阅读说明：本技术 金属有机骨架负载二氧化钛光催化材料及其制备方法 (Metal organic framework loaded titanium dioxide photocatalytic material and preparation method thereof ) 是由 董文钧 马雨威 海广通 王戈 于 2019-12-06 设计创作，主要内容包括：本发明公开了一种金属有机骨架负载二氧化钛光催化材料及其制备方法,具体采用界面共轭技术,通过使用羧基双齿结构将二氧化钛和金属有机骨架连接,制备二氧化钛/金属有机骨架异质结光催化剂,可以有效提高光生电子从金属有机骨架材料向二氧化钛的转移能力和光催化活性。本发明所实的制备方法、工艺简单、反应条件温和；原料及设备廉价易得,成本低；合成时间短、效率高,适合规模化生产。(The invention discloses a titanium dioxide photocatalytic material loaded on a metal organic framework and a preparation method thereof, and particularly relates to a titanium dioxide/metal organic framework heterojunction photocatalyst prepared by connecting titanium dioxide and the metal organic framework by using a carboxyl double-tooth structure by adopting an interface conjugation technology, which can effectively improve the transfer capacity and photocatalytic activity of photo-generated electrons from the metal organic framework material to the titanium dioxide. The preparation method and the process are simple, and the reaction condition is mild; the raw materials and equipment are cheap and easy to obtain, and the cost is low; short synthesis time, high efficiency and suitability for large-scale production.)

1. The preparation method of the photocatalytic material with the titanium dioxide loaded on the metal organic framework is characterized by comprising the following steps:

(1) dissolving glucose in deionized water at a concentration of 0.83mol/L, and reacting the mixed solution in a high-pressure reaction kettle at 190 ℃ for 2 h; after the reaction is finished, cooling the reaction kettle to room temperature, centrifuging, washing and drying to obtain the carbon nanospheres;

(2) dispersing the carbon nano-microspheres and water in the step (1) in absolute ethyl alcohol to form a suspension A, wherein the molar concentration of the water is 0.35mol/L, and the molar concentration of the carbon nano-microspheres is 5.56 g/L; dissolving tetrabutyl titanate in absolute ethyl alcohol by 0.13 mol/L to obtain a solution B, dropwise adding the solution B into the solution A to obtain a suspension, wherein the volume ratio of the solution B to the solution A is 1:1, then stirring the suspension for 30 minutes, finally refluxing the suspension at 80 ℃ for 5 hours, and after cooling, centrifuging, washing and drying a brown product;

(3) heating the product prepared in the step (2) to 500 ℃ by using a muffle furnace at a heating rate of 5 ℃/min, and then keeping for 2h to remove carbon nuclei, thereby finally obtaining the titanium dioxide hollow nanospheres with the oxygen vacancies;

(4) dispersing the titanium dioxide hollow nanospheres prepared in the step (3) into a certain amount of N, N-dimethylformamide solution containing diaminoterephthalic acid, wherein the mass concentration of the titanium dioxide hollow spheres is 5.0g/L, the molar concentration of the diaminoterephthalic acid is 2.0 mmol/L-8.0 mmol/L, performing ultrasonic dispersion for 30min to adsorb more carboxyl chains on the surface of titanium dioxide, then adding the suspension into an iron chloride solution with the concentration of 2.0 mmol/L-8.0 mmol/L, performing oil bath reaction for 2h at 110 ℃ and the volume ratio of the suspension to the iron chloride solution is 1:1, cooling, centrifuging, washing and drying the product.

2. The preparation method according to claim 1, wherein the washing in step (1) is 3 times of washing with absolute ethanol and deionized water, and the drying is drying the product in a vacuum oven at 80 ℃ for 12 h.

3. The preparation method according to claim 1, wherein the washing in step (2) is 3 times of washing with absolute ethanol and deionized water, and the drying is drying the product in a vacuum oven at 80 ℃ for 12h to obtain the titanium dioxide surface-supported NH₂-MIL-101(Fe) composite photocatalytic material.

4. The method according to claim 1, wherein the washing in step (4) is performed 3 times by using absolute ethanol and deionized water, and the drying is performed by drying the product in a vacuum oven at 80 ℃ for 12 hours.

5. The hollow titanium dioxide prepared by the preparation method of any one of claims 1 to 4 is loaded with a metal organic framework photocatalyst on the surface.

Technical Field

The invention belongs to the field of nano composite materials and photocatalysis, and particularly relates to a preparation method of a photocatalyst with a metal organic framework loaded on the surface of hollow titanium dioxide.

Technical Field

Water pollution is a crucial issue of general concern due to industrial development and rapid population growth. After intensive research for decades, semiconductor photocatalysis technology has been developed into an efficient technology for treating wastewater. Titanium dioxide is one of the most promising semiconductor photocatalytic materials for photocatalytic degradation of pollutants due to its low cost, non-toxicity, high cyclability and high stability. However, the large band gap limits its response to uv light only. At the same time, a higher recombination rate of photo-generated electrons leads to a lower quantum efficiency. The scholars have designed various structures to solve these problems, such as layered structures, hollow structures, etc., which can improve the quantum efficiency of titanium dioxide by using the multiple scattering effect of light. However, the low utilization of visible light by titanium dioxide still limits the use of solar energy. Therefore, the titanium dioxide hollow structure and the metal organic framework are combined to form a heterostructure, which is an effective means for effectively improving the response to visible light, enhancing the carrier separation and reducing the band gap.

The metal organic framework is a promising material, and has larger specific surface area, adjustable pore size, more active sites and stable chemical properties. Therefore, they are widely used in various fields such as chemisorption, energy storage materials and application of catalysis. Among them, titanium-based metal organic frameworks, zirconium-based metal organic frameworks, iron-based metal frameworks and copper-based metal organic frameworks are a viable photocatalyst because of their appropriate electron excitation structure from HOMO to LUMO. In particular, the iron-based metal organic framework material has remarkable achievement in the aspect of degrading organic pollutants by light under visible light because of the existence of a large number of iron-oxygen clusters. The iron-oxygen cluster can show inherent absorbance in the visible light range and can transfer electrons from O^2-Transfer to Fe^{3 +}. However, the lower carrier separation rate of the iron-based metal-organic framework material during the photocatalytic process results in lower quantum efficiency. Therefore, combining iron-based metal organic framework materials with titanium dioxide to form type II heterostructures is an effective means to solve the above problems. The iron-based metal organic framework material is anchored on the surface of titanium dioxide through a carboxyl double-tooth structureA method for heterostructure stabilization. In addition, the carboxyl bidentate structure close to the anchoring part has stronger electron-withdrawing effect, and the electron density can be pulled out from Fe-MOFs and injected into TiO₂In (1). In addition, because the carboxyl bidentate chelating structure can connect the donor and the acceptor, the migration capability of charges in the molecule from the donor to the titanium dioxide is enhanced and a conjugation effect is generated. However, few studies have been made on how to bind an iron-based metal-organic framework having a carboxyl bidentate chelate structure to titanium dioxide and improve its photocatalytic activity.

Disclosure of Invention

The invention aims to anchor a metal organic framework material to the surface of a titanium dioxide hollow nanosphere by using an organic ligand with carboxyl and using a carboxyl bidentate structure to enable the photocatalyst to have the capability of efficiently degrading organic pollutants and higher stability. The preparation scheme has low cost and wide application range.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method for anchoring a metal organic framework material to the surface of a titanium dioxide hollow nanosphere with a controllable carboxyl bidentate structure comprises the following steps:

1) fully dissolving a certain amount of glucose in deionized water, and then reacting the mixed solution in a high-pressure reaction kettle at 190 ℃ for 2 hours; and after the reaction is finished, cooling the reaction kettle to room temperature, centrifuging, washing and drying to obtain the carbon nanospheres.

(2) Dispersing a certain amount of the carbon nano microspheres in the step (1) and a certain amount of water in a certain amount of absolute ethyl alcohol to form a suspension A. Dissolving a certain amount of tetrabutyl titanate in a certain amount of absolute ethyl alcohol to obtain a solution B, and slowly dropwise adding the solution B into the solution A. The suspension was then stirred for a further 30 minutes. Finally, the suspension was refluxed at 80 ℃ for 5 h. After cooling, the brown product is centrifuged, washed and dried.

(3) And (3) keeping the product prepared in the step (2) at 500 ℃ for 2h at the heating rate of 5 ℃/min by using a muffle furnace to remove the carbon core, and finally obtaining the titanium dioxide hollow nanospheres with the oxygen vacancies.

(4) Dispersing the titanium dioxide hollow nanospheres (5.0g/L) prepared in the step (3) into a certain amount of N, N dimethylformamide solution containing diaminoterephthalic acid, and performing ultrasonic dispersion for 30min so as to adsorb more carboxyl chains on the surface of titanium dioxide. Then the suspension is added into ferric chloride solution with certain concentration, and the mixture is subjected to oil bath reaction at the temperature of 110 ℃ for 2 hours. After cooling, the product was centrifuged, washed and dried. Obtaining the titanium dioxide hollow nanosphere loaded with NH on the surface₂-MIL-101(Fe) composite photocatalytic material.

The glucose molar concentration in the step (1) is 0.83 mol/L.

The washing in the step (1) refers to washing respectively 3 times by using absolute ethyl alcohol and deionized water, and the drying refers to drying the product in a vacuum oven at 80 ℃ for 12 hours.

The molar concentration of tetrabutyl titanate in the step (2) is 0.13 mol/L. The molar concentration of water is 0.35mol/L

And (3) washing in the step (2) refers to washing respectively 3 times by using absolute ethyl alcohol and deionized water, and drying refers to drying the product in a vacuum oven at 80 ℃ for 12 hours.

The mass concentration of the titanium dioxide hollow sphere in the step (4) is 5.0g/L, the molar concentration of ferric chloride is 2.0 mmol/L-8.0 mmol/L, and the molar concentration of diamino terephthalic acid is 2.0 mmol/L-8.0 mmol/L.

And (4) washing in the step (4) refers to washing respectively 3 times by using absolute ethyl alcohol and deionized water, and drying refers to drying the product in a vacuum oven at 80 ℃ for 12 hours.

The invention also relates to the metal organic framework loaded titanium dioxide photocatalytic material prepared by the method.

The invention adopts an interface conjugation technology, and the titanium dioxide and the metal organic framework are connected by using the carboxyl double-tooth structure to prepare the titanium dioxide/metal organic framework heterojunction photocatalyst, so that the transfer capability and photocatalytic activity of photoproduction electrons from the metal organic framework material to the titanium dioxide can be effectively improved. The glucose-derived carbon nanospheres serve as a reducing agent and a template to synthesize titanium dioxide hollow nanospheres having oxygen vacancies. The bidentate chelate structure in 2-amino terephthalic acid is connected with titanium dioxide by taking the surface oxygen vacancy of the titanium dioxide as a premise. Subsequently, the metal organic framework photocatalytic material can directionally grow on the surface of the titanium dioxide. The conjugated effect between the titanium dioxide and the metal organic framework obviously enhances the transfer capability of photoproduction electrons, and can also generate a tail structure to narrow the band gap of the composite material so as to improve the photocatalysis performance, and the titanium dioxide/metal organic framework composite material has the following advantages:

(1) developing a novel metal organic framework and semiconductor titanium dioxide connection mode;

(2) the prepared titanium dioxide loaded metal organic framework can effectively improve the stability of the composite material and the efficiency of degrading pollutants by photocatalysis.

(3) The method provided by the invention has the advantages of mild reaction conditions, simple operation process and shorter reaction period, and is suitable for industrial production.

Drawings

FIG. 1 is a scanning electron microscope image of a titanium dioxide hollow sphere and titanium dioxide supported iron-based metal organic framework composite material obtained in example 1 of the present invention;

FIG. 2 is a projection electron microscope image of the titanium dioxide supported iron-based metal organic framework composite material obtained in example 1 of the present invention;

FIG. 3 shows the activity diagrams of the titanium dioxide supported iron-based metal organic framework composite material obtained in example 1 and the photocatalytic degradation of methylene blue of titanium dioxide under the irradiation of visible light;

FIG. 4 is a graph showing the circulation stability of hydrogen production by visible light of the titanium dioxide supported iron-based metal organic framework composite material obtained in example 1 of the present invention;

FIG. 5 is a schematic diagram showing the bonding manner of the iron-based metal-organic framework and titanium dioxide of the titanium dioxide-supported iron-based metal-organic framework composite material obtained in example 1 of the present invention;

fig. 6 is a schematic diagram of infrared and carboxyl structures of titanium dioxide, titanium dioxide with carboxyl bidentate structure and titanium dioxide supported iron-based metal organic framework composite material obtained in example 2 of the present invention.

Detailed Description

For the purpose of promoting a better understanding of the objects, aspects and advantages of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and specific examples