Preparation method of mesoporous silica

Abstract

The invention relates to a mesoporous silica preparation method, which comprises: S1, reaction liquid preparation: dissolving a surfactant in water, respectively adding n-hexane, a silane coupling agent having double bonds and a photoinitiator, and uniformly stirring to obtain a mixed liquid; s2, photo-initiation reaction: carrying out high-pressure mercury lamp illumination reflux reaction on the mixed solution obtained in the step S1 at a certain temperature to obtain a polymer; s3, silicon source hydrolysis reaction; s4, drying and washing; and S5, calcining to obtain the calcined mesoporous silica. According to the invention, a reactive surfactant and a silane coupling agent with double bonds are subjected to graft polymerization to obtain a silane compound with surface activity. The obtained silane compound with surface activity can be used as a pore-forming agent in the subsequent calcining process, and meanwhile, the agglomeration problem of particles can be effectively controlled, so that the particle size of the calcined mesoporous silica is in a submicron scale range.

Description

Technical Field

[0001] The invention belongs to the technical field of porous material preparation, and in particular relates to a method for preparing mesoporous silica. Background Art

[0002] Mesoporous silica (pore size 2-50 nm) is widely used in separation and purification, adsorption, catalysis, sensing, drug loading, and sustained release due to its high specific surface area and appropriate pore size distribution. Currently, mesoporous silica is typically prepared using hydrothermal or sol-gel methods, using surfactants (such as CTAB) or block polymers (such as P123) as organic templates to construct the mesoporous structure.

[0003] In fact, in the preparation process of nanomaterials, in addition to the role of pore formation and surface modification, surfactants also play a key role in controlling particle size. The preparation of mesoporous silica with good monodispersity and small particle size can effectively improve its performance in practical applications and broaden its scope of application. For example, in the process of preparing silica-loaded quantum dots by the all-solid-state method, the sample needs to be treated at high temperature. This will cause serious agglomeration between nanoparticles, and the synthesized quantum dots coated with mesoporous silica have a particle size of mostly micrometers. For example, our company's first application for a Chinese patent with publication number CN118978913A discloses a full-solid-state post-processing technology for perovskite quantum dots and its application. In its comparative example 1, it is clearly stated that after high-temperature calcination, the perovskite luminescent body obtained is subjected to particle size analysis using a Bettersize2600 laser particle size analyzer. The results show that the D50 of the quantum dot luminescent body is 4.665μm and the D97 is 75.67μm. This makes it difficult to obtain submicron-scale samples, severely limiting the use of high-precision preparation processes such as inkjet printing, and therefore needs to be improved. Summary of the Invention

[0004] This invention proposes a method for preparing mesoporous silica. This method graft-polymerizes a reactive surfactant with a silane coupling agent containing double bonds to produce a surface-active silane compound. This silane compound is then used to stabilize the interface of an oil-in-water emulsion, resulting in highly monodisperse mesoporous silica. The resulting surface-active silane compound acts as a pore-forming agent during the subsequent calcination process, effectively controlling particle agglomeration and ensuring that the mesoporous silica particle size after calcination is in the submicron range.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing mesoporous silica comprises the following steps:

[0007] S1. Preparation of reaction solution: dissolve the surfactant in water, then add n-hexane, a silane coupling agent with a double bond, and a photoinitiator, respectively, and stir to obtain a mixed solution;

[0008] S2, photoinitiated reaction: the mixed solution obtained in step S1 is subjected to a high-pressure mercury lamp irradiation reflux reaction at a certain temperature to obtain a polymer;

[0009] S3, silicon source hydrolysis reaction: adding alkaline aqueous solution and ethyl orthosilicate to the polymer after the reaction in step S2, and condensing and refluxing at a certain temperature to obtain a mixture;

[0010] S4, drying and washing: drying the mixture after the reaction in step S3, grinding it into powder, repeatedly washing it with water, extracting it with an organic solvent under reflux, and finally drying it to obtain the mesoporous silica before calcination;

[0011] S5, calcination: placing the pre-calcined mesoporous silica obtained in step S4 in a furnace, calcining it at a certain temperature and heating rate to remove the organic template, thereby obtaining calcined mesoporous silica.

[0012] Furthermore, in step S1, the surfactant is DNS-86 (1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate);

[0013] The silane coupling agent with double bonds is KH-570;

[0014] The photoinitiator is hydroxycyclohexane phenone.

[0015] Furthermore, in step S2, the temperature is 60-75° C., and the illumination reflux reaction time is 2-4 hours.

[0016] Furthermore, in step S3, the alkaline aqueous solution is aqueous ammonia, the condensation reflux reaction temperature is 65-75° C., and the reaction time is 1-3 hours.

[0017] Furthermore, in step S4, the drying temperature is 85-95° C., the organic solvent is anhydrous ethanol, the reflux extraction temperature is 85-95° C., and the time is 8-12 hours.

[0018] Furthermore, in step S5, the calcination temperature is 500-600° C., the heating rate is 8-12° C. / min, and the calcination time is 5-7 h.

[0019] Furthermore, before calcination, the average particle size of the mesoporous silica is controllable in the range of 40-100 nm, and the specific surface area is 180-280 m 2 / g range is adjustable;

[0020] After calcination, the average particle size of the mesoporous silica is 500-900 nm, and the specific surface area is 300-350 m 2 / g.

[0021] Furthermore, the pore size of the mesoporous silica after calcination is smaller than the pore size of the mesoporous silica before calcination.

[0022] Furthermore, the calcination step in step S5 can be compatible with the high-temperature sintering synthesis process of perovskite quantum dots, thereby combining the demolding process of mesoporous silica and the process of melting and filling mesoporous silica with perovskite precursor into one to synthesize perovskite quantum dots loaded with mesoporous silica.

[0023] Furthermore, the mesoporous silica prepared by the method can be used as an adsorption, loading and coating material;

[0024] The objects of adsorption, loading and coating include at least quantum dot materials.

[0025] Beneficial effects of the present invention: The present invention relates to a method for preparing mesoporous silica. The method uses reactive surfactants and silane coupling agents with double bonds as raw materials, water as the external phase, and n-hexane as the internal phase to form an oil-in-water emulsion, and initiates polymerization by ultraviolet light to form a stable shell at the interface of the oil-water emulsion. Then, by adding ethyl orthosilicate as a silicon source and hydrolyzing it under the action of ammonia water, silica with good monodispersity is obtained. Before calcination, the average particle size of the mesoporous silica can be controlled in the range of 40 to 100 nm, and the specific surface area is 180-280 m 2 The pore size is adjustable in the range of 1000 nm / g, and the pore size is about 9 nm. After calcination to remove the organic template, the mesoporous silica particles can be kept at the submicron scale, with a typical particle size of 500-900 nm and a specific surface area of 300-350 m 2 / g, with a pore size of approximately 7nm. The mesoporous silica obtained by this method has small particle size and good monodispersity, and can be used as an adsorption, loading and coating material, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The polymerization reaction equation of the DNS-86 of the present invention and the silane coupling agent having a double bond under the action of a photoinitiator is (a:b=4-15);

[0027] Figure 2 TEM image of the mesoporous silica prepared in Example 1 of the present invention before calcination;

[0028] Figure 3 This is a TEM image of the mesoporous silica prepared in Example 1 of the present invention after calcination;

[0029] Figure 4This is a particle size distribution diagram of the mesoporous silica prepared in Example 1 of the present invention before calcination;

[0030] Figure 5 This is a particle size distribution diagram of the mesoporous silica prepared in Example 1 of the present invention after calcination;

[0031] Figure 6 The adsorption-desorption curve and pore distribution diagram of the mesoporous silica prepared in Example 1 of the present invention before calcination;

[0032] Figure 7 This is the adsorption-desorption curve and pore distribution diagram of the mesoporous silica prepared in Example 1 of the present invention after calcination. DETAILED DESCRIPTION

[0033] To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] A method for preparing mesoporous silica comprises the following steps:

[0035] A certain amount of DNS-86 (1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate) was dissolved in a certain amount of distilled water, and a certain amount of n-hexane, KH-570 (γ-methacryloxypropyltrimethoxysilane) and 0.27g of photoinitiator (hydroxycyclohexane phenone) were added under stirring, and the mixture was refluxed at 68℃ under high pressure mercury lamp for 3h ( Figure 1 ). After the reaction is completed, a certain amount of ammonia water and ethyl orthosilicate are added, and the reaction is condensed and refluxed at 70°C for 2 hours. After the reaction is completed, it is placed in a 90°C oven for drying, and the dried solid is ground into powder with an agate mortar. After the obtained powder is repeatedly washed with distilled water, it is wrapped with filter paper and placed in a Soxhlet extractor. 300 mL of anhydrous ethanol is measured, refluxed at 90°C for 10 hours, and then placed in a 90°C forced drying oven for drying. The mesoporous silica before calcination is obtained. After drying is completed, it is placed in a pit furnace, set to 550°C, and the temperature is programmed to rise by 10°C / min. It is calcined at this temperature for 6 hours. Finally, the organic template is removed to obtain the calcined mesoporous silica.

[0036] The addition amount of each material component of Example 1 to Example 14 and the average particle size and polydispersity index (PDI) of the obtained product (mesoporous silica before calcination) are shown in Table 1:

[0037] Table 1

[0038]

[0039]

[0040] The present invention uses a reactive surfactant (DNS-86) and a silane coupling agent with double bonds as raw materials, water as the external phase and n-hexane as the internal phase to form an oil-in-water emulsion. Ultraviolet light is used to initiate polymerization to form a stable shell at the oil-water emulsion interface. Then, by adding ethyl orthosilicate as a silicon source and hydrolyzing it under the action of ammonia water, a well-dispersed silica is obtained. Before calcination, the average particle size of the mesoporous silica can be controlled in the range of 40 to 100 nm, and the specific surface area is 180-280 m 2 The pore size is adjustable in the range of 1000 nm. After calcination to remove the organic template, the mesoporous silica particles can be kept at the submicron scale, with the main particle size distribution being 500-1000 nm. Figure 4-5 shown.

[0041] Application examples:

[0042] The present invention provides an application example method that combines the demoulding process of mesoporous silica and the process of melting and filling mesoporous silica with a perovskite precursor into one, comprising the following steps:

[0043] Step A1: preparing the pre-calcined mesoporous silica prepared in Example 1, and blending it with a perovskite precursor (a lead source, a cesium source mixture and / or lead-cesium halide) to obtain a mixed powder;

[0044] Step A2: Place the mixed powder of step A1 in a pit furnace, set the temperature program to 550°C and 10°C / min, calcine at this temperature for 6 hours, and naturally cool to room temperature; finally, while removing the organic template, the perovskite precursor is melted and filled into the pores of the mesoporous silica to obtain perovskite quantum dots supported by mesoporous silica, that is, the mesoporous silica adsorbs, loads and coats the perovskite quantum dots.

[0045] The preparation method for the above-mentioned application example can also be found in Chinese Patent Publication No. CN113501540A, which discloses a lead halide cesium perovskite quantum dot and its preparation method. This method employs a blend of an unde-templated molecular sieve (mesoporous silica) and a perovskite precursor, followed by high-temperature calcination to temperatures above 500°C. This combines the steps of removing the template from the unde-templated molecular sieve and melt-filling the perovskite precursor into the molecular sieve pores. These steps are completed within a single calcination process, eliminating the need for repeated temperature increases and decreases.

[0046] It should be noted that calcining molecular sieves at high temperatures can cause agglomeration of the molecular sieves, resulting in an increase in particle size. Although the above-mentioned prior art (CN113501540A) combines the demoulding of the molecular sieve with the synthesis process of quantum dots loaded in the molecular sieve pores, it effectively avoids the repeated heating and cooling operations of the molecular sieve to further control the particle size of the synthesized quantum dots. However, even with process optimization, the synthesized quantum dots are still micron-sized. Instead of the submicron-sized average particle size consistent with the present application.

[0047] The definition of submicron level in the present invention is based on the common understanding of those skilled in the art, that is, the particle size range is between 0.1 μm (100 nm) and 1 μm (1000 nm).

[0048] Comparative Example 1:

[0049] The difference from Example 1 is that DNS-86 (1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate) is replaced by CTAB.

[0050] Conclusion: After calcination, the average particle size of mesoporous silica is greater than 1.5 μm.

[0051] Comparative Examples 2-5:

[0052] The difference from Example 1 is that the silane coupling agent KH-570 is replaced by KH-520, KH-530, KH-540, and KH-550 respectively.

[0053] Conclusion: Because KH-520, KH-530, KH-540, and KH-550 lack carbon-carbon double bonds in their structures, they cannot react and polymerize with DNS-86 (1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate), resulting in the same technical effects as those of the present invention. After calcination, the average particle size of the mesoporous silica is greater than 1.5 μm.

[0054] In summary: Figure 2-7 As shown in FIG. 1 , the average particle size of the mesoporous silica sample of the present invention before calcination is 49 nm, and the average particle size after calcination is 700 nm. The specific surface area before calcination is 212 m 2 / g, pore size 9nm; specific surface area after calcination 325m 2 / g, pore size 7nm.

[0055] In the calcination step S5 of the present invention, the organic template removed is a polymer formed by the surfactant (DNS-86) and the silane coupling agent (KH-570) having a double bond under the conditions of photoinitiation reaction, see Figure 1The reaction equation is shown. The synthesized surface-active silane compound plays a key role in the subsequent regulation of mesoporous silica particle size:

[0056] The present invention graft-polymerizes a reactive surfactant with a silane coupling agent containing double bonds to produce a surface-active silane compound. This silane compound is then used to stabilize the interface of an oil-in-water emulsion, resulting in mesoporous silica with good monodispersity. The resulting surface-active silane compound acts as a pore-forming agent during the subsequent calcination process, effectively controlling particle agglomeration and ensuring that the mesoporous silica particle size after calcination is in the submicron range.

[0057] While the present invention is described through the above-described embodiments to illustrate the detailed preparation methods of the present invention, the present invention is not limited to the above-described detailed preparation methods. This does not necessarily mean that the present invention must rely on the above-described products and detailed preparation methods in order to be implemented. Those skilled in the art will appreciate that any improvements to the present invention, or any combination or equivalent substitution of raw materials in the products of the present invention, fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing mesoporous silica, characterized in that: The steps include: S1. Preparation of reaction solution: dissolve the surfactant in water, then add n-hexane, a silane coupling agent with a double bond, and a photoinitiator, respectively, and stir to obtain a mixed solution; S2, photoinitiated reaction: the mixed solution obtained in step S1 is subjected to a high-pressure mercury lamp irradiation reflux reaction at a certain temperature to obtain a polymer; S3, silicon source hydrolysis reaction: adding alkaline aqueous solution and ethyl orthosilicate to the polymer after the reaction in step S2, and condensing and refluxing at a certain temperature to obtain a mixture; S4, drying and washing: drying the mixture after the reaction in step S3, grinding it into powder, repeatedly washing it with water, extracting it with an organic solvent under reflux, and finally drying it to obtain the mesoporous silica before calcination; S5, calcination: placing the pre-calcined mesoporous silica obtained in step S4 in a furnace, calcining it at a certain temperature and heating rate to remove the organic template, thereby obtaining calcined mesoporous silica.

2. The method for preparing mesoporous silica according to claim 1, wherein: In the step S1, the surfactant is DNS-86 (1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate); The silane coupling agent with double bonds is KH-570; The photoinitiator is hydroxycyclohexane phenone.

3. The method for preparing mesoporous silica according to claim 1, wherein: In step S2, the temperature is 60-75° C., and the illumination reflux reaction time is 2-4 hours.

4. The method for preparing mesoporous silica according to claim 1, wherein: In step S3, the alkaline aqueous solution is aqueous ammonia, the condensation reflux reaction temperature is 65-75° C., and the reaction time is 1-3 hours.

5. The method for preparing mesoporous silica according to claim 1, wherein: In step S4, the drying temperature is 85-95° C., the organic solvent is anhydrous ethanol, the reflux extraction temperature is 85-95° C., and the time is 8-12 hours.

6. The method for preparing mesoporous silica according to claim 1, wherein: In step S5, the calcination temperature is 500-600° C., the heating rate is 8-12° C. / min, and the calcination time is 5-7 h.

7. The method for preparing mesoporous silica according to claim 1, wherein: Before calcination, the average particle size of the mesoporous silica is controllable in the range of 40-100 nm, and the specific surface area is 180-280 m 2 / g range is adjustable; After calcination, the average particle size of the mesoporous silica is 500-900 nm, and the specific surface area is 300-350 m 2 / g.

8. The method for preparing mesoporous silica according to claim 7, wherein: The pore size of the mesoporous silica after calcination is smaller than the pore size of the mesoporous silica before calcination.

9. A method for preparing mesoporous silica according to any one of claims 1 to 8, characterized in that: The calcination step in step S5 is compatible with the high-temperature sintering synthesis process of perovskite quantum dots, thereby combining the demolding process of mesoporous silica and the process of melting and filling mesoporous silica with a perovskite precursor into one, so as to synthesize perovskite quantum dots supported by mesoporous silica.

10. A method for preparing mesoporous silica according to any one of claims 1 to 8, characterized in that: The mesoporous silica prepared by the method can be used as an adsorption, loading and coating material; The objects of adsorption, loading and coating include at least quantum dot materials.

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