Triazine-based cofs, preparation method thereof and application of hydrogen peroxide production

Abstract

The application discloses a triazine-based COF, which is prepared from 4,4',4"-(1,3,5-triazine-2,4,6-triyl) triphenylamine and 2,5-dihydroxy-1,4-benzene dicarboxaldehyde as building units, and the triazine-based COF is in a coral shape. The application further discloses a preparation method of the triazine-based COF, which comprises the following steps: uniformly mixing 4,4',4"-(1,3,5-triazine-2,4,6-triyl) triphenylamine, 2,5-dihydroxy-1,4-benzene dicarboxaldehyde, N-methyl pyrrolidone and a catalyst, and performing reaction to obtain the triazine-based COF. The application further discloses application of the triazine-based COF and the triazine-based COF prepared by the method in photocatalytic production of hydrogen peroxide. The application further discloses a method for producing hydrogen peroxide by using water. The triazine-based COF can greatly improve the photocatalytic H2O2 production efficiency.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, and in particular to a triazine-based COFs, its preparation method, and its application in producing hydrogen peroxide. Background Technology

[0002] Photocatalysis, as a highly efficient, safe, and environmentally friendly purification technology, generally relies on the redox capabilities of photocatalysts under sunlight to purify pollutants, synthesize substances, and transform them. For example, hydrogen peroxide (H2O2) is one of the world's 100 most important chemicals, widely used in chemical production, environmental protection, energy storage, and as a microbial disinfectant. H2O2 is a clean energy source with an energy density comparable to compressed hydrogen, and it is easier to store and transport. The anthraquinone process is the most commonly used industrial method for preparing H2O2, but this method typically uses metal catalysts such as palladium, resulting in high energy consumption and significant waste. Therefore, using photocatalytic materials to generate H2O2 through the photocatalytic reaction of water and O2 under sunlight is a clean and safe preparation method with great potential compared to other H2O2 preparation methods.

[0003] Currently, most reported photocatalytic materials are based on metal oxides and metal-organic frameworks, which easily cause significant environmental pollution, limiting their widespread application in real-world water treatment systems. Furthermore, most reported photocatalysts require sacrificial agents to quench electrons or holes and improve charge separation efficiency. Introducing other substances into the reaction system generates byproducts along with H2O2. Due to the presence of water-soluble sacrificial agents and their oxidation products, the separation and purification required to obtain a pure H2O2 solution is costly and cumbersome. Therefore, photocatalytic production of H2O2 without the use of sacrificial agents is crucial. To address these issues, a rationally designed photocatalytic material is urgently needed to solve the challenge of producing H2O2 from pure water. Covalent organic frameworks (COFs) are porous organic materials linked by covalent bonds, possessing highly tunable structures, broadened light absorption, and a wide range of active sites, making them widely applicable in the field of photocatalysis.

[0004] However, to date, most existing COF photocatalytic materials rely on sacrificial agents to improve photocatalytic performance, which leads to the generation of byproducts and increases the cost of H2O2 extraction. Furthermore, COF materials exhibit poor electron-hole separation capabilities in pure water, severely limiting their photocatalytic performance. Additionally, some COF materials show low H2O2 production yields without the use of sacrificial agents. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, this invention proposes a triazine-based COFs and its preparation method, as well as its application in hydrogen peroxide production. This invention introduces triazine-based COFs with a coral-like structure, which can significantly improve the efficiency of photocatalytic H2O2 production.

[0006] This invention proposes a triazine-based COFs, wherein the triazine-based COFs are constructed using 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde as building blocks, and the triazine-based COFs are coral-like.

[0007] Preferably, the specific surface area of ​​the triazine-based COFs is 2800-3000 m². 2 / g.

[0008] The present invention also proposes a method for preparing the above-mentioned triazine-based COFs, comprising the following steps: mixing 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, N-methylpyrrolidone and a catalyst, and reacting to obtain triazine-based COFs.

[0009] Preferably, the catalyst is acetic acid.

[0010] Preferably, the molar ratio of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde is 1:0.8-1.2.

[0011] Preferably, the ratio of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine to N-methylpyrrolidone is 1 mol: 4.5-5.5 L.

[0012] Preferably, the volume ratio of N-methylpyrrolidone to catalyst is 9-11:1.

[0013] Preferably, the reaction temperature is 150-170℃ and the reaction time is 60-84h.

[0014] Preferably, the reaction is carried out in an inert gas atmosphere.

[0015] The inert gas mentioned above can be argon, etc.

[0016] Preferably, after the reaction is complete, the product is purified to obtain triazine-based COFs.

[0017] Preferably, the purification step includes: after the reaction is complete, collecting the solid, washing the solid with ethanol, drying it, and obtaining triazine COFs.

[0018] Preferably, the solid is washed with ethanol at 70-90°C.

[0019] This invention also proposes the application of the above-mentioned triazine-based COFs, and the triazine-based COFs prepared by the above method, in the photocatalytic production of hydrogen peroxide.

[0020] The present invention also proposes a method for producing hydrogen peroxide using water, comprising the following steps: mixing a photocatalyst with water, introducing oxygen, and irradiating with light to obtain hydrogen peroxide, wherein the photocatalyst is the above-mentioned triazine-based COFs or triazine-based COFs prepared by the above method.

[0021] Preferably, a xenon lamp is used for illumination.

[0022] The water mentioned above can be deionized water, purified water, etc.

[0023] This invention selects 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde as building blocks, and uses appropriate organic solvents and preparation methods to finally obtain coral-like triazine-based COFs. These COFs have high crystallinity and high specific surface area. Their specific structure can provide a large number of active sites to participate in the photocatalytic H2O2 production reaction in aquaculture. They do not require additional sacrificial agents to consume photogenerated carriers, thus improving their photogenerated electron-hole pair separation ability. This solves the problems of existing COF photocatalytic materials, which mostly rely on sacrificial agents to generate byproducts, and suffer from severe recombination and low utilization of photogenerated carriers.

[0024] Compared with COFs materials using 1,3,5-tris(4-aminophenyl)benzene as the building block, the present invention introduces triazine groups into COFs materials, which further enhances the separation ability of photogenerated electrons and holes during the reaction process and improves its photocatalytic efficiency; compared with phenyl, the photocatalytic H2O2 production activity of the coral-like triazine COFs of the present invention is increased by about 3 times.

[0025] This invention employs a one-pot, one-step polymerization method to obtain coral-like triazine-based COFs. The preparation method is simple and has universal applicability to COFs materials. Attached Figure Description

[0026] Figure 1-3 The images shown are, in order, scanning electron microscope (a) and transmission electron microscope (b) spectra of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0027] Figure 4 The X-ray diffraction patterns of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown below. NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0028] Figure 5The image shows the infrared spectrum of the triazine-based COFs prepared in Example 1, wherein NMP-COF is from Example 1, Tapt is 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, and DHTA is 2,5-dihydroxy-1,4-benzyl dicarboxaldehyde.

[0029] Figure 6 The image shows the carbon NMR spectrum of the triazine-based COFs prepared in Example 1.

[0030] Figure 7 The X-ray photoelectron spectroscopy (XPS) of the triazine-based COFs prepared in Example 1 is shown, where a is the full spectrum, b is the C1s spectrum, c is the N1s spectrum, and d is the O1s spectrum.

[0031] Figure 8 The H2O2 production of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 under visible light irradiation for 2 hours is shown. Among them, NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0032] Figure 9 The graphs (a) and (b) show the performance of the triazine-based COFs prepared in Example 1 in producing H2O2 under visible light irradiation for a long time.

[0033] Figure 10 The water contact angle test results are for COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2, where NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0034] Figure 11 The photoluminescence spectra of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown. NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2. Detailed Implementation

[0035] The technical solution of the present invention will now be described in detail through specific embodiments.

[0036] Example 1

[0037] A method for preparing triazine-based COFs includes the following steps:

[0038] Weigh 0.354 g (1 mmol) of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 0.166 g (1 mmol) of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, place them in a three-necked flask, add 5 mL of N-methylpyrrolidone and 0.5 mL of acetic acid in sequence, stir for 5 min and sonicate for 10 min; then heat in an oil bath at 160 °C for 72 h under argon atmosphere and reflux for 72 h, filter to obtain a red solid, wash the red solid repeatedly with ethanol until the washing solution is colorless and transparent (each washing step is: heat in a water bath at 80 °C and stir for 10 min), then dry to obtain triazine COFs, denoted as NMP-COF.

[0039] Example 2

[0040] A method for preparing triazine-based COFs includes the following steps:

[0041] Weigh 0.354 g (1 mmol) of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 0.133 g (0.8 mmol) of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde into a three-necked flask, add 4.5 mL of N-methylpyrrolidone and 0.5 mL of acetic acid, stir for 5 min, and sonicate for 10 min. Then, under an argon atmosphere, heat in an oil bath at 150 °C and reflux for 84 h. Filter to obtain a red solid. Wash the red solid repeatedly with ethanol until the washing solution is colorless and transparent (each washing step is: heat in a water bath at 70 °C and stir for 10 min). Then dry to obtain triazine COFs.

[0042] Example 3

[0043] A method for preparing triazine-based COFs includes the following steps:

[0044] Weigh 0.354 g (1 mmol) of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 0.199 g (1.2 mmol) of 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, place them in a three-necked flask, add 5.5 mL of N-methylpyrrolidone and 0.5 mL of acetic acid in sequence, stir for 5 min and sonicate for 10 min; then heat in an oil bath at 170 °C for 60 h under argon atmosphere and reflux for 60 h, filter to obtain a red solid, wash the red solid repeatedly with ethanol until the washing liquid is colorless and transparent (each washing step is: heat in a water bath at 90 °C and stir for 10 min), and then dry to obtain triazine COFs.

[0045] Comparative Example 1

[0046] A method for preparing triazine-based COFs includes the following steps:

[0047] Replace “N-methylpyrrolidone” with “o-dichlorobenzene”, otherwise the same as in Example 1, denoted as o-DCB-COF.

[0048] Comparative Example 2

[0049] A method for preparing phenyl COFs includes the following steps:

[0050] Replace “1 mmol of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine” with “1 mmol of 1,3,5-tris(4-aminophenyl)benzene” and “N-methylpyrrolidone” with “o-dichlorobenzene”, otherwise the same as in Example 1, denoted as Tapb-COF.

[0051] The COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested, and the results are as follows: Figure 1-11 As shown.

[0052] Figure 1-3 The images shown are, in order, scanning electron microscope (a) and transmission electron microscope (b) spectra of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0053] Depend on Figure 1-3 It can be seen that the triazine COFs prepared in Example 1 are arranged in a coral-like aggregate, while the triazine COFs prepared in Comparative Example 1 are arranged in a granular aggregate, and the phenyl COFs prepared in Comparative Example 2 are composed of spherical aggregates of varying sizes. The specific surface area of ​​the triazine COFs prepared in Example 1 was measured to be 2960.6 m². 2 / g, the parent nucleus of triazine COFs (parent nucleus structure as follows) Figure 6 The macrocyclic pore size formed (as shown in the structural formula) is 2.37 nm; different building blocks and organic solvents will result in different microstructures of the final product, thus affecting its photocatalytic performance.

[0054] Figure 4 The X-ray diffraction patterns of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown below. NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0055] Depend on Figure 4 It can be seen that the triazine COFs prepared in Example 1 have higher crystallinity than the COFs prepared in Comparative Examples 1 and 2.

[0056] Figure 5The image shows the infrared spectrum of the triazine-based COFs prepared in Example 1, wherein NMP-COF is from Example 1, Tapt is 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine, and DHTA is 2,5-dihydroxy-1,4-benzyl dicarboxaldehyde.

[0057] Figure 6 The image shows the carbon NMR spectrum of the triazine-based COFs prepared in Example 1.

[0058] Figure 7 The X-ray photoelectron spectroscopy (XPS) of the triazine-based COFs prepared in Example 1 is shown, where a is the full spectrum, b is the C1s spectrum, c is the N1s spectrum, and d is the O1s spectrum.

[0059] Depend on Figure 5-7 It can be seen that the formation of the imine bond (C=N) proves that the triazine COFs were successfully prepared in Example 1.

[0060] The COFs obtained in Example 1, Comparative Example 1, and Comparative Example 2 were used as photocatalysts for the production of H2O2. The specific steps included: placing 0.002g of photocatalyst in a reaction flask, adding 30mL of deionized water and stirring to mix, purging with oxygen for 20min, and then irradiating with a 300W xenon lamp. Every 30min, 1mL of the reaction solution was taken to detect the concentration of H2O2.

[0061] The method for detecting H2O2 is as follows: Filter 1 mL of the reaction solution and add it to 2 mL of the detection solution (the detection solution consists of equal volumes of 0.4 mol / L potassium iodide aqueous solution and 0.1 mol / L potassium hydrogen phthalate aqueous solution). Shake well and allow the color to develop. Measure the absorbance of the liquid using a UV-Vis spectrophotometer, and calculate the H2O2 concentration based on the absorbance. The results are as follows: Figure 8 As shown.

[0062] Figure 8 The H2O2 production of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 under visible light irradiation for 2 hours is shown. Among them, NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0063] Depend on Figure 8 It can be seen that the photocatalytic H2O2 production performance of the triazine-based COFs prepared in Example 1 is much higher than that of Comparative Examples 1-2.

[0064] Figure 9 The graphs (a) and (b) show the performance of the triazine-based COFs prepared in Example 1 in producing H2O2 under visible light irradiation for a long time.

[0065] Depend on Figure 9It can be seen that the triazine-based COFs prepared in Example 1 have stable catalytic activity within 6 hours and good cycle stability.

[0066] Figure 10 The water contact angle test results are for COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2, where NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0067] Depend on Figure 10 It can be seen that the COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 all have superhydrophilicity and can be well dispersed in water.

[0068] Figure 11 The photoluminescence spectra of COFs prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown. NMP-COF is Example 1, o-DCB-COF is Comparative Example 1, and Tapb-COF is Comparative Example 2.

[0069] Depend on Figure 11 It can be seen that the triazine-based COFs prepared in Example 1 have stronger photogenerated carrier migration and separation capabilities, and more photogenerated charges participate in the reaction, thereby improving the photocatalytic H2O2 production performance.

[0070] In summary, the triazine-based structure introduced in this invention promotes the separation of photogenerated carriers and improves the efficiency of photocatalytic H2O2 production. Furthermore, this invention uses suitable organic solvents and preparation methods to obtain coral-like triazine-based COFs, which have high crystallinity, large specific surface area, and a specific microstructure that provides a large number of active sites to participate in the photocatalytic H2O2 production reaction, thereby significantly improving the efficiency of photocatalytic H2O2 production. The coral-like triazine-based COFs described in this invention have broad market application prospects.

[0071] The method described in this invention provides a stable synthetic method for regulating the structure of COFs. By introducing or replacing electron-withdrawing or electron-donating groups, the electron movement in the COFs structure can be adjusted, achieving efficient migration and separation of charge carriers. This solves the problem that most existing COFs photocatalytic materials require the use of sacrificial agents and have low efficiency in the migration and separation of photogenerated charge carriers.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing triazine-based COFs, characterized in that, The process includes the following steps: mixing 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,5-dihydroxy-1,4-benzenedicarboxaldehyde, N-methylpyrrolidone and a catalyst, and reacting them to obtain triazine-based COFs.

2. The method for preparing triazine-based COFs according to claim 1, characterized in that, The specific surface area of ​​the triazine-based COFs is 2800-3000 m². 2 / g.

3. The method for preparing triazine-based COFs according to claim 1, characterized in that, The catalyst is acetic acid.

4. The method for preparing triazine-based COFs according to claim 1, characterized in that, The molar ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine to 2,5-dihydroxy-1,4-benzenedicarboxaldehyde is 1:0.8-1.

2.

5. The method for preparing triazine-based COFs according to claim 1, characterized in that, The ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine to N-methylpyrrolidone is 1 mol: 4.5-5.5 L.

6. The method for preparing triazine-based COFs according to claim 1, characterized in that, The volume ratio of N-methylpyrrolidone to catalyst is 9-11:

1.

7. The method for preparing triazine-based COFs according to claim 1, characterized in that, The reaction temperature is 150-170℃, and the reaction time is 60-84 h.

8. The method for preparing triazine-based COFs according to claim 1, characterized in that, The reaction takes place in an inert gas atmosphere.

9. The method for preparing triazine-based COFs according to claim 1, characterized in that, After the reaction was completed, the product was purified to obtain triazine COFs.

10. The method for preparing triazine-based COFs according to claim 9, characterized in that, The purification steps include: after the reaction is complete, the solid is collected, washed with ethanol, and dried to obtain triazine COFs.

11. The method for preparing triazine-based COFs according to claim 10, characterized in that, The solid was washed with ethanol at 70-90°C.

12. The application of a triazine-based COFs prepared by the method according to any one of claims 1-11 in the photocatalytic production of hydrogen peroxide.

13. A method for producing hydrogen peroxide using water, characterized in that, The process includes the following steps: mixing the photocatalyst with water, introducing oxygen, and irradiating with light to obtain hydrogen peroxide, wherein the photocatalyst is a triazine-based COFs prepared by the method described in any one of claims 1-11.

14. The method for producing hydrogen peroxide using water according to claim 13, characterized in that, Illumination is achieved using xenon lamps.

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