Mg2FeH6-coated MCM-41 composite material as well as preparation method and application thereof

Abstract

The invention is applicable to the technical field of solid hydrogen storage, and provides an Mg2FeH6-coated MCM-41 composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, preparing MCM-41, then synthesizing Mg / Fe-MOF on an MCM-41 molecular sieve in situ, and carbonizing and hydrogenating to obtain the Mg2FeH6-coated MCM-41 composite material. The prepared material shows excellent hydrogen storage performance under the conditions that the temperature is 300 DEG C, the hydrogen absorption pressure is 3 MPa and the hydrogen desorption pressure is 0.2 MPa, the maximum hydrogen absorption capacity reaches 12.8 wt%, and the maximum hydrogen desorption capacity reaches 12.6 wt%; the Mg2FeH6-coated MCM-41 prepared by taking MOF as a template has the advantages of nanocrystallization structure and high specific surface area, provides a rapid hydrogen transmission channel, improves the hydrogen storage performance of the material, and shows good reversibility; the method is simple in process and suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state hydrogen storage, and particularly relates to an Mg 2 FeH 6 @MCM-41 composite material and its preparation method and application. Background Technique

[0002] Hydrogen is a colorless, odorless and extremely light gas with high energy density and wide chemical activity, and it is one of the most abundant elements in the universe. In the energy field, hydrogen, as a clean energy source, is widely used in fuel cells and hydrogen engines, and can be efficiently converted into electrical energy or heat energy. Moreover, its combustion product is mainly water and no greenhouse gases will be generated. However, the storage and transportation of hydrogen have always been the key problems restricting the development of hydrogen energy. Traditional high-pressure gaseous hydrogen storage and liquid hydrogen storage have problems of safety hazards and high costs. In recent years, solid-state hydrogen storage technology has emerged. It uses solid materials as intermediate media to store hydrogen. This technology can store hydrogen safely at normal temperature and pressure, greatly reducing the risk of hydrogen leakage, and has advantages such as high volumetric hydrogen storage density, good safety and low cost. Therefore, it shows broad application prospects in many fields such as fuel cell vehicles, stationary energy storage, and backup power supplies. With the continuous progress of technology and the reduction of costs, solid-state hydrogen storage is expected to play a more important role in the future energy system.

[0003] At present, the research on solid-state hydrogen storage materials mainly focuses on metal-based hydrogen storage materials, coordination hydrides, and physical adsorption materials, etc. Among them, magnesium-based hydrogen storage materials have attracted much attention due to their high capacity and good hydrogen storage performance. The literature [International Journal of Hydrogen Energy, 2019, 44(29): 15239-15245] reported an Mg@C 60 nanosheet with multiple hydrogen storage sites prepared by a simple ball-milling process, and Mg nanoparticles are uniformly distributed in C 60The upper nanosheets can achieve a hydrogen storage capacity of 12.50 wt% under a pressure of 45 bar, but their dependence on high-pressure conditions limits their practical applications. In addition, Chinese Patent No. CN115140706A discloses a Mg-Ni-Si-based hydrogen storage alloy prepared by ball milling using master alloy as raw material. The hydrogen storage capacity of this alloy is only 5.1% when tested under a pressure of 1 Mpa, with a relatively low capacity. Another Chinese invention patent No. CN108950260A discloses Mg-based hydrogen storage nanowires obtained by electrospinning. This material not only has a larger total hydrogen storage capacity but also faster hydrogen absorption and desorption rates. The maximum hydrogen absorption capacity reaches 12.12%, and the maximum hydrogen desorption capacity reaches 7.89%. However, its reversibility still needs to be further improved. In summary, Mg-based hydrogen storage materials exhibit excellent hydrogen absorption and desorption properties. The future research and development direction of hydrogen storage materials will focus on the preparation of nanomaterials and multi-metal modified materials. Therefore, the present invention proposes a Mg 2 FeH 6 @MCM-41 composite material and its preparation method and application. Summary of the Invention

[0004] The purpose of the present invention is to provide a Mg 2 FeH 6 @MCM-41 composite material and its preparation method and application, aiming to solve the problems raised in the above background technology.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A preparation method of a Mg 2 FeH 6 @MCM-41 composite material, comprising the following steps:

[0007] Step S1: Prepare MCM-41;

[0008] Dissolve cetyltrimethylammonium bromide in deionized water, place it in a water bath and stir; add ammonia water to the solution and continue stirring; transfer the solution to a water bath, add tetraethoxysilane dropwise, continue stirring and then let it stand; after suction filtration and washing, dry the obtained solid in an oven, and finally calcine it in a muffle furnace to obtain MCM-41 molecular sieve;

[0009] Step S2: Prepare Mg / Fe-MOF@MCM-41;

[0010] Disperse the MCM-41 prepared in Step S1 in deionized water to obtain Solution A; Dissolve Mg(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2O and 2,5-dihydroxyterephthalic acid are dissolved in N,N-dimethylformamide and ethanol to obtain solution B; solution A and solution B are mixed and transferred to an autoclave for reaction. After cooling, it is centrifuged, washed, and dried under vacuum to obtain Mg / Fe-MOF@MCM-41;

[0011] Step S3: Prepare Mg 2 FeH 6 @MCM-41 composite material;

[0012] The Mg / Fe-MOF@MCM-41 prepared in step S2 is placed in a tubular furnace and calcined under a nitrogen atmosphere. After cooling, the sample is placed in a reaction kettle and treated under a hydrogen atmosphere to finally obtain Mg 2 FeH 6 @MCM-41 composite material.

[0013] Furthermore, the specific process of step S1 is as follows:

[0014] Cetyltrimethylammonium bromide is dissolved in deionized water and placed in a water bath at 40 - 60 °C, and stirred for 10 - 20 min; ammonia water is added to the solution at a dropping rate of 50 - 60 drops / min, and stirring is continued for 10 - 20 min; the solution is transferred to a water bath at 40 - 60 °C, and tetraethoxysilane is added at a dropping rate of 40 - 60 drops / min, and stirring is continued for 1 - 2 h and then left to stand for 3 - 6 h; suction filtration and washing are carried out 2 - 3 times, the obtained solid is dried in an oven at 80 - 100 °C for 12 - 24 h, and finally calcined in a muffle furnace at 500 - 600 °C for 6 - 8 h to obtain MCM-41 molecular sieve.

[0015] Furthermore, in step S1, the mass ratio of cetyltrimethylammonium bromide, ammonia water, tetraethoxysilane, and deionized water is 1:3 - 5:3 - 5:60 - 80.

[0016] Furthermore, the specific process of step S2 is as follows:

[0017] The MCM-41 prepared in step S1 is dispersed in deionized water to obtain solution A; Mg(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O and 2,5-dihydroxyterephthalic acid are dissolved in N,N-dimethylformamide and ethanol to obtain solution B; solution A and solution B are mixed and transferred to an autoclave, and reacted at 100 - 120 °C for 24 - 48 h. After cooling, it is centrifuged and washed with water 3 - 5 times, and finally dried under vacuum at 130 - 150 °C for 2 - 4 h to obtain Mg / Fe-MOF@MCM-41.

[0018] Further, in the step S2, the mass ratio of 2,5-dihydroxyterephthalic acid, Mg(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, MCM-41, ethanol, deionized water and N,N-dimethylformamide is 1:1 - 2:2 - 4:4 - 6:20 - 25:20 - 30:400 - 450.

[0019] Further, the specific process of the step S3 is as follows:

[0020] Place the Mg / Fe-MOF@MCM-41 prepared in the step S2 in a tubular furnace, calcine it at 400 - 500 °C for 4 - 6 h under a nitrogen atmosphere, after cooling, place the sample in a reaction kettle at 300 - 400 °C and 4 - 6 MPa hydrogen for 8 - 10 h, and finally obtain the Mg 2 FeH 6 @MCM-41 composite material.

[0021] A Mg 2 FeH 6 @MCM-41 composite material prepared by the preparation method of the Mg 2 FeH 6 @MCM-41 composite material according to the above.

[0022] The present invention has the following beneficial effects:

[0023] 1. The present invention provides a preparation method of a Mg 2 FeH 6 @MCM-41 composite material. The prepared material shows excellent hydrogen storage performance under the conditions of a temperature of 300 °C, a hydrogen absorption pressure of 3 MPa, and a hydrogen desorption pressure of 0.2 MPa. Its maximum hydrogen absorption capacity reaches 12.8 wt%, and its maximum hydrogen desorption capacity reaches 12.6 wt%.

[0024] 2. The present invention uses MOF as a template to prepare Mg 2 FeH 6 @MCM-41, which has the advantages of a nanostructured structure and a high specific surface area. At the same time, it provides a rapid hydrogen transmission channel, improves the hydrogen storage performance of the material, and shows good reversibility.

[0025] 3. The Mg 2 FeH 6The @MCM-41 composite material has a simple process and is suitable for large-scale production. The present invention provides a new idea for the development of high-performance solid hydrogen storage materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a hydrogen absorption performance curve graph.

[0027] Figure 2 It is a hydrogen desorption performance curve graph. DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention will be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0029] The present invention provides a preparation method of a Mg 2 FeH 6 @MCM-41 composite material, comprising the following steps:

[0030] Step S1: Prepare MCM-41;

[0031] Dissolve cetyltrimethylammonium bromide (CTAB) in deionized water, place it in a water bath at 40 - 60 °C, and stir for 10 - 20 min; add ammonia water to the solution at a dropping rate of 50 - 60 drops / min, and continue to stir for 10 - 20 min; transfer the solution to a water bath at 40 - 60 °C, add tetraethoxysilane (TEOS) at a dropping rate of 40 - 60 drops / min, continuously stir for 1 - 2 h and then let it stand for 3 - 6 h; filter and wash 2 - 3 times, dry the obtained solid in an oven at 80 - 100 °C for 12 - 24 h, and finally calcine it in a muffle furnace at 500 - 600 °C for 6 - 8 h to obtain MCM-41 molecular sieve.

[0032] Among them, the mass ratio of CTAB, ammonia water, TEOS and deionized water is 1:3 - 5:3 - 5:60 - 80.

[0033] Step S2: Prepare Mg / Fe-MOF@MCM-41;

[0034] Disperse the MCM-41 prepared in step S1 in deionized water to obtain solution A; dissolve Mg(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2O and 2,5-dihydroxytriphenyl dicarboxylic acid (DHTP) are dissolved in N,N-dimethylformamide (DMF) and ethanol to obtain Solution B; Solution A and Solution B are mixed and transferred to an autoclave, and reacted at 100-120 °C for 24-48 h. After cooling, it is centrifugally washed with water 3-5 times, and finally vacuum dried at 130-150 °C for 2-4 h to obtain Mg / Fe-MOF@MCM-41.

[0035] Among them, the mass ratio of DHTP, Mg(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, MCM-41, ethanol, deionized water and DMF is 1:1-2:2-4:4-6:20-25:20-30:400-450.

[0036] Step S3: Prepare the Mg 2 FeH 6 @MCM-41 composite material;

[0037] The Mg / Fe-MOF@MCM-41 prepared in Step S2 is placed in a tubular furnace and calcined at 400-500 °C for 4-6 h under a nitrogen atmosphere. After cooling, the sample is placed in a reaction kettle at 300-400 °C and 4-6 MPa of hydrogen for 8-10 h to finally obtain the Mg 2 FeH 6 @MCM-41 composite material.

[0038] In the embodiment of the present invention, the present invention first prepares MCM-41, then in-situ synthesizes Mg / Fe-MOF on the MCM-41 molecular sieve, and then obtains Mg 2 FeH 6 @MCM-41 composite material through carbonization and hydrogenation. MCM-41 has a high specific surface area, is rich in hydroxyl groups on the surface, provides additional adsorption sites, enhances physical adsorption, and its pores are arranged in a hexagonal order, which is conducive to the orderly storage and release of hydrogen molecules, and improves the reversibility of hydrogen storage. The in-situ synthesized Mg / Fe-MOF maintains a high specific surface area and pore characteristics after carbonization, and has better electrical conductivity, which helps the rapid transfer of electrons. After hydrogenation, the Mg 2 FeH 6 has a cubic structure, and its ion group [FeH 6 4- has an octahedral structure and is surrounded by Mg. This unique structure provides a good spatial environment for the storage of hydrogen. The present invention provides a new idea for the development of high-performance solid-state hydrogen storage materials.

[0039] ​The present invention will be further described in conjunction with specific embodiments.

[0040] Example 1: The present invention provides a preparation method of Mg 2 FeH 6 @MCM-41 composite material, and the steps are as follows:

[0041] Step S1: Prepare MCM-41;

[0042] Dissolve 10 g of cetyltrimethylammonium bromide (CTAB) in 600 g of deionized water, place it in a water bath at 40 °C, and stir for 10 min; add 30 g of ammonia water to the solution at a dropping rate of 50 drops / min, and continue to stir for 10 min; transfer the solution to a water bath at 40 °C, add 30 g of tetraethoxysilane (TEOS) at a dropping rate of 40 drops / min, continuously stir for 1 h, and then let it stand for 3 h; perform suction filtration and washing twice, dry the obtained solid in an oven at 80 °C for 12 h, and finally calcine it in a muffle furnace at 500 °C for 6 h to obtain MCM-41 molecular sieve.

[0043] Step S2: Prepare Mg / Fe-MOF@MCM-41;

[0044] Disperse 4 g of MCM-41 in 20 g of deionized water to obtain solution A; dissolve 1 g of Mg(NO 3 ) 2 ·6H 2 O, 2 g of Fe(NO 3 ) 3 ·9H 2 O and 1 g of 2,5-dihydroxyterephthalic acid (DHTP) in 400 g of N,N-dimethylformamide (DMF) and 20 g of ethanol to obtain solution B. Mix solution A and solution B, transfer them to an autoclave, react at 100 °C for 24 h, cool, centrifuge and wash with deionized water three times, and finally dry in vacuo at 130 °C for 2 h to obtain Mg / Fe-MOF@MCM-41.

[0045] Step S3: Prepare Mg 2 FeH 6 @MCM-41 composite material;

[0046] Place Mg / Fe-MOF@MCM-41 in a tubular furnace, calcine it at 400 °C for 4 h under a nitrogen atmosphere. After cooling, place the sample in a reaction kettle at 300 °C and 4 MPa of hydrogen for 8 h, and finally obtain Mg 2 FeH 6 @MCM-41 composite material.

[0047] Example 2: The present invention provides a Mg 2 FeH6 Preparation method of @MCM-41 composite material, the steps are as follows:

[0048] Step S1: Prepare MCM-41;

[0049] Dissolve 10 g of cetyltrimethylammonium bromide (CTAB) in 800 g of deionized water, place it in a water bath at 60 °C, and stir for 20 min; add 50 g of ammonia water to the solution at a dropping rate of 60 drops / min, and continue to stir for 20 min; transfer the solution to a water bath at 60 °C, and add 50 g of tetraethoxysilane (TEOS) at a dropping rate of 60 drops / min, continuously stir for 2 h and then let it stand for 6 h; filter and wash 3 times, dry the obtained solid in an oven at 100 °C for 24 h, and finally calcine it in a muffle furnace at 600 °C for 8 h to obtain MCM-41 molecular sieve.

[0050] Step S2: Prepare Mg / Fe-MOF@MCM-41;

[0051] Disperse 6 g of MCM-41 in 30 g of deionized water to obtain solution A; dissolve 2 g of Mg(NO 3 ) 2 ·6H 2 O, 4 g of Fe(NO 3 ) 3 ·9H 2 O and 1 g of 2,5-dihydroxyterephthalic acid (DHTP) in 450 g of N,N-dimethylformamide (DMF) and 25 g of ethanol to obtain solution B; mix solutions A and B, and transfer them to an autoclave, react at 120 °C for 48 h, cool, centrifuge and wash with deionized water 5 times, and finally dry in vacuo at 150 °C for 4 h to obtain Mg / Fe-MOF@MCM-41.

[0052] Step S3: Prepare Mg 2 FeH 6 @MCM-41 composite material;

[0053] Place Mg / Fe-MOF@MCM-41 in a tubular furnace, calcine it in a nitrogen atmosphere at 500 °C for 6 h, after cooling, place the sample in a reaction kettle at 400 °C and 6 MPa of hydrogen for 10 h, and finally obtain Mg 2 FeH 6 @MCM-41 composite material.

[0054] Example 3: The present invention provides a preparation method of Mg 2 FeH 6 @MCM-41 composite material, the steps are as follows:

[0055] Step S1: Prepare MCM-41;

[0056] Dissolve 10 g of cetyltrimethylammonium bromide (CTAB) in 800 g of deionized water, place it in a water bath at 60 °C, and stir for 20 min; add 50 g of ammonia water to the solution at a dropping rate of 60 drops / min, and continue to stir for 20 min; transfer the solution to a water bath at 60 °C, and add 50 g of tetraethoxysilane (TEOS) at a dropping rate of 60 drops / min, continuously stir for 2 h and then let it stand for 6 h; filter and wash 3 times, dry the obtained solid in an oven at 100 °C for 24 h, and finally calcine it in a muffle furnace at 550 °C for 8 h to obtain MCM-41 molecular sieve.

[0057] Step S2: Prepare Mg / Fe-MOF@MCM-41;

[0058] Disperse 5 g of MCM-41 in 30 g of deionized water to obtain solution A; dissolve 2 g of Mg(NO 3 ) 2 ·6H 2 O, 4 g of Fe(NO 3 ) 3 ·9H 2 O and 1 g of 2,5-dihydroxyterephthalic acid (DHTP) in 450 g of N,N-dimethylformamide (DMF) and 25 g of ethanol to obtain solution B; mix solutions A and B, and transfer them to an autoclave, react at 110 °C for 48 h, after cooling, centrifuge and wash with deionized water 5 times, and finally dry under vacuum at 150 °C for 4 h to obtain Mg / Fe-MOF@MCM-41.

[0059] Step S3: Prepare Mg 2 FeH 6 @MCM-41 composite material;

[0060] Place Mg / Fe-MOF@MCM-41 in a tubular furnace, calcine it at 450 °C for 6 h under a nitrogen atmosphere, after cooling, place the sample in a reaction kettle at 400 °C and 6 MPa of hydrogen for 10 h to obtain Mg 2 FeH 6 @MCM-41 composite material.

[0061] Comparative Example 1: The difference between this comparative example and Example 1 is that MCM-41 was not added (that is, step S1 in Example 1 was not carried out, and MCM-41 was not added when carrying out step S2).

[0062] Comparative Example 2: The difference between this comparative example and Example 1 is that hydrogenation and carbonization were not carried out (that is, step S3 in Example 1 was not carried out).

[0063] The experimental steps for testing the hydrogen storage performance of the materials prepared in Examples 1-3 and Comparative Examples 1-2 are as follows:

[0064] When evaluating the hydrogen storage performance, the sample is first subjected to 3 activation hydrogen absorption and desorption cycles at 350 °C to remove the oxide film on the material surface. The pressures during hydrogen absorption and desorption are 3 MPa and 0.2 MPa respectively. After activation, the sample is tested for hydrogen absorption and desorption performance at 300 °C, and the pressures during hydrogen absorption and desorption are 3 MPa and 0.2 MPa respectively. The specific test data are recorded in Table 1.

[0065] Table 1 Hydrogen Storage Performance Test

[0066] Name Weight (g) Hydrogen absorption capacity (wt.%) Hydrogen desorption capacity (wt.%) Example 1 0.5 11.6 11.4 Example 2 0.5 12.4 12.1 Example 3 0.5 12.8 12.6 Comparative Example 1 0.5 6.5 4.4 Comparative Example 2 0.5 8.6 8.3

[0067] As can be seen from the data in Table 1, the synthesized Mg 2 FeH 6 @MCM-41 composite material exhibits excellent hydrogen storage performance. Under the conditions of a temperature of 300 °C, a hydrogen absorption pressure of 3 MPa, and a hydrogen desorption pressure of 0.2 MPa, its maximum hydrogen absorption capacity reaches 12.8 wt%, and the maximum hydrogen desorption capacity reaches 12.6 wt%. In contrast, the hydrogen storage performance of the material without MCM-41 and without carbonization and hydrogenation is significantly reduced. This result indicates that as a carrier, the hexagonal ordered pores and more adsorption active sites provided by MCM-41 are beneficial to hydrogen storage and release. Figure 1 and Figure 2 are the hydrogen absorption and desorption performance curves respectively. As can be seen from the figure, after 30 minutes of hydrogen absorption, the material reaches saturation, and the material obtained in Example 3 has the best performance; the hydrogen desorption is also completed in 30 minutes, and the materials obtained in Examples 1-3 exhibit excellent reversibility during hydrogen absorption and desorption. In contrast, the sample without MCM-41 has poor reversibility. In addition, the hydrogen storage performance of the material treated by carbonization and hydrogenation is significantly improved, indicating that the formed hydride is the key to improving the material performance.

[0068] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes in form and details made to the present invention without departing from the spirit and scope of the present invention defined by the appended claims all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Mg2FeH6@MCM-41 composite material, characterized in that: The following steps are involved: Step S1: preparing MCM-41; Dissolve hexadecyltrimethylammonium bromide in deionized water and stir in a water bath; Ammonia water was added dropwise to the solution and stirring was continued; the solution was transferred to a water bath, tetraethoxysilane was added dropwise, stirring was continued and then allowed to stand; after suction filtration and washing, the obtained solid was dried in an oven and finally calcined in a muffle furnace to obtain MCM-41 molecular sieve; Step S2: preparing Mg / Fe-MOF@MCM-41; The MCM-41 prepared in step S1 is dispersed in deionized water to obtain a solution A; Mg(NO3)2·6H2O, Fe(NO3)3·9H2O and 2,5-dihydroxytriphenylene glycol are dissolved in N,N-dimethylformamide and ethanol to obtain a solution B; the solution A and the solution B are mixed and transferred to an autoclave for reaction, cooled, centrifuged, washed and vacuum dried to obtain Mg / Fe-MOF@MCM-41; Step S3: preparing Mg2FeH6@MCM-41 composite material; The Mg / Fe-MOF@MCM-41 prepared in step S2 was placed in a tube furnace and calcined under a nitrogen atmosphere. After cooling, the sample was placed in a reactor and treated under a hydrogen atmosphere to finally obtain a Mg2FeH6@MCM-41 composite material.

2. The method for preparing the Mg2FeH6@MCM-41 composite material according to claim 1, characterized in that: The specific process of step S1 is as follows: Dissolve hexadecyltrimethylammonium bromide in deionized water, place in a water bath at 40-60°C, and stir for 10-20 minutes; add ammonia water to the solution at a dropping speed of 50-60 drops / min, and continue stirring for 10-20 minutes; transfer the solution to a water bath at 40-60°C, add tetraethoxysilane at a dropping speed of 40-60 drops / min, continue stirring for 1-2 hours, and then stand for 3-6 hours; filter and wash 2-3 times, dry the obtained solid in an oven at 80-100°C for 12-24 hours, and finally calcine in a muffle furnace at 500-600°C for 6-8 hours to obtain MCM-41 molecular sieve.

3. The method for preparing the Mg2FeH6@MCM-41 composite material according to claim 2, characterized in that: In the step S1, the mass ratio of hexadecyltrimethylammonium bromide, ammonia water, tetraethoxysilane and deionized water is 1:3-5:3-5:60-80.

4. The method for preparing the Mg2FeH6@MCM-41 composite material according to claim 1, characterized in that: The specific process of step S2 is as follows: The MCM-41 prepared in step S1 is dispersed in deionized water to obtain solution A; Mg(NO3)2·6H2O, Fe(NO3)3·9H2O and 2,5-dihydroxytriphenylcarbamate are dissolved in N,N-dimethylformamide and ethanol to obtain solution B; solution A and solution B are mixed and transferred to an autoclave, reacted at 100-120°C for 24-48h, cooled and washed by centrifugation with water for 3-5 times, and finally vacuum dried at 130-150°C for 2-4h to obtain Mg / Fe-MOF@MCM-41.

5. The method for preparing the Mg2FeH6@MCM-41 composite material according to claim 4, characterized in that: In the step S2, the mass ratio of 2,5-dihydroxytribenzoic acid, Mg(NO3)2·6H2O, Fe(NO3)3·9H2O, MCM-41, ethanol, deionized water and N,N-dimethylformamide is 1:1-2:2-4:4-6:20-25:20-30:400-450.

6. The method for preparing the Mg2FeH6@MCM-41 composite material according to claim 1, characterized in that: The specific process of step S3 is as follows: The Mg / Fe-MOF@MCM-41 prepared in step S2 was placed in a tubular furnace and calcined at 400-500°C for 4-6 hours under a nitrogen atmosphere. After cooling, the sample was placed in a reactor at 300-400°C and 4-6MPa hydrogen for 8-10 hours to finally obtain a Mg2FeH6@MCM-41 composite material.

7. A Mg2FeH6@MCM-41 composite material obtained according to the preparation method of the Mg2FeH6@MCM-41 composite material according to any one of claims 1 to 6.

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