CN106238100B - Titanium dioxide nanoplate loads the preparation and application process of MIL-100 (Fe) composite photocatalyst material - Google Patents

Abstract

The invention discloses a method for preparing and applying a composite photocatalytic material loaded with titanium dioxide nanosheets MIL‑100 (Fe), which belongs to the field of titanium dioxide photocatalysis, and in particular relates to the field of titanium dioxide nanosheets loaded porous metal-organic framework (MOFs) composite materials. In the present invention, tetrabutyl titanate and hydrofluoric acid are stirred evenly at room temperature, put into a hydrothermal reaction kettle for reaction, and titanium dioxide nanosheets are obtained after separation, washing and drying; then titanium dioxide nanosheets are uniformly dispersed in three Ferric chloride anhydrous ethanol solution, magnetically stirred at room temperature for 15 minutes, after separation by suction filtration, the obtained product was dispersed in trimesic acid anhydrous ethanol solution, reacted in a water bath at 50-80°C for 20-50 minutes, and filtered by suction The product obtained after separation is repeated 2 to 50 times to obtain a composite photocatalytic material loaded with titanium dioxide nanosheets MIL‑100 (Fe); the catalyst prepared by this method is particularly suitable for catalytic degradation of high-concentration organic dyes (such as methylene blue ), reaching a high degradation rate.

Description

Preparation and application of MIL-100(Fe) composite photocatalytic materials supported by titanium dioxide nanosheets application method

technical field

The invention relates to the field of titanium dioxide photocatalysis, in particular to the field of titanium dioxide nanosheet-loaded porous metal-organic framework (MOFs) composite materials. The catalyst prepared by the method is particularly suitable for catalytically degrading high-concentration organic dyes (such as methylene blue) under visible light irradiation, and achieves a high degradation rate.

Background technique

At present, titanium dioxide photocatalyst has attracted extensive attention of researchers at home and abroad due to its advantages of stability, non-toxicity and low price, and has broad application prospects in wastewater treatment, air purification, antibacterial and deodorizing, self-cleaning and other fields. Anatase-phase single-crystal titanium dioxide nanosheets have a higher proportion of high-energy active surfaces (001), which can more effectively promote the catalytic reaction, and thus have received great attention. However, the small photoresponse range and the high recombination rate of photogenerated electrons and holes lead to low photon quantum efficiency and slow reaction rate, which limit the practical application of titanium dioxide.

Metal-organic frameworks (MOFs) are crystalline porous materials with periodic network structures formed by self-assembly of transition metal ions and organic ligands. During the charge transfer process from the ligand to the metal under light conditions, highly active electrons and holes will be generated to have catalytic activity. TiO2-loaded MOFs composite system material has high adsorption and special contact interface structure, so it can greatly accelerate the process of photocatalytic reaction.

There are generally two types of MOFs in titanium dioxide-MOFs materials (1) with Ti metal as the central atom; (2) with non-Ti metal as the central atom. When Ti metal is the central atom, the ligand is generally trimesic acid, terephthalic acid or terephthalic acid with amino groups. Ti precursors and organic ligands are added during the preparation process to simultaneously generate titanium dioxide and MOFs under hydrothermal conditions to form a composite photocatalytic material. When non-Ti metal is used as the central atom, titanium dioxide nanomaterials, metal salts of MOFs central metals and ligands are added to the reaction system at the same time, and finally a titanium dioxide-loaded MOFs composite photocatalytic material is obtained. The latter is difficult to prepare due to harsh reaction conditions, and there are few types of MOFs that can perform photocatalytic reactions, so there are few reports.

Wu et al. (Wu Ling, Huang Linjuan, Shen Lijuan, Qin Na, Xiong Jinhua, Fuzhou University) Ti-MOF (MIL-125(Ti)-NH ₂ ) was self-templated in a certain ratio of oxygen and nitrogen atmosphere (oxygen: nitrogen = 1 :5～1:10) to synthesize large specific surface area and N self-doped TiO ₂ polyhedra. Through this template method, the morphology of MOF is well copied, and the microporous structure greatly improves the specific surface area of TiO ₂ , the specific surface area reaches 262.3m ² /g, and the regulation of MOF ligands can TiO ₂ is doped with N, F, and S elements to improve the visible light photocatalytic performance of TiO ₂ . However, the MIL-125(Ti)-NH ₂ material obtained by this method needs to rely on the doping of non-metallic elements to achieve visible photocatalytic performance, and there is still a long way to go before it can be put into practical production and application.

Zheng et al. (Zheng Jing, Qi Pengyu, Li Chenqi, Hu Liping, Shi Lei, Zhang Min, Xu Jingli, Shanghai University of Engineering and Technology) dissolved TiO ₂ nanomaterials, soluble cobalt salts, and trimesic acid in deionized water and placed them in a closed reactor. Heat to 135-150°C and keep it for 20-28 hours; then lower the temperature to 118-122°C and keep it for 4.5-6 hours; then lower the temperature to 98-105°C and keep it for 4.5-6 hours, and finally let it cool down to room temperature naturally Stand still for 11-14 hours; take the precipitate and wash it thoroughly to obtain a TiO ₂ /Co-MOF composite material. The obtained material has good thermal stability and chemical stability, has strong adsorption to dyes, and can be used as an adsorbent. This method is cumbersome, energy-intensive, and does not demonstrate responsiveness to visible light.

The Fe-centered, trimesic acid-liganded MOF——MIL-100(Fe) has visible-light photocatalytic performance and good water and thermal stability. In the present invention, titanium dioxide nanosheets and MIL-100(Fe) are combined for the first time, and a high-efficiency visible light catalyst that loads MIL-100(Fe) on titanium dioxide nanosheets is prepared by using a layer-by-layer coating method.

Contents of the invention

The invention provides a method for preparing a titanium dioxide nanosheet loaded MIL-100 (Fe) composite material, which enables the titanium dioxide nanosheet catalyst loaded with the MIL-100 (Fe) to have excellent photocatalytic performance.

A kind of preparation method of titanium dioxide nano sheet loaded MIL-100 (Fe) composite material, comprises the following steps:

1) Stir tetrabutyl titanate and hydrofluoric acid evenly at room temperature, put them into a hydrothermal reaction kettle at 150-220° C. for 15-24 hours, and obtain titanium dioxide nanosheets after separation, washing and drying.

2) Uniformly disperse the titanium dioxide nanosheets in step 1) in ferric chloride absolute ethanol solution, stir magnetically at room temperature for 15 min, and disperse the obtained product in trimesic acid absolute ethanol solution after separation by suction filtration , react in a water bath at 50-80° C. for 20-50 minutes, and separate the product obtained by suction filtration, then repeat step 2) 2-50 times to obtain a composite photocatalytic material loaded with titanium dioxide nanosheets MIL-100 (Fe).

In step 1), preferably, the mass ratio of tetrabutyl titanate to hydrofluoric acid is 1:0.1-0.3:. It is beneficial to obtain titanium dioxide nanosheets with different sizes and better crystallinity, so that the finally prepared titanium dioxide nanosheets loaded MIL-100(Fe) composite material has better visible light photocatalytic performance. Further preferably, the mass ratio of tetrabutyl titanate to hydrofluoric acid is 1:0.2-0.25. It is beneficial to obtain titanium dioxide nanosheets with different sizes and better crystallinity, so that the finally prepared titanium dioxide nanosheets loaded MIL-100(Fe) composite material has better visible light photocatalytic performance.

Preferably, react in a high-temperature reactor at 150-220° C. for 15-24 hours, and react under the preferred conditions by hydrothermal synthesis method, which is beneficial to obtain titanium dioxide nanosheets with better crystallinity and relatively uniform morphology. Further preferably, reacting in a high-temperature reactor at 200-220° C. for 20-22 hours can obtain better crystallinity, which is beneficial to obtain titanium dioxide nanosheets with more uniform morphology.

As a preference, the water bath reaction temperature described in step 1) is 60-70°C, the time is 30-40min, and the product obtained after suction filtration and separation, repeats step 2) for 15-20 times

In step 2), as a preference, the mass ratio of titanium dioxide nanosheets, ferric chloride absolute ethanol solution, and trimesic acid absolute ethanol solution is 1:0.2～0.5:0.1～0.4, so that MIL-100 (Fe) can be loaded on TiO2 nanosheets, thus exhibiting good catalytic activity under visible light. Further preferably, the mass ratio of titanium dioxide nanosheets, ferric chloride absolute ethanol solution, and trimesic acid absolute ethanol solution is 1:0.30-0.35:0.25-0.30. It is beneficial to obtain a composite material with uniform loading of MIL-100(Fe), thereby showing better catalytic activity under visible light.

The titanium dioxide nanosheet loaded MIL-100 (Fe) composite photocatalyst prepared by the present invention is applied to the photocatalytic degradation experiment, and 20 mg titanium dioxide nanosheet loaded MIL-100 (Fe) composite material is added in the methylene blue aqueous solution whose concentration is 50 mg/L, and then Add 0.2ml H ₂ O ₂ , ultrasonically disperse evenly, and react in dark for 60 minutes. When the adsorption equilibrium is reached, place it under a 300w xenon mercury lamp with a wavelength greater than 420nm for photocatalytic degradation reaction. Visible light was used as the light source and methylene blue was used as the target degradation product for photocatalytic degradation treatment, and a good degradation effect was achieved.

Adopting the present invention to prepare the titanium dioxide nanosheet photocatalyst loaded with MIL-100 (Fe) has the following advantages: (1) has very high adsorptivity, utilizes the porosity of MIL-100 (Fe) to adsorb organic molecules, thereby Make the photocatalytic active surface of the catalyst fully contact with the degradation substrate to improve the photocatalytic efficiency; (2) improve the photon quantum efficiency, and the transfer of electrons between titanium dioxide and MIL-100(Fe) can be efficiently carried out to improve the electron-hole ratio. Separation efficiency, so as to speed up the catalytic reaction, can degrade high concentration of organic matter in a short time; (3) has a visible light photoresponse, MIL-100 (Fe) loading can promote the catalyst to absorb visible light, so that the material has visible light Catalytic activity; (4) The preparation method is simple; this preparation method can obtain titanium dioxide nanosheets with easy-to-control morphology through a simple hydrothermal reaction, and obtain a uniformly loaded composite material through a layer-by-layer coating method, and the preparation parameters are easy. control, good repeatability.

The catalyst carrier of the present invention is a titanium dioxide nano sheet prepared by a hydrothermal reaction method, the size of which is about 50-60 nm, and an anatase phase structure. The photocatalytic composite material loaded with MIL-100(Fe) was obtained under the conditions of ferric chloride as iron source and trimesic acid as ligand in water bath. The prepared MIL-100(Fe)-loaded titanium dioxide nanosheet photocatalyst was applied to the photocatalytic degradation experiment. Visible light was used as the light source and high concentration of methylene blue was used as the target degradation product for photocatalytic degradation treatment, and a good degradation effect was achieved.

Description of drawings

Fig. 1 is the transmission electron microscope figure (TEM) of the titania nanosheet that embodiment 1 prepares

Fig. 2 is the scanning electron micrograph (SEM) of the MIL-100 (Fe) loaded titania nanosheet prepared in embodiment 1

Fig. 3 is the transmission electron micrograph (TEM) of the MIL-100 (Fe) loaded titania nanosheet prepared in embodiment 1

Fig. 4 is the XRD figure of the MIL-100 (Fe) loaded titania nanosheet prepared in embodiment 1

Fig. 5 is the photocatalytic degradation curve of the MIL-100(Fe) loaded titanium dioxide nanosheets prepared in Example 1.

Detailed ways

Below in conjunction with example the method of the present invention is described further. These examples further describe and demonstrate embodiments within the scope of the present invention. The examples given are for the purpose of illustration only and do not constitute any limitation to the present invention, and various changes can be made thereto without departing from the spirit and scope of the present invention.

Example 1

(1) Add 5ml of hydrofluoric acid with a mass fraction of 40% to 25ml of tetrabutyl titanate, stir evenly at 25°C, put it into a 100ml autoclave, and react at 200°C for 20h. After the reaction is finished, it is washed to neutrality with deionized water and ethanol, and dried to obtain titanium dioxide nanosheet powder.

(2) Weigh 0.027g of ferric trichloride hexahydrate and dissolve it in 10m of ethanol, ultrasonically dissolve it fully, and then disperse 0.10g of prepared titanium dioxide nanosheets into the above solution, after ultrasonic dispersion is uniform, magnetic force at room temperature After stirring for 15 min, the titanium dioxide nanosheets with Fe ³⁺ adsorption were separated by suction filtration; 0.021 g of trimesic acid was dissolved in 10 m of ethanol, and ultrasonically dissolved to fully dissolve the Fe ³⁺ adsorbed titanium dioxide nanosheets. Trimellitic acid ethanol solution, dispersed evenly, placed in a 70°C water bath for 30min reaction, and then separated by suction to obtain a sample.

(3) Step (2) of Example 1 was repeated 20 times, that is, titanium dioxide nanosheets were coated with MIL-100(Fe) 20 times to obtain a composite photocatalytic material loaded with titanium dioxide nanosheets MIL-100(Fe).

The obtained product is analyzed by a transmission electron microscope (TEM) and shows that the titanium dioxide prepared by the method has a size of about 70-80 nm, a uniform thin sheet structure and a relatively smooth surface. After loading MIL-100(Fe), irregular MIL-100(Fe) crystals can be clearly seen on the surface of titanium dioxide in scanning electron microscope (SEM) and transmission electron microscope (TEM).

Weighed 20 mg of the above-prepared MIL-100(Fe)-loaded titanium dioxide nanosheet catalyst to carry out the experiment of catalytic degradation of high concentration methylene blue under visible light. The methylene blue concentration was 50 mg·L ^-1 , and the degradation rate of methylene blue was 99.0% after 80 min of visible light irradiation.

Example 2

The preparation method of the MIL-100 (Fe) loaded titanium dioxide nanosheet composite catalyst, the steps are the same as in Example 1, the difference is: the titanium dioxide nanosheets are coated with MIL-100 (Fe) 5 times

Weighed 20 mg of the above-prepared MIL-100(Fe)-loaded titanium dioxide nanosheet catalyst to carry out the experiment of catalytic degradation of high ^- concentration methylene blue under visible light.

Example 3

The preparation method of MIL-100 (Fe) loaded titanium dioxide nanosheet composite catalyst, the steps are the same as in Example 1, the difference is: titanium dioxide nanosheets are coated MIL-100 (Fe) 10 times

Weighed 20 mg of the above-prepared MIL-100(Fe)-loaded titanium dioxide nanosheet catalyst to carry out the experiment of catalytic degradation of high concentration methylene blue under visible light. The methylene blue concentration was 50 mg·L ^-1 , and the degradation rate of methylene blue was 84.2% after 80 min of visible light irradiation.

Example 4

The preparation method of MIL-100 (Fe) loaded titanium dioxide nanosheet composite catalyst, the steps are the same as in Example 1, the difference is: titanium dioxide nanosheets are coated MIL-100 (Fe) 25 times

Weighed 20 mg of the above-prepared MIL-100(Fe)-supported titanium dioxide nanosheet catalyst to carry out the experiment of catalytic degradation of high concentration methylene blue under visible light. The methylene blue concentration was 50 mg·L ^-1 , and the degradation rate of methylene blue was 76.5% after 80 min of visible light irradiation.

Claims (9)

1. A preparation method of titanium dioxide nanosheet loaded MIL‐100 (Fe) composite photocatalytic material, characterized in that it comprises the following steps: 1) Stir tetrabutyl titanate and hydrofluoric acid together at room temperature evenly, put them into a hydrothermal reaction kettle for reaction, and obtain titanium dioxide nanosheets after separation, washing and drying; 2) Uniformly disperse the titanium dioxide nanosheets in step 1) in ferric chloride absolute ethanol solution, stir magnetically at room temperature for 15 min, and disperse the obtained product in trimesic acid absolute ethanol solution after separation by suction filtration , reacted in a water bath at 50-80°C for 20-50 minutes, and separated the product obtained by suction filtration, and then repeated step 2) 2-50 times to obtain a composite photocatalytic material loaded with titanium dioxide nanosheets MIL‐100 (Fe); In step 1), the mass ratio of tetrabutyl titanate to hydrofluoric acid is 1:0.1-0.3; The mass ratio of titanium dioxide nanosheets, ferric chloride absolute ethanol solution and trimesic acid absolute ethanol solution in step 2) is 1:0.2-0.5:0.1-0.4. 2. the preparation method of titanium dioxide nanosheet load MIL-100 (Fe) composite photocatalytic material according to claim 1, is characterized in that, in step 1), the quality of described tetrabutyl titanate, hydrofluoric acid The ratio is 1:0.2～0.25. 3. The preparation method of titanium dioxide nanosheets loaded MIL-100 (Fe) composite photocatalytic material according to claim 1, characterized in that, in step 1), react in a hydrothermal reactor at 150-220°C for 15-24h . 4. The method for preparing the titanium dioxide nanosheet-loaded MIL-100 (Fe) composite photocatalytic material according to claim 3, characterized in that the reaction is carried out in a hydrothermal reactor at 200-220° C. for 20-22 hours. 5. the preparation method of titanium dioxide nanosheet load MIL‐100 (Fe) composite photocatalytic material according to claim 1, is characterized in that, step 2) described in titanium dioxide nanosheet, iron trichloride dehydrated alcohol solution , The mass ratio of trimesic acid absolute ethanol solution is 1:0.2-0.5:0.1-0.4. 6. the preparation method of titanium dioxide nanosheet load MIL‐100 (Fe) composite photocatalytic material according to claim 5, is characterized in that, described titanium dioxide nanosheet, ferric chloride dehydrated alcoholic solution, trimesis The mass ratio of the formic acid absolute ethanol solution is 1:0.30-0.35:0.25-0.30. 7. the preparation method of titanium dioxide nanosheet load MIL-100 (Fe) composite photocatalytic material according to claim 1, it is characterized in that, the product obtained after suction filtration and separation in step 2), repeat step 2) times is 10 to 30 times. 8. The preparation method of titanium dioxide nanosheet-loaded MIL-100 (Fe) composite photocatalytic material according to claim 1, characterized in that, the water bath reaction temperature described in step 2) is 60-70°C, and the time is 30 ~40min, the product obtained after suction filtration and separation, repeat step 2) for 15-20 times. 9. The application method of the titanium dioxide nanosheet loaded MIL-100 (Fe) composite photocatalytic material prepared according to any one of claims 1 to 8, characterized in that 20 mg of titanium dioxide nanosheet loaded MIL-100 (Fe) The composite material is added to the methylene blue aqueous solution with a concentration of 50mg/L, and then 0.2ml H ₂ O ₂ is added, and the ultrasonic dispersion is uniform, and the dark reaction is performed for 60 minutes. degradation reaction.