Metallic pyrazine bonded covalent organic framework material as well as preparation method and application thereof

Abstract

The invention provides a pyrazine bonded covalent organic framework material with metallic property as well as a preparation method and application thereof, and belongs to the technical field of catalyst synthesis. According to the covalent organic framework nano material provided by the invention, an aromatic compound containing a pi conjugated system and an organic ligand containing transition metal are selected as construction units, a highly conjugated hcb topological structure is synthesized, and the covalent organic framework nano material is a metallic high-crystallinity framework material; the material has the advantages of high specific surface area, high electron mobility and good thermochemical stability, shows excellent oxygen reduction catalytic performance, is simple and green in preparation method, is easy in condition control, can realize performance regulation and control by changing a construction unit, and is excellent in performance.

Description

Technical Field

[0001] This application relates to the technical field of catalyst synthesis, and particularly relates to a pyrazine-bonded covalent organic framework material with metallicity, and a preparation method and application thereof. Background Art

[0002] Under the dual pressures of the continuous increase in global energy demand and the increasingly severe environmental problems, the development of efficient and sustainable electrocatalytic materials has become a forefront research hotspot. Covalent Organic Frameworks (COFs), with their unique structural advantages such as highly ordered porosity, precisely tunable chemical composition, and excellent stability, have emerged in multiple fields such as gas storage, separation, sensing, and catalysis, showing extremely broad application prospects. Especially in the field of electrocatalysis, the porous structure and high designability of COFs make them ideal catalyst carriers, which can significantly improve the activity and selectivity of reactions, providing strong material support for energy conversion and environmental governance.

[0003] However, traditional COF materials still face many challenges in electrocatalytic applications. For example, their low electrical conductivity and limited number of active sites severely limit the actual application efficiency of the materials in complex electrocatalytic reactions. In recent years, researchers have been committed to optimizing the performance of COFs through various strategies, including introducing heteroatoms, designing special linking bonds, and constructing unique electronic structures. Among them, the pyrazine bond, as a linking method with unique electronic properties, has been proven to significantly improve the electrocatalytic performance of COFs. The introduction of the pyrazine bond not only enhances the electron transport ability of the material but also further expands the pore structure of COFs through its unique structural characteristics, thereby providing more active sites for electrocatalytic reactions.

[0004] So far, a variety of covalent organic framework nanomaterials have been constructed through covalent bonding, including borate esters, triazines, Schiff bases, etc. The building units are connected by covalent bonds and stacked through π-π interactions to form a layered structure with a periodic framework and ordered pores, presenting structural characteristics similar to graphene and h-BN. Exploring the application fields of covalent organic framework materials remains an ongoing challenge. Secondly, there are few studies and reports on the Dirac cone phenomenon in covalent organic framework materials, which have broad development and application prospects. Currently, only the Dirac cone phenomenon of graphene has been confirmed experimentally, and the existence of the Dirac cone endows graphene with many novel physical phenomena and electronic properties, such as half-integer, fractional, and fractal quantum Hall effects, ultra-high mobility, etc. The Dirac cone is a unique electronic band structure that can significantly improve the electrical conductivity and charge transport efficiency of materials, providing a more efficient electron transfer path for electrocatalytic reactions. Therefore, it is expected that introducing metallicity into COFs materials will make their performance in electrocatalytic reactions more outstanding, showing significant catalytic activity and high stability, bringing new breakthroughs to their performance improvement.

[0005] Therefore, it is of practical significance to develop metallic pyrazine-bonded covalent organic framework materials with the Dirac cone phenomenon. Summary of the Invention

[0006] This application provides a metallic pyrazine-bonded covalent organic framework material, its preparation method, and electrocatalytic application to solve the above problems mentioned in the background technology.

[0007] In the first aspect, this application provides a metallic pyrazine-bonded covalent organic framework material, and this covalent organic framework material includes a structural unit shown in Formula I:

[0008]

[0009] In Formula I, "R1" is any one of C, N, and O; "R2" is any one of C, N, and O; "M" is any one of Fe, Co, Ni, Cu, Zn, Cr, Mn, V, and Ti.

[0010] In the second aspect, this application provides a preparation method of a metallic pyrazine-bonded covalent organic framework material. This method is used to prepare the above-mentioned covalent organic framework material, and this covalent organic framework material is synthesized by a solid-phase synthesis method with 2,3,6,7,10,11-hexamminotriphenyl and a metal-containing organic ligand in a molar ratio of 2-6:1-8.

[0011] In Formula I,

[0012] The groups connected to both ends of the structure are

[0013] The groups connected to both ends of the structure are

[0014] Optionally, a method for preparing a pyrazine-bonded covalent organic framework material with metallicity includes the following steps:

[0015] (1) Take 2,3,6,7,10,11-hexamminetriphenyl and a catalyst in a mortar, manually grind for 10 - 15 min, and then add a metal-containing organic ligand and continue to grind for 20 - 25 min to obtain a reaction mixture to be reacted;

[0016] (2) Transfer the reaction mixture to be reacted to a reactor, seal it, and carry out a condensation reaction. After the reaction is completed, naturally cool it to room temperature, perform suction filtration, take the filter cake to obtain a crude covalent organic framework material;

[0017] (3) Wash the crude covalent organic framework material successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at a temperature of 70 - 80 °C for 24 hours to obtain a high-crystalline covalent organic framework material.

[0018] Optionally, the catalyst includes at least one of benzoic anhydride, p-toluenesulfonic acid, and benzoic acid.

[0019] Optionally, the addition amount of the catalyst is in a ratio of 0.5 - 5:1 to the sum of the amounts of substance of 2,3,6,7,10,11-hexamminetriphenyl and the metal-containing organic ligand.

[0020] Optionally, the temperature of the condensation reaction is 80 - 200 °C, and the time is 12 - 168 hours.

[0021] Optionally, the pressure of the condensation reaction is 1 - 6 MPa.

[0022] Optionally, the volume ratio of tetrahydrofuran to methanol is 1:1, and the mass ratio of the crude covalent organic framework material to the sum of the masses of tetrahydrofuran and methanol is 1:1 - 3.

[0023] In a third aspect, the present application provides an application of a pyrazine-bonded covalent organic framework material with metallicity. The covalent organic framework material is the above-mentioned covalent organic framework material or the covalent organic framework material obtained by using the above-mentioned preparation method. The application of the covalent organic framework material as an electrocatalyst for oxygen reduction to produce water.

[0024] Optionally, the half-wave potential of the covalent organic framework material in a 0.1 M KOH electrolyte is ≥ 0.86 V vs. RHE.

[0025] The present application provides a pyrazine-bonded covalent organic framework material with metallicity, its preparation method and application, realizing the synthesis of a pyrazine-bonded covalent organic framework material with metallicity. Compared with the prior art, it has the following beneficial effects:

[0026] (1) In the present application, aromatic compounds containing π-conjugated systems and organometallic ligands containing metals are selected as building units to synthesize a highly conjugated hcb topological structure (with 2,3-connected nodes, usually manifested as a six-connected topological network), which is a highly crystalline framework material with metallicity, having a high specific surface area, high electron mobility and good thermochemical stability, and exhibiting excellent metallicity and oxygen reduction catalytic performance.

[0027] (2) First, 2,3,6,7,10,11-hexaminotriphenyl and a catalyst are ground in a mortar, and then an organometallic ligand containing a metal is added and ground continuously, reducing the particle sizes of the reaction raw materials and the catalyst, and at the same time making the particle size distribution of the reaction raw materials and the catalyst more uniform, thereby improving the efficiency of the subsequent condensation reaction and the yield and quality of the covalent organic framework material. Through the condensation reaction, a highly conjugated hcb topological structure and a highly crystalline covalent organic framework material are synthesized. Metal atoms and pyrazine bonds are introduced into the covalent organic framework material at the same time. The introduction of pyrazine bonds not only enhances the electron transport ability of the material, but also further expands the pore structure of the COFs through its unique structural characteristics, thus providing more active sites for the electrocatalytic reaction. At the same time, the heterocyclic compound containing a highly π-conjugated system in M-Pz-COF and the special d orbitals of transition metals act synergistically, and this structure has a Dirac cone phenomenon, which is beneficial to promoting charge transfer at the electrode / electrolyte interface.

[0028] (3) The novel covalent organic framework material prepared in the present application can be observed to present a regular two-dimensional thin nanosheet shape from the microscopic structure, providing a large specific surface area, exposing more active sites, enhancing the electrocatalytic oxygen reduction response. When this catalyst is used for the application of oxygen reduction to produce water, the half-wave potential in 0.1M KOH electrolyte is not lower than 0.86V vs. RHE, making the covalent organic framework material easy to react as an electrocatalyst and the electrode material having good activity.

[0029] (4) The preparation method provided by the present application is simple, green, the conditions are easy to control, and the performance can be regulated by changing the building units, and the performance is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 Schematic diagram of the synthesis route of the Cu-Pz-COF framework material provided in Embodiment 1 of the present application;

[0032] Figure 2 Schematic diagram of the structure of the Cu-Pz-COF framework material provided in Embodiment 1 of the present application;

[0033] Figure 3 X-ray powder diffraction pattern of the Cu-Pz-COF framework material provided in Embodiment 1 of the present application;

[0034] Figure 4 Linear sweep voltammetry curve pattern of electrocatalytic oxygen reduction of the Cu-Pz-COF framework material provided in Embodiment 1 of the present application.

[0035] Figure 5 Energy band calculation pattern of the Cu-Pz-COF framework material provided in Embodiment 1 of the present invention. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following clearly and completely describes the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts also belong to the scope of protection of the present application. In addition, for those steps or conditions of specific technical operations not specified in the embodiments, they are all carried out according to the techniques or conditions described in the general literature in the art or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchases. In addition, it should also be understood that when the terms "include" and / or "comprise" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0037] In a first aspect, the present application provides a pyrazine-bonded covalent organic framework material with metallicity, and the covalent organic framework material includes a structural unit shown in Formula I:

[0038]

[0039] In Formula I, "R1" is any one of C, N, and O; "R2" is any one of C, N, and O; "M" is any one of Fe, Co, Ni, Cu, Zn, Cr, Mn, V, and Ti.

[0040] In a second aspect, the present application provides a method for preparing a pyrazine-bonded covalent organic framework material with metallicity. This method is used to prepare the above-mentioned covalent organic framework material, which is synthesized by solid-phase synthesis using 2,3,6,7,10,11-hexaminotriphenyl and a metal-containing organic ligand in a molar ratio of 2-6:1-8.

[0041] The structure of 2,3,6,7,10,11-hexaminotriphenyl is

[0042] The structure of the metal-containing organic ligand is

[0043] Specifically, the present application selects an aromatic compound containing a π-conjugated system and a metal-containing organic ligand as building units to synthesize a highly conjugated hcb topological structure (with 2,3-connected nodes, usually showing a six-connected topological network), which is a highly crystalline framework material with metallicity, having a high specific surface area, high electron mobility, and good thermochemical stability, and exhibiting excellent oxygen reduction catalytic performance. The preparation method provided by the present application is simple, green, easy to control conditions, and can achieve performance regulation by changing the building units, with excellent performance.

[0044] Optionally, the method for preparing a pyrazine-bonded covalent organic framework material with metallicity includes the following steps:

[0045] (1) Weigh 2,3,6,7,10,11-hexaminotriphenyl and a catalyst in a mortar, manually grind for 10-15 minutes, then add the metal-containing organic ligand and continue to grind for 20-25 minutes to obtain a reaction mixture to be reacted.

[0046] (2) Transfer the reaction mixture to a reactor, seal it, and carry out a condensation reaction. After the reaction is completed, naturally cool to room temperature, filter by suction, and take the filter cake to obtain a crude covalent organic framework material.

[0047] (3) Wash the crude covalent organic framework material successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at a temperature of 70-80 °C for 24 hours to obtain a highly crystalline covalent organic framework material.

[0048] Specifically, as Figure 1As shown, this is the synthesis route diagram of the covalent organic framework material provided by this application (taking a copper-containing organic ligand as an example). First, 2,3,6,7,10,11-hexamminotriphenyl and a catalyst are placed in a mortar and ground manually. Then, a metal-containing organic ligand is added and grinding is continued to reduce the particle size of the reaction raw materials and the catalyst, and at the same time make the particle size distribution of the reaction raw materials and the catalyst more uniform, thereby improving the efficiency of the subsequent condensation reaction and the yield and quality of the covalent organic framework material. Through the condensation reaction, a highly conjugated hcb topological structure and a highly crystalline covalent organic framework material are synthesized, named: M-Pz-COF, where "M" represents the type of metal atom.

[0049] In this application, by reacting 2,3,6,7,10,11-hexamminotriphenyl with a metal-containing organic ligand, a highly crystalline covalent organic framework material is obtained. At the same time, metal atoms and pyrazine bonds are introduced into the covalent organic framework material. The introduction of pyrazine bonds not only enhances the electron transport ability of the material, but also further expands the pore structure of COFs through its unique two-dimensional structural characteristics, thereby providing more active sites for the electrocatalytic reaction. At the same time, the heterocyclic compound with a highly π-conjugated system in M-Pz-COF and the special d orbitals of transition metals act synergistically. This structure has a Dirac cone phenomenon, which is beneficial to promoting charge transfer at the electrode-electrolyte interface.

[0050] Optionally, the molar ratio of 2,3,6,7,10,11-hexamminotriphenyl to the metal-containing organic ligand is 2-6:1-8.

[0051] Specifically, it is beneficial to the efficient progress of the condensation reaction, helps the efficient generation of pyrazine bonds, improves the quality of the pyrazine bond-connected covalent organic framework material with metallicity, and at the same time makes the covalent organic framework material have a larger specific surface area, exposing more active sites and enhancing the electrocatalytic oxygen reduction response.

[0052] Optionally, the catalyst includes at least one of benzoic anhydride, p-toluenesulfonic acid, and benzoic acid.

[0053] Optionally, the addition amount of the catalyst is in a ratio of 0.5-5:1 to the sum of the amounts of substance of 2,3,6,7,10,11-hexamminotriphenyl and the metal-containing organic ligand.

[0054] Optionally, the temperature of the condensation reaction is 80-200 °C and the time is 12-168 hours.

[0055] Optionally, the pressure of the condensation reaction is 1-6 MPa.

[0056] Specifically, control the temperature, time, and pressure of the condensation reaction, so that the covalent organic framework material can present a regular two-dimensional rectangular thin nanosheet shape in terms of microstructure, providing a large specific surface area and exposing more active sites, which helps the covalent organic framework material to have high activity during the catalytic process.

[0057] Further, the reaction temperature is 100 - 180 °C, and the reaction time is 72 - 120 hours;

[0058] Furthermore, the reaction temperature is 130 - 150 °C, and the reaction time is 96 - 120 hours.

[0059] Optionally, the volume ratio of tetrahydrofuran to methanol is 1:1, and the ratio of the mass of the crude covalent organic framework material to the sum of the masses of tetrahydrofuran and methanol is 1:1 - 3.

[0060] Specifically, tetrahydrofuran and methanol are used to wash the crude covalent organic framework material, so that the impurities therein are dissolved in tetrahydrofuran and / or methanol, realizing the purification of the covalent organic framework material and improving the quality of the covalent organic framework material.

[0061] In a third aspect, the present application provides an application of a pyrazine-bonded covalent organic framework material with metallicity. This covalent organic framework material is the above-mentioned covalent organic framework material or the covalent organic framework material obtained by using the above-mentioned preparation method. This covalent organic framework material is used as an electrocatalyst for oxygen reduction to produce water.

[0062] Optionally, the half-wave potential of the covalent organic framework material in 0.1 M KOH electrolyte ≥ 0.86 V vs. RHE.

[0063] Specifically, for the novel covalent organic framework material prepared in the present application, it can be observed from the microstructure that it presents a regular two-dimensional thin nanosheet shape, providing a large specific surface area and exposing more active sites, enhancing the electrocatalytic oxygen reduction response. When using this catalyst for the application of oxygen reduction to produce water, the half-wave potential in 0.1 M KOH electrolyte is not lower than 0.86 V vs. RHE, making it easy for the electrode to react when the covalent organic framework material is used as an electrocatalyst and the electrode material has good activity.

[0064] The technical solutions of the present application will be described in detail below with specific examples.

[0065] Example 1

[0066] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0067] Preparation of Cu-Pz-COF framework material: Weigh accurately 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 10.33 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 10 min, add 4.68 g of Cu-containing organic ligand (15 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an incubator at 150 °C for 120 hours. After cooling to room temperature, filter by suction. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the highly crystalline covalent organic framework material Cu-Pz-COF with a yield of 82%. The synthetic route diagram is as shown in Figure 1 shown, and the structural schematic diagram of Cu-Pz-COF is as shown in Figure 2 shown.

[0068] Example 2

[0069] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0070] Preparation of Fe-Pz-COF framework material: Weigh accurately 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 2.58 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 12 min, add 4.56 g of Fe-containing organic ligand (15 mmol) and continue grinding for 25 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an incubator at 130 °C for 100 hours. After cooling to room temperature, filter by suction. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 75 °C for 24 hours to obtain the highly crystalline covalent organic framework material Fe-Pz-COF with a yield of 85%.

[0071] Example 3

[0072] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0073] Preparation of Co-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 33 g of benzoic acid and place them in a mortar. After manually grinding for 15 min, add 4.61 g of Co-containing organic ligand (15 mmol) and continue grinding for 25 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an incubator at 80 °C for 48 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 80 °C for 24 hours to obtain the highly crystalline covalent organic framework material Co-Pz-COF with a yield of 78%.

[0074] Example 4

[0075] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0076] Preparation of Ni-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 5 g of benzoic acid and place them in a mortar. After manually grinding for 10 min, add 2.3 g of Ni-containing organic ligand (7.5 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an incubator at 100 °C for 120 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the highly crystalline covalent organic framework material Ni-Pz-COF with a yield of 86%.

[0077] Example 5

[0078] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0079] Preparation of Zn-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 5 g of benzoic anhydride and place them in a mortar. After manually grinding for 10 min, add 1.57 g of Zn-containing organic ligand (5 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an incubator at 80 °C for 168 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the highly crystalline covalent organic framework material Zn-Pz-COF with a yield of 82%.

[0080] Example 6

[0081] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0082] Preparation of Cr-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 5.28 g of benzoic anhydride and place them in a mortar. After manually grinding for 10 min, add 0.50 g of Cr-containing organic ligand (1.67 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an oven at 150 °C for 120 hours. After cooling to room temperature, transfer it to a constant-temperature oven and keep it at 100 °C for 48 h. Turn off the oven. After the oven cools to room temperature, wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the high-crystalline covalent organic framework material Cr-Pz-COF with a yield of 78%.

[0083] Example 7

[0084] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0085] Preparation of Mn-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 5 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 10 min, add 1.52 g of Mn-containing organic ligand (15 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen torch and react in an oven at 150 °C for 120 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 75 °C for 24 hours to obtain the high-crystalline covalent organic framework material Mn-Pz-COF with a yield of 79%.

[0086] Example 8

[0087] A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0088] Preparation of V-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 5 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 10 min, add 4.49 g of V-containing organic ligand (15 mmol) and continue grinding for 20 min to evenly disperse the solids. Seal the ampoule bottle with a high-temperature hydrogen flame gun and react in an incubator at 150 °C for 120 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the highly crystalline covalent organic framework material V-Pz-COF with a yield of 79%.

[0089] Example 9

[0090] A method for preparing a pyrazine-bonded covalent organic framework material with metallicity, the method comprising the following steps:

[0091] Preparation of Ti-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 5 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 10 min, add 2.96 g of Ti-containing organic ligand (10 mmol) and continue grinding for 20 min to evenly disperse the solids. Seal the ampoule bottle with a high-temperature hydrogen flame gun and react in an incubator at 150 °C for 120 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 75 °C for 24 hours to obtain the highly crystalline covalent organic framework material Ti-Pz-COF with a yield of 76%.

[0092] Experimental Example 1

[0093] Through the solutions provided in Examples 1 to 9, the pyrazine-bonded covalent organic framework material with metallicity of the present application can be successfully synthesized. Taking the Cu-Pz-COF framework material as an example, the structure of the covalent organic framework material provided in Example 1 of the present application was characterized by an X-ray diffractometer, and the X-ray diffraction pattern of the Cu-Pz-COF framework material is as Figure 3 shown. The strong peak at about 5° belongs to the pore size peak, and the peak at about 27° represents the interlayer stacking of the (001) crystal plane, indicating the synthesis of a two-dimensional porous material, and at the same time indicating that the Cu-Pz-COF framework material is a highly crystalline covalent organic framework material.

[0094] Experimental Example 2

[0095] Electrochemical performance test:

[0096] Preparation of Cu-Pz-COF framework material as a working electrode: Accurately weigh 5 mg of the Cu-Pz-COF framework material provided in Example 1 into a 5 mL centrifuge tube, add 1 mL of a mixed solution of nafion (perfluorosulfonic acid-based polymer) and ethanol (volume ratio of nafion to ethanol is 1:9) thereto, and ultrasonicate for 2 hours to obtain a homogeneous ink solution. Accurately measure 10 μL of the ink solution and uniformly coat it into a carbon paper substrate of 1*1 cm 2 , and dry it at 65 °C for 1 hour to obtain the required working electrode.

[0097] Electrochemical performance test of Cu-Pz-COF framework material: Prepare 0.1 M KOH electrolyte solution and perform tests using a three-electrode system. First, introduce Ar gas for 30 min to remove air in the electrolyte, and then introduce O2 for 30 min to saturate it with oxygen. In the test environment, continuously introduce O2 at a flow rate of 5 mL / min to keep it in an oxygen-saturated state for a long time. Perform cyclic voltammetry scanning tests between 0 V - 1.2 V vs. RHE at a scanning rate of 50 mV / s for 50 cycles, then perform cyclic scanning between 0 V - 1.2 V vs. RHE at a scanning rate of 20 mV / s for 100 cycles to activate the electrode, and subsequently perform linear sweep voltammetry tests between 0 V - 1.2 V vs. RHE at a scanning rate of 5 mV / s. The linear sweep voltammogram is as shown in Figure 4 .

[0098] As shown in Figure 4 , the half-wave potential of the Cu-Pz-COF framework material in 0.1 M KOH electrolyte solution is not lower than 0.86 V vs. RHE, indicating that when the covalent organic framework material is used as an electrocatalyst, the electrode is easy to react and the electrode material has good activity.

[0099] Experimental Example 3

[0100] Metallic property verification

[0101] Use Materials Studio (MS) software to calculate the band structure of the Cu-Pz-COF framework material provided in Example 1 to confirm the existence of metallic properties. The obtained results are as shown in Figure 5 .

[0102] As can be seen from Figure 5 , in the band calculation, the Fermi level is specified as 0 eV as the reference point of energy. Therefore, this calculation shows that the band intersects with the Fermi level and the band curve crosses the Fermi level, indicating that the Cu-Pz-COF framework material shows metallic properties and has excellent electrical conductivity.

[0103] Comparative Example 1

[0104] The difference from Example 1 lies in:

[0105] A preparation method of a pyrazine-linked covalent organic framework material with metallicity, the method comprising the following steps:

[0106] Preparation of Cu-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 10.33 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 10 min, add 19.5 g of a Cu-containing organic ligand (62.5 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen flame gun and react in an incubator at 150 °C for 120 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the highly crystalline covalent organic framework material Cu-Pz-COF with a yield of 65%.

[0107] Comparative Example 2

[0108] The difference from Example 1 lies in:

[0109] A preparation method of a pyrazine-linked covalent organic framework material with metallicity, the method comprising the following steps:

[0110] Preparation of Cu-Pz-COF framework material: Accurately weigh 4.77 g of 2,3,6,7,10,11-hexamminotriphenyl (15 mmol) and 10.33 g of p-toluenesulfonic acid and place them in a mortar. After manually grinding for 10 min, add 0.76 g of a Cu-containing organic ligand (2.45 mmol) and continue grinding for 20 min to make the solids disperse evenly. Seal the ampoule bottle with a high-temperature hydrogen flame gun and react in an incubator at 150 °C for 120 hours. After cooling to room temperature, perform suction filtration. Wash the obtained brownish-black powder successively with tetrahydrofuran and methanol, and then dry it in a vacuum drying oven at 70 °C for 24 hours to obtain the highly crystalline covalent organic framework material Cu-Pz-COF with a yield of 62%.

[0111] Experimental Example 4

[0112] Electrochemical performance test: Using the same method as in Experimental Example 2, perform electrochemical performance tests on the Cu-Pz-COF framework materials obtained from Comparative Example 1 and Comparative Example 2, and compare them with Example 1. Each experiment is set with at least three parallel tests, and the results are shown in Table 1.

[0113] Table 1

[0114] Example 1 Comparative Example 1 Comparative Example 2 Half-wave potential / V vs. RHE 0.86 0.7 0.72

[0115] As can be seen from Table 1, the half-wave potential of the Cu-Pz-COF framework material provided in Example 1 of this application is 0.86 V, which has a higher half-wave potential compared to Comparative Example 1 and Comparative Example 2. This indicates that the covalent organic framework material with metallicity and high crystallinity generated by reacting 2,3,6,7,10,11-hexaminotriphenyl and a metal-containing organic ligand in a specific molar ratio has a high specific surface area and high electron mobility, and thus has excellent metallicity and oxygen reduction catalytic performance. When used as an electrocatalyst, the electrode is prone to reaction while the electrode material has good activity.

[0116] Moreover, compared with the half-wave potential of 0.83 V vs. RHE of 20% Pt / C commonly used in the prior art, the half-wave potential of the pyrazine-bonded covalent organic framework material with metallicity provided in this application is still relatively high. By introducing metal atoms and pyrazine bonds into the covalent organic framework material simultaneously in this application, the introduction of pyrazine bonds not only enhances the electron transport ability of the material, but also further expands the pore structure of COFs through its unique regular two-dimensional rectangular thin nanosheet structure characteristics, thus providing more active sites for the electrocatalytic reaction. At the same time, M-Pz-COF contains a heterocyclic compound with a highly π-conjugated system that synergistically interacts with the special d orbitals of transition metals. This structure has a Dirac cone phenomenon, which is conducive to promoting charge transfer at the electrode / electrolyte interface.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A pyrazine-bonded covalent organic framework material with metallic properties, characterized in that, The pyrazine-bonded covalent organic framework material includes a structural unit shown in Formula I: In Formula I, "R1” is any one of C, N, and O; "R2” is any one of C, N, and O; "M” is any one of Fe, Co, Ni, Cu, Zn, Cr, Mn, V, and Ti.

2. A preparation method of a pyrazine-bonded covalent organic framework material with metallicity, characterized in that, The method is used to prepare the covalent organic framework material described in Claim 1. The covalent organic framework material is synthesized by a solid-phase synthesis method with 2,3,6,7,10,11-hexamminotriphenyl and a metal-containing organic ligand in a molar ratio of 2-6:1-8. In the said Formula I, The groups connected to both ends of the structure are The groups connected to both ends of the structure are 3. The preparation method of the pyrazine-bonded covalent organic framework material with metallicity according to claim 2, wherein, The method includes the following steps: (1) Take 2,3,6,7,10,11-hexamminotriphenyl and a catalyst in a mortar according to the ratio, grind for 10-15 min, and then add the metal-containing organic ligand and continue to grind for 20-25 min to obtain a reaction mixture to be reacted. (2) Transfer the reaction mixture to be reacted to a reactor, seal it, and carry out a condensation reaction. After the reaction is completed, cool it naturally to room temperature, filter by suction, take the filter cake to obtain a crude covalent organic framework material. (3) Wash the crude covalent organic framework material successively with tetrahydrofuran and methanol, and dry it in a vacuum drying oven at a temperature of 70-80 °C for 24 hours to obtain the high-crystalline covalent organic framework material.

4. The preparation method of the pyrazine-bonded covalent organic framework material with metallicity according to claim 3, characterized in that, The catalyst includes at least one of benzoic anhydride, p-toluenesulfonic acid, and benzoic acid.

5. The preparation method of the pyrazine-bonded covalent organic framework material with metallicity according to claim 3, characterized in that, The addition amount of the catalyst is in a ratio of 0.5-5:1 to the sum of the amounts of substance of 2,3,6,7,10,11-hexamminotriphenyl and the metal-containing organic ligand.

6. The preparation method of the pyrazine-bonded covalent organic framework material with metallicity according to claim 3, characterized in that, The temperature of the condensation reaction is 80-200 °C, and the time is 12-168 hours.

7. According to the preparation method of the pyrazine-bonded covalent organic framework material with metallicity described in Claim 3, the pressure of the condensation reaction is 1-6 MPa.

8. The preparation method of the pyrazine-bonded covalent organic framework material with metallicity according to claim 3, wherein The volume ratio of the tetrahydrofuran to the methanol is 1:1, and the mass ratio of the crude covalent organic framework material to the sum of the masses of the tetrahydrofuran and the methanol is 1:1-3.

9. Application of a pyrazine-linked covalent organic framework material with metallicity, characterized in that, The covalent organic framework material is the covalent organic framework material described in Claim 1 above, or the covalent organic framework material obtained by the preparation method described in any one of Claims 2-8. The covalent organic framework material is used as an electrocatalyst for oxygen reduction to produce water.

10. Use of the pyrazine-bonded covalent organic framework material with metallicity according to claim 9, characterized in that, The half-wave potential of the covalent organic framework material in 0.1 M KOH electrolyte is ≥ 0.86 V vs. RHE.

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