Preparation Method and Application of a Core-Shell Structure PLNPs@COFs Composite Photocatalytic Material

Abstract

Preparation method and application of a core-shell structured PLNPs@COFs composite photocatalytic material, which specifically discloses a core-shell structured PLNPs@COFs composite photocatalytic material. Among them, the core is persistent luminescence nanoparticles (PLNPs), and the shell is a covalent organic framework material (COFs), with the chemical formula (x)Zn2GeO4:Mn,Li@(y)TaPa-1-COF (1≤x≤6, 1≤y≤6). This composite material is prepared by a solvothermal method. First, separate PLNPs are synthesized. After surface modification and aldehyde group formation of the PLNPs, they are mixed evenly with the precursor of COFs, and a core-shell structured PLNPs@COFs composite material is formed by in-situ growth through a solvothermal reaction. The composite photocatalytic material prepared by the present invention has good adsorption and redox capabilities, exhibits good performance in photocatalytic degradation of pollutants, and has good application prospects in the fields of environment and energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials of photocatalysts, and particularly relates to the preparation and application of a core-shell structured PLNPs@COFs composite photocatalytic material. Background Art

[0002] With the rapid development of human industrialization, a series of environmental problems have emerged. Water pollution is one of the environmental pollutions that seriously endanger human life and health. At present, water pollution has damaged human health by destroying the river ecosystem and further damaged the economic development. Dyeing wastewater in polluted water has the characteristics of high turbidity, poor biodegradability, complex composition, and high chromaticity, and is one of the most difficult industrial wastewaters to treat. Therefore, the degradation of dyeing wastewater is the main problem in reducing environmental pollution. Photocatalytic technology directly converts solar energy into chemical energy, and has the advantages of zero pollution, low energy consumption, mild reaction conditions, etc. It has become a green technology with great potential in solving environmental problems and energy problems. In recent years, it has been widely used in the treatment of polluted water and achieved good results. At present, traditional semiconductor catalyst materials such as TiO2 and CdS have been widely studied in the field of photocatalysis. Covalent organic framework materials are porous organic crystal materials formed by covalent bonding of organic monomers, and have been used in the treatment of polluted water due to their good visible light absorption, high specific surface area, environmental friendliness, etc. However, its further application is limited due to the high electron-hole recombination rate. Long afterglow nanomaterials can also be used as photocatalysts due to their good redox ability, and because they can store light energy by themselves and slowly release the light energy after the light source is removed, they have the potential to become all-weather photocatalysts. However, their further application is limited due to their small specific surface area and narrow range of light absorption.

[0003] Therefore, in-situ growth of covalent organic framework materials on the surface of long afterglow nanomaterials to construct a core-shell heterostructure composite photocatalytic material has great scientific research significance and social and economic value. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method and application of a core-shell structured PLNPs@COFs composite photocatalytic material for the deficiencies existing in the prior art. The composite material is a (x) long afterglow nanomaterial@(y) covalent organic framework material composite (1≤x≤6, 1≤y≤6), and the (x) long afterglow nanomaterial@(y) covalent organic framework material composite has good adsorption, redox ability and a stable core-shell heterostructure.

[0005] The technical solution of the present invention:

[0006] A core-shell structured PLNPs@COFs composite photocatalytic material, where the composite photocatalytic material is: (x) long afterglow nanomaterial @ (y) covalent organic framework material, with the chemical formula (x)Zn2GeO4:Mn,Li @ (y)TaPa-1-COF, where 1 ≤ x ≤ 6 and 1 ≤ y ≤ 6, and the composite catalyst with the best effect is obtained through doping with different ratios. The x and y are respectively the mass fractions of the long afterglow nanomaterial and the covalent organic framework material. Preferably, x is 3 and y is 1.

[0007] Furthermore, the long afterglow nanomaterial in the composite photocatalytic material is the long afterglow nanomaterial PLNPs.

[0008] The preparation method of the above-mentioned PLNPs@COFs composite photocatalytic material includes the following preparation steps:

[0009] (1) Preparation of the long afterglow nanomaterial;

[0010] According to the molar ratio of 0.4:0.2:0.08:0.005 of the Zn 2+ solution, Ge 4+ solution, Li + solution, and Mn 2+ solution, add the Zn 2+ solution, Ge 4+ solution, Li + solution, and Mn 2+ solution into a container, stir well at 18 - 25 °C for 30 - 60 minutes, then adjust the pH value of the mixed solution to 7.0 - 9.0 with ammonia water with a mass percentage concentration of 12%, and continue to stir well at 18 - 25 °C for 30 - 60 minutes to obtain a precursor mixed solution; carry out a hydrothermal reaction in a stainless steel reaction kettle lined with polytetrafluoroethylene, with the reaction temperature of 160 - 170 °C and the time of 12 - 16 hours. After the hydrothermal reaction ends, let the reaction kettle cool naturally to room temperature, and wash it with absolute ethanol to finally obtain a white product;

[0011] Transfer the above white product to a muffle furnace and calcine it at 800 - 1000 °C for 2 - 4 hours to obtain the long afterglow nanomaterial.

[0012] According to the above experimental conditions, change the pH value of the precursor mixed solution, adjust the calcination temperature and calcination time respectively, and finally the optimal preparation conditions of this long afterglow nanomaterial can be determined;

[0013] Preferably, the Zn 2+ solution is an aqueous solution prepared from zinc nitrate or zinc chloride;

[0014] Preferably, the Ge 4+ solution is an aqueous solution prepared by dropping germanium oxide into ammonia water.

[0015] Preferably, the Li + solution is an aqueous solution prepared from lithium nitrate;

[0016] Preferably, the Mn 2+ is an aqueous solution prepared from manganese chloride;

[0017] Preferably, the hydrothermal reaction temperature is preferably set at 170 °C and heat-treated for 14 hours.

[0018] (2). Surface functionalization of the long afterglow nanomaterial;

[0019] Disperse the long afterglow nanomaterial obtained in step (1) in NaOH solution and stir overnight to obtain hydroxylated long afterglow nanomaterial (PLNPs-OH). Then add γ-aminopropyltriethoxysilane (APTES) to the solution containing the hydroxylated long afterglow nanomaterial, stir overnight and heat to 70-90 °C to obtain aminated long afterglow nanomaterial (PLNPs-NH2); then add phloroglucinol to the 1,4-dioxane solution containing the aminated long afterglow nanomaterial, add an appropriate amount of 5M aqueous acetic acid solution, transfer to a stainless steel reaction kettle lined with polytetrafluoroethylene for reaction, the reaction temperature is 110-130 °C, and the time is 2-4 hours to obtain aldehyde-functionalized long afterglow nanomaterial (PLNPs-CHO).

[0020] (3). Preparation of long afterglow nanomaterial@covalent organic framework material composite

[0021] Weigh the aldehyde-functionalized long afterglow nanomaterial PLNPs-CHO obtained in step (2) and the precursor of the covalent organic framework material (a mixture weighed according to the ratio of phloroglucinol to p-phenylenediamine of 0.6 mmol:0.9 mmol) in the mass fraction ratio of x long afterglow nanomaterial@y covalent organic framework material where 1 ≤ x ≤ 6 and 1 ≤ y ≤ 6 and place them in a pressure-resistant glass tube. Then add mesitylene, 1,4-dioxane, and 5M aqueous acetic acid solution according to the dosage ratio of 2:2:0.5, disperse them evenly by ultrasonic wave, perform freeze-thaw degassing three times with liquid nitrogen, and perform sealing treatment. Then transfer to a blast drying oven for reaction, the reaction temperature is 110-130 °C, and the reaction time is 70-74 hours. After the reaction, wash with tetrahydrofuran and N-N-dimethylformamide 3-6 times, soak in acetone for 46-50 hours, and then collect by centrifugation and dry in a vacuum drying oven to obtain the target product x long afterglow nanomaterial@y covalent organic framework material.

[0022] By combining the precursors of PLNPs-CHO and covalent organic framework materials in different mass fraction ratios and in-situ growing through solvothermal reaction, PLNPs@COFs composite photocatalytic materials with different ratios can be prepared. We have prepared PLNPs@COFs(1:6), PLNPs@COFs(1:3), PLNPs@COFs(1:2), PLNPs@COFs(2:1), PLNPs@COFs(3:1) and PLNPs@COFs(6:1).

[0023] The present invention also provides the application of the PLNPs@COFs composite photocatalytic material, namely (x) long afterglow nanomaterial @ (y) covalent organic framework material, in photocatalytic degradation of organic pollutants. Specifically, it can be used to degrade the pollutant Rhodamine B, and the (x) long afterglow nanomaterial @ (y) covalent organic framework material is used to degrade the Rhodamine B solution under light irradiation.

[0024] Furthermore, the light source is ultraviolet light (25W ultraviolet lamp).

[0025] Furthermore, the dosage of the PLNPs@COFs composite photocatalytic material in the Rhodamine B solution of pollutants is 0.1 - 0.3 g / L. The photocatalytic reaction time is 40 - 60 minutes.

[0026] Advantages and beneficial effects of the present invention:

[0027] The preparation method of the present invention is simple and easy to implement, the raw materials are cheap and easy to obtain, and the equipment and process are simple and easy to operate; the method of the present invention has the advantages of small reagent pollution and good reaction repeatability. The prepared (x) long afterglow nanomaterial @ (y) covalent organic framework material PLNPs@COFs(3:1) composite photocatalytic material shows good degradation effect in the process of photocatalytic degradation of Rhodamine B, and the photocatalytic performance is stable. By surface-modifying the long afterglow nanomaterial and in-situ growing the covalent organic framework material on the surface of the long afterglow nanomaterial, the obtained composite material with a core-shell structure can achieve efficient degradation of pollutants, CO2 reduction and water splitting for hydrogen evolution. Description of the drawings

[0028] Figure 1 XRD pattern of the PLNPs@COFs composite photocatalytic material prepared in Example 1.

[0029] Figure 2 TEM of the PLNPs@COFs composite photocatalytic material prepared in Example 1.

[0030] Figure 3 Degradation effect diagram of the PLNPs@COFs composite photocatalytic material prepared in Example 1 on the Rhodamine B solution. Detailed implementation manners

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, and the present invention is not limited to these embodiments only.

[0032] Example 1: Preparation of long afterglow nanomaterials, including the following steps:

[0033] According to the molar ratio of the Zn 2+ solution, Ge 4+ solution, Li + solution, and Mn 2+ solution, which is 0.4:0.2:0.08:0.005, add the Zn 2+ solution, Ge 4+ solution, Li + solution, and Mn 2+ solution into a round-bottom flask, stir well at a temperature of 18 - 25 °C for 60 minutes, then adjust the pH value of the mixed solution to 8 with ammonia water having a mass percentage concentration of 12%, and continue to stir well at a temperature of 18 - 25 °C for 60 minutes to obtain a precursor mixed solution; perform a hydrothermal reaction at 170 °C for 14 hours in a stainless steel reaction kettle lined with polytetrafluoroethylene. After the hydrothermal reaction is completed, let the reaction kettle cool naturally to room temperature, and wash it with absolute ethanol to finally obtain a white product; transfer the above white product to a muffle furnace and calcine it at 900 °C for 3 hours to obtain the long afterglow nanomaterial Zn2GeO4:Mn,Li.

[0034] The preparation of the Zn 2+ solution, Ge 4+ solution, Li + solution, and Mn 2+ solution can be seen in the part of the invention content.

[0035] Example 2:

[0036] Basically the same as Example 1, the difference is that the pH of the mixed solution precursor is changed to 7.

[0037] Example 3:

[0038] Basically the same as Example 1, the difference is that the calcination time is changed to 2 hours.

[0039] Example 4:

[0040] Basically the same as Example 1, the difference is that the calcination temperature is changed to 950 °C.

[0041] Example 5:

[0042] Preparation of a core-shell structured PLNPs@COFs composite photocatalytic material (x) long afterglow nanomaterial @ (y) covalent organic framework material, the method includes the following steps:

[0043] (1) Surface functionalization of the long-afterglow nanomaterials: 100 mg of the long-afterglow nanomaterials prepared in Example 4 were dispersed in a NaOH solution with a concentration of 5 mM and stirred overnight to obtain hydroxylated long-afterglow nanomaterials (PLNPs-OH). Then, 50 mg of APTES was added to the solution containing the hydroxylated long-afterglow nanomaterials, stirred and heated to 80 °C overnight to obtain aminated long-afterglow nanomaterials (PLNPs-NH2); then, 10 mg of phloroglucinol trialdehyde was added to the 1,4-dioxane solution containing the aminated long-afterglow nanomaterials, 0.5 mL of an acetic acid aqueous solution with a concentration of 5 M was added, and the mixture was transferred to a stainless-steel reaction kettle lined with polytetrafluoroethylene for reaction. The reaction temperature was 110 - 130 °C and the time was 2 - 4 hours to obtain aldehyde-functionalized long-afterglow nanomaterials (PLNPs-CHO).

[0044] (2) Appropriate amounts of aldehyde-functionalized long-afterglow nanomaterials PLNPs-CHO and the precursor of the covalent organic framework material (a mixture weighed according to the ratio of phloroglucinol trialdehyde to p-phenylenediamine of 0.6 mmol:0.9 mmol) were weighed according to the mass fraction ratio of x long-afterglow nanomaterials @ y covalent organic framework material precursor of 1 ≤ x ≤ 6 and 1 ≤ y ≤ 6 and placed in a pressure-resistant glass tube. Then, 2 mL of mesitylene, 2 mL of 1,4-dioxane, and 0.5 mL of an acetic acid aqueous solution with a concentration of 5 M were added. After ultrasonic dispersion and three freeze-thaw cycles of degassing with liquid nitrogen and sealing treatment, the mixture was transferred to a forced-air drying oven for reaction. The reaction temperature was 120 °C and the reaction time was 72 hours. After the reaction, it was washed 5 times with tetrahydrofuran and N,N-dimethylformamide, soaked in acetone for 48 hours, and then centrifuged and collected and dried in a vacuum drying oven to obtain the target product x long-afterglow nanomaterials @ y covalent organic framework material.

[0045] PLNPs-CHO and the precursor of the covalent organic framework material were combined in different mass fraction ratios, and PLNPs@COFs composites with different ratios could be prepared by in-situ growth through solvothermal reaction. For example, (x = 1, y = 6), (x = 1, y = 3), (x = 1, y = 2), (x = 2, y = 1), (x = 3, y = 1), and (x = 6, y = 1) were taken respectively, and we prepared PLNPs@COFs(1:6), PLNPs@COFs(1:3), PLNPs@COFs(1:2), PLNPs@COFs(2:1), PLNPs@COFs(3:1), and PLNPs@COFs(6:1). Through photocatalytic degradation experiments, it was found that with the increase of the composite material ratio, the catalytic performance first increased and then decreased, and the PLNPs@COFs(3:1) composite material had the best catalytic performance.

[0046] Figure 1 The (x) long afterglow nanomaterial @(y) covalent organic framework material composite photocatalytic material was characterized by XRD. Through the characterization, it was observed that the diffraction peaks of the composite material were consistent with the characteristic diffraction peaks of the two materials.

[0047] Figure 2 The morphology of the (x) long afterglow nanomaterial @(y) covalent organic framework material (PLNPs@COFs(3:1)) was characterized by TEM. Through the transmission electron microscope, it was observed that the covalent organic framework material was wrapped on the surface of the long afterglow nanomaterial, with the long afterglow nanomaterial as the core and the covalent organic framework material as the shell.

[0048] Figure 3 The (x) long afterglow nanomaterial @(y) covalent organic framework material composite photocatalytic material was proved to have good photocatalytic degradation ability by degrading rhodamine B solution. Among them, the PLNPs@COFs(3:1) composite material had the best catalytic performance.

[0049] Although the present invention has been described through embodiments, the embodiments are not used to limit the present invention. Those skilled in the art can make various deformations and improvements within the spirit of the present invention, such as adjusting the composition ratio or time range. The effects of such adjustments are predictable, so they are also within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the same or equivalent technical features of the claims of this application.

Claims

1. A core-shell structured PLNPs@COFs composite photocatalytic material, characterized in that: The composite photocatalytic material is: x long afterglow nanomaterial @ y covalent organic framework material, with the chemical formula xZn2GeO4:Mn,Li @ yTaPa-1-COF, where 1 ≤ x ≤ 6 and 1 ≤ y ≤ 6, and x and y are the mass fractions of the long afterglow nanomaterial and the covalent organic framework material, respectively.

2. The PLNPs@COFs composite photocatalytic material according to claim 1, wherein The x:y is 3:

1.

3. A preparation method of the PLNPs@COFs composite photocatalytic material with the core-shell structure described in claim 1, characterized in that, It includes the following steps: (1) Preparation of the long afterglow nanomaterial; Zn is added to a container in a molar ratio of 0.4:0.2:0.08:0.005 2+ solution, Ge 4+ solution, Li + solution and Mn 2+ solution are added to a container, and the mixture is stirred thoroughly for 30 - 60 minutes at a temperature of 18 - 25 °C. Then, the pH value of the mixed solution is adjusted to 7.0 - 9.0 with ammonia water, and stirring is continued for 30 - 60 minutes at a temperature of 18 - 25 °C to obtain a precursor mixed solution; a hydrothermal reaction is carried out in a stainless-steel autoclave with a polytetrafluoroethylene liner. The reaction temperature is 160 - 170 °C, and the time is 12 - 16 hours. After the hydrothermal reaction is completed, the autoclave is naturally cooled to room temperature and washed with absolute ethanol to finally obtain a white product; the above white product is transferred to a muffle furnace and calcined at 800 - 1000 °C for 2 - 4 hours to obtain a long-afterglow nanomaterial; (2) Surface functionalization of the long afterglow nanomaterial; Disperse the long afterglow nanomaterial obtained in step (1) in an NaOH solution and stir overnight to obtain hydroxylated long afterglow nanomaterial PLNPs-OH; then add γ-aminopropyltriethoxysilane to the solution containing the hydroxylated long afterglow nanomaterial, stir and heat to 70-90 °C overnight to obtain aminated long afterglow nanomaterial PLNPs-NH2; then add phloroglucinol to the 1,4-dioxane solution containing the aminated long afterglow nanomaterial, add an appropriate amount of 5M acetic acid aqueous solution, transfer to a stainless steel reaction kettle lined with polytetrafluoroethylene for reaction, the reaction temperature is 110-130 °C, and the time is 2-4 hours to obtain aldehyde-functionalized long afterglow nanomaterial PLNPs-CHO; (3) Preparation of the long afterglow nanomaterial @ covalent organic framework material composite Weigh an appropriate amount of the aldehyde-functionalized long afterglow nanomaterial PLNPs-CHO obtained in step (2) and the precursor of the covalent organic framework material according to the mass fraction ratio of 1 ≤ x ≤ 6 and 1 ≤ y ≤ 6 in x long afterglow nanomaterial @ y covalent organic framework material and place them in a pressure-resistant glass tube. Then add mesitylene, 1,4-dioxane, and 5M acetic acid aqueous solution according to the dosage ratio of 2:2:0.

5. After ultrasonic dispersion, perform freeze-thaw degassing with liquid nitrogen, and seal it. Then transfer it to a blast drying oven for solvothermal reaction. The reaction temperature is 110-130 °C, and the reaction time is 70-74 hours; after the reaction, wash with tetrahydrofuran and N,N-dimethylformamide, soak in acetone for 46-50 hours, and then collect by centrifugation and dry in a vacuum drying oven to obtain the target product x long afterglow nanomaterial @ y covalent organic framework material.

4. The preparation method of the PLNPs@COFs composite photocatalytic material according to claim 3, characterized in that, The Zn 2 + solution includes an aqueous solution prepared from zinc nitrate or zinc chloride. The Ge 4+ solution includes an aqueous solution prepared by dropping ammonia water into germanium oxide. The Li + solution includes an aqueous solution prepared from lithium nitrate. The Mn 2+ solution includes an aqueous solution prepared from manganese chloride.

5. The preparation method of the PLNPs@COFs composite photocatalytic material according to claim 3, characterized in that, The precursor of the covalent organic framework material includes a mixture weighed according to the ratio of phloroglucinol and p-phenylenediamine of 0.6 mmol:0.9 mmol.

6. Use of the PLNPs@COFs composite photocatalytic material according to claim 1 or 2, characterized in that, It is used for photocatalytic degradation of organic pollutants.

7. The application according to claim 6, wherein The organic pollutant is Rhodamine B.

8. The application according to claim 7, wherein The dosage of the PLNPs@COFs composite photocatalytic material in the Rhodamine B solution of the pollutant is 0.1-0.3 g / L.

9. According to the application described in claim 7, characterized in that, The light source for the photocatalytic degradation reaction is an ultraviolet light source; The photocatalytic reaction time is 40-60 minutes.

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