Synthesis method of hydrogen storage material N-ethyl carbazole

Abstract

The invention provides a synthesis method of a hydrogen storage material N-ethyl carbazole, and the synthesis method of the hydrogen storage material N-ethyl carbazole comprises the following steps: step 1, preparing an intermediate tetrahydrocarbazole; step 2, preparing a liquid product, and step 3, sequentially adding 53-76.5 parts of the liquid product prepared in the step 2, 213-320 parts of a solvent o-dichlorobenzene and 0.8-1.2 parts of 5% platinum / carbon into a three-neck flask provided with a reflux condenser, heating to reflux, and keeping the temperature for 1 hour; reacting, cooling to 80 DEG C, filtering, adding 26.5-40 parts of a hot solvent to wash the catalyst, and carrying out reduced pressure distillation to recover the solvent, so as to obtain a product N-ethyl carbazole; 4, adding 3-6 parts of N-ethyl carbazole prepared in the step 3, a proper amount of a solvent and 1-2 parts of an organic framework material into a reaction kettle, reacting for 8-12 hours at 120 DEG C by adopting a solvothermal method, cooling to room temperature after the reaction is completed, filtering, washing and drying to obtain a product hydrogen storage N-ethyl carbazole; a Fisher carbazole synthesis method is adopted, phenylhydrazine and cyclohexanone are used as raw materials, 1, 2, 3, 4-tetrahydrocarbazole is obtained through condensation and closed loop, an N-tetrahydrocarbazole intermediate is obtained through ethylation reaction, and the high-purity hydrogen storage material N-ethyl carbazole is obtained through dehydrogenation.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, in particular to a method for synthesizing hydrogen storage material N-ethylcarbazole. Background Art

[0002] Hydrogen energy is a secondary energy source with abundant sources, green and low carbon, and wide application. The development of hydrogen energy is of great significance to building a clean, low-carbon, safe and efficient energy system and achieving the goals of carbon peak and carbon neutrality. However, the safe and efficient storage and transportation of hydrogen restrict the development of hydrogen energy. Hydrogen storage is one of the core technologies in the hydrogen energy industry. Liquid organic hydrogen carriers (LOHC) and solid metal hydrides are two important types of chemical hydrogen storage carriers. LOHC has the advantages of high hydrogen storage density, good cyclicity, convenient thermal management, and high compatibility with oil and gas facilities. It is particularly valued in the field of long-distance hydrogen storage and transportation, and is also expected to be used in vehicle-mounted hydrogen storage. Among them, N-ethylcarbazole (NEC) has become one of the most promising LOHCs due to its high capacity, suitable operating temperature, low volatility, and low toxicity.

[0003] At present, N-ethylcarbazole is mainly prepared by ethylation of carbazole, but the content of N-ethylcarbazole synthesized by this method is low and is only used in the dye and pigment industry, which cannot meet the requirements of hydrogen storage materials. A synthetic process route for high-purity N-ethylcarbazole is designed to improve the hydrogen storage capacity and be suitable for industrial production. Summary of the invention

[0004] The present invention provides a method for synthesizing hydrogen storage material N-ethylcarbazole, aiming to solve the problems raised by the above background technology.

[0005] The present invention is achieved by a method for synthesizing a hydrogen storage material N-ethylcarbazole, comprising the following steps: Step 1: preparing the intermediate tetrahydrocarbazole, adding 8-12 parts of phenylhydrazine hydrochloride and 32-48 parts of water into a three-necked flask, stirring at room temperature until dissolved; then adding 3.4-3.6 parts of 30% hydrochloric acid, heating to 70°C and adding dropwise 5.6-1.4 parts of cyclohexanone; continuing to keep warm for 2 hours, cooling and filtering, washing with water, and drying to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 68.4-102.6 parts of the intermediate tetrahydrocarbazole prepared in step 1, 160-240 parts of sodium hydroxide aqueous solution, 66.8-171.1 parts of benzene and 0.8-1.2 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 78-117 parts of ethyl chloride, slowly heat to 105° C., pressure of 0.25 MPa, keep warm for 6 hours, and cool to room temperature; separate the alkali layer, neutralize with 30% hydrochloric acid, wash to neutrality, and distill to recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 53-76.5 parts of the liquid product obtained in step 2, 213-320 parts of solvent o-dichlorobenzene, and 0.8-1.2 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 26.5-40 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 3-6 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 1-2 parts of organic framework materials into the reaction kettle, and react at 120°C for 8-12 hours by solvent thermal method. After the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole. Preferably, step 1: prepare the intermediate tetrahydrocarbazole, add 8 parts of phenylhydrazine hydrochloride and 32 parts of water into a three-necked flask, stir at room temperature until dissolved; then add 3.4 parts of 30% hydrochloric acid, raise the temperature to 70°C and dropwise add 5.6 parts of cyclohexanone; continue to keep warm for 2 hours, cool and filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 68.4 parts of the intermediate tetrahydrocarbazole prepared in step 1, 160 parts of sodium hydroxide aqueous solution, 66.8 parts of benzene and 0.8 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 78 parts of ethyl chloride, slowly heat to 105°C, the pressure is 0.25MPa, keep warm for 6 hours, and cool to room temperature; separate the alkali layer, neutralize it in 30% hydrochloric acid, wash it to neutrality, and distill and recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 53 parts of the liquid product obtained in step 2, 213 parts of solvent o-dichlorobenzene, and 0.8 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 26.5 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 3 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 1 part of organic framework material into the reaction kettle, use the solvent thermal method, react at 120°C for 8-12 hours, and after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

[0006] Preferably, step 1: prepare the intermediate tetrahydrocarbazole, add 12 parts of phenylhydrazine hydrochloride and 48 parts of water into a three-necked flask, stir at room temperature until dissolved; then add 3.6 parts of 30% hydrochloric acid, raise the temperature to 70°C and dropwise add 1.4 parts of cyclohexanone; continue to keep warm for 2 hours, cool and filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 102.6 parts of the intermediate tetrahydrocarbazole prepared in step 1, 240 parts of sodium hydroxide aqueous solution, 171.1 parts of benzene and 1.2 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 117 parts of ethyl chloride, slowly heat to 105°C, the pressure is 0.25MPa, keep the temperature for 6 hours, and cool to room temperature; separate the alkali layer, neutralize it in 30% hydrochloric acid, wash it to neutrality, and distill and recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 76.5 parts of the liquid product obtained in step 2, 320 parts of solvent o-dichlorobenzene, and 1.2 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 40 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 6 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 2 parts of organic framework materials into the reaction kettle, use the solvent thermal method, react at 120°C for 8-12 hours, and after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

[0007] Preferably, the organic framework materials are UiO-66 and ZIF-8.

[0008] Preferably, in step 4, the solution is continuously stirred during the reaction in the reactor.

[0009] Due to the adoption of the above scheme, the beneficial effects of the present invention are as follows: the present application adopts water to synthesize tetrahydrocarbazole, uses ethyl chloride as raw material, and synthesizes N-ethyltetrahydrocarbazole by ethylation, adopts Fisher carbazole synthesis method, uses phenylhydrazine and cyclohexanone as raw materials, condenses and closes the ring to obtain 1,2,3,4-tetrahydrocarbazole, obtains N-tetrahydrocarbazole intermediate by ethylation reaction, and then dehydrogenates to obtain high-purity hydrogen storage material N-ethylcarbazole; in the present application, a hydrogen storage material synthesis method of metal organic framework materials such as UiO-66 and ZIF-8 and N-based carbazole composite materials is adopted, and a composite material of top structure and N-subsequent carbazole is formed by introducing metal organic framework materials (such as UiO-66 and ZIF-8) into the synthesis process. This composite material can significantly increase the hydrogen storage capacity, and the high specific interaction and microporous structure of MOFs provide a large number of adsorption sites for aqueous solution, so that the product can store more aqueous solution.

[0010] After the metal organic framework material is combined with N-o-carbazole, the adsorption and release performance of aqueous solution can be optimized. The pores and surface chemical properties of MOFs materials provide weak reaction to aqueous solution, effectively reducing the desorption temperature of aqueous solution during hydrogen storage, thus achieving extremely controllable water absorption and efficient release. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0012] A method for synthesizing hydrogen storage material N-ethylcarbazole comprises the following steps: Step 1: preparing the intermediate tetrahydrocarbazole, adding 8-12 parts of phenylhydrazine hydrochloride and 32-48 parts of water into a three-necked flask, stirring at room temperature until dissolved; then adding 3.4-3.6 parts of 30% hydrochloric acid, heating to 70°C and adding dropwise 5.6-1.4 parts of cyclohexanone; continuing to keep warm for 2 hours, cooling and filtering, washing with water, and drying to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 68.4-102.6 parts of the intermediate tetrahydrocarbazole prepared in step 1, 160-240 parts of sodium hydroxide aqueous solution, 66.8-171.1 parts of benzene and 0.8-1.2 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 78-117 parts of ethyl chloride, slowly heat to 105° C., pressure of 0.25 MPa, keep warm for 6 hours, and cool to room temperature; separate the alkali layer, neutralize with 30% hydrochloric acid, wash to neutrality, and distill to recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 53-76.5 parts of the liquid product obtained in step 2, 213-320 parts of solvent o-dichlorobenzene, and 0.8-1.2 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 26.5-40 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 3-6 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 1-2 parts of organic framework materials into a reaction kettle, use a solvent thermal method, react at 120°C for 8-12 hours, and after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

[0013] Example 1 Add 104g of phenylhydrazine hydrochloride and 400g of water into a 1000ml three-necked flask, stir at room temperature until dissolved, add 30g of 30% hydrochloric acid, raise the temperature to 70℃, add 70g of cyclohexanone dropwise, and continue to add for about 1 hour. Keep warm for 2 hours, cool and filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole.

[0014] In a 2000ml autoclave, add 171g (1.0mol) 99% tetrahydrocarbazole, 400g 40% sodium hydroxide aqueous solution, 167g benzene and 2g triethylbenzylammonium bromide in sequence, and close the autoclave. After nitrogen replacement three times, add 97g (1.5mol) ethyl chloride, slowly heat to 105℃, pressure 0.25MPa, keep warm for 6h, and cool to room temperature. Remove the alkali layer, neutralize with 30% hydrochloric acid, wash to neutrality, distill and recover benzene, and obtain 195g of liquid product with a yield of 98% and a GC purity of 98.5%.

[0015] In a 2000ml three-necked flask equipped with a reflux condenser, add 199g (1mol) of N-tetrahydrocarbazole, 800g of solvent o-dichlorobenzene, and 3.0g of 5% platinum / carbon in sequence, heat to reflux, and keep warm for 11 hours. The reaction solution is cooled to 80°C, filtered, the catalyst is washed with 100ml of hot solvent, and the solvent is recovered by vacuum distillation to obtain 193.8g of N-ethylcarbazole, with a yield of 98% and a GC chromatographic purity of 99.3%.

[0016] In a 2000 ml reactor, add 450 g of N-ethylcarbazole prepared in step 3, 500 ml of o-dichlorobenzene, 100 g of UiO-66 and 100 g of ZIF-8. After sufficient stirring, react at 120 ° C for 8-12 hours using a solvent thermal method. After the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

[0017] Example 2 Add 85g of phenylhydrazine hydrochloride and 320g of water into a 1000ml three-necked flask, stir at room temperature until dissolved, add 24g of 30% hydrochloric acid, raise the temperature to 70℃, add 56g of cyclohexanone dropwise, and add it after about 1h. Keep warm for 2 hours, cool and filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole.

[0018] In a 2000ml autoclave, add 171g of 99% tetrahydrocarbazole, 400g of 40% sodium hydroxide aqueous solution, 167g of benzene and 2g of triethylbenzylammonium bromide in sequence, and close the autoclave. After nitrogen replacement three times, add 97g of ethyl chloride, slowly heat to 105℃, pressure 0.25MPa, keep warm for 6h, and cool to room temperature. Remove the alkali layer, neutralize with 30% hydrochloric acid, wash to neutrality, distill and recover benzene, and obtain 195g of liquid product with a yield of 97.8% and a GC purity of 98.5%.

[0019] In a 2000ml three-necked flask equipped with a reflux condenser, 160g of N-tetrahydrocarbazole, 640g of solvent o-dichlorobenzene, and 2.4g of 5% platinum / carbon were added in sequence, the temperature was raised to reflux, and the reaction was kept warm for 11 hours. The reaction solution was cooled to 80°C, filtered, the catalyst was washed with 800ml of hot solvent, and the solvent was recovered by vacuum distillation to obtain 150.1g of N-ethylcarbazole, with a yield of 93.8% and a GC chromatographic purity of 97.3%.

[0020] In a 2000 ml reactor, add 300 g of N-ethylcarbazole prepared in step 3, 350 ml of o-dichlorobenzene, 67 g of UiO-66 and 67 g of ZIF-8. After sufficient stirring, react at 120 ° C for 8-12 hours using a solvent thermal method. After the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

[0021] Example 3 Add 124g of phenylhydrazine hydrochloride and 480g of water into a 1000ml three-necked flask, stir at room temperature until dissolved, add 36g of 30% hydrochloric acid, raise the temperature to 70℃, add 85g of cyclohexanone dropwise, and add it in about 1h. Keep warm for 2 hours, cool and filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole.

[0022] In a 2000ml autoclave, add 205g of 99% tetrahydrocarbazole, 480g of 40% sodium hydroxide aqueous solution, 200g of benzene and 2.4g of triethylbenzylammonium bromide in sequence, and close the autoclave. After nitrogen replacement three times, add 115g of ethyl chloride, slowly heat to 105℃, pressure 0.25MPa, keep warm for 6h, and cool to room temperature. Remove the alkali layer, neutralize with 30% hydrochloric acid, wash to neutrality, distill and recover benzene, and obtain 235g of liquid product with a yield of 97.7% and a GC purity of 97.5%.

[0023] In a 2000ml three-necked flask equipped with a reflux condenser, add 240g N-tetrahydrocarbazole, 100g solvent o-dichlorobenzene, and 4g 5% platinum / carbon in sequence, heat to reflux, and keep warm for 11 hours. The reaction solution is cooled to 80°C, filtered, the catalyst is washed with 120ml hot solvent, and the solvent is recovered by vacuum distillation to obtain 232g N-ethylcarbazole with a yield of 97.6% and a GC chromatographic purity of 98.3%.

[0024] In a 2000ml reactor, add 550g of N-ethylcarbazole prepared in step 3, 600ml of o-dichlorobenzene, 120g of UiO-66 and 120g of ZIF-8, stir thoroughly, and react at 120°C for 8-12 hours using a solvent thermal method. After the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

[0025] In this application, UiO-66 and ZIF-8 are used as metal organic frameworks (MOFs) materials to improve the hydrogen storage capacity of the product. Both UiO-66 and ZIF-8 have extremely high specific porosity (usually in the range of 1200-1800 m² / g) and highly meshed pore structures. These pores can effectively adsorb and store molecules in aqueous solution.

[0026] Oxygen molecules enter the microporous structure of the material through physical adsorption or chemical adsorption, so MOFs with high epoxy resin ratio can accommodate more oxygen and increase hydrogen storage capacity.

[0027] The pore sizes of UiO-66 are between 7.5 and 8 Å, while those of ZIF-8 are about 11.6 Å (large pores) and 3.4 Å (small pores). These micropore diameters match the size of hydrogen molecules, helping to effectively capture and store the foam molecules while preventing them from escaping easily.

[0028] The grid and diversity of the pore structure allow the material to store more oxygen and release it under appropriate conditions, improving the controllability and efficiency of hydrogen storage.

[0029] UiO-66 contains potassium oxygen clusters and ZIF-8 contains zinc ions. These metal nodes provide a highly stable framework structure for the material. At the same time, the reaction of metal ligands can enhance the reaction with aqueous solution and improve the adsorption capacity of aqueous solution.

[0030] Both UiO-66 and ZIF-8 have good thermal stability, which enables them to maintain structural defects in different temperature ranges, thus ensuring the safety and efficiency of hydrogen storage.

[0031] Under high temperature or pressure conditions, these MOFs materials can still maintain efficient hydrogen storage capabilities and are not prone to structural collapse.

[0032] The interactions between foam molecules and the metal centers and organic ligands in MOFs are usually weak, belonging to van der Waals and electrostatic interactions. This makes the adsorption and release of foams relatively easy, achieving efficient foam contact. Especially under low temperature conditions, this weak response is more suitable for hydrogen storage applications.

[0033] When UiO-66 and ZIF-8 are combined with organic composite materials such as N-carbazole, they can further enhance the hydrogen storage capacity. The combination of MOFs and N-carbazole can improve the adsorption kinetics of aqueous solutions and increase the hydrogen storage capacity of the material. MOFs, as supporting materials, increase the hydrogen storage density of the entire system and provide more adsorption sites for aqueous solutions.

[0034] The high specific pore size, microporous structure, good thermal stability and surface adjustability of UiO-66 and ZIF-8 make them have obvious advantages in improving the storage capacity and hydrogen storage efficiency of reflux. These materials can effectively improve the hydrogen storage performance of composite materials by providing additional advantageous anion adsorption sites and enhanced anion exchange capacity.

[0035] The above description of the embodiments is to facilitate the understanding and use of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing hydrogen storage material N-ethylcarbazole, characterized in that: The steps include: Step 1: Prepare the intermediate tetrahydrocarbazole, add 8-12 parts of phenylhydrazine hydrochloride and 32-48 parts of water into a three-necked flask, stir at room temperature until dissolved; then add 3.4-3.6 parts of 30% hydrochloric acid, raise the temperature to 70°C, and dropwise add 5.6-1.4 parts of cyclohexanone; Continue to keep warm for 2 hours, cool, filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 68.4-102.6 parts of the intermediate tetrahydrocarbazole prepared in step 1, 160-240 parts of sodium hydroxide aqueous solution, 66.8-171.1 parts of benzene and 0.8-1.2 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 78-117 parts of ethyl chloride, slowly heat to 105° C., pressure of 0.25 MPa, keep warm for 6 hours, and cool to room temperature; separate the alkali layer, neutralize with 30% hydrochloric acid, wash to neutrality, and distill to recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 53-76.5 parts of the liquid product obtained in step 2, 213-320 parts of solvent o-dichlorobenzene, and 0.8-1.2 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 26.5-40 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 3-6 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 1-2 parts of organic framework materials into a reaction kettle, use a solvent thermal method, react at 120°C for 8-12 hours, and after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

2. The method for synthesizing the hydrogen storage material N-ethylcarbazole according to claim 1, characterized in that: Step 1: Prepare the intermediate tetrahydrocarbazole, add 8 parts of phenylhydrazine hydrochloride and 32 parts of water into a three-necked flask, stir at room temperature until dissolved; then add 3.4 parts of 30% hydrochloric acid, raise the temperature to 70°C and dropwise add 5.6 parts of cyclohexanone; Continue to keep warm for 2 hours, cool, filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 68.4 parts of the intermediate tetrahydrocarbazole prepared in step 1, 160 parts of sodium hydroxide aqueous solution, 66.8 parts of benzene and 0.8 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 78 parts of ethyl chloride, slowly heat to 105°C, the pressure is 0.25MPa, keep warm for 6 hours, and cool to room temperature; separate the alkali layer, neutralize it in 30% hydrochloric acid, wash it to neutrality, and distill and recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 53 parts of the liquid product obtained in step 2, 213 parts of solvent o-dichlorobenzene, and 0.8 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 26.5 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 3 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 1 part of organic framework material into the reaction kettle, use the solvent thermal method, react at 120°C for 8-12 hours, and after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

3. The method for synthesizing the hydrogen storage material N-ethylcarbazole according to claim 1, characterized in that: Step 1: Prepare the intermediate tetrahydrocarbazole, add 12 parts of phenylhydrazine hydrochloride and 48 parts of water into a three-necked flask, stir at room temperature until dissolved; then add 3.6 parts of 30% hydrochloric acid, raise the temperature to 70°C and dropwise add 1.4 parts of cyclohexanone; Continue to keep warm for 2 hours, cool, filter, wash with water, and dry to obtain the intermediate tetrahydrocarbazole; Step 2: Prepare a liquid product. In an autoclave, add 102.6 parts of the intermediate tetrahydrocarbazole prepared in step 1, 240 parts of sodium hydroxide aqueous solution, 171.1 parts of benzene and 1.2 parts of triethylbenzylammonium bromide in sequence, and close the autoclave; after nitrogen replacement three times, add 117 parts of ethyl chloride, slowly heat to 105°C, the pressure is 0.25MPa, keep the temperature for 6 hours, and cool to room temperature; separate the alkali layer, neutralize it in 30% hydrochloric acid, wash it to neutrality, and distill and recover benzene to obtain a liquid product; Step 3: In a three-necked flask equipped with a reflux condenser, 76.5 parts of the liquid product obtained in step 2, 320 parts of solvent o-dichlorobenzene, and 1.2 parts of 5% platinum / carbon are added in sequence, the temperature is raised to reflux, and the temperature is kept for 1 hour; the reaction is cooled to 80°C, filtered, 40 parts of hot solvent are added to wash the catalyst, and the solvent is recovered by vacuum distillation to obtain the product N-ethylcarbazole; Step 4: Add 6 parts of N-ethylcarbazole prepared in step 3, an appropriate amount of solvent, and 2 parts of organic framework materials into the reaction kettle, use the solvent thermal method, react at 120°C for 8-12 hours, and after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain the product hydrogen storage N-ethylcarbazole.

4. A method for synthesizing N-ethylcarbazole as a hydrogen storage material according to claims 1-3, characterized in that: The organic framework materials are UiO-66 and ZIF-8.

5. The method for synthesizing the hydrogen storage material N-ethylcarbazole according to claim 2, characterized in that: In the step 4, the solution is continuously stirred during the reaction in the reactor.