Composite hydrogen storage material and preparation method thereof

Abstract

The invention discloses a composite hydrogen storage material and a preparation method thereof, and belongs to the technical field of hydrogen storage materials and preparation thereof. The invention solves the problems of low adsorption capacity, complex preparation process, poor material stability and the like of the existing MOF material as a hydrogen storage material. The metal organic covalent material (MIL-101 (Cr)) is modified by a post-modification method of an organic ligand (formic acid, acetic acid, glycine or beta-alanine), so that the hydrogen storage capacity of the metal organic covalent material under high pressure is improved, and the modified material not only increases the hydrogen storage capacity under the same condition, but also increases the hydrogen storage capacity under the same condition. And the adsorption heat of hydrogen is also greatly improved, so that the hydrogen adsorption capacity is increased, and a new thought and method are provided for further developing an efficient and safe hydrogen storage material.

Description

Technical Field

[0001] The present invention relates to a composite hydrogen storage material and a preparation method thereof, belonging to the technical field of hydrogen storage materials and preparation methods thereof. Background Art

[0002] Hydrogen, as a clean, efficient, and sustainable secondary energy source, has garnered widespread attention. Its high energy density, renewable nature, and pollution-free combustion products make it an ideal energy carrier. The hydrogen energy industry chain is long and complex, encompassing multiple stages, including hydrogen production, storage, transportation, and refueling. Currently, hydrogen storage and transportation remain a bottleneck hindering the rapid development of the industry.

[0003] Traditional hydrogen storage methods, such as high-pressure gaseous hydrogen storage and low-temperature liquid hydrogen storage, suffer from poor safety, high energy consumption, and high costs. In recent years, solid-state hydrogen storage, including solid hydride hydrogen storage and metal-organic framework (MOF) / covalent organic framework (COF) hydrogen storage, has become a hot topic in hydrogen storage technology research. These methods offer high hydrogen storage density and improved safety. Solid-state hydride hydrogen storage technology reacts hydrogen with a metal or metal alloy under certain conditions to form a solid hydride, which is then released through heating or the action of a catalyst. However, this hydrogen storage method suffers from high energy consumption during hydrogen release and a very short cycle life. MOF / COF hydrogen storage utilizes the porous structure of MOF / COF materials to store hydrogen in their pores through physical adsorption. However, these materials still have limitations in hydrogen storage performance, such as low hydrogen storage capacity, low adsorption heat, and poor cycling stability.

[0004] Current research on metal-organic frameworks (MOFs) as hydrogen storage materials focuses on increasing their surface area or by adding metals like palladium to boost their adsorption heat, thereby increasing their hydrogen adsorption capacity. However, these improvements are limited. Furthermore, the complex process for preparing high-surface-area MOFs and the poor stability of the materials themselves make them difficult to commercialize. Summary of the Invention

[0005] In order to solve the problems of low adsorption capacity, complex preparation process, poor material stability, etc. of existing MOF materials as hydrogen storage materials, the present invention provides a composite hydrogen storage material and a preparation method thereof.

[0006] The technical solution of the present invention: One of the purposes of the present invention is to provide a composite hydrogen storage material, which is MIL-101 (Cr) modified by organic ligands.

[0007] It is further defined that the organic ligand is formic acid, acetic acid, glycine or β-alanine.

[0008] It is further specified that the adsorption capacity of the composite hydrogen storage material reaches 8.54 wt% at 77K and 70 bar.

[0009] The second object of the present invention is to provide a method for preparing the above-mentioned composite hydrogen storage material, which comprises: subjecting a hydrothermal reaction system consisting of MIL-101 (Cr), an organic ligand and water to a hydrothermal reaction to prepare the composite hydrogen storage material.

[0010] It is further defined that the molar ratio of MIL-101(Cr) to the organic ligand is 1:1.2.

[0011] It is further defined that the solid content of the hydrothermal reaction system is 3-8 wt %.

[0012] It is further defined that the solid content of the hydrothermal reaction system is 5.5 wt %.

[0013] It is further defined that the hydrothermal reaction temperature is 130~220℃.

[0014] It is further defined that the hydrothermal reaction temperature is 160~200°C.

[0015] Furthermore, the hydrothermal reaction temperature is 180°C.

[0016] It is further defined that the hydrothermal reaction time is 8 to 24 hours.

[0017] It is further limited that the hydrothermal reaction time is 10~18h.

[0018] It is further limited that the hydrothermal reaction time is 10 h.

[0019] Beneficial effects of the present invention: The present invention modifies a metal-organic covalent material (MIL-101(Cr)) through post-modification with an organic ligand, thereby increasing the metal-organic covalent material's hydrogen storage capacity under high pressure. The modified material not only increases hydrogen storage capacity under the same conditions, but also significantly increases its heat of adsorption for hydrogen, thereby increasing hydrogen adsorption capacity. This provides new ideas and methods for the further development of efficient and safe hydrogen storage materials. Furthermore, the present invention utilizes a simple MOF post-modification preparation method, functionalizing the metal-organic covalent material (MIL-101(Cr)) by selecting a suitable organic ligand modifier. This simple, mature, and stable process, combined with inexpensive and readily available raw materials, offers advantages in practical applications, making it suitable for large-scale industrial production and of great significance for its commercial application, providing more reliable technical support for the storage and utilization of hydrogen energy. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 N2 adsorption-desorption curve of MIL-101 (Cr) at 77K; Figure 2N2 adsorption-desorption curve of the formic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 1 at 77K; Figure 3 This is the N2 adsorption-desorption curve of the acetic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 2 at 77K; Figure 4 N2 adsorption-desorption curve of the glycine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 3 at 77K; Figure 5 N2 adsorption-desorption curve of the β-alanine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 4 at 77K; Figure 6 N2 adsorption-desorption curve of the propionic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Comparative Example 1 at 77K; Figure 7 is the pore size distribution curve of MIL-101 (Cr); Figure 8 This is the pore size distribution curve of the formic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 1; Figure 9 This is the pore size distribution curve of the acetic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 2; Figure 10 This is the pore size distribution curve of the glycine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 3; Figure 11 This is the pore size distribution curve of the β-alanine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 4; Figure 12 This is the pore size distribution curve of the propionic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Comparative Example 1; Figure 13 is the H2 adsorption-desorption curve of MIL-101 (Cr) at 77K; Figure 14 H2 adsorption-desorption curve of the formic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 1 at 77K; Figure 15 This is the H2 adsorption-desorption curve of the acetic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 2 at 77K; Figure 16 H2 adsorption-desorption curve of the glycine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 3 at 77K; Figure 17This is the H2 adsorption-desorption curve of the β-alanine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 4 at 77K; Figure 18 H2 adsorption-desorption curve of the propionic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Comparative Example 1 at 77K; Figure 19 is the charge density difference during the adsorption of H2 by MIL-101(Cr); Figure 20 The charge density difference of the formic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 1 during the adsorption of H2; Figure 21 The charge density difference during the adsorption of H2 by the acetic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Example 2; Figure 22 The charge density difference of the glycine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 3 during the adsorption of H2; Figure 23 The charge density difference of the β-alanine-modified MIL-101 (Cr) hydrogen storage material prepared in Example 4 during the adsorption of H2; Figure 24 The charge density difference of the propionic acid-modified MIL-101 (Cr) hydrogen storage material prepared in Comparative Example 1 during the adsorption of H2. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions 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 intended to limit the present invention.

[0021] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0022] Specifically, MIL-101 (Cr), CAS: 869288-09-5, used in the following examples was purchased from Shanghai Kaisen Biotechnology Co., Ltd.

[0023] Example 1 MIL-101 (Cr) and formic acid with a molar ratio of 1:1.2 were mixed with solvent water to obtain a hydrothermal reaction system with a solid content of 5.5wt%. The hydrothermal reaction system was placed in a reactor and a hydrothermal reaction was carried out at 180°C for 10 hours to obtain a formic acid-modified MIL-101 (Cr) hydrogen storage material.

[0024] Example 2 MIL-101 (Cr) and acetic acid with a molar ratio of 1:1.2 were mixed with solvent water to obtain a hydrothermal reaction system with a solid content of 5.5wt%. The hydrothermal reaction system was placed in a reactor and a hydrothermal reaction was carried out at 180°C for 10 hours to obtain acetic acid-modified MIL-101 (Cr) hydrogen storage material.

[0025] Example 3 MIL-101 (Cr) and glycine in a molar ratio of 1:1.2 were mixed with solvent water to obtain a hydrothermal reaction system with a solid content of 5.5 wt%. The hydrothermal reaction system was placed in a reactor and subjected to a hydrothermal reaction at 180°C for 10 hours to obtain a glycine-modified MIL-101 (Cr) hydrogen storage material.

[0026] Example 4 MIL-101 (Cr) and glycine in a molar ratio of 1:1.2 were mixed with solvent water to obtain a hydrothermal reaction system with a solid content of 5.5 wt%. The hydrothermal reaction system was placed in a reactor and subjected to a hydrothermal reaction at 180°C for 10 h to obtain β-alanine-modified MIL-101 (Cr) hydrogen storage material.

[0027] Comparative Example 1 MIL-101 (Cr) and propionic acid in a molar ratio of 1:1.2 were mixed with solvent water to obtain a hydrothermal reaction system with a solid content of 5.5 wt%. The hydrothermal reaction system was placed in a reactor and subjected to a hydrothermal reaction at 180°C for 10 hours to obtain a propionic acid-modified MIL-101 (Cr) hydrogen storage material.

[0028] Effect Examples (1) The specific surface areas of the modified hydrogen storage materials prepared in Examples 1 to 4 and Comparative Example 1 and the raw material MIL-101 (Cr) for preparing the modified hydrogen storage materials were characterized. Specifically, the N2 adsorption-desorption curves of the modified hydrogen storage materials prepared in Examples 1 to 4 and Comparative Example 1 and the raw material MIL-101 (Cr) for preparing the modified hydrogen storage materials at 77K are shown as follows: Figures 1 to 6 As shown in the figure, the specific surface area of MIL-101 (Cr) is 2876m 2 / g, the specific surface area of MIL-101 (Cr) modified with formic acid is 2957m 2 / g, the specific surface area of acetic acid modified MIL-101 (Cr) is 2780m 2 / g, the specific surface area of MIL-101 (Cr) modified with propionic acid is 2775m 2 / g, the specific surface area of glycine-modified MIL-101 (Cr) is 2701m 2 / g, the specific surface area of β-alanine modified MIL-101 (Cr) is 2441m 2 / g.

[0029] The pore size distribution of the modified hydrogen storage materials prepared in Examples 1 to 4 and Comparative Example 1 and the raw material MIL-101 (Cr) for preparing the modified hydrogen storage materials were further characterized. The results are as follows: Figures 7-12 As shown in the figure, the pore size of MIL-101 (Cr) does not change significantly before and after modification with organic ligands. (2) The hydrogen storage performance of the modified hydrogen storage materials prepared in Examples 1 to 4 and Comparative Example 1 and the raw material MIL-101 (Cr) for preparing the modified hydrogen storage materials were characterized. Specifically, the total adsorption capacity of hydrogen by the above materials under high pressure (0-70 bar) and 77K was as follows: Figures 13 to 18 As shown in the figure, the hydrogen adsorption trends of all materials are similar when the pressure is less than 10 bar, showing a rapid increase. As the pressure increases, the MIL-101(Cr) materials modified with organic ligands such as formic acid, acetic acid, glycine, and β-alanine all exhibit higher hydrogen adsorption than the original unmodified MIL-101(Cr). In particular, using β-alanine as a modifier, the adsorption capacity reaches 8.54wt% at 70 bar, while the total hydrogen adsorption capacity of MIL-101(Cr) is 7.89wt%.

[0030] (3) Density Functional Theory (DFT) calculations were used to show the enhanced hydrogen storage performance mechanism of the modified MIL-101 (Cr). The results showed that when hydrogen approaches the MIL-101 (Cr) framework, it will preferentially adsorb to the F-containing sites on the framework because the strong electronegativity of F makes this site an electron-rich region. In order to further illustrate the interaction between H2 molecules and MIL-101 (Cr) building blocks, the charge density difference (CDD) caused by the H2 adsorption process was calculated. The results are shown in Figure 2. Figures 19 to 24 As shown. Figure 19As shown in the figure, when H2 approaches a F-containing site on unmodified MIL-101(Cr), some of the F's electrons donate to the outer orbital of the hydrogen, forming a region of increased electron density between F and H (the black area in the figure indicates where the electron density increases during adsorption). Furthermore, due to the strong polarization effect of F, the H2 molecule is also partially polarized, with the electron density decreasing at the end closest to F (the white area in the figure indicates where the electron density decreases during adsorption) and increasing at the end farther from F. This polarized H2, with its partial positive charge near the F end, forms a strong intermolecular interaction with the F-containing site.

[0031] Depend on Figures 20-24 As shown, when H2 approaches the modified MIL-101(Cr), its interaction with the F-containing site on the framework (shown in the figure ②) is similar to that of the original, unmodified MIL-101. However, after organic ligand modification, a significant decrease in electron density occurs at the O site (shown in the figure ①) at the center of the MIL-101(Cr) building block during adsorption. CDD calculations indicate that this electron flow partially toward the F-containing site, slowing the decrease in electron density at site ②. To some extent, the electrons donated by the O site enhance the electron density at the F site and its interaction with H2. Consequently, the organic ligand-modified MIL-101(Cr) exhibits a higher heat of hydrogen adsorption and, in experimental tests, a relatively higher hydrogen adsorption capacity. Of course, this ligand modification, which results in the electron-volatile nature of the O site, does not apply to all non-benzoic acid ligands (the original MIL-101 ligand). Calculations found that modification with propionic acid did not enhance electron flow and had a low adsorption heat, which may be related to its long-chain structure and lack of polar groups.

[0032] In summary, the composite hydrogen storage material provided by the present invention, by functionalizing MOF with a suitable modifier, greatly enhances its adsorption heat for hydrogen, thereby increasing the hydrogen adsorption capacity.

[0033] The above description is merely a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A composite hydrogen storage material, characterized in that The composite hydrogen storage material is MIL-101 (Cr) modified by organic ligands.

2. The composite hydrogen storage material according to claim 1, characterized in that The organic ligand is formic acid, acetic acid, glycine or β-alanine.

3. The composite hydrogen storage material according to claim 1, characterized in that The adsorption capacity of the composite hydrogen storage material at 77K and 70bar reaches 8.54wt%.

4. A method for preparing the composite hydrogen storage material according to any one of claims 1 to 3, characterized in that: The product is prepared by subjecting a hydrothermal reaction system consisting of MIL-101 (Cr), an organic ligand and water to a hydrothermal reaction.

5. The preparation method according to claim 4, characterized in that The molar ratio of MIL-101 (Cr) to the organic ligand is 1:1.

2.

6. The preparation method according to claim 4, characterized in that The solid content of the hydrothermal reaction system is 3~8wt%.

7. The preparation method according to claim 4, characterized in that The hydrothermal reaction temperature is 130~220℃.

8. The preparation method according to claim 7, characterized in that The hydrothermal reaction temperature is 160~200℃.

9. The preparation method according to claim 4, characterized in that The hydrothermal reaction time is 8~24h.

10. The preparation method according to claim 9, characterized in that The hydrothermal reaction time is 10~18h.

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