Aza-diene-connected covalent organic framework polymer as well as preparation method and application thereof

Abstract

The invention provides an azadiene-connected covalent organic framework polymer and a preparation method and application thereof, and belongs to the technical field of chemistry and new materials, and the structural formula of the covalent organic framework polymer is shown as a formula I or a formula II. According to the invention, two novel aza-diene coupled COFs (COF-JUL236 and COF-JLU237) with high crystallinity and high specific surface area are successfully synthesized, and by introducing an expanded pi conjugated bond aza-diene structure, not only is the light absorption range of the COF-JLUs widened, but also exciton recombination is effectively inhibited, so that the photocatalytic efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of chemistry and new material technology, and more specifically, to a covalent organic framework polymer connected with an azadiene and a preparation method and application thereof. Background Art

[0002] As a green and sustainable means of chemical transformation, photocatalytic technology has attracted much attention in the fields of organic synthesis, environmental governance and energy conversion in recent years. Its core is to use light energy to excite catalysts to produce highly active species (such as free radicals, hole-electron pairs), drive the target reaction to proceed efficiently, and thus reduce dependence on traditional high temperature, high pressure or precious metal catalysts. However, the development of photocatalytic materials with high catalytic activity, excellent selectivity and good stability remains an important challenge in this field.

[0003] In the field of selective oxidation of organic sulfides, sulfoxide compounds are key intermediates for drug synthesis (such as omeprazole), functional materials and fine chemicals. Traditional methods mainly rely on transition metal catalysts (such as vanadium and molybdenum complexes) or stoichiometric oxidants (such as persulfate and hydrogen peroxide), and there are problems such as metal residue pollution, harsh reaction conditions (strong acid, high temperature) and excessive oxidation to generate sulfone byproducts. In recent years, although heterogeneous photocatalytic systems (such as TiO2 and MOFs) have shown certain potential, they are limited by narrow light absorption range (mainly ultraviolet response), limited substrate mass transfer due to pore structure mismatch, and insufficient exposure of active sites. Their catalytic efficiency and selectivity are still difficult to meet actual needs. For example, some reported TiO2-based catalysts require ultraviolet light excitation, and the selectivity for sulfide to sulfoxide is less than 80%, which seriously restricts their application value. On the other hand, the oxidation reaction of phenylboronic acid compounds is an important way to construct important structures such as phenol and biphenyl ether. Existing methods mostly rely on precious metal catalysts (such as palladium, copper) or strong oxidants (such as m-chloroperbenzoic acid), which have the problems of high cost, poor functional group compatibility and waste disposal. Although photocatalytic oxidation is an ideal alternative, existing catalysts (such as organic dyes, conjugated polymers) generally have bottlenecks such as poor stability (easy photodegradation), low visible light utilization and weak substrate adsorption capacity, resulting in low reaction efficiency (such as conversion rate <50%) or the need to add a co-catalyst (such as triethylamine), which increases the complexity of the process.

[0004] As emerging crystalline porous materials, covalent organic frameworks (COFs) exhibit unique advantages in the field of photocatalysis due to their high specific surface area, adjustable pore size, and well-defined active sites. However, traditional COFs (such as those linked by imine bonds or borate ester bonds) often suffer from insufficient chemical stability (especially in acidic / alkaline media), high recombination rates of photo-generated carriers, and limited visible light response. For example, imine-bonded COFs are prone to bond cleavage under light irradiation, leading to structural collapse; while most COFs have relatively wide bandgaps and can only absorb ultraviolet or blue light, which limits the utilization rate of sunlight. In addition, the selective regulation mechanism of existing COF photocatalysts in complex reaction systems (such as the coexistence of multiple substrates) is not clear, making it difficult to achieve precise synthesis of specific products.

[0005] To address the above problems, this patent innovatively designs a covalent organic framework material based on azadiene bonds. This material connects conjugated units through rigid azadiene linkages, not only significantly enhancing the chemical stability and light absorption performance of the framework (extending to the visible light region), but also enabling selective adsorption and activation of substrates due to its highly ordered pore structure and abundant surface active sites. In the selective oxidation of thioethers, the framework material efficiently inhibits over-oxidation side reactions by regulating the hole oxidation ability and free radical generation pathway; meanwhile, it exhibits broad functional group tolerance in the oxidation reaction of phenylboronic acid, providing a new route for the green synthesis of phenolic compounds without the need for additional oxidants or metal promoters. The realization of this bifunctional catalytic property breaks through the technical bottlenecks of traditional photocatalysts with single applications and harsh conditions, and has important industrial application prospects. Summary of the Invention

[0006] One object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0007] Another object of the present invention is to provide an azadiene-linked covalent organic framework polymer and its preparation method and application. Based on the novel COF material linked by azadiene, it breaks through the performance limits of traditional catalysts by precisely regulating the electronic structure of the framework, the pore microenvironment, and the distribution of active sites, providing an innovative solution for the green and efficient synthesis of phenolic compounds.

[0008] To achieve these and other advantages of the present invention, there is provided an azadiene-linked covalent organic framework polymer, the structural formula of which is shown in Formula I or Formula II;

[0009]

[0010] Preferably, the azadiene-linked covalent organic framework polymer is a crystalline porous structure formed by connecting through extended π-conjugated azadiene (C=N-C=C) bonds; the covalent organic framework polymer has a two-dimensional layered stacking structure, with a specific surface area of 600-652m 2 / g and a pore size of 2.4-2.5 nm.

[0011] The present invention also provides a method for preparing the above-mentioned azadiene-linked covalent organic framework polymer, which includes the following steps: mixing a triazine-based triacrolein monomer and a triamino monomer in a molar ratio of 1:1, dissolving them in a mixed organic solvent and stirring evenly to form a reaction system, adding an acid catalyst to the reaction system, reacting at 100 °C for 3 d, and obtaining the product after centrifugation, washing, and drying; the concentrations of the triazine-based triacrolein monomer and the triamino monomer in the reaction system are both 0.05 mol / L.

[0012] Preferably, in the method, the acid catalyst is an aqueous acetic acid solution with a concentration of 6 M, and the volume of the aqueous acetic acid solution is 10% of the volume of the mixed organic solvent.

[0013] Preferably, in the method, the triazine-based triacrolein monomer is 3,3',3”-((1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))triacrolein (TTTB);

[0014] The triamino monomer is 1,3,5-tris(4-aminophenyl)benzene (TAPB) or 1,3,5-tris(4-aminophenyl)triazine (TAPT).

[0015] Preferably, in the method, the mixed organic solvent is prepared by mixing 1,4-dioxane and mesitylene in a volume ratio of 4:6.

[0016] The present invention also provides an application of the azadiene-linked covalent organic framework polymer as a photocatalyst in organic synthesis reactions, and the organic synthesis reaction is the selective oxidation of arylboronic acid or sulfide.

[0017] Preferably, in the application, the conditions of the organic synthesis reaction are:

[0018] Using oxygen as the oxidant, with an oxygen pressure of 1 atm;

[0019] Using methanol, acetonitrile or water as the solvent;

[0020] Using a visible light source with a wavelength of 460 nm and a power of 30 W generated by an LED lamp as the light source;

[0021] The reaction temperature is room temperature, and the reaction time is 1-15 h;

[0022] The substrate concentration is 0.1 mmol / mL; the ratio of the amount of photocatalyst to the amount of substrate is 5 mg:0.1 mmol;

[0023] In the organic synthesis reaction, an electron donor N,N-diisopropylethylamine (DIPEA) is added, and its dosage is 1-5 times the molar amount of the substrate.

[0024] The present invention has at least the following beneficial effects:

[0025] 1. The present invention constructs a novel aza-diene linked structure - covalent organic framework polymers (COF-JLU236 and COF-JLU237) through the aza-diene (C=N-C=C) bond, improving the material stability and optoelectronic properties; the covalent organic framework polymers (COF-JLU236 and COF-JLU237) constructed by the present invention have a rigid planar skeleton, with good thermal and chemical durability (thermal stability above 430 °C, resistant to acids / alkalis and organic solvents), significantly enhancing the material stability.

[0026] 2. The present invention broadens the light absorption range of the obtained covalent organic framework polymers (COF-JLU236 and COF-JLU237) to 750 nm (band gap 2.32 eV / 2.35 eV) through an extended π-conjugated system, far exceeding that of traditional imine bond COFs (<450 nm), effectively improving the utilization rate of sunlight.

[0027] 3. The COFs prepared by the Schiff base condensation reaction of the present invention have a two-dimensional layered stacking structure, high crystallinity (sharp PXRD peaks, FWHM only 0.48° / 0.62°), specific surface area of 600-652 m 2 / g, pore size of 2.4-2.5 nm, providing an efficient channel for substrate diffusion and adsorption. The characteristics of high crystallinity and ordered porous structure can effectively promote the catalytic reaction efficiency;

[0028] 4. The covalent organic framework polymers prepared by the present invention have excellent photogenerated carrier separation ability, with fast and high transient photocurrent response (the photocurrent density of COF-JLU236 is significantly higher than that of COF-JLU237). Electrochemical impedance spectroscopy (EIS) shows low charge transfer resistance and carrier lifetime up to 2.62 ns, effectively inhibiting electron-hole recombination.

[0029] 5. The covalent organic framework polymer of the present invention can be applied to the efficient catalytic selective oxidation reaction. It has a wide substrate adaptability. The catalytic reaction conditions are under visible light (460 nm LED), with O2 as the oxidant, and it can efficiently catalyze the selective oxidation of sulfides (the yield of the target product is 94 - 97%) and phenylboronic acid (the yield of the target product is 92 - 98%), and it shows excellent activity towards substrates with different substituents (such as -Cl, -Br, -OMe); the catalytic efficiency is significantly better than that of traditional noble metal catalysts (such as palladium complexes) and imine bond COFs (TOF < 20 h -1 ), and it avoids the use of stoichiometric oxidants, meeting the requirements of green chemistry.

[0030] 6. The covalent organic framework polymer of the present invention has good cycle stability and industrial application potential. Especially, after the COF-JLU236 is recycled 5 times, its catalytic activity does not decrease significantly (the yield > 95%), and its structure and morphology remain intact (verified by PXRD, FT-IR and SEM). The large-scale experiment (the dosage of 1a is 1.05 g) still maintains a yield of 97%, showing the prospect of industrial application.

[0031] 7. The pyridine nitrogen site in the aza-diene of the covalent organic framework polymer of the present invention coordinates with the boron atom of the substrate, reducing the reaction activation energy; the photo-generated electrons are directly transferred to O2 to generate superoxide radicals (O2 - ), avoiding the generation of by-products and ensuring high-selectivity oxidation.

[0032] 8. Through the design of COFs materials connected by aza-diene, the present invention solves the core problems of poor stability, narrow spectral response and fast carrier recombination in traditional photocatalytic systems, providing an innovative solution for the efficient and green synthesis of phenolic compounds and sulfur oxides, and having both academic value and industrial application prospects.

[0033] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the synthetic route diagram of the covalent organic framework polymers COF-JLU236 and COF-JLU237 in Example 1 of the present invention;

[0035] Figure 2 It is the Fourier transform infrared spectrogram of the covalent organic framework polymers COF-JLU236 and COF-JLU237 in Example 1 of the present invention;

[0036] Figure 3Solid-state 13C CP-MAS NMR spectra and structural formulas of covalent organic framework polymers COF-JLU236 and COF-JLU237 in Example 1 of the present invention;

[0037] Figure 4 Powder X-ray diffraction (PXRD) patterns of covalent organic framework polymers COF-JLU236 and COF-JLU237 in Example 1 of the present invention. Among them, (a) and (b) are the powder X-ray diffraction (PXRD) patterns of COF-JLU236 and COF-JLU237 respectively. The experimental curve is red, the Pawley refinement curve is black, the simulated curve is sky blue, the difference between the experimental and refined PXRD patterns is green, and the observed reflections are blue; (c) and (e) are the top views of COF-JLU236 and COF-JLU237 respectively, showing the overlapping (AA) structure; (d) and (f) are the side views of COF-JLU236 and COF-JLU237 respectively;

[0038] Figure 5 Results display of the PXRD pattern of COF-JLU236 in Example 1 of the present invention. Among them, (a) is the PXRD pattern of COF-JLU236. The experimental curve is black, the AA stacking model is red, the AB stacking model is blue, and the ABC stacking model is purple. The structural diagrams of COF-JLU236 simulated by the stacking modes in the unit cell are shown through (b) AA, (c) AB, and (d) ABC respectively;

[0039] Figure 6 Results display of the PXRD pattern of COF-JLU237 in Example 1 of the present invention. Among them, (a) is the PXRD pattern of COF-JLU237. The experimental curve is black, the AA stacking model is red, the AB stacking model is blue, and the ABC stacking model is purple. The structure of COF-JLU237 simulated by the (b) AA, (c) AB, and (d) ABC stacking modes in the unit cell;

[0040] Figure 7 Powder X-ray diffraction (PXRD) patterns of covalent organic framework polymers COF-JLU236 and COF-JLU237 in Example 1 of the present invention. (a) is the powder X-ray diffraction (PXRD) pattern of COF-JLU236 (full width at half maximum FWHM = 2 × 0.24° = 0.48°); (b) is the powder X-ray diffraction (PXRD) pattern of COF-JLU237 (full width at half maximum FWHM = 2 × 0.31° = 0.62°);

[0041] Figure 8These are the field emission scanning electron microscope images of covalent organic framework polymers COF-JLU236 and COF-JLU237 in Example 1 of the present invention, where Figure 8 a corresponds to COF-JLU236, Figure 8 b corresponds to COF-JLU237;

[0042] Figure 9 These are the N2 adsorption (solid circles) and desorption (hollow circles) isotherms of covalent organic framework polymers COF-JLU236( Figure 9 a) and COF-JLU237( Figure 9 b) in Example 1 of the present invention;

[0043] Figure 10 These are the pore size distribution diagrams of covalent organic framework polymers COF-JLU236( Figure 10 a) and COF-JLU237( Figure 10 b) in Example 1 of the present invention;

[0044] Figure 11 These are the thermogravimetric curves of covalent organic framework polymers COF-JLU236 (purple line) and COF-JLU237 (green line) in a nitrogen atmosphere in Example 1 of the present invention;

[0045] Figure 12 These are the PXRD curves of covalent organic framework polymers COF-JLU236( Figure 12 a) and COF-JLU237( Figure 12 b) after being treated under different conditions for 3 days in Example 1 of the present invention;

[0046] Figure 13 These are the FT-IR spectra of covalent organic framework polymers COF-JLU236( Figure 13 a) and COF-JLU237( Figure 13 b) after being treated under different conditions for 3 days in Example 1 of the present invention;

[0047] Figure 14 (a) is the ultraviolet / visible diffuse reflectance spectrum curve of COF-JLUs; Figure 14 (b) is the Tauc plot of COF-JLUs, Figure 14 (c) is the schematic diagram of the energy band structure of COF-JLU236 and COF-JLU237. Figure 14 (d) is the calculated energy band structure and density of states of COF-JLU236. Figure 14 (e) is the calculated distribution of the lowest unoccupied molecular orbital (LOMO) and the highest occupied molecular orbital (HOMO) of the periodic unit of COF-JLU236. Figure 14(f) is the photocatalytic efficiency performance of COF-JLU236 in five consecutive cycles of photocatalytic oxidation of sulfide. Figure 14 (g) is the electron paramagnetic resonance (EPR) conduction band electron spectrum of COF-JLU236 in the dark and under visible light irradiation. Figure 14 (h) is the ultraviolet / visible absorption spectrum and photo of the TMPD cation generated by COF-JLU236 in the presence of light and oxygen. Figure 14 (i) is the transient current density of COF-JLUs. Figure 14 (j) is the electrochemical impedance spectroscopy (EIS) of COF-JLUs. Figure 14 (k) is the photoluminescence decay curve of COF-JLUs;

[0048] Figure 15 (a) is the ultraviolet / visible diffuse reflection spectral curve of COF-JLU20 and COF-JLU236, Figure 15 (b) is the chemical structure diagram and product physical diagram of COF-JLU20; Figure 15 (c) is the chemical structure diagram and product physical diagram of COF-JLU236; Figure 15 (d) is the ultraviolet / visible diffuse reflection spectral curve of COF-JLU16 and COF-JLU237, Figure 15 (e) is the chemical structure diagram and product physical diagram of COF-JLU16; Figure 15 (f) is the chemical structure diagram and product physical diagram of COF-JLU237;

[0049] Figure 16 is for COF-JLU236 ( Figure 16 a) and COF-JLU237 ( Figure 16 b) Mott-Schottky curve diagram;

[0050] Figure 17 is the calculated band structure and density of states diagram of COF-JLU237 ( Figure 17 a), the calculated lowest unoccupied molecular orbital (LOMO) and highest occupied molecular orbital (HOMO) distribution diagrams of the periodic unit of COF-JLU237 ( Figure 17 b);

[0051] Figure 18 is the Fourier transform infrared spectrum of COF-JLU236 before and after five consecutive cycles of photocatalytic oxidation of sulfide Figure 18 a); the powder X-ray diffraction spectrum of COF-JLU236 before and after five consecutive cycles of photocatalytic oxidation of sulfide Figure 18b); Field emission scanning electron microscope images of COF-JLU236 before and after five consecutive cycles of sulfide photooxidation( Figure 18 c);

[0052] Figure 19 Figure showing the leaching test results of COF-JUL236 for sulfide photooxidation;

[0053] Figure 20 Figure showing the electron spin resonance spectra of COF-JLU236 in the dark and under visible light irradiation, using TEMP as a spin trap agent for singlet oxygen( 1 O2);

[0054] Figure 21 Figure for the analysis of the photocatalytic mechanism of COF-JUL236 for photocatalytic oxidation of sulfide;

[0055] Figure 22 Figure showing the performance results of COF-JLU236 in five consecutive cycles of photocatalytic efficiency for photocatalytic oxidation of arylboronic acid;

[0056] Figure 23 Figure for the photocatalytic mechanism of COF-JUL236 for photocatalytic oxidation of arylboronic acid;

[0057] Figure 24 1H NMR spectrum of TTTB 1 H spectrum;

[0058] Figure 25 13C NMR spectrum of TTTB 13 C spectrum;

[0059] Figure 26 1H NMR spectrum of TAPB 1 H spectrum;

[0060] Figure 27 1H NMR spectrum of TAPT 1 H spectrum. Detailed implementation manners

[0061] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, so that those skilled in the art can implement it according to the description in the specification.

[0062] It should be understood that the terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0063] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0064] Characterization methods involved in the present invention:

[0065] Nuclear magnetic resonance spectroscopy (NMR): Liquid NMR was measured using an Avance III-400 spectrometer, and the chemical shift (δ, ppm) was referenced to TMS as an internal standard. Solid-state 13 13C CP / MAS NMR was performed using a Bruker AVANCE III 400WB spectrometer.

[0066] Powder X-ray diffraction (PXRD): Measured using a PANalytical BV Empyrean diffractometer in the 2θ range of 1.5 - 40° at room temperature.

[0067] Fourier transform infrared spectroscopy (FT-IR): Using the KBr pellet method, tested in the range of 4000 - 400 cm-1 through a TENSOR 27 spectrometer (Bruker). 1 Range.

[0068] Solid ultraviolet-visible spectroscopy (UV / Vis DRS): Measured in the range of 200 - 800 nm using a Shimadzu U-4100 spectrophotometer.

[0069] Nitrogen adsorption-desorption: Specific surface area and pore volume were calculated by the BET method (ASAP 2020 analyzer). Sample pretreatment: Dried in vacuum at 80 °C for 10 hours. Pore size distribution was calculated by non-local density functional theory (NLDFT).

[0070] Field emission scanning electron microscopy (FE-SEM): Images were taken using a HITACHI UHR FE-SEM SU8000.

[0071] Thermogravimetric analysis (TGA): Using a TA Q500 thermogravimetric balance, heated to 800 °C at a rate of 20 °C / min under N2 atmosphere.

[0072] Electron paramagnetic resonance (EPR): Measured using a JES-FA 200 spectrometer under illumination with a 30 W OLED light source.

[0073] Photoluminescence spectroscopy (PL): Measured using an FLS920 Edinburgh instrument.

[0074] Photoelectrochemical tests: Using a CHI760E workstation, a three-electrode system (GCE working electrode, Ag / AgCl reference electrode, Pt counter electrode). Mott-Schottky analysis: 5 mg of catalyst + 20 μL of 5 wt% Nafion were dispersed in 980 μL of ethanol, sonicated, and then drop-coated onto the GCE, with a 0.1 M Na2SO4 electrolyte.

[0075] Photocurrent test: 300W xenon lamp (CEAULIGHT CEL-HXF300), 50-second on-off cycle.

[0076] Electrochemical impedance spectroscopy (EIS): 5 mg catalyst + 50 μL of 1.5 wt% PVDF NMP solution dispersed in 225 μL of water / ethanol mixture, drop-coated on GCE, 0.1 M KCl + 5 mM [Fe(CN)6] 3 - / 4 - electrolyte.

[0077] Potential conversion formula: ENHE = EAg / AgCl + 0.20 V (1) ERHE = EAg / AgCl + 0.0591·pH + 0.20 V (2)

[0078] Structure modeling: Pawley refinement was performed using Materials Studio 2020 software. The space group was obtained from the Reticular Chemistry Structure Resource. The structure was optimized using the Forcite module, and the PXRD data was fitted using the Reflex module.

[0079] DFT calculation: Gaussian 16B.01 program, M06-2X functional, 6-311G(d,p) basis set was used to describe C / H / N atoms.

[0080] Reagents: 4-bromobenzonitrile, acrolein diethyl acetal (Heowns); trifluoromethanesulfonic acid (Tansoole); solvents (Tianjin Yongda Chemical Reagents) were dried and distilled under nitrogen protection. Deuterated reagents (Energy Chemical).

[0081] <Example 1>

[0082] I. Preparation of aza-diene-linked covalent organic framework polymer (synthetic route as shown Figure 1 below)

[0083] 1.1. Synthesis of triazine-based triacrolein monomer - 3,3',3”-((1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))triacrolein (TTTB), and its synthetic route is as follows;

[0084]

[0085] The synthesis steps of TTTB include:

[0086] S11. Add 10 mL of trifluoromethanesulfonic acid to a 25 mL round-bottom flask at 0 °C. Subsequently, slowly drip a CHCl3 solution of 4-bromobenzonitrile (5.1 g, 30 mmol) into the flask, stir overnight, then pour the reaction solution into 50 mL of water, adjust to neutral with 2N (2 mol / L) NaOH, then extract with CH2Cl2, and evaporate to dryness under reduced pressure to obtain a white solid, 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (4.6 g, yield: 91%);

[0087] S12. Mix 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (0.546 g, 1 mmol), tert-butylammonium acetate (0.462 g, 6 mmol), K2CO3 (0.621 g, 4.5 mmol), Pd(OAc)2 (20 mg, 0.09 mmol), and KCl (0.223 g, 3 mmol). Subsequently, add 8 mL of anhydrous DMF and acrolein diethyl acetal (1.37 mL, 9 mmol), stir evenly, then freeze-pump-vacuum three times, and reflux for 12 hours under nitrogen protection. After cooling, add 10 mL of 2N (2 mol / L) HCl and stir for 30 minutes, extract with dichloromethane, and perform column chromatography to obtain a pale yellow solid (153 mg, yield: 32%), which is 3,3',3”-((1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))triacrolein (TTTB), with the molecular formula C 30 H 21 N3O3.

[0088] The nuclear magnetic resonance (NMR) results of 3,3',3”-((1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))triacrolein (TTTB) 1 The 1H spectrum is as Figure 24 shown, 13 The 13C spectrum is as Figure 25 shown) are as follows:

[0089] 1 1H NMR (400 MHz, CDCl3): δ 9.79 (d, J = 7.5 Hz, 3H), 8.82 (d, J = 13.0 Hz, 6H), 7.78 (d, J = 8.0 Hz, 6H), 7.59 (d, J = 15.9 Hz, 3H), 6.86 (dd, J = 15.9, 7.5 Hz, 3H).

[0090] 13 13C NMR (100 MHz, CDCl3): δ 193.40, 170.86, 151.14, 138.07, 138.02, 130.07, 129.58, 128.68.

[0091] 1.2 Synthesis of 1,3,5-tris(4-aminophenyl)benzene (TAPB), and the synthesis route is as follows;

[0092]

[0093] The synthesis of 1,3,5-tris(4-aminophenyl)benzene (TAPB) includes the following steps:

[0094] S2.1 Add 1,3,5-tribromobenzene (200 mg, 0.64 mmol), 4-aminophenylboronic acid pinacol ester (627 mg, 2.86 mmol), Pd(PPh3)4 (40 mg, 0.045 mmol), K2CO3 (705 mg, 5.1 mmol) and 20 mL of anhydrous dioxane into a 250 mL round-bottom flask. After degassing three times, react at 120 °C for 36 hours under nitrogen protection;

[0095] S2.2 After the reaction is completed, quench with an ice bath, filter, and obtain a grayish-white solid (178 mg, yield: 80%) by column chromatography, namely 1,3,5-tris(4-aminophenyl)benzene (TAPB), with the molecular formula C 24 H 21 N3.

[0096] The results of the hydrogen spectrum of the nuclear magnetic resonance spectrum (NMR) of 1,3,5-tris(4-aminophenyl)benzene (TAPB) (the spectrum is as Figure 26 shown) are as follows: 1 H NMR (400 MHz, CDCl3): δ 7.60 (s, 3H), 7.50 (d, J = 8.3 Hz, 6H), 6.78 (d, J = 8.3 Hz, 6H), 3.74 (s, 6H).

[0097] 1.3 Synthesis of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT), and the synthesis route is as follows;

[0098]

[0099] The synthesis steps of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) are as follows: Add 3 mL of trifluoromethanesulfonic acid to a 25 mL round-bottom flask in an ice bath at 0 °C, and slowly add 4-aminobenzonitrile (0.96 g, 8.17 mmol) to the round-bottom flask. Stir overnight, pour the reaction solution into 50 mL of water, and adjust to neutral with 2N (2 mol / L) NaOH. Filter by suction, wash with distilled water and methanol to obtain a pale yellow solid (0.78 mg, yield: 82%), namely 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT), with the molecular formula C 21 H 18N6。

[0100] The proton nuclear magnetic resonance (NMR) spectrum of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) (the spectrum is as shown in Figure 27 the figure) shows the following results: 1 HNMR(400MHz,DMSO-d6):δ8.36(d,J=8.4Hz,6H),6.70(d,J=8.4Hz,6H),5.93(s,6H).

[0101] 1.4. Synthesis of covalent organic framework polymer COF-JLU236. The synthesis route is as follows:

[0102]

[0103] The synthesis steps of covalent organic framework polymer COF-JLU236 are as follows: Add TTTB (23 mg, 0.05 mmol) and TAPB (17 mg, 0.05 mmol) into a 2 mL Pyrex tube. Add 0.6 mL of mesitylene, 0.4 mL of dioxane, and 0.1 mL of 6 M acetic acid solution into the Pyrex tube, and disperse by ultrasonic wave. After three times of vacuum degassing, seal with a flame. React at a constant temperature of 100 °C for 3 days, then centrifuge and filter the product, wash it with tetrahydrofuran, and dry it in vacuum at 60 °C for 6 hours to obtain a yellow powder (yield 97%), that is, covalent organic framework polymer COF-JLU236, with the molecular formula C 96 H 54 N 12 。

[0104] 1.5. Synthesis of covalent organic framework polymer COF-JLU237. The synthesis route is as follows:

[0105]

[0106] The synthesis steps of covalent organic framework polymer COF-JLU237 are as follows: Add TTTB (23 mg, 0.05 mmol) and TAPT (18 mg, 0.05 mmol) into a 2 mL Pyrex tube. Add 0.6 mL of mesitylene, 0.4 mL of dioxane, and 0.1 mL of 6 M acetic acid solution into the Pyrex tube, and disperse by ultrasonic wave. After three times of vacuum degassing, seal with a flame. React at a constant temperature of 100 °C for 3 days, then filter the product, wash it with tetrahydrofuran, and dry it in vacuum at 60 °C for 6 hours to obtain a light yellow powder (yield 91%), that is, covalent organic framework polymer COF-JLU237, with the molecular formula C 93 H 42 N 15 。

[0107] II. Characterization of Covalent Organic Framework Polymers COF-JLU236 and COF-JLU237

[0108] 2.1 Fourier Transform Infrared Spectroscopy

[0109] As Figure 2 shown, the infrared spectra of COF-JLU236 and COF-JLU237 show that extremely obvious strong characteristic peaks appear at 1604 cm -1 and 1609 cm -1 . After analysis, this peak can be clearly attributed to the C=N bond, which strongly proves the successful formation of the azadiene linkage; further comparison of the polymer spectrum with the monomer spectrum reveals that the characteristic peaks originally present in the aldehyde group and amino group almost completely disappear in the polymer spectrum. This result fully indicates that during the synthesis of COF-JLU236 and COF-JLU237, a high degree of polycondensation reaction occurs, causing a large number of aldehyde groups and amino groups to participate in the reaction, resulting in a significant weakening and even disappearance of their characteristic peaks. This not only reveals the chemical bonding changes within the material but also provides an important basis for in-depth understanding of its structure and properties.

[0110] 2.2 Solid-State 13 13C CP / MAS Nuclear Magnetic Resonance Characterization

[0111] As Figure 3 shown, Figure 3 a shows the solid-state 13C CP-MAS NMR spectrum of COF-JLU236 and its chemical structure diagram, Figure 3 b presents the solid-state 13C CP-MAS NMR spectrum of COF-JLU237 and its chemical structure diagram. Through the molecular-level analysis by 13C CP / MAS NMR, it is further firmly confirmed that the covalent organic framework polymer with azadiene linkage has been successfully prepared in the present invention. In the spectrum of COF-JLU236, the peak at about 150.7 ppm can be attributed to the carbon atom in the newly formed C=N group, while the low-field signal at about 170.0 ppm corresponds to the triazine ring (see Figure 3 a). Similarly, the spectrum of COF-JLU237 shows two characteristic signals at 170.3 ppm and 148.5 ppm (see Figure 3b). Specifically, the carbon signals of the C═C groups in COF-JLU236 appear at approximately 136.3 ppm and 113.8 ppm, respectively; in COF-JLU237, the carbon signals of this group are located at approximately 137.3 ppm and 115.2 ppm, respectively. In addition, the other peaks in the spectra can be attributed to the vibrations of unsubstituted and substituted aromatic carbons. The presence and attribution of these characteristic peaks provide crucial molecular-level evidence for a deeper understanding of the chemical structures of COF-JLU236 and COF-JLU237, strongly supporting the structural characteristics of the materials prepared in this invention.

[0112] 2.3, Powder X-ray Diffraction (PXRD)

[0113] In the process of exploring the crystal structures of covalent organic framework polymers COF-JLU236 and COF-JLU237, key information was obtained by using powder X-ray diffraction (PXRD) technology in combination with structure simulation methods. The specific results are as Figures 4 - 7 shown. As can be seen from the PXRD pattern of COF-JLU236 in Figure 4 a, it shows an obvious main peak at 3.54°, and weak peaks appear at 6.21°, 7.03° and 9.46°. These peaks correspond to the diffractions of the (100), (110), (200) and (210) crystal planes, respectively. In addition, there is a broad peak at approximately 25.4°, which is caused by the π-π stacking interaction between the layers of COF-JLU236 and belongs to the (001) plane. By simulating different stacking modes, it was found that the simulated curve of the AA stacking mode (sky blue line) highly coincides with the experimental data in terms of signal position and intensity ( Figure 4 a), while the simulated curves of the AB and ABC stacking modes deviate significantly from the experimental spectra ( Figure 5 ). Looking at the PXRD pattern of COF-JLU237 ( Figure 4 b), characteristic signals appear at 3.52°, 6.01° and 9.21°. The simulation results show that its crystal structure also conforms to the AA stacking mode (sky blue line, Figure 6 ). Further analysis of the experimental curves by Pawley refinement (the green lines in Figure 4 a, b) gives Rwp = 6.40% and Rp = 4.48% for COF-JLU236; Rwp = 6.91% and Rp = 5.27% for COF-JLU237, indicating that the simulation results match the experimental data well. In addition, from Figure 7From the full width at half maximum (FWHM) data of COF-JLU236 and COF-JLU237, the FWHM of COF-JLU236 is 0.48° (2×0.24°), and the FWHM of COF-JLU237 is 0.62° (2×0.31°). Combining the above PXRD analysis results fully indicates that the covalent organic framework polymers COF-JLU236 and COF-JLU237 synthesized in this invention have a highly ordered crystal structure and exhibit strong crystallinity.

[0114] 2.4, Field Emission Scanning Electron Microscope

[0115] As Figure 8 shown, the microtopography of the covalent organic framework polymers COF-JLU236 ( Figure 8 a) and COF-JLU237 ( Figure 8 b) was characterized by field emission scanning electron microscope (FE-SEM). The results show that both materials exhibit a highly uniform nanosheet structure with a flat surface and no obvious agglomeration. No other heterophase particles were observed in the FE-SEM images, indicating that COF-JLU236 and COF-JLU237 have good phase purity and structural uniformity, which lays a solid foundation for providing stable active sites in photocatalytic reactions.

[0116] 2.5, Adsorption-Desorption Experiment

[0117] The N2 adsorption-desorption experiment was carried out at 77K to systematically evaluate the pore structure characteristics of nitrogen heterodiene-linked covalent organic frameworks (COFs). As Figure 9 shown, the adsorption-desorption curves of COF-JLU236 ( Figure 9 a) and COF-JLU237 ( Figure 9 b) both exhibit typical type IV isotherm characteristics, and a sharp rise appears in the low pressure region where the relative pressure P / P0 < 0.01, indicating that the material has a rich microporous structure. When P / P0 is between 0.4 - 0.95, an obvious H3-type hysteresis loop appears, which is a typical characteristic of mesoporous materials, confirming the presence of a one-dimensional open channel structure in the material.

[0118] 2.6, Specific Surface Area and Pore Size Distribution

[0119] As Figure 10 shown, calculated by the Brunauer-Emmett-Teller (BET) method, the specific surface areas of COF-JLU236 and COF-JLU237 are 652 m 2 / g and 608 m 2 / g respectively.

[0120] Aperture distribution analysis based on non-local density functional theory (NLDFT) showed that both materials formed highly ordered mesoporous structures. The average pore diameter of COF-JLU236 was 2.46 nm, and that of COF-JLU237 was 2.42 nm( Figure 10 ). Notably, COF-JLU237 exhibited a higher adsorption capacity when P / P0 was close to 1, with a total pore volume of 0.43 cm 3 / g, higher than 0.38 cm 3 / g of COF-JLU236. This was attributed to the higher structural openness conferred by its unique triazine ring structural unit. The above results were highly consistent with the AA stacking mode revealed by powder X-ray diffraction (PXRD) analysis, further confirming the periodically arranged one-dimensional channel structure in the materials. This hierarchical pore system provided an ideal channel for substrate diffusion and charge transport in photocatalytic reactions, which was an important structural basis for its excellent catalytic performance.

[0121] 2.7. Thermogravimetric analysis (TGA)

[0122] As Figure 11 shown, the thermal stabilities of COF-JLU236 and COF-JLU237 were systematically studied using thermogravimetric analysis (TGA) technology. Under a nitrogen atmosphere, the temperature was raised from room temperature to 800 °C at a heating rate of 20 °C / min, and both materials showed excellent thermal stabilities. The initial decomposition temperature of COF-JLU236 (purple line) was 430 °C, with a weight loss of about 15% at 500 °C and a total weight loss rate of 32% at 800 °C; the initial decomposition temperature of COF-JLU237 (green line) was as high as 510 °C, with only an 8% weight loss before 600 °C and a total weight loss rate of 28% at 800 °C.

[0123] Notably, the thermal stability of COF-JLU237 was significantly better than that of COF-JLU236, which was attributed to the higher bond energy of the conjugated system formed by the triazine ring unit and the benzene ring in its structure. When the temperature exceeded the initial decomposition temperature, both materials showed a slow weight loss trend, indicating the gradual degradation process of their backbone structures. The gentle weight loss stage of the TGA curve at 500 - 800 °C corresponded to the carbonization process of the organic framework, and this characteristic further verified the structural integrity of the materials under high-temperature conditions. This result was highly consistent with the characterization results of Fourier transform infrared spectroscopy( Figure 13 ) and powder X-ray diffraction( Figure 12 ), confirming that the materials could still maintain the integrity of their backbone structures at high temperatures. This excellent thermal stability provided a solid foundation for its practical application in photocatalytic reactions, especially showing significant advantages in catalytic systems that required high-temperature pretreatment or long-term stability.

[0124] 2.8. Chemical stability

[0125] To evaluate the chemical stability of the materials, solvent tolerance tests were systematically carried out. COF-JLU236 and COF-JLU237 were respectively placed in methanol, tetrahydrofuran, water, 6 M hydrochloric acid, and 6 M sodium hydroxide solution, and after continuously soaking at room temperature for 72 hours, structural characterization was carried out by powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FT-IR)( Figures 12 - 13 ).

[0126] PXRD analysis showed ( Figure 12 a,b) that after treatment with different solvents, the diffraction peak position of the (100) crystal plane of COF-JLU236 remained at 3.54°, and the peak intensity retention rate was above 90%; the diffraction peak of the (100) crystal plane of COF-JLU237 was still located at 3.52°, without obvious shift or intensity attenuation. In the FT-IR spectra ( Figure 13 a,b), the characteristic peak of the C=N bond at 1604 cm -1 was completely retained, and no reappearance of residual peaks of precursors such as aldehyde groups (1720 cm -1 ) or amino groups (3400 cm -1 ) was observed, indicating that the framework structure of the material remained intact.

[0127] It is particularly noteworthy that after treatment under strong acidic (6 M HCl) and strong basic (6 M NaOH) conditions, the material can still maintain an ordered crystalline structure. This excellent chemical stability is attributed to the electron delocalization effect provided by the conjugated system formed by triazine rings and benzene rings, as well as the chemical inertness of imine bonds in an acid / base environment. Compared with the reported COF materials of the same type, the COF-JLU236 and COF-JLU237 prepared in this invention show a wider pH tolerance, and the structural integrity retention rate is increased by about 15 - 20%.

[0128] This result is complementary to the results of thermogravimetric analysis (TGA)( Figure 11 ), jointly verifying the structural stability of the material under harsh conditions such as high temperature, acid, and base. This excellent chemical stability provides an important guarantee for its long-term recycling in complex reaction systems, especially having significant advantages in photocatalytic processes involving corrosive media.

[0129] 2.9, Ultraviolet-visible diffuse reflectance spectroscopy

[0130] The ultraviolet-visible diffuse reflectance spectra (UV-DRS) of COF-JLUs materials show a broad light absorption range extending to 750 nm, which is consistent with their colors. Specifically as Figure 14 shown in a. It is noteworthy that the absorption range of azadiene-linked COFs is wider than that of the corresponding imine-linked COFs, specifically asFigure 15 As shown Figure 15 a is the UV / Vis diffuse reflectance spectra curves of COF-JLU20 and COF-JLU236; Figure 15 b is the chemical structure of COF-JLU20, and the inset is the corresponding physical picture. Figure 15 c is the chemical structure of COF-JLU236, and the inset is the corresponding physical picture. Figure 15 d is the UV / Vis diffuse reflectance spectra curves of COF-JLU16 and COF-JLU237, Figure 15 e is the chemical structure of COF-JLU16, and the inset is the corresponding physical picture. Figure 15 f is the chemical structure of COF-JLU237, and the inset is the corresponding physical picture; Based on the Tauc plot analysis, the optical band gap (Eg) of COF-JLU236 is calculated to be 2.32 electron volts, and the optical band gap of COF-JLU237 is 2.35 electron volts, as specifically shown Figure 14 in b.

[0131] 2.10. Electrochemical detection

[0132] For the two materials of COF-JLU236 and COF-JLU237, the energy level characteristics were deeply explored by using the electrochemical Mott-Schottky measurement method. Through precise measurement and calculation, as Figure 16 shown, the measured value of the conduction band minimum (CBM) potential of COF-JLU236 is -1.45 V (using Ag / AgCl as the reference electrode), while the conduction band minimum potential of COF-JLU237 is -1.02 V (also relative to Ag / AgCl). At the same time, according to the basic formula of the energy band structure Eg = EVBM - ECBM, the valence band maximum (VBM) potential of the two materials was reasonably estimated. The results show that the valence band maximum potential of COF-JLU236 is 1.07 V, and the valence band maximum potential of COF-JLU237 reaches 1.53 V. The specific energy band structure arrangement can be referred to Figure 14 in c. Further, the density functional theory (DFT) calculation method was used to systematically analyze these two materials. The results of the projected density of states analysis clearly show that the electrons in the materials mainly come from carbon atoms and nitrogen atoms. It is particularly worth noting that the band gap width of COF-JLU236 is only 0.078 eV (see details in Figure 14 d), which is significantly lower than 0.085 eV of COF-JLU237( Figure 17 a). The narrower band gap indicates that COF-JLU236 has higher efficiency in the electron transfer process, and this conclusion is highly consistent with the theoretical expectation of the molecular orbital contribution. From the molecular orbital level, as Figure 14As shown in e, the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of COF-JLU236 are mainly concentrated on the acceptor TTTB and the donor TAPB. This distribution pattern is conducive to the effective separation and transport of charges. In sharp contrast, the separation effect of the LUMO and HOMO of COF-JLU237 is poor ( Figure 17 b), which greatly limits its charge separation ability and thus has an adverse effect on the overall optoelectronic properties of the material.

[0133] <Example 2>

[0134] Photocatalytic oxidation of sulfides is shown by the following chemical reaction equations:

[0135]

[0136] Table 1 Optimization of photocatalytic conditions for the selective oxidation of thioanisole by covalent organic framework polymers [a]

[0137]

[0138]

[0139] In Table 1, [a] Reaction conditions: under photocatalyst (5.0 mg), 1a (0.1 mmol), solvent (1.0 mL), O2 (1 atm), room temperature and blue light irradiation (460 nm, 30 W LED lamp). [b] Isolated yield. [c] In the dark. [d] In air. [e] In an argon atmosphere. [f] TEMPO as a radical scavenger. [g] NaN3 as a singlet oxygen scavenger. [h] BQ as a superoxide scavenger.

[0140] In this example, the photocatalytic oxidation of sulfides was selected as an example to evaluate the reactions of the photocatalytic performance of two azadiene-linked COFs (COF-JLU236, COF-JLU237). Specifically, in the reaction with thioanisole (1a) as the substrate and O2 as the green oxidant, the effect of the solvent on the yield was studied. As shown in Table 1, at room temperature, under blue light irradiation (460 nm, 30 W LED lamp), the yields obtained by COF-JLU236 in N,N-dimethylformamide (DMF, 19%), water (75%) and acetonitrile (CH3CN, 87%) were relatively low (Table 1, entries 1-3). In sharp contrast, almost quantitative yields of methyl phenyl sulfoxide (2a) could be obtained in methanol (MeOH) (Table 1, entry 4), which was higher than that of the monomer-based catalytic system (Table 1, entries 5 and 6). It is worth mentioning that although the two COFs have similar absorption bands, when COF-JLU237 was used as the photocatalyst, only low yields were obtained under the same conditions (Table 1, entry 7). In addition, control experiments showed that the excitation light, photocatalyst and O2 were all essential for the reaction process (Table 1, entries 8-11).

[0141] The two COF-JLUs have high crystallinity, intrinsic porosity, strong absorption in the visible light range and suitable energy levels, which prompt this application to explore their solid photocatalytic performance. As is well known, sulfoxides play a crucial role as bioactive substances in the pharmaceutical industry and as intermediates in organic synthesis. Preparing sulfoxides by photocatalytic oxidation of sulfides is an atom-economical and efficient strategy.

[0142] <Example 3>

[0143] The photocatalytic selective oxidation of sulfides to sulfoxides is shown by the following chemical reaction formula;

[0144]

[0145] Table 2 Time and Yield Statistics for the Photocatalytic Selective Oxidation of Sulfides to Sulfoxides [a]

[0146]

[0147] In Table 2, [a] Reaction conditions: photocatalyst (5.0 mg), substrate (0.1 mmol), solvent (1.0 mL), oxygen (1 atm), room temperature and blue light irradiation (460 nm, 30 W LED lamp). [b] Isolated yield.

[0148] To study the universality of the photocatalytic oxidation system, a series of organic sulfides with different substituents were investigated in this example. As shown in Table 2, COF-JLU236 can efficiently and highly selectively induce the conversion of various sulfides to sulfoxides. However, these reactions are affected by the electronic and steric factors of the substituents on the sulfides. For example, the reaction rate of benzyl methyl sulfide with electron-withdrawing groups (such as -Cl and -Br) is lower than that of benzyl methyl sulfide with electron-donating groups (Table 2, entries 5 and 6). Similarly, the electronic effect was also observed in the previously reported photocatalytic sulfoxidation reactions. In addition, a recycling experiment was further carried out in the model reaction using COF-JLU236 as the photoinitiator. COF-JLU236 can be conveniently recovered from the photocatalytic system by centrifugation, washed and dried for use in the next reaction. It was found that COF-JLU236 can be continuously recycled at least five times without obvious loss of photocatalytic efficiency( Figure 14 f). It is worth noting that the recycled COF sample well retains the original linkage and morphology as specifically shown in Figure 18 . In particular, due to the good durability of the COF material, it also has high crystallinity. Subsequently, after 2 hours of photocatalytic reaction, COF-JLU236 was filtered out from the mixture, and the separated solution had no further activity, as shown in Figure 19 , which indicates the heterogeneous nature of the photocatalytic system.

[0149] <Example 4>

[0150] Large-scale photocatalysis of COF-JLU236 (as shown in the following chemical reaction formula) was carried out with 1a (1.05 g, 8.45 mmol) as the substrate in 5.0 mL of methanol at room temperature

[0151]

[0152] To study the photocatalytic mechanism, a series of control experiments were carried out in this example. Under standard conditions, 2,2,6,6-tetraethylpiperidine-1-oxyl (TEMPO) was added as a radical scavenger to the photocatalytic system, and a lower yield of 2a (23%) was obtained (Table 1, entry 15). By adding sodium azide (NaN3), a singlet oxygen( 1 O2) scavenger, a decrease in the product yield was observed (Table 1, entry 16). On the contrary, when p-benzoquinone (BQ) was injected as a superoxide radical anion (O2 ·- ), the yield of 2a dropped sharply to 16% (Table 1, entry 17). Therefore, it can be speculated that 1 O2 and O2 ·- are two important intermediates in this catalytic process, and O2 ·- plays a more crucial role compared to 1 O2.

[0153] This example achieved a high yield of 97%, indicating that the photocatalytic effect of COF-JLU236 on 1a has great potential in industrial synthesis.

[0154] <Example 5>

[0155] Mechanism study

[0156] Furthermore, electron paramagnetic resonance (EPR) experiments were conducted, in which 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and 2,2,6,6-tetramethylpiperidine (TMP) were used as spin-trapping agents for O2 ·- and 1 O2, respectively. Characteristic peaks corresponding to O2 ·- were observed under light illumination, as Figure 14 shown by g. In the case of 1 O2, the corresponding signal was not detected as Figure 20 shown, which is consistent with the experimental results obtained above (Table 1, entries 16 and 17). In addition, due to the electron transfer from N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) to O2, COF-JL236 can effectively accelerate the formation of O2 and blue cation radicals under light illumination ( Figure 14 h). Based on the above results, a reasonable process for the photocatalytic selective sulfur oxidation of O2 by COF-JLU236 is shown in Figure 21. Under light illumination, the possible reaction pathway is proposed as Figure 21 follows: COF-JLU236 is activated to form an excited state, resulting in the simultaneous generation of photogenerated electrons (e - ) and holes (h + ). Subsequently, the photogenerated electrons (e-) can activate O2 to form O2· - and 1 O2 through single-electron transfer or energy transfer processes, respectively. On the one hand, the photogenerated h + transfers to 1a, generating a sulfur-centered radical cation intermediate A. Then, O2· - attacks intermediate A through its nucleophilic property to obtain a peroxymethanesulfinyl intermediate B. On the other hand, intermediate B is still generated through the reaction between 1 O2 and 1a. Finally, B reacts with methanol to form the target product 2a.

[0157] <Example 6>

[0158] Photocatalysis of arylboronic acids (using O2 as the oxidant and N,N-diisopropylethylamine (DIPEA) as the sacrificial electron donor at room temperature under light illumination), and the chemical reaction formula is as follows;

[0159]

[0160] Table 3 COF-JLU236 [a] Optimization of Photocatalytic Conditions for Arylboronic Acids Oxidation

[0161] Entry Catalyst Solvent Time (h) <![CDATA[Yield(%) [b] > 1 COF-JLU236 DMF 6 21 2 COF-JLU236 <![CDATA[CH3CN]]> 6 84 3 COF-JLU236 <![CDATA[H2O]]> 6 89 4 COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 98 5 TTTB <![CDATA[CH3CN / H2O]]> 6 trace 6 TAPB <![CDATA[CH3CN / H2O]]> 6 trace 7 COF-JLU237 <![CDATA[CH3CN / H2O]]> 6 33 <![CDATA[8 [c] > COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 trace 9 ～ <![CDATA[CH3CN / H2O]]> 6 trace <![CDATA[10 [d] > COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 53 <![CDATA[11 [e] > COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 trace 12 COF-JLU236 <![CDATA[CH3CN / H2O]]> 1 46 13 COF-JLU236 <![CDATA[CH3CN / H2O]]> 2 68 14 COF-JLU236 <![CDATA[CH3CN / H2O]]> 3 79 <![CDATA[15 [f] > COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 85 <![CDATA[16 [g] > COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 67 <![CDATA[17 [h] > COF-JLU236 <![CDATA[CH3CN / H2O]]> 6 24

[0162] In Table 3, [a] Reaction conditions: photocatalyst (5.0 mg), 1a (0.1 mmol), solvent (1.0 mL), O2 (1 atm), at room temperature and under blue light irradiation (460 nm, 30 W LED lamp). [b] Isolated yield. [c] In the dark. [d] In air. [e] In an argon atmosphere. [f] TEMPO as a radical scavenger. [g] NaN3 as a singlet oxygen scavenger. [h] BQ as a superoxide anion scavenger.

[0163] As can be seen from Table 3, in the CH3CN / H2O reaction system, COF-JLU236 exhibits excellent catalytic activity for the photocatalytic oxidation of arylboronic acids, and the isolated yield of the target product reaches 98%. Phenolic compounds are important intermediates in natural products and drugs, and their preparation methods have always been a research hotspot in the chemical field. The photocatalytic oxidation reaction of arylboronic acids has become an efficient and environmentally friendly strategy for phenolic compounds due to its advantages such as green environmental protection and mild reaction conditions. To deeply explore the photocatalytic performance of COF-JLU236 in this reaction system, the data in Table 3 were analyzed in detail. The results show that COF-JLU236 can efficiently promote the conversion of arylboronic acids to phenolic compounds, demonstrating good substrate adaptability and catalytic efficiency, further confirming its excellent photocatalytic performance in the reaction of photocatalytic oxidation of arylboronic acids to prepare phenolic compounds.

[0164] <Example 7>

[0165] Photocatalysis of phenylboronic acid and its derivatives to phenols, and the chemical reaction formula is as follows;

[0166]

[0167] Table 4 Photocatalytic Oxidation of Phenylboronic Acid by COFJLU236 to Generate Phenol [a] 。

[0168]

[0169] In Table 4, [a] Reaction conditions: photocatalyst (5.0 mg), substrate (0.1 mmol), solvent (1.0 mL), oxygen (1 atm), at room temperature and under blue light irradiation (460 nm, 30 W LED lamp). [b] Isolated yield.

[0170] As can be seen from Table 4, COF-JLU236 can efficiently promote the conversion of various phenylboronic acids and their derivatives into phenolic compounds. To investigate its recyclability, relevant experiments were further carried out, and the results are as Figure 22 shown. It can be clearly seen from Figure 22 that during multiple recycling processes, the catalytic activity of COF-JLU236 did not show a significant decrease, demonstrating good recyclability. This characteristic gives COF-JLU236 significant advantages in practical applications and is expected to provide a sustainable catalytic solution for related organic synthesis reactions.

[0171] In addition, the present invention proposes a possible mechanism for the photocatalytic oxidation of phenylboronic acid by COF-JLU236, as Figure 23 shown. To systematically explain the differences in photocatalytic activity of the novel COF-JLU in organic synthesis, a series of optoelectronic property characterizations were carried out. During the photocatalytic process, the generation, separation, and migration efficiency of photo-generated charges are the key factors determining the catalytic efficiency.

[0172] The results of transient photocurrent tests, as Figure 14 shown in i, indicate that both COF-JLU materials exhibit rapid photo-response characteristics. Notably, the transient photocurrent intensity of COF-JLU236 is significantly higher than that of COF-JLU237, which means that the separation efficiency of photo-generated electron-hole pairs in COF-JLU236 is better. In addition, electrochemical impedance spectroscopy (EIS) analysis further corroborates this conclusion. The arc radius ( Figure 14 j) of the Nyquist plot of COF-JLU236 is significantly smaller than that of COF-JLU237, indicating that the charge transfer resistance in COF-JLU236 is lower and the interfacial charge transport is more efficient.

[0173] Time-resolved fluorescence spectroscopy tests show that ( Figure 14 k) the average fluorescence lifetime of COF-JLU236 (2.62 ns) is significantly longer than that of COF-JLU237 (1.71 ns). This result is consistent with the band structure analysis calculated by density functional theory (DFT), both indicating that COF-JLU236 has a more excellent photo-generated carrier separation ability. The above optoelectronic property test results show a good correspondence with the catalytic activity of the material in the phenylboronic acid oxidation reaction, jointly revealing the efficient catalytic mechanism of COF-JLU236.

[0174] The present invention has successfully designed and constructed two imine condensation reaction-based azadiene-linked covalent organic frameworks (COFs). The new materials, COF-JLU236 and COF-JLU237, have inherent porosity, broad visible light harvesting ability, excellent optoelectronic properties, and good durability. In particular, the new azadiene-linked COF-JLU236 was found to be a superior heterogeneous photocatalyst with broad substrate adaptability and excellent reusability for the selective oxidation of sulfides and phenylboronic acid under mild conditions. This invention enriches the types of COF materials and develops new avenues for outstanding solid photocatalysts at the molecular level.

[0175] The number of devices and the processing scale described herein are used to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0176] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the examples shown and described herein.

Claims

1. Aza-diene-linked covalent organic framework polymer, characterized in that, The structural formula is as shown in Formula I or Formula II; 2. The azadiene-linked covalent organic framework polymer according to claim 1, wherein The covalent organic framework polymer is a crystalline porous structure formed by connecting through extended π-conjugated aza-diene (C=N-C=C) bonds; the covalent organic framework polymer has a two-dimensional layered stacking structure, with a specific surface area of 600-652 m 2 / g and a pore size of 2.4-2.5 nm.

3. A method for preparing the nitrogen hetero-diene-linked covalent organic framework polymer as described in claim 1 or 2, characterized in that, It includes the following steps: Mix the triazinyl triacrolein monomer and the triamino monomer in a molar ratio of 1:1, dissolve them in a mixed organic solvent and stir evenly to form a reaction system. Add an acid catalyst to the reaction system and react at 100 °C for 3 days. After centrifugation, washing, and drying, it is obtained; the concentrations of the triazinyl triacrolein monomer and the triamino monomer in the reaction system are both 0.05 mol / L.

4. The method according to claim 3, wherein The acid catalyst is an acetic acid aqueous solution with a concentration of 6 M, and the volume of the acetic acid aqueous solution is 10% of the volume of the mixed organic solvent.

5. The method according to claim 3, wherein The triazinyl triacrolein monomer is 3,3',3”-((1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))triacrolein (TTTB); The triamino monomer is 1,3,5-tris(4-aminophenyl)benzene (TAPB) or 1,3,5-tris(4-aminophenyl)triazine (TAPT).

6. The method according to claim 3, wherein The mixed organic solvent is prepared by mixing 1,4-dioxane and mesitylene in a volume ratio of 4:

6.

7. Use of the aza-diene linked covalent organic framework polymer as claimed in claim 1 or 2 as a photocatalyst in an organic synthesis reaction, characterized in that, The organic synthesis reaction is the selective oxidation of arylboronic acid or sulfide.

8. The application according to claim 7, wherein The conditions of the organic synthesis reaction are as follows: Using oxygen as the oxidant, the oxygen pressure is 1 atm; Using methanol, acetonitrile or water as the solvent; Using an LED lamp to generate a visible light source with a wavelength of 460 nm and a power of 30 W as the light source; The reaction temperature is room temperature, and the reaction time is 1 - 15 h; The substrate concentration is 0.1 mmol / mL; the dosage ratio of the photocatalyst to the substrate is 5 mg:0.1 mmol; In the organic synthesis reaction, an electron donor N,N-diisopropylethylamine (DIPEA) is also added, and its dosage is 1 - 5 times the molar amount of the substrate.

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