Zirconium-based MOFs solid hydrogen storage material and preparation method thereof

Abstract

The invention discloses a zirconium-based MOFs solid hydrogen storage material and a preparation method thereof.The preparation method comprises the steps that zirconium chloride and fumaric acid are mixed and subjected to ball milling, and raw material powder is obtained; dissolving the raw material powder in a mixed solvent of DMF (Dimethyl Formamide) and formic acid, and performing ultrasonic treatment to form a uniform precursor solution; heating the precursor solution, carrying out reactive crystallization, cooling, and centrifuging to obtain a precipitate; and sequentially washing and drying the precipitate by using a DMF solution and methanol, and vacuumizing and activating under a heating condition to prepare the zirconium-based MOFs solid hydrogen storage material. By optimizing the organic ligand, the structure of the Zr-based MOFs material is accurately controlled, the problem of slow dynamics in the hydrogen storage process of the material is effectively solved, and the hydrogen adsorption, diffusion and release performance of the material is improved.

Description

Technical Field

[0001] The present invention belongs to the field of zirconium-based solid hydrogen storage materials, and relates to a zirconium-based MOFs solid hydrogen storage material and a preparation method thereof. Background Art

[0002] As a clean energy source, hydrogen energy has great application potential, but it has not been able to achieve large-scale application due to the bottleneck of storage and transportation technologies. Currently, the mainstream hydrogen storage technologies are divided into two types: high-pressure gaseous hydrogen storage and cryogenic liquid hydrogen storage. High-pressure gaseous hydrogen storage technology has the highest maturity and prominent cost advantages. However, due to the high safety pressure threshold, the improvement of hydrogen storage density is highly restricted. Phenomena such as hydrogen embrittlement, hydrogen permeation, and aging lead to a high degree of dependence on carbon fiber materials, and the construction of transportation pipeline networks lags seriously behind. It is only suitable for short-distance, small and medium-scale transportation scenarios. Cryogenic liquid hydrogen storage has problems such as the physical limit of volume hydrogen storage density, no large room for development, over-reliance on imported core equipment, and high energy consumption costs for long-term storage, making it difficult to achieve large-scale application. In recent years, solid hydrogen storage has broken through the extreme limitations of traditional high-pressure and low-temperature storage and transportation conditions, and entered the public eye with significant safety advantages. It is accelerating penetration in fields such as distributed energy, and has considerable application prospects. Among them, metal-organic framework materials (MOFs) have significantly improved hydrogen storage performance compared with traditional metal solid hydrogen storage materials due to their high specific surface area and adjustable pore channels, becoming an excellent means of solid hydrogen storage. However, existing research shows that MOFs materials generally have problems such as high temperature sensitivity, obvious environmental impact (most MOFs decompose when encountering water), slow hydrogen diffusion rate (adsorption at room temperature requires >30 minutes), complex preparation methods, and long production cycles. For example, Zn-based MOFs materials have extremely poor water stability, insufficient thermal stability, and lack of open metal sites; Cu-based MOFs materials have low mechanical strength and produce highly toxic substances when encountering water; Fe / Mn-based MOFs materials have low specific surface area and require high-temperature reduction, etc. It still needs a long time to develop to achieve large-scale industrial application. Zr-based MOFs materials have extremely strong water stability and relatively high specific surface area compared with other matrix materials, which is of great significance for the safe storage and transportation of hydrogen. However, due to the failure to effectively control the pore size and pore structure of existing Zr-based MOFs materials, it is difficult to overcome the problems of poor hydrogen absorption / desorption kinetic performance, limited hydrogen storage performance, short material cycle life, the research and development-engineering application conversion chain has not been connected, and the system integration cost is doubled compared with gaseous hydrogen storage in general solid hydrogen storage problems, which seriously restricts the large-scale deployment and application of solid hydrogen storage means and still needs further improvement. Summary of the Invention

[0003] The purpose of the present invention is to provide a zirconium-based MOFs solid hydrogen storage material and a preparation method thereof, to solve the problem of poor hydrogen absorption / desorption kinetic performance of Zr-based MOFs materials prepared by the prior art.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of a zirconium-based MOFs solid hydrogen storage material, comprising: Mix zirconium chloride and fumaric acid and ball mill to obtain raw material powder; Dissolve the raw material powder in a mixed solvent of DMF and formic acid, and form a uniform precursor solution through ultrasonic treatment; Heat the precursor solution, carry out reaction crystallization, centrifuge after cooling to obtain a precipitate; Wash the precipitate with DMF solution and methanol in sequence, dry, and carry out vacuum activation under heating conditions to prepare the zirconium-based MOFs solid hydrogen storage material.

[0005] Further, the molar ratio of zirconium chloride to fumaric acid is 0.8 - 1.2:1.

[0006] Further, the ball milling speed is 300 - 700 rpm, the ball-to-material ratio is 10:1, and the ball milling time is 0.5 - 1.5 h.

[0007] Further, the volume ratio of DMF to formic acid is 15 - 25:5 - 9.

[0008] Further, the mass-to-volume ratio of the raw material powder to the mixed solvent is 0.93 - 1.395 g:20 - 34 ml.

[0009] Further, the ultrasonic treatment time is 30 - 60 min, and the ultrasonic treatment frequency is 20 - 30 kHz.

[0010] Further, the heating temperature of the precursor solution is 110 - 150 °C, and the crystallization reaction time is 5 - 9 h.

[0011] Further, the washing process includes: First, centrifuge and wash the precipitate with DMF solution three times to remove unreacted reagents, and then further centrifuge and wash with methanol solution three times to remove the remaining DMF in the precipitate. The centrifugation rate is 3000 - 4000 rpm.

[0012] Further, the drying temperature is 80 - 120 °C, the drying time is 10 - 15 h, and the vacuum activation temperature is 130 - 170 °C.

[0013] A zirconium-based MOFs solid hydrogen storage material prepared by the above preparation method.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a zirconium-based MOFs solid hydrogen storage material. By deeply optimizing the organic ligand, zirconium chloride (ZrCl4) is mixed with fumaric acid, and a combined solvent of DMF and formic acid is used to dissolve the raw materials and coordinate them. The reaction system is modified with formic acid to optimize the structure of MOF in multiple ways. It can precisely control the crystal structure of zirconium-based MOFs, which is beneficial to the formation of a more stable and ordered pore structure, providing a more favorable spatial environment for the adsorption and storage of hydrogen, thereby improving the hydrogen storage performance of the material. Then, the uniformly formed precursor solution after ultrasonic treatment is subjected to reaction crystallization. After the reaction, it is naturally cooled to room temperature, and the precipitate is obtained by centrifugal separation and washed multiple times to remove unreacted reagents and trace solvents, reducing the impurity content in the material and improving the purity of the material. This not only helps to improve the hydrogen storage performance but also may reduce side reactions caused by impurities during the hydrogen storage and release processes, improving the service life and safety of the material. Finally, it is first dried and then vacuum-activated at a higher temperature to optimize the pore structure of the material, thereby obtaining a zirconium-based MOFs solid hydrogen storage material with excellent performance. The present invention aims at the problems in the pore size and pore structure design of Zr-based MOFs materials. By optimizing the organic ligand, precise control of the structure of Zr-based MOFs materials is achieved, improving the hydrogen adsorption, diffusion, and release performance of the materials. Through means such as ultrasonic mixing, mechanical ball milling, and activation treatment, the material synthesis process is optimized, improving the reaction activity and rate of the materials, effectively solving the problem of slow kinetics during the hydrogen storage process of the materials. Also, through the adjustment of reaction conditions, the hydrogen storage performance of the materials is further improved. The Zr-based MOFs materials prepared in the above manner show many improvements compared with traditional materials, such as light weight, high adsorption, weakened extreme conditions, reduced cost, increased yield, and enhanced recyclability.

[0015] Furthermore, the synthesis process of this patent adopts ultrasonic mixing and mechanical ball milling techniques. During ball milling, the raw material activity and mixing uniformity are improved with a suitable rotation speed and ball-to-material ratio. Ultrasonic treatment promotes the dissolution of raw materials, making the solution more uniform and stable.

[0016] Furthermore, in the link of controlling reaction conditions, the reagent dosage and ratio are precisely adjusted, and the crystallization temperature and duration are precisely controlled, allowing the crystals to grow fully and have a regular structure. This is not only highly energy-efficient but also greatly optimizes the material performance. After the product is dried at a suitable temperature, it is vacuum-activated at a higher temperature to optimize the pore structure and further improve the hydrogen absorption and release performance of the material.

[0017] The present invention also provides a zirconium-based MOFs solid hydrogen storage material. Through a triple synergistic strategy of modifying ligand materials, replacing and synthesizing process means innovation, and adjusting and optimizing reaction conditions, the present invention breaks through the bottleneck of the existing technology and obtains a Zr-based MOFs material with high comprehensive benefits. The hydrogen storage performance of this Zr-based MOFs material has been significantly improved, and its hydrogen adsorption and hydrogen storage capacity are significantly higher than those of traditional MOFs materials at normal temperature, high and low pressures. At the same time, the present invention avoids the extreme condition requirements of traditional technologies, shows wide working condition adaptability, extends the storage temperature range to -40~200°C, exhibits good humidity tolerance and wide-range pH stability, and has excellent stability. On this basis, the weight of the product has also been reduced to a certain extent compared with traditional products, greatly improving the safety of transportation and the convenience of carrying. The triple characteristics of high adsorption, wide working condition adaptability, and low weight drive the reduction of the weight and volume of storage and transportation and the reduction of compression energy consumption, forming multiple cost reduction effects, and the economic benefits of the product are significant. In addition, the present invention has excellent recyclability and large production volume, can greatly extend the service life of the material, shorten the production cycle, and has considerable industrialization potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a bar chart of the dehydrogenation mass ratio of the Zr-based MOFs hydrogen storage material prepared under the conditions of Examples 1-5 and Comparative Examples 1-5 of the present invention.

[0020] Figure 2 It is an EDS elemental energy spectrum diagram of the Zr-based MOFs hydrogen storage material prepared under the conditions of Example 3 of the present invention.

[0021] Figure 3 It is an SEM electron micrograph of the Zr-based MOFs hydrogen storage material prepared under the conditions of Example 3 of the present invention.

[0022] Figure 4 It is an SEM electron micrograph of the Zr-based MOFs hydrogen storage material prepared under the conditions of Comparative Example 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art with respect to the present invention. In case of conflict, the definitions in this specification shall prevail.

[0024] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0025] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0026] In this document, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar expressions cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0027] In this document, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as within the scope described in this specification.

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0029] Conventional instrumentation and equipment in the art are used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratios represent weight ratios.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings: The present invention provides a method for preparing a zirconium-based MOFs solid-state hydrogen storage material, which specifically includes the following steps: Mix two raw materials of zirconium chloride (ZrCl4) and fumaric acid (C4H4O4) with a molar ratio of 0.8 - 1.2:1, place them in a ball milling tank, and add ball milling media (such as stainless steel balls or zirconia balls).

[0031] 2) Perform ball milling on a ball mill at a speed of 300 - 700 rpm, with a ball-to-material ratio of 10:1 and a ball milling time of 0.5 - 1.5 h to obtain raw material powder.

[0032] 3) Dissolve the ball-milled raw material powder at a mass-to-volume ratio of 0.93 - 1.395 g:20 - 34 ml in a mixed solvent with a volume ratio of DMF to formic acid of 15 - 25:5 - 9, and use an ultrasonic device to process for 30 - 60 min at an ultrasonic treatment frequency of 20 - 30 kHz to achieve sufficient dissolution until the solution is clear, forming a uniform precursor solution.

[0033] 4) Transfer the clear precursor solution to a Teflon-lined autoclave and react at 110 - 150 °C for 5 - 9 h for crystallization.

[0034] 5) After the reaction is completed, naturally cool to room temperature and separate the precipitate by centrifugation (3000 - 4000 rpm).

[0035] 6) Use a DMF solution to wash the precipitate by centrifugation 3 times to remove unreacted reagents; then use a methanol solution to further wash by centrifugation 3 times to remove the remaining DMF in the precipitate at a centrifugation rate of 3000 - 4000 rpm.

[0036] 7) Dry the washed precipitate in an oven at 80 - 120 °C overnight for 10 - 15 h, and then perform vacuum activation at 130 - 170 °C to optimize the pore structure of the material, thus obtaining the zirconium-based MOFs solid-state hydrogen storage material.

[0037] The following further describes the present invention in detail through specific examples: Example 1: 1) Weigh 0.93 g of zirconium chloride (ZrCl4) and 0.58035 g of fumaric acid (C4H4O4), mix the two raw materials, place them in a ball milling tank, and add zirconia ball milling media.

[0038] 2) Perform ball milling on a ball mill at a speed of 300 rpm, with a ball-to-material ratio of 10:1 and a ball milling time of 30 min.

[0039] 3) Dissolve the ball-milled raw material powder in a mixed solvent prepared from 15 mL of DMF and 5 mL of formic acid, and use an ultrasonic device to treat it for 30 min at a frequency of 20 kHz to achieve sufficient dissolution and form a uniform precursor solution.

[0040] 4) Transfer the precursor solution to a Teflon-lined autoclave and carry out a crystallization reaction at 110 °C for 5 h.

[0041] 5) After the reaction is completed, naturally cool it to room temperature and obtain a precipitate by centrifugation at 3000 rpm.

[0042] 6) First, wash the precipitate 3 times by centrifugation with a DMF solution to remove unreacted reagents, and then further wash it 3 times by centrifugation with a methanol solution to remove the remaining DMF in the precipitate. The centrifugation rate is 3000 rpm.

[0043] 7) Dry the washed precipitate in an oven at 80 °C for 10 h, and then carry out dynamic vacuum activation at 130 °C to obtain the final MOF-801 material.

[0044] Example 2: 1) Weigh 1.04625 g of zirconium chloride (ZrCl4) and 0.58035 g of fumaric acid (C4H4O4). After mixing the two raw materials, place them in a ball mill jar and add zirconia ball milling media.

[0045] 2) Carry out ball milling on a ball mill at a rotation speed of 400 rpm, with a ball-to-material ratio of 10:1 and a ball milling time of 45 min.

[0046] 3) Dissolve the ball-milled raw material powder in a mixed solvent prepared from 17.5 mL of DMF and 6 mL of formic acid, and use an ultrasonic device to treat it for 40 min at a frequency of 22.5 kHz to achieve sufficient dissolution and form a uniform precursor solution.

[0047] 4) Transfer the precursor solution to a Teflon-lined autoclave and carry out a crystallization reaction at 120 °C for 6 h.

[0048] 5) After the reaction is completed, naturally cool it to room temperature and obtain a precipitate by centrifugation at 3200 rpm.

[0049] 6) First, wash the precipitate 3 times by centrifugation with a DMF solution to remove unreacted reagents, and then further wash it 3 times by centrifugation with a methanol solution to remove the remaining DMF in the precipitate. The centrifugation rate is 3200 rpm.

[0050] 7) Dry the washed precipitate in an oven at 90 °C for 11 h, and then perform dynamic vacuum activation at 140 °C to obtain the final MOF-801 material.

[0051] Example 3: 1) Weigh 1.1625 g of zirconium chloride (ZrCl4) and 0.58035 g of fumaric acid (C4H4O4). After mixing the two raw materials, place them in a ball milling jar and add zirconia ball milling media.

[0052] 2) Ball mill at a speed of 500 rpm on a ball mill, with a ball-to-material ratio of 10:1 and a ball milling time of 60 min.

[0053] 3) Dissolve the ball-milled raw material powder in a mixed solvent prepared from 20 mL of DMF and 7 mL of formic acid, and use an ultrasonic device to treat it at a frequency of 25 kHz for 45 min to achieve complete dissolution and form a uniform precursor solution.

[0054] 4) Transfer the precursor solution to a Teflon-lined autoclave and react at 130 °C for 7 h for crystallization reaction.

[0055] 5) After the reaction is completed, cool it to room temperature naturally and obtain a precipitate by centrifugation at 3500 rpm.

[0056] 6) First, wash the precipitate 3 times by centrifugation with a DMF solution to remove unreacted reagents, and then further wash it 3 times by centrifugation with a methanol solution to remove the remaining DMF in the precipitate, with a centrifugation rate of 3500 rpm.

[0057] 7) Dry the washed precipitate in an oven at 100 °C for 12 h, and then perform dynamic vacuum activation at 150 °C to obtain the final MOF-801 material.

[0058] Example 4: 1) Weigh 1.27875 g of zirconium chloride (ZrCl4) and 0.58035 g of fumaric acid (C4H4O4). After mixing the two raw materials, place them in a ball milling jar and add zirconia ball milling media.

[0059] 2) Ball mill at a speed of 600 rpm on a ball mill, with a ball-to-material ratio of 10:1 and a ball milling time of 75 min.

[0060] 3) Dissolve the ball-milled raw material powder in a mixed solvent prepared from 22.5 mL of DMF and 8 mL of formic acid, and use an ultrasonic device to treat it at a frequency of 27.5 kHz for 50 min to achieve complete dissolution and form a uniform precursor solution.

[0061] 4) Transfer the precursor solution to a Teflon-lined autoclave and carry out a crystallization reaction at 140 °C for 8 h.

[0062] 5) After the reaction is completed, cool it to room temperature naturally and obtain the precipitate by centrifugation at 3700 rpm.

[0063] 6) First, wash the precipitate 3 times by centrifugation with DMF solution to remove unreacted reagents, and then further wash it 3 times by centrifugation with methanol solution to remove the remaining DMF in the precipitate. The centrifugation rate is 3700 rpm.

[0064] 7) Dry the washed precipitate in an oven at 110 °C for 14 h, and then carry out dynamic vacuum activation at 160 °C to obtain the final MOF-801 material.

[0065] Example 5: 1) Weigh 1.395 g of zirconium chloride (ZrCl4) and 0.58035 g of fumaric acid (C4H4O4). After mixing the two raw materials, place them in a ball milling jar and add zirconia ball milling media.

[0066] 2) Carry out ball milling on a ball mill at a rotation speed of 700 rpm, with a ball-to-material ratio of 10:1 and a ball milling time of 90 min.

[0067] 3) Dissolve the ball-milled raw material powder in a mixed solvent prepared from 25 mL of DMF and 9 mL of formic acid, and use an ultrasonic device to treat it at a frequency of 30 kHz for 60 min to achieve complete dissolution and form a uniform precursor solution.

[0068] 4) Transfer the precursor solution to a Teflon-lined autoclave and carry out a crystallization reaction at 150 °C for 9 h.

[0069] 5) After the reaction is completed, cool it to room temperature naturally and obtain the precipitate by centrifugation at 4000 rpm.

[0070] 6) First, wash the precipitate 3 times by centrifugation with DMF solution to remove unreacted reagents, and then further wash it 3 times by centrifugation with methanol solution to remove the remaining DMF in the precipitate. The centrifugation rate is 4000 rpm.

[0071] 7) Dry the washed precipitate in an oven at 120 °C for 15 h, and then carry out dynamic vacuum activation at 170 °C to obtain the final MOF-801 material.

[0072] Comparative Example 1: 1) Dissolve 1.2 g (corresponding to 5.17 mmol) of zirconium chloride (ZrCl4) and 1.8 g (corresponding to 15.5 mmol) of fumaric acid (C4H4O4) in 93.4 ml (corresponding to 5.17 mol) of deionized water, and perform ultrasonic treatment until the solution becomes clear.

[0073] 2) Add the above solution to 19.5 ml (corresponding to 5.17 mmol) of formic acid. After ultrasonic mixing, place it in a Teflon-lined autoclave and carry out a crystallization reaction at 200 °C for 8 h.

[0074] 3) After the reaction is completed, let the solution cool naturally to room temperature, then collect the formed precipitate by centrifugation at 4000 rpm and wash it 3 times with deionized water.

[0075] 4) Dry at room temperature to obtain the final product.

[0076] Comparative Example 2: 1) Weigh 0.72184 g (corresponding to 2.24 mmol) of zirconyl chloride octahydrate (ZrOCl2·8H2O) and 0.59524 g (corresponding to 2.36 mmol) of trimethyl 1,3,5-benzenetricarboxylate (H3BTC).

[0077] 2) Mix the above materials in 30 mL of DMF and 30 mL of formic acid and perform ultrasonic treatment for 40 min.

[0078] 3) Place the mixture in a reaction kettle and react at 120 °C for 24 h to promote crystallization.

[0079] 4) Perform centrifugal washing 3 times each with DMF and methanol.

[0080] 5) Immerse the product in 10 mL of methanol for 3 days, and change the methanol 3 times during this period.

[0081] 6) Dry overnight at 60 °C for 24 h, collect the target product, and store it in a bottle.

[0082] Comparative Example 3: 1) Weigh 2.1655 g (corresponding to 6.72 mmol) of zirconyl chloride octahydrate (ZrOCl2·8H2O) and 1.7857 g (corresponding to 7.08 mmol) of trimethyl 1,3,5-benzenetricarboxylate (H3BTC).

[0083] 2) Mix the above materials in 30 mL of DMF and 30 mL of formic acid and perform ultrasonic treatment for 40 min.

[0084] 3) Place the mixture in a reaction kettle and react at 115 °C for 24 h to promote crystallization.

[0085] 4) Conduct centrifugal washing 3 times each with DMF and methanol.

[0086] 5) Immerse the product in 15 mL of methanol for 3 days, changing the methanol 3 times during this period.

[0087] 6) Dry at 80 °C for 12 h, collect the target product, and store it in a bottle.

[0088] Comparative Example 4: 1) Dissolve 1.61125 g (corresponding to 5.00 mmol) of zirconium oxychloride octahydrate (ZrOCl₂·8H₂O) and 0.58035 g (corresponding to 5.00 mmol) of fumaric acid (C₄H₄O₄) in a mixed solution of 22.5 mL of DMF and 7.5 mL of formic acid, and ultrasonically treat until the solution becomes clear.

[0089] (2) Place the above clear solution in a Teflon-lined autoclave and keep it in an oven at 130 °C for 12 h for crystallization.

[0090] (3) After the reaction is completed, let the solution cool naturally to room temperature, and then collect the formed precipitate by centrifugation (4000 rpm).

[0091] (4) Wash the precipitate 3 times with a DMF solution to remove unreacted reagents; then further wash 3 times with a methanol solution.

[0092] (5) Vacuum dry the washed product at 100 °C for 10 h to obtain the final product.

[0093] Comparative Example 5: 1) Weigh 0.221 g of zirconium chloride (ZrCl₄) and 0.158 g of terephthalic acid (H₂BDC), and dissolve the above materials in 30 mL of DMF.

[0094] 2) Add 1.87 mL of acetic acid for modification, and ultrasonically treat the mixed solution for 40 min.

[0095] 3) Place the mixture in a reaction kettle and react at 120 °C for 24 h to promote crystallization.

[0096] 4) After the reaction is completed, conduct centrifugal washing 3 times each with DMF and ethanol to remove unreacted reagents.

[0097] 5) Dry the product at 60 °C for 24 h, record the product mass, add chloroform according to the ratio of 0.3 g of product / 80 mL of chloroform, and immerse for 5 days for further modification.

[0098] 6) Vacuum dry the product after centrifugation at 188 °C for 48 h, and finally store the product in a bottle.

[0099] The non-isothermal hydrogen desorption performance of the Zr-based MOF materials prepared in the above Examples 1-5 and Comparative Examples 1-5 was tested, and the specific results are shown in Table 1.

[0100] Table 1 Non-isothermal dehydrogenation performance test data of Zr-based MOF hydrogen storage materials prepared under different examples and comparative examples

[0101] Figure 1 It is a bar chart of the dehydrogenation mass ratio of the Zr-based MOF hydrogen storage materials prepared under the conditions of Examples 1-5 and Comparative Examples 1-5. From Figure 1 It can be seen that at a pressure of 20 bar, the dehydrogenation amount of Example 3 is excellent among similar materials, while at a pressure of 50 bar, the dehydrogenation amount is significantly higher than that of other samples. Its dehydrogenation amount under different pressures shows good performance, indicating its high-efficiency hydrogen storage and dehydrogenation ability and the stability of its hydrogen storage performance. In addition, it can be seen from the figure that when the pressure of Example 3 increases from 20 bar to 50 bar, the dehydrogenation amount almost triples, indicating its good responsiveness to pressure changes, enabling it to maintain a high hydrogen storage and dehydrogenation efficiency under different pressure conditions.

[0102] Figure 2 It is an energy spectrum diagram of the Zr-based MOF hydrogen storage materials prepared under the conditions of Example 3. Through energy-dispersive X-ray spectroscopy (EDS), a stoichiometric analysis of Experimental Example 3 was carried out, and clear elemental composition data were obtained. The detected characteristic X-ray spectrum contains four significant energy peaks, among which Zr shows a bimodal characteristic with obvious intensity differences. Through spectral peak area integration and normalization processing, the atomic percentages of C, O, and Zr in the material were calculated to be 48.78%, 34.72%, and 16.49% respectively. This proportional relationship is basically consistent with the theoretical chemical formula of Example 3, indicating that there are few impurities. In addition, it can be seen from the figure that the distribution of the three elements C, O, and Zr in this material is uniform, indicating its excellent structure.

[0103] Figure 3 and Figure 4SEM electron micrographs of the Zr-based MOF hydrogen storage materials prepared under the conditions of Example 3 and Comparative Example 5 respectively. The results show that the particle size distribution of Example 3 is concentrated in the range of 200 nm, presenting a regular octahedral morphology with clear boundaries, which is completely consistent with the description of the typical structure, indicating that the modification process does not damage the overall lattice framework of the material. Further observing the high-resolution SEM image, it can be seen that there is a dense and homogeneous pore structure on the surface of Example 3, and the spatial arrangement of the pores shows a clear periodic law, indicating that it maintains a stable nanostructure and crystal characteristics. While the particle size of Comparative Example 5 is mainly concentrated in the order of 100 nm, presenting a tetrahedral structure. Compared with Example 3, its particle size is too small, which reduces its thermal conductivity, and then leads to a sharp increase in the material temperature during hydrogen absorption and a sharp decrease during hydrogen desorption, slowing down the reaction kinetics and directly affecting the hydrogen absorption and desorption rates. In addition, due to its too small particle size, it is more likely to be further pulverized due to the repeated volume expansion and contraction during the hydrogen absorption and desorption cycles, resulting in agglomeration and deterioration of heat transfer. After long-term cycling, performance degradation is more likely to occur due to increased pulverization, and the cycling stability is poor. In terms of geometric structure, the geometric size of the pores in the octahedral structure of Example 3 is larger, which can accommodate more hydrogen atoms, facilitating the balance of high volumetric hydrogen storage density and gravimetric hydrogen storage capacity. And the geometric symmetry of the octahedral structure is higher, and the diffusion path of hydrogen atoms in it is smoother. In contrast, the close packing of the tetrahedral structure will lead to a higher hydrogen diffusion barrier. Compared with the tetrahedral structure, the octahedral structure can significantly reduce the diffusion activation energy of hydrogen and improve the hydrogen absorption and desorption rates. Finally, the octahedral structure usually has higher symmetry and stronger chemical bonding, which can effectively resist volume expansion and pulverization during the repeated hydrogen absorption and desorption processes, and has both a high specific surface area and structural stability, significantly extending the service life of the hydrogen storage material.

[0104] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a zirconium-based MOFs solid hydrogen storage material, characterized in that, Including: Mix zirconium chloride and fumaric acid and ball-mill them to obtain raw material powder; Dissolve the raw material powder in a mixed solvent of DMF and formic acid, and form a uniform precursor solution through ultrasonic treatment; Heat the precursor solution, carry out reaction crystallization, centrifuge after cooling to obtain a precipitate; Wash the precipitate successively with DMF solution and methanol, dry it, and activate it by vacuum pumping under heating conditions to prepare a zirconium-based MOFs solid hydrogen storage material.

2. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The molar ratio of the zirconium chloride to the fumaric acid is (0.8~1.2):

1.

3. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The ball-milling rotation speed is 300~700 rpm, the ball-to-material ratio is 10:1, and the ball-milling time is 0.5~1.5 h.

4. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The volume ratio of the DMF to the formic acid is (15~25):(5~9).

5. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The mass-volume ratio of the raw material powder to the mixed solvent is (0.93~1.395) g:(20~34) ml.

6. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The ultrasonic treatment time is 30~60 min, and the ultrasonic treatment frequency is 20~30 kHz.

7. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The heating temperature of the precursor solution is 110~150 °C, and the crystallization reaction time is 5~9 h.

8. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, wherein, The washing process includes: First, centrifuge and wash the precipitate 3 times with DMF solution to remove unreacted reagents, and then further centrifuge and wash 3 times with methanol solution to remove the remaining DMF in the precipitate. The centrifugation rate is 3000~4000 rpm.

9. The preparation method of a zirconium-based MOFs solid hydrogen storage material according to claim 1, characterized in that, The drying temperature is 80~120 °C, the drying time is 10~15 h, and the vacuum pumping activation temperature is 130~170 °C.

10. A zirconium-based MOFs solid hydrogen storage material prepared by the preparation method according to any one of claims 1~9.

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