Preparation method of light-responsive Cu@Fe heterogeneous MOF energy storage material, light-responsive Cu@Fe heterogeneous MOF energy storage material and application thereof

Abstract

The present invention relates to the field of MOF energy storage technology, and in particular to a preparation method of a light-responsive Cu@Fe heterogeneous MOF energy storage material, a light-responsive Cu@Fe heterogeneous MOF energy storage material, and an application thereof. The method comprises the following steps: (1) preparing a core copper-based MOF, (2) preparing a core-shell structure Cu@Fe-MOF, and (3) performing surface plasma treatment to obtain the light-responsive Cu@Fe heterogeneous MOF energy storage material. HKUST-1 is used as the core, and its abundant d-orbital electrons and strong π-d orbital interaction are utilized to construct an efficient electron transport channel. Secondly, MIL-101(Fe) is selected as the shell, and by introducing 2,2'-bipyridine-5,5'-dicarboxylic acid as a photosensitive ligand, a significant enhancement of the light response performance is achieved.

Description

Technical Field

[0001] The present invention relates to the field of MOF energy storage technology, and in particular to a preparation method of a light-responsive Cu@Fe heterogeneous MOF energy storage material, a light-responsive Cu@Fe heterogeneous MOF energy storage material and applications thereof. Background Art

[0002] With the rapid development of renewable energy and the expansion of smart grids, efficient and multifunctional energy storage materials have become an increasing research hotspot in the energy field. Metal-organic framework (MOF) materials have attracted much attention in the energy storage field due to their high specific surface area, tunable porosity, and rich functionalization possibilities. However, traditional MOF materials still face many challenges in practical applications, especially in the coordinated optimization of photoresponsiveness and electrochemical performance.

[0003] In the existing technology, MOF materials with a single metal center often find it difficult to simultaneously achieve efficient electron transport and excellent photoresponse performance. For example, copper-based MOFs such as HKUST-1 have good electron conductivity but lack significant photoresponse characteristics. Iron-based MOFs such as MIL-101(Fe) exhibit photocatalytic activity under certain conditions, but their electron transport efficiency is relatively low. In addition, most MOF materials face the problem of insufficient structural stability during long-term cycling, which seriously limits their application in practical energy storage devices.

[0004] Some researchers have attempted to improve the overall performance of MOF materials by mixing metal centers or through subsequent functionalization. However, these approaches often struggle to achieve optimal synergy between the functionalities of the components and face challenges in maintaining the material's high surface area and regular pore structure. In particular, achieving an organic combination of photoresponsiveness and energy storage performance without sacrificing the inherent advantages of MOF materials remains a pressing technical challenge. Summary of the Invention

[0005] The present invention aims to solve the above technical problems. Through innovative core-shell structure design, precise introduction of photosensitive ligands and synergistic optimization of surface plasma treatment, a new Cu@Fe heterogeneous MOF material with both high-efficiency photoresponse performance and excellent energy storage performance is developed.

[0006] The object of the present invention is to provide a method for preparing a light-responsive Cu@Fe heterogeneous MOF energy storage material, comprising the following steps:

[0007] (1) Preparation of core copper-based MOF:

[0008] First, add 200-250 parts by weight of N,N-dimethylformamide into a 500 mL round-bottom flask;

[0009] Next, add 30-40 parts by weight of copper nitrate trihydrate and stir at 20-25°C until completely dissolved;

[0010] Then, slowly add 15-20 parts by weight of 1,3,5-benzenetricarboxylic acid and continue stirring for 30-60 minutes;

[0011] Again, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed;

[0012] Next, the reactor was placed in an oven at 120-140° C. for 24-48 hours;

[0013] Afterwards, the mixture was cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each;

[0014] Finally, the obtained product was vacuum dried at 80-100 °C for 12-24 hours to obtain the inner core copper-based MOF;

[0015] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0016] First, the core copper-based MOF obtained in step (1) is dispersed in 180-220 parts by weight of N,N-dimethylformamide and ultrasonically treated for 30-60 minutes;

[0017] Secondly, dissolving 25-35 parts by weight of ferric chloride hexahydrate in 50-70 parts by weight of N,N-dimethylformamide;

[0018] Then, 8-12 parts by weight of terephthalic acid and 2-4 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid are dissolved in the remaining N,N-dimethylformamide;

[0019] Again, slowly add the iron salt solution dropwise to the core copper-based MOF suspension and stir for 30-60 minutes;

[0020] Then, slowly add the mixed solution of terephthalic acid and 2,2'-bipyridine-5,5'-dicarboxylic acid, and stir at room temperature for 2-4 hours;

[0021] Afterwards, the resulting mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed;

[0022] Then, the reactor was placed in an oven at 150-180° C. for 48-72 hours;

[0023] Then, the mixture was cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each;

[0024] Finally, the obtained product was vacuum dried at 100-120 °C for 24-48 hours to obtain the core-shell structure Cu@Fe-MOF;

[0025] (3) Surface plasma treatment:

[0026] First, the core-shell structure Cu@Fe-MOF obtained in step (2) is placed in a plasma treatment chamber;

[0027] Secondly, vacuum to 1-5Pa;

[0028] Then, oxygen is introduced and the pressure is controlled at 10-50 Pa;

[0029] Again, set the RF power to 50-100W and the treatment time to 5-15 minutes;

[0030] Finally, turn off the power, vent to normal pressure, take out the sample, and obtain the photoresponsive Cu@Fe heterogeneous MOF energy storage material.

[0031] Preferably, the core copper-based MOF is HKUST-1.

[0032] Preferably, the shell of the core-shell structure Cu@Fe-MOF is MIL-101(Fe).

[0033] Preferably, the preparation process of the core copper-based MOF in step (1) is carried out in a polytetrafluoroethylene-lined high-pressure reactor.

[0034] Preferably, the preparation process of the core-shell structure Cu@Fe-MOF in step (2) is carried out in a polytetrafluoroethylene-lined high-pressure reactor.

[0035] Preferably, 2,2'-bipyridine-5,5'-dicarboxylic acid is added as a photosensitizing ligand in step (2).

[0036] Preferably, oxygen is used as the processing gas in the plasma treatment in step (3).

[0037] Photoresponsive Cu@Fe heterogeneous MOF energy storage material, which is prepared by the method described.

[0038] Preferably, the material has a core-shell structure, wherein the core is a copper-based MOF and the shell is an iron-based MOF.

[0039] The application of the photoresponsive Cu@Fe heterogeneous MOF energy storage material in supercapacitors.

[0040] The core innovation of this invention lies in its unique molecular design and sophisticated structural regulation. First, HKUST-1 is used as the core, and its abundant d-orbital electrons and strong π-d orbital interactions are utilized to construct an efficient electron transport channel. Secondly, MIL-101(Fe) is selected as the shell, and by introducing 2,2'-bipyridine-5,5'-dicarboxylic acid as a photosensitive ligand, the photoresponsive performance is significantly enhanced. This core-shell structure not only achieves spatial separation of functions, but also forms a unique electronic state at the interface, further optimizing the electrochemical performance of the material.

[0041] More notably, the present invention significantly increases the number of active sites on the material's surface through a carefully designed surface plasma treatment, while maintaining the integrity of the MOF framework. This treatment not only enhances the material's electrochemical activity but also potentially introduces oxygen vacancies or other defects on the MOF surface, further enhancing the material's photoresponse and charge separation efficiency.

[0042] From the perspective of molecular orbital theory and solid-state physics, the core-shell structure of this invention achieves energy band engineering at the molecular scale. The conduction band of the core HKUST-1 and the valence band of the shell MIL-101(Fe) form a stepped energy level structure, which facilitates the rapid separation and directional migration of photogenerated electron-hole pairs. Furthermore, the introduction of the photosensitive ligand may split the coordination field around the Fe(III) ion, generating new energy levels and thus broadening the material's light absorption range.

[0043] Furthermore, the present invention exhibits some unexpected technical benefits. For example, the core-shell structure not only increases the specific surface area of ​​the material but also forms a unique microporous structure at the interface, likely due to the mismatch effect between the two MOF lattices. This unique pore structure provides an ideal channel for the rapid diffusion of the electrolyte and may also serve as an active site for charge storage, significantly improving the material's capacitance and rate performance.

[0044] In summary, this invention successfully combines photoresponsiveness with efficient energy storage through multiple synergistic effects, resulting in the development of a multifunctional, high-performance new MOF material. This material not only significantly surpasses existing technologies in various performance indicators but also opens up new possibilities for the development of a new generation of intelligent, integrated energy storage devices. Its excellent photoelectric conversion efficiency, high specific capacitance, superior rate capability, and exceptional cycling stability hold broad application prospects in a variety of cutting-edge fields, including integrated photovoltaic-energy storage systems, smart windows, and wearable devices. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example 1

[0047] This example provides a photoresponsive Cu@Fe heterogeneous MOF energy storage material and its preparation method. This material has a core-shell structure, with the core being the HKUST-1 copper-based MOF and the outer shell being the MIL-101(Fe) iron-based MOF. This unique structural design combines the advantages of both metal MOFs to achieve efficient electron transport and photoresponsive performance.

[0048] The preparation method of the material comprises the following steps:

[0049] (1) Preparation of core copper-based MOF (HKUST-1):

[0050] First, 200 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Next, 30 parts by weight of copper nitrate trihydrate were added and stirred at 20°C until completely dissolved. Then, 15 parts by weight of 1,3,5-benzenetricarboxylic acid were slowly added and stirring continued for 30 minutes. Again, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Next, the autoclave was placed in a 120°C oven for 24 hours. Afterwards, it was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the resulting product was vacuum dried at 80°C for 12 hours to obtain a core copper-based MOF.

[0051] In the embodiments of the present invention, HKUST-1 is preferably selected based on its excellent electron conductivity. This is due to the strong interaction between the copper ion's d orbitals and the ligand's π orbitals, which facilitates rapid electron transport within the MOF framework. This efficient electron transport pathway provides the foundation for the excellent charge-discharge performance of the entire material.

[0052] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0053] First, the core copper-based MOF obtained in step (1) was dispersed in 180 parts by weight of N,N-dimethylformamide and ultrasonically treated for 30 minutes. Secondly, 25 parts by weight of ferric chloride hexahydrate was dissolved in 50 parts by weight of N,N-dimethylformamide. Then, 8 parts by weight of terephthalic acid and 2 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid were dissolved in the remaining N,N-dimethylformamide. Again, the iron salt solution was slowly added dropwise to the core copper-based MOF suspension and stirred for 30 minutes. Next, the mixed solution of terephthalic acid and 2,2'-bipyridine-5,5'-dicarboxylic acid was slowly added and stirred at room temperature for 2 hours. Thereafter, the resulting mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Subsequently, the autoclave was placed in an oven at 150°C and maintained for 48 hours. Subsequently, the mixture was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the obtained product was vacuum dried at 100 °C for 24 h to obtain the core-shell structure Cu@Fe-MOF.

[0054] It is noteworthy that in this example, the introduction of 2,2'-bipyridine-5,5'-dicarboxylic acid as a photosensitizing ligand significantly enhances the material's light response. This photosensitizing ligand can form a photosensitive complex with iron ions under light conditions, promoting electron excitation and transfer, thereby improving the material's photoelectric conversion efficiency.

[0055] (3) Surface plasma treatment:

[0056] First, the core-shell structure Cu@Fe-MOF obtained in step (2) was placed in a plasma treatment chamber. Secondly, the vacuum was evacuated to 1 Pa. Then, oxygen was introduced and the pressure was controlled at 10 Pa. Again, the radio frequency power was set to 50 W and the treatment time was 5 minutes. Finally, the power was turned off, the exhaust was reduced to normal pressure, and the sample was removed to obtain the photoresponsive Cu@Fe heterogeneous MOF energy storage material.

[0057] Furthermore, the plasma treatment step of the present invention is a key innovation. By using oxygen plasma treatment, the MOF surface can be effectively activated, increasing active sites and improving the material's reactivity. This treatment may introduce surface defects or modify surface functional groups, further enhancing the material's photoresponse and electrochemical properties.

[0058] Example 2

[0059] This embodiment also provides a photoresponsive Cu@Fe heterogeneous MOF energy storage material and a preparation method thereof, but some parameters are adjusted to explore the effects of different conditions on the material properties.

[0060] The preparation method of the material comprises the following steps:

[0061] (1) Preparation of core copper-based MOF (HKUST-1):

[0062] First, 225 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Next, 35 parts by weight of copper nitrate trihydrate were added and stirred at 22.5°C until completely dissolved. Then, 17.5 parts by weight of 1,3,5-benzenetricarboxylic acid were slowly added and stirring continued for 45 minutes. Again, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Next, the autoclave was placed in a 130°C oven and kept for 36 hours. Afterwards, it was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the resulting product was vacuum dried at 90°C for 18 hours to obtain a core copper-based MOF.

[0063] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0064] First, the core copper-based MOF obtained in step (1) was dispersed in 200 parts by weight of N,N-dimethylformamide and ultrasonically treated for 45 minutes. Secondly, 30 parts by weight of ferric chloride hexahydrate was dissolved in 60 parts by weight of N,N-dimethylformamide. Then, 10 parts by weight of terephthalic acid and 3 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid were dissolved in the remaining N,N-dimethylformamide. Again, the iron salt solution was slowly added dropwise to the core copper-based MOF suspension and stirred for 45 minutes. Next, the mixed solution of terephthalic acid and 2,2'-bipyridine-5,5'-dicarboxylic acid was slowly added and stirred at room temperature for 3 hours. Thereafter, the resulting mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Subsequently, the autoclave was placed in an oven at 165°C and maintained for 60 hours. Subsequently, the mixture was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the obtained product was vacuum dried at 110 °C for 36 h to obtain the core-shell structure Cu@Fe-MOF.

[0065] Preferably, in this embodiment, by extending the reaction time and increasing the reaction temperature, we expect to obtain a more complete core-shell structure and higher crystallinity. This optimization may affect the specific surface area and porosity of the material, thereby affecting its energy storage performance.

[0066] (3) Surface plasma treatment:

[0067] First, the core-shell structure Cu@Fe-MOF obtained in step (2) was placed in a plasma treatment chamber. Secondly, the vacuum was evacuated to 3 Pa. Then, oxygen was introduced and the pressure was controlled at 30 Pa. Again, the radio frequency power was set to 75 W and the treatment time was 10 minutes. Finally, the power was turned off, the exhaust was reduced to normal pressure, and the sample was removed to obtain the photoresponsive Cu@Fe heterogeneous MOF energy storage material.

[0068] It is worth noting that the intensity and time of the plasma treatment were increased in this embodiment, which may lead to deeper surface modification and further enhance the photoresponse performance and electrochemical activity of the material.

[0069] Example 3

[0070] This example provides another photoresponsive Cu@Fe heterogeneous MOF energy storage material and its preparation method, and further explores the effect of parameter adjustment on material properties.

[0071] The preparation method of the material comprises the following steps:

[0072] (1) Preparation of core copper-based MOF (HKUST-1):

[0073] First, 250 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Next, 40 parts by weight of copper nitrate trihydrate were added and stirred at 25°C until completely dissolved. Then, 20 parts by weight of 1,3,5-benzenetricarboxylic acid were slowly added and stirring continued for 60 minutes. Again, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Next, the autoclave was placed in a 140°C oven and kept for 48 hours. Afterwards, it was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the resulting product was vacuum dried at 100°C for 24 hours to obtain a core copper-based MOF.

[0074] Furthermore, in this example, by increasing the concentration of the reactants and extending the reaction time, we expect to obtain HKUST-1 crystals with higher yields and larger particle sizes, which may affect the formation process of the core-shell structure and the properties of the final material.

[0075] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0076] First, the core copper-based MOF obtained in step (1) was dispersed in 220 parts by weight of N,N-dimethylformamide and ultrasonically treated for 60 minutes. Secondly, 35 parts by weight of ferric chloride hexahydrate was dissolved in 70 parts by weight of N,N-dimethylformamide. Then, 12 parts by weight of terephthalic acid and 4 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid were dissolved in the remaining N,N-dimethylformamide. Again, the iron salt solution was slowly added dropwise to the core copper-based MOF suspension and stirred for 60 minutes. Next, the mixed solution of terephthalic acid and 2,2'-bipyridine-5,5'-dicarboxylic acid was slowly added and stirred at room temperature for 4 hours. Thereafter, the resulting mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Subsequently, the autoclave was placed in an oven at 180°C and maintained for 72 hours. Subsequently, the mixture was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the obtained product was vacuum dried at 120 °C for 48 h to obtain the core-shell structure Cu@Fe-MOF.

[0077] It is worth noting that the amount of 2,2'-bipyridine-5,5'-dicarboxylic acid was increased in this example, which may further enhance the photoresponse properties of the material. At the same time, extending the reaction time and increasing the reaction temperature may affect the integrity and crystallinity of the core-shell structure.

[0078] (3) Surface plasma treatment:

[0079] First, the core-shell structure Cu@Fe-MOF obtained in step (2) was placed in a plasma treatment chamber. Secondly, the vacuum was evacuated to 5 Pa. Then, oxygen was introduced and the pressure was controlled at 50 Pa. Again, the radio frequency power was set to 100 W and the treatment time was 15 minutes. Finally, the power was turned off, the exhaust was reduced to normal pressure, and the sample was removed to obtain the photoresponsive Cu@Fe heterogeneous MOF energy storage material.

[0080] Preferably, the highest intensity plasma treatment is used in this embodiment, which may lead to significant changes in the surface of the material, including the introduction of more defect sites and functional groups, thereby significantly improving the electrochemical activity and photoresponse performance of the material.

[0081] Example 4

[0082] This example provides a photoresponsive Cu@Fe heterogeneous MOF energy storage material and a preparation method thereof, and explores the influence of intermediate parameter values ​​on material properties.

[0083] The preparation method of the material comprises the following steps:

[0084] (1) Preparation of core copper-based MOF (HKUST-1):

[0085] First, 225 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Next, 35 parts by weight of copper nitrate trihydrate were added and stirred at 22.5°C until completely dissolved. Then, 17.5 parts by weight of 1,3,5-benzenetricarboxylic acid were slowly added and stirring continued for 45 minutes. Again, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Next, the autoclave was placed in a 130°C oven and kept for 36 hours. Afterwards, it was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the resulting product was vacuum dried at 90°C for 18 hours to obtain a core copper-based MOF.

[0086] Furthermore, this example uses intermediate reaction parameters to balance factors such as yield, crystallinity, and particle size to obtain the optimal core copper-based MOF structure. This balance may affect the subsequent formation of the core-shell structure and the performance of the final material.

[0087] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0088] First, the core copper-based MOF obtained in step (1) was dispersed in 200 parts by weight of N,N-dimethylformamide and ultrasonically treated for 45 minutes. Secondly, 30 parts by weight of ferric chloride hexahydrate was dissolved in 60 parts by weight of N,N-dimethylformamide. Then, 10 parts by weight of terephthalic acid and 3 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid were dissolved in the remaining N,N-dimethylformamide. Again, the iron salt solution was slowly added dropwise to the core copper-based MOF suspension and stirred for 45 minutes. Next, the mixed solution of terephthalic acid and 2,2'-bipyridine-5,5'-dicarboxylic acid was slowly added and stirred at room temperature for 3 hours. Thereafter, the resulting mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed. Subsequently, the autoclave was placed in an oven at 165°C and maintained for 60 hours. Subsequently, the mixture was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the obtained product was vacuum dried at 110 °C for 36 h to obtain the core-shell structure Cu@Fe-MOF.

[0089] Preferably, in this embodiment, by selecting intermediate reaction conditions, we expect to achieve an optimal balance between core-shell structural integrity, crystallinity, and photoresponsiveness. In particular, the amount of 2,2'-bipyridine-5,5'-dicarboxylic acid is selected to be an intermediate value, aiming to achieve an optimal combination of photosensitivity and structural stability.

[0090] (3) Surface plasma treatment:

[0091] First, the core-shell structure Cu@Fe-MOF obtained in step (2) was placed in a plasma treatment chamber. Secondly, the vacuum was evacuated to 3 Pa. Then, oxygen was introduced and the pressure was controlled at 30 Pa. Again, the radio frequency power was set to 75 W and the treatment time was 10 minutes. Finally, the power was turned off, the exhaust was reduced to normal pressure, and the sample was removed to obtain the photoresponsive Cu@Fe heterogeneous MOF energy storage material.

[0092] It is worth noting that a moderate plasma intensity was used in this example, which aims to strike a balance between surface activation and structural integrity. We expect that this treatment can moderately increase the surface active sites while avoiding excessive destruction of the core-shell structure of the material.

[0093] Finally, it's worth emphasizing that these examples demonstrate the core innovation of this invention: through a carefully designed core-shell structure, the introduction of a photosensitive ligand, and surface plasmon treatment, a unique combination of photoresponsiveness and efficient energy storage is achieved. The development of this multifunctional MOF material offers new possibilities for addressing energy storage and conversion challenges, and is expected to find widespread application in fields such as supercapacitors and photoelectric conversion devices.

[0094] Comparative Example 1: Single HKUST-1MOF Material

[0095] This comparative example aims to verify the necessity of the core-shell structure. HKUST-1 was prepared using the same method as in Example 1, but without subsequent core-shell structure construction and surface treatment.

[0096] The preparation method comprises the following steps:

[0097] First, 200 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Secondly, 30 parts by weight of copper nitrate trihydrate were added and stirred at 20°C until completely dissolved. Then, 15 parts by weight of 1,3,5-benzenetricarboxylic acid were slowly added and stirring continued for 30 minutes. Again, the mixture was transferred to a polytetrafluoroethylene-lined high-pressure reactor and sealed. Next, the reactor was placed in a 120°C oven and kept for 24 hours. Afterwards, it was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the resulting product was vacuum dried at 80°C for 12 hours to obtain the HKUST-1MOF material.

[0098] Preferably, by comparison with Example 1, we expect that this single MOF structure will lack photoresponsiveness and may also have lower energy storage capacity. This comparison can highlight the important role of the core-shell structure in achieving multifunctionality.

[0099] Comparative Example 2: Cu@Fe-MOF material without photosensitive ligand

[0100] This comparative example aims to verify the necessity of the photosensitizing ligand. A method similar to that of Example 2 is used, but 2,2'-bipyridine-5,5'-dicarboxylic acid is not added when preparing the outer shell.

[0101] The preparation method comprises the following steps:

[0102] (1) Preparation of core copper-based MOF (HKUST-1):

[0103] Same as step (1) in Example 2.

[0104] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0105] First, the core copper-based MOF obtained in step (1) was dispersed in 200 parts by weight of N,N-dimethylformamide and ultrasonically treated for 45 minutes. Next, 30 parts by weight of ferric chloride hexahydrate was dissolved in 60 parts by weight of N,N-dimethylformamide. Then, 13 parts by weight of terephthalic acid was dissolved in the remaining N,N-dimethylformamide. Again, the iron salt solution was slowly added dropwise to the core copper-based MOF suspension and stirred for 45 minutes. Next, the terephthalic acid solution was slowly added and stirred at room temperature for 3 hours. The subsequent steps were the same as in Example 2.

[0106] (3) Surface plasma treatment:

[0107] Same as step (3) of Example 2.

[0108] Furthermore, by comparing the performance differences between this comparative example and Example 2, we anticipate that we can clearly demonstrate the key role of 2,2'-bipyridine-5,5'-dicarboxylic acid as a photosensitive ligand in enhancing the material's photoresponsive properties. This comparison can also reveal the synergistic mechanism between the photosensitive ligand and the iron-based MOF.

[0109] Comparative Example 3: Cu@Fe-MOF material without plasma treatment

[0110] This comparative example aims to verify the necessity of surface plasma treatment. A core-shell structured Cu@Fe-MOF was prepared using the same method as in Example 3, but without the final plasma treatment step.

[0111] The preparation method comprises the following steps:

[0112] (1) Preparation of core copper-based MOF (HKUST-1):

[0113] Same as step (1) of Example 3.

[0114] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0115] Same as step (2) of Example 3.

[0116] Preferably, by comparing the performance differences between this comparative example and Example 3, we expect to clearly demonstrate the important role of plasma treatment in enhancing the surface activity of the material, improving the photoresponse performance and electrochemical performance. This comparison can reveal how surface treatment affects the electronic structure and reactivity of the material.

[0117] Comparative Example 4: Inverse core-shell structure Fe@Cu-MOF material

[0118] This comparative example aims to verify the necessity of a specific core-shell structure design. A method similar to Example 4 is used, but the order of the materials of the core and shell is reversed.

[0119] The preparation method comprises the following steps:

[0120] (1) Preparation of core iron-based MOF (MIL-101(Fe)):

[0121] First, 200 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Secondly, 30 parts by weight of ferric chloride hexahydrate were added and stirred at 22.5°C until completely dissolved. Then, 10 parts by weight of terephthalic acid and 3 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid were slowly added and stirring continued for 45 minutes. Again, the mixture was transferred to a polytetrafluoroethylene-lined high-pressure reactor and sealed. Next, the reactor was placed in a 165°C oven and kept for 60 hours. Afterwards, it was naturally cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each. Finally, the resulting product was vacuum dried at 110°C for 36 hours to obtain an inner core iron-based MOF.

[0122] (2) Preparation of core-shell structure Fe@Cu-MOF:

[0123] A similar procedure to step (2) of Example 4 was employed, but the roles of the copper salt and the iron salt were interchanged.

[0124] (3) Surface plasma treatment:

[0125] Same as step (3) of Example 4.

[0126] Furthermore, by comparing the performance differences between this comparative example and Example 4, we anticipate that the importance of a specific core-shell structure design (copper-based core, iron-based shell) in achieving efficient electron transport and photoresponsive performance can be confirmed. This comparison can reveal the intrinsic connection between material structure and performance.

[0127] Comparative Example 5: Cu / Fe mixed MOF material without core-shell structure

[0128] This comparative example aims to verify the superiority of the core-shell structure over the simple mixed structure, and a mixed MOF containing copper and iron is synthesized simultaneously by a one-step method.

[0129] The preparation method comprises the following steps:

[0130] First, 225 parts by weight of N,N-dimethylformamide were added to a 500 mL round-bottomed roasted melon. Next, 17.5 parts by weight of copper nitrate trihydrate and 15 parts by weight of ferric chloride hexahydrate were added and stirred at 22.5°C until completely dissolved. Then, a mixture of 13.75 parts by weight of 1,3,5-benzenetricarboxylic acid, 5 parts by weight of terephthalic acid, and 1.5 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid was slowly added and stirred for 45 minutes. The mixture was then transferred to a polytetrafluoroethylene-lined autoclave and sealed. The autoclave was then placed in an oven at 150°C for 48 hours. The mixture was then naturally cooled to room temperature, filtered, and washed three times with N,N-dimethylformamide and three times with ethanol. Finally, the resulting product was vacuum-dried at 100°C for 24 hours to obtain a Cu / Fe hybrid MOF material.

[0131] Then, the same surface plasma treatment as in Example 4 was performed.

[0132] Preferably, by comparing the performance differences between this comparative example and Example 4, we expect to confirm the superiority of the core-shell structure in achieving functional partitioning, improving electron transport efficiency, and enhancing photoresponse performance. This comparison can reveal how the core-shell structure synergistically exerts the respective advantages of the core and shell.

[0133] Comparative Example 6: Cu@Fe-MOF materials with different photosensitive ligand contents

[0134] This comparative example aims to verify the optimization effect of the photosensitizing ligand content. A method similar to that of Example 1 is used, but the amount of 2,2'-bipyridine-5,5'-dicarboxylic acid is significantly increased.

[0135] The preparation method comprises the following steps:

[0136] (1) Preparation of core copper-based MOF (HKUST-1):

[0137] Same as step (1) of Example 1.

[0138] (2) Preparation of core-shell structure Cu@Fe-MOF:

[0139] First, the core copper-based MOF obtained in step (1) was dispersed in 180 parts by weight of N,N-dimethylformamide and ultrasonically treated for 30 minutes. Next, 25 parts by weight of ferric chloride hexahydrate was dissolved in 50 parts by weight of N,N-dimethylformamide. Then, 4 parts by weight of terephthalic acid and 6 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid were dissolved in the remaining N,N-dimethylformamide. Subsequent steps were the same as in Example 1.

[0140] (3) Surface plasma treatment:

[0141] Same as step (3) of Example 1.

[0142] Furthermore, by comparing the performance differences between this comparative example and Example 1, we anticipate that optimizing the photosensitizer ligand content will impact material properties. Excessive photosensitizer ligand content may compromise the structural stability of the MOF, thus affecting its overall performance. This comparison will reveal the trade-off between photosensitizer ligand content and material structure and performance.

[0143] We designed a comprehensive series of experimental tests to evaluate the effectiveness and superiority of our photoresponsive Cu@Fe heterogeneous MOF energy storage material and its preparation method. These tests encompassed multiple aspects, including the material's structural characteristics, photoresponsiveness, electrochemical properties, and energy storage performance, aiming to fully demonstrate the core innovations and unique advantages of this invention.

[0144] First, we performed structural characterization of the materials. X-ray diffraction (XRD) analysis was used to confirm the crystal structure of HKUST-1 and MIL-101(Fe) and their presence in the core-shell material. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the morphology and interfacial characteristics of the core-shell structure. X-ray photoelectron spectroscopy (XPS) analysis was used to investigate the elemental composition and chemical state of the material surface, particularly changes before and after plasma treatment.

[0145] Next, we evaluated the material's photoresponse properties. UV-visible diffuse reflectance spectroscopy was used to analyze the material's light absorption characteristics. Photocurrent density measurements were performed under simulated sunlight to evaluate the material's photoelectric conversion efficiency. Transient photocurrent response testing was used to investigate the material's electron-hole pair separation efficiency under illumination.

[0146] Next, we further investigated the electrochemical properties of the material. Cyclic voltammetry (CV) tests were performed at different scan rates to evaluate the material's capacitance and reaction reversibility. Electrochemical impedance spectroscopy (EIS) analysis was used to investigate the material's electronic and ion transport properties. Galvanostatic charge-discharge tests were performed at various current densities to evaluate the material's specific capacity and rate capability.

[0147] Finally, we conducted long-term cyclic stability tests to evaluate the durability of the material in practical applications.

[0148] All tests were conducted at room temperature (25 ± 2°C) and a relative humidity of 50 ± 5%. Electrochemical tests used a three-electrode system with the prepared MOF material as the working electrode, a platinum counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and a 1 M Na2SO4 aqueous solution as the electrolyte.

[0149] Based on the above tests, we obtained the following results:

[0150] Table 1: Material structure and photoresponse performance test results

[0151]

[0152] Table 2: Electrochemical performance and energy storage performance test results

[0153]

[0154]

[0155] According to the above test results, Example 3 shows the best comprehensive performance and can be regarded as the best embodiment of the present invention. It has the highest specific surface area (1720m 2 / g), the maximum photocurrent density (18.7μA / cm 2 ), the fastest photoresponse time (63ms), the highest specific capacitance (390F / g), and the best cycling stability (96% retention after 5000 cycles).

[0156] After in-depth analysis of these data, we found that the present invention exhibits some unexpected technical effects:

[0157] 1. Ultra-high specific surface area and excellent pore structure: The specific surface area of ​​Example 3 reaches 1720m 2 / g, significantly higher than that of HKUST-1 alone (Comparative Example 1) and a simple mixed MOF (Comparative Example 5). This significant improvement is likely due to the interfacial effect of the core-shell structure, which creates additional microporous structures at the interface between the two MOFs. This unique pore structure not only provides more active sites but also facilitates rapid diffusion of the electrolyte, significantly improving the electrochemical performance of the material.

[0158] 2. Significantly enhanced photoresponse performance: The photocurrent density of Example 3 (18.7 μA / cm2) is more than 20 times higher than that of a single HKUST-1 (Comparative Example 1, 0.8 μA / cm2). This huge improvement is not just a simple material combination effect, but stems from the synergistic effect of the photosensitive ligand in the core-shell structure and the surface activation brought about by the plasma treatment. In particular, the photoresponse time is shortened to 63 ms, indicating that the material has extremely fast photoelectric conversion capabilities, which is of great significance for the development of efficient photoelectrochemical devices.

[0159] 3. Excellent rate performance: At a high current density of 20 A / g, Example 3 still maintains 85% of its capacitance. This excellent rate performance is attributed to the synergistic effect of the core-shell structure. The core HKUST-1 provides a fast electron transport channel, while the shell MIL-101(Fe) provides an efficient ion diffusion pathway. This unique structural design achieves synergistic optimization of electron and ion transport, which is difficult to achieve with traditional single MOF materials.

[0160] 4. Excellent cycling stability: After 5000 cycles, Example 3 still retained 96% of its capacitance. This excellent stability is likely attributed to the protective effect of the core-shell structure. The MIL-101(Fe) shell likely acts as a buffer layer during cycling, reducing structural stress in the HKUST-1 core and thus improving the overall material stability.

[0161] 5. Low Charge Transfer Resistance: The charge transfer resistance of Example 3 was only 2.7Ω, significantly lower than that of the other samples. This demonstrates that the core-shell structure and plasma treatment significantly improve the material's electrical conductivity and electrochemical activity. In particular, this low resistance is achieved while maintaining a high specific surface area, a characteristic difficult to achieve with conventional porous materials.

[0162] In summary, the present photoresponsive Cu@Fe heterogeneous MOF energy storage material demonstrates multifaceted synergistic effects, significantly surpassing single-component materials in various performance indicators while also achieving an organic combination of photoresponsiveness and energy storage performance. This multifunctional, high-performance novel material opens up new possibilities for the development of next-generation intelligent energy storage devices and is expected to find widespread application in integrated photovoltaic-energy storage systems, smart windows, and other fields.

[0163] The foregoing is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. Preparation method of photoresponsive Cu@Fe heterogeneous MOF energy storage material, characterized in that , including the following steps: (1) Preparation of core copper-based MOF: First, add 200-250 parts by weight of N,N-dimethylformamide into a 500 mL round-bottom flask; Next, add 30-40 parts by weight of copper nitrate trihydrate and stir at 20-25°C until completely dissolved; Then, 15-20 parts by weight of 1,3,5-benzenetricarboxylic acid was slowly added and stirring was continued for 30-60 minutes to obtain a mixture of N,N-dimethylformamide, copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid; Again, the mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed; Next, the reactor was placed in an oven at 120-140°C for 24-48 hours; Afterwards, the mixture was cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each; Finally, the obtained product was vacuum dried at 80-100 °C for 12-24 hours to obtain the core copper-based MOF; (2) Preparation of core-shell structure Cu@Fe-MOF: First, the core copper-based MOF obtained in step (1) is dispersed in 180-220 parts by weight of N,N-dimethylformamide and ultrasonically treated for 30-60 minutes; Secondly, 25-35 parts by weight of iron chloride hexahydrate is dissolved in 50-70 parts by weight of N, N-dimethylformamide to obtain an iron chloride hexahydrate solution in N, N-dimethylformamide; Then, 8-12 parts by weight of terephthalic acid and 2-4 parts by weight of 2,2'-bipyridine-5,5'-dicarboxylic acid are dissolved in the remaining N,N-dimethylformamide; Again, slowly add the N,N-dimethylformamide solution of ferric chloride hexahydrate to the core copper-based MOF suspension and stir for 30-60 minutes; Then, slowly add the mixed solution of terephthalic acid and 2,2'-bipyridine-5,5'-dicarboxylic acid and stir at room temperature for 2-4 hours; Afterwards, the resulting mixture was transferred to a polytetrafluoroethylene-lined autoclave and sealed; Then, the reactor was placed in an oven at 150-180°C for 48-72 hours; Then, the mixture was cooled to room temperature, filtered, and washed with N,N-dimethylformamide and ethanol three times each; Finally, the obtained product was vacuum dried at 100-120 °C for 24-48 h to obtain the core-shell structure Cu@Fe-MOF; (3) Surface plasma treatment: First, the core-shell structure Cu@Fe-MOF obtained in step (2) was placed in a plasma treatment chamber; Secondly, vacuum to 1-5 Pa; Then, oxygen was introduced and the pressure was controlled at 10-50 Pa; Again, set the RF power to 50-100 W and the treatment time to 5-15 minutes; Finally, turn off the power, vent to normal pressure, take out the sample, and obtain the photoresponsive Cu@Fe heterogeneous MOF energy storage material.

2. The preparation method according to claim 1, characterized in that , the core copper-based MOF is HKUST-1.

3. The preparation method according to claim 1, characterized in that , the shell of the core-shell structure Cu@Fe-MOF is MIL-101(Fe).

4. The preparation method according to claim 1, characterized in that , in step (2), 2,2'-bipyridine-5,5'-dicarboxylic acid is added as a photosensitizing ligand.

5. The preparation method according to claim 1, characterized in that , the plasma treatment in step (3) uses oxygen as the processing gas.

6. A photoresponsive Cu@Fe heterogeneous MOF energy storage material, characterized in that , the material is prepared by the method described in any one of claims 1-5.

7. The light-responsive Cu@Fe heterogeneous MOF energy storage material according to claim 6, characterized in that ,The material has a core-shell structure, in which the core is a copper-based MOF and the shell is an iron-based MOF.

8. Use of the photoresponsive Cu@Fe heterogeneous MOF energy storage material according to claim 6 or 7 in a supercapacitor.

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