A porous carbon composite material, its preparation method and application

Abstract

Embodiments of the present invention relate to the technical field of composite materials, and specifically disclose a porous carbon composite material, a preparation method and an application thereof. The porous carbon composite material provided by the embodiments of the present invention is prepared by reacting an amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde under catalytic conditions and then carbonizing. COF is grown on the surface of the MOF. The method is simple and does not require operation under a microwave reactor device, solving the problem that the preparation conditions of existing porous carbon composite materials are relatively harsh. Moreover, in the preparation method of the porous carbon composite material provided by the embodiments of the present invention, by using pyrrolidine as a catalyst, a product with a high yield is obtained in a short time under mild conditions. Compared with the methods in the prior art, it is simple, efficient, and less polluting, and has broad market prospects.

Description

Technical Field

[0001] The embodiments of the present invention belong to the technical field of composite materials, and specifically relate to a porous carbon composite material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of social economy and the continuous progress of science and technology, people's requirements for the performance of materials are also getting higher and higher. To meet the needs of production and research and development, more and more types of composite materials have been designed. For example, new porous materials such as metal-organic framework materials (MOF) and covalent organic framework materials (COF) have the advantages of high crystallinity, large surface area, high porosity, better chemical and mechanical stability, etc., and have been widely used in the fields of catalysis, energy storage, gas separation, and nanomedicine.

[0003] At present, based on new porous materials such as MOF and COF, MOF composite materials or COF composite materials prepared by means of metal doping and other means can have good gas adsorption, catalysis and other properties on the basis of maintaining their own characteristics such as the porous structure of the raw materials, and have broad application prospects. These new hybrid materials combine the outstanding characteristics of the MOF and COF structures and have broad application prospects in the fields of catalysis, energy storage, gas separation, and nanomedicine. Therefore, the research and development of porous carbon composite materials with excellent performance based on new porous materials such as MOF and COF have become a research hotspot.

[0004] However, the above-mentioned existing technical solutions have the following defects: Although there are some preparation methods for existing porous carbon composite materials, they generally have the problem of relatively harsh preparation conditions, which affects their practical applications. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a porous carbon composite material. By using pyrrolidine as a catalyst, a core-shell composite material with a high yield is obtained in a short time under mild conditions, and then it is made into a porous carbon composite material after high-temperature anaerobic carbonization, so as to solve the problem that the existing porous carbon composite materials have relatively harsh preparation conditions mentioned in the above background art.

[0006] To achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

[0007] A porous carbon composite material, specifically a composite material with a covalent organic framework material (COF) grown on the surface of a metal-organic framework material (MOF), includes the following raw materials: amino-functionalized bimetallic MOF, melamine, terephthalaldehyde; wherein, the amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde are reacted under catalytic conditions and then carbonized to obtain the porous carbon composite material.

[0008] In an embodiment of the present invention, a bimetallic MOF is synthesized by a simple solvothermal method and then aminated and modified to form an amino-functionalized bimetallic MOF (i.e., aminated MOF). Using the aminated MOF as the core, a covalently linked core-shell composite material is in-situ constructed through a Schiff base reaction. At the same time, by changing the types and proportions of doped metals, the composite material has a high specific surface area, high conductivity, and a hierarchical pore structure containing micropores, mesopores, and macropores. Compared with the methods in the prior art, it is simple and efficient. By growing COF on the surface of MOF, it does not need to be operated under a microwave reactor device, has little pollution, and has broad prospects in practical applications.

[0009] Preferably, the amino-functionalized bimetallic MOF is prepared by adding ethylenediamine to the bimetallic MOF for amino-functionalization. Among them, the bimetallic MOF is prepared by a solvothermal reaction of a metal salt and 2,5-dihydroxyterephthalic acid as raw materials and adding a deprotonating agent.

[0010] As a preference of the above technical solution, in the preparation of the MOF@COF core-shell composite material, the reaction temperature during the heterogeneous interface growth on the surface of the amino-functionalized bimetallic MOF is 70-100 °C, the reaction time is 12-24 hours, and the weight ratio of melamine, terephthalaldehyde, and bimetallic MOF is 2-8:1.5-5:1, and further preferably 2.6-7.8:1.63-4.89:1.

[0011] Another object of the embodiment of the present invention is to provide a preparation method of a porous carbon composite material. The preparation method of the porous carbon composite material includes the following steps:

[0012] 1) Add the amino-functionalized bimetallic MOF to a dimethyl sulfoxide solution in proportion and mix evenly. Then add melamine, terephthalaldehyde, and the catalyst pyrrolidine in sequence, mix and degas, and then react at 70-100 °C for 12-24 h under sealed conditions, and then centrifuge, wash, and dry to obtain the core-shell composite material;

[0013] 2) Mix the core-shell composite material with KOH evenly and carbonize it in a nitrogen atmosphere, wash it to neutrality, and dry it to obtain the porous carbon composite material.

[0014] In an embodiment of the present invention, the specific preparation process of the porous carbon composite material is as follows:

[0015]

[0016] Specifically, in the present invention, 2,5-dihydroxyterephthalic acid is used as a ligand, cobalt nitrate hexahydrate and manganese chloride tetrahydrate are used as metal salts, N,N-dimethylformamide, absolute ethanol, and deionized water are used as a mixed solvent, and triethylamine is used as a deprotonating agent. A powdered cobalt-manganese bimetallic MOF material is prepared by a solvothermal method;

[0017] After the bimetallic MOF material is prepared, it is functionalized with ethylenediamine to form amino-functionalized MnCo-MOF-NH2;

[0018] Using melamine and terephthalaldehyde as raw materials, adding amino-functionalized MnCo-MOF-NH2, and pyrrolidine as a catalyst, heterogeneous interface growth is carried out on the surface of the cobalt-manganese bimetallic organic framework material to prepare a core-shell composite material with a core-shell structure;

[0019] The obtained core-shell composite material is mixed evenly with KOH and then calcined in a N2 atmosphere, and the temperature is raised from room temperature to a specific temperature (600, 700, and 800 °C) at a heating rate of 5 °C·min -1 for calcination, and the calcination time is 2 hours. After washing to neutral and drying, the porous carbon composite material is obtained.

[0020] That is, the preparation method of the porous carbon composite material includes four steps: the preparation of cobalt-manganese bimetallic MOF, the amino-functionalization of cobalt-manganese bimetallic MOF, the preparation of the core-shell composite material, and the high-temperature anaerobic carbonization to prepare the porous carbon composite material.

[0021] Another object of the embodiments of the present invention is to provide a porous carbon composite material prepared by the above preparation method and the application of this porous carbon composite material in gas adsorption and separation, catalysis, and energy storage. In the application in energy storage, the porous carbon composite material can be used to prepare electrode materials.

[0022] Compared with the prior art, the beneficial effects of the embodiments of the present invention are:

[0023] The porous carbon composite material provided by the embodiment of the present invention is prepared by reacting amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde under catalytic conditions and then carbonizing. COF is grown on the surface of the MOF. The method is simple and does not require operation in a microwave reactor device. The prepared porous carbon composite material has a high specific surface area, high conductivity, and a hierarchical pore structure containing micropores, mesopores, and macropores, solving the problem that the preparation conditions of existing porous carbon composite materials are relatively harsh. Moreover, in the preparation method of the porous carbon composite material provided by the embodiment of the present invention, a deprotonating agent is used to accelerate the nucleation rate, and the grain size can be regulated. By using pyrrolidine as a catalyst, a product with a high yield is obtained in a short time under mild conditions. Compared with the methods in the prior art, it is simple, efficient, and less polluting, and can better achieve the transformation of achievements, having broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0025] Figure 1 Scanning electron microscope (SEM) photograph of the powdery cobalt-manganese bimetallic MOF material prepared in Example 1 of the present invention.

[0026] Figure 2 Scanning electron microscope (SEM) photograph of the core-shell composite material prepared in Example 1 of the present invention.

[0027] Figure 3 Scanning electron microscope (SEM) photograph of the core-shell composite material after carbonization at 700 °C prepared in Example 1 of the present invention.

[0028] Figure 4 Low-temperature nitrogen isothermal adsorption and desorption curve of the porous carbon composite material prepared in Example 1 of the present invention.

[0029] Figure 5 Pore size distribution curve of the porous carbon composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments and drawings of the present invention. Obviously, the following embodiments will help those skilled in the art to further understand the embodiments of the present invention, but do not limit the embodiments of the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the embodiments of the present invention, several modifications and improvements can be made. These all belong to the protection scope of the embodiments of the present invention.

[0031] The following describes the specific implementation of the present invention in detail in conjunction with specific embodiments.

[0032] First of all, it should be noted that using MOF and COF as precursors is one of the important means for preparing porous carbon composites in recent years. For example, in the prior art, COF can be prepared separately first, and then mixed and reacted with MOF to prepare porous carbon composites. However, growing MOF on the surface of COF requires using metal ions as nodes. According to experimental observations, the method is relatively harsh and requires operation under a microwave reactor device, and the grown appearance is uneven, which is not as simple as growing COF on the surface of MOF in the embodiments of the present invention.

[0033] Therefore, in order to solve the problems in the prior art, the embodiments of the present invention provide a porous carbon composite, specifically a MOF@COF-derived porous carbon composite with a high specific surface area, high conductivity, and a hierarchical pore structure containing micropores, mesopores and macropores at the same time. The porous carbon composite includes the following raw materials:

[0034] Amino-functionalized bimetallic MOF, melamine, terephthalaldehyde; wherein, the amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde are reacted under catalytic conditions and then carbonized to obtain the porous carbon composite.

[0035] Further preferably, the amino-functionalized bimetallic MOF is prepared by adding ethylenediamine to bimetallic MOF for amino-functionalization.

[0036] Further preferably, the bimetallic MOF is prepared by carrying out a solvothermal reaction with metal salts and 2,5-dihydroxyterephthalic acid as raw materials by adding a deprotonating agent.

[0037] Further preferably, the weight ratio of melamine, terephthalaldehyde, and bimetallic MOF is 2.6 - 7.8:1.63 - 4.89:1.

[0038] Further preferably, the deprotonating agent is selected from alkaline substances such as ammonia water, NaOH solution or mixtures such as triethylamine solution. Here, triethylamine solution is preferred.

[0039] Further preferably, the concentration of the deprotonating agent is 0.012 - 0.024 mol / L. Preferably, triethylamine is used as the deprotonating agent. Correspondingly, the concentration of the triethylamine solution is 0.012 - 0.024 mol / L. The triethylamine solution is a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine. It should be noted that in practical applications, of course, the deprotonating agent can also be a mixed solution of tetrahydrofuran (THF) and deionized water with a volume ratio of 1:1, or a mixed solution with a volume ratio of deionized water∶methanol∶DMF = 1∶1∶1. However, the mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine has a good effect and a high nucleation rate of the bimetallic MOF.

[0040] Further preferably, the two metals in the amino-functionalized bimetallic MOF are selected from any two of Fe, Ni, Cu, Zn, Co, and Mn.

[0041] Further preferably, when preparing the bimetallic MOF with triethylamine as the deprotonating agent, the amino-functionalized bimetallic MOF is prepared by refluxing the bimetallic MOF (here preferably cobalt-manganese bimetallic MOF, that is, Co and Mn are used as the doped metals and MOF-74 is used as the precursor) and ethylenediamine under nitrogen after amino-functionalization.

[0042] It should be noted that the special features of the embodiments of the present invention are as follows: (1) When synthesizing the bimetallic MOF, using the triethylamine solution of the deprotonating agent accelerates the nucleation rate of CoMn-MOF-74, and the grain size decreases with the increase of the triethylamine concentration. By controlling the concentration of triethylamine, the size of the amino-functionalized bimetallic MOF can be controlled. Therefore, the size and morphology of MOF materials with different metals and structures can be regulated. (2) The preparation of the porous carbon composite material uses melamine and terephthalaldehyde as raw materials and pyrrolidine as a catalyst. Under mild conditions, a core-shell composite material with a high yield is obtained in a short time. By growing COF on the surface of the MOF, it is simpler and more efficient than the methods in the prior art, with less pollution and no need to operate under a microwave reactor device.

[0043] Preferably, in the raw materials of the porous carbon composite, the preparation of the bimetallic MOF is as follows: Cobalt(II) nitrate hexahydrate, manganese(II) chloride tetrahydrate and 2,5-dihydroxyterephthalic acid are dissolved in a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine, and ultrasonically mixed evenly. Then the mixed solution is transferred to an autoclave and subjected to solvothermal treatment at 120 - 135 °C for 16 - 24 h, followed by centrifugal washing and vacuum drying to obtain the bimetallic MOF. By using 2,5-dihydroxyterephthalic acid as the ligand, cobalt(II) nitrate hexahydrate and manganese(II) chloride tetrahydrate as metal salts, N,N-dimethylformamide, absolute ethanol and deionized water as the mixed solvent, and triethylamine as the deprotonating agent, a powdered cobalt-manganese bimetallic MOF material is prepared by the solvothermal method, and the size of the material is controlled by controlling the concentration of triethylamine.

[0044] Further preferably, in the raw materials of the porous carbon composite, as a preference of the above technical solution, the pore structure and specific surface area of the bimetallic MOF are controlled by controlling the ratio of 2,5-dihydroxyterephthalic acid and the metal salt. Generally, the molar ratio of the metal salt to 2,5-dihydroxyterephthalic acid is 3.2 - 3.3:1.

[0045] As a preference of the above technical solution, the reaction activity of the porous carbon composite in the electrochemical reaction is controlled by controlling the ratio of the metal salts. Generally, the molar ratio of the metal salts cobalt(II) nitrate hexahydrate and manganese(II) chloride tetrahydrate is 1:9 - 9:1, preferably 1:4 - 4:1.

[0046] Further preferably, in the raw materials of the porous carbon composite, the amino-functionalized bimetallic MOF is an amino-functionalized MOF, and the preparation method is as follows: The prepared bimetallic MOF is added to a mixed solution of ethanol and ethylenediamine, and refluxed under nitrogen for 12 hours. After cooling, the reaction mixture is filtered to produce a yellow precipitate, washed with ethanol, and dried under vacuum at 80 °C.

[0047] As a preference of the above technical solution, the activation of the core-shell composite is controlled by controlling the ratio of the core-shell composite and KOH, and the mass ratio of the core-shell composite to KOH is 1:1 - 3.

[0048] The embodiment of the present invention also provides a preparation method of a porous carbon composite, and the preparation method of the porous carbon composite specifically includes the following steps:

[0049] 1) The amino-functionalized bimetallic MOF is added to the dimethyl sulfoxide solution in proportion and mixed evenly. Melamine, terephthalaldehyde, and the catalyst pyrrolidine are added in sequence. After mixing, nitrogen degassing is carried out, and then the reaction is carried out at 70 - 100 °C for 12 - 24 h under sealed conditions. After centrifugation, washing, and drying, a core-shell composite material (i.e., MOF@COF obtained by growing COF on the surface of MOF) is obtained;

[0050] 2) The core-shell composite material obtained in step 1) is mixed evenly with KOH (of course, NaOH, ZnCl, etc. can also be used, but the effect is not as good as KOH) and then carbonized in a nitrogen atmosphere (heating from room temperature to a specific temperature at a heating rate of 5 °C·min -1 for carbonization, and the carbonization time is 2 hours), washed to neutrality, and dried to obtain the porous carbon composite material, that is, the MOF@COF-derived porous carbon composite material.

[0051] It should be noted that in the preparation method of the porous carbon composite material, by mixing the core-shell composite material evenly with KOH, KOH etches on the surface of the core-shell composite material under high-temperature conditions, and the high temperature reacts with carbon to increase the specific surface area and pore size, thereby facilitating the subsequent preparation of the MOF@COF-derived porous carbon composite material with a high specific surface area, high conductivity, and a hierarchical pore structure containing micropores, mesopores, and macropores at the same time.

[0052] As a preference of the above technical solution, in the preparation method of the porous carbon composite material, the carbonization temperature is 600 - 800 °C. That is, the carbonization of the core-shell composite material is controlled by controlling the carbonization temperature of the core-shell composite material, and the carbonization temperature of the core-shell composite material is 600 - 800 °C. Preferably, the specific temperatures are 600, 700, and 800 °C.

[0053] Further preferably, in the preparation method of the porous carbon composite material, the nitrogen degassing can be carried out by using existing equipment such as an adsorption pump or a vacuum pump to evacuate for 5 - 15 min to meet the vacuum degree requirement in the reaction environment, so as to avoid the adverse effects of air on the reaction through nitrogen degassing. All of the above can be achieved by existing technologies and will not be elaborated here.

[0054] Preferably, the preparation method of the porous carbon composite material includes the following steps:

[0055] 1) In this embodiment, by using melamine and terephthalaldehyde as raw materials and pyrrolidine as a catalyst, heterogeneous interface growth is carried out on the surface of a cobalt-manganese bimetallic metal-organic framework material to prepare a core-shell structured MOF@COF composite porous material. First, melamine, terephthalic acid, and the cobalt-manganese bimetallic metal-organic framework are added to a glass container containing dimethyl sulfoxide solvent, and the above mixture is ultrasonically treated to be mixed evenly. Then pyrrolidine is slowly dropped into the above mixture. Next, the above mixture is degassed with nitrogen for 10 min, and then the container is sealed and reacted at 70 - 100 °C for 12 - 24 h, followed by centrifugation, washing, and drying to obtain the MOF@COF core-shell composite material.

[0056] 2) The obtained MOF@COF core-shell composite material is mixed evenly with KOH and then calcined in a N₂ atmosphere. It is heated from room temperature to a specific temperature (600, 700, and 800 °C) at a heating rate of 5 °C·min⁻¹ for calcination for 2 hours, washed until neutral, and dried to obtain the MOF@COF-derived porous carbon composite material.

[0057] The embodiment of the present invention also provides a porous carbon composite material prepared by using the preparation method of the above porous carbon composite material. After loading an ordered COF on the surface of the MOF, the smooth pure MOF structure has changed significantly, and the surface of the structure tends to be rough. The N atoms contained in the COF material are an effective method to improve the poor electrical conductivity of the MOF. By doping N atoms in the prepared porous carbon composite material, the wettability of the material can be increased, its electron distribution can be changed, thereby promoting the effective contact between the electrode material and the electrolyte. Therefore, the adjustable morphology and microstructure of the obtained porous carbon composite material make it and its derived composite materials have better electrochemical properties.

[0058] The embodiment of the present invention also provides an application of the above porous carbon composite material in the preparation of electrode materials.

[0059] In the above application, preferably, the preparation method of the electrode material is as follows: The obtained porous carbon composite material, a binder (60% polytetrafluoroethylene dispersion), and acetylene black are put into a mortar and ground according to a mass ratio of 8:1:1, and then a small amount of ethanol solution is dropped to form a uniform slurry. The slurry is smeared on dry nickel foam, and the smeared area is 1×1 cm 2 , placed in an oven at 60 °C and dried for 12 h. Finally, the nickel foam is pressed at a pressure of 10 MPa for 10 s to obtain the electrode material as an electrode sheet product.

[0060] In the performance test, the obtained porous carbon composite material was used as the working electrode, mercury oxide as the reference electrode, and a platinum sheet as the counter electrode to form a three-electrode system. Electrochemical tests were carried out using a CHI660E electrochemical workstation from Shanghai Chenhua Company in an electrolyte solution of 3 mol / L KOH. During the test, the scanning voltage range was -0.2 - 0.5 V. The results showed that at a current density of 0.5 Ag －1 the specific capacitance of the prepared MOF@COF-derived porous carbon composite material reached 550 F / g.

[0061] The technical effects of the porous carbon composite material of the embodiments of the present invention are further described below by listing specific examples.

[0062] Example 1

[0063] A porous carbon composite material, the preparation method of which includes the following steps:

[0064] (1) Preparation of bimetallic MOF: Dissolve 0.2328 g of cobalt nitrate hexahydrate, 0.6333 g of manganese chloride tetrahydrate, and 0.198 g of 2,5-dihydroxyterephthalic acid in a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water, and triethylamine (using triethylamine as a deprotonating agent, the corresponding mixed solution is 100 mL, the concentration of triethylamine in the mixed solution is 0.024 mol / L, and other raw materials can be added in equal volume ratios, that is, DMF:absolute ethanol:deionized water = 1:1:1, and 0.0024 mol of triethylamine is added), ultrasonically mix evenly, then transfer the ultrasonically treated mixed solution to an autoclave, carry out solvothermal treatment at 135 °C for 24 h, then centrifuge and wash, and vacuum dry to obtain bimetallic MOF, specifically powdered cobalt-manganese bimetallic MOF.

[0065] (2) Preparation of amine-functionalized MOF: Add the prepared bimetallic MOF to an equal-volume mixed solution of ethanol and ethylenediamine, and reflux under nitrogen for 12 hours. After cooling, filter the reaction mixture to produce a yellow precipitate, wash with ethanol, and dry under vacuum at 80 °C to obtain amine-functionalized MOF, that is, amine-functionalized bimetallic MOF.

[0066] (3) Preparation of core-shell composite material: Add the prepared amino-functionalized MOF into a dimethyl sulfoxide solution, and perform ultrasonic treatment to make it evenly mixed; subsequently, add 0.94 g of melamine and 1.5 g of terephthalaldehyde dissolved in 50 mL of DMSO into the suspension in sequence, and perform ultrasonic treatment on the above mixture to make it evenly mixed. Then, slowly drop 4.67 g of pyrrolidine as a catalyst into the above mixture, and continue to perform ultrasonic treatment on the suspension. After it is evenly mixed, the reaction mixture is degassed with nitrogen for 10 min, then the container is sealed, and after reacting at 70 °C for 12 h, it is centrifuged, washed, and dried to obtain the core-shell composite material.

[0067] (4) Mix the core-shell composite material obtained in step (3) with KOH in equal weight and evenly mix it, then carbonize it in a N₂ atmosphere, and heat it from room temperature to 700 °C at a heating rate of 5 °C·min －1 for carbonization, and the carbonization time is 2 hours. Wash it until it is neutral and dry to obtain the porous carbon composite material, that is, the MOF@COF-derived porous carbon composite material.

[0068] Example 2

[0069] Compared with Example 1, except that when preparing the bimetallic MOF, 0.7916 g of manganese chloride tetrahydrate and 0.198 g of 2,5-dihydroxyterephthalic acid are dissolved in a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine, the others are the same as in Example 1.

[0070] Example 3

[0071] Compared with Example 1, except that when preparing the bimetallic MOF, 0.58 g of cobalt nitrate hexahydrate, 0.3958 g of manganese chloride tetrahydrate and 0.198 g of 2,5-dihydroxyterephthalic acid are dissolved in a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine, the others are the same as in Example 1.

[0072] Example 4

[0073] Compared with Example 1, except that when preparing the bimetallic MOF, 0.931 g of cobalt nitrate hexahydrate, 0.158 g of manganese chloride tetrahydrate and 0.198 g of 2,5-dihydroxyterephthalic acid are dissolved in a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine, the others are the same as in Example 1.

[0074] Example 5

[0075] Compared with Example 1, except that when preparing the bimetallic MOF, 1.164 g of cobalt nitrate hexahydrate and 0.198 g of 2,5-dihydroxyterephthalic acid were dissolved in a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine, the others were the same as Example 1.

[0076] Example 6

[0077] In this example, when detecting the specific capacitance performance of the porous carbon composites prepared in Examples 1-5, specifically, the obtained porous carbon composites were used as the working electrode, mercury oxide was used as the reference electrode, and a platinum sheet was used as the counter electrode to form a three-electrode system. Electrochemical tests were carried out using a CHI660E electrochemical workstation from Shanghai Chenhua Company in an electrolyte solution of 3 mol / L KOH. During the test, the scanning voltage range was -0.2 - 0.5 V.

[0078] Among them, the raw materials of the porous carbon composites prepared in Examples 1-5 can be represented by Table 1.

[0079] Table 1 Raw material ratio table

[0080]

[0081]

[0082] The above samples were prepared according to the methods in the examples, and then the specific capacitance performance was detected using the same steps as above.

[0083] Correspondingly, the detection results of the specific capacitance performance of the porous carbon composites prepared in Examples 1-5 are shown in Table 2.

[0084] Table 2 Specific capacitance performance detection table

[0085] Group Sample Code <![CDATA[Specific capacitance (0.5 Ag -1 )]]> Example 2 Mn-MOF-74@COF-700 426.0 F / g Example 1 <![CDATA[Mn4Co1-MOF-74@COF-700]]> 550 F / g Example 3 <![CDATA[Mn1Co1-MOF-74@COF-700]]> 524.8 F / g Example 4 <![CDATA[Mn1Co4-MOF-74@COF-700]]> 486.4 F / g Example 5 <![CDATA[Co1-MOF-74@COF-700]]> 368.0 F / g

[0086] The results show that at a current density of 0.5 Ag －1 when, the specific capacitance of the porous carbon composite prepared in Example 1, that is, the MOF@COF-derived porous carbon composite, reached 550 F / g, showing broad application prospects in the preparation of electrode materials.

[0087] It should be noted that the porous carbon composite material is obtained by carbonizing the core-shell composite material. The advantages of the carbonized core-shell composite material are as follows: The MOF@COF core-shell composite material has a relatively high carbon content and a uniform pore structure. After carbonization, the carbon material can still maintain the porous structure, and the conductivity after carbonization is better. The specific surface area and porosity of the carbonized product are greatly increased, so that the contact area between the sample and the electrolyte is increased, which is very beneficial to the dispersion of ions between the sample channels and the transfer of electrons. The COF material contains a rich N content, which can also improve the pseudocapacitance. In addition to the double-layer capacitance effect brought by the carbon material after carbonization, there is also the pseudocapacitance effect brought by the metal oxide to improve the electrochemical performance together. Therefore, the specific capacitance of the porous carbon composite material can reach 550 F / g.

[0088] Example 7

[0089] In order to explore the preparation principle of the porous carbon composite material, the bimetallic MOF, core-shell composite material, and porous carbon composite material obtained in Example 1 were characterized by scanning electron microscopy (SEM) in turn. The specific characterization results are shown in Figure 1 、 Figure 2 and Figure 3 .

[0090] Among them, Figure 1 is the scanning electron microscopy (SEM) photograph of the powdery cobalt-manganese bimetallic MOF in Example 1. In Figure 1 , the scale bar is 2 μm. It can be clearly seen that this morphology is formed due to the growth of COF on the surface of the MOF. By using the deprotonating agent triethylamine solution, the nucleation rate of CoMn-MOF-74 is accelerated, and the grain size decreases with the increase of the triethylamine concentration.

[0091] Figure 2 is the scanning electron microscopy (SEM) photograph of the core-shell composite material in Example 1; in Figure 2 , the scale bar is 1 μm. It can be clearly seen the morphology of the core-shell composite material. After amino-functionalization, COF can grow better and more firmly on the surface of the MOF because chemical bonds are generated.

[0092] Figure 3 is the scanning electron microscopy (SEM) photograph of the porous carbon composite material formed by carbonizing the core-shell composite material in Example 1 at 700 °C; in Figure 3 , the scale bar is 1 μm. It can be clearly seen that by mixing the core-shell composite material and KOH evenly, KOH etches on the surface of the core-shell composite material under high-temperature conditions, and the high temperature reacts with carbon to increase the specific surface area and pore size, which is beneficial to the subsequent preparation of MOF@COF-derived porous carbon composite materials with a high specific surface area, high conductivity, and a multi-level pore structure containing micropores, mesopores, and macropores at the same time.

[0093] It should be noted that after loading an ordered COF on the surface of MOF, the smooth pure MOF structure has changed significantly. SEM images show that after loading COF on MOF crystals, the surface of the MOF@COF hybrid tends to be rough. The N atoms contained in the COF material are an effective method to improve the poor electrical conductivity of MOF. Doping N atoms in the composite material can increase the wettability of the material and change its electron distribution, thereby promoting the effective contact between the electrode material and the electrolyte. The adjustable morphology and microstructure of the MOF@COF-derived porous carbon composite make it and its derived composites have better electrochemical performance.

[0094] Example 8

[0095] Compared with Example 1, except that melamine, terephthalaldehyde, and bimetallic MOF were added in a weight ratio of 2.6:4.89:1, the others were the same as in Example 1.

[0096] Example 9

[0097] Compared with Example 1, except that melamine, terephthalaldehyde, and bimetallic MOF were added in a weight ratio of 7.8:1.63:1, the others were the same as in Example 1.

[0098] Example 10

[0099] Compared with Example 1, except that melamine, terephthalaldehyde, and bimetallic MOF were added in a weight ratio of 5:2.5:1, the others were the same as in Example 1.

[0100] Example 11

[0101] Compared with Example 1, except that the concentration of the deprotonating agent was 0.012 mol / L, the others were the same as in Example 1.

[0102] Example 12

[0103] Compared with Example 1, except that the concentration of the deprotonating agent was 0.02 mol / L, the others were the same as in Example 1.

[0104] Example 13

[0105] Compared with Example 1, in the preparation method, except that it was "sealed container, react at 80 °C for 12 h" and "heat from room temperature to 600 °C at a heating rate of 4 °C·min －1 for carbonization for 2 hours", the others were the same as in Example 1.

[0106] Example 14

[0107] Compared with Example 1, in the preparation method, except that it is "sealed container, react at 90 °C for 12 h" and "heat up from room temperature to 700 °C for carbonization at a heating rate of 6 °C·min －1 and the carbonization time is 2 hours", the others are the same as in Example 1.

[0108] Example 15

[0109] Compared with Example 1, in the preparation method, except that it is "sealed container, react at 100 °C for 12 h" and "heat up from room temperature to 800 °C for carbonization at a heating rate of 5 °C·min －1 and the carbonization time is 2 hours", the others are the same as in Example 1.

[0110] Performance detection

[0111] In order to further obtain the material characteristics, the porous carbon composite material prepared in Example 1 of the present invention (labeled as Mn4Co1-MOF-74@COF-700) was subjected to a low-temperature nitrogen isothermal adsorption and desorption experiment. At the same time, the porous carbon composite material prepared in Example 2 (labeled as Mn-MOF-74@COF-700) was used as a comparison, and Mn-MOF-74-700 was used as a reference. The obtained low-temperature nitrogen isothermal adsorption and desorption curve is as Figure 4 shown. The corresponding pore size distribution curve is as Figure 5 shown.

[0112] Among them, the preparation method of Mn-MOF-74-700 is: dissolve 0.7916 g of manganese chloride tetrahydrate and 0.198 g of 2,5-dihydroxyterephthalic acid into a mixed solution of N,N-dimethylformamide, absolute ethanol, deionized water and triethylamine (using triethylamine as a deprotonating agent, the corresponding mixed solution is 100 mL, the concentration of triethylamine in the mixed solution is 0.024 mol / L, and other raw materials can be added in equal volume ratio, that is, DMF:absolute ethanol:deionized water = 1:1:1, add 0.0024 mol of triethylamine), ultrasonically mix evenly, then transfer the ultrasonically mixed solution to an autoclave, carry out solvothermal treatment at 135 °C for 24 h, then centrifuge and wash, and vacuum dry to obtain Mn-MOF-74. After mixing Mn-MOF-74 and KOH evenly by weight, carbonize in a N2 atmosphere, and heat up from room temperature to 700 °C for carbonization at a heating rate of 5 °C·min －1 and the carbonization time is 2 hours, wash to neutral and dry to obtain Mn-MOF-74-700.

[0113] Combined with the data in the figure for analysis, the BET test results of the porous carbon composite material prepared in Example 1 of the present invention can be obtained, as shown in Table 3 specifically.

[0114] Table 3 BET test result table

[0115]

[0116] Combined with the previous data, it can be seen that in the embodiment of the present invention, first, a bimetallic MOF is prepared by a solvothermal synthesis method; secondly, the bimetallic MOF is aminated, and then the aminated bimetallic MOF is added to the synthesis system of a covalent organic framework COF, and a covalently linked MOF@COF core-shell composite material is in-situ constructed by means of a Schiff base reaction between the two components; finally, the MOF@COF core-shell composite material is pyrolyzed and carbonized at high temperature. The composite material prepared by this method has both a high specific surface area and high conductivity, and is a hierarchical pore structure containing micropores, mesopores and macropores at the same time. By regulating the types and proportions of metal ions in the MOF, introducing a variety of metal active sites into the porous material helps to improve the reaction activity and mass transfer advantage of the composite material in an electrochemical reaction. This preparation method has mild experimental conditions, simple process, low pollution and low energy consumption.

[0117] It should be noted that for the MOF without amination modification, there are two metal ions present. After carbonization, the metal ion bonds do not exist but become metal oxides. Good pseudocapacitive behavior can be observed using the porous carbon composite material as an electrode. The bimetallic sample shows enhanced pseudocapacitive characteristics, which may be attributed to the following two reasons: First, the ionic radius of manganese ions is larger than that of cobalt ions, so the spatial size of the sample is increased, and the specific surface area and porosity of the product are greatly increased, thus increasing the contact area between the sample and the electrolyte, which is very beneficial to the dispersion of ions between the sample channels and the transfer of electrons. Second, the mixed metal composition can produce a synergistic effect of multiple different metals, which can improve the conductivity and introduce rich redox reactions.

[0118] As can be seen from the above results, the beneficial effects of the embodiments of the present invention are as follows. In the embodiments of the present invention, the amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde are reacted under catalytic conditions and then carbonized to obtain the porous carbon composite material. COF is grown on the surface of the MOF. The method is simple and does not require operation under a microwave reactor device, solving the problem that the preparation conditions of existing porous carbon composite materials are relatively harsh, and has a broad market prospect. Compared with general MOFs as precursors, bimetallic MOFs can improve the specific surface area. At the same time, the COF grown on the surface can improve the characteristics of traditional MOF-derived porous carbon due to poor wettability with the electrolyte, thereby promoting the diffusion of electrolyte ions. The doping of N atoms in the composite material can increase the wettability of the material and change its electron distribution, thereby promoting the effective contact between the electrode material and the electrolyte. The combination of the two makes the finally obtained composite electrode material have a high specific surface area and high conductivity; in addition, due to the ordered pore structure of MOF and COF itself, the pyrolyzed porous carbon material has an open pore structure and a large number of micropores, and at the same time contains relatively small mesopores, which is conducive to the accumulation of charges and the transmission of electrolyte, and is a prerequisite for obtaining excellent electrochemical performance.

[0119] The above has described the preferred embodiments of the present invention in detail, describing the basic principles, main features, and advantages of the present invention. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Within the scope of knowledge possessed by ordinary technicians in the art, various changes can be made without departing from the purpose of the embodiments of the present invention. It is not necessary and impossible to enumerate all the embodiments here. And the obvious changes or variations derived therefrom are still within the protection scope of the embodiments of the present invention.

Claims

1. A porous carbon composite material, characterized in that The porous carbon composite material is prepared using the following raw materials: amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde; wherein the amino-functionalized bimetallic MOF, melamine, and terephthalaldehyde are reacted under catalytic conditions using pyrrolidine as a catalyst and then carbonized to obtain the porous carbon composite material.

2. The porous carbon composite material according to claim 1, wherein Among the raw materials of the porous carbon composite material, the amine-functionalized bimetallic MOF is prepared by adding ethylenediamine to the bimetallic MOF as a raw material for amine functionalization.

3. The porous carbon composite material according to claim 2, wherein The weight ratio of melamine, terephthalaldehyde and bimetallic MOF is 2-8:1.5-5:

1.

4. The porous carbon composite material according to claim 2, wherein The bimetallic MOF is prepared by using metal salt and 2,5-dihydroxyterephthalic acid as raw materials, adding a deprotonating agent and conducting a solvent thermal reaction.

5. The porous carbon composite material according to claim 4, characterized in that The concentration of the deprotonating agent is 0.012-0.024 mol / L.

6. A method for preparing the porous carbon composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) The amino-functionalized bimetallic MOF was added to a dimethyl sulfoxide solution and mixed evenly. Melamine, terephthalaldehyde, and catalyst pyrrolidine were then added in sequence. After mixing, the mixture was degassed and reacted at 70-100°C for 12-24 hours under sealed conditions. The mixture was centrifuged, washed, and dried to obtain a core-shell composite material. 2) The core-shell composite material is uniformly mixed with KOH, carbonized in a nitrogen atmosphere, washed to neutrality, and dried to obtain the porous carbon composite material.

7. The method for preparing the porous carbon composite material according to claim 6, wherein: In the method for preparing the porous carbon composite material, the carbonization temperature is 600-800° C., and the heating rate is 4-6° C. per minute.

8. Use of the porous carbon composite material according to any one of claims 1 to 5 in the preparation of electrode materials.

9. Use of the porous carbon composite material according to claim 8 in the preparation of electrode materials, characterized in that: The preparation method of the electrode material comprises: grinding the porous carbon composite material with a binder and acetylene black, then adding an ethanol solution dropwise to form a uniform slurry, applying the slurry on dry nickel foam, and pressing at a pressure of not less than 10 MPa after drying to obtain the electrode material.

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