A-D-A type COF photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses an A-D-A type COF photocatalyst as well as a preparation method and application thereof, and the COF photocatalyst is constructed by taking 4 ', 4' ', 4' ''-(1, 3, 5-triazinyl-2, 4, 6-triyl) tri (([1, 1 '-biphenyl]-4-amine)) (TB) and 2, 7-dibenzaldehyde-benzothiadiazole (BTDA) as units; the preparation method comprises the following steps: (1) adding TB and BTDA into an organic solvent, and uniformly mixing; (2) continuously adding an acid catalyst, uniformly mixing, and removing air; and (3) carrying out an aldehyde-amine condensation reaction on the air-removed mixture in the step (2) to obtain a yellow precipitate, washing, and drying to obtain the photocatalyst. According to the invention, a novel acceptor-donor-acceptor (A-D-A) COF is synthesized from TB and BTDA, and the COF has an excellent catalytic effect on photocatalytic synthesis of H2O2.

Description

Technical Field

[0001] The present invention relates to a catalyst, and particularly to an A-D-A type COF photocatalyst and its preparation method and application. Background Art

[0002] Hydrogen peroxide (H2O2) is regarded as a sustainable fuel and oxidant, which has attracted increasing attention in the energy and environmental fields. It is widely used in pulp and textile bleaching, emergency disinfection, advanced oxidation processes (AOPs) in wastewater treatment, as well as food preservation and the electronics industry. H2O2 not only has great potential as an environmentally friendly environmental remediation oxidant, but also as a liquid fuel alternative to H2 and O2 in fuel cells. Currently, the global annual production of hydrogen peroxide is approximately 2.2 million metric tons. Its two main production methods include industrial and laboratory methods. Industrial techniques include the anthraquinone and electrolysis methods, while laboratory methods usually require manganese dioxide catalysis. In the anthraquinone method, hydrogen gas passes through an anthraquinone solution, reducing it to anthraquinone hydroxide, and then undergoes an oxidation-reduction cycle reaction to produce hydrogen peroxide. However, the anthraquinone method is prone to pollution, involves complex production processes, requires the addition of Ni or Pd catalysts, and generates a large amount of organic waste. In contrast, the electrolysis method involves the direct reaction of H2 and O2 through electrolysis in an acidic medium to produce H2O2. Similarly, the electrolysis method also has some disadvantages, such as high energy consumption, equipment maintenance challenges, and the need to precisely control the ratio of hydrogen and oxygen to reduce the explosion risk. In addition, hydrogen peroxide is prone to decomposition, posing storage and transportation hazards, and strict safety measures need to be taken. Therefore, efforts are being made to develop new H2O2 production methods that operate under milder reaction conditions and minimize waste generation.

[0003] COFs are infinite 2D or 3D structures composed of organic molecules covalently bonded by light elements such as C, N, O, and S. It has a specific structure and predictable pores, which makes it have potential application prospects in catalysis, separation, and energy storage. COFs are usually formed by the covalent bonding of organic monomers, and their structure and pore size can be controlled by selecting different lengths and numbers of organic monomer branches, making COFs highly controllable in structure. In addition, some COFs have photosensitivity, which means they can undergo structural changes under light irradiation, thereby regulating their catalytic performance, making COFs have advantages in photocatalysis and can drive the synthesis of H2O2 under light without sacrificial reagents. In addition, COFs have many pores and a highly ordered structure, giving them a larger specific surface area. This is important for photocatalysis because a larger surface area helps to improve the efficiency of light absorption and catalytic reactions. Therefore, COFs are considered a promising photocatalyst, especially redox molecular-junction covalent organic frameworks, which can effectively promote the separation and transfer of photo-generated charges and improve the photocatalytic efficiency by introducing active sites with different redox potentials.

[0004] Currently, researchers have developed various COF-based photocatalysts for H2O2 synthesis, mainly including the following categories: (1) Donor-acceptor (D-A) type COF: By constructing electron donor (D) and electron acceptor (A) units, it promotes the separation of photo-generated charges and improves the catalytic activity. (2) Metal-modified COF: By introducing metals (such as Pt, Co) as co-catalysts, it enhances the carrier separation efficiency. However, the metal cost is high and it is prone to inactivation. (3) Porous structure-regulated COF: By optimizing the pore structure, it promotes the diffusion of reactants. Although COF materials show potential in photocatalytic H2O2 synthesis, the catalytic yield still needs to be improved. Summary of the Invention

[0005] Object of the Invention: The first object of the present invention is to provide an A-D-A type COF photocatalyst for improving the yield of photocatalytic synthesis of H2O2; the second object of the present invention is to provide a preparation method of the A-D-A type COF photocatalyst; the third object of the present invention is to provide the application of the A-D-A type COF photocatalyst in photocatalytic preparation of H2O2.

[0006] Technical Solution: The A-D-A type COF photocatalyst of the present invention is constructed from 4',4″′,4″″′-(1,3,5-triazine ring-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) (TB) and 2,7-dibenzaldehyde-benzothiadiazole (BTDA) as units.

[0007] The COF photocatalyst presents a flower cluster shape.

[0008] The structural formula of 4',4″′,4″″′-(1,3,5-triazine ring-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) (TB) is as follows:

[0009]

[0010] The structural formula of 2,7-dibenzaldehyde-benzothiadiazole (BTDA) is as follows:

[0011]

[0012] Preferably, the molar ratio of 4',4″′,4″″′-(1,3,5-triazine ring-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) to 2,7-dibenzaldehyde-benzothiadiazole is 2:2.6 - 3.4.

[0013] The preparation method of the A-D-A type COF photocatalyst of the present invention includes the following steps:

[0014] (1) Mix 4',4″′,4″″′-(1,3,5-triazine-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) and 2,7-dibenzaldehyde-benzothiadiazole evenly in an organic solvent;

[0015] (2) Continuously add an acid catalyst, mix evenly, and then remove air;

[0016] (3) Carry out an aldehyde-amine condensation reaction on the mixture after removing air in step (2) to obtain a yellow precipitate, wash it, and dry it to obtain the A-D-A type COF photocatalyst.

[0017] Preferably, in step (1), the organic solvent is a mixture of 1,3,5-trimethylbenzene and 1,4-dioxane.

[0018] Preferably, in step (2), the temperature of the aldehyde-amine condensation reaction is 120 - 130 °C, and the reaction time is 72 - 96 h.

[0019] Preferably, in step (2), the acid catalyst is an aqueous acetic acid solution. More preferably, the concentration of the aqueous acetic acid solution is 3 - 6 mol / L.

[0020] Preferably, in step (2), removing air is: quickly freeze with a liquid nitrogen bath, and carry out degassing through three freeze-pump-thaw cycles. Further, perform ultrasonic treatment on the reaction system before degassing, such as ultrasonic treatment for 10 - 30 min.

[0021] Preferably, in step (3), the washing is carried out with tetrahydrofuran and methanol respectively.

[0022] Preferably, in step (3), the drying temperature is 120 - 130 °C.

[0023] Application of the A-D-A type COF photocatalyst described in the present invention in photocatalytic preparation of H2O2.

[0024] Mechanism of invention: In this invention, a COF material is constructed with TB and BTDA as units. By introducing the TB monomer, its electron-rich phenyl group serves as an electron donor unit, and the benzothiazole group in the BTDA monomer and the triazine group in the TB monomer serve as acceptor units, thus synthesizing a novel acceptor-donor-acceptor (A-D-A) COF. This A-D-A type COF catalyst is used for the oxidation of H2O and the reduction of O2 to generate H2O2. Compared with the traditional D-A structure, in the reaction path of H2O oxidation to generate H2O2, the rate-determining step *H2O to *OH of the A-D-A structure exhibits a lower free energy barrier; meanwhile, in the reaction path of O2 reduction to generate H2O2, the rate-determining step *O2 to *OOH of the A-D-A structure also exhibits a lower free energy barrier. The lower reaction energy barrier in the above reaction process improves the yield of catalytic generation of H2O2.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) A novel acceptor-donor-acceptor (A-D-A) COF is synthesized with TB and BTDA, which has excellent catalytic effect on the photocatalytic synthesis of H2O2; (2) The preparation method is simple and easy to industrialize; (3) This method is inexpensive and can be prepared in large quantities, the material can be recycled, and the environmental and economic benefits are high; (4) High and stable H2O2 production (1936 μmol g -1 h -1 ) is achieved by photocatalysis in water. Description of the drawings

[0026] Figure 1 is the synthesis schematic diagram of TB-BTDA-COF;

[0027] Figure 2 is the schematic overview of TB-BTDA-COF (a), TB-BT-COF (b) and TT-BTDA-COF (c). The blue and yellow blocks represent the acceptor and donor distributions respectively. The hole-electron distributions of TB-BTDA-COF (d), TB-BT-COF (e) and TT-BTDA-COF (f). The blue and green surfaces represent the hole and electron distributions respectively (isosurface = 0.0008). The electronic surface potential (ESP) of TB-BTDA-COF (g), TB-BT-COF (h) and TT-BTDA-COF (i). The red and blue surfaces represent the positive and negative electron distributions respectively;

[0028] Figure 3 are the SEM images and TEM images of the COF materials prepared in Example 1, Comparative Example 1 and Comparative Example 2;

[0029] Figures 4 - 6Experimental (red dots) and simulated (blue lines) PXRD spectra of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0030] Figure 7 UV / Vis absorption spectra of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0031] Figure 8 Tauc plots of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0032] Figure 9 Mott-Schottky plots of the COF material prepared in Example 1;

[0033] Figure 10 Mott-Schottky plots of the COF material prepared in Comparative Example 1;

[0034] Figure 11 Mott-Schottky plots of the COF material prepared in Comparative Example 2;

[0035] Figure 12 Energy band structure diagrams of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0036] Figure 13 Transient photocurrent response diagrams of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0037] Figure 14 Electrochemical impedance diagrams of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0038] Figure 15 Transient fluorescence lifetime decay curves of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0039] Figure 16 H2O2 production performance diagrams of the COF materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 in pure water and O2 atmosphere;

[0040] Figure 17 Cyclic performance diagram of photocatalytic synthesis of H2O2 by the COF material prepared in Example 1;

[0041] Figure 18 EPR spectra of the reaction solution of the COF material prepared in Example 1 under dark and visible light irradiation;

[0042] Figure 19 Photocatalytic diagrams of the COF material prepared in Example 1 under different sacrificial agent conditions. Detailed implementation manners

[0043] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0044] Example 1

[0045] The A-D-A type COF photocatalyst of the present invention is constructed with TB and BTDA as units, and its preparation method includes the following steps:

[0046] (1) Mix 5.8 mg (0.02 mmol) of TB and 5.2 mg (0.03 mmol) of BTDA with 0.75 mL of 1,3,5-trimethylbenzene and 0.25 mL of 1,4-dioxane, and add them to a 10 mL heat-resistant glass tube (size: 19×65 mm). The mixture is ultrasonically treated for 30 minutes to ensure uniform dispersion of the monomers.

[0047] (2) Subsequently, add 0.2 mL of 6 mol / L acetic acid aqueous solution to the system, continue ultrasonic treatment for 10 minutes, place the reaction tube in a liquid nitrogen bath (77 K), degas through three freeze-thaw cycles, and evacuate to an internal pressure of about 100 mTorr, then restore to room temperature.

[0048] (3) Let the mixture stand and heat at 120 °C for 72 hours. After the reaction is completed, filter through a Buchner funnel to obtain a yellow precipitate, and wash it repeatedly with THF and acetone until the filtrate is colorless. Transfer the sample to a Soxhlet extractor and wash it with tetrahydrofuran and methanol for 24 hours respectively. Finally, dry the sample under vacuum at 120 °C overnight to obtain the target product TB-BTDA-COF with a yield of 75%.

[0049] Comparative Example 1

[0050] The COF material of this comparative example is constructed with TB and 1,4-bis(4-formylphenyl)benzene (BT) as units, and the structural formula of BT is as follows:

[0051]

[0052] The preparation method includes the following steps:

[0053] (1) Mix 5.8 mg (0.02 mmol) of TB and 4.3 mg (0.03 mmol) of BT with 0.75 mL of 1,3,5-trimethylbenzene and 0.25 mL of 1,4-dioxane, and add them to a 10 mL heat-resistant glass tube (size: 19×65 mm). The mixture is ultrasonically treated for 30 minutes to ensure uniform dispersion of the monomers.

[0054] (2) Subsequently, 0.2 mL of 6 mol / L aqueous acetic acid solution was added to the system, and ultrasonic treatment was continued for 10 minutes. The reaction tube was placed in a liquid nitrogen bath (77 K), degassed by three freeze-thaw cycles, and evacuated to an internal pressure of about 100 mTorr, then restored to room temperature.

[0055] (3) The mixture was heated statically at 120 °C for 72 hours. After the reaction was completed, a yellow precipitate was obtained by filtration through a Buchner funnel and washed repeatedly with THF and acetone until the filtrate was colorless. The sample was transferred to a Soxhlet extractor and washed with tetrahydrofuran and methanol for 24 hours respectively. Finally, the sample was dried under vacuum at 120 °C overnight to obtain the target product TB-BT-COF with a yield of 75%.

[0056] Comparative Example 2

[0057] The COF material of this comparative example was constructed from 5”-(4'-amino[1,1'-biphenyl]-4-yl)[1,1':4',1”:3”,1″′:4″′,1″″-quaterphenyl]-4,4””-diamine (TT) and BTDA as units. The structural formula of TT is as follows:

[0058]

[0059] The preparation method includes the following steps:

[0060] (1) 5.8 mg (0.02 mmol) of TT and 5.2 mg (0.03 mmol) of BTDA were mixed with 0.8 mL of 1,3,5-trimethylbenzene and 0.2 mL of 1,4-dioxane, and added to a 10 mL heat-resistant glass tube (size: 19×65 mm). The mixture was ultrasonically treated for 30 minutes to ensure uniform dispersion of the monomers.

[0061] (2) Subsequently, 0.2 mL of 6 mol / L aqueous acetic acid solution was added to the system, and ultrasonic treatment was continued for 10 minutes. The reaction tube was placed in a liquid nitrogen bath (77 K), degassed by three freeze-thaw cycles, and evacuated to an internal pressure of about 100 mTorr. After restoring to room temperature,

[0062] (3) The mixture was heated statically at 120 °C for 72 hours. After the reaction was completed, a yellow precipitate was obtained by filtration through a Buchner funnel and washed repeatedly with THF and acetone until the filtrate was colorless. The sample was transferred to a Soxhlet extractor and washed with tetrahydrofuran and methanol for 24 hours respectively. Finally, the sample was dried under vacuum at 120 °C overnight to obtain the target product TT-BTDA-COF with a yield of 70%.

[0063] Structure description and characterization

[0064] Consisting of Figure 2It can be seen that TB-BTDA-COF forms an A-D-A structure, and TB-BT-COF and TT-BTDA-COF form a D-A structure.

[0065] The COF catalysts of Example 1, Comparative Example 1 and Comparative Example 2 were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD), and the results are as Figures 3 - 6 shown.

[0066] From Figure 3 the SEM and TEM images in [reference], it can be seen that Example 1 (TB-BTDA-COF) and Comparative Example 1 (TB-BT-COF) exhibit a flower cluster morphology, while Comparative Example 2 (TT-BTDA-COF) exhibits a nanorod morphology, and the lattice fringes of the three COFs can be clearly observed in the HR-TEM images, indicating a high degree of crystallinity.

[0067] From Figure 4 it can be obtained that Example 1 (TB-BTDA-COF) has a sharp and strong diffraction peak below 1.60° (2θ), corresponding to the (100) crystal plane, and its R p refinement parameter is 1.62%, and R wp is 2.17%.

[0068] From Figure 5 it can be obtained that Example 1 (TB-BT-COF) has a sharp and strong diffraction peak below 1.65° (2θ), corresponding to the (100) crystal plane, and its R p refinement parameter is 1.83%, and R wp is 2.5%.

[0069] From Figure 6 it can be obtained that Example 1 (TT-BTDA-COF) has a sharp and strong diffraction peak below 1.69° (2θ), corresponding to the (100) crystal plane, and its R p refinement parameter is 1.71%, and R wp is 2.28%.

[0070] Performance test

[0071] 1. Ultraviolet / visible absorption performance test

[0072] The COF catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were characterized by solid ultraviolet (DRS), and the results are as Figure 7 shown.

[0073] From Figure 7From the UV-vis DRS spectra, it can be seen that all samples exhibit strong absorption in the visible light region, and the TB-BTDA-COF in Example 1 shows the strongest absorption. The high UV absorption intensity indicates that TB-BTDA-COF has a broader light response range and stronger light capture ability, which directly promotes the generation of more photoexcited electron-hole pairs, thus significantly improving the efficiency of photocatalytic synthesis of H2O2.

[0074] By calculating the corresponding electronic structures, the results are as Figure 8 shown. It is determined that the optical band gaps of TB-BTDA-COF, TB-BT-COF, and TT-BTDA-COF are 2.31, 2.40, and 2.68 eV, respectively, showing semiconductor characteristics.

[0075] 2. Mott-Schottky Test

[0076] The conduction band potentials of TB-BTDA-COF, TB-BT-COF, and TT-BTDA-COF at their respective isoelectric points are inferred by Mott-Schottky (M-S) analysis, as Figures 9 - 11 shown.

[0077] From Figures 9 - 11 it can be obtained that compared with Ag / AgCl, the conduction band potentials of TB-BTDA-COF, TB-BT-COF, and TT-BTDA-COF are -0.88, -0.85, and -0.81 eV (relative to NHE, -0.68, -0.65, and -0.61 eV, respectively). This indicates that their conduction band electrons have stronger reducing ability and can more efficiently reduce O2 to ·O2 - (O2 / ·O2 - = -0.33 V vs. NHE), and then generate H2O2 (O2 / H2O2 = +0.68 V vs. NHE). Subsequently, the valence band (VB) positions of TB-BTDA-COF, TB-BT-COF, and TT-BTDA-COF are calculated to be 1.63, 1.75, and 2.07 eV (relative to NHE) ( Figure 12 ), indicating that the hole oxidation ability of TB-BTDA-COF is moderate, which can not only avoid over-oxidation to damage H2O2 (H2O2 / O2 = +1.44 V vs. NHE), but also provide sufficient driving force to oxidize H2O. The CB values of the three COFs exceed -0.33 and 0.68 eV (relative to NHE), indicating that they can directly or indirectly pass through 2e -The ORR pathway promotes the generation of H2O2. In addition, the VB potential ensures sufficient thermodynamic driving force for the oxidation of water to O2, thus promoting the redox cycle. Therefore, in theory, all three types of COFs can be effective photocatalysts for generating H2O2 from pure water, and TB-BTDA-COF has the best catalytic ability.

[0078] 3. Transient photocurrent response test

[0079] The transient photocurrent response performance of the materials of Example 1, Comparative Example 1 and Comparative Example 2 was tested by transient photocurrent response experiments, and the results are as Figure 13 shown.

[0080] It can be Figure 13 seen that the results of the transient photocurrent response experiment show that compared with TB-BT-COF and TT-BTDA-COF, TB-BTDA-COF exhibits a stronger response, indicating less electron recombination and faster photoinduced electron migration in TB-BTDA-COF, providing more active carriers for the photocatalytic reaction. This property significantly improves the photocatalytic H2O2 production performance of the material, enabling it to achieve a higher yield under the same conditions.

[0081] 4. Electrochemical impedance spectroscopy (EIS) test

[0082] The impedance of the materials of Example 1, Comparative Example 1 and Comparative Example 2 was tested by electrochemical impedance spectroscopy (EIS), and the results are as Figure 14 shown.

[0083] It can be Figure 14 seen that the electrochemical impedance spectroscopy (EIS) shows that compared with TB-BT-COF and TT-BTDA-COF, TB-BTDA-COF exhibits a relatively low charge transfer resistance ( Figure 14 ), indicating lower charge transfer resistance and faster interfacial electron transfer in TB-BTDA-COF. The lower charge transfer resistance of TB-BTDA-COF significantly improves the interfacial electron transport efficiency, which, combined with the excellent photoinduced charge separation ability, jointly drives the efficient photocatalytic H2O2 synthesis performance.

[0084] 5. Transient fluorescence lifetime test

[0085] To verify these findings, the photoluminescence (PL) spectra and transient fluorescence lifetime decay curves of the three COFs were measured, and the results are as Figure 15 shown.

[0086] It can be Figure 15It can be seen that the PL intensity of TB-BTDA-COF is significantly lower than that of TB-BT-COF and TT-BTDA-COF. The calculated fluorescence lifetime of TB-BTDA-COF is 3.65 μs, while that of TB-BT-COF is 1.41 μs and that of TT-BTDA-COF is 0.71 μs. This result indicates that TB-BTDA-COF has a lower electron-hole recombination rate and a more persistent charge separation state, which directly enhances the photocatalytic activity and H2O2 synthesis efficiency.

[0087] 6. Photocatalytic hydrogen peroxide production performance test

[0088] The photocatalytic hydrogen peroxide production performance of the COFs catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 was tested. The test method includes the following steps:

[0089] (1) Disperse 2 mg of the catalyst in 5 mL of deionized water and ultrasonically treat for 15 minutes to ensure uniform dispersion;

[0090] (2) Pass high-purity oxygen into the mixed solution for 30 minutes to remove air and saturate the solution with oxygen;

[0091] (3) Seal the reactor;

[0092] (4) Conduct a light irradiation experiment using a xenon lamp source (PLS-SXE300D, Beijing Perfectlight);

[0093] (5) Take samples every 15 minutes;

[0094] (6) After the sample is filtered through a 0.22 μm filter membrane, use an ultraviolet-visible spectrophotometer to measure the concentration of H2O2 in the solution. The results are as Figure 16 shown.

[0095] It can be Figure 16 seen that there is a linear relationship between the production of H2O2 and the irradiation time. The hydrogen peroxide production rates of Example 1, Comparative Example 1 and Comparative Example 2 are 1936 μmol g -1 h -1 , 1100 μmol g -1 h -1 , 402 μmol g -1 h -1 respectively. The catalytic efficiency of Comparative Example 1 decreased compared with that of Example 1 because BT was used to replace BTDA, lacking a strong electron-withdrawing unit (BTDA), resulting in a lower charge separation efficiency. The catalytic efficiency of Comparative Example 2 decreased compared with that of Example 1 because TT was used instead of TB, and there is no triazine structure in TT, which may limit electron delocalization.

[0096] 7. Catalyst stability test

[0097] The stability test of the COF catalyst in Example 1 was carried out, and the results are as Figure 17 shown.

[0098] It can be seen through Figure 17 that after continuous repeated cycling, the production of H2O2 only decreased slightly, indicating excellent structural stability and catalytic durability of the material. This performance is attributed to the highly stable covalent organic framework structure in Example 1 and its efficient utilization of photo-generated carriers during the reaction.

[0099] 8. Electron paramagnetic resonance (EPR) spectroscopy test

[0100] The electron paramagnetic resonance (EPR) spectrum of TB-BTDA-COF in Example 1 was measured using 5,5-dimethyl-1-pyrrolidone oxide (DMPO) as a radical spin trap agent, and the results are as Figure 18 shown.

[0101] It can be obtained from Figure 18 that no obvious radical signal was detected under dark conditions. Under light illumination conditions, the EPR spectrum showed obvious characteristic peaks in the range of 3450 - 3540 G, which confirmed that TB-BTDA-COF can effectively generate the key *OOH radical intermediate under photoexcitation, and this radical is an important active species in the reaction pathway of photocatalytic synthesis of H2O2. This result directly proves that the excellent photocatalytic activity of TB-BTDA-COF stems from its efficient photo-generated carrier separation and radical generation ability.

[0102] 9. Photocatalytic H2O2 production performance of TB-BTDA-COF under different conditions

[0103] To study the participation mechanism of O2 in the reaction, various scavengers were introduced into the reaction system for control experiments, and the test results are as Figure 19 shown.

[0104] It can be obtained from Figure 19 that after adding ethanol as a hole scavenger, the production of H2O2 increased significantly, reaching 2131 μmol g -1 h -1 . It is worth noting that after adding benzyl alcohol as a hole scavenger, a significant increase in the production of H2O2 was observed, reaching 44.42 mmol g -1 h -1 , which is about 23 times the production of hydrogen peroxide under pure oxygen atmosphere.

Claims

1. An ADA type COF photocatalyst, characterized in that: It is constructed from 4',4"',4""'-(1,3,5-triazine-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) and 2,7-dibenzaldehyde-benzothiadiazole.

2. The ADA type COF photocatalyst according to claim 1, characterized in that: The COF photocatalyst appears in a flower cluster shape.

3. The ADA type COF photocatalyst according to claim 1, characterized in that: The molar ratio of the 4',4"',4""'-(1,3,5-triazine ring-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) to 2,7-dibenzaldehyde-benzothiadiazole is 2:2.6-3.

4.

4. A method for preparing an ADA type COF photocatalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) adding 4',4"',4""'-(1,3,5-triazine-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)) and 2,7-dibenzaldehyde-benzothiadiazole into an organic solvent and mixing them evenly; (2) Continue to add acid catalyst, mix well, and remove air; (3) subjecting the mixture after air removal in step (2) to an aldehyde-amine condensation reaction to obtain a yellow precipitate, which is then washed and dried to obtain the ADA-type COF photocatalyst.

5. The method for preparing the ADA type COF photocatalyst according to claim 4, characterized in that: The temperature of the aldehyde-amine condensation reaction is 120-130°C.

6. The method for preparing the ADA type COF photocatalyst according to claim 4, characterized in that: In step (2), the acid catalyst is an aqueous solution of acetic acid.

7. The method for preparing the ADA type COF photocatalyst according to claim 4, characterized in that: In step (1), the organic solvent is a mixture of 1,3,5-trimethylbenzene and 1,4-dioxane.

8. The method for preparing the ADA type COF photocatalyst according to claim 4, characterized in that: In step (3), the washing is washing with tetrahydrofuran and methanol respectively.

9. The method for preparing the ADA type COF photocatalyst according to claim 4, characterized in that: In step (3), the drying temperature is 120-130°C.

10. Use of the ADA type COF photocatalyst according to any one of claims 1 to 3 in photocatalytic preparation of H2O2.

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