Covalent triazine framework photocatalyst based on chromophore modification as well as preparation method and application of covalent triazine framework photocatalyst

Abstract

The invention belongs to the technical field of photocatalysis, and discloses a chromophore modification-based covalent triazine framework photocatalyst as well as a preparation method and application thereof. The covalent triazine framework is composed of a plurality of repeated structural units, a chromophore is a nitro group or an oxazole group, the structural formula of the structural units is shown as a formula I or a formula II, and in the formula, ''-'' represents an omitted repeated structural unit; 1, 4-di (4-formyl phenyl) benzene with a substituent group, ammonium iodide, ferric acetate hydrate and a solvent I are mixed by # imgabs0 # to obtain reaction liquid I, and then the chromophore modified covalent triazine frame photocatalyst is obtained through reaction. The activity of the CTF-1 modified by the chromophore and the activity of the CTF-2 modified by the chromophore in the photocatalytic imidazo [1, 2-a] pyridine C3-H bond sulfonyl imidization reaction are respectively 1.50 times and 1.71 times that of the CTF-3 (which is not modified by the chromophore). Meanwhile, the catalyst has good reusability, and the activity of the CTFs photocatalyst is basically unchanged after the catalyst is repeatedly used for five times.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysis, and in particular to a covalent triazine framework photocatalyst. Background Art

[0002] Light is a clean and renewable energy source. The use of light to drive organic reactions has a history of more than 100 years. In particular, in the past nearly 30 years, organic reactions catalyzed by visible light and photosensitivity small molecules have exploded. Traditional homogeneous photocatalysts are mainly concentrated on metal ruthenium and iridium complexes. There are problems with the high price and toxicity of the catalysts; in the pharmaceutical industry, "metal-free" catalytic systems are more popular. Therefore, visible light-induced "metal-free" catalysis has received increasing attention in organic transformations. Covalent triazine frameworks (CTFs) are formed by the polymerization of pure organic conjugated molecular monomers. They are easy to synthesize and characterize, and have the characteristics of stable structure, diverse types and easy modification. The ingeniously designed CTFs structure can provide a microenvironment for highly selective catalytic reactions. At the same time, CTFs materials have good photosensitivity and can achieve different types of chemical transformations under the induction of visible light. Therefore, visible CTFs materials are green and widely used.

[0003] Imidazolo[1,2-a]pyridine molecules have good biological activity and are widely used in materials science, agricultural medicine and pharmaceutical industry. In particular, functionalized imidazo[1,2-a]pyridine has better pharmacological activity, so there are many drug molecules with imidazo[1,2-a]pyridine as the core skeleton on the market, such as Alpidem, Zolpidem, Olprinone, etc. At the same time, sulfonylimide compounds have been widely used in medicine, pesticides and materials science due to their antibacterial, anti-inflammatory, anticancer, lipid-lowering and plant growth inhibition properties, such as sulfadiazine, sulfamethoxazole, rosuvastatin, and penoxalan. Therefore, the development of a sulfonylimide imidazo[1,2-a]pyridine derivative with strong industrial applicability has important academic and industrial research significance. In recent years, people have developed a variety of methods for synthesizing sulfonylimide imidazo[1,2-a]pyridine derivatives, among which direct CH sulfonylimide is considered to be one of the most effective methods. However, the proposed scheme, although highly efficient, requires transition metal catalysts and high reaction temperatures. For example, in 2018, Song et al. developed an efficient method to achieve the CH bond sulfonylimidation reaction of 2-phenylimidazole [1,2-a] pyridine with N-fluorobenzenesulfonimide (NFSI) catalyzed by [(MeCN)4Cu]BF4 (J.Org.Chem.2018,83,13991-14000,DOI:10.1021 / acs.joc.8b02348). Photocatalysis uses clean, green light energy to produce highly active free radical intermediates under mild conditions, accelerating reactions that are difficult to complete under traditional thermochemical conditions, opening up new avenues for chemical synthesis. For example, in 2023, a paper published by Yadav's group and others reported an efficient method for photocatalytic imidazo[1,2-a]pyridine C3-H bond sulfonylimide using bis(benzenesulfonyl)imide (NHSI) as a raw material (J.Org.Chem.2023,88,9599-9614,DOI:10.1021 / acs.joc.2c02022). Although this method is mild and effective, it uses Eosin Y as a photocatalyst to construct a homogeneous catalytic system, which has the problem of low reaction activity and the inability to recycle the photocatalyst after completion. Summary of the invention

[0004] In order to solve the technical problem that the photocatalytic imidazo[1,2-a]pyridine C3-H bond sulfonylimidization reaction system has low photocatalytic activity and cannot be reused, the present invention proposes a covalent triazine framework photocatalyst based on chromophore modification and its preparation method and application. To achieve the above purpose, the technical solution of the present invention is implemented as follows:

[0005] A chromophore-modified covalent triazine framework photocatalyst, which is composed of a plurality of repeated structural units, wherein the chromophore is a nitro group or an oxazole group, wherein the structural formula of the structural unit is shown in the following formula I or formula II, wherein "--" indicates an omitted repeated structural unit;

[0006]

[0007] The preparation method of the above-mentioned chromophore-modified covalent triazine framework photocatalyst comprises the following steps: uniformly mixing 1,4-di(4-formylphenyl)benzene with a substituent, ammonium iodide, ferric acetate hydrate and solvent I to prepare a reaction solution I, followed by a reaction, washing and drying after the reaction, respectively using N,N-dimethylformamide (DMF), acetonitrile (MeCN), dilute HCl (1.5M), water and anhydrous ethanol to wash until the liquid is colorless, then wetting the solid with anhydrous ethanol and grinding it into a fine powder, then Soxhlet extraction with methanol as a solvent for 24 hours, and finally drying the obtained solid in a vacuum drying oven at 70°C for 24 hours to obtain a chromophore-modified covalent triazine framework catalyst.

[0008] The molar ratio of the substituted 1,4-di(4-formylphenyl)benzene, ammonium iodide and ferric acetate hydrate is 1:(1-3):(0.1-1); preferably, the molar ratio of the substituted 1,4-di(4-formylphenyl)benzene, ammonium iodide and ferric acetate hydrate is 1:2:0.45.

[0009] The 1,4-di(4-formylphenyl)benzene with a substituent is 2'-nitro-[1,1':4',1"-terphenyl]-4,4"-dicarboxaldehyde or 4,4'-(benzothiazole-4,7-diyl)dibenzaldehyde.

[0010] The preparation method of 2'-nitro-[1,1':4',1"-terphenyl]-4,4"-dicarboxaldehyde or 4,4'-(benzothiazole-4,7-diyl)dibenzaldehyde comprises the following steps: under palladium catalysis, 2,5-dibromonitrobenzene (or 4,7-dibromobenzothiazole) and 4-formylphenylboronic acid are subjected to cross-coupling reaction to obtain the product.

[0011] Furthermore, the preparation method of the above-mentioned 2'-nitro-[1,1':4',1"-terphenyl]-4,4"-dicarboxaldehyde or 4,4'-(benzothiazole-4,7-diyl)dibenzaldehyde comprises the following steps: adding 2,5-dibromonitrobenzene (or 4,7-dibromobenzothiazole), 4-formylphenylboric acid, a base and a palladium catalyst to a mixed solvent (consisting of tetrahydrofuran, methanol and distilled water), heating to reflux (cross-coupling reaction), removing the solvent, filtering, washing, drying and separating and purifying to obtain the product.

[0012] Furthermore, the molar ratio of the above-mentioned 2,5-dibromonitrobenzene (or 4,7-dibromobenzothiazole), 4-formylphenylboronic acid and palladium catalyst is 1:(2-5):(0.01-0.5); preferably, the molar ratio of 2,5-dibromonitrobenzene (or 4,7-dibromobenzothiazole), 4-formylphenylboronic acid and palladium catalyst is 1:2.5:0.05.

[0013] Furthermore, the temperature of the heating reflux reaction is 60-100°C and the time is 12-48h; preferably, the temperature of the heating reflux reaction is 75°C and the time is 24h.

[0014] The above solvent I is o-dichlorobenzene.

[0015] The concentration of substituted 1,4-di(4-formylphenyl)benzene in the reaction solution I is 0.02-0.2 mol / L; preferably, the concentration of substituted 1,4-di(4-formylphenyl)benzene in the reaction solution I is 0.1 mol / L.

[0016] The reaction temperature is 40-160°C and the reaction time is 1-4 days. In order to control the reaction speed, adjust the product particle size and avoid agglomeration, a step-by-step heating reaction method can be adopted, for example, heating at 40, 80, 120, and 160°C for 24 hours each.

[0017] The above-mentioned chromophore-modified covalent triazine framework photocatalyst is used in catalyzing the C3-H bond sulfonylimidization reaction of imidazo[1,2-α]pyridine.

[0018] Furthermore, the steps of the above-mentioned sulfonylimidization reaction are: uniformly mixing the chromophore-modified covalent triazine framework photocatalyst, imidazo[1,2-α]pyridine derivative, sulfonamide derivative, iodophenyldiacetic acid and solvent II to prepare reaction solution II, and reacting under visible light irradiation.

[0019] The addition amount of the above-mentioned chromophore-modified covalent triazine framework photocatalyst based on solvent II is 1-100 mg / mL; the concentration of imidazo[1,2-α]pyridine derivative in reaction solution II is 0.1-1 mol / L, the concentration of sulfonamide derivative is 0.2-2 mol / L, and the concentration of iodophenyldiacetic acid is 0.2-2 mol / L; solvent II is 1,2-dichloroethane (DCE).

[0020] Preferably, the addition amount of the above-mentioned covalent triazine framework catalyst based on solvent II is 5 mg / mL; the concentration of imidazo[1,2-α]pyridine derivative in reaction solution II is 0.2 mol / L, the concentration of sulfonamide derivative is 0.4 mol / L, and the concentration of iodophenyldiacetic acid is 0.4 mol / L.

[0021] After the synthesis reaction in the present invention is completed, the post-treatment process is not particularly limited. The reaction mixture is first filtered, and the filtered residue is washed with a solvent to obtain a CTFs catalyst for repeated use; then the solvent of the filtrate is removed, and the target product is obtained by column chromatography separation or recrystallization.

[0022] The beneficial effects produced by the present invention are:

[0023] (1) The CTFs material of the present invention is prepared by a common solvothermal process, which does not require isolation from air and water. The preparation method is simple and easy, and it is also easier to mass produce, which reduces costs, provides a new choice for photocatalyst materials, and expands the application value of CTFs materials.

[0024] (2) The chromophore introduced in the present invention can improve the overall conjugation of CTFs materials, thereby broadening their visible light absorption range, improving the band gap structure, reducing the recombination rate of photogenerated carriers, improving the charge separation efficiency and electron mobility, and ultimately significantly improving the photocatalytic activity of CTFs. Experiments show that the photocatalytic performance of the constructed chromophore-modified CTF-1 and CTF-2 is better than that of the unmodified CTF-3, among which the activity of CTF-1 and CTF-2 in the photocatalytic imidazo[1,2-a]pyridine C3-H bond sulfonylimidization reaction is 1.50 and 1.71 times that of CTF-3, respectively.

[0025] (3) The CTFs photocatalyst constructed by the present invention has good stability and can be recycled multiple times, and there is no obvious change in the catalyst structure and activity after multiple cycles.

[0026] (4) As a photocatalytic material, the catalytic reaction takes place at room temperature and only requires visible light irradiation without heating. The catalytic conditions are simple and the catalytic process is energy-saving, environmentally friendly and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 FT-IR spectra of (a) CTF-1, (b) CTF-2, (c) CTF-3 and the corresponding monomers; (d) CTF-1, (e) CTF-2, (f) CTF-3 13 C CP / MAS ssNMR test spectrum.

[0029] Figure 2Thermogravimetric curves of CTF-1, CTF-2 and CTF-3 under nitrogen atmosphere.

[0030] Figure 3 SEM images of (a) CTF-1, (b) CTF-2, and (c) CTF-3.

[0031] Figure 4 SEM image and EDX spectrum of aluminum sheet as CTF-1 substrate.

[0032] Figure 5 SEM image and EDX spectrum of aluminum sheet as CTF-2 substrate.

[0033] Figure 6 SEM image and EDX spectrum of aluminum sheet as CTF-3 substrate.

[0034] Figure 7 (a) N2 adsorption isotherms of CTF-1, CTF-2 and CTF-3 at 77K; (b) pore size distribution diagram of CTF-1, (c) CTF-2 and (d) CTF-3.

[0035] Figure 8 UV-vis DRS spectra of CTF-1, CTF-2 and CTF-3.

[0036] Fig. 9 Band gap energy spectra calculated using the Kubelka-Munk formula for CTF-1, CTF-2, and CTF-3.

[0037] Fig.10 Photoluminescence emission spectra of CTF-1, CTF-2 and CTF-3.

[0038] Fig.11 These are the photocurrent response spectra of CTF-1, CTF-2, and CTF-3.

[0039] Fig.12 Nyquist impedance diagrams of CTF-1, CTF-2, and CTF-3.

[0040] Fig.13 This is the H NMR spectrum of the target product 3aa.

[0041] Fig.14 This is the NMR carbon spectrum of the target product 3aa.

[0042] Fig.15 (a) Evaluation of the reusability of CTF-1 in photocatalytic hydroxylation reactions; (b) FT-IR spectra of CTF-1 before and after five catalytic cycles, and (c) N2 adsorption curves. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The preparation method of 2'-nitro-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde used in the present invention comprises the following steps: 2,5-dibromonitrobenzene (1124 mg, 4 mmol), 4-formylphenylboric acid (1499 mg, 10 mmol), Pd(PPh3)4 (232 mg, 0.2 mmol), K2CO3 (2073 mg, 15 mmol) and a magnet are placed in a 250 mL flask, and 50 mL of tetrahydrofuran, 25 mL of methanol and 25 mL of distilled water are added under nitrogen conditions. The mixture is heated at 75° C. for 24 hours on a heating mantle, and the entire reaction is carried out under a nitrogen atmosphere, during which stirring and condensation reflux are kept turned on. After the reaction is completed, the flask is taken out and cooled to room temperature, and the organic solvent is removed under vacuum conditions. The solid is then filtered, washed with 100 mL*3 of distilled water, and dried. The solid was then purified by column chromatography (petroleum ether-dichloromethane) to obtain 1205 mg of 2'-nitro-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde with a yield of 85%.

[0045] The preparation method of 4,4'-(benzothiazole-4,7-diyl)benzaldehyde used in the present invention comprises the following steps: 4,7-dibromobenzothiazole (1172 mg, 4 mmol), 4-formylphenylboronic acid (1499 mg, 10 mmol), Pd(PPh3)4 (232 mg, 0.2 mmol), K2CO3 (2073 mg, 15 mmol) and a magnet are placed in a 250 mL flask, and 50 mL of tetrahydrofuran, 25 mL of methanol and 25 mL of distilled water are added under nitrogen conditions. The mixture is heated at 75°C for 24 hours on a heating mantle, and the entire reaction is carried out under a nitrogen atmosphere, during which stirring and condensation reflux are kept turned on. After the reaction is completed, the flask is taken out and cooled to room temperature, and the organic solvent is removed under vacuum conditions. The solid is then filtered, washed with 100 mL*3 of distilled water, and dried. The solid was then purified by column chromatography (petroleum ether-dichloromethane) to obtain 1249 mg of 4,4'-(benzothiazole-4,7-diyl)benzaldehyde with a yield of 91%.

[0046] Example 1

[0047] The preparation method of the chromophore-modified covalent triazine framework photocatalyst (structure as shown in Formula I) of this embodiment comprises the following steps:

[0048] 2'-Nitro-[1,1':4',1"-terphenyl]-4,4"-dicarboxaldehyde (166 mg, 0.5 mmol), NH4I (73 mg, 1 mmol) and ferric acetate hydrate (47 mg, 0.225 mmol) were placed in a 25 mL test tube, and 5 mL of o-dichlorobenzene was added. After 5 minutes of ultrasonic dispersion, the mixture was heated on a heating mantle at 40, 80, 120, and 160 ° C for 24 hours each. The entire reaction was carried out under air atmosphere, and stirring and condensation reflux were kept turned on. After the reaction is completed, the test tube is taken out and cooled to room temperature, 10 mL of dilute hydrochloric acid (1.5 M) / methanol = 1 / 1 is added, stirred and mixed evenly, and then soaked for half an hour, and then the product is separated by centrifugation, and washed with DMF, MeCN, dilute HCl (1.5 M), water and anhydrous ethanol respectively until the liquid is colorless, and then the solid is moistened with anhydrous ethanol and ground into fine powder, and then Soxhlet extraction is performed with methanol for 24 hours, and finally the obtained solid is dried in a vacuum drying oven at 70°C for 24 hours. Take it out and return it to room temperature to obtain olefin-linked CTF-1.

[0049] Example 2

[0050] The preparation method of the chromophore-modified covalent triazine framework photocatalyst (structure as shown in Formula II) of this embodiment comprises the following steps:

[0051] 4,4'-(Benzothiazole-4,7-diyl)benzaldehyde (172mg, 0.5mmol), NH4I (73mg, 1mmol) and ferric acetate hydrate (47mg, 0.225mmol) were placed in a 25mL test tube and 5mL o-dichlorobenzene was added. After 5 minutes of ultrasonic dispersion, the mixture was heated on a heating mantle at 40, 80, 120, and 160°C for 24 hours each. The entire reaction was carried out under air atmosphere, and stirring and condensation reflux were kept on during the reaction. After the reaction, the test tube was taken out and cooled to room temperature, 10mL of dilute hydrochloric acid (1.5M) / methanol = 1 / 1 was added, stirred and mixed evenly, and then soaked for half an hour, and then the product was separated by centrifugation, and washed with DMF, MeCN, dilute HCl (1.5M), water and anhydrous ethanol respectively until the liquid was colorless, and then the solid was moistened with anhydrous ethanol and ground into fine powder, and then Soxhlet extraction was performed with methanol for 24 hours, and finally the obtained solid was dried in a vacuum drying oven at 70°C for 24 hours. Take out and return to room temperature to obtain olefin-linked CTF-2.

[0052] Comparative Example

[0053] The preparation method of the covalent triazine framework photocatalyst of this comparative example is different from that of Example 1 in that there is no substituent on 1,4-di(4-formylphenyl)benzene, and the steps are as follows:

[0054] 1,4-di(4-formylphenyl)benzene (143mg, 0.5mmol), NH4I (73mg, 1mmol) and ferric acetate hydrate (47mg, 0.225mmol) were placed in a 25mL test tube and 5mL o-dichlorobenzene was added. After 5 minutes of ultrasonic dispersion, the mixture was heated on a heating mantle at 40, 80, 120, and 160°C for 24 hours each. The entire reaction was carried out under air atmosphere, and stirring and condensation reflux were kept on during the reaction. After the reaction, the test tube was taken out and cooled to room temperature, 10mL of dilute hydrochloric acid (1.5M) / methanol = 1 / 1 was added, stirred and mixed evenly, and then soaked for half an hour, and then the product was separated by centrifugation, and washed with DMF, MeCN, dilute HCl (1.5M), water and anhydrous ethanol respectively until the liquid was colorless, and then the solid was moistened with anhydrous ethanol and ground into fine powder, and then Soxhlet extraction was performed with methanol for 24 hours, and finally the obtained solid was dried in a vacuum drying oven at 70°C for 24 hours. The reaction mixture was taken out and returned to room temperature to obtain olefin-linked CTF-3.

[0055] The structural formulas of the structural units in CTF-1, CTF-2 and CTF-3 prepared in Example 1, Example 2 and Comparative Example 1 are shown below, where “--” represents an omitted repeating structural unit;

[0056]

[0057] In the FT-IR spectrum, the CTFs at 1690 cm -1 The stretching vibration peak of the aromatic aldehyde group (Ar-CHO) at 1508 cm -1 and 1365cm -1 The triazine group vibration peak was newly added at , indicating that the aldehyde group participated in the reaction and condensed into a triazine ring, which preliminarily verified the successful synthesis of CTFs ( Figure 1 ac).

[0058] 13 The C CP / MAS NMR peak at 171.0 ppm further confirmed the successful condensation of the triazine groups ( Figure 1 df). Meanwhile, the peaks at 133.9, 133.5 and 135.7 ppm are attributed to the carbon atoms connected to the triazine ring.

[0059] In view of this, all CTFs were proven to be successfully synthesized.

[0060] It can be seen from the TGA curves that in N2 atmosphere, the three CTFs have good thermal stability and there is no obvious mass decay within 260℃ ( Figure 2 ).

[0061] The morphology of these CTFs was observed using FE-SEM ( Figure 3 ). CTF-1 and CTF-2 have similar coral-like porous structures, and CTF-3 is stacked in a granular form and also presents a porous structure. In addition, the surface of CTF-2 and CTF-3 is entangled with nanofilaments.

[0062] At the same time, it can be seen from EDX that these CTFs are evenly distributed with elements such as C and N ( Figure 4-6 ), the distribution of O elements in CTF-1 and N elements in CTF-2 also indicate that both nitro groups and oxazole groups were successfully introduced into their respective frameworks.

[0063] N2 adsorption was performed at 77 K to evaluate the permanent porosity of CTF-1, CTF-2, and CTF-3. Figure 7 As shown in (a), these CTFs exhibit typical type I adsorption isotherms, indicating microporous characteristics. The BET surface areas of CTF-1, CTF-2, and CTF-3 were calculated to be 19, 63, and 18 m 2 g -1 The pore sizes of the three CTFs were studied using the NLDFT model, which were 2.62, 2.57, and 2.73 nm ( Figure 7 bd).

[0064] The photoelectric properties of these CTFs were evaluated by ultraviolet-visible spectroscopy (UV-vis). Figure 8 As shown, these CTFs have a wide absorption range in the visible light region. The maximum peak of the wide absorption band of CTF-1 is 424nm, CTF-2 is 451nm, and CTF-3 is 405nm. The results are obvious. Compared with CTF-3, CTF-1 and CTF-2 have leading visible light absorption ranges, proving that the introduction of chromophores into the CTFs framework can red-shift the maximum absorption wavelength of CTFs. The optical band gaps of CTF-1, CTF-2, and CTF-3 are calculated to be 2.36, 2.10, and 2.41 eV, respectively, using Kubelka-Munk transform reflectance spectra. Fig. 9 ), proving that the band gap of CTFs can be effectively improved after the chromophore is introduced into the CTFs framework.

[0065] From the PL spectra of these three CTFs ( Fig.10 ), the fluorescence intensities of CTF-1 and CTF-2 are similar, both lower than that of CTF-3, indicating that the introduction of chromophore into the CTFs framework can effectively reduce the recombination rate of photogenerated carriers of CTFs. Obviously, chromophore can effectively improve the photoelectric properties of CTFs, and more electrons can be transmitted and utilized in the photocatalytic process.

[0066] The charge separation and migration behaviors of these three CTFs were investigated using TPC measurements and EIS. Fig.11 As shown in the figure, the transient photocurrents of CTF-3, CTF-1 and CTF-2 increase in turn. Compared with CTF-3 without chromophore modification, CTF-1 and CTF-2 both have a significant improvement in transient photocurrent response. CTF-1 and CTF-2 show faster light response speeds, indicating that the charge separation efficiency of photogenerated charges under visible light irradiation is improved. Therefore, the introduction of chromophores on CTFs can effectively improve the photoelectric activity of CTFs.

[0067] In addition, the impedance of these three CTFs showed a trend of CTF-3>CTF-1>CTF-2 ( Fig.12 ), which indicates that the introduction of chromophores on CTFs can effectively reduce the charge transfer resistance of CTFs, increase the electron mobility, and thus more effectively limit the electron-hole recombination rate.

[0068] The CTF-1, CTF-2 and CTF-3 used in the following application experiments are all catalysts prepared in Examples 1, 2 and Comparative Example 1.

[0069] Example 3

[0070] The preparation method of the chromophore-modified covalent triazine framework photocatalyst (structure as shown in Formula I) of this embodiment comprises the following steps:

[0071] 2'-Nitro-[1,1':4',1"-terphenyl]-4,4"-dicarboxaldehyde (166 mg, 0.5 mmol), NH4I (36.5 mg, 0.5 mmol) and ferric acetate hydrate (104.4 mg, 0.5 mmol) were placed in a 25 mL test tube, and 2.5 mL of o-dichlorobenzene was added. After ultrasonic dispersion for 5 minutes, the mixture was heated on a heating mantle at 40, 80, 120, and 160 ° C for 24 hours each. The entire reaction was carried out under air atmosphere, and stirring and condensation reflux were kept turned on. After the reaction is completed, the test tube is taken out and cooled to room temperature, 10 mL of dilute hydrochloric acid (1.5 M) / methanol = 1 / 1 is added, stirred and mixed evenly, and then soaked for half an hour, and then the product is separated by centrifugation, and washed with DMF, MeCN, dilute HCl (1.5 M), water and anhydrous ethanol respectively until the liquid is colorless, and then the solid is moistened with anhydrous ethanol and ground into fine powder, and then Soxhlet extraction is performed with methanol for 24 hours, and finally the obtained solid is dried in a vacuum drying oven at 70°C for 24 hours. Take it out and return it to room temperature to obtain olefin-linked CTF-1.

[0072] Example 4

[0073] The preparation method of the chromophore-modified covalent triazine framework photocatalyst (structure as shown in Formula II) of this embodiment comprises the following steps:

[0074] 4,4'-(Benzothiazole-4,7-diyl)benzaldehyde (172 mg, 0.5 mmol), NH4I (109.5 mg, 1.5 mmol) and ferric acetate hydrate (10.4 mg, 0.05 mmol) were placed in a 25 mL test tube, and 25 mL of o-dichlorobenzene was added. After ultrasonic dispersion for 5 minutes, the mixture was heated on a heating mantle at 40, 80, 120, and 160 ° C for 24 hours each. The entire reaction was carried out under air atmosphere, and stirring and condensation reflux were kept on. After the reaction is completed, the test tube is taken out and cooled to room temperature, 10 mL of dilute hydrochloric acid (1.5 M) / methanol = 1 / 1 is added, stirred and mixed evenly, and then soaked for half an hour, and then the product is separated by centrifugation, and washed with DMF, MeCN, dilute HCl (1.5 M), water and anhydrous ethanol respectively until the liquid is colorless, and then the solid is moistened with anhydrous ethanol and ground into fine powder, and then Soxhlet extraction is performed with methanol for 24 hours, and finally the obtained solid is dried in a vacuum drying oven at 70°C for 24 hours. Take it out and return it to room temperature to obtain olefin-linked CTF-2.

[0075] Application Example 1

[0076] 39 mg of 2-phenylimidazo[1,2-a]pyridine, 5 mg of CTF-1 catalyst, 119 mg of 1,2-benzenedisulfonimide, 129 mg of iodophenyldiacetic acid, and 1.0 mL of DCE were weighed into a 20 mL reaction tube. A stirring bar was added thereto, and then the mixture was stirred for 3 h at 25°C in an air atmosphere under white light (λ≥420 nm). After the reaction was completed, the catalyst was removed by filtration, the filtrate solvent was removed by a rotary evaporator, and then 76.3 mg of the sulfonylimidation product 3aa was obtained by column chromatography separation with a yield of 78%.

[0077]

[0078] The NMR data of the sulfonylimidation product 3aa (such as Fig.13 and 14 ): 1 H NMR (400MHz, CDCl3): δ7.92(d,J=7.4Hz,4H),7.73(d,J=7.2Hz,2H),7.64(d,J=8.9Hz,1H),7.57(t,J=7.5Hz,2H),7.5 1(d,J=6.9Hz,1H),7.39(t,J=7.8Hz,4H),7.29-7.25(m,1H),7.19-7.15(m,1H),7.13-7.09(m,2H),6.67-6.63(m,1H);13 C NMR (100MHz, CDCl3): δ145.5,144.5,139.1,134.6,131.8,129.1,129.0,128.5,128.1,127.5,126.9,123.9,117.9,112.7,111.1.

[0079] Application Example 2

[0080] 39 mg of 2-phenylimidazo[1,2-a]pyridine, 5 mg of CTF-2 catalyst, 119 mg of 1,2-benzenedisulfonimide, 129 mg of iodophenyldiacetic acid, and 1.0 mL of DCE were weighed into a 20 mL reaction tube. A stirring bar was added thereto, and then the mixture was stirred for 3 h at 25°C in an air atmosphere under white light (λ≥420 nm). After the reaction was completed, the catalyst was removed by filtration, the filtrate solvent was removed by a rotary evaporator, and then 87.0 mg of the sulfonylimidation product 3aa was obtained by column chromatography separation with a yield of 89%.

[0081] Comparative application example 1

[0082] 39 mg of 2-phenylimidazo[1,2-a]pyridine, 5 mg of CTF-3 catalyst, 119 mg of 1,2-benzenedisulfonimide, 129 mg of iodophenyldiacetic acid, and 1.0 mL of DCE were weighed into a 20 mL reaction tube. A stirring bar was added, and then the mixture was stirred for 3 h at 25°C in an air atmosphere under white light (λ≥420 nm). After the reaction was completed, the catalyst was removed by filtration, and the filtrate solvent was removed by a rotary evaporator. Then, 50.9 mg of the sulfonylimidation product 3aa was obtained by column chromatography separation, with a yield of 52%.

[0083] Comparative Application Example 2

[0084] 39 mg of 2-phenylimidazo[1,2-a]pyridine, 119 mg of 1,2-benzenedisulfonimide, 129 mg of iodophenyldiacetic acid, and 1.0 mL of DCE were weighed into a 20 mL reaction tube, and a stirring bar was added thereto, and then stirred for 3 h in an air atmosphere at 25°C under white light (λ≥420 nm). After the reaction was completed, the catalyst was removed by filtration, the filtrate solvent was removed by a rotary evaporator, and then separated by column chromatography, but the target product 3aa was not obtained.

[0085] Application Example 3

[0086] 39 mg of 2-phenylimidazo[1,2-a]pyridine, 5 mg of CTF-2 catalyst, 119 mg of 1,2-benzenedisulfonimide, 129 mg of iodophenyldiacetic acid, and 1.0 mL of DMF were weighed in a 20 mL reaction tube. A stirring bar was added, and then the mixture was stirred for 3 h at 25°C in an air atmosphere under white light (λ≥420 nm). After the reaction was completed, the catalyst was removed by filtration, and the filtrate solvent was removed by a rotary evaporator. Then, 62.6 mg of the sulfonylimidation product 3aa was obtained by column chromatography separation, with a yield of 65%.

[0087] Application Example 4

[0088] 0.6 g of 2-phenylimidazo[1,2-a]pyridine, 75 mg of CTF-2 catalyst, 1.8 g of 1,2-benzenedisulfonimide, 2.0 g of iodophenyldiacetic acid, and 15.0 mL of DCE were weighed into a 100 mL reaction tube. A stirring bar was added thereto, and then the mixture was stirred for 3 h at 25°C in an air atmosphere under white light (λ≥420 nm). After the reaction was completed, the catalyst was removed by filtration, the filtrate solvent was removed by a rotary evaporator, and then 1.188 g of the sulfonylimidation product 3aa was obtained by column chromatography separation, with a yield of 81%.

[0089] The CTF-2 photocatalyst removed by filtration after the reaction was washed with tetrahydrofuran (20 mL*3), placed in a 70°C vacuum drying oven for 24 h, taken out and returned to room temperature, and then put into the reaction again, and this cycle was repeated 5 times. After 5 photocatalytic cycles, Fig.15 As shown in a, the yield of the product did not change significantly. The recovered CTF-2 was further characterized by FT-IR and BET. Fig.15 As shown in Figs. b and 15c, CTF-2 still maintains its original structure. These data fully demonstrate the high stability and recyclability of CTF-2. Fig.15 ).

[0090] The C3 sulfonylimidation derivative of imidazo[1,2-a]pyridine was synthesized by the same method as in Application Example 3. The various reaction conditions and reaction results are shown in Table 1.

[0091] Table 1 Synthesis of various imidazo[1,2-a]pyridine C3 sulfonylimidation derivatives under different conditions

[0092]

[0093]

[0094] It can be seen from the above embodiments that the preparation method of the present invention has a wide range of substrate applicability and a yield that can reach above medium. The CTFs photocatalyst used in the preparation method has high catalytic activity, high reaction efficiency, stable catalyst structure, and no significant change in catalyst activity after multiple uses.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A chromophore-modified covalent triazine framework photocatalyst characterized in that: The covalent triazine framework photocatalyst is composed of a plurality of repeated structural units, the chromophore is a nitro group or an oxazole group, wherein the structural formula of the structural unit is shown in the following formula I or formula II, wherein "--" indicates an omitted repeated structural unit; 2. The method for preparing the covalent triazine framework photocatalyst according to claim 1, characterized in that: The steps are as follows: 1,4-di(4-formylphenyl)benzene with a substituent, ammonium iodide, ferric acetate hydrate and solvent I are uniformly mixed to prepare a reaction solution I, followed by a reaction, and after the reaction is completed, a chromophore-modified covalent triazine frame photocatalyst is obtained.

3. The method for preparing the covalent triazine framework photocatalyst according to claim 2, characterized in that: The molar ratio of the substituted 1,4-di(4-formylphenyl)benzene, ammonium iodide and ferric acetate hydrate is 1:(1-3):(0.1-1).

4. The method for preparing a covalent triazine framework photocatalyst according to claim 2 or 3, characterized in that: The 1,4-di(4-formylphenyl)benzene with a substituent is 2'-nitro-[1,1':4',1"-terphenyl]-4,4"-dicarboxaldehyde or 4,4'-(benzothiazole-4,7-diyl)dibenzaldehyde.

5. The method for preparing the covalent triazine framework photocatalyst according to claim 4, characterized in that: The solvent I is o-dichlorobenzene.

6. The method for preparing the covalent triazine framework photocatalyst according to claim 5, characterized in that: The concentration of 1,4-di(4-formylphenyl)benzene with a substituent in the reaction solution I is 0.02-0.2 mol / L.

7. The method for preparing the covalent triazine framework photocatalyst according to claim 6, characterized in that: The reaction temperature is 40-160° C. and the reaction time is 1-4 days.

8. Use of the chromophore-modified covalent triazine framework photocatalyst according to claim 1 in catalyzing the C3-H bond sulfonylimidization reaction of imidazo[1,2-α]pyridine.

9. The use according to claim 8, characterized in that: The steps of the sulfonylimidization reaction are: uniformly mixing a chromophore-modified covalent triazine framework photocatalyst, an imidazo[1,2-α]pyridine derivative, a sulfonamide derivative, iodophenyldiacetic acid and a solvent II to prepare a reaction solution II, and reacting under visible light irradiation.

10. The use according to claim 9, characterized in that: The chromophore-modified covalent triazine framework photocatalyst is added in an amount of 1-100 mg / mL based on solvent II; the concentration of the imidazo[1,2-α]pyridine derivative in the reaction solution II is 0.1-1 mol / L, the concentration of the sulfonamide derivative is 0.2-2 mol / L, and the concentration of iodophenyldiacetic acid is 0.2-2 mol / L; and the solvent II is 1,2-dichloroethane.

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