Dispersible mesoporous carbon spheres and preparation method thereof

Abstract

The invention belongs to the technical field of carbon material preparation, and particularly relates to a dispersible mesoporous carbon sphere and a preparation method thereof. According to the invention, through a one-pot and two-step silicon adding process, the monodisperse SiO2 layer coated polymer-SiO2 composite sphere with uniform and controllable size is synthesized under a low-temperature condition. According to the present invention, the SiO2 can simultaneously achieve the dual effects of pore forming and spatial separation, and the SiO2 layer can prevent the cross-linking agglomeration of the mesoporous carbon sphere during the heat treatment process, such that the SiO2 layer-coated polymer-SiO2 composite sphere is subjected to the heat treatment carbonization and silica removal process so as to obtain the monodisperse and uniform-size dispersible mesoporous carbon sphere;

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon material preparation, and particularly relates to a dispersible mesoporous carbon sphere and a preparation method thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Mesoporous carbon nanospheres have the advantages of high specific surface area, adjustable pore structure, stable physical and chemical properties, and good biocompatibility, and are widely used in the fields of biomedicine, catalytic separation, adsorption, etc. ( Nat. Mater. 2015, 14 ,763-774; Adv. Mater. 2020, 32 , 2002475). Especially in the field of biomedicine, high-quality mesoporous carbon nanospheres can be used as tracers and drug carriers to realize the diagnosis and treatment of tumor tissues / cells (Carbon2016, 101 , 135-142, Nat. Rev. Drug Discov. 2021, 20 , 101-124). At present, using phenolic compounds as raw materials, through the template method, polymer nanospheres are synthesized through a hydrothermal process, and then mesoporous carbon spheres can be obtained by high-temperature pyrolysis and removal of the template. However, the hydrothermal process requires a relatively high temperature, which is difficult to scale up production, and the size of the polymer spheres is difficult to control (especially when the size is <200 nm). In addition, direct pyrolysis of the polymer spheres will cause the generated carbon spheres to adhere / aggregate to each other, and cannot form dispersible mesoporous carbon spheres in the solvent. To solve this problem, the traditional strategy is to coat a protective layer (usually SiO 2 layer) on the surface of the polymer spheres, and through spatial separation, inhibit the mutual adhesion of the carbon spheres during the carbonization process ( Angew. Chem. Int. Ed. 2011, 50, 11765-11768). However, this process often requires centrifugal separation of the synthesized polymer spheres first (the smaller the size, the more difficult to separate, >10000 rpm), followed by washing, surface modification / or adding a large amount of surfactant to achieve silicon layer coating, and then centrifugal separation again to obtain the final polymer-SiO 2 composite spheres, which makes the process route long and the operation cumbersome, resulting in increased costs and affecting the large-scale production of products. Summary of the Invention

[0004] In order to solve the deficiencies of the prior art, the object of the present invention is to provide a dispersible mesoporous carbon sphere and a preparation method thereof. The present invention synthesizes monodisperse and uniformly controllable SiO through a one-pot two-step silicon addition process under low-temperature conditions.2 Layer-coated polymer-SiO 2 Composite spheres. SiO 2 Simultaneously achieve the dual functions of pore formation and spatial separation, and during the heat treatment process, the SiO 2 layer can prevent the cross-linking and agglomeration of mesoporous carbon spheres. Therefore, the SiO 2 layer-coated polymer-SiO 2 Composite spheres undergo heat treatment carbonization and silicon removal processes to obtain monodisperse and uniformly sized dispersible mesoporous carbon spheres.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: In a first aspect, the present invention provides a method for preparing dispersible mesoporous carbon spheres, comprising the following steps: S1. Mix a silicon precursor, a hydroxy-containing aromatic compound, an aldehyde compound, a base, and a solvent, and perform a primary polymerization. After the reaction, add the silicon precursor again for a secondary polymerization to obtain SiO 2 layer-coated polymer-SiO 2 Composite spheres; S2. Heat-treat the SiO 2 layer-coated polymer-SiO 2 Composite spheres to obtain SiO 2 layer-coated carbon-SiO 2 Composite spheres; S3. Remove the SiO 2 in the layer-coated carbon-SiO 2 Composite spheres, and the dispersible mesoporous carbon spheres are obtained. 2

[0006] Preferably, the silicon precursor includes at least one of silicon acetate, ethyl trimethylsilylacetate, tetraethyl orthosilicate, tetrapropoxysilane, tetrakis(trimethylsilyl)silane, tris(trimethylsilyl)silane, tetrakis(dimethylsilyloxy)silane, and tetrabutoxysilane.

[0007] Preferably, the hydroxy-containing aromatic compound includes at least one of phenol, resorcinol, aminophenol, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 3,7-dihydroxy-2-naphthoic acid; The aldehyde compound includes aliphatic C1 to C12 aliphatic aldehydes or compounds that can be decomposed into formaldehyde.

[0008] Preferably, the base includes at least one of ammonia water, potassium hydroxide, sodium hydroxide, and triethylamine; The solvent includes at least one of water, methanol, ethanol, acetone, isopropanol, and tetrahydrofuran.

[0009] Preferably, in step S1, the molar ratio of the silicon precursor, the hydroxy-containing aromatic compound, the aldehyde compound, and the base during the first polymerization is 1-5:1:2-10:2-15, and the ratio of the silicon precursor used in the first polymerization to the silicon precursor used in the second polymerization is 1-5:1.

[0010] Preferably, in step S1, the reaction temperatures of the first polymerization and the second polymerization are the same, being 20-150 °C, the reaction time of the first polymerization is 12-36 h, and the reaction time of the second polymerization is 4-24 h.

[0011] Preferably, in step S2, the heat treatment temperature is 300-1200 °C, the time is 1-10 h, and the heat treatment atmosphere includes at least one of Ar, N 2 , He and H 2 in a mixed gas with an inert atmosphere.

[0012] Preferably, in step S3, the carbon-SiO 2 coated with SiO 2 composite spheres are immersed in an etching solution and left standing to remove SiO 2 , and the etching solution is an alkali solution or a hydrofluoric acid solution with a concentration of 0.5-8 mol L -1 , the alkali includes at least one of ammonia water, potassium hydroxide, sodium hydroxide, and triethylamine, the standing temperature is 40-90 °C, and the standing time is 2-48 h.

[0013] In a second aspect, the present invention provides a dispersible mesoporous carbon sphere obtained by the preparation method as described in the first aspect.

[0014] Preferably, the dispersible mesoporous carbon sphere has an open mesoporous structure, the pore diameter is 5-50 nm, the pore volume is 0.5-3 cm 3 g -1 , the specific surface area of the dispersible mesoporous carbon sphere is 300-1500 m 2 g -1 , and the diameter is 50-800 nm.

[0015] The beneficial effects achieved by one or more of the above technical solutions of the present invention are as follows: The dispersible mesoporous carbon sphere of the present invention has an open mesoporous structure, with a size in the range of 5-800 nm, has good dispersibility in a specific solvent, and has high stability, and has broad application prospects in the fields of catalysis, energy, biomedicine, etc.

[0016] The present invention obtains a dispersible mesoporous carbon sphere with high dispersibility and high stability through three steps of low-temperature polymerization, heat treatment, and desilication. The preparation method has the advantages of simple preparation process, low cost, and easy scale-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 It is the Zeta potential diagram of the dispersible mesoporous carbon spheres in water in Example 1 of the present invention; Figure 2 It is the size distribution diagram of the dispersible mesoporous carbon spheres in water in Example 1 of the present invention; Figure 3 It is the nitrogen physical adsorption diagram of the dispersible mesoporous carbon spheres in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] As described in the background art, there are problems such as a long process route, cumbersome operation, and high cost in the synthesis process of existing mesoporous carbon spheres.

[0020] The present invention provides a high-quality mesoporous carbon sphere and a preparation method thereof. During the low-temperature polymerization process, a SiO 2 layer-coated polymer-SiO 2 composite sphere is synthesized through a one-pot two-step silicon addition process, and SiO 2 simultaneously realizes the dual functions of pore formation and spatial separation. During the heat treatment process, the SiO 2 layer can prevent the cross-linking and agglomeration of the mesoporous carbon spheres; the size of the high-quality mesoporous carbon spheres is in the range of 5-800 nm and has good dispersibility in a specific solvent. When necessary, a surfactant can be added or the carbon spheres can be surface-modified to improve their dispersibility in the solvent.

[0021] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will specifically describe the technical solution of the present invention in detail with reference to specific examples and comparative examples.

[0022] Example 1 5 mL of tetrapropyl orthosilicate, 0.6 g of resorcinol, 0.8 mL of formaldehyde, and 2.0 mL of ammonia water were dissolved in 80 mL of ethanol-water to form a homogeneous solution, and stirred at 40 o °C for 24 hours. Then 2 mL of tetraethyl orthosilicate was added and stirring was continued for 12 h. After the reaction ended, centrifugation, washing, and drying were carried out, and carbonization was carried out at 600 o °C for 4 h under an argon atmosphere. The obtained product was added to 20 mL of 2 mol L -1 NaOH solution, and left standing at 70 o °C for 24 hours, washed, and dried to obtain dispersible mesoporous carbon spheres. The Zeta potential of the dispersible mesoporous carbon spheres in water is as shown in Figure 1As shown, the Zeta potential is about -30 mV, indicating that the dispersible mesoporous carbon spheres can be stably dispersed in water and are not easily agglomerated. As Figure 2 shown, the particle size of the dispersible mesoporous carbon spheres is mainly distributed at 200 nm. As Figure 3 shown, according to the nitrogen adsorption results, the specific surface area of the dispersible mesoporous carbon spheres is calculated to be 800 m 2 g -1 , the pore diameter is 18 nm, and the pore volume is 2.5 cm 3 g -1 .

[0023] Example 2 Dissolve 5 mL of tetrapropyl orthosilicate, 0.6 g of 3-aminophenol, 0.8 mL of formaldehyde, and 2.0 mL of ammonia water in 80 mL of water to form a homogeneous solution, and stir at 20 o °C for 24 hours. Add 2 mL of tetraethyl orthosilicate and continue stirring for 12 h. After the reaction is completed, centrifuge, wash, and dry. Carbonize at 600 o °C for 4 h in an argon atmosphere. Add the obtained product to 20 mL of 2 mol L -1 NaOH solution, and let it stand at 70 o °C for 24 hours. Wash and dry to obtain dispersible mesoporous carbon spheres with a diameter of 400 nm.

[0024] Example 3 Dissolve 5 mL of tetraethyl orthosilicate, 0.6 g of resorcinol, 0.8 mL of formaldehyde, and 4.0 mL of ammonia water in 80 mL of water to form a homogeneous solution, and stir at 20 o °C for 24 hours. Add 2 mL of tetrapropyl orthosilicate and continue stirring for 12 h. After the reaction is completed, centrifuge, wash, and dry. Carbonize at 600 o °C for 4 h in an argon atmosphere. Add the obtained product to 20 mL of 2 mol L -1 NaOH solution, and let it stand at 70 o °C for 24 hours. Wash and dry to obtain dispersible hollow mesoporous carbon spheres with a diameter of 600 nm.

[0025] Example 4 Dissolve 5 mL of tetrapropyl orthosilicate, 0.6 g of resorcinol, 0.8 mL of formaldehyde, and 2.0 mL of ammonia water in 80 mL of ethanol-water to form a homogeneous solution, and stir at 150 o °C for 24 hours. Add 2 mL of tetraethyl orthosilicate and continue stirring for 12 h. After the reaction is completed, centrifuge, wash, and dry. Carbonize at 900 o °C for 3 h in an argon atmosphere. Add the obtained product to 20 mL of 2 mol L -1 NaOH solution, and let it stand at 40o Let it stand for 48 hours, wash, and dry to obtain dispersible mesoporous carbon spheres.

[0026] Example 5 Dissolve 5 mL of tetrapropyl orthosilicate, 0.6 g of resorcinol, 0.8 mL of formaldehyde, and 2.0 mL of ammonia water in 80 mL of ethanol-water to form a homogeneous solution, and stir at 20 o °C for 24 hours. Add 2 mL of tetraethyl orthosilicate and continue stirring for 12 h. After the reaction is completed, centrifuge, wash, and dry. Carbonize at 300 o °C for 5 h. Add the obtained product to 20 mL of 2 mol / L -1 NaOH solution, let it stand at 90 o °C for 2 hours, wash, and dry to obtain dispersible mesoporous carbon spheres.

[0027] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of dispersible mesoporous carbon spheres, characterized in that, it comprises the following steps: S1. Mix a silicon precursor, a hydroxyl-containing aromatic compound, an aldehyde compound, a base, and a solvent, perform a primary polymerization, and then add the silicon precursor again after the reaction for a secondary polymerization to obtain a polymer-SiO 2 coated layer-SiO 2 composite sphere; S2. Coating the polymer-SiO 2 composite spheres with SiO 2 and subjecting the coated spheres to heat treatment to obtain SiO 2 coated carbon-SiO 2 composite spheres; S3. Remove SiO 2 layer-coated carbon-SiO 2 in the composite spheres of SiO 2 , thus obtaining dispersible mesoporous carbon spheres.

2. The preparation method according to claim 1, characterized in that, the silicon precursor includes at least one of silicon acetate, ethyl trimethylsilylacetate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrakis(trimethylsilyl)silane, tris(trimethylsilyl)silane, tetrakis(dimethylsilyloxy)silane, and tetrabutyl orthosilicate.

3. The preparation method according to claim 1, characterized in that, the hydroxy-containing aromatic compound includes at least one of phenol, resorcinol, aminophenol, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 3,7-dihydroxy-2-naphthoic acid; the aldehyde compound includes aliphatic C1 to C12 aliphatic aldehydes or compounds that can decompose into formaldehyde.

4. The preparation method according to claim 1, characterized in that, the base includes at least one of ammonia water, potassium hydroxide, sodium hydroxide, and triethylamine; the solvent includes at least one of water, methanol, ethanol, acetone, isopropanol, and tetrahydrofuran.

5. The preparation method according to claim 1, characterized in that, in step S1, the molar ratio of the silicon precursor, the hydroxy-containing aromatic compound, the aldehyde compound, and the base during the first polymerization is 1-5:1:2-10:2-15, and the ratio of the silicon precursor used in the first polymerization to the silicon precursor used in the second polymerization is 1-5:

1.

6. The preparation method according to claim 1, characterized in that, in step S1, the reaction temperatures of the first polymerization and the second polymerization are the same, being 20-150 °C, the reaction time of the first polymerization is 12-36 h, and the reaction time of the second polymerization is 4-24 h.

7. The preparation method according to claim 1, characterized in that, In step S2, the heat treatment temperature is 300 - 1200 °C, the time is 1 - 10 h, and the heat treatment atmosphere includes at least one of Ar, N 2 , He, and H 2 and a mixed gas with an inert atmosphere.

8. The preparation method according to claim 1, characterized in that, In step S3, the carbon-SiO 2 coated with SiO 2 composite spheres are immersed in the etching solution and left standing to remove SiO 2 , the etching solution is an alkali solution or a hydrofluoric acid solution with a concentration of 0.5-8 mol L -1 , the alkali includes at least one of ammonia water, potassium hydroxide, sodium hydroxide and triethylamine, the standing temperature is 40-90 °C, and the standing time is 2-48 h.

9. A dispersible mesoporous carbon sphere, characterized in that, it is obtained by the preparation method according to any one of claims 1-8.

10. The dispersible mesoporous carbon sphere according to claim 9, characterized in that, The dispersible mesoporous carbon spheres have an open mesoporous structure with a pore diameter of 5 - 50 nm and a pore volume of 0.5 - 3 cm 3 g -1 , and the specific surface area of the dispersible mesoporous carbon spheres is 300 - 1500 m 2 g -1 , with a diameter of 50 - 800 nm.

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