Preparation method of topological star-shaped nano hollow reactor and application thereof

Abstract

The application relates to a preparation method of a topological star-shaped nano hollow reactor and application thereof. The application is to solve the problems of template assistance and harsh template removal conditions required by the formation of a traditional MOF derived nano hollow reactor. The preparation method comprises the following steps: firstly, zinc nitrate and CTAB are mixed and dissolved in deionized water to obtain a zinc nitrate solution; 2-methyl imidazole is added into the deionized water, and a methyl imidazole solution is obtained after stirring; the methyl imidazole solution is added into the zinc nitrate solution to obtain a star-shaped ZIF-8 nano column material; secondly, tannic acid water solution is added into the star-shaped ZIF-8 nano column material dispersion liquid to obtain a star-shaped hollow ZIF-8 nano column material; and thirdly, the star-shaped hollow ZIF-8 nano column material is calcined to obtain a topological star-shaped nano hollow reactor. The application realizes effective regulation of the geometric topological structure of the MOF-based material through a simple and mild chemical method, and hollow structures are etched by using organic acid, so that the complexity of the template removal step in the traditional etching process is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of MOF-derived hollow nanomaterials. BACKGROUND

[0002] Metal-organic framework compounds (MOFs) can be used as precursors or templates for the manufacture of MOF-derived hollow nanoreactors (HoNRs). They are usually composed of metal compounds, layered double hydroxides, biological enzymes and their mixed composite materials. MOF-derived hollow nanoreactors play an important role in photocatalysis, energy storage and conversion, and biomedicine, because they have superior properties such as large specific surface area, microporous or mesoporous, efficient electron and mass transport during the reaction process, inherited multifunctionality of structure, high resistance to acid-base environment, electrical conductivity and diversity of chemical composition.

[0003] In most cases, the technical synthesis path of MOF-derived hollow nanoreactors mainly depends on the decomposition of MOFs or their composite materials under certain conditions or chemical reactions with ideal reagents:

[0004] (1) Hollow silica derived from the secondary components of MOF@shell composite materials;

[0005] (2) Hollow porous carbon materials derived from the organic components of MOFs and their shell molecules;

[0006] (3) Hollow metal oxides, sulfides, carbides, supported HoNRs, etc. derived from the metal components of MOFs or MOF composite materials.

[0007] The geometric topological morphology of traditional MOF-derived hollow nanoreactors is usually a cube or a prismatic dodecahedron. It is difficult to synthesize MOF-based precursors with complex topological structures using simple chemical synthesis. In addition, the formation of hollow topological structures usually requires the assistance of templates such as silica (SiO2) and polystyrene (PS), and the significant disadvantage of this method is that the template needs to be removed under harsh conditions. Not only is the cost high, but the entire synthesis process is difficult, produces a lot of waste, and is not economical and universal for large-scale preparation. SUMMARY

[0008] The purpose of the present application is to solve the problem that the geometric topological morphology of traditional MOF-derived hollow nanoreactors is usually a cube or a prismatic dodecahedron, and the formation of hollow topological structures requires the assistance of templates, and the conditions for removing the templates are harsh, and to provide a preparation method of topological star-shaped hollow nanoreactors.

[0009] The preparation method of the topological star-shaped nanometer hollow reactor is realized according to the following steps:

[0010] I. Synthesis of star-shaped ZIF-8 nanocolumns:

[0011] Zn(NO3)2.6H2O and cetyltrimethylammonium bromide (CTAB) are mixed in deionized water to obtain a zinc nitrate solution; 2-methylimidazole (MeIM) is added to the deionized water, and after stirring, a methyl imidazole solution is obtained; the methyl imidazole solution is added (quickly) to the zinc nitrate solution, and the reaction is carried out at room temperature; after washing and drying, the star-shaped ZIF-8 nanocolumn material is obtained;

[0012] II. Synthesis of star-shaped hollow topological precursors:

[0013] The star-shaped ZIF-8 nanocolumn material is added to deionized water, and after ultrasonic dispersion, a dispersion liquid is obtained; a tannic acid aqueous solution is added to the dispersion liquid, and the reaction is stirred at room temperature; after collecting the solid phase and drying, the star-shaped hollow ZIF-8 nanocolumn material is obtained;

[0014] III. Synthesis of star-shaped hollow nanoreactor:

[0015] The star-shaped hollow ZIF-8 nanocolumn material and the activated material powder are placed at both ends of the crucible, and calcination treatment is carried out at a temperature of 620-750°C under an argon atmosphere; after cooling, the topological star-shaped nanometer hollow reactor (material) is obtained;

[0016] In step I, the mass ratio of Zn(NO3)2.6H2O to 2-methylimidazole is (1-1.5):(7-10); the methyl imidazole solution is added to the zinc nitrate solution, and the mass percentage content of cetyltrimethylammonium bromide (CTAB) in the system is 0.4-0.8wt%;

[0017] In step II, the mass ratio of the star-shaped ZIF-8 nanocolumn material to tannic acid is (15-25):1.

[0018] The application of the topological star-shaped nanometer hollow reactor is to use the topological star-shaped nanometer hollow reactor as a photocatalytic material, an electrocatalytic material, or a drug delivery material.

[0019] The application takes a representative zeolitic imidazolate framework (ZIF) material in the MOF family as a breakthrough point, and successfully prepares star-shaped nano ZIF materials with high symmetry and cross-shaped intersection by regulating the amount of surfactant cetyltrimethylammonium bromide (CTAB) in the initial precursor ZIF material and the ratio of metal salt to 2-methylimidazole (2-MeIM) in the ZIF material synthesis process. On this basis, the application uses tannic acid (TA), which is a polyphenol, as an organic acid. When tannic acid forms a chelate with the metal sites on the MOFs, it can provide many phenolic hydroxyl groups on the surface of the MOFs, which can act as a buffer in an alkaline environment. At the same time, the TA macromolecule can be chelated on the MOFs to form a protective layer, protecting the large framework of the MOFs from being destroyed. The slow release of H + The application can uniformly pass through the pores on the surface of the MOF-based material in the same direction and avoid the disadvantages of the "template method" to form a highly dispersed hollow topological star-shaped structure by undergoing a mild chemical reaction inside. After forming the MOF-based hollow topological precursor, a carbon-based shell / metal-based compound core-shell nano hollow reactor can be prepared by in-situ calcination at a temperature lower than the evaporation temperature of the metal salt.

[0020] The application realizes effective regulation of the geometric topological structure of the MOF-based material by simple and mild chemical means. And with the etching effect of TA, an organic acid, a highly dispersed hollow topological structure is formed. The overall technical effect is better than that of the nano hollow structure prepared by the traditional "template method". In addition, by calcination or further chemical reaction means, the free metal salt ions in the MOF can be converted into the corresponding metal compounds in-situ. Through the protection mechanism of TA, the stable existence of enzymes and macromolecules in the hollow cavity can also be realized. This topological hollow structure technology can be applied to the fields of (photo) electrocatalysis, new energy conversion and storage, and biomedicine. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 SEM image of the star-shaped ZIF-8 nanocolumn prepared in step one of the example;

[0022] Figure 2 TEM image of the star-shaped ZIF-8 nanocolumn prepared in step one of the example;

[0023] Figure 3 SEM image of the star-shaped hollow topological precursor prepared in step two of the example;

[0024] Figure 4 SEM image of the topological star-shaped nano hollow reactor prepared in step three of the example;

[0025] Figure 5TEM image of topological star-shaped nanometer hollow reactor prepared for example step three;

[0026] Figure 6 BET image (left) and pore volume image (right) of topological star-shaped nanometer hollow reactor prepared for example step three;

[0027] Figure 7 Photocatalytic CO2 reduction performance image (left) and cycle stability column chart (right) of topological star-shaped nanometer hollow reactor prepared for example step three. DETAILED DESCRIPTION

[0028] Specific embodiment one: the preparation method of the topological star-shaped nanometer hollow reactor in this embodiment is implemented according to the following steps:

[0029] I. Synthesis of star-shaped ZIF-8 nanocolumns:

[0030] Zn(NO3)2·6H2O and cetyltrimethylammonium bromide (CTAB) were mixed in deionized water to obtain a zinc nitrate solution; 2-methylimidazole (MeIM) was added to deionized water, and after stirring, a methyl imidazole solution was obtained. The methyl imidazole solution was added (quickly) to the zinc nitrate solution, and the reaction was allowed to stand at room temperature. After washing and drying, star-shaped ZIF-8 nanocolumn materials were obtained;

[0031] II. Synthesis of star-shaped hollow topological precursor:

[0032] The star-shaped ZIF-8 nanocolumn material was added to deionized water, and after ultrasonic dispersion, a dispersion liquid was obtained. A single tannic acid aqueous solution was added to the dispersion liquid, and the reaction was stirred at room temperature. After the solid phase was collected and dried, star-shaped hollow ZIF-8 nanocolumn materials were obtained;

[0033] III. Synthesis of star-shaped hollow nanoreactor:

[0034] The star-shaped hollow ZIF-8 nanocolumn material and the activated material powder were placed at both ends of the crucible, and calcination treatment was carried out at a temperature of 620-750°C under an argon atmosphere. After cooling, a topological star-shaped nanometer hollow reactor (material) was obtained;

[0035] In step one, the mass ratio of Zn(NO3)2·6H2O to 2-methylimidazole was controlled to be (1-1.5):(7-10); the methyl imidazole solution was added to the zinc nitrate solution, and the mass percentage content of cetyltrimethylammonium bromide (CTAB) in the system was 0.4-0.8wt%;

[0036] In step two, the mass ratio of star-shaped ZIF-8 nanocolumn material to tannic acid was (15-25):1.

[0037] The preparation method of the topological star-shaped nanometer hollow reactor of the embodiment includes the following technical features:

[0038] (1) Formation method of novel ZIF-8 structure:

[0039] In the embodiment, by controlling the amount of CTAB (hexadecyl trimethyl ammonium bromide) in the precursor and the ratio of Zn ions to 2-methyl imidazole, a ZIF-8 structure different from the traditional dodecahedron morphology is successfully constructed. This method does not rely on templates, and novel structure design is achieved by adjusting the concentration and ratio of reactants, with the advantages of simple synthesis and strong structure controllability.

[0040] (2) Tannic acid etching to construct hollow cavity structure:

[0041] Tannic acid is used as an etchant to replace the traditional template method to form a hollow cavity structure. This organic acid etching method has the advantages of being green, environmentally friendly and easy to operate, and can more accurately control the morphology and size of the hollow structure, avoiding the complexity of the template removal step in traditional etching.

[0042] (3) In-situ calcination to realize Zn-based composite semiconductor star-shaped topological structure HoNRs:

[0043] The in-situ calcination process is used to further convert the hollow cavity structure into a Zn-based composite star-shaped topological hollow nanoreactor (HoNRs) with semiconductor properties. This in-situ calcination method not only enhances the electrical properties of the material, but also ensures the stability of the complex topological structure at high temperatures, making it have wide application potential in the fields of catalysis, electrochemistry and optoelectronics.

[0044] Specific implementation method two: The difference between this embodiment and specific implementation method one is that in step one, 1-1.5 g of Zn(NO3)2·6H2O and 0.5-2 g of hexadecyl trimethyl ammonium bromide (CTAB) are mixed and dissolved in 35-50 mL of deionized water to obtain a zinc nitrate solution; 7-10 g of 2-methyl imidazole (MeIM) is added to 100-140 mL of deionized water, and after stirring, a methyl imidazole solution is obtained.

[0045] Specific implementation method three: The difference between this embodiment and specific implementation method one or two is that in step one, the methyl imidazole solution is added to the zinc nitrate solution, and the mass percentage content of hexadecyl trimethyl ammonium bromide (CTAB) in the system is 0.5-0.6 wt%.

[0046] Specific implementation method four: The difference between this embodiment and one of specific implementation methods one to three is that in step one, the reaction time is 1.5-3 h at room temperature.

[0047] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that the concentration of the tannic acid aqueous solution in step 2 is 5 mg / mL.

[0048] Specific embodiment 6: The difference between this embodiment and any one of specific embodiments 1 to 5 is that in step 2, the mass ratio of the star-shaped ZIF-8 nanorod material to tannic acid is 20:1.

[0049] Specific embodiment 7: The difference between this embodiment and any one of specific embodiments 1 to 6 is that the stirring reaction time at room temperature in step 2 is 20 to 45 minutes.

[0050] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that the activation material powder in step three is Se powder, sulfur powder or tellurium powder.

[0051] This embodiment uses sulfur powder, tellurium powder, etc. to form zinc-based semiconductor materials such as ZnS and ZnTe. In addition, it can be expanded to different metal-based MOF materials.

[0052] Specific embodiment 9: The difference between this embodiment and any one of specific embodiments 1 to 8 is that in step 3, the mass ratio of the star-shaped hollow ZIF-8 nanorod material and the activation material powder is (0.3-0.8):1.

[0053] Specific embodiment 10: This embodiment differs from any one of specific embodiments 1 to 9 in that the calcination treatment time in step 3 is 1.5 to 3 hours.

[0054] Example: The preparation method of the topological star-shaped nano hollow reactor of this embodiment is achieved by the following steps:

[0055] 1. Synthesis of star-shaped ZIF-8 nanopillars:

[0056] 1.332 g of Zn(NO3)2·6H2O and 1 g of cetyltrimethylammonium bromide (CTAB) were mixed and dissolved in 40 mL of deionized water to obtain a zinc nitrate solution; 8 g of 2-methylimidazole (MeIM) was added to 120 mL of deionized water and stirred vigorously for 3 minutes to obtain a methylimidazole solution, which was (quickly) added to the zinc nitrate solution. The mixture was allowed to react at room temperature for 2 hours, washed several times with deionized water and ethanol, collected by centrifugation at 10,000 rpm, and dried in vacuo at 50°C to obtain a star-shaped ZIF-8 nanopillar material;

[0057] 2. Synthesis of star-shaped hollow topological precursors:

[0058] 200 mg of star-shaped ZIF-8 nanopillar material was added to 30 mL of deionized water, and ultrasonicated at room temperature for 30 minutes to obtain a dispersion. 2 mL of a 5 mg / mL tannic acid aqueous solution was added to the dispersion, and the mixture was stirred at room temperature for 30 minutes. The solid phase was collected and dried at 50°C to obtain a star-shaped hollow ZIF-8 nanopillar material (hS-ZIF-8);

[0059] 3. Synthesis of star-shaped hollow nanoreactors:

[0060] 0.4 g of star-shaped hollow ZIF-8 nanocolumn material and 1.0 g of Se powder were placed at both ends of an alumina crucible. Under an argon environment, the temperature was raised to 650°C at a heating rate of 2°C / min, and the mixture was calcined at 650°C for 2 hours. After naturally cooling to room temperature, a topological star-shaped nanohollow reactor (hC-ZnSe) was obtained.

[0061] In this embodiment, the crystal growth kinetics is controlled by adjusting the synthesis time. After adding a high content of CTAB (>0.16wt%), the crystal growth of the synthesized ZIF-8 crystals (octagonal plates (OP), cross twins (IT) and nanorods (NR)) is closely related to the synthesis kinetics. As for OP crystals, as the synthesis time increases, the lateral size of the crystal increases faster than the crystal thickness, resulting in an increase in the aspect ratio of the OP crystal. The particle size of IT crystals with high symmetry also increases with the extension of the synthesis time. For NR crystals with anisotropic shape, the length increases with the extension of the synthesis time, but the thickness remains almost unchanged. Therefore, the aspect ratio of the NR crystal will increase as the reaction proceeds. The crystal growth rate slows down with the addition of CTAB, which may be due to the competitive interaction between the ligand and surfactant (CTAB) and the metal source (zinc ions).

[0062] The high specific surface area of ​​the star-shaped structure of the topological star-shaped nano hollow reactor prepared in this embodiment exposes more active sites, thereby improving the reaction rate and efficiency. The hollow design enhances the overall structural stability and reduces the risk of structural collapse during use. The multi-stage pores can reduce the diffusion resistance of the reactants, promote rapid mass transfer, and improve the overall reaction efficiency. Through precise control of the geometric shape and size, highly targeted nanoreactors can be designed for efficient catalysis or drug delivery under different reaction conditions, thereby enhancing reaction selectivity and system performance.

[0063] Depend on Figure 4 It can be seen that the nano hollow reactor prepared in this embodiment has a hollow star-shaped topological structure.

[0064] Application Example: In this example, the prepared topological star-shaped nano hollow reactor is used as a photocatalytic material. The experimental process of photocatalysis is as follows:

[0065] In the photocatalytic reduction of CO2, 10 mg of photocatalytic material, 50 mg of [Ru(bpy)3]Cl2·6H2O (abbreviated as Ru, bpy = 2'2-bipyridine), 10 mL of triethanolamine (TEOA), 10 mL of H2O, and 30 mL of acetonitrile (MeCN) were added to a gas-tight glass reactor (with a capacity of 420 mL). After the mixed sample was uniformly ultrasonicated for 15 minutes, it was placed in a light reaction system. Before introducing light irradiation, the light reaction system was thoroughly vacuumed (3 times), and then high-purity CO2 was injected into the inner circulating reactor until the pressure reached 1 atmosphere. Then, high-purity CO2 with a partial pressure of 1 atmosphere was introduced into the reactor. The light source was a 300W Xe lamp (Beijing Perfect Light Source Co., Ltd.) with a 420 nm cutoff filter. The temperature of the reaction system was maintained at 10°C. During the photocatalytic process, the reaction system was vigorously stirred with a magnetic stirrer. After the reaction was completed, the products were quantified using a GC-9790Plus (Zhejiang Fuli Analytical Instrument Co., Ltd.) gas chromatograph.

[0066] As shown in Figure 6 , thanks to a specific surface area as high as 140.5 m 2 g -1 and a pore volume of 3.78 nm sufficient to support the passage of reaction molecules, the CH4 generation rate of the topological star-shaped nanometer hollow reactor was as high as 215.5 μmol·g -1 ·h -1 , and the electron selectivity was as high as 90%. It also had excellent photocatalytic stability Figure 7 . This performance far exceeded most of the reported photocatalysts.

[0067] The topological star-shaped nanometer hollow reactor prepared in this embodiment has unique advantages in the fields of catalysis, medicine, and new energy.

[0068] (1) Effect in the field of catalysis

[0069] The star-shaped hollow topological structure of the nanometer reactor provides a large surface area and a multi-level pore structure, which can significantly improve the exposure rate of active sites and the mass transfer efficiency of reactants in catalytic reactions. This geometry makes it easier for reactants to contact active sites and speeds up reaction rates by reducing diffusion limitations. In addition, since the topological structure of the nanometer reactor can be precisely controlled, the pore size and shape of the reactor can be adjusted for specific reactions, optimizing catalytic performance and improving the selectivity and stability of the catalyst. Therefore, this nanometer reactor has great application potential in the fields of environmental catalysis, petroleum refining, fine chemical industry, etc.

[0070] (2) Effect in the field of medicine

[0071] In the field of medicine, the unique topology of star-shaped hollow nanoreactors provides an ideal platform for drug delivery. The hollow structure not only can load a larger dose of drugs, but also can achieve controlled release of drugs by precise regulation of geometry, thereby improving treatment efficiency and reducing side effects. In addition, the geometric design of this nanoreactor can enhance its biocompatibility and targeting in the body, achieving efficient delivery to specific tissues or cells through topology control. Application scenarios include tumor targeted therapy, precision drug delivery systems, and immunotherapy in frontier fields.

[0072] (3) Effect in the field of new energy

[0073] Star-shaped hollow topology nanoreactors have significant application prospects in new energy technology, especially in electrocatalysis and photocatalysis. Its unique topology can effectively improve the transmission efficiency of electrons and ions, promote reaction activity, and reduce charge recombination. In energy storage devices such as lithium batteries, fuel cells, and supercapacitors, star-shaped hollow structures help improve the energy density, power density, and cycle stability of electrode materials. In the field of photocatalysis, the topological geometry of this nanoreactor helps enhance light absorption capacity and improve the efficiency of photogenerated carrier separation, thereby improving photocatalytic efficiency and being suitable for solar photocatalytic water splitting for hydrogen production, carbon dioxide reduction, and other new energy conversion and storage technologies.

[0074] When expanding star-shaped hollow topology nanoreactors to other MOF materials, the following modification schemes can also be considered:

[0075] (1) Metal-oxo cluster modification: By introducing metal-oxo clusters (such as titanium-oxo clusters, molybdenum-oxo clusters, etc.) on the surface or inside the pores of MOF, its catalytic activity or stability can be enhanced while maintaining the hollow structure. This modification technique is common on MOF materials and is suitable for cases where active sites need to be introduced inside the reactor.

[0076] (2) Alloying and multi-metal doping: By doping multiple metal ions (such as Co-Zn, Cu-Fe, etc.) to construct a heterostructure, the catalytic activity or electron transport performance can be further improved. This alloying strategy can be applied to different MOF materials to enhance their application in new energy and catalysis fields.

[0077] Overall, through fine design and structural regulation of different MOF materials, the manufacturing method of star-shaped hollow topology nanoreactors has strong versatility and modification space, and can be optimized and adjusted according to different application requirements, to realize its potential value in multiple fields.

Claims

1. A method for preparing a topological star-shaped nanohollow reactor, characterized in that The preparation method is realized according to the following steps: I. Synthesis of star-shaped ZIF-8 nanocolumns: Zn(NO3)2·6H2O and hexadecyl trimethyl ammonium bromide are mixed in deionized water to obtain a zinc nitrate solution; 2-methyl imidazole is added to deionized water, and after stirring, a methyl imidazole solution is obtained, which is added to the zinc nitrate solution, and the reaction is allowed to stand at room temperature, and after washing and drying, star-shaped ZIF-8 nanocolumn materials are obtained; II. Synthesis of star-shaped hollow topological precursors: The star-shaped ZIF-8 nanocolumn materials are added to deionized water, and after ultrasonic dispersion, a dispersion liquid is obtained, and a tannic acid aqueous solution is added to the dispersion liquid, and the reaction is stirred at room temperature, and after the solid phase is collected and dried, star-shaped hollow ZIF-8 nanocolumn materials are obtained; III. Synthesis of star-shaped hollow nanoreactors: The star-shaped hollow ZIF-8 nanocolumn materials and activated material powder are placed at both ends of the crucible, and calcination treatment is carried out at a temperature of 620-750°C in an argon environment, and after cooling, topological star-shaped nanometer hollow reactors are obtained; In step I, the mass ratio of Zn(NO3)2·6H2O and 2-methyl imidazole is (1-1.5):(7-10); the methyl imidazole solution is added to the zinc nitrate solution, and the mass percentage content of hexadecyl trimethyl ammonium bromide in the system is 0.4-0.8wt%; In step II, the mass ratio of star-shaped ZIF-8 nanocolumn materials to tannic acid is (15-25):1; and in step III, the activated material powder is Se powder, sulfur powder or tellurium powder.

2. The method for preparing a topological star-shaped nanohollow reactor according to claim 1, characterized in that In step I, 1-1.5g of Zn(NO3)2·6H2O and 0.5-2g of hexadecyl trimethyl ammonium bromide are mixed in 35-50mL of deionized water to obtain a zinc nitrate solution; 7-10g of 2-methyl imidazole is added to 100-140mL of deionized water, and after stirring, a methyl imidazole solution is obtained.

3. The method for preparing the topological star-shaped nano hollow reactor according to claim 1, characterized in that In step I, the methyl imidazole solution is added to the zinc nitrate solution, and the mass percentage content of hexadecyl trimethyl ammonium bromide in the system is 0.5-0.6wt%.

4. The method for preparing the topological star-shaped nano hollow reactor according to claim 1, characterized in that In step I, the reaction is allowed to stand at room temperature for 1.5-3h.

5. The method for preparing the topological star-shaped nano hollow reactor according to claim 1, characterized in that In step II, the mass ratio of star-shaped ZIF-8 nanocolumn materials to tannic acid is 20:

1.

6. The method for preparing the topological star-shaped nano hollow reactor according to claim 1, characterized in that In step II, the reaction is stirred at room temperature for 20-45 minutes.

7. The method for preparing the topological star-shaped nano hollow reactor according to claim 1, characterized in that In step III, the mass ratio of star-shaped hollow ZIF-8 nanocolumn materials to activated material powder is (0.3-0.8):

1.

8. The method for preparing the topological star-shaped nano hollow reactor according to claim 1, characterized in that In step III, the calcination treatment time is 1.5-3 hours.

9. Use of topological star-shaped nanohollow reactors prepared according to claim 1, characterized by The topological star-shaped nanometer hollow reactor is used as a photocatalytic material, an electrocatalytic material or a drug delivery material.

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