A covalent organic framework material and a preparation method and application thereof

Abstract

The present application belongs to the technical field of organic framework materials, and particularly relates to a kind of covalent organic framework material and its preparation method and application.The present application covalent organic framework material includes electron donor and electron acceptor;Electron donor and electron acceptor are connected by covalent bond;Electron donor includes organic ligand containing aldehyde group terminal group;Electron acceptor includes organic ligand containing amino terminal group.The present application is constructed by specific kind of electron donor-electron acceptor structure, so that the redox center in the covalent organic framework material is separated in space, which is beneficial to the rapid separation and migration of photo-generated carriers and improves the lifetime of photo-generated carriers, thereby efficient photocatalysis-piezoelectricity synergistic catalytic reaction is generated H2O2, and the yield of hydrogen peroxide can be obviously improved, and under the synergistic effect of photocatalysis-piezoelectricity, the efficiency of hydrogen peroxide produced by the material is higher than that under the condition of photocatalysis.

Description

Technical Field

[0001] This invention belongs to the field of organic framework materials technology, and specifically relates to a covalent organic framework material, its preparation method, and its application. Background Technology

[0002] As a clean and mild oxidant, hydrogen peroxide has many advantages, such as the highest content of active oxygen, excellent reactivity over a wide pH range, and the production of only non-toxic byproducts (water and oxygen) in the reaction. Therefore, hydrogen peroxide is widely used in bleaching, mining, metal processing, decontamination, wastewater treatment, and chemical organic synthesis.

[0003] Traditional methods for preparing hydrogen peroxide have several drawbacks. For example, the relatively mature anthraquinone oxidation process involves multi-step hydrogenation reactions, consuming large amounts of energy and generating polluting waste. H2O2 can be produced through the direct reaction between H2 and O2 in the presence of noble metal catalysts (such as Pd, Pt, and Pd-Au). In this reaction, H2 and O2 gases are introduced into an acidic methanol solvent, and with the aid of a catalyst, the reaction proceeds to produce H2O2 at near-0°C. However, due to the high risk of explosion and the high cost of noble metal catalysts, this method remains less than optimal. Therefore, there is an urgent need to find a green, safe, and clean method for preparing hydrogen peroxide.

[0004] Photocatalysis is a highly attractive and forward-looking solar-to-chemical energy conversion technology, potentially a major breakthrough in the field of H2O2 chemistry. It is a completely green and safe method for producing H2O2. For example, hazardous hydrogen is replaced by water, which is widely available on Earth, renewable sunlight provides all the energy for the reaction, and no pollutants are produced or emitted during the entire process. Covalent organic frameworks (COFs) are a relatively new class of non-metallic materials with high crystallinity and well-defined active sites, making them a molecular platform for photocatalytic H2O2 production. The flexibility of COF structures allows for tunability, but the efficiency of COF photocatalytic hydrogen peroxide production remains unsatisfactory.

[0005] Therefore, there is an urgent need to provide a covalent organic framework material that exhibits good photocatalytic-piezoelectric synergistic catalytic activity when applied to the preparation of hydrogen peroxide, which can significantly improve the yield of hydrogen peroxide. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions. Specifically, the present invention provides a covalent organic framework material, which, when applied to the preparation of hydrogen peroxide, exhibits good photocatalytic-piezoelectric synergistic catalytic activity and can significantly improve the yield of hydrogen peroxide.

[0007] The inventive concept of this invention: The covalent organic framework material of this invention includes an electron donor and an electron acceptor; the electron donor and the electron acceptor are connected by a covalent bond; the electron donor includes an organic ligand containing an aldehyde-terminal group; the electron acceptor includes an organic ligand containing an amino-terminal group. This invention, through the construction of a specific type of electron donor-electron acceptor structure, enables the redox centers in the COF material to be spatially separated, which facilitates the rapid separation and migration of the photogenerated support and improves its lifetime. This results in a highly efficient photocatalytic-piezoelectric synergistic catalytic reaction to produce H₂O₂, and significantly increases the yield of hydrogen peroxide.

[0008] Therefore, a first aspect of the present invention provides a covalent organic framework material.

[0009] Specifically, the covalent organic framework material includes an electron donor and an electron acceptor; the electron donor and the electron acceptor are connected by covalent bonds;

[0010] The electron donor includes an organic ligand containing an aldehyde-terminated group;

[0011] The electron acceptor includes an organic ligand containing an amino-terminal group.

[0012] Specifically, this invention improves the separation efficiency of photogenerated electron-hole pairs by introducing electron-donating groups to construct an electron donor-electron acceptor structure, thereby promoting the directional transport of photogenerated carriers and increasing the overall efficiency of oxygen reduction to produce hydrogen peroxide. This addresses the problem of low efficiency and poor utilization of photogenerated carriers in the photocatalytic synthesis of hydrogen peroxide using current covalent organic framework materials. Simultaneously, piezoelectricity is introduced during photocatalysis, creating an external internal electric field through piezoelectric potential, which promotes the separation and transport of photogenerated carriers. This results in significantly higher hydrogen peroxide activity under the synergistic effect of photocatalysis and piezoelectricity compared to the material's activity under photocatalytic hydrogen peroxide production alone. This allows the covalent organic framework material of this invention to efficiently produce hydrogen peroxide in a pure water environment without the addition of any additional sacrificial agents.

[0013] Preferably, the mass ratio of the organic ligand containing an amino-terminal group to the organic ligand containing an aldehyde-terminal group is (0.9-2.2):(0.9-2.8).

[0014] More preferably, the mass ratio of the organic ligand containing an amino-terminal group to the organic ligand containing an aldehyde-terminal group is (1-2):(1-2.5).

[0015] Preferably, the organic ligand containing an aldehyde-terminal group includes any one of 4,4',4”,4”'-([9,9'-bicarbazol]-3,3',6,6'-tetramethyl)tetrabenzaldehyde, terephthalaldehyde, and benzo[C][1,2,5]thiadiazole-4,7-dicarbaldehyde.

[0016] More preferably, the organic ligand containing the aldehyde terminal group includes 4,4',4”,4”'-([9,9'-bicarbazol]-3,3',6,6'-tetramethyl)tetrabenzaldehyde.

[0017] Preferably, the organic ligand containing an amino-terminal group includes any one of p-phenylenediamine, 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, and tri(4-aminophenyl)amine.

[0018] More preferably, the organic ligand containing an amino-terminal group includes p-phenylenediamine.

[0019] Preferably, the covalent organic framework material is selected from any one of the following structural formulas:

[0020]

[0021]

[0022]

[0023] A second aspect of the present invention provides a method for preparing the covalent organic framework material described in the first aspect of the present invention.

[0024] Specifically, the preparation method of the covalent organic framework material includes the following steps:

[0025] The covalent organic framework material is prepared by mixing an organic ligand containing an amino-terminal group, an organic ligand containing an aldehyde-terminal group, an organic solvent, and a catalyst, and reacting the mixture.

[0026] Preferably, the organic ligand containing an amino-terminal group and the organic ligand containing an aldehyde-terminal group are first dispersed uniformly in an organic solvent, and then a catalyst is added and mixed.

[0027] Preferably, ultrasonic treatment is used to ensure that the organic ligands containing amino-terminal groups and the organic ligands containing aldehyde-terminal groups are uniformly dispersed in an organic solvent.

[0028] Preferably, the ultrasonic treatment temperature is 18-33℃ and the ultrasonic treatment time is 9-22 minutes.

[0029] More preferably, the temperature of the ultrasonic treatment is 20-30℃, and the time of the ultrasonic treatment is 10-20 minutes.

[0030] Preferably, the organic solvent includes at least one selected from methanol, toluene, n-hexane, n-butanol, o-dichlorobenzene, and acetone.

[0031] More preferably, the organic solvent includes n-butanol and o-dichlorobenzene.

[0032] Preferably, the volume ratio of n-butanol to o-dichlorobenzene is 1:(0.8-1.2); more preferably, the volume ratio of n-butanol to o-dichlorobenzene is 1:(0.9-1.1); and even more preferably, the volume ratio of n-butanol to o-dichlorobenzene is 1:1.

[0033] Preferably, the catalyst comprises acetic acid.

[0034] Preferably, the concentration of the catalyst is 5-7 mol·L⁻¹. -1 More preferably, the concentration of the catalyst is 5.5-6.5 mol·L⁻¹. -1 More preferably, the concentration of the catalyst is 6 mol·L⁻¹. -1 .

[0035] Preferably, the mixing process further includes a freeze-drying process; after freeze-drying, the mixture is restored to room temperature before the reaction proceeds.

[0036] Specifically, the cryogenic degassing is performed under liquid nitrogen conditions through freeze-thaw cycles.

[0037] Preferably, the temperature during cryogenic degassing is 67-87K; more preferably, the temperature during cryogenic degassing is 72-82K; and even more preferably, the temperature during cryogenic degassing is 77K.

[0038] Specifically, during the freeze-degassing process, the mixture is first frozen and then degassed, and the mixed solution is kept frozen during the degassing process.

[0039] Preferably, degassing is performed by vacuuming.

[0040] Preferably, the vacuuming time during the freeze-drying process is 3.5-6.5 minutes; more preferably, the vacuuming time during the freeze-drying process is 4-6 minutes.

[0041] Specifically, the freeze-thaw cycle is repeated after the freezing and vacuuming process is completed and the temperature is restored to room temperature.

[0042] Specifically, the reason for thawing at room temperature is to observe the phenomenon of dissolved oxygen overflowing from the mixed solution. Since the entire system is sealed and the interior is under vacuum after evacuation, dissolved oxygen in the mixed solution will spontaneously overflow.

[0043] Preferably, the reaction temperature is 110-130℃ and the reaction time is 60-80h; more preferably, the reaction temperature is 115-125℃ and the reaction time is 65-75h.

[0044] Preferably, the reaction is a hydrothermal reaction.

[0045] Preferably, the reaction is followed by washing.

[0046] Preferably, the detergent used for washing includes at least one of dimethylbenzylamine, methanol, acetone, and ethane.

[0047] A third aspect of the present invention provides an application of the covalent organic framework material described in the first aspect of the present invention in the photocatalytic-piezoelectric synergistic preparation of hydrogen peroxide.

[0048] Specifically, the covalent organic framework material of this invention exhibits a photocatalytic-piezoelectric synergistic effect, which can improve the efficiency of hydrogen peroxide production. By introducing piezoelectricity simultaneously with photocatalysis, an external internal electric field is constructed through the piezoelectric potential, promoting the separation and transport of photogenerated carriers. As a result, the hydrogen peroxide production activity of the material under the photocatalytic-piezoelectric synergistic effect is significantly higher than that of the material performing only photocatalysis for hydrogen peroxide production.

[0049] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0050] (1) By constructing a specific type of electron donor-electron acceptor structure, the redox centers in the COF material are spatially separated, which is conducive to the rapid separation and migration of the photogenerated carrier and to improving the lifetime of the photogenerated carrier, thereby enabling efficient photocatalytic-piezoelectric synergistic catalytic reaction to produce H2O2 and significantly improving the yield of hydrogen peroxide.

[0051] (2) The covalent organic framework material Cz-CHO-COF of this invention has a photocatalytic-piezoelectric synergistic effect. Under the photocatalytic-piezoelectric synergistic effect, the efficiency of the material in producing hydrogen peroxide by photocatalysis-piezoelectric synergistic effect is higher than that under photocatalytic conditions. This is of great significance for exploring the influence of piezoelectricity on the photocatalysis of COFs and explaining its related mechanism.

[0052] (3) The covalent organic framework material of the present invention can directly generate hydrogen peroxide in pure water. This not only reduces the cost of sacrificial agents that most photocatalytic hydrogen peroxide production currently requires, but also, since no sacrificial agent is needed, after the material is filtered, only a mixture of hydrogen peroxide and water remains in the system, and no additional sacrificial agent needs to be separated, making it more convenient to use. In industrial production, the absence of sacrificial agents can be regarded as a green and environmentally friendly strategy. Attached Figure Description

[0053] Figure 1 This is a structural diagram of the covalent organic framework material Cz-CHO-COF prepared in Example 1 of the present invention;

[0054] Figure 2 This is a structural diagram of the covalent organic framework material H-COF prepared in Example 2 of the present invention;

[0055] Figure 3 This is a structural diagram of the covalent organic framework material NO-COF prepared in Example 3 of the present invention;

[0056] Figure 4 This is a transmission electron microscope image of the covalent organic framework material Cz-CHO-COF prepared in Example 1 of this invention;

[0057] Figure 5 The X-ray diffraction pattern of the covalent organic framework material Cz-CHO-COF prepared in Example 1 of this invention;

[0058] Figure 6 This is the standard curve used in this invention to determine the concentration of hydrogen peroxide;

[0059] Figure 7 This is a graph showing the efficiency of photocatalysis and photocatalysis-piezoelectric synergistic hydrogen peroxide production of the covalent organic framework material Cz-CHO-COF prepared in Example 1 of this invention. Detailed Implementation

[0060] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0061] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0062] Example 1

[0063] A covalent organic framework material includes an organic ligand p-phenylenediamine containing an amino-terminal group and an organic ligand 4,4',4”,4”'-([9,9'-bicarbazole]-3,3',6,6'-tetramethyl)tetrabenzaldehyde containing an aldehyde-terminal group, wherein p-phenylenediamine and 4,4',4”,4”'-([9,9'-bicarbazole]-3,3',6,6'-tetramethyl)tetrabenzaldehyde are covalently linked.

[0064] A method for preparing a covalent organic framework material includes the following steps:

[0065] 15 mg of p-phenylenediamine, an organic ligand containing an amino-terminal group, and 30 mg of 4,4',4”,4”'-([9,9'-bicarbazol]-3,3',6,6'-tetramethyl)tetrabenzaldehyde, an organic ligand containing an aldehyde-terminal group, were added to a glass tube. 2 mL of n-butanol and o-dichlorobenzene (volume ratio 1:1) were then added. The glass tube was immersed in an ultrasonic bath at 25°C for 15 min to ensure uniform dispersion of the organic ligands in the n-butanol / o-dichlorobenzene organic solvent system. Then, 0.2 mL of a 6 mol·L⁻¹ solution was added. -1 The mixture was stirred with acetic acid solution, the glass bottle was removed and placed in liquid nitrogen at 77K for rapid freezing and degassing, and then brought back to room temperature. This process was repeated three times to fully remove oxygen and avoid the oxygen in the glass bottle affecting the preparation of the covalent organic framework material during the reaction. The glass bottle was then quickly sealed, and after the freezing cycle was completed and the temperature was brought back to room temperature, the glass tube was placed in a forced-air drying oven and kept at a constant temperature of 120℃ for 72 hours. A solid product was generated at the bottom of the glass tube. The solid was separated by vacuum filtration and filtered alternately with methanol, acetone and ethane until the filtrate was colorless and dried to obtain the covalent organic framework material, denoted as Cz-CHO-COF.

[0066] The structure of the covalent organic framework material Cz-CHO-COF prepared in Example 1 is as follows: Figure 1 As shown.

[0067] Example 2

[0068] A covalent organic framework material includes an organic ligand 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine containing an amino-terminal group and an organic ligand terephthalaldehyde containing an aldehyde-terminal group, wherein 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and terephthalaldehyde are covalently linked.

[0069] A method for preparing a covalent organic framework material includes the following steps:

[0070] 22 mg of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, an organic ligand containing an amino-terminal group, and 12 mg of terephthalaldehyde, an organic ligand containing an aldehyde-terminal group, were added to a glass tube. 1 mL of a 1:1 volume ratio of n-butanol / o-dichlorobenzene was then added. The glass tube was immersed in an ultrasonic bath at 25°C for 15 min to ensure uniform dispersion of the organic ligands in the n-butanol / o-dichlorobenzene organic solvent system. Then, 0.1 mL of a 6 mol·L⁻¹ solution was added. -1 The acetic acid solution was removed from the glass bottle and rapidly frozen and degassed in liquid nitrogen at 77K. This process was repeated three times to avoid the oxygen in the bottle affecting the catalyst preparation during the reaction. The glass bottle was then quickly sealed. After the freezing cycle was completed and the temperature was restored to room temperature, the glass tube was placed in a forced-air drying oven and kept at a constant temperature of 120℃ for 72 hours. After the reaction, a solid product was generated at the bottom of the glass tube. The solid was separated by vacuum filtration and filtered alternately with methanol, acetone, and n-hexane until the filtrate was colorless. After drying, the covalent organic framework material, denoted as H-COF, was obtained.

[0071] The structure of the covalent organic framework material H-COF prepared in Example 2 is as follows: Figure 2 As shown.

[0072] Example 3

[0073] A covalent organic framework material includes an organic ligand tris(4-aminophenyl)amine containing an amino-terminated group and an organic ligand benzo[C][1,2,5]thiadiazole-4,7-dicarboxaldehyde containing an aldehyde-terminated group, wherein the tris(4-aminophenyl)amine and benzo[C][1,2,5]thiadiazole-4,7-dicarboxaldehyde are covalently linked.

[0074] A method for preparing a covalent organic framework material includes the following steps:

[0075] 20 mg of tris(4-aminophenyl)amine, an organic ligand containing an amino-terminal group, and 16 mg of benzo[C][1,2,5]thiadiazole-4,7-dicarboxaldehyde, an organic ligand containing an aldehyde-terminal group, were added to a glass tube. 1 mL of a 1:1 mixture of n-butanol and o-dichlorobenzene was then added. The glass tube was immersed in an ultrasonic bath at 25°C for 15 min to ensure thorough and uniform dispersion of the organic ligands in the n-butanol / o-dichlorobenzene organic solvent system. Finally, 0.1 mL of a 6 mol·L⁻¹ solution was added. -1The acetic acid solution was removed from the glass bottle and rapidly frozen and degassed in liquid nitrogen at 77K. This process was repeated three times to avoid the oxygen in the bottle affecting the catalyst preparation during the reaction. The glass bottle was then quickly sealed. After the freezing cycle was completed and the temperature was restored to room temperature, the glass tube was placed in a forced-air drying oven and kept at a constant temperature of 120℃ for 72 hours. After the reaction, a solid product was generated at the bottom of the glass tube. The solid was separated by suction filtration and filtered alternately with dimethylformamide and acetone until the filtrate was colorless. After drying, the covalent organic framework material was obtained, denoted as NO-COF.

[0076] The structure of the covalent organic framework material NO-COF prepared in Example 3 is as follows: Figure 3 As shown.

[0077] Performance testing

[0078] 1. Transmission electron microscopy test

[0079] The covalent organic framework material Cz-CHO-COF prepared in Example 1 was subjected to transmission electron microscopy (TEM) testing. The TEM image is shown below. Figure 4 As shown.

[0080] Depend on Figure 4 The TEM images show that the material has a nanocluster morphology.

[0081] 2. X-ray diffraction analysis

[0082] X-ray diffraction analysis was performed on the covalent organic framework material Cz-CHO-COF prepared in Example 1, and the results are as follows: Figure 5 As shown, the horizontal axis 2Theta (degree) represents the diffraction angle 2θ (°), the vertical axis Intensity (au) represents the diffraction intensity, Experimental represents the experimental data obtained from XRD tests, Pawley refined represents Pawley refinement, AA stacking represents AA stacking, AB stacking represents AB stacking, Difference represents the difference between the actual XRD test results and the Pawley refined results, Bragg positions represent the Bragg peak positions, Rp represents the graph variance factor, and Rwp represents the weighted graph variance factor.

[0083] Depend on Figure 5 It can be seen that the covalent organic framework material Cz-CHO-COF is an AA stack and has a good crystal structure with a stable and highly ordered arrangement.

[0084] 3. Catalytic performance testing

[0085] The photocatalytic and photocatalytic-piezoelectric synergistic effects of the covalent organic framework material Cz-CHO-COF prepared in Example 1 on the generation of hydrogen peroxide were tested.

[0086] (1) Establishment of the standard curve: The standard curve was measured using the N,N-diethyl-p-phenylenediamine colorimetric method. The specific method is as follows:

[0087] Prepare 1 L of 0.5 M disodium hydrogen phosphate solution and 1 L of 0.5 M sodium dihydrogen phosphate solution. Add the disodium hydrogen phosphate solution to the sodium dihydrogen phosphate solution until the pH of the mixed solution is 6, thus obtaining the buffer solution required for the test. Weigh 0.1 g of N,N-diethyl-p-phenylenediamine (DPD) and dissolve it in 10 mL of 0.05 M H2SO4 solution to obtain the DPD solution required for color development. Weigh 0.1 g of peroxidase (POD) and dissolve it in 10 mL of water to obtain the POD solution required for color development. Use a 30% hydrogen peroxide stock solution and dilute it to obtain hydrogen peroxide solutions with concentrations of 25 μM-200 μM (25 μM, 50 μM, 75 μM, 100 μM, 150 μM, 200 μM). Take a 10 mL colorimetric tube and add 5.9 mL of water, 3 mL of buffer solution, 1 mL of the test solution (the hydrogen peroxide solution prepared above), and 50 μL of... POD solution, 50 μL DPD solution, capped, inverted 3 times, and allowed to stand for 30 seconds. Absorption spectra were obtained at 400 nm-700 nm using a UV spectrophotometer. A standard curve was established, revealing that the absorbance reached its maximum at 551 nm, and the standard curve showed good fit. The standard curve is shown below. Figure 6 As shown, the horizontal axis H2O2 Concentration (μM) represents the hydrogen peroxide concentration, and Absorbance (au) represents the absorbance.

[0088] (2) Determination of hydrogen peroxide concentration: The concentration of hydrogen peroxide was determined by the N,N-diethyl-p-phenylenediamine colorimetric method, and the specific method is as follows:

[0089] Prepare 1 L of 0.5 M disodium hydrogen phosphate solution and 1 L of 0.5 M sodium dihydrogen phosphate solution. Add the disodium hydrogen phosphate solution to the sodium dihydrogen phosphate solution until the pH of the mixed solution reaches 6, thus obtaining the buffer solution required for the test. Weigh 0.1 g of DPD and dissolve it in 10 mL of 0.05 M sodium dihydrogen phosphate solution. In H2SO4 solution, the DPD solution required for color development was obtained; 0.1g of POD was weighed and dissolved in 10mL of water to obtain the POD solution required for color development; a 10mL colorimetric tube was taken, and 5.9mL of water, 3mL of buffer solution, 1mL of test solution (2mg of Cz-CHO-COF prepared in Example 1 was weighed into a reaction glass bottle, 20mL of deionized water was added, and the mixture was sonicated for 3min to fully disperse the Cz-CHO-COF catalyst in the water; pure oxygen was aerated in the water for 20min, the cap was quickly tightened and sealed, and the reaction was carried out to obtain a reaction suspension; reaction suspensions at different reaction times (0min, 15min, 30min, 45min, 60min) were taken, and the reaction suspensions were filtered through a 0.22μM PES syringe filter to obtain the test solution), 50μL of POD solution, and 50μL of POD solution were added. The DPD solution was capped, inverted three times, and allowed to stand for 30 seconds. The absorbance was then measured at 551 nm using a UV spectrophotometer, and the hydrogen peroxide concentration was calculated using the standard curve described above.

[0090] (3) Photocatalytic production of hydrogen peroxide: Weigh 2 mg of Cz-CHO-COF prepared in Example 1 into a reaction glass bottle, add 20 mL of deionized water, and sonicate for 3 min to fully disperse the Cz-CHO-COF catalyst in the water; aerate the water with pure oxygen for 20 min, and quickly tighten the cap to seal, thus obtaining a reaction suspension; irradiate the reaction suspension with a 300 W xenon lamp light source with λ>420 nm, and take the solutions at 0 min, 15 min, 30 min, 45 min, and 60 min of reaction, and determine the hydrogen peroxide concentration using the N,N-diethyl-p-phenylenediamine colorimetric method, and determine the corresponding absorbance at each concentration using ultraviolet-visible spectrophotometry, and calculate the concentration of hydrogen peroxide produced by the standard curve.

[0091] (4) Photocatalytic-piezoelectric synergistic production of hydrogen peroxide: Weigh 2 mg of Cz-CHO-COF prepared in Example 1 into a reaction glass bottle, add 20 mL of deionized water, and sonicate for 3 min to fully disperse the catalyst in the water; aerate the water with pure oxygen for 20 min, and quickly tighten the cap to seal, to obtain a reaction suspension; use a 300 W xenon lamp source with λ>420 nm and a 40 KHz ultrasonic machine (80 W) to irradiate / sonicate the reaction suspension, take the solution at 0 min, 15 min, 30 min, 45 min and 60 min of reaction, determine the hydrogen peroxide concentration by N,N-diethyl-p-phenylenediamine colorimetric method, and use ultraviolet-visible spectrophotometry to determine the corresponding absorbance at each concentration, and calculate the concentration of hydrogen peroxide produced by standard curve.

[0092] The efficiency graphs of photocatalysis and photocatalysis-piezoelectric synergistic hydrogen peroxide production of the covalent organic framework material Cz-CHO-COF prepared in Example 1 are shown below. Figure 7 As shown, the horizontal axis Time (min) represents time (minutes), the vertical axis H2O2Production (μM) represents hydrogen peroxide yield, Cz-CHO-COF Photo represents the hydrogen peroxide production efficiency of Cz-CHO-COF under photocatalytic conditions, and Cz-CHO-COF Pizeo-Photo represents the hydrogen peroxide production efficiency of Cz-CHO-COF under photocatalytic-piezoelectric conditions.

[0093] Depend on Figure 7 It is known that the hydrogen peroxide yield of the covalent organic framework material Cz-CHO-COF under photocatalytic conditions is 2638 μmol g. -1 h -1 The hydrogen peroxide yield under photocatalysis-piezoelectric synergistic conditions was 3670 μmol g. -1 h -1 It exhibits good efficiency in producing hydrogen peroxide, and under the synergistic effect of photocatalysis and piezoelectricity, the efficiency of this photocatalytic material in producing hydrogen peroxide is higher than that under photocatalytic conditions.

[0094] In summary, this invention, through the construction of specific types of electron donor-electron acceptor structures, enables the redox centers in covalent organic framework materials to be spatially separated. This facilitates the rapid separation and migration of photogenerated supports and improves their lifetime, thereby enabling highly efficient photocatalytic-piezoelectric synergistic catalytic reactions to produce H2O2. This significantly increases the yield of hydrogen peroxide, and under the synergistic effect of photocatalysis and piezoelectricity, the efficiency of hydrogen peroxide production by this material is higher than that under photocatalytic conditions.

[0095] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. The application of a covalent organic framework material in the photocatalytic-piezoelectric synergistic preparation of hydrogen peroxide, characterized in that, The covalent organic framework material includes an electron donor and an electron acceptor; the electron donor and the electron acceptor are connected by covalent bonds; The electron donor includes an organic ligand containing an aldehyde-terminated group; The electron acceptor includes an organic ligand containing an amino-terminal group; The organic ligand containing the aldehyde terminal group is 4,4',4'',4'''-([9,9'-bicarbazol]-3,3',6,6'-tetramethyl)tetrabenzaldehyde; The organic ligand containing an amino-terminal group is p-phenylenediamine; The structural formula of the covalent organic framework material is: ； The method for preparing the covalent organic framework material includes the following steps: The covalent organic framework material is prepared by mixing an organic ligand containing an amino-terminal group, an organic ligand containing an aldehyde-terminal group, an organic solvent, and a catalyst, and reacting the mixture. The organic solvent is selected from at least one of methanol, toluene, n-hexane, n-butanol, o-dichlorobenzene, and acetone; The catalyst is acetic acid.

2. The application according to claim 1, characterized in that, The mass ratio of the organic ligand containing an amino-terminal group to the organic ligand containing an aldehyde-terminal group is (0.9-2.2):(0.9-2.8).

3. The application according to claim 1, characterized in that, The mixing process also includes a freeze-degassing process; after freeze-degassing, the mixture is restored to room temperature before the reaction is carried out.

4. The application according to claim 1, characterized in that, The reaction temperature is 110-130℃, and the reaction time is 60-80h.

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