Aza-cyclic covalent organic framework material and preparation method and application thereof

Abstract

The application relates to the technical field of electrochemical materials, and discloses a nitrogen heterocyclic covalent organic framework material with a chemical formula of (C 42 H 18 N 12 ) n , wherein n is a positive integer greater than or equal to 4; a preparation method thereof comprises the following steps: S1: under an inert atmosphere, six nitrogen heterocyclic triphenylene-2,3,8,9,14,15-hexahalogen-substituted compounds, 2,3,6,7,10,11-hexaaminotriphenylhexa-hydrochloride, a deprotonation reagent, bis (1,5-cyclooctadiene) rhodium (I) tetrafluoroborate and 1,3-diisopropylimidazole chloride are added into an organic solvent in a molar ratio of 1:(1-1.5):(9-18):(0.02-0.12):(0.04-0.25), are uniformly mixed, are reacted at 50-150 DEG C for 1-7 days, are naturally cooled to room temperature, are filtered to collect precipitates, and a crude product is obtained; S2: the crude product in S1 is washed and dried to obtain the nitrogen heterocyclic covalent organic framework material; and the material is applied to lithium ion battery negative electrode materials and positive electrode materials. The scheme solves the problems of poor rate performance and limited application range of existing covalent organic framework materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical materials, in particular to a nitrogen heterocyclic covalent organic framework material and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in new energy vehicles, energy storage systems and various consumer electronic products due to their outstanding energy density advantages. For lithium ion batteries, electrode materials are the key elements that determine the energy density, power density and cycle life of the energy storage devices. The electrode materials used in traditional lithium ion batteries are mainly inorganic materials such as carbon materials or transition metal compounds. Among them, although carbon materials have certain characteristics, their actual capacity is low and they are difficult to meet the increasing demand for high performance; transition metal compounds are severely dependent on scarce natural resources, limiting their large-scale application and making the cost of batteries high. In view of the future more extensive application requirements of lithium ion batteries, it is urgent to develop electrode materials with high specific capacity and resource sustainability to promote the energy density and power density to a new height.

[0003] Covalent organic frameworks (COFs) emerge as the times require, which are crystalline organic polymers formed by covalent bonds between light elements such as C, H, N, O, B and S, which are widely available and abundant. The most remarkable feature of COFs is that they have regular hetero-element doping and unique porous structure. When used as electrode materials, they can provide ample active sites for lithium ion storage, have high specific capacity and excellent rate performance, and have great potential in the preparation of lithium ion batteries with high energy density and high power density.

[0004] The technical solution of patent No. CN112920405B discloses a thin-layer covalent organic framework material connected by irreversible bonds and its preparation method and application. The preparation process is as follows: 2,3,6,7,10,11-hexabromotriphenyl, 2,3,6,7,10,11-hexaaminotriphenyl hexahydrate, deprotonation reagent, bis(1,5-cyclooctadiene) rhodium (I) tetrafluoroborate and N,N'-(isopropyl) imidazole chloride are weighed according to the molar ratio of 1:(1-2):(7-14):(0.01-0.1):(0.02-0.2) and then added to an organic solvent, mixed and reacted at 80-160℃ for 3-15 days, then solid-liquid separation is performed, and the target material is obtained by washing and drying the solid phase. All atoms in the prepared thin-layer covalent organic framework material are connected by irreversible piperazine rings, and the material is in the form of crystalline thin-layer COFs nanosheets formed by ordered stacking of single-layer COFs. The material has excellent chemical stability, good electrochemical lithium storage capacity and excellent cycle stability, providing a new direction for the development of lithium ion battery negative materials.

[0005] However, the material has obvious shortcomings. On the one hand, the rate performance is poor, and in some scenarios with extremely high power requirements, the problem is particularly prominent. For example, in the rapid acceleration of electric vehicles, the energy recovery of sudden braking, or the emergency power supply application of some industrial equipment requiring instant high-power output, due to the poor rate performance, the material cannot be quickly and efficiently charged and discharged, making it difficult to meet the demand for instant high-current supply, resulting in limited device operation efficiency, and even possible power shortage; on the other hand, the material can only be applied to the negative electrode of lithium-ion batteries at the present stage, which greatly restricts its application scope and makes it difficult to play a role in a wider battery-related field. SUMMARY

[0006] The present application aims to provide a nitrogen heterocyclic covalent organic framework material and its preparation method and application, in order to solve the problems of poor rate performance and limited application range of existing covalent organic framework materials.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a nitrogen heterocyclic covalent organic framework material, the structural formula of the nitrogen heterocyclic covalent organic framework is:

[0008]

[0009] In the formula, n is a positive integer greater than or equal to 4.

[0010] The present application also provides another technical scheme, a preparation method of a nitrogen heterocyclic covalent organic framework material, comprising the following steps:

[0011] S1: under an inert atmosphere, hexaazatriphenylene-2,3,8,9,14,15-hexahalogen-substituted compound, 2,3,6,7,10,11-hexaaminotriphenylhexa-hydrochloride, deprotonation reagent, bis(1,5-cyclooctadiene) rhodium (I) tetrafluoroborate and 1,3-diisopropylimidazole chloride are added to an organic solvent in a molar ratio of 1:(1-1.5):(9-18):(0.02-0.12):(0.04-0.25), mixed uniformly, reacted at 50-150℃ for 1-7 days, naturally cooled to room temperature, and then the precipitate was collected by filtration to obtain a crude product;

[0012] S2: the crude product in S1 is washed and dried to obtain a nitrogen heterocyclic covalent organic framework material.

[0013] Preferably, in S1, the structural formula of the hexaazatriphenylene-2,3,8,9,14,15-hexahalogen-substituted compound is:

[0014]

[0015] In the formula, X is any one of Br, Cl and F.

[0016] Preferably, in S1, the deprotonating agent is any one of an organic strong base and an inorganic base.

[0017] Preferably, the organic strong base is any one of lithium tert-butoxide, sodium tert-butoxide and potassium tert-butoxide; and the inorganic base is any one of sodium carbonate, potassium carbonate and cesium carbonate.

[0018] Preferably, in S1, the inert atmosphere is any one of nitrogen and argon.

[0019] Preferably, in S1, the organic solvent is any one of ethylene glycol dimethyl ether, dimethyl sulfoxide, N-methyl pyrrolidone and toluene.

[0020] Preferably, the washing process in S2 is: firstly, the crude product in S1 is subjected to preliminary washing by using N,N-dimethylformamide, deionized water and tetrahydrofuran in sequence; and then, the wet product without drying is subjected to deep washing by using Soxhlet extraction method, and tetrahydrofuran and methanol are used as the extraction solvents in sequence.

[0021] Preferably, in S2, the drying temperature is 100-120℃, and the drying time is 24-48h.

[0022] The application further provides another technical solution, i.e., an application of the nitrogen heterocyclic covalent organic framework material in lithium ion battery negative electrode materials and positive electrode materials.

[0023] The nitrogen heterocyclic covalent organic framework material provided by the technical solution is prepared through Buchwald-Hartwig arylamine reaction, and irreversible C-NH-C nitrogen heterocyclic rings and a large number of high-activity C=N are introduced, and the triphenylene group and the hexaazatriphenylene group are connected through the irreversible C-NH-C nitrogen heterocyclic rings, and the following advantages are achieved.

[0024] (1) The nitrogen heterocyclic covalent organic framework material provided by the technical solution innovatively introduces a large number of C=N and benzene ring structures, and these structures serve as active sites of lithium ions, greatly improve the density of redox active sites, and thus lay a solid foundation for significant improvement of battery theoretical capacity. Experimental results show that the specific capacity can reach 938 mAh / g after 100 cycles at a current density of 0.1 A / g.

[0025] (2) In the nitrogen heterocyclic covalent organic framework material provided by the technical solution, the introduction of the triphenylene group and the hexaazatriphenylene group greatly increases the proportion of conjugated aromatic structures, improves the rate performance of the material, and enables the material to maintain good charge and discharge efficiency even at a large current density of 5 A / g. Moreover, the material can quickly restore high specific capacity when the current density is restored to a low value.

[0026] (3) The nitrogen heterocyclic covalent organic framework material provided by the technical scheme has excellent resistance in strong acid, strong base and organic solvent, ensures the long-term use reliability of the material in harsh environment, and reduces the performance loss caused by material dissolution or degradation.

[0027] (4) The nitrogen heterocyclic covalent organic framework material provided by the technical scheme breaks through the application limitation of the prior art only in the negative electrode, and can be used as both a negative electrode material and a positive electrode material of a lithium ion battery, greatly widening the application field thereof, which has important significance for developing new high-performance energy storage devices.

[0028] (5) The nitrogen heterocyclic covalent organic framework material is constructed by using light elements which are widely available and abundant, thereby reducing the dependence on scarce natural resources, meeting the concept of green chemistry, and being conducive to promoting the development of lithium ion batteries in a more environmentally friendly direction. The synthesis process of the material utilizes the Buchwald-Hartwig aryl amination reaction, ensures efficient and controllable formation of C-NH-C bonds, realizes effective utilization of resources and environment-friendly manufacturing process.

[0029] (6) The technical scheme optimizes the washing process to ensure the purity and performance of the material: pre-washing with N,N-dimethylformamide can effectively wash away unreacted raw materials, residual catalysts and small molecular products generated after the reaction, lay a foundation for subsequent washing steps, and reduce the potential influence of impurities on the performance of the material; pre-washing with deionized water can specifically wash away the inorganic salt NaBr generated during the reaction, avoid the influence of residual inorganic salt on the electrochemical performance of the material, and ensure the chemical purity of the material; pre-washing with tetrahydrofuran can wash away the high-boiling point solvents (DMF and H2O) used in the previous washing steps, and further remove the small molecular products remaining after the reaction, thereby further improving the purity of the material. Deep washing is performed by using Soxhlet extraction method, and tetrahydrofuran is used for the second time for Soxhlet extraction washing, which can ensure that the impurities that are difficult to remove are thoroughly washed. Subsequently, washing with methanol realizes the replacement of solvent molecules in the pores, facilitates subsequent drying treatment, ensures the integrity and purity of the internal structure of the material, and further ensures the performance stability of the material in application.

[0030] In summary, the present application overcomes the problems in the prior art by innovative structural design, irreversible C-NH-C azacycle connection of triphenylene groups and hexaazatriphenylene groups, combined with efficient synthesis methods such as Buchwald-Hartwig aryl amination reaction, and optimized washing process. The prepared azacycle covalent organic framework material has excellent performance in electrochemical performance, stability, rate characteristics and environmental sustainability, and the purity and performance of the material are ensured through fine washing. The material is suitable for positive and negative electrode materials of high-performance lithium ion batteries, and injects new vitality into the development of lithium ion battery field, and is expected to occupy an important position in future energy storage systems, and provide an innovative technical solution for solving global energy storage problems. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A schematic diagram of the molecular structure of the azacycle covalent organic framework material prepared in Example 1 of the present application;

[0032] Figure 2 The SEM image of the azacycle covalent organic framework material prepared in Example 1 of the present application;

[0033] Figure 3 The infrared spectrum of the azacycle covalent organic framework material prepared in Example 1 of the present application;

[0034] Figure 4 The XRD graph of the azacycle covalent organic framework material prepared in Example 1 of the present application;

[0035] Figure 5 The solid-state nuclear magnetic carbon spectrum of the azacycle covalent organic framework material prepared in Example 1 of the present application;

[0036] Figure 6 The infrared spectrum of the azacycle covalent organic framework material prepared in Example 1 of the present application after being soaked in 12 moL / L sodium hydroxide solution, 12 moL / L hydrochloric acid solution, diethyl carbonate, acetonitrile, dichloromethane for 7 days respectively;

[0037] Figure 7 The cycle performance graph of the button cell assembled by the azacycle covalent organic framework material prepared in Example 1 of the present application under the condition of current density of 0.1 A / g;

[0038] Figure 8 The cyclic voltammetry curve of the button cell assembled by the azacycle covalent organic framework material prepared in Example 1 of the present application as the negative electrode after activation;

[0039] Figure 9 The rate performance graph of the button cell assembled by the azacycle covalent organic framework material prepared in Example 1 of the present application after activation;

[0040] Figure 10 The long cycle performance graph of the button cell assembled by the nitrogen heterocyclic covalent organic framework material prepared in Example 1 of the present application at a current density of 5 A / g;

[0041] Figure 11 The cyclic voltammogram of the button cell assembled by the nitrogen heterocyclic covalent organic framework material prepared in Example 1 of the present application as a positive electrode at different scanning rates;

[0042] Figure 12 The rate performance graph of the button cell assembled by the irreversible bond connected thin-layer covalent organic framework material prepared in Comparative Example 1 of the present application after activation. DETAILED DESCRIPTION

[0043] The following is further described in detail through specific embodiments:

[0044] Example 1

[0045] A nitrogen heterocyclic covalent organic framework material, the structural formula of the nitrogen heterocyclic covalent organic framework is:

[0046]

[0047] In the formula, n is a positive integer greater than or equal to 4.

[0048] A preparation method of a nitrogen heterocyclic covalent organic framework material, comprising the following steps:

[0049] S1: under an inert atmosphere, hexaazatriphenylene-2,3,8,9,14,15-hexahalogen substituent, 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride, deprotonation reagent, bis(1,5-cyclooctadiene) rhodium (I) tetrafluoroborate and 1,3-diisopropylimidazole chloride are added into an organic solvent in a molar ratio of 1:(1-1.5):(9-18):(0.02-0.12):(0.04-0.25), mixed uniformly, reacted at 50-150℃ for 1-7 days, naturally cooled to room temperature, and then the precipitate was collected by filtration to obtain a crude product;

[0050] Among them, the hexaazatriphenylene-2,3,8,9,14,15-hexahalogen substituent is any one of 2,3,8,9,14,15-hexabromohexaazatriphenylene, 2,3,8,9,14,15-hexachlorohexaazatriphenylene and 2,3,8,9,14,15-hexafluorohexaazatriphenylene;

[0051] The structural formula of the hexaazatriphenylene-2,3,8,9,14,15-hexahalogen substituent is:

[0052]

[0053] X is any one of Br, Cl and F;

[0054] The structural formula of 2,3,6,7,10,11-hexaaminotriphenylenium hexachloride is as follows:

[0055]

[0056] The deprotonating agent is any one of an organic strong base and an inorganic base; the organic strong base is any one of lithium tert-butoxide, sodium tert-butoxide and potassium tert-butoxide; the inorganic base is any one of sodium carbonate, potassium carbonate and cesium carbonate;

[0057] The organic solvent is any one of ethylene glycol dimethyl ether, dimethyl sulfoxide, N-methyl pyrrolidone and toluene;

[0058] The inert gas is any one of nitrogen and argon;

[0059] In this embodiment, in a glove box in an argon atmosphere, 2,3,8,9,14,15-hexabromohexaazatriphenylene (abbreviated as HATN-Br6), 2,3,6,7,10,11-hexaaminotriphenylenium hexachloride (abbreviated as HATP-6HCl), sodium tert-butoxide, bis(1,5-cyclooctadiene)rhodium(I) tetrafluoroborate and 1,3-diisopropylimidazole chloride are added into a thick-walled pressure-resistant reaction tube containing ethylene glycol dimethyl ether in a molar ratio of 1:1:15:0.05:0.1, wherein the amount of ethylene glycol dimethyl ether is 8 mL, then a sealing operation is performed, and the reaction tube is removed from the glove box, ultrasonic dispersion is performed for 30 min, and then the reaction tube is placed in an oven at 120℃, and reaction is performed for 3 days; after the reaction system is naturally cooled to room temperature, the precipitate is collected by filtration to obtain a crude product.

[0060] S2: The crude product in S1 is washed and vacuum dried to obtain a nitrogen heterocyclic covalent organic framework material; the washing process is as follows: the crude product in S1 is first subjected to preliminary washing with N,N-dimethylformamide, deionized water and tetrahydrofuran in sequence, after the preliminary washing, the wet product without drying is subjected to deep washing by Soxhlet extraction, and tetrahydrofuran and methanol are used as extraction solvents in sequence for deep washing; the washed product is placed in a vacuum drying box and dried at 100-120℃ for 24-48 h to obtain a red-brown solid product PIPHATN COF, i.e., a nitrogen heterocyclic covalent organic framework material. In this embodiment, the drying temperature is 120℃, and the drying time is 24 h.

[0061] The application of a nitrogen heterocyclic covalent organic framework material to lithium ion battery negative electrode materials and positive electrode materials.

[0062] Figure 1A schematic diagram of the molecular structure of the nitrogen heterocyclic covalent organic framework material prepared in Example 1 is shown in FIG. 1. Figure 1 It can be seen that the nitrogen heterocyclic covalent organic framework material is a two-dimensional COF material obtained by connecting triphenylene and hexaazatriphenylene through C-NH-C nitrogen heterocycles and expanding in the two-dimensional direction.

[0063] The nitrogen heterocyclic covalent organic framework material prepared in Example 1 was observed by scanning electron microscopy, and the results are shown in FIG. 2. Figure 2 As shown in FIG. 2, the nitrogen heterocyclic covalent organic framework material is a strip-shaped structure stacked by small pieces, which is beneficial to the rapid transmission of lithium ions and improves the rate performance.

[0064] The nitrogen heterocyclic covalent organic framework material prepared in Example 1 was detected and analyzed by infrared spectroscopy, and the results are shown in FIG. 3. Figure 3 It can be seen from FIG. 3 that there is no C-Br peak near 600 cm-1 in the nitrogen heterocyclic covalent organic framework material (PIPHATN COF), and in-plane bending vibration mode and out-of-plane bending vibration mode of N-H bond in piperazine linker are shown at 1514 cm-1 and 838 cm-1, respectively; the stretching vibration mode of N-H bond is shown at 3332 cm-1, and the asymmetric stretching vibration mode of C-N bond in piperazine bond is shown at 1089 cm-1, which fully proves the conversion from reactants to products. -1 -1 -1 -1 -1

[0065] The nitrogen heterocyclic covalent organic framework material prepared in Example 1 was detected and analyzed by X-ray diffraction, and the results are shown in FIG. 4. Figure 4 It can be seen from FIG. 4 that the nitrogen heterocyclic covalent organic framework material shows diffraction peaks at 8.9°, 24.5° and 42°, respectively, corresponding to the (100), (001) and (110) crystal planes of two-dimensional stacking, which proves that the nitrogen heterocyclic covalent organic framework material is successfully synthesized.

[0066] The nitrogen heterocyclic covalent organic framework material prepared in Example 1 was detected and analyzed by solid-state nuclear magnetic carbon spectrum, and the results are shown in FIG. 5. Figure 5 It can be seen from FIG. 5 that different kinds of carbon connected triphenylene and hexaazatriphenylene through C-NH-C appear chemical shifts, which proves that the nitrogen heterocyclic covalent organic framework material is successfully synthesized.

[0067] The nitrogen heterocyclic covalent organic framework material prepared in Example 1 was soaked in 12 moL / L sodium hydroxide solution, 12 moL / L hydrochloric acid solution, diethyl carbonate, acetonitrile and dichloromethane for 7 days, respectively, then filtered and washed with water and methanol, vacuum dried at 120℃, and then analyzed by infrared spectroscopy. As shown in FIG. 6. Figure 6 ​​​​​It can be seen that the infrared spectrum does not change, indicating that the internal C=N and C-NH-C still exist, and indicating that it has good stability in strong acid, strong base and organic solvent.

[0068] The nitrogen heterocyclic covalent organic framework material prepared in Example 1 was kept at 450℃ for 2h under nitrogen atmosphere to remove residual impurity molecules in the pores, and then assembled into a button cell, and its performance was tested. The assembly process was as follows: the nitrogen heterocyclic covalent organic framework material prepared in Example 1, conductive carbon black and PVDF binder were mixed in a weight ratio of 6:3:1 in an N-methyl pyrrolidone solution to form a uniform slurry, which was then coated on a copper foil to form a working electrode; lithium metal sheet was used as a counter electrode, and 1moL / L lithium hexafluorophosphate ethylene carbonate / dimethyl carbonate / methyl ethyl carbonate (volume ratio 1:1:1) + 1% vinylene carbonate solution was used as an electrolyte to assemble a button cell. After standing for 12 hours, the performance of the button cell was tested, and the test voltage range was 0.01-3V (V vs Li / Li + ).

[0069] The button cell assembled from the nitrogen heterocyclic covalent organic framework material prepared in Example 1 was activated at a current density of 0.1A / g, and the cycle performance graph was measured. Figure 7 It can be seen that at a current density of 0.1A / g, the specific capacity shows an upward trend in the early stage. After 100 cycles, the specific capacity is increased to 938mAh / g. The gradual increase in specific capacity indicates that the electrode needs an activation process before achieving its maximum specific capacity.

[0070] The button cell assembled from the nitrogen heterocyclic covalent organic framework material prepared in Example 1 was subjected to cyclic voltammetry test at different scanning rates. Figure 8 It can be seen that the cyclic voltammogram has a pair of redox peaks near 1V, which is attributed to the C=N group in the structure, indicating that C=N as an active site participates in the storage of lithium ions.

[0071] The button cell assembled from the nitrogen heterocyclic covalent organic framework material prepared in Example 1 was subjected to rate performance test at different current densities. Figure 9It can be seen that the GCD test under different current densities is carried out to test the specific capacity of the PIPHATN COF electrode, and then the rate performance and cycle stability are measured. When the current density is 0.1A / g, 0.2A / g, 0.5A / g, 1A / g, 2A / g, 5A / g, the electrode respectively shows 710, 644, 545, 464, 378, 275mAh / g of reversible specific capacity; with the test, when the current density is restored from the large current density of 5A / g to the small current density of 0.1A / g, the specific capacity of the COF electrode can quickly recover to the high specific capacity of 788mAh / g, indicating that it has good reversibility.

[0072] The button cell assembled by the nitrogen heterocyclic covalent organic framework material prepared in Example 1 is subjected to a large current cycle test of 5A / g. From the test data, it can be seen that the button cell has a high capacity retention rate of 70% after 1000 cycles, indicating that it has good cycle stability. Figure 10 It can be seen that after 2600 cycles, there is still a high capacity retention rate, indicating that it has good cycle stability.

[0073] The button cell prepared by taking the nitrogen heterocyclic covalent organic framework material prepared in Example 1 as the positive electrode is assembled by: taking the nitrogen heterocyclic covalent organic framework material, conductive carbon black and PVDF binder prepared in Example 1, according to the weight ratio of 6:3:1, adding them into N-methyl pyrrolidone solution to mix thoroughly, making uniform slurry, and coating on copper foil to make positive electrode; lithium metal sheet as negative electrode, 1moL / L lithium hexafluorophosphate ethylene carbonate / dimethyl carbonate / methyl ethyl carbonate (volume ratio 1:1:1) + 1% vinylene carbonate solution as electrolyte to assemble button cell, and after standing for 12 hours, the performance is tested, the test voltage range is 1-4V, and it can withstand 4V voltage, which can be used as positive electrode of lithium ion battery, indicating that it can be used as excellent lithium battery positive electrode material.

[0074] Comparative Example 1

[0075] The irreversible bond connected thin layer covalent organic framework material disclosed in the technical solution of patent No. CN112920405B is taken as a comparison.

[0076] The irreversible bond connected thin layer covalent organic framework material obtained from the patent is assembled into a button cell, and its rate performance is detected. The experimental data show that under the condition that the current density is set to be 0.1A / g, 0.2A / g, 0.5A / g, 1A / g, 2A / g, 5A / g in turn, the material respectively presents specific capacity of 1696, 1511, 1159, 851, 579, 329mAh / g (especially noted that the above experimental data are directly from patent CN112920405B).

[0077] By comparison Figure 9 and Figure 12It can be seen that the rate performance of the nitrogen heterocyclic covalent organic framework material is obviously better than that of the thin-layer covalent organic framework material connected by irreversible bonds.

[0078] Further exploration of the application scope of both can know that the nitrogen heterocyclic covalent organic framework material has unique advantages, which can not only adapt to the positive material of lithium ion battery, but also meet the demand of negative material; In sharp contrast, the thin-layer covalent organic framework material connected by irreversible bonds can only be limited to the application field of negative material of lithium ion battery, and the application range is relatively narrow.

[0079] The above is only an embodiment of the present application, and the specific technical solutions and / or common knowledge of the scheme are not described in detail. It should be pointed out that for those skilled in the art, without departing from the technical scheme of the present application, a number of modifications and improvements can be made, which should also be regarded as the protection scope of the present application, which will not affect the effect and practicality of the present application. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. An azacyclic covalent organic framework material, characterized by: The structural formula of the azacyclic covalent organic framework is: In the formula, n is a positive integer greater than or equal to 4.

2. A method of preparing a nitrogen heterocycle covalent organic framework material, characterized by: The method comprises the following steps: S1: under an inert atmosphere, a hexaazatriphenylene-2,3,8,9,14,15-hexahalogen-substituted compound, 2,3,6,7,10,11-hexaaminotriphenylhexa-hydrochloride, a deprotonating agent, bis(1,5-cyclooctadiene)rhodium(I) tetrafluoroborate and 1,3-diisopropylimidazole chloride are added into an organic solvent in a molar ratio of 1:(1-1.5):(9-18):(0.02-0.12):(0.04-0.25), and are uniformly mixed, and then are reacted at 50-150 DEG C for 1-7 days, and then are naturally cooled to room temperature, and then are filtered to collect a precipitate, thereby obtaining a crude product; S2: the crude product in S1 is washed and dried to obtain an azacyclic covalent organic framework material.

3. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 2, characterized in that: In S1, the structural formula of the hexaazatriphenylene-2,3,8,9,14,15-hexahalogen-substituted compound is: In the formula, X is any one of Br, Cl and F.

4. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 3, characterized in that: In S1, the deprotonating agent is any one of an organic strong base and an inorganic base.

5. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 4, characterized in that: The organic strong base is any one of lithium tert-butoxide, sodium tert-butoxide and potassium tert-butoxide; and the inorganic base is any one of sodium carbonate, potassium carbonate and cesium carbonate.

6. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 5, characterized in that: In S1, the inert atmosphere is any one of nitrogen and argon.

7. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 6, characterized in that: In S1, the organic solvent is any one of ethylene glycol dimethyl ether, dimethyl sulfoxide, N-methyl pyrrolidone and toluene.

8. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 7, characterized in that: In S2, the washing process is as follows: the crude product in S1 is first subjected to preliminary washing with N,N-dimethylformamide, deionized water and tetrahydrofuran in sequence, and then is subjected to deep washing by Soxhlet extraction, and tetrahydrofuran and methanol are used as extraction solvents in sequence.

9. The method for preparing a nitrogen heterocyclic covalent organic framework material according to claim 8, characterized in that: In S2, the drying temperature is 100-120 DEG C, and the drying time is 24-48 h.

10. Use of the nitrogen heterocycle covalent organic framework material according to claim 1, characterized in that: The azacyclic covalent organic framework material is applied to lithium ion battery negative electrode materials and positive electrode materials.

Images