Nitrogen-doped multi-level microporous carbon material and preparation method thereof

Abstract

The application relates to a nitrogen-doped multi-level microporous carbon material and a preparation method thereof, and belongs to the technical field of carbon materials. A conjugated microporous polymer of an alkyne porphyrin is obtained by coupling reaction of a halogenated aromatic hydrocarbon containing bromine and an alkyne benzene compound under the joint action of copper and palladium catalysts. By pyrolysis at different temperatures, some functional groups in the polymer are cracked and escape in the form of gas, which continuously forms pores in the carbon skeleton and gradually changes into a nitrogen-doped multi-level microporous carbon material. The nitrogen-doped sites in the structure of the multi-level microporous carbon material generate defect sites and provide a large number of active sites; meanwhile, the multi-level microporous structure forms a three-dimensional through structure between pores, effectively shortening the ion diffusion path; pyrolysis can change the polymer skeleton into a short-range ordered structure, providing an interlayer embedding channel for ions; and the energy storage mechanism of the material is defect adsorption, interlayer embedding and micropore filling respectively.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials, specifically relating to a nitrogen-doped multi-level microporous carbon material, its preparation method, and its application in sodium-ion batteries. Background Technology

[0002] Currently, soft carbon and hard carbon materials are the mainstream anode materials for sodium-ion batteries, but they each have inherent drawbacks. Soft carbon materials have a high degree of graphitization and small interlayer spacing, making it difficult for sodium ions to intercalate and deintercalate, thus limiting capacity. On the other hand, the microstructure and pore size distribution of hard carbon materials are difficult to precisely control, resulting in large fluctuations in electrochemical performance. In addition, they lack structural stability and are prone to pulverization and structural collapse during long-term cycling. Furthermore, hard carbon requires high pyrolysis temperatures, making experimental conditions more demanding.

[0003] Conjugated microporous polymers (CMPs) possess multiple advantages, including flexible molecular structure control, a highly delocalized π-conjugated system allowing for rapid electron migration within the framework, structural stability, and insolubility in electrolytes. These have made them a hot research topic. Heteroatom-doped hierarchical microporous carbon prepared by the pyrolysis of CMPs possesses the advantages of a high specific surface area and a rigid conjugated framework, similar to precursors. The pyrolysis process causes heteroatoms to escape as gas, leaving pores and continuously creating a hierarchical microporous structure. The three-dimensional interconnected structure between these pores further increases the specific surface area. Furthermore, CMPs are rich in nitrogen atoms, which, after pyrolysis, form high-content, highly dispersed nitrogen-doped sites within the carbon framework, providing numerous sodium-storage active sites. This results in higher reversible capacity and faster reaction kinetics compared to hard and soft carbons. As electrode materials, they exhibit ultra-high capacity, excellent rate performance, and long-cycle stability, making them highly promising electrode materials. Therefore, the sodium-storage performance of CMPs can be effectively improved through high-temperature pyrolysis.

[0004] Based on the above analysis, this invention prepares an alkynyl porphyrin conjugated microporous polymer material, which is then pyrolyzed at high temperatures to form a nitrogen-doped hierarchical microporous carbon material, which is used as a negative electrode material for sodium-ion batteries. The material is rich in nitrogen doping, and the nitrogen-doped sites can form defects, thus providing a large number of active sites. Simultaneously, the hierarchical microporous structure creates a three-dimensional interconnected structure between pores, providing a large surface area and effectively shortening the ion transport path. The short-range ordered layered structure provides stable interlayer insertion channels for sodium ions, effectively promoting rapid insertion and extraction. The nitrogen-doped hierarchical microporous carbon material structure provides three mechanisms for sodium ion storage: defect adsorption, interlayer insertion, and micropore filling, exhibiting excellent rate performance and cycle stability. Summary of the Invention

[0005] The key problem this invention aims to solve is to select a material that can replace soft carbon and hard carbon, addressing their respective issues of capacity limitation, difficult preparation conditions, and poor structural stability during cycling, and further optimizing their electrochemical performance in sodium-ion storage. The specific technical solution is as follows:

[0006] A method for preparing nitrogen-doped hierarchical microporous carbon materials involves using bromine-containing haloaromatic hydrocarbons and alkynylbenzene compounds as starting materials, and conducting a cross-coupling reaction under the combined action of palladium and copper catalysts, and in an alkaline environment with polar solvents and inert gas as reaction conditions, to obtain alkynylporphyrin conjugated microporous polymers. The obtained polymers are then subjected to high-temperature pyrolysis in an inert gas environment to gradually transform the material into nitrogen-doped porous carbon materials.

[0007] Preferably, the alkynylbenzene compound is selected from 1,3,5-triethynylbenzene, hexaethynylbenzene, or 1,4-diethynylbenzene, and the bromine-containing haloaromatic hydrocarbon is selected from m-tetra(p-bromophenyl)porphyrin, and the molar ratio of the bromine-containing haloaromatic hydrocarbon to the alkynylbenzene compound is 1:1 to 10:1.

[0008] Preferably, the polar solvent is selected from at least one of N,N-dimethylformamide, tetrahydrofuran, toluene, and pyridine, and the alkaline environment is provided by triethylamine.

[0009] Preferably, the palladium catalyst is selected from Pd(PPh3)4, Pd(PPh3)2Cl2 or Pd(dppf)Cl2, the copper catalyst is selected from CuI, CuBr, CuCl or Cu(OTf)2, and the molar ratio of the palladium catalyst to the copper catalyst is 1:0.5-1:1.

[0010] Preferably, the cross-coupling reaction temperature is 80℃-100℃, and the stirring reaction time is 24 h-72 h.

[0011] Preferably, the inert gas is selected from nitrogen, helium, and argon.

[0012] The high-temperature pyrolysis temperature is 300℃-800℃ (preferably 600-700℃), the pyrolysis time is 2-6 hours, and the pyrolysis heating rate is 5-10℃ / min.

[0013] Further, the specific steps include the following:

[0014] Step a: Dissolve m-tetra(p-bromophenyl)porphyrin and 1,3,5-triethynylbenzene in N,N-dimethylformamide and triethylamine. After purging with argon gas for 15 minutes, add Pd(PPh3)4 and CuI sequentially. Purge with argon gas again for 15 minutes. Seal the system and stir at 100°C for 72 hours. After the reaction, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder. The reaction mixture consists of 0.3 mmol m-tetra(p-bromophenyl)porphyrin and 0.2 mmol 1,3,5-triethynylbenzene, 15 mL N,N-dimethylformamide, 15 mL triethylamine, 0.03 mmol Pd(PPh3)4, and 0.03 mmol CuI.

[0015] Step b: The alkynyl porphyrin conjugated microporous polymer powder obtained in step a is placed in a tube furnace and pyrolyzed at different temperatures in an inert gas environment to gradually transform it into nitrogen-doped porous carbon material.

[0016] The inert gas environment described in step b is selected from nitrogen, helium, and argon.

[0017] The pyrolysis of the alkyne-based conjugated microporous polymer prepared in this invention can retain the high specific surface area of ​​the precursor, forming a large number of ultra-micropores and hierarchical micropore structures with smaller pore size, more uniform distribution, and interconnection. The pores are interconnected and have a three-dimensional interconnected structure, which greatly shortens the ion diffusion path. The uniformly dispersed nitrogen doping formed after pyrolysis creates a large number of defect sites. These defects can provide a large number of active centers, effectively improving sodium storage capacity and reaction kinetics. When used as a sodium-ion battery anode material, it has a capacity retention rate of over 90% after 500 cycles under low current, which is significantly better than most commercial soft carbon and hard carbon materials currently available. Attached Figure Description

[0018] Figure 1 The pore size distribution of the nitrogen-doped hierarchical microporous carbon prepared in Example 1 of this invention.

[0019] Figure 2 The pore size distribution of the nitrogen-doped hierarchical microporous carbon prepared in Example 2 of this invention.

[0020] Figure 3 The pore size distribution of the nitrogen-doped hierarchical microporous carbon prepared in Example 3 of this invention.

[0021] Figure 4 The pore size distribution of the nitrogen-doped hierarchical microporous carbon prepared in Example 4 of this invention.

[0022] Figure 5 The pore size distribution of the nitrogen-doped hierarchical microporous carbon prepared in Example 5 of this invention.

[0023] Figure 6 The pore size distribution of the nitrogen-doped hierarchical microporous carbon prepared in Example 6 of this invention.

[0024] Figure 7 The nitrogen-doped hierarchical microporous carbon material prepared in Example 1 of this invention is used as a negative electrode for a sodium-ion battery with a capacity of 100 mA g. -1 The following is a graph showing the cyclic performance.

[0025] Figure 8 The nitrogen-doped hierarchical microporous carbon material prepared in Example 2 of this invention is used as a 100 mA g anode in a sodium-ion battery. -1 The following is a graph showing the cyclic performance.

[0026] Figure 9 The nitrogen-doped hierarchical microporous carbon material prepared in Example 3 of this invention is used as a 100 mA g anode in a sodium-ion battery. -1 The following is a graph showing the cyclic performance.

[0027] Figure 10 The nitrogen-doped hierarchical microporous carbon material prepared in Example 4 of this invention is used as a 100 mA g anode for sodium-ion batteries. -1 The following is a graph showing the cyclic performance.

[0028] Figure 11 The nitrogen-doped hierarchical microporous carbon material prepared in Example 5 of this invention is used as a 100 mA g anode for sodium-ion batteries. -1 The following is a graph showing the cyclic performance.

[0029] Figure 12 The nitrogen-doped hierarchical microporous carbon material prepared in Example 6 of this invention is used as a 100 mA g anode in a sodium-ion battery. -1 The following is a graph showing the cyclic performance.

[0030] Figure 13 The rate performance of the nitrogen-doped hierarchical microporous carbon materials prepared in Examples 1-6 of this invention as anodes in sodium-ion batteries at different current densities is shown in the graphs. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. The pore size distribution was measured using a Micromeritics ASAP 2460 fully automated specific surface area and porosity analyzer (USA).

[0032] This invention provides a nitrogen-doped hierarchical microporous carbon material and its preparation method. The material is characterized by abundant nitrogen doping, forming numerous defect sites and thus providing a large number of active sites; a hierarchical microporous coexistence structure with interconnected and three-dimensionally connected pores, resulting in a large surface area and shortened ion transport paths; a short-range ordered layered structure that provides stable interlayer insertion channels for sodium ions, effectively promoting rapid insertion and extraction; and excellent structural stability during cycling, effectively mitigating volume expansion and significantly improving the rate performance and cycle life of sodium-ion batteries.

[0033] In this invention, the nitrogen-doped multi-level microporous carbon material can be represented as Alk-Por-CMP-300, Alk-Por-CMP-400, Alk-Por-CMP-500, Alk-Por-CMP-600, Alk-Por-CMP-700 and Alk-Por-CMP-800 according to different pyrolysis temperatures.

[0034] In this invention, the nitrogen-doped multi-level microporous carbon material uses nitrogen doping to provide defect sites, and ions are stored through three mechanisms: defect adsorption, interlayer embedding, and micropore filling.

[0035] Its preparation method includes the following steps:

[0036] Step a: Dissolve bromine-containing haloaromatic hydrocarbons and alkynylbenzene compounds in N,N-dimethylformamide and triethylamine. After purging with argon gas for 15 minutes, add Pd(PPh3)4 and CuI sequentially, and purge with argon gas again for 15 minutes. Seal the above system and stir at 100°C for 72 hours. After the reaction is complete, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0037] Step b: The alkynyl porphyrin conjugated microporous polymer powder obtained in step a is placed in a tube furnace and pyrolyzed at different temperatures in an inert gas environment to gradually transform it into nitrogen-doped multi-level microporous carbon material.

[0038] Specifically, in some embodiments of the present invention, the different temperatures are selected from 300°C to 800°C.

[0039] Specifically, in some embodiments of the present invention, the pyrolysis holding time is selected from 2-6 hours.

[0040] Specifically, in some embodiments of the present invention, the heating rate of the pyrolysis temperature is selected from 5-10℃ / min.

[0041] Specifically, in some embodiments of the present invention, the inert gas environment is selected from nitrogen, helium and argon.

[0042] The present invention will be further described below through specific embodiments.

[0043] In the following specific embodiments, operations without specified conditions are performed under standard conditions or conditions recommended by the manufacturer. Raw materials without specified manufacturers and specifications are all commercially available products.

[0044] Example 1: Synthesis of Alk-Por-CMP-300

[0045] Step a: Accurately weigh 0.15 mmol of m-tetra(p-bromophenyl)porphyrin and 0.1 mmol of 1,3,5-triethynylbenzene and dissolve them in a mixed solution of 7.5 mL of N,N-dimethylformamide and 7.5 mL of triethylamine. After purging with argon gas for 15 minutes, add 0.03 mmol of Pd(PPh3)4 and 0.03 mmol of CuI sequentially. After purging with argon gas again for 15 minutes, seal the above system and stir the reaction at 100 °C for 72 hours. After the reaction is completed, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0046] Step b: Place the alkynyl porphyrin conjugated microporous polymer powder obtained in step a into a tube furnace and heat it from 30°C to 300°C at a heating rate of 5°C / min under an argon atmosphere, holding it at that temperature for 2 hours, so that the alkynyl porphyrin conjugated microporous polymer is transformed into nitrogen-doped hierarchical microporous carbon material.

[0047] Figure 1 The pore size distribution results show that the pore size of the nitrogen-doped hierarchical microporous carbon material prepared in this example is 1.26 nm-2.0 nm.

[0048] Example 2 Synthesis of Alk-Por-CMP-400

[0049] Step a: Accurately weigh 0.15 mmol of m-tetra(p-bromophenyl)porphyrin and 0.1 mmol of 1,3,5-triethynylbenzene and dissolve them in a mixed solution of 7.5 mL of N,N-dimethylformamide and 7.5 mL of triethylamine. After purging with argon gas for 15 minutes, add 0.03 mmol of Pd(PPh3)4 and 0.03 mmol of CuI sequentially. After purging with argon gas again for 15 minutes, seal the above system and stir the reaction at 100 °C for 72 hours. After the reaction is completed, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0050] Step b: Place the alkynyl porphyrin conjugated microporous polymer powder obtained in step a into a tube furnace and heat it from 30°C to 400°C at a heating rate of 5° / min under an argon atmosphere for 2 hours, so that the alkynyl porphyrin conjugated microporous polymer is transformed into nitrogen-doped hierarchical microporous carbon material.

[0051] Figure 2 The pore size distribution results show that the nitrogen-doped hierarchical microporous carbon material prepared in this example has both ultramicropores (<0.7 nm) with a pore size of 0.64 nm and micropores (1.26 nm-2.0 nm) with pore sizes of 1.26 nm and 2.0 nm.

[0052] Example 3 Synthesis of Alk-Por-CMP-500

[0053] Step a: Accurately weigh 0.15 mmol of m-tetra(p-bromophenyl)porphyrin and 0.1 mmol of 1,3,5-triethynylbenzene and dissolve them in a mixed solution of 7.5 mL of N,N-dimethylformamide and 7.5 mL of triethylamine. After purging with argon gas for 15 minutes, add 0.03 mmol of Pd(PPh3)4 and 0.03 mmol of CuI sequentially. After purging with argon gas again for 15 minutes, seal the above system and stir the reaction at 100 °C for 72 hours. After the reaction is completed, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0054] Step b: Place the alkynyl porphyrin conjugated microporous polymer powder obtained in step a into a tube furnace and heat it from 30°C to 500°C at a heating rate of 5° / min under an argon atmosphere for 2 hours, so that the alkynyl porphyrin conjugated microporous polymer is transformed into nitrogen-doped hierarchical microporous carbon material.

[0055] Figure 3 The pore size distribution results show that the nitrogen-doped hierarchical microporous carbon material prepared in this example has both ultramicropores (<0.7 nm) with a pore size of 0.67 nm and micropores (0.7 nm-2.0 nm) with a pore size of 1.2 nm.

[0056] Example 4 Synthesis of Alk-Por-CMP-600

[0057] Step a: Accurately weigh 0.15 mmol of m-tetra(p-bromophenyl)porphyrin and 0.1 mmol of 1,3,5-triethynylbenzene and dissolve them in a mixed solution of 7.5 mL of N,N-dimethylformamide and 7.5 mL of triethylamine. After purging with argon gas for 15 minutes, add 0.03 mmol of Pd(PPh3)4 and 0.03 mmol of CuI sequentially. After purging with argon gas again for 15 minutes, seal the above system and stir the reaction at 100 °C for 72 hours. After the reaction is completed, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0058] Step b: The alkynyl porphyrin conjugated microporous polymer powder obtained in step a is placed in a tube furnace and heated from 30°C to 600°C at a heating rate of 5° / min under an argon atmosphere, and held at that temperature for 2 hours, so that the alkynyl porphyrin conjugated microporous polymer is transformed into nitrogen-doped hierarchical microporous carbon material.

[0059] Figure 4 The pore size distribution results show that the nitrogen-doped hierarchical microporous carbon material prepared in this example has both ultramicropores (<0.7 nm) with a pore size of 0.67 nm and micropores (0.7 nm-2.0 nm) with a pore size of 1.17 nm.

[0060] Example 5 Synthesis of Alk-Por-CMP-700

[0061] Step a: Accurately weigh 0.15 mmol of m-tetra(p-bromophenyl)porphyrin and 0.1 mmol of 1,3,5-triethynylbenzene and dissolve them in a mixed solution of 7.5 mL of N,N-dimethylformamide and 7.5 mL of triethylamine. After purging with argon gas for 15 minutes, add 0.03 mmol of Pd(PPh3)4 and 0.03 mmol of CuI sequentially. After purging with argon gas again for 15 minutes, seal the above system and stir the reaction at 100 °C for 72 hours. After the reaction is completed, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0062] Step b: Place the alkynyl porphyrin conjugated microporous polymer powder obtained in step a into a tube furnace and heat it from 30°C to 700°C at a heating rate of 5° / min under an argon atmosphere for 2 hours, so that the alkynyl porphyrin conjugated microporous polymer is transformed into nitrogen-doped hierarchical microporous carbon material.

[0063] Figure 5The pore size distribution results show that the nitrogen-doped hierarchical microporous carbon material prepared in this example has both ultramicropores (<0.7 nm) with a pore size of 0.58 nm and micropores (0.7 nm-2.0 nm) with a pore size of 0.80-1.26 nm.

[0064] Example 6 Synthesis of Alk-Por-CMP-800

[0065] Step a: Accurately weigh 0.15 mmol of m-tetra(p-bromophenyl)porphyrin and 0.1 mmol of 1,3,5-triethynylbenzene and dissolve them in a mixed solution of 7.5 mL of N,N-dimethylformamide and 7.5 mL of triethylamine. After purging with argon gas for 15 minutes, add 0.03 mmol of Pd(PPh3)4 and 0.03 mmol of CuI sequentially. After purging with argon gas again for 15 minutes, seal the above system and stir the reaction at 100 °C for 72 hours. After the reaction is completed, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder.

[0066] Step b: Place the alkynyl porphyrin conjugated microporous polymer powder obtained in step a into a tube furnace and heat it from 30°C to 800°C at a heating rate of 5° / min under an argon atmosphere for 2 hours, so that the alkynyl porphyrin conjugated microporous polymer is transformed into nitrogen-doped hierarchical microporous carbon material.

[0067] Figure 6 The pore size distribution results show that the nitrogen-doped hierarchical microporous carbon material prepared in this example has both ultramicropores (<0.7 nm) with a pore size of 0.46-0.58 nm and micropores (0.7 nm-2.0 nm) with a pore size of 0.85-1.17 nm.

[0068] Example 7: Assemble a 2032 type coin cell sodium-ion battery

[0069] The nitrogen-doped hierarchical microporous carbon materials prepared in Examples 1-6 were used to prepare anodes for sodium-ion batteries. The hierarchical microporous carbon material, Ketjen black, and polyvinylidene fluoride were mixed in a ratio of 7:2:1, and the sample was coated onto copper foil. The mixture was then cut into discs with a radius of 0.6 cm and dried in a vacuum oven at 100°C for 8 h, and used as the working electrode. These were assembled into 2032 coin cells, with pure sodium foil used as the counter electrode, separated from the working electrode by a glass fiber separator. The electrolyte was 1M NaPF6-EMC / FEC / PC (24:1:25V%). The batteries were assembled in an argon-filled glove box, where the moisture and oxygen concentrations were below 0.1 ppm.

[0070] Cyclic performance test: at 100 mA g -1At a current density of 0.01 V-3 V, the average coulombic efficiency and capacity retention were obtained by using the Xinwei Battery Testing System to conduct 500 cycles of testing within the range of 0.01 V-3 V. Figures 7-9 The Alk-Por-CMP-300, Alk-Por-CMP-400, and Alk-Por-CMP-500 materials prepared in Examples 1-3 are shown in 100 mA g. -1 After 500 cycles, the capacity was almost zero. This may be because the low-temperature pyrolysis resulted in incomplete pyrolysis, with the carbon skeleton still primarily composed of organic polymers, exhibiting extremely poor conductivity. Consequently, abundant micropores / micropores did not appear. Figure 10 The Alk-Por-CMP-600 material prepared in Example 4 was shown to be at 100 mA g. -1 After 500 cycles, the capacity can be maintained at 150 mAh g. -1 The initial discharge capacity is 500 mAh g. -1 The second cycle capacity was 168 mAh g. -1 The second capacity decrease was mainly due to the formation of a solid electrolyte interphase (SEI) membrane during the first cycle, which consumed a large number of ions. After 500 cycles, the capacity retention rate was about 89%. Figure 11 The Alk-Por-CMP-700 material prepared in Implementation Case 5 was tested at 100 mA g. -1 After 500 cycles, the capacity can be maintained at 250 mAh g. -1 The discharge capacity during the first cycle was 760 mAh g. -1 It retains more than 90% of its capacity after 500 cycles, surpassing most commercial soft and hard carbon materials currently available. Figure 12 The Alk-Por-CMP-800 material prepared in Implementation Case 6 was tested at 100 mA g. -1 After 300 cycles, the capacity rapidly decays to 0, mainly because the pyrolysis of the material at 800℃ produces a large number of micropores, which cause the structure to collapse due to the continuous insertion and extraction of ions during the cycling process. Figure 13 The rate performance results of Case Studies 1-6 show that the capacity of the prepared nitrogen-doped hierarchical microporous carbon materials decreases slowly and steadily with increasing current density, maintaining a high capacity even at higher current densities, indicating that the material possesses rapid charge transport and sodium ion diffusion kinetics. Furthermore, when the current density returns to its initial state, the capacity quickly recovers to its initial value, demonstrating the material's structural stability and excellent electrochemical reversibility during repeated sodium insertion / extraction processes.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing nitrogen-doped hierarchical microporous carbon materials, characterized in that, Starting with bromine-containing halogenated aromatic hydrocarbons and alkynylbenzene compounds, a cross-coupling reaction was carried out under the combined action of palladium and copper catalysts, alkaline environment, polar solvent, and inert gas conditions to obtain alkynyl porphyrin conjugated microporous polymers. The obtained polymers were then subjected to high-temperature pyrolysis in an inert gas environment to gradually transform the material into nitrogen-doped porous carbon materials.

2. The method according to claim 1, characterized in that, The alkynylbenzene compounds are selected from 1,3,5-triethynylbenzene, hexaethynylbenzene, or 1,4-diethynylbenzene, and the bromine-containing haloaromatic hydrocarbons are selected from m-tetra(p-bromophenyl)porphyrin. The molar ratio of the bromine-containing haloaromatic hydrocarbons to the alkynylbenzene compounds is 1:1 to 10:

1.

3. The method according to claim 1, characterized in that, The polar solvent is selected from at least one of N,N-dimethylformamide, tetrahydrofuran, toluene, and pyridine, and the alkaline environment is provided by triethylamine.

4. The method according to claim 1, characterized in that, The palladium catalyst is selected from Pd(PPh3)4, Pd(PPh3)2Cl2 or Pd(dppf)Cl2, and the copper catalyst is selected from CuI, CuBr, CuCl or Cu(OTf)2. The molar ratio of the palladium catalyst to the copper catalyst is 1:0.5-1:

1.

5. The method according to claim 1, characterized in that, The cross-coupling reaction temperature is 80℃-100℃, and the stirring reaction time is 24 h-72 h.

6. The method according to claim 1, characterized in that, The inert gas mentioned in both places is selected from nitrogen, helium and argon.

7. The method according to claim 1, characterized in that, The high-temperature pyrolysis temperature is 300℃-800℃ (preferably 600-700℃), the pyrolysis time is 2-6 hours, and the pyrolysis heating rate is 5-10℃ / min.

8. The method according to claim 1, characterized in that, Specifically, the steps include the following: Step a: Dissolve m-tetra(p-bromophenyl)porphyrin and 1,3,5-triethynylbenzene in N,N-dimethylformamide and triethylamine. After purging with argon gas for 15 minutes, add Pd(PPh3)4 and CuI sequentially. Purge with argon gas again for 15 minutes. Seal the system and stir at 100°C for 72 hours. After the reaction, filter the solution. The resulting purple precipitate is washed three times each with methanol, dichloromethane, and anhydrous ethanol to obtain alkynylporphyrin conjugated microporous polymer powder. The reaction mixture consists of 0.3 mmol m-tetra(p-bromophenyl)porphyrin and 0.2 mmol 1,3,5-triethynylbenzene, 15 mL N,N-dimethylformamide, 15 mL triethylamine, 0.03 mmol Pd(PPh3)4, and 0.03 mmol CuI. Step b: The alkynyl porphyrin conjugated microporous polymer powder obtained in step a is placed in a tube furnace and pyrolyzed at different temperatures in an inert gas environment to gradually transform it into nitrogen-doped porous carbon material.

9. A nitrogen-doped hierarchical microporous carbon material prepared according to any one of claims 1-8.

10. The application of a nitrogen-doped multi-level microporous carbon material prepared according to any one of claims 1-8, for use as a negative electrode in a sodium-ion battery.

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