Mesoporous asymmetric single-atom catalysts, methods of making and using the same
By constructing mesopores in one step through the pyrolytic etching framework of oxygen-containing functional groups, the complexity of traditional carbon-based single-atom catalyst preparation and the challenge of mesopore construction have been solved, enabling the simple and efficient preparation and application of high-performance asymmetric SACs, which exhibit excellent catalytic performance, especially in zinc-iodine batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DONGHUA UNIV
- Filing Date
- 2026-05-13
- Publication Date
- 2026-07-24
AI Technical Summary
Traditional carbon-based single-atom catalysts are complex to prepare and costly, making it difficult to achieve the industrial application of high-performance asymmetric SACs. Furthermore, existing mesoporous construction processes are cumbersome and make it difficult to achieve precise control of the mesoporous structure.
The framework is etched by thermally releasing gas from oxygen-containing functional groups. Mesopores and asymmetric coordination environments are constructed in one step through a ligand ablation strategy, simplifying the process and realizing the integrated design of mesopore structure and electronic structure.
A simple and efficient preparation of mesoporous carbon-supported asymmetric single-atom catalysts has been achieved, which are suitable for zinc-iodine battery cathode materials, improving catalytic activity and stability while reducing production costs.
Smart Images
Figure CN122441471A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of new materials technology, specifically relating to a mesoporous asymmetric single-atom catalyst and its preparation method, which is a mesoporous carbon-supported single-atom catalyst material based on a ligand ablation strategy, its preparation method, and its application. Background Technology
[0002] Carbon-based single-atom catalysts (SACs) have attracted widespread attention in various catalysis and energy conversion fields due to their extreme atomic utilization and unique electronic structure. However, traditional carbon-based single-atom centers typically exhibit highly symmetrical coordination configurations (such as the symmetrical M-N4 structure derived from the pyrolysis of ZIF-8). This symmetry often results in a linear proportional relationship between the adsorption energy of the active center and the intermediate, greatly limiting further breakthroughs in catalytic kinetics. In recent years, by breaking spatial or chemical symmetries to construct "asymmetric SACs," the electronic state density distribution of the metal center can be effectively reshaped and the reaction energy barrier optimized, demonstrating great potential for improving intrinsic catalytic activity.
[0003] However, the preparation of high-performance asymmetric SACs often faces a trade-off between process complexity and structural controllability. Currently, the academic community generally adopts the method of pre-synthesized complexes undergoing pyrolysis coordination and post-pyrolysis treatment to add heteroatoms. Although this method can achieve precise control of the coordination structure, it still has significant drawbacks: complex complex preparation is complex and costly; post-pyrolysis treatment is limited by lengthy processes and difficulty in covering modification sites. These bottlenecks result in high production costs and lengthy production cycles for asymmetric SACs, severely restricting their industrial application.
[0004] Therefore, seeking a template-free, green, and simple construction strategy for asymmetric SACs has become a research focus in the field of carbon-based single-atom materials. During the thermal treatment of carbon precursors, the evolution of molecular structure is often accompanied by the release of gaseous products. Based on this, developing a novel process for generating mesopores through directional ablation of oxygen-containing functional groups, utilizing the pyrolysis behavior of the precursor's own functional groups within a specific temperature range to construct pores in situ, is expected to break the limitations of traditional multi-step methods. This method not only simplifies the process flow but also allows for precise intervention in the mesoporous structure by controlling the type and distribution of functional groups, providing a highly competitive technical solution for the large-scale preparation of high-performance carbon-based asymmetric SACs materials. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides a mesoporous asymmetric single-atom catalyst, its preparation method, and its applications. Mesopores are generated in one step by thermally decomposing oxygen-containing functional groups and releasing gases to etch the framework. This mechanism not only achieves the synergistic construction of mesopores and asymmetric coordination environments but also provides a new pathway for the integrated design of the pore and electronic structures of single-atom catalysts. The method offers advantages such as simple process, good reproducibility, and adjustable particle morphology, mesopore size, and porosity, making it suitable for the construction of cathode materials for zinc-iodine batteries.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a mesoporous asymmetric single-atom catalyst involves dissolving and mixing a zinc salt, an organic ligand with oxygen-containing functional groups, and an acetylacetone metal salt to obtain an oxygen-containing functional group ZIFs material. The oxygen-containing functional group ZIFs powder is then subjected to high-temperature pyrolysis to obtain a mesoporous carbon-supported asymmetric single-atom catalyst.
[0007] The preparation method described above, the steps for preparing oxygen-functionalized ZIFs materials are as follows: S1. Dissolve the organic ligand in a mixed organic solvent to obtain solution A, and prepare an aqueous solution of zinc salt and a solution of acetylacetone metal salt or a mixed solution of zinc salt and acetylacetone metal salt; S2. When solution A is stirred, zinc salt solution and acetylacetone metal salt solution or a mixed solution of zinc salt and acetylacetone metal salt are added dropwise. The reaction is stirred and then centrifuged and washed after the reaction is completed to obtain oxygen-containing functional group ZIFs powder.
[0008] In the preparation method described above, in step S1, the mixed organic solvent is a mixture of two or more of N,N-dimethylformamide, methanol, dimethyl sulfoxide, n-butanol, dioxane, and acetonitrile. The solvent used in the mixed solution of zinc salt and acetylacetone metal salt is the above-mentioned mixed organic solvent. The solvent in the acetylacetone metal salt solution is selected from one of N,N-dimethylformamide, methanol, dimethyl sulfoxide, n-butanol, dioxane, and acetonitrile.
[0009] The preparation method described above, another step for preparing oxygen-functionalized ZIFs materials is as follows: Zinc salt, organic ligand, and acetylacetone metal salt were dissolved in an organic solvent, and the mixture was allowed to stand and heated to react. After the reaction was completed, the mixture was centrifuged and washed to obtain oxygen-containing functional group ZIF powder.
[0010] In the preparation method described above, the organic solvent for preparing the oxygen-containing functional group ZIFs material is selected from one or more of N,N-dimethylformamide, methanol, dimethyl sulfoxide, n-butanol, dioxane, and acetonitrile.
[0011] In the preparation method described above, the zinc salt is selected from zinc nitrate hexahydrate and zinc acetylacetonate, the organic ligand is selected from imidazole-2-carboxaldehyde and 2-nitroimidazole, and the acetylacetonate metal salt is selected from calcium acetylacetonate, manganese acetylacetonate, iron acetylacetonate, barium acetylacetonate, vanadium acetylacetonate, magnesium acetylacetonate, and copper acetylacetonate.
[0012] In the preparation method described above, the molar ratio of zinc salt to organic ligand is 2–4:1, the reaction temperature of zinc salt, organic ligand and acetylacetone metal salt is 20–120 °C, and the reaction time is 0.5–72 h.
[0013] The preparation method described above involves pyrolyzing oxygen-containing functional group ZIFs powder under inert gas protection using a programmed temperature calcination method. The programmed temperature rise rate is 2~10℃ / min, the pyrolysis temperature is 350~950℃, and the pyrolysis time is 0.5~3h.
[0014] The present invention also provides a mesoporous asymmetric single-atom catalyst, which is prepared by the above-described preparation method. The catalyst has a pore structure of random through-pores with a pore size of 3.8~7.7 nm.
[0015] This invention also provides an application of a mesoporous asymmetric single-atom catalyst in a zinc-iodine battery. The mesoporous asymmetric single-atom catalyst serves as a support for loading metal single atoms and is used for polyiodide-catalyzed reactions in the zinc-iodine battery. The metal single atoms include Ca, Mg, Ba, Mn, Fe, V, and Cu.
[0016] The working principle of this invention is explained by selecting ZIF-90 (whose ligand is imidazole-2-carboxaldehyde) as a precursor. The aldehyde functional group in the ligand plays an important role in the high-temperature pyrolysis process. The aldehyde functional group reduces the thermal stability of MOF and generates reactive oxygen species in situ during pyrolysis, driving the oxidative etching reaction and continuously releasing CO / CO2. These gaseous products etch from the inside of the carbon skeleton outward, thereby creating uniform mesopores (3.8~7.7 nm) in the originally microporous ZIF-derived carbon material in one step.
[0017] This invention simultaneously constructs a mesoporous environment that promotes mass transfer and a metal-N3O microenvironment with an asymmetric electronic structure through a ligand ablation strategy, thereby realizing a rapid, stable, and efficient iodine redox reaction in zinc-iodine batteries.
[0018] Compared with the prior art, the present invention has the following advantages: This application uses organic ligands containing oxygen-containing functional groups such as aldehydes to react with metal salts in a mixed solvent to generate precursor MOFs. The precursor MOFs are then generated by high-temperature pyrolysis, which causes the ligands to undergo controlled thermal decomposition and release gas, thereby forming mesoporous channels in situ within the framework. Furthermore, by adjusting the amount of metal salts fed, various asymmetric single-atom structures can be realized.
[0019] Currently, ordered mesoporous MOFs are mainly synthesized via micellar template synthesis, which uses surfactants and block copolymer micelles as templates and achieves synthesis through a cooperative self-assembly mechanism. However, the design of surfactant components and the control of MOF crystallization processes are extremely complex and cumbersome, posing significant challenges to the regulation of mesoporous structures and making it difficult to extend the synthesis of MOFs with other components. Furthermore, the post-processing step of removing the template is tedious and may damage the structure or introduce impurities.
[0020] This application proposes a ligand ablation strategy where pores are generated through the active ablation of the carbon framework via chemical reactions. The pore walls are integrated with the carbon matrix, resulting in a continuous and complete structure without the risk of template residue. More importantly, this strategy achieves the integrated and synergistic construction of the mesoscopic structure and the microscopic coordination environment—oxygen-containing functional groups act as both pore-forming etchants and oxygen donors, simultaneously completing pore structure generation and metal coordination configuration modulation during a one-step pyrolysis process. Mesopores and asymmetric sites are created in situ during pyrolysis using the aldehyde groups of the precursor ligands themselves. This method is simple, efficient, and universal, providing a paradigm for designing highly efficient catalysts.
[0021] The synthesis process of this invention is simple, efficient, and highly reproducible. The prepared mesoporous metal-organic framework material has the advantage of adjustable mesopore size and porosity, and can be extended to group d and p elements. It not only provides an ideal catalyst for high-performance zinc-iodine batteries, but also provides a brand-new design idea and theoretical basis for the design of a new generation of asymmetric single-atom catalysts in the future. Attached Figure Description
[0022] Figure 1 The images are transmission electron microscope images of the mesoporous carbon-supported asymmetric Ca single-atom catalyst prepared in Example 4, where (a) is the pyrolysis product of Ca@ZIF-65 and (b) is the pyrolysis product of Ca@ZIF-90. Figure 2 Transmission electron microscope images of the microporous carbon-supported symmetric Ca single-atom catalyst (Ca-N4) prepared in Comparative Example 1, a is a low-magnification view and b is a high-magnification view; Figure 3 The nitrogen adsorption-desorption curves are for the microporous carbon-supported symmetric Ca single-atom catalyst (Ca-N4) prepared in Comparative Example 1. Figure 4The images are transmission electron microscope (TEM) images of the products obtained by pyrolysis of Ca@ZIF-90 at different temperatures in Comparative Example 2, where (a), (b), and (c) are pyrolysis temperatures of 350℃, 550℃, and 750℃, respectively. Figure 5 The rate capability diagram for using Ca-N4 and Ca-N3O as positive electrode materials in zinc-iodine batteries in Experiment Example 1 is shown. Figure 6 This demonstrates the long-cycle performance of Ca-N4 and Ca-N3O used as positive electrode materials in zinc-iodine batteries in Experiment Example 1. Detailed Implementation
[0023] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0024] Example 1 89.2 mg zinc nitrate hexahydrate, 50 mg calcium acetylacetonate, and 135.7 mg 2-nitroimidazole were dissolved in 12 mL DMF. The solution was sonicated for 20 minutes until the solid was completely dissolved. The solution was then placed in an oven and allowed to react at 120 °C for 12 hours. The precipitated product was collected by centrifugation, washed three times with DMF and twice with methanol, and then dried under vacuum at 60 °C for 12 hours to obtain Ca@ZIF-65 powder.
[0025] Example 2 30.74 mg of imidazole-2-carboxaldehyde was added to 2 mL of a water / ethanol mixture (volume ratio 4:1). After 3 hours, 2 mL of an aqueous solution containing 23.8 mg of zinc nitrate hexahydrate and 10 mg of calcium acetylacetonate dissolved in 1 mL of tetrahydrofuran (THF) were rapidly added to the mixture, followed by stirring at room temperature for 12 hours. The precipitate was obtained by centrifugation and washed with methanol and tetrahydrofuran, respectively. The precipitate was then dried under vacuum at 60 °C for 12 hours to obtain Ca@ZIF-90 powder.
[0026] Example 3 Zinc acetylacetonate (274 mg) and calcium acetylacetonate (96 mg) were dissolved in 15 mL of a 1:4 mixture of N,N-dimethylformamide and methanol. This solution was then added to 10 mL of a 1:4 mixture of N,N-dimethylformamide and methanol containing 504 mg of imidazole-2-carboxaldehyde. The mixture was stirred at room temperature for 12 hours. The product was collected by centrifugation, washed four times with methanol, and then dried under vacuum at 60 °C for 12 hours to obtain the Ca@ZIF-90 product.
[0027] Example 4 The Ca@ZIF-65 and Ca@ZIF-90 powders prepared in Examples 1 and 3 were finely ground and placed in an alumina crucible for pyrolysis at 950°C under nitrogen protection. The temperature was increased to 950°C at a rate of 5°C per minute, held for 2 hours, and after cooling, a black powder was obtained, which is the mesoporous carbon-supported asymmetric Ca single-atom catalyst (Ca-N3O). Transmission electron microscopy images of the product are shown below. Figure 1 As shown, by Figure 1 As can be seen, the strategy of preparing mesoporous carbon by ablation of oxygen-containing functional group ligands has been verified in both ZIF-65 and ZIF-90 fractions.
[0028] Example 5 30.74 mg of imidazole-2-carboxaldehyde was added to 2 mL of a water / ethanol mixture (volume ratio 4:1) to prepare solution A. Five solutions A were prepared in total. After 3 hours, 2 mL of zinc nitrate hexahydrate aqueous solution (containing 23.8 mg of zinc nitrate hexahydrate) and 10 mg of barium acetylacetonate, 10 mg of iron acetylacetonate, 10 mg of manganese acetylacetonate, and 10 mg of magnesium acetylacetonate dissolved in 1 mL of tetrahydrofuran were rapidly added to the above mixture, followed by stirring at room temperature for 12 hours. Ba@ZIF-90, Fe@ZIF-90, Mg@ZIF-90, and Mn@ZIF-90 products were obtained by centrifugation and washed with methanol. Then, the products were pyrolyzed at 950 °C for 2 h under a nitrogen atmosphere at a heating rate of 5 °C / min to prepare mesoporous carbon-supported asymmetric mesoporous single-atom catalysts (M-N3O).
[0029] Comparative Example 1 Zinc nitrate hexahydrate (1.069 g, 3.6 mmol) and calcium acetylacetonate (96 mg, 0.36 mmol) were simultaneously dissolved in 15 mL of methanol. The resulting solution was then added to 10 mL of methanol containing 1.161 g (14.2 mmol) of 2-methylimidazole. After vigorous stirring for 5 min, the mixture was allowed to stand at room temperature for 20 h without further stirring. Ca@ZIF-8 particles were collected by centrifugation, washed four times with methanol, and vacuum dried overnight. Subsequently, the mixture was pyrolyzed at 950°C for 2 h under a nitrogen atmosphere at a heating rate of 5°C / min to prepare a microporous carbon-supported symmetric Ca single-atom catalyst (Ca-N4).
[0030] Depend on Figure 2 , 3 Transmission electron microscopy images and nitrogen adsorption-desorption curves show that the pyrolysis products of ZIF-8 are microporous carbon materials.
[0031] Comparative Example 2 Ca@ZIF-90 powder was finely ground and placed in an alumina crucible. Under nitrogen protection, it was pyrolyzed at 350℃, 550℃, and 750℃ respectively, and then the program was immediately stopped and the furnace was cooled. After cooling, pyrolysis intermediates at 350℃, 550℃, and 750℃ were obtained, respectively. The results are as follows... Figure 4 As shown, as the pyrolysis temperature continues to rise, the pore size produced by etching also gradually increases.
[0032] Experimental Example 1 Ca-N4 and Ca-N3O (obtained by pyrolysis of Ca@ZIF-90) were respectively prepared into homogeneous slurries with NMP. The slurries were then coated onto a titanium mesh and vacuum-dried overnight at 80°C. The resulting positive electrode was then cut. A 0.1 M M 2+1 M KI aqueous solution was then dropped onto the electrode, and a coin-shaped battery was assembled in air. The prepared electrode (12 mm in diameter) was used as the positive electrode, zinc foil (0.05 mm thick, 16 mm in diameter) as the negative electrode, and a 2 M Zn(SO4)2 aqueous solution as the electrolyte. The battery performance was then tested. Experimental results are shown below. Figure 5 , 6 .like Figure 5 As shown, Ca-N3O exhibits significantly superior capacity performance at all current densities: at 0.1 A g -1 With a capacity of up to 224.2 mAh g -1 Even in 10Ag -1 It can still maintain 160.6mAh g at high rates. -1 The capacity retention rate reached 71.6%; while the microporous CaN4 / I2 at 0.1 Ag... -1 It only provides 143.6 mAh g. -1 , in 10A g-1 After cycling, the capacity rapidly decreased to 44.5 mAh g. -1 .like Figure 6 As shown, the Ca-N3O / I2 electrode can achieve a high capacity of 230 mAh / g at a current density of 0.1 A / g and has excellent durability, maintaining a capacity of 201 mAh / g after 500 cycles, which is equivalent to an extremely low decay rate of only 0.02% per cycle.
[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a mesoporous asymmetric single-atom catalyst, characterized in that: This method involves dissolving and mixing zinc salts, organic ligands with oxygen-containing functional groups, and acetylacetone metal salts to obtain oxygen-containing functional group ZIFs materials. Then, the oxygen-containing functional group ZIFs powder is subjected to high-temperature pyrolysis to obtain a mesoporous carbon-supported asymmetric single-atom catalyst.
2. The method for preparing a mesoporous asymmetric single-atom catalyst according to claim 1, characterized in that: The steps for preparing oxygen-containing functional group ZIFs materials are as follows: S1. Dissolve the organic ligand in a mixed organic solvent to obtain solution A, and prepare an aqueous solution of zinc salt and a solution of acetylacetone metal salt or a mixed solution of zinc salt and acetylacetone metal salt; S2. When solution A is stirred, zinc salt solution and acetylacetone metal salt solution or a mixed solution of zinc salt and acetylacetone metal salt are added dropwise. The reaction is stirred and then centrifuged and washed after the reaction is completed to obtain oxygen-containing functional group ZIFs powder.
3. The method for preparing a mesoporous asymmetric single-atom catalyst according to claim 1, characterized in that: The steps for preparing oxygen-functionalized ZIFs materials are as follows: Zinc salt, organic ligand, and acetylacetone metal salt are dissolved in an organic solvent, heated and allowed to stand for reaction, and centrifuged and washed after the reaction is completed to obtain oxygen-functionalized ZIFs powder.
4. A method for preparing a mesoporous asymmetric single-atom catalyst according to any one of claims 1-3, characterized in that: The zinc salt is selected from zinc nitrate hexahydrate and zinc acetylacetonate, the organic ligand is selected from imidazole-2-carboxaldehyde and 2-nitroimidazole, and the acetylacetonate metal salt is selected from calcium acetylacetonate, manganese acetylacetonate, iron acetylacetonate, barium acetylacetonate, vanadium acetylacetonate, magnesium acetylacetonate, and copper acetylacetonate.
5. The method for preparing a mesoporous asymmetric single-atom catalyst according to claim 4, characterized in that: The molar ratio of zinc salt to organic ligand is 2–4:1, the reaction temperature of zinc salt, organic ligand and acetylacetone metal salt is 20–120℃, and the reaction time is 0.5–72 h.
6. The method for preparing a mesoporous asymmetric single-atom catalyst according to claim 2, characterized in that: In step S1, the mixed organic solvent is two or more of N,N-dimethylformamide, methanol, dimethyl sulfoxide, n-butanol, dioxane, and acetonitrile. The solvent used in the mixed solution of zinc salt and acetylacetone metal salt is the above-mentioned mixed organic solvent. The solvent in the acetylacetone metal salt solution is selected from one of N,N-dimethylformamide, methanol, dimethyl sulfoxide, n-butanol, dioxane, and acetonitrile.
7. The method for preparing a mesoporous asymmetric single-atom catalyst according to claim 3, characterized in that: The organic solvent is selected from one or more of N,N-dimethylformamide, methanol, dimethyl sulfoxide, n-butanol, dioxane, and acetonitrile.
8. A method for preparing a mesoporous asymmetric single-atom catalyst according to any one of claims 1-3, characterized in that: The oxygen-containing functional group ZIFs powder was pyrolyzed under inert gas protection by a programmed temperature calcination method. The programmed temperature rise rate was 2~10℃ / min, the pyrolysis temperature was 350~950℃, and the pyrolysis time was 0.5~3h.
9. A mesoporous asymmetric single-atom catalyst, characterized in that: The catalyst is prepared by any one of the preparation methods described in claims 1-3 and 5-7, and the pore structure of the catalyst is an irregular through-pore with a pore size of 3.8~7.7 nm.
10. The application of the mesoporous asymmetric single-atom catalyst according to claim 9 in a zinc-iodine battery, characterized in that: The mesoporous asymmetric single-atom catalyst is used as a support to support metal single atoms for polyiodide-catalyzed reactions in zinc-iodine batteries. The metal single atoms include Ca, Mg, Ba, Mn, Fe, V, and Cu.