbon nanotubes is a composite material of metal phthalocyanine covalent organic framework and carbon nanotubes.

[0028] Preferably, the preparation method further includes the addition of carbon nanotube materials as follows:

[0029] Metal phthalocyanine, small organic molecules, and carbon nanotube materials are added to a solvent, ultrasonically treated to obtain a suspension, a catalyst is added, and after a freeze-vacuum-thaw cycle, the reaction is carried out under sealed conditions to obtain a metal phthalocyanine covalent organic framework material.

[0030] Furthermore, the metal phthalocyanine covalent organic framework-carbon nanotube composite material can also be:

[0031] 1) Metal phthalocyanine, small organic molecules, solvent and catalyst are mixed and then reacted under sealed conditions after a freeze-vacuum-thaw cycle to obtain metal phthalocyanine covalent organic framework material;

[0032] 2) Physically blend metal phthalocyanine covalent organic framework materials and carbon nanotube materials to obtain metal phthalocyanine covalent organic framework and carbon nanotube composite materials;

[0033] The metal phthalocyanine covalent organic framework material provided by this invention is prepared using the above method.

[0034] This invention also provides the application of metal phthalocyanine covalent organic framework materials in electrocatalytic oxygen reduction.

[0035] The inventors discovered that covalent organic frameworks (COFs), as a novel type of crystalline porous material, have attracted widespread attention due to their periodic framework, tunable catalytic site microenvironment, and good stability, making them an ideal platform for developing ORR catalysts. Introducing FePc as a building block into the COF framework not only allows for the targeted design of the catalytic site microenvironment but also effectively prevents the aggregation of catalytic sites. To regulate the electronic structure around the active center Fe, different heteroatoms are introduced into the COF framework to increase electron donor or acceptor sites. Simultaneously, the hybridization of certain heteroatoms (such as nitrogen and sulfur) with carbon atoms can enhance the π-conjugated system in COFs, promoting electron delocalization. To achieve accessibility of catalytic sites, COFs with different pore structures and interlayer spacings were designed. Furthermore, to improve the overall conductivity of the material, a composite with functional carbon nanotubes was designed. Through strong π-π interactions with layered 2D COFs, carrier migration efficiency is improved, thereby enhancing catalytic activity.

[0036] Compared with existing technologies, this invention improves the catalytic performance of materials by constructing a covalent organic framework structure and selecting different building blocks (small organic molecules) to regulate the microenvironment near the catalytic site at the molecular level. Simultaneously, the framework structure allows the active sites (MPc) to be better dispersed on the surface of the framework structure during the catalytic reaction. Compared with metal phthalocyanine polymers alone, the utilization rate of active sites is improved, significantly enhancing the overall performance of the material. The one-dimensional porous structure obtained after constructing the covalent organic framework facilitates proton and ion transport, improving the conductivity and catalytic activity of the material to a certain extent. The halogen-containing and hydroxyl-containing building blocks, linked by aromatic ether bonds, endow the material with extremely high stability, enabling the material to maintain its original framework structure and catalytic performance during subsequent development and utilization. Furthermore, by compositing the covalent organic framework material with functionalized carbon nanotubes, the conductivity of the material is improved. At the same time, the porous structure of the carbon nanotubes allows for better dispersion, greatly increasing the specific surface area and improving the contact opportunity between gas molecules and the catalytic site, thereby enhancing the catalytic performance of the material. This invention applies metal phthalocyanine covalent organic framework materials to the electrocatalytic ORR reaction, and the synthesized composite material exhibits superior electrocatalytic ORR performance (EORR). 1 / 2 =0.92V vs. RHE), which is superior to currently reported ORR catalysts. Furthermore, through comparative experiments and performance tests, the selected synthesis method and testing conditions are currently the most convenient and effective approach. The product is easy to separate and purify, and the prepared material is more environmentally friendly and efficient, showing promise for industrial application. It also provides new research ideas for the development of subsequent catalysts. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of FePc-THDMA-COF;

[0038] Figure 2 This is a schematic diagram of the structure of FePc-THB-COF;

[0039] Figure 3 This is a schematic diagram of the structure of FePc-TTH-COF;

[0040] Figure 4 This is a schematic diagram of the structure of FePc-DBD-COF;

[0041] Figure 5 Field emission scanning electron microscope image of FePc-THDMA-COF / CNTs;

[0042] Figure 6 Field emission scanning electron microscope image of FePc-THB-COF / CNTs;

[0043] Figure 7 Infrared test results for THDMA, FePc-16F, FePc-THDMA-COF and FePc-THDMA-COF / CNTs;

[0044] Figure 8 Infrared test results for THB, FePc-16F, FePc-THB-COF, and FePc-THB-COF / CNTs;

[0045] Figure 9 The LSV curves of FePc-THDMA-COF under different rotational speeds are shown.

[0046] Figure 10 LSV curves of FePc-THDMA-COF / CNTs under different rotational speeds;

[0047] Figure 11 LSV curves of FePc-THB-COF under different rotational speeds;

[0048] Figure 12 LSV curves of FePc-THB-COF / CNTs under different rotational speeds;

[0049] Figure 13 LSV curves of FePc-TTH-COF under different rotational speeds;

[0050] Figure 14 The LSV curves of FePc-DBD-COF under different rotational speeds are shown. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0053] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0054] Example 1

[0055] The preparation method of the metal phthalocyanine covalent organic framework material FePc-THDMA-COF is as follows:

[0056] FePc-16F (0.02 mmol, 17.12 mg) and THDMA (0.04 mmol, 10.81 mg) were added to a 10 mL Pyrex tube, followed by 2 mL of dioxane solvent. The mixture was sonicated for 10 minutes to form a homogeneous suspension. Then, 20 μL of triethylamine was added to the mixture. The Pyrex tube containing the suspension was frozen in liquid nitrogen, evacuated to a vacuum, and then thawed. This process was repeated three times to maintain a vacuum. The tube was then sealed and heated in an oven at 120 °C for three days. The black precipitate was collected by centrifugation and washed for one week each with acetone, dichloromethane, and tetrahydrofuran (THF) in a Soxhlet extractor. The resulting material was designated FePc-THDMA-COF; its structure is as described. Figure 1 As shown.

[0057] like Figure 7 As shown, the material structure was analyzed using a Fourier transform infrared spectrometer (Bruker Scientific Instruments, INVENIO), at a depth of 1352 cm⁻¹. -1 963cm -1 The appearance of two sets of characteristic peaks can be observed, which is attributed to the symmetric and asymmetric tensile vibrations of the COC bond, thus confirming the successful construction of the material skeleton;

[0058] The tests were conducted using a CHI760E electrochemical workstation and a rotating disk electrode apparatus. A three-electrode system was used in a five-cell electrolytic cell, with an Ag / AgCl electrode and a Pt sheet as the reference and counter electrodes. The material obtained in Example 1 (5 mg), Ketjen black carbon powder (5 mg), and a perfluorinated Nafion resin solution (25 μL, 5 wt%) were added to a vial containing isopropanol (975 μL). After ultrasonic treatment for 60 minutes, a catalyst ink slurry was obtained. 10 mL of the obtained ink slurry was uniformly coated onto a disk electrode rde (disk inner diameter = 5.0 mm) to prepare the working electrode.

[0059] Using 0.1M KOH as the electrolyte, O2 was first bubbled into it for 30 minutes to saturate the electrolyte. The disc rotation speed was adjusted to test under different speed conditions of 400, 625, 900, 1225, and 1600 rpm.

[0060] Figure 9 The linear scanning voltammetry curve shown was obtained at a scan rate of 20 mV / s. The curve reveals that the half-wave potential and limiting current density of FePc-THDMA-COF are 0.89 V and 5.78 mA / cm², respectively. -2 .

[0061] Following the same preparation method as in Example 1, but changing the type of catalyst and solvent, the crystallinity of the product was investigated, and the results are shown in Table 1.

[0062] Table 1. Effects of different reaction conditions on the crystallinity of the material.

[0063]

[0064] The higher the crystallinity of the product, the more favorable it is for carrier transport. Therefore, the most preferred solvent in this invention is dioxane, and the catalyst is triethylamine, resulting in a product with high crystallinity that is beneficial for carrier transport.

[0065] Example 2

[0066] The preparation method of the metal phthalocyanine covalent organic framework material FePc-THB-COF is as follows:

[0067] FePc-16F (0.02 mmol, 17.12 mg) and THB (0.04 mmol, 5.68 mg) were added to a 10 mL Pyrex tube, followed by 2 mL of dioxane solvent. The mixture was sonicated for 10 minutes to form a homogeneous suspension. Then, 20 μL of triethylamine was added to the mixture. The Pyrex tube containing the suspension was frozen in liquid nitrogen, thawed under vacuum, and this process was repeated three times to maintain a vacuum. The tube was then sealed and heated in an oven at 120 °C for three days. The black precipitate was collected by centrifugation and washed for one week each with acetone, dichloromethane, and THF in a Soxhlet extractor. The resulting material was designated FePc-THB-COF, and its structure is described below. Figure 2 As shown.

[0068] Figure 8 As shown, the material structure was analyzed using a Fourier transform infrared spectrometer (Bruker Scientific Instruments, INVENIO), at a depth of 1352 cm⁻¹. -1 963cm -1 The appearance of two sets of characteristic peaks can be observed, which is attributed to the symmetric and asymmetric tensile vibrations of the COC bond, thus confirming the successful construction of the material skeleton.

[0069] The tests were conducted using a CHI760E electrochemical workstation and a rotating disk electrode apparatus. A three-electrode system was used in a five-cell electrolytic cell, with an Ag / AgCl electrode and a Pt sheet as the reference and counter electrodes. The material obtained in Example 2 (5 mg), Ketjen black carbon powder (5 mg), and a perfluorinated Nafion resin solution (25 μL, 5 wt%) were added to a vial containing isopropanol (975 μL). After ultrasonic treatment for 60 minutes, a catalyst ink slurry was obtained. 10 mL of the obtained ink slurry was uniformly coated onto a disk electrode rde (disk inner diameter = 5.0 mm) to prepare the working electrode.

[0070] Using 0.1M KOH as the electrolyte, O2 was first bubbled into it for 30 minutes to saturate the electrolyte. The disc rotation speed was adjusted to test under different speed conditions of 400, 625, 900, 1225, and 1600 rpm.

[0071] Figure 11 The linear scanning voltammetry curve shown was obtained at a scan rate of 20 mV / s. The curve reveals that the half-wave potential and limiting current density of FePc-THB-COF are 0.88 V and 5.09 mA / cm², respectively. -2 .

[0072] Example 3

[0073] The preparation method of the metal phthalocyanine covalent organic framework material FePc-TTH-COF is as follows:

[0074] FePc-16F (0.02 mmol, 17.12 mg) and TTH (0.04 mmol, 11.36 mg) were added to a 10 mL Pyrex tube, followed by 2 mL of dioxane solvent. The mixture was sonicated for 10 minutes to form a homogeneous suspension. Then, 20 μL of triethylamine was added to the mixture. The Pyrex tube containing the suspension was then frozen in liquid nitrogen, evacuated to a vacuum, and thawed. This process was repeated three times to maintain a vacuum. The tube was then sealed and heated in an oven at 120 °C for three days. The black precipitate was collected by centrifugation and washed for one week each with acetone, dichloromethane, and THF in a Soxhlet extractor. The resulting material was designated FePc-TTH-COF; its structure is as described. Figure 3 As shown.

[0075] The tests were conducted using a CHI760E electrochemical workstation and a rotating disk electrode apparatus. A three-electrode system was used in a five-cell electrolytic cell, with an Ag / AgCl electrode and a Pt sheet as the reference and counter electrodes. The material obtained in Example 3 (5 mg), Ketjen black carbon powder (5 mg), and a perfluorinated Nafion resin solution (25 μL, 5 wt%) were added to a vial containing isopropanol (975 μL). After ultrasonic treatment for 60 minutes, a catalyst ink slurry was obtained. 10 mL of the obtained ink slurry was uniformly coated onto a disk electrode rde (disk inner diameter = 5.0 mm) to prepare the working electrode.

[0076] Using 0.1M KOH as the electrolyte, O2 was first bubbled into it for 30 minutes to saturate the electrolyte. The disc rotation speed was adjusted to test under different speed conditions of 400, 625, 900, 1225, and 1600 rpm.

[0077] Figure 13 The linear scanning voltammetry curve shown was obtained at a scan rate of 20 mV / s. The curve reveals that the half-wave potential and limiting current density of FePc-TTH-COF are 0.78 V and 5.34 mA / cm², respectively. -2 .

[0078] Example 4

[0079] The preparation method of the metal phthalocyanine covalent organic framework material FePc-DBD-COF is as follows:

[0080] FePc-16F (0.02 mmol, 17.12 mg) and DBD (0.04 mmol, 9.80 mg) were added to a 10 mL Pyrex tube, along with 2 mL of dioxane solvent. The mixture was sonicated for 10 minutes to form a homogeneous suspension. Then, 20 μL of triethylamine was added to the mixture. The Pyrex tube containing the suspension was then frozen in liquid nitrogen, evacuated to a vacuum, and thawed. This process was repeated three times to maintain a vacuum. The tube was then sealed and heated in an oven at 120 °C for three days. The black precipitate was collected by centrifugation and washed for one week each with acetone, dichloromethane, and THF in a Soxhlet extractor. The resulting material was designated FePc-DBD-COF; its structure is as described. Figure 4 As shown.

[0081] The tests were conducted using a CHI760E electrochemical workstation and a rotating disk electrode apparatus. A three-electrode system was used in a five-cell electrolytic cell, with an Ag / AgCl electrode and a Pt sheet as the reference and counter electrodes. The material obtained in Example 4 (5 mg), Ketjen black carbon powder (5 mg), and a perfluorinated Nafion resin solution (25 μL, 5 wt%) were added to a vial containing isopropanol (975 μL). After ultrasonic treatment for 60 minutes, a catalyst ink slurry was obtained. 10 mL of the obtained ink slurry was uniformly coated onto a disk electrode rde (disk inner diameter = 5.0 mm) to prepare the working electrode.

[0082] Using 0.1M KOH as the electrolyte, O2 was first bubbled into it for 30 minutes to saturate the electrolyte. The disc rotation speed was adjusted to test under different speed conditions of 400, 625, 900, 1225, and 1600 rpm.

[0083] Figure 14 The linear scanning voltammetry curve shown was obtained at a scan rate of 20 mV / s. The curve reveals that the half-wave potential and limiting current density of FePc-DBD-COF are 0.82 V and 4.78 mA / cm², respectively. -2 .

[0084] Example 5

[0085] The preparation method of FePc-THDMA-COF / CNTs, a metal phthalocyanine covalent organic framework-carbon nanotube composite material, is as follows:

[0086] FePc-16F (0.02 mmol, 17.12 mg), THDMA (0.04 mmol, 10.81 mg), and 20 mg of amino-functionalized carbon nanotubes (MWCNTs) were added to a 10 mL Pyrex tube. 2 mL of dioxane solvent was added, and the mixture was sonicated for 10 minutes to form a homogeneous suspension. Then, 20 μL of triethylamine was added to the mixture. The Pyrex tube containing the suspension was frozen in liquid nitrogen, thawed under vacuum, and this process was repeated three times to maintain a vacuum. The tube was then sealed and heated in an oven at 120 °C for three days. The black precipitate was collected by centrifugation and washed for one week each with acetone, dichloromethane, and THF in a Soxhlet extractor. The resulting material was designated FePc-THDMA-COF / CNTs.

[0087] Figure 5 As shown in the field emission scanning electron microscope image, FePc-THDMA-COF and amino-functionalized multi-walled carbon nanotubes are fully and uniformly mixed, and the whole structure presents a loose and porous morphology, which is conducive to the exposure of active sites and gas diffusion and transport.

[0088] Figure 7 As shown, the material structure was analyzed using a Fourier transform infrared spectrometer (Bruker Scientific Instruments, INVENIO), at a depth of 1352 cm⁻¹. -1 963cm -1 The appearance of two sets of characteristic peaks can be observed, which is attributed to the symmetric and asymmetric stretching vibrations of COC bonds, thus confirming the successful construction of the material framework and that the introduction of amino-functionalized carbon nanotubes did not destroy the framework structure of the material.

[0089] The tests were conducted using a CHI760E electrochemical workstation and a rotating disk electrode apparatus. A three-electrode system was used in a five-cell electrolytic cell, with an Ag / AgCl electrode and a Pt sheet as the reference and counter electrodes. The material obtained in Example 5 (5 mg), Ketjen black carbon powder (5 mg), and a perfluorinated Nafion resin solution (25 μL, 5 wt%) were added to a vial containing isopropanol (975 μL). After ultrasonic treatment for 60 minutes, a catalyst ink slurry was obtained. 10 mL of the obtained ink slurry was uniformly coated onto a disk electrode rde (disk inner diameter = 5.0 mm) to prepare the working electrode.

[0090] Using 0.1M KOH as the electrolyte, O2 was first bubbled into it for 30 minutes to saturate the electrolyte. The disc rotation speed was adjusted to test under different speed conditions of 400, 625, 900, 1225, and 1600 rpm.

[0091] Figure 10The linear scanning voltammetry curves shown were obtained at a scan rate of 20 mV / s. The curves indicate that the half-wave potential and limiting current density of FePc-THDMA-COF / CNTs are 0.92 V and 6.46 mA / cm², respectively. -2 .

[0092] Example 6

[0093] The preparation method of FePc-THB-COF / CNTs, a metal phthalocyanine covalent organic framework-carbon nanotube composite material, is as follows:

[0094] FePc-16F (0.02 mmol, 17.12 mg), THB (0.04 mmol, 5.68 mg), and 20 mg of amino-functionalized carbon nanotubes (MWCNTs) were added to a 10 mL Pyrex tube. 2 mL of dioxane solvent was added, and the mixture was sonicated for 10 minutes to form a homogeneous suspension. Then, 20 μL of triethylamine was added to the mixture. The Pyrex tube containing the suspension was frozen in liquid nitrogen, thawed under vacuum, and this process was repeated three times to maintain a vacuum. The tube was then sealed and heated in an oven at 120 °C for three days. The black precipitate was collected by centrifugation and washed for one week each with acetone, dichloromethane, and THF in a Soxhlet extractor. The resulting material was designated FePc-THB-COF / CNTs.

[0095] Figure 6 As shown in the field emission scanning electron microscope image, FePc-THB-COF is thoroughly and uniformly mixed with amino-functionalized multi-walled carbon nanotubes, and the entire structure exhibits a loose and porous morphology, which is conducive to the exposure of active sites and gas diffusion and transport.

[0096] Figure 8 As shown, the material structure was analyzed using a Fourier transform infrared spectrometer (Bruker Scientific Instruments, INVENIO), at a depth of 1352 cm⁻¹. -1 963cm -1 The appearance of two sets of characteristic peaks can be observed, which is attributed to the symmetric and asymmetric stretching vibrations of the COC bond, thus confirming the successful construction of the material framework and that the introduction of amino-functionalized carbon nanotubes did not destroy the framework structure of the material.

[0097] The tests were conducted using a CHI760E electrochemical workstation and a rotating disk electrode apparatus. A three-electrode system was used in a five-cell electrolytic cell, with an Ag / AgCl electrode and a Pt sheet as the reference and counter electrodes. The material obtained in Example 6 (5 mg), Ketjen black carbon powder (5 mg), and a perfluorinated Nafion resin solution (25 μL, 5 wt%) were added to a vial containing isopropanol (975 μL). After ultrasonic treatment for 60 minutes, a catalyst ink slurry was obtained. 10 mL of the obtained ink slurry was uniformly coated onto a disk electrode rde (disk inner diameter = 5.0 mm) to prepare the working electrode.

[0098] Using 0.1M KOH as the electrolyte, O2 was first bubbled into it for 30 minutes to saturate the electrolyte. The disc rotation speed was adjusted to test under different speed conditions of 400, 625, 900, 1225, and 1600 rpm.

[0099] Figure 12 The linear scanning voltammetry curve shown was obtained at a scan rate of 20 mV / s. The curve reveals that the half-wave potential and limiting current density of FePc-THB-COF / CNTs are 0.91 V and 6.02 mA / cm², respectively. -2 .

[0100] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a metal phthalocyanine covalent organic framework material, characterized in that, The preparation method is specifically as follows: Metal phthalocyanine, small organic molecules, solvent and catalyst were mixed and reacted under sealed conditions after a freeze-vacuum-thaw cycle to obtain metal phthalocyanine covalent organic framework materials. The metal phthalocyanine is MPc-16X, wherein M is any one of Fe, Co, Ni or Cu; and X is any one of F or Cl. The organic small molecule is any one of 9,10-dimethyl-2,3,6,7-tetrahydroxyanthracene, 1,2,4,5-benzenetetrol, 1,2,4,5-benzenetetramine tetrahydrochloride, or 2,5-diamino-1,4-benzenedithiophene dihydrochloride. The freezing-vacuum-thawing cycle involves placing the mixed solution in a container, freezing it in liquid nitrogen, evacuating it to a vacuum state, and then thawing it. This process is repeated three times to maintain a vacuum in the system. The molar ratio of the metal phthalocyanine to the small organic molecule is 1-3:1-3.

2. The preparation method according to claim 1, characterized in that, The solvent is mesitylene or dioxane; the catalyst is any one of ammonia, trimethylamine, or triethylamine.

3. The preparation method according to claim 1, characterized in that, The reaction is carried out under sealed conditions at a temperature of 60℃-160℃ for 3-7 days.

4. A method for preparing a metal phthalocyanine covalent organic framework material, characterized in that, The preparation method is specifically as follows: Metal phthalocyanine, small organic molecules and carbon nanotube materials are added to a solvent, ultrasonically treated to obtain a suspension, then a catalyst is added, and after freezing-vacuum-thawing cycles, the reaction is carried out under sealed conditions to obtain metal phthalocyanine covalent organic framework materials. The metal phthalocyanine is MPc-16X, wherein M is any one of Fe, Co, Ni or Cu; and X is any one of F or Cl. The organic small molecule is any one of 9,10-dimethyl-2,3,6,7-tetrahydroxyanthracene, 1,2,4,5-benzenetetrol, 1,2,4,5-benzenetetramine tetrahydrochloride, or 2,5-diamino-1,4-benzenedithiophene dihydrochloride. The freezing-vacuum-thawing cycle involves placing the mixed solution in a container, freezing it in liquid nitrogen, evacuating it to a vacuum state, and then thawing it. This process is repeated three times to maintain a vacuum in the system. The molar ratio of the metal phthalocyanine to the small organic molecule is 1-3:1-3; The ratio of metal phthalocyanine to carbon nanotube material is 0.001 mmol / mg.

5. A metal phthalocyanine covalent organic framework material prepared by the preparation method according to any one of claims 1-4.

6. The application of the metal phthalocyanine covalent organic framework material of claim 5 in electrocatalytic oxygen reduction.

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