Solid hydrogen storage material of transition metal nickel doped tetra-nitrogen-based organic framework and preparation method of solid hydrogen storage material

Abstract

The invention relates to a solid hydrogen storage material of a transition metal nickel-doped tetrazo organic framework and a preparation method thereof, and the preparation method comprises the following steps: dissolving anhydrous nickel chloride in absolute ethyl alcohol to obtain a nickel ion precursor solution; the preparation method comprises the following steps: mixing N, N-dimethylformamide and absolute ethyl alcohol, adding tetraphenylpyrazine, stirring and dissolving to obtain a uniformly dispersed tetraphenylpyrazine solution; the preparation method comprises the following steps: mixing a nickel ion precursor solution and a tetraphenylpyrazine solution, carrying out ultrasonic treatment at room temperature, continuously stirring at room temperature, and finally heating and stirring to obtain a precursor solution of a nickel-doped tetra-nitrogen-based organic framework; and standing and precipitating the precursor liquid, respectively carrying out centrifugal treatment by using deionized water and absolute ethyl alcohol, and finally, carrying out vacuum drying to obtain the solid hydrogen storage material of the transition metal nickel doped tetra-nitrogen-based organic framework. The solid hydrogen storage material prepared by the invention has the characteristics of high hydrogen storage capacity, good cycle stability and simple operation flow, and is used for a solid hydrogen storage device to realize non-cracking chemical adsorption of hydrogen.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state hydrogen storage, and particularly relates to a preparation method of a solid-state hydrogen storage material of a transition metal nickel-doped tetraazido organic framework. Background Art

[0002] With the increasing global attention to energy sustainable development, hydrogen energy, as a zero-emission, high-energy-density and renewable green energy, is gradually becoming a key direction for global energy transformation. The wide application of hydrogen energy depends on efficient storage technologies, and solid-state hydrogen storage has attracted much attention due to its high hydrogen storage density and good safety.

[0003] Solid-state hydrogen storage materials mainly achieve hydrogen storage through two mechanisms: physical adsorption and chemical adsorption. However, there are still many challenges in the current field of solid-state hydrogen storage materials. Physical adsorption materials, such as activated carbon, zeolite, and porous organic polymers, although having a high surface area, due to the action of van der Waals forces, their hydrogen adsorption strength is weak, and effective hydrogen storage can only be achieved under harsh conditions such as low temperature and high pressure, which may lead to changes in the bulk structure of the material and affect its cycle stability; it also increases the cost of hydrogen storage and limits the wide application of physical adsorption materials in practical applications. Chemical adsorption materials, such as MgH 2 , LiBH 4 , and NaAlH 4 etc., although having a high hydrogen storage mass density, their hydrogen release process usually requires high temperature conditions. High-temperature hydrogen release not only increases energy consumption but also may lead to changes in the bulk structure of the material and affect its cycle stability.

[0004] Therefore, developing a new type of solid-state hydrogen storage material with high hydrogen storage capacity, good cycle stability, and simple operation process has become an urgent need in current research. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a solid-state hydrogen storage material of a transition metal nickel-doped tetraazido organic framework. By developing a transition metal nickel-doped tetraazido organic framework material, the framework forms a COF or MOF solid-state hydrogen storage material with a large specific surface area through unsaturated sites as organic ligand connection sites. This material not only has high hydrogen storage performance and excellent cycle stability, but also the transition metal center sites serve as hydrogen absorption sites, enabling non-cracking chemical adsorption of hydrogen. At the same time, the relatively dense electron cloud formed by the saturated bonds in the framework helps to accelerate the transmission rate of hydrogen to the active center sites.

[0006] The technical solution of the present invention is: A solid hydrogen storage material of transition metal nickel-doped tetraamino organic framework, the solid hydrogen storage material is a transition metal nickel-doped tetraamino pyrazine organic framework material, the nickel content in the solid hydrogen storage material is 1.50 at%, used in solid hydrogen storage devices to achieve non-cracking chemical adsorption of hydrogen.

[0007] A preparation method of a solid hydrogen storage material of transition metal nickel-doped tetraamino organic framework, the specific steps are as follows: S1: Prepare the precursor solution of nickel ions Dissolve anhydrous nickel chloride in absolute ethanol to prepare the precursor solution of nickel ions; S2: Prepare the tetraphenylpyrazine solution Mix N,N-dimethylformamide (DMF) and absolute ethanol according to a volume ratio of 3:1, add tetraphenylpyrazine, and stir evenly to obtain the tetraphenylpyrazine solution; S3: Prepare the precursor liquid of nickel-doped tetraamino organic framework Mix the precursor solution of nickel ions and the tetraphenylpyrazine solution according to a mass ratio of 1:3, treat under ultrasonic conditions at room temperature for 1 h, stir at room temperature for 1 h, and finally heat and stir at 80 °C for 12 h to obtain the precursor liquid of nickel-doped tetraamino organic framework; S4: Prepare the solid hydrogen storage material of transition metal nickel-doped tetraamino organic framework Let the precursor liquid of nickel-doped tetraamino organic framework in S3 stand at room temperature for 8 h, remove the supernatant and retain the precipitate, wash and centrifuge several times alternately with deionized water and absolute ethanol, and dry in vacuum to obtain the solid hydrogen storage material of transition metal nickel-doped tetraamino organic framework.

[0008] Further, in step S2, the mass-volume ratio of tetraphenylpyrazine to N,N-dimethylformamide is 8:1.

[0009] Further, in step S1, the mass-volume ratio of anhydrous nickel chloride to absolute ethanol is 4:1 mg / mL.

[0010] Further, in step S4, when drying in vacuum, the drying temperature is 60 °C and the drying time is 12 h.

[0011] Further, the number of times of washing alternately with deionized water and absolute ethanol is 3 times.

[0012] Further, when washing alternately with deionized water and absolute ethanol, first add deionized water for washing, centrifuge, retain the precipitate, then add absolute ethanol for washing, centrifuge, and retain the precipitate.

[0013] The present invention uses anhydrous nickel chloride as a precursor and tetraphenylpyrazine as the main material. By stirring in a high-temperature environment, nickel ions are coordinated with tetraphenylpyrazine, and through heat treatment, a solid-state hydrogen storage material of transition metal nickel-doped tetraamino organic framework is obtained. Its beneficial effects are as follows: 1) The combination of nickel and the tetraamino organic framework. The electronic structure on the 3d orbit of transition metal nickel Ni has a relatively high surface energy, which can form a stable metal-hydrogen bond with hydrogen molecules, thus significantly improving the hydrogen adsorption performance. Moreover, the relatively low ionization energy and high metal-hydrogen bond affinity of nickel enable nickel to form a strong interaction with hydrogen molecules, promoting hydrogen adsorption. Compared with cobalt and iron doping, nickel has a stronger electron regulation ability, which can provide more electron density during the gas adsorption process, thereby improving the dynamic behavior of hydrogen adsorption and desorption. This electron regulation effect makes the nickel-doped tetraamino organic framework material show more excellent performance in hydrogen storage applications. And tetraphenylpyrazine, as an organic framework, has a more stable structure compared to tetraphenylporphyrin. In the tetraphenylpyrazine molecule, the pyrazine ring has a strong nitrogen-nitrogen coordination ability and can form a more stable coordination structure with transition metal nickel. This stability enables tetraphenylpyrazine to maintain a high chemical stability when constructing the organic framework, thereby providing a stronger hydrogen adsorption ability for solid-state hydrogen storage devices and realizing non-cracking chemical adsorption of hydrogen.

[0014] 2) From the perspective of the preparation process, the simplified preparation process not only reduces the complexity of operation and safety risks but also selects raw materials that are easy to obtain. Compared with the traditional process using tetraphenylporphyrin as a transition metal ion-doped framework, this method reduces the complex and potentially dangerous experimental step of condensation reflux under nitrogen. Through simple coordination, centrifugation, and heat treatment processes, the synthesis of an efficient hydrogen storage material can be achieved, making it a more suitable industrial production route with strong practical application potential.

[0015] 3) Good cycle stability: After the material is degassed at 120 °C and then subjected to hydrogen absorption and desorption tests, and at the same time, after hydrogen absorption under a hydrogen pressure environment of 50 bar, no structural damage or performance degradation occurs, demonstrating durability and recyclability.

[0016] 4) Appropriate hydrogen desorption temperature: The material can desorb hydrogen at room temperature. Description of the Drawings

[0017] Figure 1 is a scanning transmission electron microscope (STEM) image of the transition metal nickel-doped tetraamino organic framework material of the present invention (corresponding to Example 1) at 5 μm and 10 nm resolutions; Figure 2 is a scanning transmission electron microscope (STEM) image of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 1) at 500 nm and 10 nm resolutions; Figure 3 It is the scanning transmission electron microscope (STEM) image of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 2) at 1 μm and 10 nm resolutions; Figure 4 It is the scanning transmission electron microscope (STEM) image of the transition metal iron-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 4) at 1 μm and 10 nm resolutions; Figure 5 It is the energy-dispersive X-ray spectroscopy (EDS) image of the transition metal nickel-doped tetraamino organic framework material of the present invention (corresponding to Example 1); Figure 6 It is the energy-dispersive X-ray spectroscopy (EDS) image of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 1); Figure 7 It is the energy-dispersive X-ray spectroscopy (EDS) image of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 2); Figure 8 It is the energy-dispersive X-ray spectroscopy (EDS) image of the transition metal iron-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 4); Figure 9 It is the scanning electron microscope (SEM) image of the transition metal nickel-doped tetraamino organic framework material of the present invention (corresponding to Example 1) at 20 μm resolution; Figure 10 It is the scanning electron microscope (SEM) image of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 1) at 10 μm resolution; Figure 11 It is the scanning electron microscope (SEM) image of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 2) at 5 μm resolution; Figure 12 It is the scanning electron microscope (SEM) image of the transition metal iron-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 4) at 10 μm resolution; Figure 13 It is the high-resolution X-ray photoelectron spectroscopy image (a) of the transition metal nickel-doped tetraamino organic framework material of the present invention (corresponding to Example 1) and the high-resolution X-ray sub-spectroscopy images (b), (c), (d) of C1s, N 1s, and Ni 2p; Figure 14 It is the high-resolution X-ray photoelectron spectroscopy image (a) of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 1) and the high-resolution X-ray sub-spectroscopy images (b), (c), (d) of C1s, N 1s, and Ni 2p; Figure 15 are the high-resolution X-ray photoelectron spectroscopy (a) of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 2) and the high-resolution X-ray sub-spectroscopy of C1s, N 1s, and Ni 2p (b), (c), (d); Figure 16 are the high-resolution X-ray photoelectron spectroscopy (a) of the transition metal iron-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 4) and the high-resolution X-ray sub-spectroscopy of C1s, N 1s, and Ni 2p (b), (c), (d); Figure 17 is the nitrogen adsorption-desorption isotherm curve of the transition metal nickel-doped tetraamino organic framework material of the present invention (corresponding to Example 1) at liquid nitrogen temperature; Figure 18 is the nitrogen adsorption-desorption isotherm curve of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 1) at liquid nitrogen temperature; Figure 19 is the nitrogen adsorption-desorption isotherm curve of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 2) at liquid nitrogen temperature; Figure 20 is the nitrogen adsorption-desorption isotherm curve of the transition metal iron-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 4) at liquid nitrogen temperature; Figure 21 is the hydrogen adsorption-desorption isotherm curve of the transition metal nickel-doped tetraamino organic framework material of the present invention (corresponding to Example 1) at liquid nitrogen temperature; Figure 22 is the hydrogen adsorption-desorption isotherm curve of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 1) at liquid nitrogen temperature; Figure 23 is the hydrogen adsorption-desorption isotherm curve of the transition metal cobalt-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 2) at liquid nitrogen temperature; Figure 24 is the hydrogen adsorption-desorption isotherm curve of the transition metal iron-doped tetraamino organic framework material of the present invention (corresponding to Comparative Example 4) at liquid nitrogen temperature. Detailed Embodiments

[0018] The tetraphenylpyrazine powder used in Example 1, Comparative Example 1, and Comparative Example 4 of the present invention is the same batch of tetraphenylpyrazine; the tetraamino organic framework crystals prepared in Comparative Example 2 and Comparative Example 3 are prepared in the same batch.

[0019] Example 1 S1: Prepare the precursor solution of nickel ions Dissolve 40 mg of anhydrous nickel chloride in 10 mL of anhydrous ethanol, and stir at room temperature until completely dissolved to obtain a precursor solution of nickel ions; S2: Prepare a solution of tetraphenylpyrazine Mix 15 mL of N,N-dimethylformamide (DMF) and 5 mL of anhydrous ethanol, stir evenly, and then add 120 mg of tetraphenylpyrazine, and stir until the tetraphenylpyrazine is completely dissolved to obtain a solution of tetraphenylpyrazine; S3: Prepare a precursor solution of nickel-doped tetraamino organic framework Mix all the precursor solution of nickel ions prepared in S1 and the solution of tetraphenylpyrazine prepared in S2 together, ultrasonicate for 1 h, stir at room temperature for 1 h, and then heat and stir at 80 °C for 12 h to obtain a precursor solution of nickel-doped tetraamino organic framework; S4: Prepare a solid hydrogen storage material of transition metal nickel-doped tetraamino organic framework Let the precursor solution in S3 stand and precipitate at room temperature for 8 h, remove the supernatant and retain the precipitate. First, add deionized water for washing, centrifuge, retain the precipitate, then add anhydrous ethanol for washing, centrifuge, retain the precipitate, repeat the above alternating washing with deionized water and anhydrous ethanol and centrifuge 3 times, and then dry in a vacuum oven at 60 °C for 12 h, and cool to room temperature to obtain a solid hydrogen storage material of transition metal nickel-doped tetraamino organic framework. In the structural characterization of the nickel-doped tetraamino organic framework material prepared in Example 1, the scanning transmission electron microscope (STEM) energy spectrum and its element distribution map are as Figure 1 shown. Figure a) shows that the material has a regular block morphology, and Figure b) shows a regular lattice and a pore structure with a deeper contrast, providing abundant sites for hydrogen storage. In Figure 5 the energy-dispersive X-ray spectroscopy (EDS) map, the presence of (a) C, (b) N, and (c) Ni elements, and their uniform distribution are clearly shown, proving that this preparation method has successfully doped nickel into the organic framework material. The scanning electron microscope image at a magnification of 20 μm is as Figure 9 shown. The material mainly presents a regular block structure, which is beneficial to increasing the transmission rate of hydrogen on the material. At the same time, the surface of the material is smooth, and the pore structure of the framework part is filled or covered by transition metal nickel; at the same time, a small amount of precursors that did not participate in the doping reaction and showed an irregular morphology appear near the regular block structure. The high-resolution X-ray photoelectron spectrum of nickel-doped tetraamino organic framework Figure 13 (a) shows that nickel has been successfully doped into the tetraamino organic framework, and the relative content of Ni is 1.5 at%; Figure 13(b) is the high-resolution spectrum of C1s. Multiple peaks in the spectrum represent different carbon environments. For example, the peaks of C-C / C-N and C-O-C correspond to the chemical bonding of carbon with carbon, nitrogen, and oxygen respectively. Through these peaks, the C-N bonds in the organic part of the material can be inferred; Figure 13 (c) is the high-resolution spectrum of N1s. Multiple peaks can be seen, including Oxidized N, Pyridinic N, Pyrrolic N, and Ni-N, etc. This spectrum reveals the different chemical states of nitrogen in the tetraphenylpyrazine structure. Especially the Ni-N peak of the coordination of nickel and nitrogen indicates that a coordination bond is formed between nickel and tetraphenylpyrazine; Figure 13 (d) is the high-resolution spectrum of Ni 2p. Two main peaks of nickel are shown: Ni 2p 3 / 2 and Ni 2p 1 / 2; In addition, the coordination peak Ni-N and satellite peak Sat. of nickel and nitrogen can also be seen. The shapes and positions of these peaks indicate the oxidation state of nickel and the binding mode with nitrogen. Especially the appearance of the Ni-N peak indicates the coordination of nickel with tetraphenylpyrazine. The nitrogen adsorption and desorption amounts are as Figure 17 shown, Figure 17 (a) It can be obtained that the specific surface area of this material is 9.2028 m 2 g -1 , and the specific surface area < 10 m 2 g -1 . This can be attributed to the fact that transition metal ions may form a relatively tight coordination structure, inhibiting the generation of pores or the opening of larger pores. Therefore, the specific surface area is relatively small; Figure 17 (b) indicates that the pore size distribution of this material is mainly mesoporous.

[0020] In the hydrogen storage performance test of the nickel-doped tetraamino organic framework material obtained in Example 1, after the material is degassed at 120 °C, the hydrogen absorption and desorption tests are carried out. The material does not show structural damage or performance decline, demonstrating durability and recyclability. The hydrogen adsorption-desorption isotherm curve at liquid nitrogen temperature is as Figure 21 shown. The material can release hydrogen at room temperature; when the hydrogen pressure is 50 bar, its hydrogen absorption and desorption amount reaches 0.2568 wt%. At the same time, the absorption and desorption curves basically coincide, which not only shows the excellent hydrogen desorption and desorption ability of the material prepared by the present invention, but also shows that when hydrogen is adsorbed at a pressure environment of 50 bar, the structure of the material does not break due to the high-pressure environment. At the same time, this hydrogen absorption curve has no plateau and shows a linear growth trend, indicating that this material has the potential to adsorb more hydrogen under greater pressure.

[0021] Comparative Example 1 Cobalt-doped tetraamino organic framework material Replace 40 mg of anhydrous nickel chloride in step S1 of Example 1 with 80 mg of anhydrous cobalt chloride, and the other steps are the same as in Example 1.

[0022] In the structural characterization of the cobalt-doped tetraamino organic framework material prepared in Comparative Example 1, the scanning transmission electron microscope (STEM) energy spectrum and its elemental distribution map are as Figure 2 shown. Figure a) shows that there are a large number of pore structures on the surface of the material where the contrast is deeper, providing rich sites for hydrogen storage. Figure b) shows that the material has a regular and ordered lattice; in Figure 6 the energy-dispersive X-ray spectroscopy (EDS) map, the presence of (a) C, (b) N, and (c) Co elements, and their uniform distribution are clearly shown, proving that this preparation method has successfully doped cobalt into the organic framework material; the scanning electron microscope image at a magnification of 10 μm is as Figure 10 shown. The material grows regularly and orderly, mainly presenting a needle-like structure, which is beneficial to increasing the hydrogen transmission rate on the material; it can be seen from the high-resolution X-ray photoelectron spectrum Figure 14 (a) of the cobalt-doped tetraamino organic framework that cobalt has been successfully doped into the tetraamino organic framework, and the relative content of Co is 2.95 at%. Figure 14 (b) is the high-resolution spectrum of C1s. The multiple peaks in the spectrum represent different carbon environments. For example, the peaks of C-C / C-N and C-O-C correspond to the chemical bonds of carbon with carbon, nitrogen, and oxygen respectively. Through these peaks, the C-N bond in the organic part of the material can be inferred. Figure 14 (c) is the high-resolution spectrum of N1s. It can be seen that four different peaks appear at 398.6, 399.3, 400.2, and 402.2 eV, corresponding to the chemical environments of pyridine nitrogen, nitrogen-metal bond, pyrrole nitrogen, and nitrogen oxide respectively. Among them, the coordination peak Co-N of cobalt and nitrogen indicates that a coordination bond is formed between cobalt and tetraphenylpyrazine. In the Co 2p spectrum Figure 14 (d), the deconvoluted peaks at 795.4 and 780.7 eV are attributed to Co 2+ ionic state, indicating that N-coordination guides the formation of the main oxidation state of Co single atoms. In addition, obvious Shake-up satellite peaks (labeled as sat.) are also observed at 783.3 and 797.4 eV; the nitrogen adsorption and desorption amounts are as Figure 18 shown. Figure 17 (a) It can be obtained that the specific surface area of this material is 2.3409 m 2 g -1 , Figure 17 (b) shows that the pore size distribution of this material is mainly mesoporous.

[0023] In Comparative Example 1, the hydrogen storage performance of the obtained cobalt-doped tetraamino organic framework material was tested for hydrogen adsorption at liquid nitrogen temperature and hydrogen desorption isotherm at room temperature. The experimental results are as Figure 22 shown. The hydrogen adsorption-desorption amount reached 0.1191 wt% under a hydrogen pressure of 50 bar. The adsorption-desorption curves basically coincided, indicating that the material has good hydrogen desorption and adsorption capabilities. It is worth noting that there is no plateau in the hydrogen adsorption curve, showing a growth trend linearly related to the pressure, suggesting that the material still has the potential to adsorb more hydrogen at higher pressures. However, compared with the nickel-doped organic framework material in Example 1, the hydrogen storage performance of this material is less than 1 / 2 of that in Example 1. This difference further emphasizes the significant impact of nickel doping on the hydrogen storage performance of the organic framework material in the present invention. As a transition metal, nickel has a unique electronic structure and strong metal-hydrogen bond interaction, significantly improving the hydrogen adsorption capacity. Therefore, the doping of nickel element in this material obviously plays a crucial role in its hydrogen storage performance, highlighting the unique advantages of nickel-doped organic framework materials in the field of hydrogen storage.

[0024] Comparative Example 2 Cobalt-doped tetraamino organic framework materials with different preparation methods S1: Preparation of tetraamino organic framework Add 100 mL of propionic acid and 9.08 g of benzaldehyde C 6 H 5 CHO into a three-necked flask, deoxygenate, heat to 141 °C, and gradually add 6.0 g of pyrrole dropwise using a constant pressure dropping funnel; reflux for 6 h under nitrogen protection, and set the reflux temperature to 141 °C; introduce air into the reaction system for 5 minutes, stop heating and stirring, cool to room temperature, let stand overnight, then filter, wash the solid with methanol to obtain purple crystals; S2: Preparation of the precipitate of cobalt-doped tetraamino organic framework Weigh 0.854 g of the purple crystals obtained in S1 and 3.1 g of cobalt chloride hexahydrate and dissolve them in 100 mL of DMF, reflux for 8 h, cool to room temperature, add 200 mL of deionized water, filter the generated precipitate, wash it twice with 50 mL of deionized water, and then wash it three times with methanol to obtain the precipitate of cobalt-doped tetraamino organic framework; S3: Preparation of the solid hydrogen storage material of transition metal cobalt-doped tetraamino organic framework Dry the precipitate obtained in S2 in a vacuum oven at 60 °C, and then cool to room temperature to obtain the solid hydrogen storage material of transition metal cobalt-doped tetraamino organic framework.

[0025] In the structural characterization of the cobalt-doped tetraamino organic framework material prepared in Comparative Example 2, the scanning transmission electron microscope (STEM) energy spectrum and its element distribution map are as Figure 3As shown, Figure a) shows that the material has a regular blocky morphology. In Figure b), no obvious regular lattice fringes are seen, but there are pore structures and the boundary of the regular crystal structure; Figure 7 In the energy-dispersive X-ray spectroscopy (EDS) pattern, the presence of elements (a) C, (b) N, and (c) Co, and their uniform distribution are clearly shown, proving that this preparation method has successfully doped cobalt into the organic framework material; The scanning electron microscopy image at a magnification of 5 μm is as Figure 11 shown. The material mainly presents an irregular blocky structure. It can be seen that near the blocky structure, there are precursors that did not participate in the doping reaction and show an irregular morphology; The high-resolution X-ray photoelectron spectroscopy of cobalt-doped tetraazido organic framework can be seen Figure 15 in (a), indicating that cobalt has been successfully doped into the tetraazido organic framework, and the relative content of Co is 0.25 at%. Figure 15 (b) is the high-resolution spectrum of Co 2p. It shows two main peaks of Co: Co2p3 / 2 and Co2p1 / 2; The nitrogen adsorption and desorption amounts are as Figure 19 shown, Figure 19 (a) It can be obtained that the specific surface area of this material is 2.3236 m 2 g -1 , Figure 19 (b) indicates that the pore size distribution of this material is mainly mesoporous.

[0026] In the hydrogen storage performance test of the cobalt-doped tetraazido organic framework material obtained in Comparative Example 2, the hydrogen adsorption-desorption isotherm curve at liquid nitrogen temperature is as Figure 21 shown. When the hydrogen pressure is 50 bar, its hydrogen adsorption and desorption amount is only 0.0893 wt%. Nevertheless, the adsorption-desorption curves almost completely overlap, indicating that this material has good hydrogen desorption and desorption capabilities. At the same time, the hydrogen adsorption curve has no plateau, meaning that this material still has great hydrogen adsorption potential at higher pressures. However, compared with the tetraazido organic framework material formed by tetraphenylpyrazine coordination in Comparative Example 1, the hydrogen storage performance of the tetraazido organic framework formed by tetraphenylporphyrin in this comparative example is significantly lower. This phenomenon further confirms the unique advantage of tetraphenylpyrazine in the field of hydrogen storage. As a tetraazido ligand, tetraphenylpyrazine can improve the hydrogen adsorption capacity through stronger metal-nitrogen coordination, which makes it show more excellent performance in hydrogen storage.

[0027] Comparative Example 3 Nickel-doped tetraazido organic framework materials with different preparation methods In S2, 3.1 g of cobalt chloride hexahydrate was replaced with 3.1 g of nickel chloride hexahydrate NiCl 2 ·6H 2 O. Other steps are the same as in Comparative Example 2.

[0028] In the hydrogen adsorption test of the nickel-doped tetraamino organic framework material prepared in Comparative Example 3 at liquid nitrogen temperature and desorption at room temperature, when the hydrogen pressure is 50 bar, the hydrogen adsorption and desorption amount is 0.91 wt%. Compared with the tetraamino organic framework material formed by coordination with tetraphenylpyrazine in Example 1, the hydrogen storage performance of the tetraamino organic framework formed by tetraphenylporphyrin in this example is significantly lower. This phenomenon further confirms the unique advantage of tetraphenylpyrazine in the field of hydrogen storage.

[0029] Comparative Example 4 Iron-doped tetraamino organic framework material Replace 40 mg of anhydrous nickel chloride in step S1 of Example 1 with 40 mg of anhydrous ferrous chloride, and the other steps are the same as in Example 1.

[0030] In the structural characterization of the iron-doped tetraamino organic framework material prepared in Example 1, the scanning transmission electron microscope (STEM) energy spectrum and its elemental distribution map are as Figure 4 shown. Figure a) shows that the material has a regular blocky morphology. In Figure b), no obvious regular lattice fringes are seen, but there is a boundary line between the pore structure and the regular crystal structure; in Figure 5 the energy-dispersive X-ray spectroscopy (EDS) map, the presence of (a) C, (b) N, and (c) Fe elements and their uniform distribution are clearly shown, proving that this preparation method has successfully doped iron into the organic framework material; the scanning electron microscope image at a magnification of 10 μm is as Figure 12 shown. The material mainly presents a regular blocky structure, which is beneficial to increasing the hydrogen transmission rate on the material. At the same time, the surface of the material is smooth, and the pore structure of the framework part is filled or covered by the transition metal iron. At the same time, precursors that did not participate in the doping reaction and show an irregular morphology appear near the regular blocky structure; the high-resolution X-ray photoelectron spectrum of the iron-doped tetraamino organic framework can be seen Figure 16 (a) shows that iron has been successfully doped into the tetraamino organic framework, and the relative content of Fe is 0.16 at%. Figure 16 (b) is the high-resolution spectrum of C1s. The multiple peaks in the spectrum represent different carbon environments. For example, the peaks of C-C / C-N and C-O-C correspond to the chemical bonds of carbon with carbon, nitrogen, and oxygen respectively. The C-N bond in the organic part of the material can be inferred from these peaks. Figure 16 (c) is the high-resolution spectrum of N1s. It can be seen that four different peaks appear at 398.6, 399.3, 400.2, and 402.2 eV, corresponding to the chemical environments of pyridine nitrogen, nitrogen-metal bond, pyrrole nitrogen, and nitrogen oxide respectively. Among them, the coordination peak Fe-N of iron and nitrogen indicates that a coordination bond is formed between iron and tetraphenylpyrazine. Figure 16(d) is the high-resolution spectrum of Fe 2p, showing two main peaks of iron: Fe 2p 3 / 2 and Fe 2p 1 / 2. In addition, the coordination peak of iron and nitrogen, Fe 2+ and the iron ions in the oxidized state, Fe 3+ are also visible, indicating the coordination of iron with tetraphenylpyrazine; the nitrogen adsorption and desorption amounts are as Figure 20 shown Figure 20 (a) It can be concluded that the specific surface area of this material is 4.5669 m 2 g -1 . Figure 20 (b) indicates that the pore size distribution of this material is mainly mesoporous

[0031] In the hydrogen storage performance test of the iron-doped tetraamino organic framework material obtained in Comparative Example 4, the hydrogen adsorption-desorption isotherm curve at liquid nitrogen temperature is as Figure 24 shown. When the hydrogen pressure is 50 bar, the hydrogen adsorption and desorption amount reaches 0.1092 wt%. At the same time, the adsorption and desorption curves basically coincide, indicating the excellent hydrogen desorption and desorption capabilities of the material prepared by the present invention. At the same time, the hydrogen adsorption curve has no plateau and shows a linear growth trend, indicating that this material has the potential to adsorb more hydrogen under greater pressure. However, compared with the nickel-doped organic framework material in Example 1, the hydrogen storage performance of this material is the same as that of cobalt doping and less than 1 / 2 of that in Example 1. This difference further emphasizes the significant influence of nickel doping on the hydrogen storage performance of organic framework materials. As a transition metal, nickel has a unique electronic structure and strong metal-hydrogen bond interaction, which significantly improves the hydrogen adsorption capacity. Therefore, the doping of nickel element in this material obviously plays a crucial role in its hydrogen storage performance, highlighting the unique advantages of nickel-doped organic framework materials in the field of hydrogen storage

[0032] I. Performance analysis of Example 1 of the present invention and its parallel test Comparative Examples 1-4. In Comparative Examples 2 and 3, tetraphenylporphyrin is used as the tetraamino organic framework, and its hydrogen absorption effect is worse than that in Example 1, indicating that tetraphenylpyrazine as an organic ligand has a better effect in hydrogen storage materials. At the same time, the combination of tetraphenylpyrazine and nickel doping is the key to achieving excellent hydrogen storage performance. The framework formed by tetraphenylpyrazine provides a stable matrix for the doping of nickel, while the metal-hydrogen bond interaction of nickel further enhances the hydrogen storage capacity of the material. In Comparative Examples 1 and 4, cobalt doping and iron doping organic frameworks are used respectively, and the hydrogen absorption amount in their hydrogen storage performance tests is less than 1 / 2 of that of nickel doping, further indicating that the role of nickel doping in tetraamino organic framework materials cannot be ignored. The nickel doping in Example 1 shows a relatively high hydrogen adsorption amount, reaching 0.2568 wt%, far exceeding the cobalt- and iron-doped materials in Comparative Examples 1 and 4. Further highlighting the large hydrogen adsorption potential of the nickel-doped tetraamino organic ligand framework material

[0033] II. Effect Analysis of Transition Metal Nickel-Doped Tetraamino Metal-Organic Framework in Embodiment 1 of the Present Invention Through the structural characterization and performance testing of the transition metal nickel-doped tetraamino metal-organic framework material prepared in Embodiment 1, some important conclusions are obtained. According to the STEM image analysis, the material presents a regular lattice structure, and obvious pore structures are shown in the regions with deeper contrast, which provides abundant adsorption sites for hydrogen storage and significantly improves the hydrogen storage capacity. The SEM image shows that the material mainly presents a regular block structure, and this structure helps to improve the transmission rate of hydrogen in the material. Through the EDS energy spectrum and its element distribution map, the uniform distribution of C, N, and Ni elements in the material can be further confirmed, indicating that nickel is successfully doped into the metal-organic framework. The XPS test results further verify the doping situation of nickel. Specifically, the high-resolution spectrum of Ni 2p shows two main peaks of nickel: Ni 2p 3 / 2 and Ni 2p 1 / 2. In addition, the coordination peak Ni-N and satellite peaks of nickel and nitrogen are also observed. The shapes and positions of these peaks indicate the oxidation state of nickel and its binding mode with nitrogen atoms. According to the XPS analysis, the doping content of nickel is 1.5 at%. In the nitrogen adsorption-desorption test, the specific surface area of this material is 9.2028 m 2 / g, showing a relatively high porosity. The hydrogen adsorption-desorption performance test shows that at the liquid nitrogen temperature, when the hydrogen pressure reaches 50 bar, the hydrogen adsorption-desorption amount of the material is 0.2568 wt%. During dehydrogenation at room temperature, the adsorption and dehydrogenation amounts are the same, and the adsorption and dehydrogenation curves basically overlap. Combining the nitrogen adsorption-desorption test results and the hydrogen adsorption-desorption curve, it can be concluded that this material has high-efficient hydrogen adsorption ability, and the hydrogen adsorption amount of the nickel center active sites is relatively high. At the same time, this material also shows the hydrogen desorption ability and cycle stability at room temperature, and has the potential to adsorb more hydrogen at higher pressures, indicating that it has great prospects in hydrogen storage applications.

Claims

1. A solid hydrogen storage material of a transition metal nickel-doped tetranitrogen-based organic framework, characterized in that: The solid-state hydrogen storage material is a transition metal nickel-doped tetrazopyrazine organic framework material, in which the nickel content is 1.50 at %, and is used in a solid-state hydrogen storage device to achieve non-cracking chemical adsorption of hydrogen.

2. A method for preparing a solid hydrogen storage material of a transition metal nickel-doped tetranitrogen-based organic framework as claimed in claim 1, characterized in that: The specific steps are as follows: S1: Preparation of nickel ion precursor solution Dissolving anhydrous nickel chloride in anhydrous ethanol to prepare a nickel ion precursor solution; S2: Preparation of tetraphenylpyrazine solution N,N-dimethylformamide (DMF) and anhydrous ethanol are mixed in a volume ratio of 3:1, tetraphenylpyrazine is added, and the mixture is stirred to obtain a tetraphenylpyrazine solution; S3: Preparation of precursor solution for nickel-doped tetranitrogen-based organic frameworks The nickel ion precursor solution and the tetraphenylpyrazine solution were mixed in a mass ratio of 1:3, treated under ultrasonic conditions at room temperature for 1 hour, stirred at room temperature for 1 hour, and finally heated and stirred at 80° C. for 12 hours to obtain a precursor solution of a nickel-doped tetranitrogen-based organic framework; S4: Preparation of transition metal nickel-doped tetranitrogen-based organic frameworks for solid-state hydrogen storage The precursor liquid of the nickel-doped tetranitrogen-based organic framework in S3 was allowed to stand at room temperature for 8 hours, the supernatant was removed and the precipitate was retained, which was washed alternately with deionized water and anhydrous ethanol and centrifuged several times, and vacuum dried to obtain a solid-state hydrogen storage material of the transition metal nickel-doped tetranitrogen-based organic framework.

3. The method for preparing the solid hydrogen storage material of transition metal nickel doped tetranitrogen-based organic framework according to claim 1, characterized in that: In step S2, the mass volume ratio of tetraphenylpyrazine to N,N-dimethylformamide is 8:

1.

4. The method for preparing a solid hydrogen storage material of a transition metal nickel-doped tetranitrogen-based organic framework according to claim 1, characterized in that: In step S1, the mass volume ratio of anhydrous nickel chloride to anhydrous ethanol is 4:1 mg / mL.

5. The method for preparing the solid hydrogen storage material of transition metal nickel doped tetranitrogen-based organic framework according to claim 1, characterized in that: In step S4, during vacuum drying, the drying temperature is 60° C. and the drying time is 12 h.

6. The method for preparing a solid hydrogen storage material of a transition metal nickel-doped tetranitrogen-based organic framework according to claim 1, characterized in that: The number of alternating washings with deionized water and anhydrous ethanol was 3 times.

7. The method for preparing the solid hydrogen storage material of transition metal nickel doped tetranitrogen-based organic framework according to claim 6, characterized in that: When washing with deionized water and anhydrous ethanol alternately, first add deionized water for washing, centrifuge, retain the precipitate, then add anhydrous ethanol for washing, centrifuge, and retain the precipitate.

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