A method for growing CNTs on MOF surface by short-term rapid high-temperature thermal shock treatment

Abstract

The present invention relates to a method for growing CNTs on the surface of a MOF using a short, rapid, high-temperature thermal shock treatment. The method comprises: pretreating a carbon substrate; immersing the pretreated carbon substrate in a metal salt solution with a concentration of 0.01 to 1 mol / L; adding a 0.01 to 1 mol / L organic ligand solution, stirring, and then allowing the reaction to proceed at room temperature to form a MOF nanomaterial deposited on the carbon substrate; connecting the two ends of the carbon substrate loaded with the MOF nanomaterial to two electrodes of a direct current power supply; then, under the protection of an inert atmosphere, applying the direct current power supply at a voltage of 15 to 25 V for a duration of 0.5 to 5 seconds. After the reaction is completed, the method cools to room temperature to obtain a carbonized MOF and a small amount of CNTs grown on the surface. The method is simple in process, requires minimal raw materials, and is low in cost. CNTs grow in situ on the carbonized MOF surface with a rapid growth rate and a randomly distributed growth direction.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of carbon nanomaterials, and relates to a method for growing CNTs on the surface of MOF by short-time rapid high-temperature thermal shock treatment. Background Art

[0002] Carbon nanotubes (CNTs) possess large surface area, high electrical conductivity, and excellent structural stability and mechanical properties, making them widely used in composite material strengthening, electromagnetic shielding, and energy storage and conversion. Metal-organic frameworks (MOFs) are porous materials formed by self-assembly of metal ions or clusters with organic ligands through coordination bonds. In recent years, nanocarbon materials prepared using MOFs as precursors or catalysts have shown promising application prospects in energy storage and conversion.

[0003] Methods for preparing CNTs on MOF surfaces are generally divided into two categories. One is to use the carbon-containing small molecules released by MOF pyrolysis as a carbon source to generate CNTs in situ (Paper 1 "Journal of the American Chemical Society, 2017, 139(24):8212-8221"); the other method is to use MOF as a catalyst and grow CNTs by adding a gaseous (methane) or solid (urea, melamine, etc.; Patent 1 "CN110518261B", Patent 2 "CN113809286A") carbon source. However, the former method requires a long heat treatment time and fine process control, while the latter method is complex and tedious, often requiring multiple reactions and high costs. Few people have studied how to simply and quickly prepare CNTs on MOF surfaces. Summary of the Invention

[0004] This invention overcomes the shortcomings of traditional methods for preparing carbon nanocatalytic materials and provides a method for growing CNTs on MOF surfaces using a short, rapid, high-temperature thermal shock treatment. The invention features a simple preparation process, requires minimal raw materials, is low-cost, and boasts rapid CNT growth, strong universality, and high reproducibility. The CNTs prepared in this invention grow in situ on the carbonized MOF surface with a random growth direction, increasing the specific surface area of ​​the substrate. Furthermore, the CNTs exhibit strong bonding to the substrate and a stable structure.

[0005] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0006] A method for growing CNTs on the surface of MOF by a short-term, rapid, high-temperature thermal shock treatment, comprising:

[0007] 1. Carbon substrate pretreatment: The carbon substrate was ultrasonically cleaned three times with deionized water, acetone, and anhydrous ethanol, respectively, and dried in a 60-100°C oven for 6-12 hours. The dried carbon substrate was placed in a concentrated nitric acid solution and placed in a 40-80°C water bath for 6-12 hours. After removal, it was washed with a large amount of deionized water until the surface pH of the carbon substrate was neutral, and then dried in a 60-100°C oven for 6-12 hours.

[0008] 2. Preparation of MOF: Prepare a metal salt solution with a concentration of 0.01 to 1 mol / L, and then soak the substrate in the above solution for 1 to 12 hours; prepare an organic ligand solution with a concentration of 0.01 to 1 mol / L, and then quickly add it to the metal salt solution and stir rapidly for 30 to 60 seconds; let it react at room temperature for 1 to 24 hours, remove the sample, wash it with water and anhydrous ethanol several times, and dry it in a 60 to 100 ° C oven to deposit the MOF nanomaterial on the carbon substrate;

[0009] III. Carbonization of MOF and Preparation of CNTs: Connect the two ends of a carbon substrate loaded with MOF nanomaterials to the two electrodes of a DC power supply. Then, under an argon atmosphere, apply the DC power supply at a voltage of 15-25V for 0.5-5 seconds. After the reaction is complete and cooled to room temperature, carbonized MOF and a small amount of CNTs grown on the surface are obtained. During the reaction, a small amount of gaseous carbon source can be introduced, resulting in the growth of a large number of CNTs on the MOF surface.

[0010] Preferably, the carbon substrate described in step 1 is selected from but not limited to: carbon fiber bundles, carbon fiber cloth, carbon fiber paper, carbon fiber felt, graphite paper, graphite sheet, graphene film, graphene foam, graphene aerogel, carbon nanotube paper, carbon nanotube sponge, electrospun carbon nanofiber membrane or carbon / carbon composite material sheet.

[0011] Preferably, the metal salt in step 2 is one or more of the following combinations, but is not limited to: cobalt nitrate, ferric nitrate, nickel nitrate, ferrous sulfate, cobalt sulfate, nickel sulfate, ferric chloride, cobalt chloride, and nickel chloride.

[0012] Preferably, the organic ligand in step 2 is one or more of the following combinations, but is not limited to: 2-methylimidazole, 1,3,5-benzenetricarboxylic acid, terephthalic acid, phthalic acid, and fumaric acid.

[0013] Preferably, the solvent for the metal salt and the organic ligand in step 2 is a combination of one or more of the following, but not limited to: water, ethanol, methanol, N,N-dimethylformamide, isopropanol, and ethylene glycol.

[0014] Preferably, the MOF described in step 2 includes but is not limited to: Co-MOF, Fe-MOF, Ni-MOF, NiCo-MOF, CoFe-MOF, NiFe-MOF, and NiCoFe-MOF.

[0015] Preferably, the MOF morphology described in step 2 includes but is not limited to: nanosheet arrays, nanowire arrays, nanoparticles, and micron particles.

[0016] Preferably, the carbon source required for the growth of CNTs in step 3 includes but is not limited to: acetylene, propane, methane, propylene, and ethylene.

[0017] This method uses Joule heating to rapidly heat-shock MOFs for a short period of time, achieving both rapid carbonization of the MOF and rapid growth of CNTs. By adjusting the carbon source, varying amounts of CNTs can be grown. This method offers a simple preparation process, rapid CNT growth, and strong versatility, providing a new technology and method for growing CNTs on MOF surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings in the specification, which constitute a part of this application, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0019] In the attached figure:

[0020] Figure 1 This is a SEM characterization image of the carbon cloth@Co-MOF array prepared by the present invention;

[0021] Figure 2 This is a low-magnification SEM characterization image of CNTs grown on the surface of the carbon cloth@Co-MOF array prepared by the present invention;

[0022] Figure 3 This is a high-magnification SEM characterization image of CNTs grown on the surface of the carbon cloth@Co-MOF array prepared by the present invention;

[0023] Figure 4 This is a SEM characterization image of the carbon cloth@Co-MOF nanoparticles prepared by the present invention;

[0024] Figure 5 This is a SEM characterization image of CNTs grown on the surface of carbon cloth@Co-MOF nanoparticles prepared in the present invention. DETAILED DESCRIPTION

[0025] In order to more clearly understand the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0026] The present invention provides a method for growing CNTs on the surface of MOF by treating it with a short-term rapid high-temperature thermal shock.

[0027] The Joule heating method quickly heats the carbon substrate sample, and simultaneously achieves rapid carbonization of MOF and rapid growth of CNTs, overcoming the shortcomings of the traditional method of preparing CNTs on the MOF surface, such as long preparation time and complex process. The method of the present invention first prepares MOF on a carbon-based conductive substrate. MOF serves as both a substrate for CNT growth and a catalyst for CNT growth. In this technical solution, by regulating parameters such as DC power supply voltage, reaction time and carbon source, uniform growth of CNTs on the MOF surface can be achieved in a short time. A large number of CNTs are grown on the MOF substrate.

[0028] In situ growth, the growth direction is randomly distributed, and they cross each other to form a three-dimensional network structure, which increases the specific surface area of ​​the substrate; in addition, the bonding force between CNTs and the substrate is good and the structure is stable.

[0029] Example 1:

[0030] 1. Carbon substrate pretreatment: The carbon fiber cloth substrate was ultrasonically cleaned 3 times with deionized water, acetone, and anhydrous ethanol respectively, and then dried in a 60℃ oven for 6 hours; the dried carbon fiber cloth was placed in a concentrated nitric acid solution.

[0031] The carbon substrate was placed in a 60°C water bath for 12 h, washed with plenty of deionized water until the pH value of the carbon substrate surface was neutral, and dried in a 60°C oven for 12 h.

[0032] 2. Preparation of MOF: Prepare a 0.06 mol / L aqueous solution of Co(NO3)2, and then soak the carbon fiber cloth in the above solution for 3 hours; prepare a 0.5 mol / L aqueous solution of 2-methylimidazole, and then quickly add it to the Co(NO3)2 aqueous solution and stir rapidly for 30 seconds; let it react at room temperature for 4 hours, remove the sample, wash it with water and anhydrous ethanol several times, and dry it in a 60°C oven. Deposit the Co-MOF array on the carbon fiber cloth substrate;

[0033] 3. Carbonization of MOF and preparation of CNTs: Connect the two ends of the carbon fiber cloth loaded with Co-MOF array to the two electrodes of a DC power supply. Then, under the protection of an argon atmosphere, turn on the DC power supply with a voltage of 20V and a duration of 0.5s. After the reaction is completed, cool it to room temperature to obtain carbonized Co-MOF and a small amount of CNTs grown on the surface.

[0034] Example 2:

[0035] 1. Carbon substrate pretreatment: The carbon fiber cloth substrate was ultrasonically cleaned three times with deionized water, acetone, and anhydrous ethanol, and dried in an 80°C oven for 8 hours. The dried carbon fiber cloth was placed in a concentrated nitric acid solution and placed in a 50°C water bath for 8 hours. After removal, it was washed with a large amount of deionized water until the surface pH of the carbon substrate was neutral, and then dried in an 80°C oven for 8 hours.

[0036] 2. Preparation of MOF: Prepare a 0.08 mol / L aqueous solution of Co(NO3)2, and then soak the substrate in the above solution for 2 hours; prepare a 0.6 mol / L aqueous solution of 2-methylimidazole, and then quickly add it to the Co(NO3)2 aqueous solution and stir rapidly for 60 seconds; let it react at room temperature for 6 hours, remove the sample, wash it with water and anhydrous ethanol several times, place it in an 80°C oven to dry, and deposit it on a carbon fiber cloth substrate to obtain a Co-MOF array;

[0037] 3. Carbonization of MOF and preparation of CNTs: Connect the two ends of the carbon fiber cloth loaded with Co-MOF array to the two electrodes of a DC power supply. Then, under the protection of an argon atmosphere, introduce a small amount of acetylene. Turn on the DC power supply with a voltage of 18V for 2s. After the reaction is completed, cool it to room temperature to obtain carbonized Co-MOF and a large number of CNTs grown on the surface.

[0038] Example 3:

[0039] 1. Carbon substrate pretreatment: The graphite paper substrate was ultrasonically cleaned three times with deionized water, acetone, and anhydrous ethanol, and dried in a 70°C oven for 7 hours. The dried graphite paper was placed in a concentrated nitric acid solution and placed in an 80°C water bath for 7 hours. After removal, it was washed with a large amount of deionized water until the surface pH of the graphite paper was neutral, and then dried in a 70°C oven for 7 hours.

[0040] 2. Preparation of MOF: Prepare a 0.1 mol / L Co(NO3)2 methanol solution, then soak the substrate in the solution for 6 hours; prepare a 0.5 mol / L 2-methylimidazole methanol solution, then quickly add it to the metal salt solution and stir rapidly for 60 seconds; let it react at room temperature for 24 hours, remove the sample, wash it with water and anhydrous ethanol several times, dry it in a 70°C oven, and deposit Co-MOF particles on a graphite paper substrate;

[0041] 3. Carbonization of MOF and preparation of CNTs: Connect the two ends of the graphite paper substrate loaded with Co-MOF particles to the two electrodes of a DC power supply. Then, under the protection of an argon atmosphere, introduce a small amount of propylene. Turn on the DC power supply with a voltage of 15V for 3s. After the reaction is completed, cool it to room temperature to obtain carbonized Co-MOF and a large number of CNTs grown on the surface.

[0042] Example 4:

[0043] 1. Carbon substrate pretreatment: The graphene film substrate was ultrasonically cleaned three times with deionized water, acetone, and anhydrous ethanol, respectively, and dried in an 80°C oven for 6 hours. The dried carbon substrate was placed in a concentrated nitric acid solution and placed in a 60°C water bath for 12 hours. After removal, it was washed with a large amount of deionized water until the pH value of the graphene film surface was neutral, and then dried in an 80°C oven for 10 hours.

[0044] 2. Preparation of MOF: Prepare a 0.05 mol / L Ni(NO3)2 aqueous solution, then soak the substrate in the solution for 5 hours; prepare a 0.4 mol / L 2-methylimidazole aqueous solution, then quickly add it to the Ni(NO3)2 aqueous solution and stir rapidly for 50 seconds; let it react at room temperature for 12 hours, remove the sample, wash it with water and anhydrous ethanol several times, dry it in a 70°C oven, and deposit Ni-MOF nanomaterials on the graphene membrane substrate;

[0045] 3. Carbonization of MOF and preparation of CNTs: Connect the two ends of the graphene membrane substrate loaded with Ni-MOF nanomaterials to the two electrodes of a DC power supply. Then, under the protection of an argon atmosphere, introduce a small amount of methane. Turn on the DC power supply with a voltage of 25V and a duration of 0.5s. After the reaction is completed, cool it to room temperature to obtain carbonized Ni-MOF and a large number of CNTs grown on the surface.

[0046] Figure 1 This is an SEM characterization image of the carbon fiber cloth@Co-MOF array prepared in Example 1 of the present invention. It can be clearly seen that a large number of Co-MOF nanosheets grow vertically on the carbon fiber surface; the nanosheets have a smooth surface and a solid structure inside; the nanosheets support each other to form an array. Figure 2 This is a low-magnification SEM characterization image of CNTs grown on the surface of the carbon cloth @ Co-MOF array prepared in Example 1 of the present invention. It can be seen from the image that after the Co-MOF array is subjected to a short-term rapid high-temperature thermal shock treatment, the nanosheets are carbonized and the surface becomes rough, but the array structure can still be maintained intact. Moreover, the high-magnification SEM characterization image of CNTs grown on the surface of the carbon cloth @ Co-MOF array prepared in Example 1 of the present invention ( Figure 3 ) It can be observed that a large number of CNTs grow in situ and uniformly on the surface of Co-MOF nanosheets. Figure 4 This is the SEM characterization of the carbon fiber cloth @ Co-MOF nanoparticles prepared in Example 1 of the present invention. It can be clearly seen that a large number of Co-MOF nanoparticles are evenly distributed and grown on the carbon fiber surface. After a short period of rapid high-temperature thermal shock treatment, Figure 5From the SEM characterization diagram, it can be seen that a large number of CNTs grow on the MOF surface, with random distribution in the growth direction and cross-linking to form a three-dimensional network structure, increasing the specific surface area of ​​the substrate.

[0047] The method of the present invention achieves efficient carbonization of MOFs and rapid in-situ growth of CNTs through high-temperature thermal shock treatment, achieving uniform CNT growth on the MOF surface. This technical solution offers simple operation, controllable process, low raw material usage, low cost, rapid CNT growth, strong universality, and reproducibility. The resulting MOF-derived CNTs have broad application prospects in various fields, particularly in nano-enhancement and catalysis.

Claims

1. A method for growing CNTs on a MOF surface by a short, rapid, high-temperature thermal shock treatment, comprising: (1) Carbon substrate pretreatment: Place the carbon substrate in concentrated nitric acid solution and place it in a water bath at 40-80°C, then wash with water until the surface pH of the carbon substrate is neutral and dry it; (2) Preparation of MOF: Soak the pretreated carbon substrate in a metal salt solution with a concentration of 0.01 to 1 mol / L; quickly add an organic ligand solution with a concentration of 0.01 to 1 mol / L, stir, and then allow to react at room temperature. After the reaction, remove the carbon substrate, wash, and dry it to obtain a carbon substrate with MOF nanomaterials deposited on it; (3) Carbonization of MOF and preparation of CNTs: Connect the two ends of the carbon substrate loaded with MOF nanomaterials to the two electrodes of a DC power supply. Then, under the protection of an inert atmosphere, turn on the DC power supply with a voltage of 15 to 25 V for 0.5 to 5 s. After the reaction is completed, cool to room temperature to obtain carbonized MOF and a small amount of CNTs grown on the surface. wherein the metal salt is cobalt nitrate or nickel nitrate, and the solvent of the metal salt solution is water or methanol; wherein the organic ligand is 2-methylimidazole, and the solvent of the organic ligand solution is water or methanol; Wherein the carbon substrate is carbon fiber cloth, graphite paper or graphene film; The MOF is Co-MOF or Ni-MOF.

2. The method according to claim 1, wherein the MOF morphology is in the form of nanosheet arrays, nanowire arrays, nanoparticles or microparticles.

3. The method according to claim 1, wherein in step (2), the carbon substrate is immersed in the metal salt solution for 1 to 12 hours, and the static reaction time at room temperature after stirring is 1 to 24 hours.

4. The method according to claim 1, wherein the carbon substrate is treated in a concentrated nitric acid solution in a water bath for 6 to 12 hours.

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