Visible light response quinoline bond connected covalent organic framework material and preparation method and application thereof

Abstract

The present application relates to a kind of visible light response quinoline bond connection covalent organic framework material and its preparation method and application, with 1,3,5-tri (4-aminophenyl) benzene, 2,5-dimethoxy benzene formaldehyde and phenylacetylene as raw material, first by Schiff base condensation reaction to build stable imine bond covalent organic framework, then using post-modification strategy, by nitrogen hetero-Diels-alder reaction imine bond and phenylacetylene are ring addition, and further oxidation aromatization, form stable quinoline ring connection structure, to realize the conversion from imine bond to quinoline unit. The obtained quinoline bond connection covalent organic framework material (named QN-TAPB-COF) under visible light irradiation, to sulfide compound exhibits superhigh selectivity oxidation rate, and has good reusability and chemical stability. By the photocatalytic oxidation test of multiple sulfide compounds, the conversion rate and selectivity of QN-TAPB-COF reach more than 90%.

Description

Technical Field

[0001] This invention relates to the fields of photocatalysis and selective organic synthesis, specifically to a visible light-responsive quinoline-linked covalent organic framework material, its preparation method, and its application in the selective oxidation of thioether compounds. Background Technology

[0002] Sulfoxides, generated by the selective oxidation of thioethers, are crucial organic synthesis intermediates and molecular building blocks in pharmaceuticals, agrochemicals, and materials science, representing a frontier in organic chemistry and chemical synthesis. Currently, traditional methods for the selective oxidation of thioethers to prepare sulfoxides mainly include peroxyacid oxidation, hydrogen peroxide oxidation, metal-catalyzed oxidation, and biocatalysis. However, these methods all suffer from significant technical drawbacks: peroxyacid oxidation easily generates byproducts and poses safety hazards; hydrogen peroxide oxidation requires stringent control of reaction conditions; metal-catalyzed oxidation easily causes transition metal ion dissolution and contamination; and biocatalysis suffers from low catalytic efficiency and narrow substrate applicability. Furthermore, all traditional methods generally suffer from poor selectivity, high energy consumption, and the potential for secondary pollution, severely limiting their application in large-scale industrial production.

[0003] In recent years, visible light-driven photocatalysis, using solar energy as its energy source, has become an ideal route for the green selective oxidation of sulfides to produce sulfoxides due to its advantages of mild reaction conditions and no secondary pollution. The performance of the catalytic material is the core key to the industrial application of this technology. Covalent organic frameworks (COFs), as a new type of organic porous photocatalytic material, have shown great application potential in the field of photocatalysis due to their characteristics such as precisely designable structure, regular pore system, excellent chemical and thermal stability, and good light absorption capacity, making them one of the preferred catalytic materials for the photocatalytic oxidation of sulfides.

[0004] Currently, most COFs used in the photocatalytic oxidation of sulfides have imine-bonded structures. These materials suffer from two major technical shortcomings: First, the imine bonds themselves have poor chemical stability and are prone to hydrolysis or structural degradation in the photocatalytic reaction system, resulting in poor recyclability and difficulty in meeting the industrial requirements of continuous catalysis. Second, the electronic polarity of imine-bonded COFs is not well regulated, resulting in a fast recombination rate and low separation efficiency of photogenerated electron-hole pairs, as well as a slow interfacial electron transfer rate, which limits the photocatalytic performance and prevents the efficient and selective oxidation of sulfide compounds.

[0005] To address the stability issue of imine-bonded COFs, researchers attempted to construct quinoline-bonded COF materials, leveraging the high stability of quinoline bonds to improve the recyclability of the materials. However, existing methods for preparing quinoline-bonded COFs have significant drawbacks. The resulting quinoline-bonded COFs exhibit poor crystallinity, leading to disordered pore structures and reduced specific surface area. This not only hinders oxygen reduction reactions but also significantly reduces the mass transfer efficiency of reactants, ultimately resulting in photocatalytic activity and selectivity failing to meet practical application requirements.

[0006] In summary, there is an urgent need to develop a COFs photocatalytic material that combines high crystallinity, high stability, and high photocatalytic performance, along with a green and efficient preparation method. This would address the pollution, low efficiency, and low selectivity issues in existing selective oxidation technologies for sulfides, as well as the technical bottlenecks of poor stability, insufficient crystallinity, and limited photocatalytic performance of existing COFs catalytic materials. Ultimately, this would promote the development of green synthesis processes for sulfides. Summary of the Invention

[0007] To address the limitations in photocatalytic performance caused by poor stability of imine-linked structures, insufficient electronic polarity regulation, and poor crystallinity of quinoline-linked organic covalent frameworks in existing technologies, this invention proposes a visible-light-responsive quinoline-linked covalent organic framework material, its preparation method, and its applications. An imine-linked covalent organic framework is generated via a Schiff base condensation reaction, followed by in-situ modification using the imine-linked covalent organic framework as a substrate through an aza-Diesle-Alder reaction. This modulates stable quinoline linkages, forming a quinoline-linked COF. This regulatory strategy effectively enhances the catalytic selectivity and product yield of the thioether oxidation reaction while maintaining high crystallinity. It also significantly improves the separation efficiency of photogenerated charges and the interfacial electron transfer rate, thereby greatly improving the photocatalytic degradation efficiency and material stability, meeting the requirements for selective oxidation of thioethers.

[0008] The solution of this invention to the above-mentioned technical problems is as follows: a visible light-responsive quinoline-linked covalent organic framework material, the structural formula of which is as follows: .

[0009] The preparation method of the visible light-responsive quinoline-linked covalent organic framework material described above has the following synthetic route: The synthesis steps are as follows: 1) Mix 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxytetraphenyldialdehyde, add an organic solvent and an aqueous solution of glacial acetic acid, and homogenize to obtain a mixed solution; 2) The mixed solution obtained in step 1) is subjected to multiple freezing, vacuuming, and thawing processes to remove dissolved oxygen. It is then sealed under vacuum conditions, heated, cooled to room temperature, filtered to obtain a precipitate, washed and extracted, and then vacuum dried to obtain an imine-linked covalent organic framework material. 3) The imine-linked covalent organic framework material obtained in step 2) is mixed with tetrachlorobenzoquinone, an organic solvent, phenylacetylene, and boron trifluoride-diethyl ether complex, and then homogenized to obtain a mixed solution; 4) The mixed solution obtained in step 3) is heated and reacted under an argon atmosphere, cooled to room temperature, filtered to obtain a precipitate, and the precipitate is washed and extracted to obtain a visible light responsive quinoline bonded covalent organic framework material.

[0010] The QN-TAPB-COF framework constructed in this invention uses 1,3,5-tris(4-aminophenyl)benzene as the structural unit. Its repeating units exhibit a characteristic hexagonal crystal arrangement, forming a highly planarized extended π-conjugated system, which significantly enhances the electron delocalization effect and promotes the effective separation of photogenerated electron-hole pairs. This hexagonal stacking structure allows for precise control of pore characteristics, achieving tight packing of the framework and thus obtaining a high specific surface area (BET). This is beneficial for the oxygen reduction reaction and improves the mass transfer efficiency of reactants, ultimately significantly enhancing photocatalytic activity.

[0011] Preferably, in step 1), the molar ratio between 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde, and glacial acetic acid is 1:1.5:15~16; the concentration of the glacial acetic acid aqueous solution is 6 mol / L, and the volume ratio of the glacial acetic acid aqueous solution to the organic solvent is 1:2~5.

[0012] Glacial acetic acid, as a bifunctional catalyst, has both catalytic activity and pH regulation function. Its dosage needs to be precisely controlled: when the amount added is within the optimal range, it can effectively promote the kinetics of Schiff base condensation reaction; while deviating from the appropriate amount will lead to an imbalance in the degree of polymerization regulation, thereby affecting the product yield and the integrity of the crystal structure.

[0013] Preferably, in step 1), the organic solvent is a mixture of n-butanol and o-dichlorobenzene in a volume ratio of 1:1.

[0014] o-Dichlorobenzene ensures the complete dissolution of 1,3,5-tris(4-aminophenyl)benzene, avoiding amorphous aggregation caused by localized overconcentration. n-Butanol guides the ordered assembly of monomers through hydrogen bonding, while moderately reducing overall solubility, promoting slow crystallization of the product at suitable supersaturation. Furthermore, o-dichlorobenzene's low polarity slows the reaction rate, while n-butanol's high polarity accelerates it; their synergy makes the reaction rate controllable.

[0015] Preferably, in step 2), the heating temperature is 110~130 ℃ and the heating time is 72 h.

[0016] Preferably, in step 3), the molar ratio of tetrachlorobenzoquinone, phenylacetylene, and boron trifluoride-ethyl ether complex is 2:3.5~4.5:0.8~1.2; the molar ratio of imine bonds to tetrachlorobenzoquinone in the imine-linked covalent organic framework material is 1:1~2.

[0017] Further optimization yields a molar ratio of tetrachlorobenzoquinone, phenylacetylene, and boron trifluoride-ethyl ether complex of 2:4:1; and a molar ratio of imine bonds to tetrachlorobenzoquinone in the imine-linked covalent organic framework material of 1:1.5.

[0018] The boron trifluoride-diethyl ether complex serves as the catalyst in this reaction, its core role being to activate the azadiene and accelerate the concerted cycloaddition. Tetrachlorobenzoquinone acts as the oxidant, its core role being to aromatize the dihydroquinoline intermediate into a stable quinoline ring. Since the boron trifluoride-diethyl ether complex catalyzes the cycloaddition to form the dihydroquinoline intermediate, and the tetrachlorobenzoquinone simultaneously undergoes oxidation, dehydrogenation, and aromatization to form the quinoline ring, the two steps are seamlessly connected. Considering the amount of tetrachlorobenzoquinone used and the reaction progress, approximately half the amount is used. Phenylacetylene, as one of the reactants in the aza-Diels-Alder reaction, is used in excess to drive the cyclization reaction to completion. The amount of tetrachlorobenzoquinone used is approximately 1.5 times that of the imine bond; this excess amount ensures complete oxidation of the imine and allows the reaction to proceed to completion.

[0019] Preferably, in step 3), the organic solvent is toluene, and the molar ratio of toluene to tetrachlorobenzoquinone is 310~320:1.

[0020] Toluene is nonpolar and its polarity is highly matched to the substrate (imine-bonded covalent organic framework) of the aza-Diels-Alder reaction in this experiment, enabling a homogeneous reaction. Furthermore, toluene is an inert solvent, stable in the aza-Diels-Alder reaction and does not react with imines. Toluene has a boiling point of 110.6 °C, and the optimal reflux temperature for the aza-Diels-Alder reaction is around 110 °C. The high selectivity of the aza-Diels-Alder reaction depends on its concerted cycloaddition mechanism, and the nonpolar environment provided by toluene is crucial for maintaining this mechanism. For example, nonpolar solutions have a moderate solvation effect on the cyclic transition state, lowering the transition state energy barrier and promoting the concerted reaction.

[0021] Preferably, in step 4), the heating temperature is 100~120 ℃ and the heating time is 72 h.

[0022] The application of the visible light-responsive quinoline-linked covalent organic framework material described above in the selective oxidation reaction of thioether compounds involves dispersing the covalent organic framework material in a solution of the thioether compound and carrying out a selective oxidation reaction under light irradiation.

[0023] The sulfide compound is any one of anisole, p-methyl anisole, p-methoxy anisole, p-fluoroanisole, p-chloroanisole, p-bromoanisole, p-iodoanisole, 2-methoxyanisole, 3-methoxyanisole, 3-chloroanisole, cyclohexylmethyl sulfide, and di-n-butyl disulfide.

[0024] When light irradiates QN-TAPB-COF, charge separation occurs, accompanied by the transport of electrons and holes, along with e and h. + The transport of participates in the conversion reaction. For e, it drives the reduction of O2 to O2. •- For h + The sulfide ester (such as methyl phenyl sulfide) is oxidized to form a positively charged intermediate. Then, the S-centered intermediate is reacted with O2. •- It is oxidized to form a persulfide intermediate, which is then converted into the final methyl phenyl sulfoxide in the presence of methanol solvent.

[0025] The beneficial effects of this invention are as follows: 1. Unique and Superior Structure: The visible-light-responsive quinoline-linked covalent organic framework photocatalyst (denoted as QN-TAPB-COF) constructed in this invention is first synthesized from 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxy-terephthalaldehyde as raw materials to obtain imine-linked COF with good crystallinity. Then, QN-TAPB-COF is synthesized by post-modification using imine-linked COF and phenylacetylene as building units. Its repeating units have a characteristic hexagonal crystal system arrangement, forming a highly planarized extended π-conjugated system, which can significantly enhance the electron delocalization effect and promote the effective separation of photogenerated electron-hole pairs. This hexagonal stacking structure can precisely control the pore characteristics and achieve tight packing of the framework, thereby obtaining a high specific surface area (BET), which is beneficial to the oxygen reduction reaction and improves the mass transfer efficiency of reactants, ultimately significantly improving the photocatalytic activity.

[0026] 2. Innovative Synthetic Method: This invention first generates a highly crystalline covalent organic framework linked by imine bonds via a Schiff base condensation reaction. Then, using the aza-Diesel-Alder method, a stable quinoline bond structure is constructed in situ on the imine bonds while maintaining the original COF framework structure. This allows for the generation of quinoline bonds while ensuring the high crystallinity of the COF.

[0027] 3. Enhanced photocatalytic performance: By directionally converting imine bonds into quinoline bonds, the QN-TAPB-COF of this invention can effectively absorb visible light and improve the separation efficiency of photogenerated electrons and holes, thereby significantly enhancing the photocatalytic selective oxidation of sulfide compounds.

[0028] 4. Stability and Recyclability: The QN-TAPB-COF material in this invention exhibits excellent structural stability before and after the reaction, maintaining a selectivity of over 90% even after continuous operation. Cyclic experiments show that its selectivity remains above 90% after multiple reuses. Furthermore, the synthesis of quinoline bonds can further improve the stability of the COF material.

[0029] 5. Green and environmentally friendly: It operates efficiently under blue light (460 nm, visible light) conditions, saving energy and protecting the environment. Furthermore, its all-organic composition avoids the risk of transition metal leaching, and the reaction process generates no secondary pollutants, reducing environmental pollution. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram illustrating the synthesis principle of the visible light responsive quinoline bond-linked covalent organic framework photocatalyst (QN-TAPB-COF) of this invention. Figure 2 Morphological images of QN-TAPB-COF and TAPB-COF provided in Comparative Example 1 and Example 1; a is a scanning electron microscope image of QN-TAPB-COF; b is a scanning electron microscope image of TAPB-COF; c is a transmission electron microscope image of QN-TAPB-COF; d is a transmission electron microscope image of TAPB-COF; Figure 3 The material structure diagrams of QN-TAPB-COF and TAPB-COF provided in Comparative Example 1 and Example 1 are shown. a is the XRD pattern of TAPB-COF provided in Comparative Example 1 and Example 1; b is the XRD pattern of QN-TAPB-COF provided in Comparative Example 1 and Example 1; c shows the FITR diagrams of TAPB-COF and QN-TAPB-COF provided in Comparative Example 1 and Example 1; d represents solid-state TAPB-COF and QN-TAPB-COF. 13 C1 NMR image; e is the fine XPS spectrum of N 1s of TAPB-COF; f is the fine XPS spectrum of N 1s of QN-TAPB-COF; g is the BET test plot of TAPB-COF; h is the BET test plot of QN-TAPB-COF.

[0031] Figure 4 Photoelectric performance test diagrams of TAPB-COF and QN-TAPB-COF provided in Comparative Example 1 and Example 1; a provides the UV and Tauc spectra of TAPB-COF and QN-TAPB-COF for Comparative Example 1 and Example 1; b provides a graph of the Mott-Schottky (MS) measurement results for TAPB-COF for Comparative Example 1; c provides the Mott-Schottky (MS) measurement results for QN-TAPB-COF in Example 1; d provides the band structure diagrams of TAPB-COF and QN-TAPB-COF for Comparative Example 1 and Example 1; e provides electrochemical impedance spectroscopy for TAPB-COF and QN-TAPB-COF for Comparative Example 1 and Example 1; f represents the transient photocurrent spectra of TAPB-COF and QN-TAPB-COF provided in Comparative Example 1 and Example 1; Figure 5 TGA spectra of TAPB-COF and QN-TAPB-COF provided in Comparative Example 1 and Example 1; Figure 6 Examples of selective oxidation of three thioether compounds by TAPB-COF and QN-TAPB-COF, provided for Comparative Example 1 and Example 1; Figure 7 Kinetic experimental diagrams of the selective oxidation of anisole by TAPB-COF and QN-TAPB-COF are provided for Comparative Example 1 and Example 1. Figure 8 The diagram shows the cyclic experiment of selective oxidation of anisole by QN-TAPB-COF, which is provided for Comparative Example 1 and Example 1. Detailed Implementation

[0032] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0033] The working principle of this invention is as follows: Figure 1As shown, this invention uses 1,3,5-tris(4-aminophenyl)benzene (TAPB) as a raw material to first construct a highly crystalline imine-linked covalent organic framework photocatalyst (TAPB-COF) material. Then, through a post-modification strategy, the linking bonds are transformed from imine bonds to quinoline bonds via a azir-Diels-Alder reaction. The hexagonal COF structure containing quinoline linkages synthesized using this method possesses unique structural features that enhance photocatalytic performance while maintaining the crystallinity of the quinoline-linked covalent organic framework. This unique framework provides precise pore control, promotes tight framework stacking, and is beneficial for efficient oxygen reduction reactions. Furthermore, this ordered structure accelerates mass transfer of reactants, offering significant advantages in photocatalytic applications.

[0034] Compared to imine-linked covalent organic frameworks, quinoline-linked covalent organic frameworks exhibit better material stability, photoelectric properties, and a wider light absorption range while maintaining high crystallinity. This design strategy demonstrates that quinoline-linked covalent organic frameworks obtained through post-modification methods possess good crystallinity. It also reveals the impact of changes in the linking bonds on photocatalytic activity and provides theoretical guidance and practical pathways for constructing highly selective and efficient photocatalytic materials.

[0035] Comparative Example 1 This embodiment provides a visible light-responsive imine-linked covalent organic framework material (denoted as TAPB-COF), comprising the following steps: 1) Add 1,3,5-tris(4-aminophenyl)benzene (16.8 mg, 0.048 mmol), 2,5-dimethoxytetraphenyldialdehyde (14 mg, 0.072 mmol), 0.2 ml n-butanol, 0.2 ml o-dichlorobenzene, and 0.125 ml aqueous acetic acid solution (6 M) to a Pyrex tube (15 mL), and sonicate for 5 minutes to obtain a uniformly dispersed TAPB-COF composite solution; 2) The TAPB-COF composite solution was subjected to three freezing, vacuuming, and thawing processes to remove dissolved oxygen. It was then sealed under vacuum conditions, placed in an oven at 120 °C and heated for 72 h. After cooling to room temperature, the precipitate was collected by filtration. 3) After washing with N,N-dimethylformamide (DMF), dioxane (1,4-dioxane), methanol, and acetone in sequence, followed by Soxhlet extraction with THF for 24 h, the product was dried under vacuum at 60 °C for 12 h to obtain TAPB-COF.

[0036] Example 1 This embodiment provides a visible light-responsive quinoline-linked covalent organic framework material (denoted as QN-TAPB-COF), comprising the following steps: 1) Take TAPB-COF (40 mg), tetrachlorobenzoquinone (80 mg, 0.3 mmol), phenylacetylene (66 µL, 0.6 mmol), toluene (10 ml) and boron trifluoride-diethyl ether complex (20 µL, 0.15 mmol) prepared in Comparative Example 1 and put them into a 25 ml round-bottom flask. Place the round-bottom flask in an oil bath at 110 °C and react for three days under an argon atmosphere. Filter and collect the precipitate. 2) The precipitate was quenched with sodium bicarbonate, washed with deionized water and tetrahydrofuran, extracted with THF by Soxhlet for 24 h, and then dried under vacuum at 80 °C for 12 h to obtain QN-TAPB-COF.

[0037] The following characterization tests were performed on the TAPB-COF prepared in Comparative Example 1 and the QN-TAPB-COF prepared in Example 1: I. Morphological Test like Figure 2 As shown, scanning electron microscopy images reveal the morphology and microstructure of TAPB-COF and QN-TAPB-COF, both of which exhibit characteristic clustered structures. Transmission electron microscopy shows obvious lattice fringes in both COFs, confirming that the synthesized COFs have high crystallinity.

[0038] II. Structural Testing like Figure 3 As shown, the XRD spectra comparison reveals that TAPB-COF and QN-TAPB-COF are highly crystalline materials. The FITR spectra show that QN-TAPB-COF exhibits a crystallinity at 1542 cm⁻¹. -1 The diffraction peak at 1600 cm⁻¹ belongs to the aromatic quinoline bond, and the peak at 1600 cm⁻¹ is also related to the diffraction peak at 1600 cm⁻¹. -1 The near disappearance of the C=N characteristic vibration at the point indicates the consumption of the imine bond. XPS revealed that the fitted N 1s peak corresponding to the pyridine nitrogen in the quinoline ring of QN-TAPB-COF appeared at 399.48 eV, confirming the successful construction of the quinoline linkage.

[0039] III. Photoelectric Performance Testing like Figure 4 As shown in Figure a, the optical band gaps of TAPB-COF and QN-TAPB-COF are derived to be 2.40 eV and 2.30 eV, respectively, using the corresponding Tauc plotting method. Figure 4 As shown in b and 4c, the flat band potentials (V) of TAPB-COF and QN-TAPB-COF are... fb The values ​​were -0.95 V and -1.00 V (relative to Ag / AgCl, pH = 7), respectively. Based on the above tests, the band structure diagrams of TAPB-COF and QN-TAPB-COF were obtained, as shown below. Figure 4 As shown in d.

[0040] To evaluate the separation efficiency of photogenerated carriers in the two photocatalysts, photocurrent density was measured, such as... Figure 4 As shown in Figure e, QN-TAPB-COF exhibits the highest photocurrent density, indicating its excellent charge separation and photocatalytic performance. Electrochemical impedance spectroscopy (EIS) further confirms this. Figure 4 f shows that the Nyquist arc radius of QN-TAPB-COF is the smallest, indicating that the charge transfer resistance is the smallest.

[0041] IV. Thermal stability test like Figure 5 As shown in the TGA spectrum, the quinoline-linked QN-TAPB-COF formed by post-modification can still maintain the integrity of its structure at 350 °C, indicating that it has excellent thermal stability.

[0042] The QN-TAPB-COF prepared in Example 1 was applied to the selective oxidation reaction of sulfide compounds, and the reaction formula is as follows: .

[0043] Application Example 1 In a solution containing 1 mL methanol, 20 µL bromobenzene, and 35.2 µL anisole, 5 mg of TAPB-COF from Comparative Example 1 was added and dispersed. The dispersion was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium, followed by irradiation under blue light (λ = 460 nm). The entire reaction was carried out under oxygen conditions. At predetermined time intervals, 20 µL of the suspension and 980 µL of methanol were centrifuged, and the supernatant was collected. Finally, the product was analyzed by gas chromatography using a flame ionization detector (GC-FID), with bromobenzene as an internal standard.

[0044] Application Example 2 In a solution containing 1 mL methanol, 20 µL bromobenzene, and 35.2 µL anisole, 5 mg of QN-TAPB-COF provided in Example 1 was added and dispersed. The dispersed suspension was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium, followed by irradiation under blue light (λ = 460 nm). The entire reaction was carried out under oxygen conditions. At predetermined time intervals, 20 µL of the suspension and 980 µL of methanol were centrifuged, and the supernatant was collected. Finally, the product was analyzed by gas chromatography using a flame ionization detector (GC-FID), with bromobenzene as an internal standard.

[0045] The comparison between the two yields the following results (expressed in dynamic form): Figure 6As shown, QN-TAPB-COF exhibits superior performance under visible light conditions. Under 1.5 h of blue light irradiation, the concentration of anisole by QN-TAPB-COF continuously decreased, while the conversion rate continuously increased, both of which were superior to TAPB-COF. After 1.5 h, the conversion rate of anisole by QN-TAPB-COF was 95%.

[0046] Application Example 3 In a solution containing 1 mL methanol, 20 µL bromobenzene, and 36.6 µL p-fluoroanisole, 5 mg of TAPB-COF (from Comparative Example 1) was added and dispersed. The dispersion was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium, followed by irradiation under blue light (λ = 460 nm). The entire reaction was carried out under oxygen conditions. At predetermined time intervals, 20 µL of the suspension and 980 µL of methanol were centrifuged, and the supernatant was collected. Finally, the product was analyzed by gas chromatography using a flame ionization detector (GC-FID), with bromobenzene as an internal standard.

[0047] Application Example 4 In a solution containing 1 mL methanol, 20 µL bromobenzene, and 36.6 µL p-fluoroanisole, 5 mg of QN-TAPB-COF provided in Example 1 was added and dispersed. The dispersion suspension was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium, followed by irradiation under blue light (λ = 460 nm). The entire reaction was carried out under oxygen conditions. At predetermined time intervals, 20 µL of the suspension and 980 µL of methanol were centrifuged, and the supernatant was collected. Finally, the product was analyzed by gas chromatography using a flame ionization detector (GC-FID), with bromobenzene as an internal standard.

[0048] Application Example 5 In a solution containing 1 mL methanol, 20 µL bromobenzene, and 40.4 µL p-methyl anisole, 5 mg of TAPB-COF (from Comparative Example 1) was added and dispersed. The dispersion was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium, followed by irradiation under blue light (λ = 460 nm). The entire reaction was carried out under oxygen conditions. At predetermined time intervals, 20 µL of the suspension and 980 µL of methanol were centrifuged, and the supernatant was collected. Finally, the product was analyzed by gas chromatography using a flame ionization detector (GC-FID), with bromobenzene as an internal standard.

[0049] Application Example 6 In a solution containing 1 mL methanol, 20 µL bromobenzene, and 40.4 µL p-methyl anisole, 5 mg of QN-TAPB-COF provided in Example 1 was added and dispersed. The dispersed suspension was stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium, followed by irradiation under blue light (λ = 460 nm). The entire reaction was carried out under oxygen conditions. At predetermined time intervals, 20 µL of the suspension and 980 µL of methanol were centrifuged, and the supernatant was collected. Finally, the product was analyzed by gas chromatography using a flame ionization detector (GC-FID), with bromobenzene as an internal standard.

[0050] Application Examples 3-6 further employed other sulfide compounds, such as p-methyl anisole and p-fluoroanisole, to test TAPB-COF and QN-TAPB-COF, demonstrating the superior selective oxidation of sulfide compounds by QN-TAPB-COF. The results are as follows: Figure 7 As shown, the conversion rates of p-methyl anisole, anisole, and p-fluoroanisole were recorded within 0-1.25 h. It can be seen that the conversion rates of QN-TAPB-COF for other sulfides are higher than those of TAPB-COF, indicating the superiority of QN-TAPB-COF in the selective oxidation of sulfide compounds.

[0051] Further cyclic stability tests were conducted on QN-TAPB-COF, repeating the sampling steps of Example 2 without adding the catalyst again. The results are as follows: Figure 8 As shown, QN-TAPB-COF maintained excellent photocatalytic activity throughout all four cycles.

[0052] Further versatility testing of QN-TAPB-COF was conducted, and the results are shown in Table 1. Besides anisole, QN-TAPB-COF also exhibits broad-spectrum activity against a variety of sulfide compounds, including p-methyl anisole, p-methoxy anisole, p-fluoroanisole, p-chloroanisole, p-bromoanisole, p-iodoanisole, 2-methoxyanisole, 3-methoxyanisole, 3-chloroanisole, cyclohexylmethyl sulfide, and di-n-butyl disulfide. This confirms the universality of QN-TAPB-COF in the selective oxidation of sulfide compounds.

[0053] Table 1. Selective oxidation effect of QN-TAPB-COF on different sulfide compounds The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A visible light-responsive quinoline-linked covalent organic framework material, characterized in that, Its structural formula is as follows: 。 2. A method for preparing a visible light-responsive quinoline-linked covalent organic framework material as described in claim 1, characterized in that, Its synthesis circuit is as follows: The synthesis steps are as follows: 1) Mix 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxytetraphenyldialdehyde, add an organic solvent and an aqueous solution of glacial acetic acid, and homogenize to obtain a mixed solution; 2) The mixed solution obtained in step 1) is subjected to multiple freezing, vacuuming, and thawing processes to remove dissolved oxygen. It is then sealed under vacuum conditions, heated, cooled to room temperature, filtered to obtain a precipitate, washed and extracted, and then vacuum dried to obtain an imine-linked covalent organic framework material. 3) The imine-linked covalent organic framework material obtained in step 2) is mixed with tetrachlorobenzoquinone, an organic solvent, phenylacetylene, and boron trifluoride-diethyl ether complex, and then homogenized to obtain a mixed solution; 4) The mixed solution obtained in step 3) is heated and reacted under an argon atmosphere, cooled to room temperature, filtered to obtain a precipitate, and the precipitate is washed and extracted to obtain a visible light responsive quinoline bonded covalent organic framework material.

3. The preparation method according to claim 2, characterized in that, In step 1), the molar ratio between 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde, and glacial acetic acid is 1:1.5:15~16; the concentration of the glacial acetic acid aqueous solution is 6 mol / L, and the volume ratio of the glacial acetic acid aqueous solution to the organic solvent is 1:2~5.

4. The preparation method according to claim 2 or 3, characterized in that, In step 1), the organic solvent is a mixture of n-butanol and o-dichlorobenzene in a volume ratio of 1:

1.

5. The preparation method according to claim 2, characterized in that, In step 2), the heating temperature is 110~130℃ and the heating time is 72 h.

6. The preparation method according to claim 2, characterized in that, In step 3), the molar ratio of tetrachlorobenzoquinone, phenylacetylene, and boron trifluoride-ethyl ether complex is 2:3.5~4.5:0.8~1.2; the molar ratio of imine bonds to tetrachlorobenzoquinone in the imine-linked covalent organic framework material is 1:1~2.

7. The preparation method according to claim 2 or 6, characterized in that, In step 3), the organic solvent is toluene, and the molar ratio of toluene to tetrachlorobenzoquinone is 310~320:

1.

8. The preparation method according to claim 2, characterized in that, Step 4), the heating temperature is 100~120 ℃, and the heating time is 72 h.

9. The application of a visible-light-responsive quinoline-linked covalent organic framework material as described in claim 1 in the selective oxidation reaction of thioether compounds, characterized in that, The covalent organic framework material was dispersed in a solution of a thioether compound and subjected to a selective oxidation reaction under visible light irradiation.

10. The application according to claim 9, characterized in that, The sulfide compound is any one of anisole, p-methyl anisole, p-methoxy anisole, p-fluoroanisole, p-chloroanisole, p-bromoanisole, p-iodoanisole, 2-methoxyanisole, 3-methoxyanisole, 3-chloroanisole, cyclohexylmethyl sulfide, and di-n-butyl disulfide.

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