Highly crystalline connected organofunctional hydrophilic group covalent organic framework nanomesh fibers, methods of making and applications thereof

Abstract

This invention discloses a highly crystalline connector-functionalized hydrophilic covalent organic framework nanofiber, its preparation method, and its applications. The preparation method uses 1,3,5-tris(4-aminophenyl)triazine and functionalized terephthalaldehyde as monomer raw materials, ultrasonically dispersed in a mixed solvent of n-butanol and o-dichlorobenzene. Acetic acid solution is added at room temperature and pressure. The mixture is processed in a container with one cycle of vacuuming and ultrasonic dispersion, repeated five times, and finally the container is completely evacuated. The product catalyst is obtained through further thermal polymerization, washing, and drying. This method elucidates an optimized strategy for synthesizing functionalized connector hydrophilic COFs, achieving considerable yields, and is simple and easy to operate. The nanofibers synthesized by this method possess typical mesoporous structures, large specific surface areas, high hydrophilicity, and high crystallinity, exhibiting high catalytic activity. They can efficiently synthesize hydrogen peroxide under visible light and pure water conditions, thus showing broad application prospects in the field of photocatalytic hydrogen peroxide production.

Description

Technical Field

[0001] This invention belongs to the field of materials synthesis technology, specifically relating to a highly crystalline connective organ-energized hydrophilic covalent organic framework nanofiber, its preparation method, and its application. Background Technology

[0002] In today's environmental governance and renewable energy fields, photocatalysis technology has attracted much attention as a highly efficient and clean energy conversion method. Among them, the photocatalytic production of hydrogen peroxide has become a prominent research direction due to its wide application in environmental purification, energy conversion, and storage. Compared with metal-containing photocatalysts, which may release metals during application and lead to the undesirable decomposition of hydrogen peroxide, metal-free photocatalysts are increasingly attracting attention in the field of photocatalytic materials research and development because they do not cause secondary environmental pollution or adverse side reactions.

[0003] Against this backdrop, novel metal-free covalent organic frameworks (COFs), with their highly controllable structure, design flexibility, atomically precise frameworks, and excellent optical and electrical properties, provide a broad molecular-level design platform for optimizing their electronic structure and surface catalytic performance, thus exhibiting wide application potential in artificial photocatalytic reactions. However, COF materials reveal fatal flaws during use: under traditional synthesis conditions, COFs exhibit low crystallinity, structural disorder, poor structural stability, poor electron transport capabilities, and hindered exciton dissociation. Therefore, scientists have proposed many interface modulation strategies, such as constructing heterojunctions, introducing appropriate active sites, and embedding single atoms, which have proven effective in optimizing the photocatalytic performance of COFs. However, these modification strategies typically require complex and multi-step synthesis processes, consuming significant time and energy. Moreover, post-synthesis methods, due to their stringent synthesis conditions, to some extent disrupt the crystal order and crystallinity of the original covalent organic framework materials, limiting the development of π-conjugated systems and the availability of the materials.

[0004] By pre-designing the structure before synthesis and introducing functional groups with electronic polarity and π-conjugated framework modification effects, it is expected to provide an economical and simple method to synthesize a COF material with high crystallinity, high specific surface area, and high reactant capture ability. Summary of the Invention

[0005] This invention aims to address problems such as low crystallinity caused by unreasonable material synthesis conditions and post-synthesis methods, providing a highly crystalline connector-enhanced hydrophilic covalent organic framework nanofiber, its preparation method, and applications. This invention utilizes pre-designed structures, selecting terephthalaldehyde containing functional groups as the connective component of the covalent organic framework, and employing a pre-synthesis strategy to introduce electronically optimized functional units into the atomically defined chemical structure. The highly crystalline connector-enhanced hydrophilic covalent organic framework nanofiber prepared by this invention has a simple synthesis method, avoiding the destruction of the original COF structure by post-synthesis modifications; it has a large specific surface area, which is beneficial for exposing surface active sites; and its high crystallinity is beneficial for effective light capture and electron transport in the photocatalytic step.

[0006] The method proposed in this invention eliminates the need for the previously reported, stringent nitrogen-cooled cyclic degassing methods used to prepare the polymerizable mixture. Instead, it employs a novel cyclic ultrasonic vacuum method, reducing the difficulty of material synthesis. This cyclic ultrasonic vacuum method ensures thorough mixing of the reactants while removing oxidizing gases from the reaction system, avoiding oxidation during monomer polymerization and improving catalyst yield. Multiple vacuum ultrasonic cycles at room temperature allow for initial monomer condensation under mild conditions, which then strengthens the imine covalent bonds under subsequent thermal polymerization, enhancing material stability.

[0007] A modification strategy for highly crystalline connective organohydrophilic covalent organic framework nanofibers involves introducing atomic-level functional groups. This not only does not affect the pore structure of the original unsubstituted COF, but also improves the crystal order and enhances the longitudinal conjugation between layers through interlayer functional group interactions (such as hydrogen bonding) and the regulation of in-plane conjugation properties, thus opening up one-dimensional channels. Therefore, it exhibits a typical mesoporous structure and a huge specific surface area.

[0008] A highly crystalline connective organometallic hydrophilic covalent organic framework nanofiber exhibits a nanofiber morphology with a diameter of 20–40 nm and a main mesopore size of 2–2.3 nm. After functionalization modification, nanospheres and nanosheets grow on the outer surface of the fiber, demonstrating the regulatory effect of functional groups on the surface microenvironment of the COF.

[0009] The specific technical solution is as follows:

[0010] A method for preparing highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers includes the following steps:

[0011] 1) Add 1,3,5-tris(4-aminophenyl)triazine and terephthalaldehyde with different functional groups to a Schlenk tube with a polytetrafluoroethylene vacuum stopper, add mixed organic solvent A to the tube, and mix evenly by ultrasonication to obtain a precursor suspension.

[0012] 2) At room temperature and pressure, add acetic acid solution to the precursor suspension obtained in step 1), mix ultrasonically, and use the cyclic ultrasonic vacuum method to obtain the mixture to be treated B.

[0013] 3) Place the Schlenk tube containing mixture B in an oven for reaction. After the reaction is complete, cool it to room temperature and thoroughly clean it to obtain a highly crystalline connective organ-energized hydrophilic covalent organic framework nanoporous fiber material.

[0014] Furthermore, the terephthalaldehydes substituted with different functional groups in step 1) are 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, or 2,5-dibromoterephthalaldehyde.

[0015] Further, in step 1), the mixed organic solvent A is a mixture of n-butanol and o-dichlorobenzene, wherein the volume ratio of n-butanol to o-dichlorobenzene is controlled at 1:0.5 to 1.5.

[0016] Furthermore, in step 1), the molar ratio of the two monomers, 1,3,5-tris(4-aminophenyl)triazine and the functionalized terephthalaldehyde monomer, is 1:1 to 2.5.

[0017] Further, in step 1), the ratio of the volume of the mixed organic solvent A to the molar number of the two precursors is 1 ml: 0.05-0.12 mmol.

[0018] Further, in step 2), the concentration of the acetic acid solution is controlled at 4–8 mol / L, and the volume ratio of its solution to the mixed organic solvent A is controlled at 1:5–20. The specific operation of the cyclic ultrasonic vacuum method is as follows: Air is evacuated from the Schlenk tube using an electric vacuum pump and the tube is sealed. After sealing, the mixture in the tube is continued to be ultrasonically mixed uniformly. Ultrasonic oscillation is used to allow dissolved gases in the solvent to enter the gas phase layer in the tube, which are then removed during the second vacuuming operation. Each vacuuming followed by ultrasonic treatment constitutes one set of operations, repeated 3–7 times. Finally, a vacuum is applied and the tube is sealed to place the mixture in a vacuum environment.

[0019] Further, in step 3), mixture B is transferred to an oven for monomer covalent polymerization, with the reaction temperature controlled at 110–130°C and the duration controlled at 60–80 h.

[0020] Further, the thorough washing step in step 3) specifically involves: centrifuging and washing with tetrahydrofuran and methanol 2 to 4 times each, stirring in N,N-dimethylformamide for 6 to 14 hours to completely remove unreacted monomers, and finally filtering to separate the obtained product; the vacuum drying temperature is controlled at 50 to 70°C, and the duration is controlled at 10 to 14 hours.

[0021] The 1,3,5-tris(4-aminophenyl)triazine monomer of this invention is obtained by a basic organic synthesis method, the steps of which are as follows: 4-aminobenzonitrile is dispersed in chloroform, wherein the molar concentration of 4-aminobenzonitrile is controlled at 0.25-0.40 mol / L. Trifluoromethanesulfonic acid is added to the above mixture, with the volume ratio of distilled water to chloroform controlled at 1:8-12. The mixture is gently stirred in an ice-water bath for 20-40 min, and then stirred at room temperature for 20-26 hours. After the reaction is complete, distilled water is added, with the volume ratio of distilled water to chloroform controlled at 1:0.8-1.2. Finally, the mixture is neutralized with an appropriate amount of NaOH solution, with a concentration of 1.5-2 mol / L. The obtained monomer is collected by vacuum filtration and washed with deionized water.

[0022] A highly crystalline connective organ-energized hydrophilic covalent organic framework nanofiber prepared by the above method has obvious lattice fringes and its structural formula is as follows:

[0023]

[0024] X is selected from OMe, OH, or Br.

[0025] Application of a highly crystalline connective organohydrophilic covalent organic framework nanofiber in photocatalytic hydrogen peroxide production.

[0026] The present invention has the following advantages and beneficial effects in practice and use:

[0027] 1) Preparation strategy of highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers: Select pre-synthesis methods, prioritize material pre-design, effectively avoid the destruction of the intrinsic structure and crystallinity of the material by post-interface synthesis modification methods, and preserve the integrity of the morphology.

[0028] 2) The highly crystalline connective organoids are hydrophilic covalent organic framework nanofibers with highly ordered one-dimensional channels and a specific surface area on the order of thousands. The functional groups on the inner side of the channels endow them with hydrophilic properties, which is beneficial for adsorbing and capturing water and dissolved oxygen required for photocatalytic hydrogen peroxide.

[0029] 3) The synthesized highly crystalline connective organohydrophilic covalent organic framework nanofibers, after functional group modification, exhibit significantly enhanced structural stability and impact resistance, showing broad prospects in the practical application and production of hydrogen peroxide. Attached Figure Description

[0030] Figure 1 Electron micrograph of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 1;

[0031] Figure 2The structural characterization diagram of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 1 is shown.

[0032] Figure 3 Nitrogen adsorption-desorption curves, pore size distribution, and water contact angle diagrams of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 1;

[0033] Figure 4 Electron micrograph of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 3;

[0034] Figure 5 The structural characterization diagram of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 3 is shown.

[0035] Figure 6 Nitrogen adsorption-desorption, pore size distribution, and water contact angle of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 3;

[0036] Figure 7 Electron micrograph of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 5;

[0037] Figure 8 The structural characterization diagram of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 5 is shown.

[0038] Figure 9 Nitrogen adsorption-desorption, pore size distribution, and water contact angle of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Example 5;

[0039] Figure 10 Electron microscopy image of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Comparative Example 7;

[0040] Figure 11 The structural characterization diagram of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Comparative Example 7 is shown.

[0041] Figure 12 The nitrogen adsorption-desorption, pore size distribution, and water contact angle diagrams of the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofibers prepared in Comparative Example 7 are shown below. Detailed Implementation

[0042] The present invention will be further described in detail below with the aid of diagrams and specific examples, so that those skilled in the art can gain a deeper understanding of the implementation process and details of the invention. In the experiments of the present invention, reagents and raw materials, unless otherwise specified, are purchased through commercial channels and do not require further purification.

[0043] It is worth noting that the experimental steps described in the following embodiments are only used to further illustrate the features and advantages of the present invention, and not to specifically limit the scope of the claims. Furthermore, the following embodiments are only a part of all embodiments of the present invention. All other implementations obtained by those skilled in the art without inventive effort, based on the embodiments of the present invention, are protected by the present invention.

[0044] The purpose of this invention is to provide a highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofiber, which is a COF material in which various electron-withdrawing or electron-donating functional groups modify the inner wall of the pores. Unlike complex liquid nitrogen cyclic freezing operations, the raw materials to be polymerized are prepared by a simple cyclic ultrasonic vacuum method, and further thermally polymerized to obtain the monolithic COF material. No further post-synthetic modification is required, which not only simplifies the experimental procedure, reduces equipment requirements, and saves energy and resources, but also maintains the good crystallinity of the COF, which is beneficial for the pore structure and high specific surface area and pore volume. Due to its finely controlled planar and axial π-conjugated structure, the highly crystalline hydroxylated connector hydrophilic covalent organic framework nanofiber of this invention, with its expanded intramolecular polarity and interfacial hydrophilicity, can efficiently capture hydrogen ions, dissolved oxygen, and water molecules in the reaction medium, achieving the effect of highly efficient photocatalytic hydrogen peroxide production under visible light. Specific embodiments are as follows:

[0045] Example 1

[0046] In this embodiment, the specific steps for preparing highly crystalline methoxy-functionalized connector hydrophilic covalent organic framework nanofibers are as follows:

[0047] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 17.5 mg (0.09 mmol) of 2,5-dimethoxyterephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to ensure uniform dispersion.

[0048] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Evacuate the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, evacuate and seal the tube to place the mixture in a vacuum environment.

[0049] (3) The reactants obtained in step (2) were placed in an oven and subjected to thermal polymerization at 120°C for 72 h. The product was first washed three times by centrifugation with tetrahydrofuran, and then washed three times by centrifugation with methanol.

[0050] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0051] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a golden yellow methoxy functionalized connector hydrophilic covalent organic framework nanoporous fiber product, denoted as TAPT-OMe.

[0052] like Figure 1 As shown in a, scanning electron microscopy results indicate that the obtained highly crystalline connective organohydrophilic covalent organic framework nanofibers exhibit an irregular morphology with a diameter of 20–40 nm and a relatively smooth surface. Figure 1 In image b, a transmission electron microscope clearly captured significant lattice fringes corresponding to the (001) crystal plane, with a width of [missing information]. This indicates that COF maintains good crystallinity. Furthermore, Figure 2 The sharp peaks at 2.8°, 5.0°, 5.9°, 7.5°, 9.5°, and 25.9° in the X-ray diffraction pattern correspond to the (100), (110), (200), (120), (220), and (001) crystal planes of TAPT-OMe, respectively, demonstrating that COF has high structural order and crystallinity. According to... Figure 2 The Fourier transform infrared spectrum of b, at 1576 cm⁻¹ -1 The strong tensile vibration peak at C=N indicates the successful formation of the imine bond (C=N). The corresponding peak at 1680 cm⁻¹... -1 The C=O peak at 2846 cm⁻¹ is attributed to the uncondensed aldehyde group. -1 The characteristic vibrational peaks correspond to the -OCH3 group, demonstrating the successful introduction of methoxy groups into this highly crystalline connective organ's hydrophilic covalent organic framework nanofibers, achieving electronic and interfacial microenvironmental modulation. Its structural formula is as follows:

[0053]

[0054] Figure 3 The nitrogen adsorption-desorption curves in sample a show that TAPT-OMe exhibits a type IV adsorption isotherm, confirming its mesoporous structure. The specific surface area calculated using the BET method is 1351 m². 2 / g. The pore distribution diagram shows that the main pore diameter is 2.09 nm, which falls within the mesoporous category. Figure 3 b shows that the water contact angle of the material is 62.9°, indicating a high affinity for water, which is beneficial for utilizing protons, water molecules, and dissolved oxygen in the aqueous phase. The above characterization results demonstrate that the highly crystalline connective tissue-enhanced hydrophilic covalent organic framework nanofibers synthesized by the method in Example 1 maintain high crystallinity, possess favorable specific surface area and mesoporous structure, and exhibit good hydrophilicity. This is beneficial for optimizing catalyst light absorption, carrier formation, and interfacial reactant adsorption and activation processes, thereby achieving the goal of highly active photocatalytic oxygen reduction to hydrogen peroxide production.

[0055] Example 2

[0056] In this embodiment, the specific steps for preparing highly crystalline connector methoxy-functionalized connector hydrophilic covalent organic framework nanofibers are as follows:

[0057] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 23.3 mg (0.12 mmol) of 2,5-dimethoxyterephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to ensure uniform dispersion.

[0058] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Vacuum the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, vacuum and seal the tube to place the mixture in a vacuum environment. (3) Place the reactant obtained in step (2) in an oven and thermally polymerize it at 120℃ for 72 h. Wash the product three times with tetrahydrofuran and then three times with methanol.

[0059] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0060] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a golden yellow methoxy-functionalized covalent organic framework nanoporous fiber product, denoted as TAPT-OMe.

[0061] Example 3

[0062] In this embodiment, the specific steps for preparing highly crystalline hydroxyl-functionalized connector hydrophilic covalent organic framework nanofibers are as follows:

[0063] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 15.0 mg (0.09 mmol) of 2,5-dihydroxyterephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to disperse evenly.

[0064] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Evacuate the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, evacuate and seal the tube to place the mixture in a vacuum environment.

[0065] (3) The reactants obtained in step (2) were placed in an oven and subjected to thermal polymerization at 120°C for 72 h. The product was first washed three times by centrifugation with tetrahydrofuran, and then washed three times by centrifugation with methanol.

[0066] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0067] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a reddish-brown hydroxyl-functionalized connector hydrophilic covalent organic framework nanoporous fiber product, denoted as TAPT-OH.

[0068] like Figure 4 As shown in a, scanning electron microscopy results show that the morphology of the obtained highly crystalline connective organoenergetic hydrophilic covalent organic framework nanofibers is irregular nanofibers with a diameter of 30-40 nm. Visible protrusions grow on the surface of the nanofibers, which is beneficial to increasing the active area. Figure 4 In image b, a transmission electron microscope clearly captured significant lattice fringes corresponding to the (001) crystal plane, with a width of [missing information]. This indicates that COF maintains good crystallinity. Furthermore, Figure 5The sharp peaks at 2.7°, 5.0°, 5.7°, 7.6°, 9.9°, and 26.2° in the X-ray diffraction pattern correspond to the (100), (110), (200), (120), (220), and (001) crystal planes of TAPT-OH, respectively, demonstrating that COF has high structural order and crystallinity. According to... Figure 5 The Fourier transform infrared spectrum of b, at 1576 cm⁻¹ -1 The strong tensile vibration peak of C=N indicates the successful formation of the imine bond (C=N). The corresponding peak is 1663 cm⁻¹. -1 The C=O peak at 3368 cm⁻¹ is attributed to the uncondensed aldehyde group. -1 The characteristic vibrational peaks correspond to the -OH group, demonstrating the successful introduction of hydroxyl groups into the highly crystalline connective organ's hydrophilic covalent organic framework nanofibers, achieving electronic and interfacial microenvironmental modulation of the connector. Its structural formula is as follows:

[0069]

[0070] Figure 6 The nitrogen adsorption-desorption curves in sample a show that TAPT-OH exhibits a type IV adsorption isotherm, confirming its mesoporous structure. The specific surface area calculated using the BET method is 2176 m². 2 / g. The pore distribution diagram shows that the main pore diameter is 2.13 nm, which falls within the mesoporous category. Figure 6 b shows that the water contact angle of the material is 46.5°, indicating a high affinity for water, which is beneficial for utilizing protons, water molecules, and dissolved oxygen in the aqueous phase. The above characterization results demonstrate that the highly crystalline connective tissue-enhanced hydrophilic covalent organic framework nanofibers synthesized by the method in Example 3 maintain high crystallinity, possess favorable specific surface area and mesoporous structure, and exhibit good hydrophilicity. This is beneficial for optimizing catalyst light absorption, carrier formation, and interfacial reactant adsorption and activation processes, thereby achieving the goal of highly active photocatalytic oxygen reduction to hydrogen peroxide production.

[0071] Example 4

[0072] In this embodiment, the specific steps for preparing highly crystalline hydroxyl-functionalized connector hydrophilic covalent organic framework nanofibers are as follows:

[0073] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 20.0 mg (0.12 mmol) of 2,5-dihydroxyterephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to disperse evenly.

[0074] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Vacuum the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, vacuum and seal the tube to place the mixture in a vacuum environment. (3) Place the reactant obtained in step (2) in an oven and thermally polymerize it at 120℃ for 72 h. Wash the product three times with tetrahydrofuran and then three times with methanol.

[0075] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0076] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a reddish-brown hydroxyl-functionalized connector hydrophilic covalent organic framework nanoporous fiber product, denoted as TAPT-OH.

[0077] Example 5

[0078] In this embodiment, the specific steps for preparing highly crystalline bromine-functionalized connector hydrophilic covalent organic framework nanofibers are as follows:

[0079] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 26.3 mg (0.09 mmol) of 2,5-dibromo-terephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to ensure uniform dispersion.

[0080] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Evacuate the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, evacuate and seal the tube to put the mixture in a vacuum environment.

[0081] (3) The reactants obtained in step (2) were placed in an oven and subjected to thermal polymerization at 120°C for 72 h. The product was first washed three times by centrifugation with tetrahydrofuran, and then washed three times by centrifugation with methanol.

[0082] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0083] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a golden yellow bromine-functionalized connector hydrophilic covalent organic framework nanoporous fiber product, denoted as TAPT-Br.

[0084] like Figure 7 As shown in Figure a, scanning electron microscopy results show that the morphology of the obtained highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers is that of irregular nanofibers with a diameter of 20-40 nm and a relatively smooth surface. However, compared with the materials synthesized in other embodiments, the fiber length is significantly shorter. Figure 7 In image b, a transmission electron microscope clearly captured significant lattice fringes corresponding to the (001) crystal plane, with a width of [missing information]. This indicates that COF maintains good crystallinity. Furthermore, Figure 8 The sharp peaks at 2.7°, 5.7°, 7.6°, 9.8°, and 26.0° in the X-ray diffraction pattern correspond to the (100), (200), (120), (220), and (001) crystal planes of TAPT-Br, respectively, demonstrating that COF has high structural order and crystallinity. According to... Figure 8 The Fourier transform infrared spectrum of b, at 1576 cm⁻¹ -1 The strong tensile vibration peak of C=N indicates the successful formation of the imine bond (C=N). The corresponding peak is at 1693 cm⁻¹. -1 The C=O peak at 1054 cm⁻¹ is attributed to the uncondensed aldehyde group. -1 The characteristic vibrational peaks correspond to the -Br group, demonstrating the successful introduction of bromine substituents into this highly crystalline connective organ's hydrophilic covalent organic framework mesoporous nanofibers, achieving electronic and interfacial microenvironmental modulation of the connector. Its structural formula is as follows:

[0085]

[0086] Figure 9 The nitrogen adsorption-desorption curves in sample a show that TAPT-Br exhibits a type IV adsorption isotherm, confirming its mesoporous structure. The specific surface area calculated using the BET method is 1203 m². 2 / g. The pore distribution diagram shows that the main pore diameter is 2.20 nm, which falls within the mesoporous category. Figure 9 b shows that the water contact angle of the material is 46.5°, indicating a high affinity for water, which is beneficial for utilizing protons, water molecules, and dissolved oxygen in the aqueous phase. The above characterization results demonstrate that the highly crystalline connective tissue-enhanced hydrophilic covalent organic framework nanofibers synthesized by the method in Example 5 maintain high crystallinity, possess favorable specific surface area and mesoporous structure, and exhibit good hydrophilicity. This is beneficial for optimizing catalyst light absorption, carrier formation, and interfacial reactant adsorption and activation processes, thereby achieving the goal of highly active photocatalytic oxygen reduction to hydrogen peroxide production.

[0087] Example 6

[0088] In this embodiment, the specific steps for preparing highly crystalline bromine-functionalized connector hydrophilic covalent organic framework nanofibers are as follows:

[0089] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 35.1 mg (0.12 mmol) of 2,5-dibromo-terephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to ensure uniform dispersion.

[0090] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Vacuum the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, vacuum and seal the tube to place the mixture in a vacuum environment. (3) Place the reactant obtained in step (2) in an oven and thermally polymerize it at 120℃ for 72 h. Wash the product three times with tetrahydrofuran and then three times with methanol.

[0091] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0092] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a golden yellow bromine-functionalized connector hydrophilic covalent organic framework nanoporous fiber product, denoted as TAPT-Br.

[0093] Example 7

[0094] In this comparative embodiment, the functionalized terephthalaldehyde monomer used to prepare the hydrophilic covalent organic framework nanofibers of the highly crystalline functionalized connectors of the present invention was replaced with unsubstituted terephthalaldehyde as a comparative tool to study the actual effect of the connector functionalization method in the present invention on the photocatalytic production of hydrogen peroxide. The specific steps are as follows:

[0095] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 12.1 mg (0.09 mmol) of terephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to disperse evenly.

[0096] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Evacuate the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, evacuate and seal the tube to place the mixture in a vacuum environment.

[0097] (3) The reactants obtained in step (2) were placed in an oven and subjected to thermal polymerization at 120°C for 72 h. The product was first washed three times by centrifugation with tetrahydrofuran, and then washed three times by centrifugation with methanol.

[0098] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0099] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a light yellow unconnected organoenergized covalent organic framework nanoporous fiber product, denoted as TAPT-H.

[0100] like Figure 10 As shown in Figure a, scanning electron microscopy results indicate that the obtained highly crystalline connective organohydrophilic covalent organic framework nanofibers exhibit an irregular morphology with a diameter of 20–40 nm and a smooth surface. Figure 10 In image b, a transmission electron microscope clearly captured significant lattice fringes corresponding to the (001) crystal plane, with a width of [missing information]. This indicates that COF maintains good crystallinity. In particular, its lattice fringe width is higher than that of functionalized COF, indicating its weaker longitudinal conjugation, which conversely verifies the optimization of the electronic structure conjugation of COF by functional groups. Furthermore, Figure 11 The diffraction peaks at 2.8°, 4.9°, 5.9°, 7.5°, 9.8°, and 24.7° in the X-ray diffraction pattern correspond to the (100), (110), (200), (120), (220), and (001) crystal planes of TAPT-H, respectively. However, the intensities of these diffraction peaks are significantly lower than those of the functionalized COFs mentioned above, indicating their relatively weak structural order and crystallinity, which conversely demonstrates the crucial role of functional groups in maintaining the good crystallinity of COFs. Figure 11 The Fourier transform infrared spectrum of b, at 1576 cm⁻¹ -1 The strong tensile vibration peak at C=N indicates the successful formation of the imine bond (C=N). The corresponding peak at 1700 cm⁻¹... -1 The C=O peak at that point is attributed to the uncondensed aldehyde group. Figure 12The nitrogen adsorption-desorption curves in sample a show that TAPT-H exhibits a type IV adsorption isotherm, confirming its mesoporous structure. The specific surface area calculated using the BET method is 477 m². 2 / g, significantly lower than that of functionalized COF. The pore size distribution diagram shows that the main pore diameter is 2.09 nm, which falls within the mesoporous range. Figure 12 b shows that the water contact angle of the material is 70.3°, significantly lower than that of the functionalized COF in the above examples, indicating its lower affinity for water. The characterization results for Example 7 demonstrate that, due to the pre-designed synthesis method and mild cyclic vacuum sonication of this invention, the crystallinity of the unconnected organ-energized COF is maintained to some extent. However, its longitudinal conjugation and overall crystallinity are lower than those of the functionalized COF, attributed to the lack of functional group modification of the COF's electronic structure. Furthermore, TAPT-H exhibits the lowest specific surface area and water affinity, which is unfavorable for contact with reactants. The study of Comparative Example 7 highlights the important role of organ-energization in this invention, which can significantly improve the interfacial properties and electronic structure of COF, achieving efficient photocatalytic production of hydrogen peroxide.

[0101] Example 8

[0102] In this comparative embodiment, the functionalized terephthalaldehyde monomer used to prepare the hydrophilic covalent organic framework nanofibers of the highly crystalline functionalized connectors of the present invention was replaced with unsubstituted terephthalaldehyde as a comparative tool to study the actual effect of the connector functionalization method in the present invention on the photocatalytic production of hydrogen peroxide. The specific steps are as follows:

[0103] (1) Accurately weigh 21.3 mg (0.06 mmol) of 1,3,5-tris(4-aminophenyl)triazine and 16.1 mg (0.12 mmol) of terephthalaldehyde into a 10 ml Schlenk tube with a polytetrafluoroethylene vacuum stopper. Add 1 ml of n-butanol and 1 ml of o-dichlorobenzene to the tube and sonicate for 5 minutes to disperse evenly.

[0104] (2) Add 0.2 mL of 6 mol / L acetic acid aqueous solution and sonicate again for 5 min. Evacuate the Schlenk tube with an electric vacuum pump and seal it with a polytetrafluoroethylene vacuum plug. Continue sonication for 15 min to remove the gas in the liquid phase and allow the gas in the liquid phase to enter the gas phase layer in the tube. One vacuuming and sonication treatment constitutes one cycle. Repeat the vacuuming and sonication cycle 4 times. Finally, evacuate and seal the tube to place the mixture in a vacuum environment.

[0105] (3) The reactants obtained in step (2) were placed in an oven and subjected to thermal polymerization at 120°C for 72 h. The product was first washed three times by centrifugation with tetrahydrofuran, and then washed three times by centrifugation with methanol.

[0106] (4) Soak and stir in DMF for 10 hours to completely remove unreacted monomers. Use a PES membrane as a filter and perform vacuum filtration. Wash the catalyst with methanol during the filtration process.

[0107] (5) The catalyst obtained in step (4) was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain a light yellow unconnected organoenergized covalent organic framework nanoporous fiber product, denoted as TAPT-H.

[0108] Application Example 1

[0109] The application of the highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers of the present invention to the visible light-guided catalytic preparation of hydrogen peroxide includes the following specific steps:

[0110] (1) Using a glass jacketed beaker as a reaction vessel, weigh 5 mg of the catalyst prepared in the above example, add it to 50 ml of pure water, and sonicate it for 15 min to make the catalyst uniformly dispersed in the liquid phase.

[0111] (2) Before the photocatalytic reaction, place the container in the dark and bubble O2 into the reaction mixture at a flow rate of 50 mL / min while magnetically stirring for 20 min to achieve O2 adsorption-desorption equilibrium.

[0112] (3) The catalytic reaction light source is a 300W metal halide lamp with a cutoff filter (λ>400nm, light intensity 100mWcm). -2 During illumination, the suspension was continuously stirred and O2 was introduced at a flow rate of 25 ml / min.

[0113] (4) Every 30 minutes, 1 ml of solution was drawn from the reactor using a syringe with a 0.22 μm filter. The concentration of H2O2 was determined by the potassium titanate oxalic acid method.

[0114] (4) The specific procedure for determining hydrogen peroxide concentration using the potassium titanium oxalate method is as follows: Add 1 ml of the reaction system solution to a 10 ml stoppered colorimetric tube, use 2 ml of 0.05 mol / L potassium titanium oxalate aqueous solution as the colorimetric reagent, and use 1 ml of 3 mol / L sulfuric acid solution to adjust the pH to facilitate the formation of a stable complex. Dilute to 10 ml. Use a UV spectrophotometer to measure the absorbance at a wavelength of 400 nm with a deionized water blank as a reference. Finally, calculate the hydrogen peroxide concentration by referring to the standard curve.

[0115] Data processing was performed on the above experimental results to obtain the yield results of the photocatalytic hydrogen peroxide production reaction after 2 hours, as shown in Table 1. Functionalized COFs (Examples 1-6) all exhibited enhanced photocatalytic hydrogen peroxide production activity compared to unfunctionalized COFs. In Example 3, when the selected precursors were 1,3,5-tris(4-aminophenyl)triazine and 2,5-dihydroxyterephthalaldehyde in a molar ratio of 1:1.5, the synthesized highly crystalline linker-functionalized hydrophilic covalent organic framework nanofibers showed the highest activity in the catalytic production of hydrogen peroxide under visible light. After 2 hours of catalytic reaction, the yield of hydrogen peroxide was 3406.3 μmol·h⁻¹. -1 ·g -1 This indicates that the highly crystalline hydroxyl-functionalized connector hydrophilic covalent organic framework possesses optimal crystallinity, specific surface area, pore size distribution, and water affinity. The method proposed in this invention provides a mild and simple preparation method, avoiding the destruction of the COF crystal structure caused by post-synthetic modification. Furthermore, atomic-level hydroxyl modulation optimizes the electronic and interfacial properties of the COF, significantly improving the catalytic activity of the material for photocatalytic hydrogen peroxide production under visible light. The overall activity order of the materials prepared in the above examples is: hydroxyl-functionalized COF > methoxy-functionalized COF > bromine-functionalized COF > unfunctionalized COF. For the same functional group, the catalytic activity of the two monomers in a molar ratio of 1:1.5 is higher than that of the hydrogen peroxide catalytic production activity in a molar ratio of 1:2. These results all indicate that the highly crystalline connective organ-enhanced hydrophilic covalent organic framework nanofibers proposed in this invention can optimize the electronic configuration, planar and longitudinal π-conjugation, specific surface area and porosity, and hydrophilicity of the original COF, thereby improving the photoreaction stability of the material and the utilization rate of reactants, and thus enhancing the photocatalytic activity for hydrogen peroxide production.

[0116] Table 1. Highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers prepared in different embodiments.

[0117] Hydrogen peroxide yield (μmol·h) after 2 hours of irradiation -1 ·g -1 )

[0118]

[0119] Through detailed descriptions of specific embodiments, this invention has comprehensively introduced the preparation method of highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers and the method for photocatalytic hydrogen peroxide production. This aims to assist researchers and technicians in related fields to better understand the specific steps and core concepts of this invention.

[0120] Obviously, the above embodiments are merely illustrative examples for clarity and not intended to limit the specific implementation. Those skilled in the art can make other changes or adjustments based on the above description without compromising the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, the invention also includes these modifications and variations.

Claims

1. A method for preparing highly crystalline connective organ-energized hydrophilic covalent organic framework nanofibers, characterized in that, Includes the following steps: 1) Add 1,3,5-tris(4-aminophenyl)triazine and terephthalaldehyde with different functional groups to a Schlenk tube with a polytetrafluoroethylene vacuum stopper, add mixed organic solvent A to the tube, and mix evenly by ultrasonication to obtain a precursor suspension. 2) At room temperature and pressure, add acetic acid solution to the precursor suspension obtained in step 1), mix ultrasonically, and use the cyclic ultrasonic vacuum method to obtain the mixture to be treated B; 3) Place the Schlenk tube containing mixture B in an oven for reaction, cool to room temperature after the reaction is complete, and thoroughly clean it to obtain a highly crystalline connective organ-energized hydrophilic covalent organic framework nanoporous fiber material. The specific operation of the cyclic ultrasonic vacuum method is as follows: use an electric vacuum pump to extract the air from the Schlenk tube and seal it. After sealing, continue to ultrasonically mix the mixture in the tube evenly. Use ultrasonic oscillation to allow the dissolved gas in the solvent to enter the gas phase layer in the tube and remove it in the second vacuuming operation. One vacuuming followed by ultrasonic treatment is considered as one set of operations. Repeat 3 to 7 times. Finally, vacuum and seal the tube to place the mixture in a vacuum environment.

2. The preparation method according to claim 1, characterized in that, In step 1), the terephthalaldehydes substituted with different functional groups are 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, or 2,5-dibromoterephthalaldehyde.

3. The preparation method according to claim 1, characterized in that, In step 1), the mixed organic solvent A is a mixture of n-butanol and o-dichlorobenzene, wherein the volume ratio of n-butanol to o-dichlorobenzene is controlled at 1:0.5~1.

5.

4. The preparation method according to claim 1 or 2, characterized in that, In step 1), the molar ratio of the two monomers 1,3,5-tris(4-aminophenyl)triazine and functionalized terephthalaldehyde is 1:1 to 2.

5.

5. The preparation method according to claim 1 or 3, characterized in that, In step 1), the ratio of the volume of the mixed organic solvent A to the molar amounts of the two monomers, 1,3,5-tris(4-aminophenyl)triazine and functionalized terephthalaldehyde, is 1 ml: 0.05~0.12 mmol.

6. The preparation method according to claim 1, characterized in that, In step 2), the concentration of the acetic acid solution is controlled at 4-8 mol / L, and the volume ratio of the acetic acid solution to the volume of the mixed organic solvent A is controlled at 1:5-20.

7. The preparation method according to claim 1, characterized in that, In step 3), mixture B is transferred to an oven for monomer covalent polymerization. The reaction temperature is controlled at 110~130℃ and the duration is controlled at 60~80 h.

8. The preparation method according to claim 1, characterized in that, The thorough washing step in step 3) is as follows: centrifuge and wash 2-4 times each with tetrahydrofuran and methanol, stir in N,N-dimethylformamide for 6-14 h to completely remove unreacted monomers, and finally filter and separate the obtained product; the vacuum drying temperature is controlled at 50-70℃ and the duration is controlled at 10-14 h.

9. A highly crystalline connective organ-energized hydrophilic covalent organic framework nanofiber prepared by any one of the preparation methods described in claims 1 to 8, exhibiting distinct lattice fringes, with the following structural formula: ， in, X is selected from OMe, OH, or Br.

10. The application of the highly crystalline connective organoenergetic hydrophilic covalent organic framework nanofiber as described in claim 9 in the photocatalytic production of hydrogen peroxide.

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