CN112691704A

CN112691704A - Flower-ball-shaped Cu-MOF-74/GO visible light catalyst and preparation method thereof

Info

Publication number: CN112691704A
Application number: CN202010880861.9A
Authority: CN
Inventors: 王睿哲
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-08-27
Filing date: 2020-08-27
Publication date: 2021-04-23

Abstract

The invention relates to the field of semiconductor photocatalytic materials, in particular to a flower-shaped spherical Cu-MOF-74/GO visible light catalyst and a preparation method thereof. The catalyst is prepared by taking N, N-Dimethylformamide (DMF) and isopropanol as solvents through solvothermal rapid preparation. The preparation method provided by the invention has the advantages that the used raw materials are simple and easy to obtain, the preparation method is simple, convenient and feasible, the cost is low, and the generation of polluting byproducts is avoided. The obtained Cu-MOF-74/GO visible light catalyst has good dispersity, excellent photocatalytic activity and good practical application prospect.

Description

Flower-ball-shaped Cu-MOF-74/GO visible light catalyst and preparation method thereof

Technical Field

The invention relates to the field of semiconductor photocatalytic materials, in particular to a flower-shaped spherical Cu-MOF-74/GO visible light catalyst and a preparation method thereof.

Background

With the rapid development of global industry, environmental problems have become increasingly prominent. Using semiconductor photocatalysts such as TiO₂The application of the method to environmental pollutant treatment has attracted more and more attention. But TiO 2₂The wide forbidden band width enables the solar cell to be excited only by ultraviolet light, the ultraviolet light only occupies a small part (less than 5%) of the solar spectrum, and meanwhile, the quantum efficiency of the solar cell is very low due to the rapid recombination of photon-generated carriers. Therefore, how to fully utilize sunlight and improve the visible light of carrier separation efficiencyCatalysts have been used as an important area of research. Metal organic framework Materials (MOFs) are porous framework materials constructed by coordination of metal ions or ion clusters and organic ligands. As the specific surface area and porosity of the MOFs are high, and the pore diameter and specific surface area are flexible and adjustable, the MOFs have potential application values in the fields of energy storage, adsorption separation, catalysis and the like. The MOFs have excellent light response performance and excellent adsorbability, and the MOFs are effectively combined to effectively and synergistically promote the photocatalysis and adsorbability. However, the current research on this aspect is still insufficient. Graphene as a novel carbon material having carbon atoms sp²A hybrid monolayer cellular crystal structure. Researchers have attracted attention in a variety of fields because of their high conductivity, chemical stability and large surface area. Graphene as a good electron acceptor can be compounded with a photocatalyst to improve photocatalytic quantum efficiency and adsorption performance. In the invention, the Cu-MOF-74 is compounded with GO with a certain oxygen-containing functional group, the combination of the Cu-MOF-74 and GO is firm, the forbidden band width can be reduced to 1.14eV, and the visible light catalytic activity for degrading pollutants is effectively improved.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: in order to solve the problems in the background art, a flower-ball-shaped Cu-MOF-74/GO composite visible light catalyst and a preparation method thereof are provided, and the flower-ball-shaped Cu-MOF-74/GO composite visible light catalyst is applied to degrading organic pollutants under visible light.

The technical scheme adopted by the invention for solving the technical problems is as follows: the invention provides a flower-shaped spherical Cu-MOF-74/GO visible light catalyst, wherein a nanorod Cu-MOF-74 is tightly combined with GO, and the Cu-MOF-74/GO compounded by the Cu-MOF-74 and GO forms a flower-shaped sphere.

The flower-ball-shaped Cu-MOF-74/GO visible light catalyst has stable and excellent photocatalytic pollutant degradation in the 420-780nm visible light wave band.

In a second aspect of the invention, a preparation method of the flower-shaped spherical Cu-MOF-74/GO visible light catalyst is provided, which comprises the following steps:

a) 2, 5-dihydroxyterephthalic acid and Cu (NO)₃)₂·3H₂Dissolving O in a mixed solution of DMF and isopropanol and carrying out short-time ultrasonic treatment to obtain a precursor solution; adding GO into the precursor solution, and performing ultrasonic treatment to obtain a mixed solution;

b) b, placing the mixed solution obtained in the step a into a polytetrafluoroethylene reaction kettle, keeping the mixed solution at 110 ℃ for 18 hours, and naturally cooling to room temperature; and washing the obtained product with DMF and methanol respectively, drying, and placing the product in vacuum at 150 ℃ overnight to obtain the flower spherical Cu-MOF-74/GO visible light catalyst.

The volume ratio of DMF to isopropanol in the mixed solution of DMF and isopropanol in the step a is 20: 1.

The Cu (NO) in the step a₃)₂·3H₂The concentrations of O and 2, 5-dihydroxyterephthalic acid in the mixed solution of DMF and isopropanol were 24.0g/L and 8.0g/L, respectively.

Cu (NO) added in the step a₃)₂·3H₂The molar ratio of O to 2, 5-dihydroxyterephthalic acid was 2: 1. Otherwise, impurities are easily formed or Cu-MOF-74 is not easily obtained.

The concentration of GO in the mixed liquid obtained in the step a is 0.40-1.50 g/L, and preferably 0.48 g/L.

The reaction temperature in the step b is 110 ℃; the reaction time was 18 h.

Preferably, the preparation method of the flower-ball-shaped Cu-MOF-74/GO visible light catalyst provided by the invention comprises the following steps:

a) 0.32g of 2, 5-dihydroxyterephthalic acid and 0.96g of Cu (NO)₃)₂·3H₂Dissolving O in a mixed solution of 38.0mL of DMF and 2.0mL of isopropanol, and performing short-time ultrasonic treatment to obtain a precursor solution; adding 18-60 mg (preferably 19mg) of GO into the precursor solution, and carrying out ultrasonic treatment to obtain a mixed solution;

More preferably, the preparation method of the flower-ball-shaped Cu-MOF-74/GO visible light catalyst provided by the invention comprises the following steps:

a) 0.32g of 2, 5-dihydroxyterephthalic acid and 0.96g of Cu (NO)₃)₂·3H₂Dissolving O in a mixed solution of 38.0mL of DMF and 2.0mL of isopropanol, violently stirring for 0.5 hour, and carrying out short-time ultrasonic treatment to obtain a precursor solution; immediately adding 18-60 mg of GO into the precursor solution, and carrying out ultrasonic treatment for 0.5 hour to obtain a mixed solution;

b) b, sealing the mixed solution obtained in the step a in a 100mL polytetrafluoroethylene reaction kettle, keeping the reaction kettle in a drying oven at the temperature of 110 ℃ for 8 hours, and naturally cooling to room temperature; the obtained precipitate is washed with DMF 1-2 times, soaked in methanol for 0.5 hr, washed and repeated four times. And (3) drying the powder in a vacuum drying oven at 60 ℃ overnight, and then placing the powder in a vacuum drying oven at 150 ℃ overnight to obtain the flower-ball-shaped Cu-MOF-74/GO visible light catalyst.

In a third aspect of the invention, the application of the flower-ball-shaped Cu-MOF-74/GO visible light catalyst is provided, and the flower-ball-shaped Cu-MOF-74/GO visible light catalyst is used for photocatalytic degradation of organic pollutants. The organic pollutant is organic dye.

Compared with the prior art, the invention has the following advantages and outstanding effects:

1. according to the invention, the Cu-MOF-74/GO is simply and rapidly prepared by taking DMF and isopropanol as solvents through a one-pot method. In the preparation process, free electrons of the Cu-MOF-74 and unpaired pi electrons of C atoms which are not completely bonded in GO can form a finally formed structure, so that the forbidden band width of the Cu-MOF-74 is reduced to 1.14eV, the quantum utilization efficiency is improved, and excellent visible light catalytic pollutant degradation is still reflected even in a long wave band. Compared with graphene, the oxygen-containing functional group of GO can react with isopropanol serving as a hydrophilic solvent, and the combination of Cu-MOF-74 and GO is facilitated.

2. The preparation method provided by the invention has the advantages of simple and easily-obtained raw materials, simple and feasible preparation method and low cost, and avoids generation of polluting byproducts. The prepared Cu-MOF-74/GO visible-light-driven photocatalyst has good dispersity, low carrier recombination rate, excellent photocatalytic activity and stability and good actual application prospect.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is an X-ray diffraction (XRD) pattern of samples prepared in examples 1 to 3 and comparative example 1;

FIG. 2(a) is a Scanning Electron Microscope (SEM) photograph of example 1;

FIG. 2(b) is a schematic view of a partially enlarged structure of (a);

FIG. 2(c) is a partially enlarged schematic view of (b);

FIG. 2(d) is a Scanning Electron Microscope (SEM) photograph of comparative example 1;

FIG. 2(e) is a Scanning Electron Microscope (SEM) photograph of example 2;

FIG. 2(f) is a Scanning Electron Microscope (SEM) photograph of example 3;

FIG. 3a is the UV absorption spectra of the solid of comparative example 1 and examples 1, 2, 3;

FIG. 3b is an energy band diagram of comparative example 1 and example 1;

FIG. 4 is a comparison of the photocatalytic activities of the visible light degradation congo red of comparative examples 1 to 3 and examples 1 to 3.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The method carries out structural characterization on the flower-ball-shaped Cu-MOF-74/GO visible light catalyst by the following means: performing structural analysis by using a Rigaku D/Max-RB type X-ray diffractometer (XRD); analyzing the morphology structure of the sample by adopting a JEOL JSM-6380LV type Scanning Electron Microscope (SEM); and performing an ultraviolet visible diffuse reflection test by adopting a spectrophotometer with the model of UV-2450.

The experimental process of degrading Congo red dye by the Cu-MOF-74/GO composite photocatalyst in the embodiment of the invention under visible light is as follows: weighing 4.5mg of catalyst, adding the catalyst into 30mL of 30mg/L Congo red solution, carrying out dark adsorption at 25 ℃ for 1.25h to achieve adsorption balance, and then carrying out a photocatalytic activity test. A300W xenon lamp is used as an irradiation light source, and light rays with the wavelength less than 420nm are filtered out. The absorbance of congo red was measured at 499nm with a UV spectrophotometer and the degradation rate was calculated therefrom. Under the condition of no illumination or no catalyst, congo red has no obvious decomposition, so that the error caused by the congo red can be ignored.

Example 1

The embodiment provides a Cu-MOF-74/GO composite photocatalytic material, which is prepared by the following steps:

0.32g of 2, 5-dihydroxyterephthalic acid and 0.96g of Cu (NO) were weighed out₃)₂·3H₂Dissolving O in a mixed solution of 38.0mL of DMF and 2.0mL of isopropanol, violently stirring for 0.5 hour, and carrying out short-time ultrasonic treatment to obtain a precursor solution; 19mg of GO is added into the precursor solution and is subjected to ultrasonic treatment for 0.5 hour to obtain a mixed solution. Sealing the obtained mixed solution in a 100mL polytetrafluoroethylene reaction kettle, keeping the sealed mixed solution in a drying oven at the temperature of 110 ℃ for 18 hours, and naturally cooling the sealed mixed solution to the room temperature; the obtained precipitate is washed with DMF 1-2 times, soaked in methanol for 0.5 hr, washed and repeated four times. And (3) drying the powder in a vacuum drying oven at 60 ℃ overnight, and then placing the powder in a vacuum drying oven at 150 ℃ overnight to obtain the flower-ball-shaped Cu-MOF-74/GO visible light catalyst.

The Cu-MOF-74/GO prepared in the example 1 is of a flower-like spherical structure, the forbidden band width of the Cu-MOF-74/GO is about 1.14eV, and the Cu-MOF-74/GO has good photocatalytic activity. FIG. 1 is an XRD spectrum of samples prepared in examples 1-3 and comparative example 1. As shown in FIG. 1, the Cu-MOF-74/GO composite catalyst shows characteristic peaks of GO at 43.43 DEG and 50.43 DEG from the characteristic peaks of Cu-MOF-74. The characteristic peaks of GO are not evident due to the small amount added. Indicating that the Cu-MOF-74/GO composite catalyst is successfully prepared. FIG. 2 shows that the samples Cu-MOF-74 and GO prepared in example 1 exist in a flower ball shape. Fig. 3a shows that the sample of the flower ball prepared in example 1 has better light absorption than comparative example 1 with a single rod-like structure, and the addition of GO improves the light energy utilization rate and promotes the photocatalytic activity. As shown in FIG. 3b, compared with the single Cu-MOF-74 of comparative example 1, the forbidden band width of the Cu-MOF-74/GO composite catalyst of example 1 is reduced from 1.44 to 1.14, so that the quantum utilization efficiency is improved, and the photocatalytic activity can be improved. The comparison of the activities in fig. 4 shows that the photocatalytic activity of example 1 is better than that of the other comparative examples and examples.

Comparative example 1

No GO is added in the preparation process, and the rest contents are the same as those described in the example 1, so that the Cu-MOF-74 photocatalyst is obtained.

The diffraction peaks of the XRD pattern of the present comparative example in FIG. 1 show that characteristic peaks of Cu-MOF-74 crystals appear at 6.74 ℃ and 11.70 ℃ while characteristic peaks also appear at 43.32 ℃ and 50.43 ℃, indicating that Cu-MOF-74 is successfully prepared. The SEM photograph in FIG. 2d shows that the pure Cu-MOF-74 catalyst of this comparative example is a rod-like structure with a rod length of about 20 microns and a diameter of about 2 microns. The comparative example in FIG. 4 has certain catalytic activity in the reaction of visible light catalytic degradation of Congo red.

Example 2

The amount of GO was changed to 38mg, and the rest of the contents were the same as those described in example 1, to obtain the visible-light-driven photocatalyst in this example.

The XRD pattern of this example in FIG. 1 shows that the prepared sample Cu-MOF-74/GO composite catalyst shows the diffraction peak of GO, and simultaneously shows the characteristic peaks of Cu-MOF-74 at 43.32 degrees and 50.43 degrees, which are consistent with the characteristic peaks of Cu-MOF-74 in comparative example 1. The characteristic peaks of GO are not evident due to the small amount added. Indicating that the Cu-MOF-74/GO composite catalyst is successfully prepared. FIG. 2e is an SEM photograph of this example, showing that the prepared sample exists in the form of a flower ball. FIG. 3a is the UV-VIS absorption spectrum of the sample of this example, showing that this example has good light absorption capability. In fig. 4, the present example has a certain catalytic activity in the visible light catalytic degradation reaction of congo red.

Example 3

The amount of GO was changed to 58mg, and the rest was the same as described in example 1, to obtain the visible-light-driven photocatalyst of this example.

The XRD pattern of this example in FIG. 1 shows that the prepared sample Cu-MOF-74/GO composite catalyst shows the diffraction peak of GO, and simultaneously shows the characteristic peaks of Cu-MOF-74 at 43.32 degrees and 50.43 degrees, which are consistent with the characteristic peaks of Cu-MOF-74 in comparative example 1. The characteristic peaks of GO are not evident due to the small amount added. Indicating that the Cu-MOF-74/GO composite catalyst is successfully prepared. FIG. 2f is an SEM photograph of this example, showing that the prepared sample exists in the form of a flower ball. Fig. 3a is the uv-vis absorption spectrum of the sample of this example, showing good light absorption capability. In fig. 4, the present example has a certain catalytic activity in the visible light catalytic degradation reaction of congo red.

Comparative example 2

Commercial P25 TiO was used₂The photocatalyst is used for degradation under Congo red visible light, and FIG. 4 shows that the comparative example has no obvious photocatalytic activity under visible light.

Comparative example 3

No catalyst is added in the process of degrading Congo red by visible light. Fig. 4 shows that in this comparative example, the single light irradiation has no obvious effect on the degradation of methyl orange.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention are equivalent to or changed within the technical scope of the present invention.

Claims

1. A preparation method of a flower-ball-shaped Cu-MOF-74/GO visible light catalyst is characterized by comprising the following steps:

a) adding Cu (NO)₃)₂·3H₂Dissolving O and 2, 5-dihydroxy terephthalic acid in a mixed solution of N, N-Dimethylformamide (DMF) and isopropanol, and performing short-time ultrasonic treatment to obtain a precursor solution; adding graphene oxide into the precursor solution and performing ultrasonic dispersion to obtain a mixed solution; the Cu (NO)₃)₂·3H₂The concentrations of O and 2, 5-dihydroxyterephthalic acid in the mixed solution of DMF and isopropanol are respectively 24.0g/L and 8.0 g/L; the added Cu (NO)₃)₂·3H₂The molar ratio of O to 2, 5-dihydroxyterephthalic acid is 2: 1;

2. The preparation method of the flower-ball-shaped Cu-MOF-74/GO visible light catalyst according to claim 1, wherein the volume ratio of DMF to isopropanol in the mixed solution in the step a is 20: 1.

3. The preparation method of the flower-shaped Cu-MOF-74/GO visible light catalyst according to claim 1, wherein the concentration of GO in the mixed liquid obtained in the step a is 0.40-1.50 g/L.

4. The preparation method of the flower-shaped Cu-MOF-74/GO visible light catalyst according to claim 1, which is characterized by comprising the following steps:

a) 0.960g of Cu (NO)₃)₂·3H₂Dissolving O and 0.320g of 2, 5-dihydroxy terephthalic acid in a mixed solution of 38.0mL of mixed solution of DMMF and 2.0mL of isopropanol, and carrying out short-time ultrasonic treatment to obtain a precursor solution; adding 18-60 mgGO into the precursor solution, and performing ultrasonic dispersion to obtain a mixed solution;

5. A flower-ball-shaped Cu-MOF-74/GO visible light catalyst, which is characterized in that the flower-ball-shaped Cu-MOF-74/GO visible light catalyst is prepared by the preparation method of any one of claims 1 to 4.

6. The visible light catalyst of claim 5, wherein the Cu-MOF-74 and GO interact to form a flower-like morphology.

7. The flower-shaped spherical Cu-MOF-74/GO visible-light-driven photocatalyst according to claim 6, wherein the flower-shaped spherical Cu-MOF-74/GO visible-light-driven photocatalyst has photocatalytic activity in the 420-780nm visible-light wavelength band.

8. The application of the flower-shaped Cu-MOF-74/GO visible light catalyst according to any one of claims 5-7, which is used for photocatalytic degradation of organic pollutants.