Porous polydopamine confinement MOF (Metal Organic Framework) nanosphere as well as preparation method and application thereof

Abstract

The invention discloses a porous polydopamine confinement MOF nanosphere and a preparation method and application thereof, and belongs to the field of material chemistry and nanotechnology, and the preparation method comprises the following steps: (1) synthesizing a mesoporous PDA-F127 nanosphere; (2) mixing the nanospheres obtained in the step (1) with an aluminum salt and an organic ligand in a solvent, and synthesizing an MOF-PDA-F127 composite material through a hydrothermal reaction; and (3) performing high-temperature carbonization treatment on the product in the step (2) to obtain the porous polydopamine confinement MOF nanospheres. The MOF-PDA-F127 nanosphere composite structure obtained by the invention has the characteristics of MOF size confinement, uniform distribution, excellent conductivity, good cycling stability and the like.

Description

Technical Field

[0001] The present invention belongs to the field of materials chemistry and nanotechnology, and specifically relates to a composite material, a preparation method and an application thereof, and more particularly to a composite material in which a micro-nano metal organic framework (MOF) is confined in the pores of porous polydopamine (PDA) nanospheres, a preparation method thereof, and an application thereof in zinc ion negative electrode materials. Background Art

[0002] Metal-Organic Frameworks (MOFs) are porous crystalline materials formed by the self-assembly of metal ions or clusters and organic ligands through coordination bonds. They have the characteristics of high specific surface area, adjustable pore size and chemical functionalization ability, and have attracted much attention in the fields of gas adsorption, catalysis, drug delivery and energy storage. For example, in the field of energy storage, the porous structure of MOFs can accommodate ion insertion / extraction, which can theoretically alleviate the volume expansion problem of electrode materials and thus improve battery cycle stability. However, the practical application of MOFs materials still faces two major challenges: first, the nanoparticles are prone to agglomeration, resulting in a reduction in effective specific surface area and pore blockage; second, their intrinsic conductivity is poor, which limits the electrochemical performance.

[0003] In the prior art, researchers have attempted to improve the dispersibility and conductivity of MOFs through various approaches. For example, a Chinese patent with publication number CN113629230A discloses a method for preparing a negative electrode material for lithium-ion batteries, which uses carbon coating technology to improve the conductivity of the material. However, the process does not involve the confined dispersion of MOFs, resulting in the problem of particle agglomeration during the cycle of the material. Another patent with publication number CN107369825A proposes a method for preparing a nitrogen-doped carbon-coated manganese oxide composite negative electrode material, which forms a carbon layer on the surface of manganese oxide by chemical vapor deposition. However, this method does not deeply optimize the loading and interface bonding strength of MOFs, which may affect the long-term stability of the composite material.

[0004] In response to the dispersibility problem of MOFs, porous carrier confinement strategies have been widely studied. For example, mesoporous silica or carbon materials can load MOFs by physical adsorption, but their surface chemical inertness leads to weak interaction with MOFs, and high-temperature calcination or strong acid etching processes increase the preparation cost (such as the template method used to prepare porous carbon-MOF composites in CN113666411B). In recent years, polydopamine (PDA) has become a research hotspot for MOFs confinement carriers due to its biomimetic adhesion and rich surface functional groups (such as amino and hydroxyl groups). PDA can form a uniform nanosphere structure through self-polymerization, and its surface functional groups can coordinate with metal ions to promote the in situ growth of MOFs. In addition, PDA can be converted into nitrogen-doped carbon materials with excellent conductivity after carbonization, further improving the electrochemical properties of the composite material.

[0005] However, the preparation of existing PDA-based composite materials still faces the following technical bottlenecks: (1) The pore size distribution of PDA nanospheres is uneven, resulting in limited and random distribution of MOFs loading. For example, the template method used in CN113666411B relies on complex etching steps, making it difficult to accurately control the mesopore size; (2) The interfacial bonding strength between MOFs and PDA is insufficient, and structural collapse is prone to occur during the cycle; (3) There is a lack of systematic optimization of carbonization process parameters. For example, a carbonization temperature that is too high (>900°C) may cause the destruction of the MOFs crystal structure, while a temperature that is too low (<600°C) may fail to form a continuous conductive network, affecting the overall performance of the material.

[0006] In summary, the existing technology has not yet effectively solved the problems of uniform dispersion, strong interfacial bonding, and synergistic improvement of conductivity of MOFs in carriers. Based on this, the present invention proposes a method for preparing porous polydopamine-confined MOF nanospheres. By introducing triblock copolymer F127 as a soft template to regulate the mesoporous structure of PDA nanospheres, combined with step-by-step hydrothermal synthesis and gradient carbonization process, the uniform dispersion and stable loading of MOFs in the carrier pores are achieved. This method not only avoids the agglomeration problem of MOFs, but also significantly improves the conductivity of the composite material through nitrogen doping during the carbonization process, providing a reliable technical solution for the development of high-performance energy storage devices. Summary of the Invention

[0007] Technical Problem Solved: This invention provides porous polydopamine-confined MOF nanospheres, their preparation method, and applications. This method enables the MOF material to be evenly dispersed within the pores of the PDA nanospheres, improving the MOF's dispersibility while maintaining its excellent performance.

[0008] Technical solution: A method for preparing porous polydopamine confined MOF nanospheres, comprising the following steps: (1) synthesizing mesoporous PDA-F127 nanospheres: dissolving polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127) and dopamine (DA) in a mixed solvent of water and ethanol at a mass ratio of 1.5:1 to 4:1, adding trimethylbenzene (TMB) to form a nanoemulsion system, then adding ammonia water to make the solution pH value not less than 11 to induce dopamine self-polymerization, and obtaining mesoporous PDA-F127 nanospheres through centrifugation, washing and freeze-drying; (2) mixing the nanospheres obtained in step (1) with aluminum salt and organic ligand in a solvent, and synthesizing MOF-PDA-F127 composite materials through hydrothermal reaction; (3) subjecting the product of step (2) to high-temperature carbonization treatment to obtain porous polydopamine confined MOF nanospheres.

[0009] The volume ratio of water, ethanol and TMB in the mixed solvent in step (1) is 5:5:1, and the mass ratio of F127 to DA is 2:1.

[0010] In step (2), the aluminum salt is at least one of aluminum nitrate, aluminum chloride, and aluminum sulfate; the organic ligand is terephthalic acid; the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and pyrrolidone; the hydrothermal reaction temperature is 100-120° C., and the reaction time is 12-24 hours.

[0011] The high-temperature carbonization treatment in step (3) includes: preheating at 350°C for 3 hours, then heating to 700-900°C at a heating rate of 2°C / min under a nitrogen atmosphere, and keeping warm for 2 hours.

[0012] The freeze-drying temperature in step (1) is -50°C to -80°C, and the drying time is 24-48 hours.

[0013] The porous polydopamine confined MOF nanospheres prepared by the above method, (a) the average particle size of the PDA nanospheres is 145nm, and the surface has a uniformly distributed mesoporous structure; (b) the MOF is MIL-53(Al), which has a stick-like structure, a length of 40-50nm, a width of 8-12nm, and is uniformly dispersed in the pores of the PDA nanospheres.

[0014] Application of the above composite materials in energy storage devices.

[0015] The above energy storage device includes a zinc ion battery, a lithium ion battery or a supercapacitor.

[0016] A zinc ion battery negative electrode material comprises the above composite material.

[0017] The composite material is prepared by the above method.

[0018] Beneficial Effects: This invention provides a composite nanomaterial of MIL-53(Al) and mesoporous PDA-F127 nanospheres, as well as its preparation method and application. The method utilizes a mesoporous nanosphere synthesis-MOF material in-situ composite-carbonization process. The resulting MOF-PDA-F127 nanosphere composite structure exhibits MOF size confinement, uniform distribution, excellent conductivity, and good cycling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the X-ray diffraction pattern of the composite material of MIL-53(Al) and mesoporous PDA-F127 nanospheres obtained in Example 1.

[0020] Figure 2 This is a scanning electron microscope image of the composite material of MIL-53(Al) and mesoporous PDA-F127 nanospheres obtained in Example 1.

[0021] Figure 3 This is a transmission electron microscopy image of the MIL-53(Al) and mesoporous PDA-F127 nanosphere composite material obtained in Example 1.

[0022] Figure 4 This is a cycle performance diagram of the composite material of MIL-53(Al) and mesoporous PDA-F127 nanospheres obtained in Example 1 for application as zinc ion negative electrode material. DETAILED DESCRIPTION

[0023] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] Example 1

[0025] (1) 1.0 g F127 and 0.5 g DA were dissolved in 100 mL of a mixture of water and ethanol in a volume ratio of 1:1 and stirred at room temperature to obtain a clear solution. 2.0 mL of TMB was then injected into the solution at a stirring speed of 500 rpm to form a nanoemulsion system. After stirring for 30 min, 5.0 mL of NH4OH was dropped into the above mixture to induce self-polymerization of dopamine oligomers. After continuous reaction for 24 h, the formed product was centrifuged and washed with water and ethanol in sequence for at least three times. Finally, mesoporous PDA-F127 nanospheres were obtained by freeze drying.

[0026] (2) 20 mg of mesoporous PDA-F127 nanospheres, 67.5 mg of aluminum nitrate nonahydrate, and 20.38 mg of terephthalic acid were added to 20 mL of DMF solution, mixed and stirred, and hydrothermally reacted at 110°C for 24 h. The resulting product was centrifuged, washed at least three times with DMF solution, and then freeze-dried to obtain the target product MIL-53(Al)-F127.

[0027] (3) MIL-53(Al)-F127 powder was heated at 350 °C for 3 h and then at 700 °C for 2 h in N2 atmosphere at a heating rate of 2 °C min -1 After the material is cooled to room temperature, it is collected to obtain MIL-53(Al)-F127-700.

[0028] Figure 1 The XRD pattern of the composite material of MIL-53(Al) and mesoporous PDA-F127 nanospheres is shown below. The composite material exhibits broad diffraction peaks at the same positions as pure PDA-F127. Furthermore, the peak near 9.3° corresponds to the standard peak of MIL-53, indicating that the composite structure is a composite of MIL-53(Al) and mesoporous PDA-F127 nanospheres.

[0029] Figure 2 This is a scanning electron microscope image of the composite material of MIL-53 (Al) and mesoporous PDA-F127 nanospheres, which shows that the composite material has a small size, good dispersion, and the nanospheres are uniform in size.

[0030] Figure 3 This transmission electron micrograph shows a composite of MIL-53(Al) and mesoporous PDA-F127 nanospheres. The carrier's morphology is a nanosphere structure, approximately 145 nm in size, with evenly distributed mesopores on the surface. The MIL-53(Al) exhibits a stick-like structure, approximately 45 nm long and 10 nm wide, evenly distributed within the pores on the surface of the mesoporous nanospheres.

[0031] In summary, the preparation method of the MIL-53 (Al) and mesoporous PDA-F127 nanosphere composite material of the present invention has a uniform size and morphology, good dispersibility, high durability to zinc ion negative electrode reaction, and is of great significance for promoting the practical application of aqueous zinc ion batteries.

[0032] Performance evaluation: Figure 4 The cycling performance test was conducted after the MIL-53 (Al) and mesoporous PDA-F127 nanosphere composite material was assembled into an electrode sheet, which showed that the composite material had a cycling stability of more than 400 hours when acting on the negative electrode of zinc ion batteries.

[0033] Example 2

[0034] According to the process flow (same as Example 1), 20 mg of mesoporous PDA-F127 nanospheres, 33.75 mg of aluminum nitrate nonahydrate and 10.19 mg of terephthalic acid were added to 20 mL of DMF solution, mixed and stirred evenly, and hydrothermally reacted at 110° C. for 24 h.

[0035] The MIL-53(Al) and mesoporous PDA-F127 nanosphere composite material prepared according to the above process flow has a small-sized nanosheet structure and is evenly loaded on the mesoporous nanospheres. The composite material has uniform size and morphology and good dispersion. The material also exhibits a cycle stability of more than 350 hours when used as the negative electrode of a zinc-ion battery.

[0036] Example 3

[0037] According to the process flow (same as Example 1), 20 mg of mesoporous PDA-F127 nanospheres, 135 mg of aluminum nitrate nonahydrate and 40.76 mg of terephthalic acid were added to 20 mL of DMF solution, mixed and stirred evenly, and hydrothermally reacted at 110° C. for 24 h.

[0038] The MIL-53(Al) and mesoporous PDA-F127 nanosphere composite material prepared according to the above process flow has a nanosheet structure and is evenly loaded on the mesoporous nanospheres. The composite material has uniform size and morphology and good dispersion. The material also exhibits a cycle stability of more than 350 hours when used as the negative electrode of a zinc ion battery.

[0039] Example 4

[0040] The MIL-53(Al)-F127 powder was heated at 350 °C for 3 h and subsequently at 600 °C for 2 h under N2 atmosphere with a heating rate of 2 °C min -1 After the material is cooled to room temperature, it is collected to obtain MIL-53(Al)-F127-600.

[0041] The MIL-53(Al) and mesoporous PDA-F127 nanosphere composite material prepared according to the above process flow has a nanosheet structure and is evenly loaded on the mesoporous nanospheres. The composite material has uniform size and morphology and good dispersion. The material also exhibits a cycle stability of more than 300 hours when used as the negative electrode of a zinc ion battery.

[0042] Example 5

[0043] The MIL-53(Al)-F127 powder was heated at 350 °C for 3 h and subsequently at 800 °C for 2 h under N2 atmosphere with a heating rate of 2 °C min -1 After the material is cooled to room temperature, it is collected to obtain MIL-53(Al)-F127-800.

[0044] The MIL-53(Al) and mesoporous PDA-F127 nanosphere composite material prepared according to the above process flow has a nanosheet structure and is evenly loaded on the mesoporous nanospheres. The composite material has uniform size and morphology and good dispersion. The material also exhibits a cycle stability of more than 300 hours when used as the negative electrode of a zinc ion battery.

[0045] The above embodiments are intended to describe preferred embodiments of the present invention and are not intended to limit the present invention. Without departing from the spirit or scope of the present invention, technical improvements and equivalent substitutions made by relevant technicians to the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing porous polydopamine confined MOF nanospheres, characterized in that: The following steps are involved: (1) Synthesis of mesoporous PDA-F127 nanospheres: polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127) and dopamine (DA) are dissolved in a mixed solvent of water and ethanol at a mass ratio of 1.5:1 to 4:1, and trimethylbenzene (TMB) is added to form a nanoemulsion system. Ammonia water is then added to make the pH value of the solution not less than 11 to induce dopamine self-polymerization. Mesoporous PDA-F127 nanospheres are obtained by centrifugation, washing and freeze-drying; (2) the nanospheres obtained in step (1) are mixed with aluminum salt and organic ligand in a solvent, and a MOF-PDA-F127 composite material is synthesized by hydrothermal reaction; (3) the product of step (2) is subjected to high-temperature carbonization treatment to obtain porous polydopamine confined MOF nanospheres.

2. The preparation method according to claim 1, characterized in that The volume ratio of water, ethanol and TMB in the mixed solvent in step (1) is 5:5:1, and the mass ratio of F127 to DA is 2:

1.

3. The preparation method according to claim 1, characterized in that In step (2), the aluminum salt is at least one of aluminum nitrate, aluminum chloride, and aluminum sulfate; the organic ligand is terephthalic acid; the solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and pyrrolidone; the temperature of the hydrothermal reaction is 100-120° C., and the reaction time is 12-24 hours.

4. The preparation method according to claim 1, characterized in that The high-temperature carbonization treatment in step (3) includes: preheating at 350°C for 3 hours, then heating to 700-900°C at a heating rate of 2°C / min under a nitrogen atmosphere, and keeping the temperature for 2 hours.

5. The preparation method according to claim 1, characterized in that The freeze-drying temperature in step (1) is -50°C to -80°C, and the drying time is 24-48 hours.

6. A porous polydopamine confined MOF nanosphere prepared according to the method of any one of claims 1 to 5, characterized in that: (a) The average particle size of the PDA nanospheres is 145 nm, and the surface has a uniformly distributed mesoporous structure; (b) The MOF is MIL-53(Al), which has a stick-like structure with a length of 40-50 nm and a width of 8-12 nm, and is uniformly dispersed in the pores of the PDA nanospheres.

7. Use of the composite material according to claim 6 in an energy storage device.

8. The use according to claim 7, characterized in that The energy storage device includes a zinc ion battery, a lithium ion battery or a supercapacitor.

9. A zinc ion battery negative electrode material, characterized in that The composite material according to claim 6.

10. The zinc ion battery negative electrode material according to claim 9, characterized in that The composite material is prepared by the method according to any one of claims 1 to 5.

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