Quercetin / covalent organic framework composite photocatalytic material and its preparation method and application

Abstract

The present invention relates to a quercetin / covalent organic framework composite photocatalytic material, its preparation method, and application. The composite photocatalytic material is prepared from quercetin and a covalent organic framework material via a solvothermal method. The quercetin in the composite photocatalytic material can sensitize the covalent organic framework material, improving the separation and transfer of photogenerated electrons and holes, effectively utilizing photogenerated carriers, and exhibiting good stability. The composite photocatalytic material can be used for full-spectrum photocatalytic production of hydrogen peroxide in water and benzyl alcohol, enabling the production of clean energy from solar energy.

Description

Technical Field

[0001] The present invention relates to the field of material synthesis, and in particular to a quercetin / covalent organic framework composite photocatalytic material and a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is a widely used green oxidant. Due to its safe operation, high oxidation potential, mildness, and environmental friendliness, it has a wide range of applications in wastewater treatment, paper bleaching, medical disinfection, chemical synthesis, and fuel cells. Furthermore, H2O2 is emerging as a promising green energy carrier because it has a higher energy density than compressed hydrogen and is easy to store and transport.

[0003] Currently, the main methods for producing H2O2 include persulfate electrolysis, electrochemical oxygen reduction, direct synthesis of hydrogen peroxide from H2 and O2, and anthraquinone oxidation. However, these methods have disadvantages such as complex reaction processes, high energy consumption, and the generation of toxic waste. Solar-driven photocatalytic oxygen reduction and water oxidation to produce H2O2 has become an environmentally friendly and sustainable alternative. Covalent organic frameworks (COFs), as a new type of organic porous materials, have attracted widespread attention in the field of photocatalysis due to their tunable structure, excellent stability, large specific surface area, abundant active sites, tunable energy band structure, and wide light absorption range. However, single semiconductor photocatalysts still have disadvantages such as narrow absorption spectrum, easy recombination of photogenerated carriers, and low solar energy utilization. Summary of the Invention

[0004] In view of this,

[0005] The first object of the present invention is to provide a covalent organic framework material and a preparation method thereof. The covalent organic framework material prepared by the method of the present invention has the characteristics of stable physicochemical properties, good crystal structure, high specific surface area, and easy modification.

[0006] The second purpose of the present invention is to provide a quercetin / covalent organic framework composite photocatalytic material and its preparation method and application. The composite photocatalytic material is a quercetin-sensitized covalent organic framework material, has good absorption capacity for ultraviolet-visible light, and can be used for photocatalytic production of hydrogen peroxide.

[0007] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0008] Firstly,

[0009] An embodiment of the present invention provides a method for preparing a covalent organic framework material, comprising the following steps:

[0010] 1,3,6,8-tetrakis(4-aminophenyl)-pyrene and 2,5-dihydroxyterephthalaldehyde are dissolved in a mixed solution of o-dichlorobenzene and n-butanol in a volume ratio of 1:1, and after ultrasonic dispersion, acetic acid solution is added. All the reactants are poured into a reactor, and then reacted in a forced air drying oven at 80-150°C for 24-96 hours to obtain a solid product. The obtained solid product is washed alternately with tetrahydrofuran and acetone multiple times, and then vacuum dried to prepare a covalent organic framework material.

[0011] In the preparation example of the covalent organic framework material, the concentration of the acetic acid solution is 5-8 mol / L, preferably 6 mol / L.

[0012] In the preparation example of the covalent organic framework material, the ratio of a mixed solution of 1,3,6,8-tetrakis(4-aminophenyl)-pyrene, 2,5-dihydroxyterephthalaldehyde, o-dichlorobenzene and n-butanol, and an acetic acid solution is: 0.03-0.07 mmol: 0.06-0.13 mmol: 5.0-8.0 mL: 0.5-0.8 mL.

[0013] Preferably, the molar ratio of 1,3,6,8-tetrakis(4-aminophenyl)-pyrene to 2,5-dihydroxyterephthalaldehyde is 1:2.

[0014] More preferably, the ratio of the mixed solution of 1,3,6,8-tetrakis(4-aminophenyl)-pyrene, 2,5-dihydroxyterephthalaldehyde, o-dichlorobenzene and 1,4-dioxane to the acetic acid solution is: 0.05 mmol: 0.1 mmol: 6.0 mL: 0.6 mL.

[0015] In the preparation example of the covalent organic framework material, the reaction temperature is 120° C. and the reaction time is 72 h.

[0016] In the preparation example of the covalent organic framework material, the vacuum drying temperature is 50-70° C. and the time is 10-15 hours.

[0017] Secondly,

[0018] An embodiment of the present invention further provides a covalent organic framework material, which is prepared by the above method.

[0019] Thirdly,

[0020] An embodiment of the present invention provides a method for preparing a quercetin / covalent organic framework composite photocatalytic material, characterized in that it includes the following steps:

[0021] The covalent organic framework material and quercetin are dispersed in a mixed solution of water and anhydrous ethanol, and sulfuric acid solution is added after ultrasonic dispersion. All the reactants are poured into a reactor, and then reacted in a forced air drying oven at 60-90°C for 12-48 hours to obtain a solid product. The obtained solid product is washed with water multiple times and then vacuum dried to obtain a quercetin / covalent organic framework composite photocatalytic material.

[0022] In the preparation example of the composite photocatalytic material, the volume ratio of water to anhydrous ethanol is (3-5): 1. Preferably, the volume ratio is 4:1.

[0023] In the preparation embodiment of the composite photocatalytic material, the concentration of the sulfuric acid solution is 0.1-0.3 mol / L. Preferably, the concentration is 0.1 mol / L.

[0024] In the preparation example of the composite photocatalytic material, the volume ratio of water, anhydrous ethanol and sulfuric acid solution is 4:1:1.

[0025] In the preparation example of the composite photocatalytic material, the ratio of quercetin, covalent organic framework material, mixed solution of water and anhydrous ethanol, and sulfuric acid solution is: 0.01-0.05 g: 0.01-0.05 g: 3.0-7.0 mL: 0.8-1.2 mL.

[0026] Preferably, the mass ratio of quercetin to the covalent organic framework material is 1:1.

[0027] More preferably, the ratio of quercetin, the covalent organic framework material, the mixed solution of water and anhydrous ethanol, and the sulfuric acid solution is: 0.03 g: 0.03 g: 5.0 mL: 1.0 mL.

[0028] In the preparation example of the composite photocatalytic material, the reaction temperature is 75° C. and the reaction time is 24 h.

[0029] In the preparation example of the composite photocatalytic material, the vacuum drying temperature is 50-70°C and the time is 10-15 hours.

[0030] An embodiment of the present invention further provides a quercetin / covalent organic framework composite photocatalytic material, which is prepared by the above-mentioned method.

[0031] Fifthly,

[0032] The embodiments of the present invention also provide the use of the quercetin / covalent organic framework composite photocatalytic material for photocatalytic production of hydrogen peroxide.

[0033] In some application examples, the photocatalytic production of hydrogen peroxide in water / benzyl alcohol is performed, wherein the light source is a xenon lamp with a full UV-visible spectrum.

[0034] The present invention has the following advantages and beneficial effects:

[0035] (1) The covalent organic framework material of the present invention has the characteristics of stable physicochemical properties, good crystal structure, high specific surface area, and easy modification.

[0036] (2) The quercetin of the present invention can sensitize the covalent organic framework material, expand the light absorption range and improve the separation and transfer efficiency of photogenerated carriers.

[0037] (3) The quercetin / covalent organic framework composite material of the present invention can efficiently produce hydrogen peroxide under the full spectrum, and the photocatalytic effect can be maintained at a good level after being reused five times after solvent elution. In some application examples, 10 mg of quercetin / covalent organic framework composite photocatalytic material was added to 50 mL of water and benzyl alcohol to produce hydrogen peroxide under the full spectrum photocatalytic efficiency of 1894.08 μmol·g -1 ·h -1 In some application examples, 10 mg of quercetin / covalent organic framework composite photocatalytic material was added to 50 mL of water and benzyl alcohol and photocatalytically produced hydrogen peroxide under a 420 nm wavelength xenon lamp, with an apparent quantum efficiency of 9.03%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0039] Figure 1 Schematic diagram of the synthesis of covalent organic framework materials and quercetin / covalent organic framework composite photocatalytic materials;

[0040] Figure 2 X-ray powder diffraction patterns of the covalent organic framework materials of Example 1 and Comparative Example 1;

[0041] Figure 3 X-ray powder diffraction patterns of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials;

[0042] Figure 4 Infrared spectra of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials;

[0043] Figure 5 X-ray photoelectron spectroscopy of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials (Quercetin / COF-3);

[0044] Figure 6Scanning electron micrographs of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials (Quercetin / COF-3); (a) is a covalent organic framework, (b) is quercetin, and (c) is a quercetin / covalent organic framework composite photocatalytic material;

[0045] Figure 7 Schematic diagram of nitrogen adsorption on covalent organic framework materials and quercetin / covalent organic framework composite photocatalytic materials (Quercetin / COF-3); (a) is the adsorption-desorption curve of the covalent organic framework material, (b) is the pore size distribution of the non-density functional model of the covalent organic framework material, (c) is the adsorption-desorption curve of the quercetin / covalent organic framework composite photocatalytic material, and (d) is the pore size distribution of the non-density functional model of the quercetin / covalent organic framework composite photocatalytic material;

[0046] Figure 8 Thermogravimetric curves of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials (Quercetin / COF-3);

[0047] Figure 9 UV-visible diffuse reflectance spectra of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials;

[0048] Figure 10 The photocurrent response curves of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials are shown;

[0049] Figure 11 Electrochemical impedance spectroscopy (EIS) of quercetin, covalent organic framework materials, and quercetin / covalent organic framework composite photocatalytic materials;

[0050] Figure 12 Schematic diagram of visible light photocatalytic production of hydrogen peroxide by 10 mg of quercetin, covalent organic framework material, and quercetin / covalent organic framework composite photocatalytic material in 50 mL of water;

[0051] Figure 13 Schematic diagram of the photocatalytic production of hydrogen peroxide by 10 mg of quercetin, a covalent organic framework material, and a quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3) in 50 mL of water and benzyl alcohol (volume ratio of 9:1); visible light is used as the light source on the left, and the full UV-visible spectrum is used as the light source on the right;

[0052] Figure 14Schematic diagram of the apparent quantum efficiency of photocatalytic production of hydrogen peroxide by 10 mg of quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3) in 50 mL of water and benzyl alcohol (volume ratio of 9:1) under xenon light sources of different wavelengths;

[0053] Figure 15 Schematic diagram of the number of reuses of quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3);

[0054] Figure 16 Schematic diagram of the long-term (6 h) photocatalytic production of hydrogen peroxide by quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3) in 50 mL of water and benzyl alcohol (volume ratio of 9:1);

[0055] Figure 17 This is the X-ray diffraction pattern of quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3) after repeated use;

[0056] Figure 18 This is the infrared spectrum of quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3) after repeated use.

[0057] In the figure, COF refers to TAPPy-Da-COF, which was prepared by the method of Example 1. DETAILED DESCRIPTION

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0059] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0060] Unless otherwise specified, the materials, reagents, and devices used in the following examples can be obtained from commercial sources or prepared according to methods in the literature.

[0061] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0062] Reagent Source:

[0063] In this example, 1,3,6,8-tetrakis(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde were purchased from Shanghai MacLean Biochemical Technology Co., Ltd., o-dichlorobenzene, n-butanol, anhydrous ethanol, concentrated sulfuric acid, glacial acetic acid, tetrahydrofuran, and acetone were purchased from Tianjin Concord Reagent Co., Ltd., and quercetin was purchased from Tianjin Xiens Biochemical Technology Co., Ltd. Potassium iodide and ammonium molybdate tetrahydrate were purchased from Kaimart (Tianjin) Chemical Technology Co., Ltd.

[0064] Example 1

[0065] A method for preparing a covalent organic framework material comprises the following steps:

[0066] 0.05 mmol of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPPy) and 0.1 mmol of 2,5-dihydroxyterephthalaldehyde (Da) were dissolved in 6.0 mL of a 1:1 volume ratio of o-dichlorobenzene and n-butanol. The mixture was ultrasonically treated for 5 minutes. After uniform dispersion, 0.6 mL of 6 mol / L aqueous acetic acid was added. The mixture was then placed in a sealed reactor and reacted at 120°C in a forced air drying oven for 72 hours. After cooling to room temperature, the solid product was obtained by centrifugation (8000 rpm for 3 minutes). The solid product was then washed three times with tetrahydrofuran and acetone alternately and dried in a vacuum drying oven at 60°C for 12 hours to obtain a covalent organic framework (TAPPy-Da-COF).

[0067] Comparative Example 1

[0068] Comparative Example 1-1

[0069] The difference from Example 1 is that in the mixed solution of o-dichlorobenzene and n-butanol, the volume ratio of o-dichlorobenzene to n-butanol is 1:3.

[0070] Comparative Example 1-2

[0071] The difference from Example 1 is that in the mixed solution of o-dichlorobenzene and n-butanol, the volume ratio of o-dichlorobenzene to n-butanol is 1:2.

[0072] Comparative Examples 1-3

[0073] The difference from Example 1 is that in the mixed solution of o-dichlorobenzene and n-butanol, the volume ratio of o-dichlorobenzene to n-butanol is 2:1.

[0074] Comparative Examples 1-4

[0075] The difference from Example 1 is that in the mixed solution of o-dichlorobenzene and n-butanol, the volume ratio of o-dichlorobenzene to n-butanol is 3:1.

[0076] Example 2

[0077] A method for preparing a quercetin / covalent organic framework composite photocatalytic material comprises the following steps:

[0078] 0.03 g of the covalent organic framework material prepared in Example 1 and 0.03 g of quercetin were weighed and added to 5.0 mL of a mixed solution of water and anhydrous ethanol (volume ratio 4:1). After ultrasonic dispersion, 1 mL of a 0.1 mol / L aqueous sulfuric acid solution was added. The mixture was then placed in a 20 mL glass bottle and reacted at 75°C in a forced air drying oven for 24 hours. After cooling to room temperature, a solid product was obtained by centrifugation (8000 rpm, 3 minutes). The solid product was then washed with water three times and dried in a vacuum drying oven at 60°C for 12 hours to obtain a quercetin / covalent organic framework composite photocatalytic material (named Quercetin / COF-3).

[0079] Example 3

[0080] Example 3-1

[0081] The difference from Example 1 is that in step (2), 0.015 g of covalent organic framework material and 0.045 g of quercetin are added so that the mass ratio of covalent organic framework material to quercetin is 1:3 respectively; the quercetin / covalent organic framework composite photocatalytic material (named Quercetin / COF-1) is finally prepared.

[0082] Example 3-2

[0083] The difference from Example 1 is that: in step (2), 0.02 g of covalent organic framework material and 0.04 g of quercetin are added so that the mass ratio of covalent organic framework material: quercetin is 1:2; the quercetin / covalent organic framework composite photocatalytic material (named Quercetin / COF-2) is finally obtained.

[0084] Example 3-3

[0085] The difference from Example 1 is that: in step (2), 0.04 g of covalent organic framework material and 0.02 g of quercetin are added respectively, so that the mass ratio of covalent organic framework material: quercetin is 2:1; the quercetin / covalent organic framework composite photocatalytic material (named Quercetin / COF-4) is finally obtained.

[0086] Examples 3-4

[0087] The difference from Example 1 is that: in step (2), 0.045 g of covalent organic framework and 0.015 g of quercetin are added respectively, so that the mass ratio of covalent organic framework material: quercetin is 3:1; the quercetin / covalent organic framework composite photocatalytic material (named Quercetin / COF-5) is finally obtained.

[0088] Experimental Example 4

[0089] Application of quercetin / covalent organic framework composite photocatalytic materials in photocatalytic hydrogen peroxide production

[0090] In the above application, the photocatalytic hydrogen peroxide production includes the following steps: weighing 10 mg of photocatalytic material into a 50 mL glass reactor, then adding 50 mL of water, or a solution of water and benzyl alcohol (volume ratio of 9:1), introducing air in the dark and stirring for 30 minutes until oxygen saturation, then using a 300W xenon lamp (visible light or ultraviolet-visible full spectrum with λ>420nm) as a light source, and conducting a photocatalytic reaction for 120 minutes. The liquid is filtered through a 0.22 μm filter membrane and the hydrogen peroxide content is tested using a UV-visible spectrophotometer.

[0091] The H2O2 content was determined by UV-visible spectrophotometer. - Restore to yellow I3 - The concentration of H2O2 was determined by potassium iodide spectrophotometry based on the principle of iodine iodide.

[0092] I3 was determined by UV-visible spectrophotometry - The concentration of H2O2 was calculated from the concentration of H2O2, and the absorption peak was 352nm. H2O2 of known concentration was added to potassium iodide solution and measured with UV-visible spectrophotometer to obtain a standard curve. - The linear relationship between the concentrations can be used to determine the H2O2 concentration of the sample. The specific experimental method is as follows: 1.0 mL of the suspension is filtered through a 0.22 μm filter to remove the photocatalyst powder. 2 mL of potassium iodide solution (1.0 M), 50 μL of ammonium molybdate tetrahydrate solution (0.4 M), and 1 mL of the sample solution are added to a 6 mL centrifuge tube, mixed evenly, and allowed to stand for 5 minutes to allow for full reaction. The absorbance of the solution is measured using UV-visible absorption spectroscopy (scanning range 300 nm to 500 nm), and the H2O2 concentration is calculated based on the absorption peak at 352 nm.

[0093] Experimental Example 5

[0094] Taking Quercetin / COF-3 as an example, the apparent quantum efficiency (AQY) of photocatalytic hydrogen peroxide production of quercetin / covalent organic framework composite photocatalytic material was tested. The measurement of the photocatalytic hydrogen peroxide apparent quantum efficiency includes the following steps: weighing 10 mg of the photocatalytic material and placing it in a 50 mL glass reactor, then adding 50 mL of a solution of water and benzyl alcohol (volume ratio of 9:1), aerating air in the dark and stirring for 30 minutes until oxygen saturation, then irradiating with a xenon lamp light source with incident light wavelengths of 420 nm, 520 nm, 600 nm, and 650 nm for 120 minutes, and taking a certain amount of liquid and filtering it through a 0.22 μm filter membrane. The content of hydrogen peroxide was tested using UV-visible spectroscopy. Finally, the AYQ was calculated by the following formula:

[0095]

[0096]

[0097] Where N a (Avogadro constant) = 6.02 × 10 23 mol -1 ; h (Planck constant) = 6.626 × 10 -34 J·s; c (speed of light) = 3×10 8 m·s -1 ; S (irradiated area) = 28.26 cm 2 ; I is the irradiation light intensity (W·cm -2 ); t is the photocatalytic time (s); λ is the wavelength of monochromatic light (nm).

[0098] Experimental Example 6

[0099] To investigate the cyclic performance of the photocatalyst of the present invention, based on the photocatalytic production of hydrogen peroxide in Example 4, the catalyst was centrifuged and washed with water multiple times, and the operation of Example 4 was repeated. The performance changes of the photocatalyst Quercetin / COF-3 prepared in Example 2 with a mass ratio of 1:1 in producing hydrogen peroxide after five cycles were compared.

[0100] Example 7

[0101] The long-term performance of the photocatalyst was verified by conducting a long-term photocatalytic H2O2 production experiment. In a reaction vessel, 10 mg of Quercetin-COF-3 prepared in Example 2 was placed in 50 mL of a two-phase system of water / benzyl alcohol (9 / 1, 45 mL / 5 mL). After air bubbling for 30 minutes in the dark, a long-term (6 h) photocatalytic experiment was conducted under full spectrum conditions. Every hour during the photocatalytic period, 1 mL of the suspension was removed using a pipette to measure H2O2 production.

[0102] The structure and performance of the quercetin / covalent organic framework composite photocatalytic material prepared by the present invention are described in detail below with reference to the accompanying drawings.

[0103] The covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention were analyzed using a Bruker D2 Phaser X-ray powder diffractometer. Figure 2 ,pass Figure 2 It can be seen that when the volume ratio of o-dichlorobenzene to n-butanol is 1:3, 1:2, 2:1, and 3:1 (Comparative Example 1), the powder XRD pattern of TAPPy-Da-COF has a low diffraction peak intensity at 3.68°, indicating poor crystallinity. When the volume ratio of o-dichlorobenzene to n-butanol is 1:1, the powder XRD pattern of TAPPy-Da-COF shows a strong diffraction peak at 3.68°, indicating high crystallinity. Therefore, TAPPy-Da-COF was prepared using a solvent with a volume ratio of o-dichlorobenzene to n-butanol of 1:1 (Example 1) for subsequent experiments.

[0104] The covalent organic framework materials and quercetin / covalent organic framework composite photocatalytic materials prepared in Examples 1 to 3 of the present invention were analyzed using a Bruker D2 Phaser X-ray powder diffractometer. Figure 3 ,pass Figure 3 As can be seen in (a), the experimental spectrum of TAPPy-Da-COF is consistent with the AA stacking model spectrum obtained by simulation calculation. Figure 10 The powder XRD patterns of TAPPy-Da-COF show diffraction peaks at 3.68°, 4.91°, 7.47°, 11.28°, 15.00° and 23.78° corresponding to the (100), (020), (220), (040), (060) and (001) crystal planes, indicating that TAPPy-Da-COF has an AA stacking structure. Figure 3 (b) X-ray powder diffraction patterns of the quercetin / COF composite photocatalytic material and the single material. The quercetin / COF composite photocatalytic material still maintains the crystalline characteristics of the COF, and the long-range ordered structure of the COF is not destroyed. At the same time, characteristic diffraction peaks of single quercetin and TAPPy-Da-COF are observed in the quercetin / COF composite material, and the intensity of the characteristic peak of quercetin gradually increases with the increase of quercetin content, indicating the successful preparation of the quercetin / COF composite material.

[0105] Infrared spectroscopy analysis

[0106] The covalent organic framework material (Example 1), quercetin and quercetin / covalent organic framework composite photocatalytic material (Examples 2-3) were analyzed using a Thermo Scientific Nicolet iS20 Fourier transform infrared spectrometer. Figure 4 As shown in (a), the stretching vibration of the NH bond in the covalent organic framework material (3430 and 3356 cm -1 ) and C=O bond stretching vibration (1667cm -1 ) disappears, and at the same time 1610cm -1 A new peak appears at , which is a typical characteristic peak of imine bond (C=N), confirming that the amino group and aldehyde group undergo Schiff base reaction to successfully form TAPPy-Da-COF. Figure 4 As shown in (b), the quercetin / covalent organic framework composite photocatalytic material has a wavelength of 1658 cm -1 The stretching vibration at 3409cm is derived from the unique C=O bond in quercetin. At the same time, the quercetin / covalent organic framework composite material has a functional group structure similar to that of quercetin and TAPPy-Da-COF, including -OH (3409cm -1 )、C=C(1510cm -1 ) bonds, indicating that the quercetin / covalent organic framework was derived from quercetin and TAPPy-Da-COF, confirming the successful compounding of the quercetin / covalent organic framework composite material.

[0107] X-ray photoelectron spectroscopy

[0108] Taking Quercetin / COF-3 prepared in Example 1 of the present invention as an example, the covalent organic framework material (Example 1), quercetin and quercetin / covalent organic framework composite photocatalytic material (Example 2) were measured by X-ray photoelectron spectroscopy using the model of the American ThermoScientific K-Alpha. Figure 5 , only C1s and O1s exist in quercetin, while the N1s peak can be clearly observed in the full spectrum of the Quercetin / COF-3 composite material, indicating that C, N and O elements exist in the Quercetin / COF-3 composite material ( Figure 5 In the C1s fine spectrum of Quercetin / COF-3, the four peaks at 290.96, 288.90, 286.43, and 284.80 eV belong to π-π*, C=N, CO, and C=C bonds, respectively ( Figure 5 (b)). At the same time, the O1s and N1s fine spectra show that Quercetin / COF-3 contains the C=O (531.44 eV) peak unique to quercetin and the C=N (400.26 eV) and CN (399.16 eV) peaks unique to TAPPy-Da-COF ( Figure 5 (c) and (d)), which further strongly supports the successful synthesis of quercetin / COF-3. Furthermore, the π-π* binding energies (BEs) of quercetin / COF-3 shifted negatively relative to those of TAPPy-Da-COF, while the BEs of quercetin / COF-3 shifted positively relative to those of quercetin. These results clearly demonstrate that quercetin binds to the covalent organic framework via π-π interactions and hydrogen bonding.

[0109] Scanning electron microscopy analysis

[0110] Taking Quercetin / COF-3 prepared in Example 2 of the present invention as an example, a scanning electron microscope of the Czech Tescan MIRA LMS was used to analyze the covalent organic framework material (Example 1) and the quercetin quercetin / covalent organic framework composite photocatalytic material (Example 2). The results are shown in FIG. Figure 6 It can be seen that the covalent organic framework material prepared by the present invention presents a stripe morphology formed by the accumulation of small particles ( Figure 6 In (a), quercetin showed a blocky structure under a scanning electron microscope with a relatively smooth surface ( Figure 6 (b)). When quercetin was compounded with TAPPy-Da-COF, small particles of TAPPy-Da-COF were observed to be evenly distributed on quercetin in the Quercetin / COF-3 composite material, and the surface of quercetin changed from smooth to rough ( Figure 6 Middle (c)) illustrates the successful complexation of the covalent organic framework material with quercetin.

[0111] Nitrogen adsorption experimental analysis

[0112] The Quercetin / COF-3 prepared in Example 1 of the present invention is used as an example for illustration. Figure 7 ,from Figure 7 It can be seen that the specific surface areas of the covalent organic framework material (Example 1) and the quercetin / covalent organic framework composite photocatalytic material (Example 2) prepared by the present invention are 1166.28 m 2 / g and 144.33m 2 / g, the specific surface area of ​​the composite material is lower than that of the single covalent organic framework material, and the nitrogen adsorption-desorption curves of the covalent organic framework material and the quercetin / covalent organic framework composite photocatalytic material are type IV, indicating the mesoporous characteristics of the material.

[0113] Stability analysis

[0114] The covalent organic framework material, quercetin and quercetin / covalent organic framework composite photocatalytic material (Quercetin / COF-3) were measured by a thermal analysis system model Rigaku TG / DTA8122, and the mass changes were recorded from room temperature to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere. Figure 8 As shown, the prepared quercetin / covalent organic framework composite photocatalytic material has good thermal stability, and the weight loss at 350°C is less than 20%.

[0115] UV-visible diffuse reflectance spectroscopy

[0116] The light absorption performance test was performed using a UV-visible diffuse reflectance spectrometer (Shimadzu UV-3600i Plus). Figure 9 As shown in the figure, the light absorption edge of quercetin is 500nm, and the light absorption edge of TAPPy-Da-COF is 650nm. Compared with single quercetin and TAPPy-Da-COF, the light absorption range of the quercetin / covalent organic framework composite material is greatly improved, even extending to the near-infrared light region, showing a wide range of ultraviolet-visible light absorption at 200-800nm, indicating its potential utilization of ultraviolet-visible light.

[0117] Photocurrent response curve analysis

[0118] The photocurrent response performance test was carried out using a Chinese CHI60-E electrochemical workstation. Figure 10 As shown, Quercetin / COF-3 has the strongest photocurrent density. The test results show that the photocurrent densities of Quercetin / COF-1, Quercetin / COF-2, Quercetin / COF-3, Quercetin / COF-4 and Quercetin / COF-5 are 0.7 μA·cm -2 , 1.4μA·cm -2 , 1.8μA·cm -2 , 0.9μA·cm -2 and 0.7 μA·cm -2 , among which Quercetin / COF-3 has the largest photocurrent density, respectively quercetin (0.5μA·cm -2 ) and TAPPy-Da-COF (0.4 μA·cm -2 ), indicating that the photogenerated carrier separation and transfer efficiency of quercetin / covalent organic framework composites are effectively improved.

[0119] Electrochemical impedance spectroscopy

[0120] Electrochemical impedance spectroscopy was performed using a Chinese CHI60-E electrochemical workstation. The curvature radius of the electrochemical impedance spectroscopy graph can effectively reflect the resistance, such as Figure 11 As shown, the quercetin / COF-3 composite material exhibits the smallest semicircle radius in the high-frequency region, which means that its interfacial charge transfer resistance is the smallest and the charge transfer rate is the fastest. The introduction of quercetin greatly reduces the resistance of the quercetin / covalent organic framework composite material during electron transfer, making it easier for electrons to transfer to TAPPy-Da-COF.

[0121] Application of quercetin / covalent organic framework composite photocatalytic materials in photocatalytic production of hydrogen peroxide

[0122] 10 mg of quercetin, TAPPy-Da-COF, and quercetin / covalent organic framework composites were photocatalytically produced under visible light (λ>420 nm) from a 300 W xenon lamp. The experiment was carried out in 50 mL of air-saturated water without sacrificial agent, and the hydrogen peroxide production was determined by potassium iodide spectrophotometry. Figure 12 As shown in Figure 2, the hydrogen peroxide production of the quercetin / COF composite was higher than that of single quercetin (20.65 μmol·g -1 ·h -1 ) or TAPPy-Da-COF (228.28 μmol·g -1 ·h -1 ) photocatalytic effect, which is due to the sensitization of TAPPy-Da-COF by quercetin. The photocatalytic production of hydrogen peroxide by quercetin / COF-1, quercetin / COF-2, quercetin / COF-3, quercetin / COF-4, and quercetin / COF-5 was 241.32 μmol·g -1 ·h -1 , 277.70 μmol·g -1 ·h -1 , 289.84 μmol·g -1 ·h -1 , 260.22 μmol·g -1 ·h -1 , 237.07 μmol·g -1 ·h -1 Among them, Quercetin / COF-3 composite photocatalyst has the best effect ,. Afterwards, benzyl alcohol was used as a sacrificial agent to further improve the photocatalytic production of hydrogen peroxide by Quercetin / COF-3. 10 mg of Quercetin / COF-3 was dispersed in 50 mL of water and benzyl alcohol (9:1) for photocatalytic production of hydrogen peroxide. The experiment was carried out under a xenon lamp visible light source (λ>420 nm). Figure 13 As shown in Figure 2, the hydrogen peroxide production of Quercetin / COF-3 composite material in water-benzyl alcohol was significantly improved, and its hydrogen peroxide production could reach 1058.47 μmol·g -1 ·h -1 , which is 3.65 times that in pure water. According to the UV-visible diffuse reflectance spectrum, quercetin as a sensitizer has strong absorption in the ultraviolet region (200-400nm). The Quercetin / COF-3 composite material inherits its strong light absorption characteristics in the ultraviolet region. Therefore, we conducted photocatalytic hydrogen peroxide production research under the full UV-visible spectrum. The experiment was carried out in water-benzyl alcohol (9:1), as shown in Figure 2. Figure 13 As shown in Figure 2, the hydrogen peroxide production of Quercetin / COF-3 composite material was further significantly improved to 1894.08 μmol·g -1 ·h -1 , which is 1.79 times that in the visible light region. The composite material has excellent hydrogen peroxide production performance under UV-visible full spectrum conditions and in water-benzyl alcohol.

[0123] Apparent quantum efficiency analysis

[0124] 10 mg of Quercetin / COF-3 was photocatalytically produced under 420 nm, 520 nm, 600 nm, and 650 nm xenon lamp light sources. The experiment was carried out in 50 mL of water-benzyl alcohol (9:1) saturated with air. Figure 14 As shown, the apparent quantum efficiency (AQY) of Quercetin / COF-3 composite material at 420nm can reach 9.03%.

[0125] Reuse analysis

[0126] Taking Quercetin / COF-3 as an example, the experiment was carried out in 50 mL of air-saturated water-benzyl alcohol (9:1) using the UV-visible full spectrum as the light source. Figure 15 As shown in the figure, after the photocatalysis-elution cycle, the photocatalytic production of hydrogen peroxide by Quercetin / COF-3 composite photocatalytic material was repeated 5 times and the yield remained at a high level.

[0127] Analysis of long-term photocatalytic experiments

[0128] Taking Quercetin / COF-3 as an example, the experiment used the full UV-visible spectrum as the light source and conducted a 6-hour continuous photocatalytic H2O2 production experiment in water-benzyl alcohol (9:1) to evaluate the long-term photostability of Quercetin-COF-3. Figure 16 As shown in the figure, after 6 h of continuous irradiation, the production of H2O2 is still gradually increasing and the rate has not decreased significantly, which means that Quercetin-COF-3 can still stably produce H2O2 after 6 h of continuous irradiation.

[0129] X-ray powder diffraction analysis after repeated use

[0130] Taking Quercetin / COF-3 as an example, the Quercetin / COF-3 material was analyzed by Bruker D2 Phaser X-ray powder diffractometer after 5 photocatalytic experiments. The results are shown in Figure 17 ,pass Figure 17 It can be seen that compared with Quercetin / COF-3 before photocatalysis, the PXRD pattern of Quercetin / COF-3 photocatalyst did not change significantly after 5 cycles, which means that its structure was well maintained after five consecutive uses and it had good cycle stability.

[0131] Infrared spectrum analysis after repeated use

[0132] Taking Quercetin / COF-3 as an example, the Fourier transform infrared spectrometer model Thermo Scientific Nicolet iS20 analyzed the Quercetin / COF-3 material after 5 photocatalytic experiments. Figure 18 As shown, compared with Quercetin / COF-3 before photocatalysis, the FT-IR spectrum of Quercetin / COF-3 photocatalyst did not change significantly after 5 cycles, which means that its structure was well maintained after five consecutive uses and it had good cycling stability.

[0133] Photocatalyst comparative example:

[0134] The present invention also compares the photocatalytic production of hydrogen peroxide performance of photocatalysts reported in the literature. As can be seen from Table 1, the quercetin / covalent organic framework composite material photocatalyst of the present invention has a good photocatalytic production effect of hydrogen peroxide and has excellent apparent quantum efficiency at 420 nm, even when the amount of photocatalyst used is small.

[0135] Table 1 Comparison of the effects of Example 1 and Comparative Example

[0136]

[0137]

[0138] References:

[0139] [1] L. Shi, L. Yang, W. Zhou, Y. Liu, L. Yin, X. Hai, H. Song, J. Ye, Photoassisted Construction of Holey Defective g-C3N4 Photocatalysts for Efficient Visible-Light-Driven H2O2 Production, Small 14 (2018) 1703142. https: / / doi.org / 10.1002 / smll.201703142.

[0140] [2] L. Ni, Y. Xiao, X. Zhou, Y. Jiang, Y. Liu, W. Zhang, J. Zhang, Z. Liu, Significantly Enhanced Photocatalytic Performance of the g-C3N4 / Sulfur-Vacancy-Containing Zn3In2S6 Heterostructure for Photocatalytic H2 and H2O2 Generation by Coupling Defects with Heterojunction Engineering, Inorganic Chemistry 61 (2022) 19552 - 19566. https: / / doi.org / 10.1021 / acs.inorgchem.2c03491.

[0141] [3] X. Yu, B. Viengkeo, Q. He, X. Zhao, Q. Huang, P. Li, W. Huang, Y. Li, Electronic Tuning of Covalent Triazine Framework Nanoshells for Highly Efficient Photocatalytic H2O2 Production, Advanced Sustainable Systems 5 (2021) 2100184. https: / / doi.org / 10.1002 / adsu.202100184.

[0142] [4]Y.Shiraishi,S.Kanazawa,Y.Sugano,D.Tsukamoto,H.Sakamoto,S.Ichikawa,T.Hirai,Highly Selective Production of Hydrogen Peroxide on Graphitic CarbonNitride(g-C3N4)Photocatalyst Activated by Visible Light,ACS Catalysis 4(2014)774-780.https: / / doi.org / 10.1021 / cs401208c.

[0143] [5]W. Zhao, P. Yan, B. Li, M. Bahri, L. Liu, X. Zhou, R. Clowes, ND Browning, Y. Wu, JW Ward, AI Cooper, Accelerated Synthesis and Discovery of Covalent OrganicFramework Photocatalysts for Hydrogen Peroxide Production, Journal of the American Chemical Society 144(2022)9902-9909. https: / / doi.org / 10.1021 / jacs.2c02666.

[0144] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0145] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a quercetin / covalent organic framework composite photocatalytic material, characterized in that: The steps include: The covalent organic framework material and quercetin are dispersed in a mixed solution of water and anhydrous ethanol, and after being uniformly dispersed by ultrasonication, a sulfuric acid solution is added. All the reactants are poured into a reactor, and then reacted in a forced air drying oven at 60-90°C for 12-48 hours to obtain a solid product. The obtained solid product is washed with water multiple times and then vacuum dried to obtain a quercetin / covalent organic framework composite photocatalytic material. The preparation method of the covalent organic framework material comprises the following steps: dissolving 1,3,6,8-tetrakis(4-aminophenyl)-pyrene and 2,5-dihydroxyterephthalaldehyde in a mixed solution of o-dichlorobenzene and n-butanol in a volume ratio of 1:1, uniformly dispersing the mixture by ultrasonication, adding an acetic acid solution, pouring all the reactants into a reactor, and then reacting in a forced air drying oven at 80-150°C for 24-96 hours to obtain a solid product, and washing the obtained solid product alternately with tetrahydrofuran and acetone multiple times, and then vacuum drying the product to obtain the covalent organic framework material.

2. The method for preparing a quercetin / covalent organic framework composite photocatalytic material according to claim 1, characterized in that: In the preparation method of the covalent organic framework material, the concentration of the acetic acid solution is 5-8 mol / L; the ratio of the mixed solution of 1,3,6,8-tetrakis(4-aminophenyl)-pyrene, 2,5-dihydroxyterephthalaldehyde, o-dichlorobenzene and n-butanol to the acetic acid solution is: 0.03-0.07 mmol: 0.06-0.13 mmol: 5.0-8.0 mL: 0.5-0.8 mL.

3. The method for preparing a quercetin / covalent organic framework composite photocatalytic material according to claim 2, characterized in that: In the preparation method of the covalent organic framework material, the concentration of the acetic acid solution is 6 mol / L; the ratio of the mixed solution of 1,3,6,8-tetrakis(4-aminophenyl)-pyrene, 2,5-dihydroxyterephthalaldehyde, o-dichlorobenzene and 1,4-dioxane to the acetic acid solution is: 0.05 mmol: 0.1 mmol: 6.0 mL: 0.6 mL.

4. The method for preparing a quercetin / covalent organic framework composite photocatalytic material according to claim 1, characterized in that: In the preparation method of the covalent organic framework material, the reaction temperature in the blast drying oven is 120° C. and the reaction time is 72 h; the vacuum drying temperature is 50-70° C. and the time is 10-15 h.

5. The method for preparing a quercetin / covalent organic framework composite photocatalytic material according to claim 1, characterized in that: The volume ratio of water to anhydrous ethanol is (3-5):1; the concentration of the sulfuric acid solution is 0.1-0.3 mol / L; the ratio of the quercetin, the covalent organic framework material, the mixed solution of water and anhydrous ethanol, and the sulfuric acid solution is: 0.01-0.05 g: 0.01-0.05 g: 3.0-7.0 mL: 0.8-1.2 mL.

6. The method for preparing a quercetin / covalent organic framework composite photocatalytic material according to claim 5, characterized in that: The volume ratio of water to anhydrous ethanol is 4:1; the concentration of the sulfuric acid solution is 0.1 mol / L; the ratio of the quercetin, the covalent organic framework material, the mixed solution of water and anhydrous ethanol, and the sulfuric acid solution is: 0.03 g: 0.03 g: 5.0 mL: 1.0 mL.

7. The method for preparing a quercetin / covalent organic framework composite photocatalytic material according to claim 1, characterized in that: In the preparation method of the quercetin / covalent organic framework composite photocatalytic material, the reaction temperature is 75°C and the reaction time is 24 hours; the vacuum drying temperature is 50-70°C and the time is 10-15 hours.

8. A quercetin / covalent organic framework composite photocatalytic material, characterized in that: The method is prepared by the method according to any one of claims 1 to 7.

9. Use of the quercetin / covalent organic framework composite photocatalytic material according to claim 8 for photocatalytic production of hydrogen peroxide.

10. The use according to claim 9, characterized in that Used for photocatalytic production of hydrogen peroxide in water / benzyl alcohol, the light source is a xenon lamp with a full UV-visible spectrum.

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