A fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst and its preparation method

Abstract

This invention discloses a fluorine-regulated composite gas-phase photocatalytic material of titanium dioxide / metal-organic framework (MOF). Using titanium oxydifluoride as both the titanium and fluorine sources, fluorine is used to regulate the structure of the composite material during its synthesis, resulting in the in-situ generation of titanium dioxide within the pores of the MOF. This forms a composite gas-phase photocatalytic material with a high specific surface area and abundant pores, exhibiting a two-phase composite flower-like structure. The fluorine generated during the titanium dioxide production process regulates the structure of both the titanium dioxide and MOF, thereby enhancing the catalytic performance of the composite gas-phase photocatalytic material by providing it with a high specific surface area and abundant pores.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic material synthesis technology, specifically to a fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalytic material and its preparation method. Background Technology

[0002] Titanium dioxide is widely used in catalysis, especially photocatalysis, due to its advantages such as photocatalytic activity, high stability, biocompatibility, and low cost. It is one of the most widely used semiconductor materials. However, its application is limited by its narrow operating spectral band, limited number of redox active sites on the material surface, and unsatisfactory adsorption performance for gaseous reactants, particularly in gas-phase photocatalysis. To overcome these shortcomings, researchers at home and abroad have adopted a series of methods to obtain titanium-based photocatalytic materials with high specific surface areas in recent years, such as preparing small titanium dioxide nanoparticles, porous titanium dioxide materials, or titanium-based metal-organic frameworks (MOFs). However, these methods still cannot produce pure titanium dioxide materials with exceptionally high specific surface areas, and titanium-based MOFs also suffer from difficulties in synthesis, poor water stability, and unsatisfactory photocatalytic performance. MOFs, on the other hand, not only possess ultra-high specific surface areas but also strong gas adsorption properties and water stability. Preparing composite materials of these two materials holds promise for improving the gas-phase catalytic ability of titanium dioxide. Existing technologies include using fluorine to modulate titanium dioxide, enhancing the photocatalytic activity of TiO2 through the synergistic effect of surface fluorination, as surface fluorination increases the number of active free species in solution, thereby increasing the photocatalytic activity of TiO2. Existing technologies also involve finely controlling the structure of MOFs using fluorine. However, these methods all involve post-structure formation, making it impossible to control the structure during the manufacturing process. This would affect the effectiveness of fluorine control and result in complex and uncontrollable processes.

[0003] Therefore, a method is needed to control fluorine levels during the formation of composite structures, so as to achieve precise control and process control, while maximizing the performance of composite materials. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a fluorine-regulated composite gas-phase photocatalytic material of titanium dioxide / metal-organic framework and its preparation method. The fluorine generated during the titanium dioxide production process regulates the structure of titanium dioxide and MOF, so that the composite gas-phase photocatalytic material has a high specific surface area and abundant pore structure, thereby improving the catalytic performance of the composite gas-phase photocatalytic material.

[0005] The present invention relates to a fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalytic material, which uses titanium oxydifluoride as the titanium source and fluorine source. In the structural synthesis of the composite material, fluorine is used to regulate the process, and titanium dioxide is generated in situ in the pores of the metal-organic framework material to form a composite gas-phase photocatalytic material with high specific area and abundant pores. The composite gas-phase photocatalytic material has a two-phase composite flower-like structure.

[0006] Furthermore, the raw materials for the combined gas-phase photocatalytic material include titanium difluorooxygenate, cadmium nitrate nonahydrate, and terephthalic acid;

[0007] Furthermore, in molar ratio, titanium difluorooxy: cadmium nitrate nonahydrate: terephthalic acid = 1:8-12:12-18.

[0008] The preparation method of the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalytic material of the present invention includes the following steps:

[0009] A composite gas-phase photocatalytic material of titanium dioxide / metal-organic framework was synthesized via hydrothermal reaction using titanium dioxide as both titanium and fluorine source.

[0010] Furthermore, the following steps are included:

[0011] Titanium difluorooxygenate, cadmium nitrate nonahydrate and terephthalic acid were added to water and mixed evenly, and then subjected to hydrothermal reaction. The product of hydrothermal reaction was washed and vacuum dried to obtain composite gas phase photocatalytic material.

[0012] Furthermore, the hydrothermal reaction temperature is 200℃-240℃, and the hydrothermal reaction time is 8-72h;

[0013] Furthermore, the vacuum drying temperature is 120-160℃, and the drying time is 6-24h;

[0014] Furthermore, the sample was washed 3-5 times with a mixture of DMF and ethanol, with a mass ratio of DMF to ethanol of 1:1.

[0015] Furthermore, the titanium difluoride is prepared by the following method:

[0016] Titanium source was added to a mixed solution of hydrofluoric acid and acetic acid and stirred evenly before undergoing a hydrothermal reaction. The resulting product was centrifuged, washed, and dried to obtain titanium difluoride. The hydrothermal reaction temperature was 160-200℃ and the reaction time was 12-24h. The drying temperature was 40-70℃ and the drying time was 6-24h.

[0017] Furthermore, the titanium source is tetrabutyl titanate or isopropyl titanate; the molar ratio is hydrofluoric acid: acetic acid: titanium source = 1:2-4:8-16.

[0018] The beneficial effects of this invention are as follows: The fluorine-regulated composite gas-phase photocatalytic material of titanium dioxide / metal-organic framework (MOF) and its preparation method disclosed herein use titanium difluoride (TIF) as both the titanium and fluorine sources. TIF generates titanium dioxide and fluoride ions in water. The fluoride ions slowly and orderly enter the pores of the MOF structure, leaving titanium dioxide structures in situ. This allows for fluorine-controlled material regulation during the formation of the titanium dioxide and MOF structure, resulting in a structure with the highest specific surface area and abundant pores, reaching over 2000 m² / g. Furthermore, the reaction rate of TIF in water is favorable for nucleation and does not easily clog the pores of the MOF structure, thus better achieving the composite of titanium dioxide and the MOF structure. In contrast, other fluoride-containing titanium sources, if hydrolyzed too quickly, will immediately nucleate, and the nuclei will be large, clogging the pores of the MOF structure and hindering the composite of titanium dioxide and the MOF structure. Therefore, the hydrolysis rate of the titanium and fluorine sources in water, and whether this rate is controllable, directly determines the specific surface area. The present invention constructs a metal-organic framework material shell on the surface of titanium dioxide, utilizing the high specific surface area and strong gas adsorption performance of MOF materials. The preparation method is simple and reproducible, and the prepared composite catalyst has excellent gas-phase catalytic performance and can be reused. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0020] Figure 1 Optical photographs of Examples 1-3 and Comparative Examples 1-2 of fluorine-modulated titanium dioxide / metal-organic framework composite gas-phase photocatalysts;

[0021] Figure 2 High-resolution SEM image of Example 3 of a fluorine-modulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst;

[0022] Figure 3 The images show the XRD patterns of Examples 1-3, Comparative Examples 1-2, and commercial anatase phase titanium dioxide of fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalysts.

[0023] Figure 4 (a) is the nitrogen adsorption-desorption curve of Examples 1-3 and Comparative Examples 1-2 of the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst.

[0024] Figure 4 (b) is a pore size distribution diagram of Examples 1-3 and Comparative Examples 1-2 of the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst material;

[0025] Figure 5Table 1 shows the specific surface area test results of Examples 1-3, Comparative Examples 1-2, and commercial anatase titanium dioxide composite gas-phase photocatalysts with fluorine-regulated titanium dioxide / metal-organic framework materials. Detailed Implementation

[0026] Example 1

[0027] Preparation of titanium difluoride

[0028] 0.1 mol tetrabutyl titanate was added to a mixed solution of 0.25 mol hydrofluoric acid and 1 mol acetic acid, and stirred at a constant speed for 20 min to prepare a reaction solution. The reaction solution was transferred to a hydrothermal reactor, and the reactor was placed in a forced-air drying oven and hydrothermally reacted at 180°C for 15 h. After cooling to room temperature, the product was washed several times with anhydrous ethanol by centrifugation and dried in a forced-air drying oven at 80°C for 4 h to obtain titanium difluoride.

[0029] Preparation of Fluorine-Regulated Titanium Dioxide / Metal-Organic Framework Composite Gas-Phase Photocatalyst: Weigh 0.35 mmol of titanium difluoride oxyfluoride prepared in step one, 3 mmol of cadmium nitrate nonahydrate, and 4.6 mmol of terephthalic acid, add them to 15 mL of water, mix well to obtain a reaction solution, transfer the above reaction solution to a hydrothermal reactor, place the hydrothermal reactor and the reactor in a forced-air drying oven, and hydrothermally react at 220 °C for 8 h; after cooling to room temperature, centrifuge to obtain the product, wash three times with a mixture of 30 mL of LDM and ethanol (1:1), and dry in a vacuum drying oven at 150 °C for 6 h to obtain the titanium dioxide / metal-organic framework composite gas-phase photocatalyst.

[0030] Example 2

[0031] Preparation of titanium difluoride

[0032] 0.1 mol of isopropyl titanate was added to a mixed solution of 0.3 mol hydrofluoric acid and 1.2 mol acetic acid, and stirred at a constant speed for 30 min to prepare a reaction solution. The reaction solution was transferred to a hydrothermal reactor, and the reactor was placed in a forced-air drying oven and hydrothermally reacted at 180°C for 9 h. After cooling to room temperature, the product was washed several times with anhydrous ethanol by centrifugation and dried in a forced-air drying oven at 80°C for 6 h to obtain titanium difluoride.

[0033] Preparation of Fluorine-Regulated Titanium Dioxide / Metal-Organic Framework Composite Gas-Phase Photocatalyst: Weigh 1.5 mmol of titanium difluoride oxyfluoride prepared in step one, 3 mmol of cadmium nitrate nonahydrate, and 4.6 mmol of terephthalic acid, add them to 20 mL of water, mix well to obtain a reaction solution, transfer the above reaction solution to a hydrothermal reactor, place the hydrothermal reactor together in a forced-air drying oven, and hydrothermally react at 220 °C for 12 h; after cooling to room temperature, centrifuge to obtain the product, wash 3 times with a mixture of 30 mL of DMF and ethanol (1:1), and dry in a vacuum drying oven at 150 °C for 8 h to obtain the titanium dioxide / metal-organic framework composite gas-phase photocatalyst.

[0034] Example 3

[0035] Preparation of titanium difluoride

[0036] 0.1 mol of isopropyl titanate was added to a mixed solution of 0.3 mol hydrofluoric acid and 1.2 mol acetic acid, and stirred at a constant speed for 15 min to prepare a reaction solution. The reaction solution was transferred to a hydrothermal reactor, and the reactor was placed in a forced-air drying oven and hydrothermally reacted at 180°C for 12 h. After cooling to room temperature, the product was washed several times by centrifugation with anhydrous ethanol and dried in a forced-air drying oven at 60°C for 6 h to obtain titanium difluoride.

[0037] Preparation of Fluorine-Regulated Titanium Dioxide / Metal-Organic Framework Composite Gas-Phase Photocatalyst: Weigh 3 mmol of titanium difluoride oxyfluoride prepared in step one, 3 mmol of cadmium nitrate nonahydrate, and 4.6 mmol of terephthalic acid, add them to 20 mL of water, mix well to obtain a reaction solution, transfer the above reaction solution to a hydrothermal reactor, place the hydrothermal reactor and the reactor in a forced-air drying oven, and hydrothermally react at 230 °C for 24 h; after cooling to room temperature, centrifuge to obtain the product, wash three times with a mixture of 30 mL of LDM and ethanol (1:1), and dry in a vacuum drying oven at 150 °C for 8 h to obtain the titanium dioxide / metal-organic framework composite gas-phase photocatalyst.

[0038] Comparative Example 1

[0039] Preparation of titanium difluoride

[0040] 0.1 mol tetrabutyl titanate was added to a mixed solution of 0.25 mol hydrofluoric acid and 1 mol acetic acid, and stirred at a constant speed for 20 min to prepare a reaction solution. The reaction solution was transferred to a hydrothermal reactor, and the reactor was placed in a forced-air drying oven and hydrothermally reacted at 180°C for 15 h. After cooling to room temperature, the product was washed several times with anhydrous ethanol by centrifugation and dried in a forced-air drying oven at 80°C for 4 h to obtain titanium difluoride.

[0041] Comparative Example 2

[0042] Preparation of metal-organic framework material MIL-101-Cr

[0043] Weigh 3 mmol of cadmium nitrate nonahydrate and 4.6 mmol of terephthalic acid and add them to 15 mL of water. Mix well to prepare a reaction solution. Transfer the reaction solution to a hydrothermal reactor and place the reactor in a forced-air drying oven. React hydrothermally at 220 °C for 8 h. After cooling to room temperature, centrifuge to obtain the product. Wash three times with a mixture of 30 mL of LDM and ethanol (1:1). Dry in a vacuum drying oven at 150 °C for 6 h to obtain the metal-organic framework material MIL-101-Cr.

[0044] Figure 1 Optical photographs of the titanium dioxide / metal-organic framework composite gas-phase photocatalysts prepared in Examples 1-3, the titanium difluoride prepared in Comparative Example 1, and the metal-organic frameworks prepared in Comparative Example 2. Figure 2 This is a SEM image of the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst prepared in Example 3. Figure 3 For XRD patterns, Figure 4 Table 1 shows the nitrogen adsorption curves and pore size distribution diagrams, and the specific surface area test results for Examples 1-3 and Comparative Examples 1-2.

[0045] from Figure 1 As can be seen, the titanium difluoride prepared in Comparative Example 1 is a white powder, the metal-organic framework material prepared in Comparative Example 2 is a blue powder sample, and the titanium dioxide / metal-organic framework composite gas-phase photocatalyst material prepared in Examples 1-3 is a yellow-green powder sample, and the yellow color gradually deepens with the increase of titanium source content during the synthesis process. Figure 2 The SEM image of the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst prepared in Example 3 shows that the sample has a two-phase composite flower-like structure with no obvious phase separation. Figure 3 The XRD patterns show that Comparative Example 1 has a typical titanium difluoride structure, Comparative Example 2 has a typical metal-organic framework material MIL-101-Cr, and Examples 1-3 are gas-phase photocatalytic materials composed of anatase phase titanium dioxide and metal-organic framework material (MIL-101-Cr). Furthermore, the relative content of titanium dioxide in the samples increases continuously with the increase of titanium source dosage during the synthesis process. Figure 4 Table 1 shows the nitrogen adsorption curves and pore size distribution diagrams, and the specific surface area test results for Examples 1-3 and Comparative Examples 1-2. The test results show that the specific surface area of ​​the prepared titanium difluoride in Comparative Example 1 is only 4 m². 2 / g, Comparative Example 2: Metal-Organic Framework Material MIL-101-Cr with a specific surface area as high as 2560m² 2 / g, the specific surface area of ​​the commercially available anatase titanium dioxide is only 27m². 2 / g, while the specific surface areas of the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalysts prepared in Examples 1-3 were as high as 2780, 2020, and 1940 m², respectively. 2 The specific surface area of ​​the fluorine-regulated titanium dioxide / metal-organic framework composite gas-phase photocatalyst prepared in Example 1 is nearly 100 times that of commercial titanium dioxide. Even with only a small amount of titanium dioxide incorporated, the specific surface area of ​​this composite material can be higher than that of the pure metal-organic framework material MIL-101-Cr. The specific surface area of ​​the composite material decreases with increasing relative titanium dioxide content. This high specific surface area makes the fluorine-regulated titanium dioxide / metal-organic framework composite material a very promising candidate for application in the field of catalysis, especially in gas-phase photocatalysis.

[0046] All the raw materials listed in this invention, as well as the upper and lower limits and ranges of the raw materials and the upper and lower limits and ranges of the process parameters (such as temperature, time, etc.), can realize this invention. Examples are not listed one by one here.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite gas-phase photocatalytic material of fluorine-regulated titanium dioxide / metal-organic framework, characterized in that: Using titanium difluoride as both the titanium and fluorine sources, fluorine is used to regulate the structural synthesis of composite materials, and titanium dioxide is generated in situ within the pores of the metal-organic framework material, forming a composite gas-phase photocatalytic material with high specific area and abundant pores. This composite gas-phase photocatalytic material has a two-phase composite flower-like structure. The raw materials for this composite gas-phase photocatalytic material include titanium difluoride, chromium nitrate nonahydrate, and terephthalic acid; the molar ratio is titanium difluoride:chromium nitrate nonahydrate:terephthalic acid = 1:8-12:12-18. The preparation of the composite gas-phase photocatalytic material includes the following steps: titanium difluoride, chromium nitrate nonahydrate, and terephthalic acid are added to water and mixed evenly, followed by a hydrothermal reaction. The product of the hydrothermal reaction is washed and vacuum dried to obtain the composite gas-phase photocatalytic material. The hydrothermal reaction temperature is 200℃-240℃, and the hydrothermal reaction time is 8-72 h.

2. The composite gas-phase photocatalytic material of fluorine-regulated titanium dioxide / metal-organic framework according to claim 1, characterized in that: The vacuum drying temperature is 120-160℃, and the drying time is 6-24h.

3. The composite gas-phase photocatalytic material of fluorine-regulated titanium dioxide / metal-organic framework according to claim 1, characterized in that: Wash 3-5 times with a mixture of DMF and ethanol, with a mass ratio of DMF to ethanol of 1:

1.

4. The composite gas-phase photocatalytic material of fluorine-regulated titanium dioxide / metal-organic framework according to claim 1, characterized in that: The titanium difluoride is prepared by the following method: a titanium source is added to a mixed solution of hydrofluoric acid and acetic acid and stirred evenly, followed by a hydrothermal reaction. The resulting product is centrifuged, washed, and dried to obtain titanium difluoride. The hydrothermal reaction temperature is 160-200℃, and the reaction time is 12-24h. The drying temperature is 40-70℃, and the drying time is 6-24h.

5. The composite gas-phase photocatalytic material of fluorine-regulated titanium dioxide / metal-organic framework according to claim 4, characterized in that: The titanium source is tetrabutyl titanate or isopropyl titanate; the molar ratio is hydrofluoric acid: acetic acid: titanium source = 1:2-4:8-16.

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