A composite of PDI nanosheet surface growth of ZnSe nanoparticles, a preparation method and applications thereof

Abstract

The application belongs to the field of preparation of nanocomposites and application of environmental protection, and discloses a composite material of PDI nanosheet surface growth of ZnSe nanoparticles, a preparation method and application thereof. The method adopts high-temperature calcination and emulsion polymerization to prepare PDI nanosheet, and then in-situ loads ZnSe nanoparticles through a solvothermal method, successfully constructs a Z-type PDI / ZnSe composite photocatalytic material, and is used for photocatalytic preparation of hydrogen peroxide and photocatalytic reduction of hexavalent chromium ions in sewage. Due to the interface Z-type band structure, the built-in potential driving action significantly inhibits the recombination behavior of photo-generated carriers, so that the photo-generated electrons and holes maintain their strongest oxidation and reduction characteristics, and the photocatalytic activity is significantly enhanced. The raw materials used in the application are widely sourced and easy to obtain, the conditions are mild and controllable, the repeatability and feasibility are good, and in solving water pollution and synthesizing high-value-added chemicals, the application has industrialization and large-scale application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic nanocomposites, and relates to a composite material of PDI nanosheet surface growth of ZnSe nanoparticles, a preparation method and application thereof. BACKGROUND

[0002] With the continuous acceleration of global industrialization, a large amount of organic pollutants and heavy metal ions are discharged, and water pollution problems are becoming increasingly serious, which has become a global problem threatening the ecological environment and human health. Traditional treatment methods such as adsorption, membrane separation, chemical precipitation and biological treatment still have obvious limitations in treatment efficiency, secondary pollution and operation cost. Therefore, it is urgent to develop new efficient, green and sustainable treatment technologies. Semiconductor photocatalytic oxidation technology is considered as an ideal way to control environmental pollution due to its low energy consumption, simple operation, mild conditions and no secondary pollution. At the same time, photocatalysis does not require additional chemical oxidants, and has excellent environmental friendliness and industrialization potential. In addition to pollution remediation, photocatalysis also plays an important role in organic synthesis, fine chemical industry and preparation of high value-added intermediates. Based on the controllable reaction path and mild reaction conditions of photocatalysis, researchers have gradually applied it to green synthesis processes such as selective oxidation and reductive coupling, providing a new strategy for low-carbon chemistry and sustainable development. However, the existing photocatalytic materials generally have the following defects: insufficient visible light utilization, fast photoelectron-hole recombination, low quantum efficiency, and insufficient structural stability and reusability. The above problems seriously restrict the application of photocatalytic technology in practical engineering fields. Therefore, developing new photocatalysts with wide visible light response, efficient charge separation and structural stability has become the core direction and research focus of current photocatalytic technology development. The present application aims to solve the technical problems of narrow light absorption range, fast charge recombination and low catalytic efficiency of existing photocatalytic materials, and provide more application-oriented materials and process basis for environmental governance and green synthesis.

[0003] In recent years, more and more organic semiconductor materials have appeared in the field of photocatalysis. Among them, perylene diimide (PDI) is a typical organic photocatalytic material, which has attracted much attention due to its diverse structure, abundant raw materials, low price and high extinction coefficient. Especially when PDI is used as a photocatalyst, due to its internal hydrogen bond and π-π stacking structure, it provides the driving force for electron transfer and exhibits excellent oxidation performance. However, due to the presence of multiple benzene rings in its structure, the large rigid planar conjugated system determines the presence of strong intermolecular forces. This leads to poor solubility of PDI and high recombination rate of electron-hole pairs, which restricts its activity in photocatalysis. Therefore, developing efficient PDI-based composite photocatalytic materials with excellent photoelectron-hole pair separation and transmission performance is a hot research topic.

[0004] ZnSe is a typical II-VI compound semiconductor. The most common stable phase is the cubic zinc blende structure, in which each central atom is surrounded by four coordinating atoms in a tetrahedral arrangement. This arrangement results in a tight and ordered bonding between atoms, and the space group has high symmetry, providing a specific structural basis for physical processes such as electron transport and light absorption and emission. At the same time, ZnSe is a direct band gap semiconductor with a band gap of about 2.7 eV, which can absorb ultraviolet to blue-green visible light, and has good advantages in photocatalytic applications. SUMMARY

[0005] Based on the prior art and the advantages of the above two materials, the present application provides a PDI nanosheet surface growth ZnSe nanoparticle composite material, a preparation method and an application. The ZnSe and PDI nanosheet form a tight Z-type heterojunction structure, which can effectively improve the separation and transfer efficiency of carriers, and maintain good oxidation-reduction activity of carriers, thereby greatly improving the overall photocatalytic activity of PDI / ZnSe material.

[0006] A preparation method of a PDI nanosheet surface growth ZnSe nanoparticle composite photocatalytic material, characterized in that it comprises the following steps:

[0007] S1: After grinding the tetracarboxylic anhydride organic matter, amino acid and aromatic compound uniformly, heat to 80-120℃ in a tube furnace under N2 protection, calcine for 2-6 h, then disperse with ethanol, add hydrochloric acid and stir, centrifuge, wash and vacuum dry after the reaction is completed; then dissolve the obtained product in deionized water, add aliphatic organic matter, continue to stir until the solution is dark red, add hydrochloric acid again, stir and carry out polymerization reaction, the reaction time is 8-16 h, and after the reaction is completed, centrifuge, wash and vacuum dry; grind to obtain PDI nanosheet; the aliphatic organic matter is one of diethylamine, trimethylamine and triethylamine;

[0008] S2: weigh ZnCl2 and selenium powder, dissolve in an alkaline solvent, stir and mix uniformly, then add ethylenediaminetetraacetic acid, and then add hydrazine hydrate and stir and mix uniformly; weigh the PDI nanosheet prepared in step S1 and add it, ultrasonic dispersion, then transfer to a reaction kettle, heat and carry out solvothermal in-situ polymerization reaction, cool, wash, vacuum dry and grind after the reaction is completed, to obtain a PDI nanosheet surface growth ZnSe nanoparticle composite material.

[0009] Further, the molar ratio of the tetracarboxylic anhydride organic matter to the amino acid in S1 is 1:2-4.

[0010] Further, the tetracarboxylic anhydride organic matter in S1 is pyrene-3,4,9,10-tetracarboxylic dianhydride; the amino acid is one of β-alanine, D-alanine and phenylalanine; and the aromatic compound is one of imidazole, pyridine and 2-methylimidazole.

[0011] Further, in S1, the tetracarboxylic anhydride organic matter is pyrene-3,4,9,10-tetracarboxylic dianhydride, the amino acid is β-alanine, and the aromatic compound is imidazole; the amount of pyrene-3,4,9,10-tetracarboxylic dianhydride is 0.025 mmol to 1 mmol, the amount of β-alanine is 0.1 mmol to 4 mmol, and the amount of imidazole is 7.34 mmol to 102.82 mmol; the amount of triethylamine is 300 μL to 500 μL, and the sample is obtained by vacuum drying; the concentration of hydrochloric acid in the first dropwise addition is 2 mol / L, and the volume is 100 mL to 200 mL; the concentration of hydrochloric acid in the second dropwise addition is 4 mol / L, and the volume is 8 mL to 16 mL.

[0012] Further, in S2, the molar ratio of ZnCl2 to selenium powder is 1:1, and the weight of the added PDI nanosheet is 1% to 10% of the total mass of the target composite material.

[0013] Further, in S2, the basic solvent is NaOH, KOH or ammonia water, and the concentration is 2 mol / L.

[0014] Further, in S2, the amount ratio of the basic solvent, ethylenediaminetetraacetic acid, hydrazine hydrate and PDI nanosheet is 30 mL to 70 mL: 4 mmol to 8 mmol: 6 mL to 14 mL: 0.0293 g to 1.1734 g; the temperature of the solvothermal in-situ polymerization reaction is 140°C to 220°C, and the reaction time is 20 h to 28 h; the washing condition is that the PDI nanosheet surface growth ZnSe nanoparticle composite material is obtained by vacuum drying and grinding after being washed with deionized water and ethanol alternately for three times each.

[0015] The PDI nanosheet surface growth ZnSe nanoparticle composite material prepared according to the preparation method is characterized in that the composite material is composed of ZnSe nanoparticles and PDI nanosheets, and the weight percentage of the PDI nanosheet is 1% to 10%.

[0016] The application of the PDI nanosheet surface growth ZnSe nanoparticle composite material in synthesizing hydrogen peroxide is characterized in that the composite material is used as a photocatalyst to synthesize hydrogen peroxide.

[0017] The application of the PDI nanosheet surface-grown ZnSe nanoparticle composite in the treatment of synthetic wastewater, characterized in that the PDI nanosheet surface-grown ZnSe nanoparticle composite is used as a photocatalyst to treat Cr(VI) in wastewater containing heavy metal Cr(VI).

[0018] The preparation method of the PDI nanosheet surface-grown ZnSe nanoparticle photocatalytic composite disclosed in the application first prepares PDI nanosheets by high-temperature calcination and emulsion polymerization, and then in-situ loads ZnSe nanoparticles by a solvothermal method, successfully constructs a Z-type PDI / ZnSe composite structure, and benefits from the construction of the interface Z-type energy band structure, the built-in potential significantly inhibits the recombination behavior of photo-generated carriers, so that the photo-generated electrons and holes maintain their strongest oxidation and reduction characteristics, thereby significantly enhancing the photocatalytic activity of PDI / ZnSe. Compared with single materials, the PDI / ZnSe composite photocatalytic material significantly improves the production of hydrogen peroxide by photocatalysis and the efficiency of catalytic reduction of Cr(VI) in wastewater, and has industrialization promotion value.

[0019] The preparation process adopted in the application has a wide source of raw materials, is easy to obtain, has a mild and controllable operation process condition, and has good repeatability and feasibility. The method has high reaction efficiency and short synthesis time, and shows good performance potential in solving water pollution and synthesizing high-value-added chemicals, and has application prospects for industrialization and scale conversion. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The XRD graph of the PDI / ZnSe composite photocatalytic material prepared in Example 1.

[0021] Figure 2 The FT-IR graph of the PDI / ZnSe composite photocatalytic material prepared in Example 1.

[0022] Figure 3 The SEM graph of the PDI / ZnSe composite photocatalytic material prepared in Example 2.

[0023] Figure 4 The PL graph of the PDI / ZnSe composite photocatalytic material prepared in Example 3.

[0024] Figure 5 The I-t graph of the PDI / ZnSe composite photocatalytic material prepared in Example 4.

[0025] Figure 6 The UV-vis graph of the PDI / ZnSe composite photocatalytic material prepared in Example 5. DETAILED DESCRIPTION

[0026] In order to clarify the technical solutions and technical purposes of the present application, the present application will be further described below in conjunction with specific examples, but the protection scope of the present application is not limited thereto.

[0027] The photocatalytic activity of the PDI nanosheet surface-grown ZnSe nanoparticle composite material prepared in the present application is characterized by two experiments of photocatalytic preparation of H2O2 and reduction of Cr(VI) in water.

[0028] Photocatalytic preparation of H2O2: The photocatalytic H2O2 generation experiment was carried out under irradiation of a 300 W xenon lamp simulating sunlight for 1 h. The specific method is as follows: 15 mg of the PDI / ZnSe composite material prepared in the example was added into 50 mL of deionized water as a photocatalyst. Before the photocatalytic H2O2 generation reaction, a 30-minute dark reaction was carried out to ensure that the photocatalyst and air reached adsorption-desorption equilibrium. During the reaction, 1 mL of the suspension was taken from the reaction system every 10 minutes, and the photocatalyst was removed by filtration. Finally, the concentration of H2O2 was determined by iodometric method.

[0029] The photocatalytic reduction of Cr(VI) experiment was carried out in a GHX-3 type photochemical reaction instrument: 20 mg of the PDI / ZnSe composite material prepared in the example was taken as a photocatalyst and uniformly dispersed in 50 mL of a 10 ppm Cr(VI) aqueous solution. First, the mixed system was ultrasonically treated for 10 minutes to ensure sufficient dispersion, and then it was magnetically stirred in the dark for 30 minutes to allow the photocatalyst and Cr(VI) to reach adsorption-desorption equilibrium. A 300 W xenon lamp was used, equipped with a 420 nm filter, to irradiate the reaction system, and the stirring was maintained continuously. During the irradiation, 2 mL of the reaction solution was taken at certain time intervals, filtered through a microporous filter membrane, and further centrifuged to remove possible residual solids and impurities. Finally, the absorbance value of the filtrate at 540 nm wavelength was determined by ultraviolet-visible spectrophotometry. Example 1

[0030] (1) 0.0098 g of pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.0089 g of β-alanine, and 0.5 g of imidazole were weighed, uniformly ground, and then heated to 80°C in a tube furnace under N2 protection for calcination for 2 h. Subsequently, the reaction product was dispersed in 30 mL of ethanol, 100 mL of 2 mol / L hydrochloric acid was added dropwise, and the reaction was stirred. After the reaction was completed, centrifugation, washing, and vacuum drying were carried out; then the product was dissolved in 60 mL of deionized water, 300 μL of triethylamine was added, 8 mL of 4 mol / L hydrochloric acid was added dropwise, and the reaction was stirred for 8 h. After the reaction was completed, centrifugation and washing were carried out. After vacuum drying, the PDI nanosheet was obtained by grinding.

[0031] (2) 0.0098 g of pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.0089 g of β-alanine, and 0.5 g of imidazole were weighed, uniformly ground, and then heated to 80°C in a tube furnace under N2 protection for calcination for 2 h. Subsequently, the reaction product was dispersed in 30 mL of ethanol, 100 mL of 2 mol / L hydrochloric acid was added dropwise, and the reaction was stirred. After the reaction was completed, centrifugation, washing, and vacuum drying were carried out; then the product was dissolved in 60 mL of deionized water, 300 μL of triethylamine was added, 8 mL of 4 mol / L hydrochloric acid was added dropwise, and the reaction was stirred for 8 h. After the reaction was completed, centrifugation and washing were carried out. After vacuum drying, the PDI nanosheet was obtained by grinding. 2.7392 g of ZnCl2and 1.5871 g of selenium powder were dissolved in 30 mL of NaOH solution with a concentration of 2 mol / L, and after stirring, 4 mmol of ethylenediaminetetraacetic acid was added, followed by the addition of 6 mL of hydrazine hydrate, and the reaction was stirred. 0.0293 g of PDI nanosheets prepared in step (1) was weighed and added, and after ultrasonic mixing, it was transferred to a reaction kettle and heated to 140°C, and reacted for 20 h. After the reaction was completed, it was cooled to room temperature. The reaction product was washed, vacuum dried, and ground to obtain a composite material of PDI nanosheets with ZnSe nanoparticles grown on the surface, referred to as "sample 1". Among them, the content of PDI in the composite photocatalyst is 1%.

[0032] Figure 1 The XRD pattern of the composite photocatalyst sample 1 prepared according to Example 1 can be clearly seen from the figure, and the strong diffraction peaks of the prepared material indicate the high crystallinity of the prepared sample. The XRD peak shape of sample 1 is very similar to that of ZnSe, and the typical diffraction peak of PDI cannot be observed due to the small amount of PDI added. To confirm whether PDI / ZnSe composite material exists in PDI, Fourier transform infrared spectroscopy (FT-IR) test was performed on the same sample, as shown in Figure 2 ZnSe is an inorganic substance and cannot be detected for its characteristic peak. The vibration peaks at 1342 cm -1 and 1590 cm -1 belong to the stretching of the perylene ring, confirming the formation of PDI. Careful observation shows that the characteristic peaks of Example 1 are consistent with those of single-phase PDI, which strongly proves the successful construction of PDI / ZnSe composite material.

[0033] The composite photocatalytic material prepared in this example has a Cr(VI) removal efficiency of 87.46% under visible light irradiation for 50 min.

[0034] The composite photocatalytic material prepared in this example has a hydrogen peroxide production of 813.56 μM under visible light irradiation for 60 min. Example 2

[0035] (1) 0.0392 g of pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.0356 g of β-alanine, and 1 g of imidazole were weighed and ground uniformly, and then heated to 90°C in a tube furnace under N2protection for calcination for 3 h. Subsequently, the reaction product was dispersed with 40 mL of ethanol, and 125 mL of 2 mol / L hydrochloric acid was added dropwise, and the reaction was stirred. After the reaction was completed, centrifugation, washing, and vacuum drying were performed; then the obtained product was dissolved in 80 mL of deionized water, 350 μL of triethylamine was added, and 10 mL of 4 mol / L hydrochloric acid was added dropwise, and the reaction was stirred for 10 h. After the reaction was completed, centrifugation, washing, and vacuum drying were performed, and the obtained product was ground to obtain PDI nanosheets.

[0036] (2) Take 3.5842g ZnCl2and 2.0766g selenium powder were dissolved in 40mL 2 mol / L NaOH solution, after stirring, 5mmol ethylenediaminetetraacetic acid was added, then 8mL hydrazine hydrate was added, and the reaction was stirred. 0.1173g of PDI nanosheet prepared in step (1) was added, ultrasonic, transferred to the reaction kettle, heated to 160℃, and the reaction time was 22h. After the reaction was completed, it was cooled to room temperature, washed, vacuum dried, and ground to obtain a composite material of PDI nanosheet surface growing ZnSe nanoparticles, referred to as "sample 2". The content of PDI in the composite photocatalyst was 3%.

[0037] Figure 3 The SEM image of the composite photocatalyst sample 2 prepared in Example 2 is shown, and it can be seen from the figure that after the solvothermal synthesis, the ZnSe nanoparticles are firmly attached to the stacked PDI nanosheets, which indicates that the composite material has been successfully prepared, and the close combination between the two helps to form a heterojunction, thereby promoting the improvement of carrier separation and charge transport performance.

[0038] The composite photocatalytic material prepared in this example has a Cr(VI) removal efficiency of 93.27% under visible light irradiation for 50min.

[0039] The composite photocatalytic material prepared in this example has a hydrogen peroxide production of 1028.93 μM under visible light irradiation for 60min. Example 3

[0040] (1) Take 0.1177g pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.1069g β-alanine, 3g imidazole, grind uniformly, then heat and calcine in a tube furnace under N2protection, the heating temperature is 100℃, and the calcination time is 4h. Then disperse with 50mL ethanol, add 150mL 2mol / L hydrochloric acid dropwise, and stir the reaction. After the reaction was completed, centrifugation, washing, vacuum drying; then dissolve it in 100mL deionized water, add 400μL triethylamine, then add 12mL 4mol / L hydrochloric acid, stir for 12h, centrifugation, washing, vacuum drying. Grind to obtain PDI nanosheet.

[0041] (2) Take 6.3098g ZnCl2and 3.6558g selenium powder were dissolved in 50mL 2 mol / L NaOH solution, after stirring, 6mmol ethylenediaminetetraacetic acid was added, then 10mL hydrazine hydrate was added, and stirring was performed. 0.3520g of PDI nanosheets prepared in step (1) was weighed and added, ultrasonic treatment was performed, and it was transferred to a reaction kettle for heating. The reaction temperature was 180℃, the reaction time was 24h, after the reaction was completed, it was cooled to room temperature, washed, vacuum dried, and ground to obtain a composite material of PDI nanosheet surface growth of ZnSe nanoparticles, referred to as "sample 3". The content of PDI in the composite photocatalyst was 5%.

[0042] Figure 4 The PL diagram of the composite photocatalyst sample 3 prepared in Example 3 is shown. As can be seen from the diagram, the ZnSe single-component material exhibits a high fluorescence emission intensity, indicating that the photo-generated carrier recombination rate is high. In contrast, the P intensity of the PDI / ZnSe composite material is greatly reduced, which proves that the heterojunction formed between the two materials enables effective separation of photo-excited carriers.

[0043] The composite photocatalytic material prepared in this example has a Cr(VI) removal efficiency of 99.16% under visible light irradiation for 50min.

[0044] The composite photocatalytic material prepared in this example has a hydrogen peroxide production of 1375.28 μM under visible light irradiation for 60min. Example 4

[0045] (1) 0.1962g of pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.1782g of β-alanine, and 5g of imidazole were weighed, ground uniformly, and then heated to 110℃ in a tube furnace under N2protection, and calcined for 5h. Subsequently, 60mL of ethanol was used for dispersion, 175mL of 2mol / L hydrochloric acid was added dropwise, and stirring reaction was performed. After the reaction was completed, centrifugation, washing, and vacuum drying were performed; then it was dissolved in 120mL of deionized water, 450μL of triethylamine was added, 14mL of 4mol / L hydrochloric acid was added, stirring reaction was performed for 14h, centrifugation, washing, and vacuum drying were performed. Grinding obtained PDI nanosheets.

[0046] (2) 6.3098g of ZnCl2and 3.6558g of selenium powder were weighed and dissolved in 50mL of 2mol / L NaOH solution, stirring was performed, 6mmol of ethylenediaminetetraacetic acid was added, then 10mL of hydrazine hydrate was added, and stirring was performed. 0.3520g of PDI nanosheets prepared in step (1) was weighed and added, ultrasonic treatment was performed, and it was transferred to a reaction kettle for heating. The reaction temperature was 180℃, the reaction time was 24h, after the reaction was completed, it was cooled to room temperature, washed, vacuum dried, and ground to obtain a composite material of PDI nanosheet surface growth of ZnSe nanoparticles, referred to as "sample 3". The content of PDI in the composite photocatalyst was 5%. 7.3591 g ZnCl2and 4.2638 g selenium powder were dissolved in 60 mL of 2 mol / L NaOH solution, after stirring, 7 mmol of ethylenediaminetetraacetic acid was added, then 12 mL of hydrazine hydrate was added, and stirring was performed. 0.5867 g of PDI nanosheets prepared in step (1) was weighed and added, ultrasonic treatment was performed, and it was transferred to a reaction kettle for heating. The reaction temperature was 200°C, and the reaction time was 26 h. After the reaction was completed, it was cooled to room temperature, washed, and vacuum dried. Grinding obtained a composite material of PDI nanosheet surface growth of ZnSe nanoparticles, referred to as “sample 4”. The content of PDI in the composite photocatalyst was 7%.

[0047] Figure 5 The transient photocurrent diagram of the composite photocatalyst sample 4 prepared in Example 4 was obtained. As can be seen from the diagram, the PDI / ZnSe composite photocatalytic material exhibits a stronger photocurrent response than ZnSe monomer, proving that the formation of the composite material improves the charge transfer efficiency.

[0048] In order to further illustrate the advantages of the composite photocatalytic material in the present application in terms of photocatalytic reduction efficiency of hexavalent chromium ions and hydrogen peroxide production, a comparative experiment was performed. PDI and ZnSe two kinds of monomer materials were physically mixed. The experimental steps of PDI nanosheet were the same as in Example 4, and ZnSe nanoparticles were prepared without the need to add PDI nanosheet in the composite material. Under the same experimental conditions and the same PDI content, it was found that after simple physical mixing, the composite photocatalytic material prepared had a hydrogen peroxide production of 700.29 μM under visible light irradiation for 60 min, and a Cr(VI) removal efficiency of 88.13% under visible light irradiation for 50 min.

[0049] The composite photocatalytic material prepared in the present example had a Cr(VI) removal efficiency of 95.34% under visible light irradiation for 50 min.

[0050] The composite photocatalytic material prepared in the present example had a hydrogen peroxide production of 988.29 μM under visible light irradiation for 60 min. Example 5

[0051] (1) 0.3923 g of pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.3564 g of β-alanine, and 7 g of imidazole were weighed, uniformly ground, and then heated to 120°C in a tube furnace under N2protection for calcination for 6 h. Subsequently, 70 mL of ethanol was used for dispersion, 200 mL of 2 mol / L hydrochloric acid was added dropwise, and stirring reaction was performed. After the reaction was completed, centrifugation, washing, and vacuum drying were performed; then it was dissolved in 140 mL of deionized water, 500 μL of triethylamine was added, then 16 mL of 4 mol / L hydrochloric acid was added, stirring reaction was performed for 16 h, centrifugation, washing, and vacuum drying were performed. Grinding obtained PDI nanosheets.

[0052] (2) 0.3923 g of pyrene-3,4,9,10-tetracarboxylic dianhydride, 0.3564 g of β-alanine, and 7 g of imidazole were weighed, uniformly ground, and then heated to 120°C in a tube furnace under N2protection for calcination for 6 h. Subsequently, 70 mL of ethanol was used for dispersion, 200 mL of 2 mol / L hydrochloric acid was added dropwise, and stirring reaction was performed. After the reaction was completed, centrifugation, washing, and vacuum drying were performed; then it was dissolved in 140 mL of deionized water, 500 μL of triethylamine was added, then 16 mL of 4 mol / L hydrochloric acid was added, stirring reaction was performed for 16 h, centrifugation, washing, and vacuum drying were performed. Grinding obtained PDI nanosheets. 9.9621g ZnCl2and 5.7720g selenium powder were dissolved in 70mL 2 mol / L NaOH solution, after stirring, 8mmol ethylenediaminetetraacetic acid was added, then 14mL hydrazine hydrate was added, and stirred. 1.1734g of PDI nanosheets prepared in step (1) was weighed and added, ultrasonic, transferred to the reaction kettle for heating, the reaction temperature was 220℃, the reaction time was 28h, after the reaction was completed, it was cooled to room temperature, washed, vacuum dried, and ground to obtain a composite material of PDI nanosheet surface growing ZnSe nanoparticles, referred to as "sample 5". The content of PDI in the composite photocatalyst was 10%.

[0053] Figure 6 The UV-vis diagram of the composite photocatalyst sample 5 prepared in Example 5 was prepared. The absorption edge of ZnSe monomer was 506.62nm, while the light absorption cutoff edge of PDI / ZnSe composite material was 665.30nm, and a significant red shift occurred. The results showed that due to the formation of heterojunction between PDI and ZnSe, the light utilization rate of visible spectrum was enhanced, thereby leading to the enhancement of the light absorption capacity of the material.

[0054] The composite photocatalytic material prepared in this example had a Cr(VI) removal efficiency of 90.58% under visible light irradiation for 50min.

[0055] The composite photocatalytic material prepared in this example had a hydrogen peroxide production of 754.31 μM under visible light irradiation for 60min.

[0056] The above embodiments are preferred embodiments of the present application, but the present application is not limited to the above embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art without departing from the essential content of the present application shall fall within the protection scope of the present application.

Claims

1. A method for preparing a composite material in which ZnSe nanoparticles are grown on the surface of PDI nanosheets, characterized in that, Includes the following steps: S1: Weigh out tetracarboxylic anhydride organic compounds, amino acids, and aromatic compounds, grind them evenly, and heat them in a tube furnace under N2 protection to 80-120℃ for calcination for 2-6 h. Then disperse them with ethanol, add hydrochloric acid dropwise while stirring, and centrifuge, wash, and vacuum dry after the reaction is complete. Next, dissolve the obtained product in deionized water, add aliphatic organic compounds, and continue stirring until the solution turns dark red. Add hydrochloric acid dropwise again while stirring to carry out the polymerization reaction for 8-16 h. After the reaction is complete, centrifuge, wash, and vacuum dry. Grind to obtain PDI nanosheets; the aliphatic organic compounds are one of diethylamine, trimethylamine, and triethylamine. S2: Weigh ZnCl2 and selenium powder and dissolve them in an alkaline solvent. After stirring and mixing evenly, add ethylenediaminetetraacetic acid and then add hydrazine hydrate. Stir and mix evenly. Weigh the PDI nanosheets obtained in step S1 and add them to the mixture. After ultrasonic dispersion, transfer the mixture to a reaction vessel and heat it to carry out a solvothermal in-situ polymerization reaction. After the reaction is completed, cool, wash, vacuum dry and grind to obtain a composite material with ZnSe nanoparticles grown on the surface of PDI nanosheets.

2. The method for preparing the composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 1, characterized in that, The molar ratio of tetracarboxylic anhydride organic compounds to amino acids in S1 is 1:2~4.

3. The method for preparing the composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 1, characterized in that, The tetracarboxylic anhydride organic compound mentioned in S1 is pyrene-3,4,9,10-tetracarboxylic dianhydride; the amino acid is one of β-alanine, D-alanine, and phenylalanine; and the aromatic compound is one of imidazole, pyridine, and 2-methylimidazole.

4. The method for preparing the composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 3, characterized in that, In S1, the amino acid is β-alanine, the aromatic compound is imidazole, the amount of pyrene-3,4,9,10-tetracarboxylic dianhydride is 0.025 mmol to 1 mmol, the amount of β-alanine is 0.1 mmol to 4 mmol, and the amount of imidazole added is 7.34 to 102.82 mmol; the amount of triethylamine is 300 to 500 μL, and the sample is obtained by vacuum drying; the concentration of the first drop of hydrochloric acid is 2 mol / L, and the volume range is 100 to 200 mL, and the concentration of the second drop of hydrochloric acid is 4 mol / L, and the volume is 8 to 16 mL.

5. The method for preparing the composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 1, characterized in that, The molar ratio of ZnCl2 and selenium powder weighed in S2 is 1:1, and the weight of the added PDI nanosheets is 1% to 10% of the total mass of the target composite material.

6. The method for preparing the composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 1, characterized in that, The alkaline solvent mentioned in S2 is NaOH, KOH, or ammonia; the concentration is 2 mol / L.

7. The method for preparing the composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 1, characterized in that, The ratio of alkaline solvent, ethylenediaminetetraacetic acid, hydrazine hydrate, and PDI nanosheets in S2 is 30 mL~70 mL: 4 mmol~8 mmol: 6 mL~14 mL: 0.0293 g~1.1734 g; the temperature of the solvothermal in-situ polymerization reaction is 140℃~220℃, and the reaction time is 20~28 h; the washing conditions are alternating centrifugation washing with deionized water and ethanol three times each; vacuum drying and grinding are performed to obtain a composite material with ZnSe nanoparticles grown on the surface of PDI nanosheets.

8. The composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets prepared by the preparation method according to any one of claims 1-7, characterized in that, The composite material is composed of ZnSe nanoparticles and PDI nanosheets, wherein the weight percentage of PDI nanosheets is 1-10%.

9. The application of the composite material with ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 8 in the synthesis of hydrogen peroxide, characterized in that: It can be used as a photocatalyst for the synthesis of hydrogen peroxide.

10. The application of the composite material with ZnSe nanoparticles grown on the surface of PDI nanosheets according to claim 8 in the treatment of synthetic wastewater, characterized in that: The composite material of ZnSe nanoparticles grown on the surface of PDI nanosheets is used as a photocatalyst to treat and reduce Cr(VI) in wastewater containing heavy metal Cr(VI).

Images