阅读说明：本技术 一种三氧化钨/zif-8复合催化剂的合成方法 (Synthetic method of tungsten trioxide/ZIF-8 composite catalyst ) 是由 汪瑾 潘家梁 徐芳 武大鹏 高志勇 王栋 蒋凯 于 2020-03-30 设计创作，主要内容包括：本发明属于光催化技术领域,具体涉及一种三氧化钨/ZIF-8复合催化剂的合成方法,至少包括以下步骤：(1)将三氧化钨纳米片分散在去离子水中,并向其中加入2-甲基咪唑水溶液并超声5-15min；(2)逐滴滴加2-甲基咪唑水溶液,搅拌8-15min；(3)加入现配制的醋酸锌水溶液,在室温下搅拌1.5-2.5h；(4)用洗涤液进行洗涤并干燥即得目标产物。三氧化钨具有较高的氧化还原电位,而ZIF-8是一种结晶性的多孔材料,具有较高的比表面积、多孔结构和丰富的路易斯碱位,具有较高的吸附能力,利用二者各自的优点并将其结合起来制备了一种复合物,能够有效提高三氧化钨的吸附能力。(The invention belongs to the technical field of photocatalysis, and particularly relates to a synthesis method of a tungsten trioxide/ZIF-8 composite catalyst, which at least comprises the following steps: (1) dispersing tungsten trioxide nano sheets in deionized water, adding a 2-methylimidazole water solution into the tungsten trioxide nano sheets, and carrying out ultrasonic treatment for 5-15 min; (2) dropwise adding 2-methylimidazole water solution, and stirring for 8-15 min; (3) adding the prepared zinc acetate aqueous solution, and stirring at room temperature for 1.5-2.5 h; (4) washing with a washing solution and drying to obtain the target product. Tungsten trioxide has higher oxidation-reduction potential, ZIF-8 is a crystalline porous material, has higher specific surface area, porous structure and abundant Lewis basic sites, has higher adsorption capacity, and prepares a compound by combining the advantages of the tungsten trioxide and the ZIF-8, and can effectively improve the adsorption capacity of the tungsten trioxide.)

1. A synthetic method of a tungsten trioxide/ZIF-8 composite catalyst is characterized by at least comprising the following steps:

(1) dispersing tungsten trioxide nano sheets in deionized water, adding a 2-methylimidazole water solution into the tungsten trioxide nano sheets, and carrying out ultrasonic treatment for 5-15 min;

(2) dropwise adding 2-methylimidazole water solution, and stirring for 8-15 min;

(3) adding the prepared zinc acetate aqueous solution, and stirring at room temperature for 1.5-2.5 h;

(4) washing with a washing solution and drying to obtain the target product.

2. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 1, wherein the method comprises the steps of: the preparation method of the tungsten trioxide nanosheet comprises the following steps: dissolving sodium tungstate dihydrate and polyvinylpyrrolidone in deionized water; and then dropwise adding acetic acid to obtain a mixed solution, carrying out ultrasonic treatment on the mixed solution for 30 minutes, then placing the mixed solution into an autoclave for reaction for 7-9 hours, wherein the reaction temperature is 180-220 ℃, naturally cooling to room temperature to obtain a crude product, and carrying out post-treatment on the crude product to obtain the tungsten trioxide nanosheet.

3. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 2, wherein: the work-up of the crude product comprises at least the following steps: centrifuging the crude product to collect powder, washing the powder with deionized water and absolute ethyl alcohol for 6-8 times to obtain a wet product, and drying the wet product in a vacuum drying oven.

4. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 1, wherein the method comprises the steps of: the washing liquid is a mixture of deionized water and anhydrous methanol, and the volume ratio of the deionized water to the anhydrous methanol is as follows: 1:1-2.

5. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 1, wherein the method comprises the steps of: the concentration of the 2-methylimidazole aqueous solution is 0.28-1.12 mol/L, and the concentration of the zinc acetate aqueous solution is 0.1-0.4 mol/L.

6. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 1, wherein the method comprises the steps of: the ratio of the tungsten trioxide to the amount of the 2-methylimidazole added in the step (1), the 2-methylimidazole added in the step (2), and the zinc acetate is as follows: 1:(3-6):(2.7-5.4):(11-44).

7. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 2, wherein: the mass ratio of acetic acid, sodium tungstate dihydrate, polyvinylpyrrolidone and deionized water is as follows: 1:660:100:12.

8. The method for synthesizing tungsten trioxide/ZIF-8 composite catalyst according to claim 2, wherein: the autoclave is coated with a polytetrafluoroethylene lining, and the relative molecular weight of the polyvinylpyrrolidone is 58000.

Technical Field

The invention relates to the technical field of photocatalysis, in particular to a synthetic method of a tungsten trioxide/ZIF-8 composite catalyst.

Background

Photocatalysis, which is the triggering of the cleavage of many chemical bonds under mild conditions by photoelectrons or holes generated by solar radiation, has been used to date for the decomposition of a variety of chemical bonds, such as C = O, C-C, C-H, N ≡ N. Generally, the photocatalytic reaction mainly comprises three steps: firstly, reactant molecules are adsorbed and activated on the surface of a photocatalyst; the second step is the transfer of the photocatalytic carrier between the reactant molecules and the photocatalyst; the third step is the analytical escape of the product. Firstly, the adsorption and activation of reactant molecules are key steps of the next photocatalytic reaction, the adsorption of the reactant molecules is facilitated due to the large surface area and the porous structure, and the adsorbed molecules can be activated due to unsaturated bonds on the surface. Tungsten trioxide nanosheets are reported to have a relatively high redox potential, however, tungsten trioxide has a surface area that is compromised and has very limited adsorption capacity. The ZIF-8 is a most basic unit consisting of 2-methylimidazole and metal atoms Zn, and has a higher specific surface area, a porous structure and rich Lewis base sites due to the special structure of the ZIF-8, so that the enrichment of substrate molecules is facilitated, a large number of active sites can be provided, the adsorption energy of the substrate molecules is reduced, the ZIF-8 has higher adsorption capacity, and the ZIF-8 has remarkable advantages in photocatalytic reaction.

Disclosure of Invention

The invention provides a synthesis method of a tungsten trioxide/ZIF-8 composite catalyst, and aims to provide a composite for enhancing the adsorption capacity of tungsten trioxide. The specific contents are as follows:

a synthetic method of a tungsten trioxide/ZIF-8 composite catalyst at least comprises the following steps:

(1) dispersing tungsten trioxide nano sheets in deionized water, adding a 2-methylimidazole water solution into the tungsten trioxide nano sheets, and carrying out ultrasonic treatment for 5-15 min;

(2) dropwise adding 2-methylimidazole water solution, and stirring for 8-15 min;

(3) adding the prepared zinc acetate aqueous solution, and stirring at room temperature for 1.5-2.5 h;

(4) washing with a washing solution and drying to obtain the target product.

Preferably, the preparation method of the tungsten trioxide nanosheet comprises the following steps: dissolving sodium tungstate dihydrate and polyvinylpyrrolidone in deionized water; and then dropwise adding acetic acid to obtain a mixed solution, carrying out ultrasonic treatment on the mixed solution for 30 minutes, putting the mixed solution into an autoclave for reaction for 7-9 hours, naturally cooling to room temperature to obtain a crude product, and carrying out post-treatment on the crude product to obtain the tungsten trioxide nanosheet.

Preferably, the work-up of the crude product comprises at least the following steps: centrifuging the crude product to collect powder, washing the powder with deionized water and absolute ethyl alcohol for 6-8 times to obtain a wet product, and drying the wet product in a vacuum drying oven.

Preferably, the washing liquid is a mixture of deionized water and anhydrous methanol, and the volume ratio of the two is as follows: 1:1-2.

Preferably, the concentration of the 2-methylimidazole aqueous solution is 0.28-1.12 mol/L, and the concentration of the zinc acetate aqueous solution is 0.1-0.4 mol/L.

Preferably, the ratio of tungsten trioxide to the amount of 2-methylimidazole in step (1), 2-methylimidazole in step (2) and zinc acetate added is: 1:(3-6):(2.7-5.4):(11-44).

Preferably, the mass ratio of the acetic acid, the sodium tungstate dihydrate, the polyvinylpyrrolidone and the deionized water is as follows: 1:660:100:12.

Preferably, the autoclave is coated with a polytetrafluoroethylene lining, and the polyvinylpyrrolidone has a relative molecular weight of 58000.

Compared with the prior art, the invention has the following advantages: the tungsten trioxide/ZIF-8 composite catalyst is prepared, ZIF-8 has rich pore structure and larger specific surface area, and is beneficial to enrichment of substrate molecules on the one hand, and can provide a large number of active sites on the other hand, reduce the adsorption energy of the substrate molecules and improve the adsorption/activation capacity of the substrate molecules on the other hand; the tungsten trioxide is beneficial to accelerating the migration of carriers from the catalyst body to the surface of the catalyst, so that more photo-generated carriers migrate to active sites on the surface of the catalyst to perform oxidation-reduction reaction with adsorbed substrate molecules; a heterogeneous interface is formed by ZIF-8 and tungsten trioxide, so that separation of photo-generated electrons and holes in space is realized, and the recombination efficiency of carriers is reduced; defects are constructed on the surfaces of tungsten trioxide and ZIF-8, defect sites are used as electron local centers, a channel for transferring electrons to substrate molecules is provided, and the substrate molecules are activated to promote a photocatalytic reaction. Therefore, the tungsten trioxide/ZIF-8 composite catalyst can be used as a photocatalyst to improve the performance of the material from the aspects of thermodynamics and kinetics, and finally improve the solar energy conversion efficiency.

Drawings

FIG. 1 is an SEM photograph of tungsten trioxide in accordance with example 1 of the present invention;

FIG. 2 is an SEM photograph of the tungsten trioxide/ZIF-8 composite catalyst of example 1 of the present invention;

FIG. 3 is a graph showing a comparison of the yields of nitrate radicals, which are reaction products of photocatalytic fixation of nitrogen by tungsten trioxide and a tungsten trioxide/ZIF-8 composite catalyst in example 2 of the present invention.

Detailed Description

The contents of the present invention can be more easily understood by referring to the following detailed description of preferred embodiments of the present invention and examples included therein, and unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, and in the case of contradiction, the definitions in the present specification shall control. The term "prepared from … …" as used herein is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "meaning," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of … …" excludes any unspecified elements, steps or components. If used in a claim, this phrase is intended to claim as closed, meaning that it does not include materials other than those described, except in connection with the common journal of usage. When the phrase "consisting of … …" appears in a clause of the claimed subject matter rather than immediately following the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of values, with an upper limit preferred value and a lower limit preferred value, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. "optional" or "any" means that the subsequently described event or events may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification and claims, is intended to modify a quantity, such that the invention is not limited to the specific quantity, but includes portions that are literally received for modification without substantial change in the basic function to which the invention is related. Accordingly, the use of "about" to modify a numerical value means that the invention is not limited to the precise value. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. In the present description and claims, range limitations may be combined and/or interchanged, including all sub-ranges contained therein if not otherwise stated.

In addition, the indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the stated number clearly indicates that the singular form is intended.

A synthetic method of a tungsten trioxide/ZIF-8 composite catalyst at least comprises the following steps:

(1) dispersing tungsten trioxide nano sheets in deionized water, adding a 2-methylimidazole water solution into the tungsten trioxide nano sheets, and carrying out ultrasonic treatment for 5-15 min;

(2) dropwise adding 2-methylimidazole water solution, and stirring for 8-15 min;

(3) adding the prepared zinc acetate aqueous solution, and stirring at room temperature for 1.5-2.5 h;

(4) washing with a washing solution and drying to obtain the target product.

Preferably, the preparation method of the tungsten trioxide nanosheet comprises the following steps: dissolving sodium tungstate dihydrate and polyvinylpyrrolidone in deionized water; and then dropwise adding acetic acid to obtain a mixed solution, carrying out ultrasonic treatment on the mixed solution for 30 minutes, then placing the mixed solution into an autoclave for reaction for 7-9 hours, wherein the reaction temperature is 180-220 ℃, naturally cooling to room temperature to obtain a crude product, and carrying out post-treatment on the crude product to obtain the tungsten trioxide nanosheet.

Preferably, the work-up of the crude product comprises at least the following steps: centrifuging the crude product to collect powder, washing the powder with deionized water and absolute ethyl alcohol for 6-8 times to obtain a wet product, and drying the wet product in a vacuum drying oven.

Preferably, the washing liquid is a mixture of deionized water and anhydrous methanol, and the volume ratio of the two is as follows: 1:1-2.

Preferably, the concentration of the 2-methylimidazole aqueous solution is 0.28-1.12 mol/L, and the concentration of the zinc acetate aqueous solution is 0.1-0.4 mol/L.

Preferably, the ratio of tungsten trioxide to the amount of 2-methylimidazole in step (1), 2-methylimidazole in step (2) and zinc acetate added is: 1:(3-6):(2.7-5.4):(11-44).

Preferably, the mass ratio of the acetic acid, the sodium tungstate dihydrate, the polyvinylpyrrolidone and the deionized water is as follows: 1:660:100:12.

Preferably, the autoclave is coated with a polytetrafluoroethylene lining, and the polyvinylpyrrolidone has a relative molecular weight of 58000.

The present invention will be specifically described below by way of examples. It is to be noted that the following examples are only for further illustration of the present invention and should not be construed as limiting the scope of the present invention. Many non-essential modifications and adaptations of the present invention will occur to those skilled in the art in view of the foregoing description, and are intended to be within the scope of the present invention. In addition, the starting materials used are all commercially available, unless otherwise specified.