Pyrazinyl covalent organic framework material as well as preparation method and application thereof

Abstract

The invention relates to a pyrazinyl covalent organic framework material as well as a preparation method and application thereof, 2, 5-dimethylpyrazine and aromatic aldehyde monomers are taken as construction elements, and the pyrazinyl covalent organic framework material connected with two olefins is synthesized through a Knoevenagel reaction. The pyrazinyl covalent organic framework material disclosed by the invention has good chemical stability and full-conjugate skeleton characteristics, shows excellent photocatalytic activity and cycling stability in visible light driven thioether oxidation reaction, and has potential application value in the fields of environmental restoration and green chemistry.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental remediation, and particularly relates to a pyrazine-based covalent organic framework material, a preparation method thereof, and an application thereof. Background Art

[0002] As typical environmental pollutants, sulfide compounds can pollute water and air if not properly treated, seriously threatening the ecosystem and human health. Their oxidation product, sulfoxide, is widely used in the fields of medicine, agriculture, chemistry, etc. Traditional chemical oxidation methods have problems such as over-oxidation and limited scope of applicable substrates. To solve these problems, researchers have gradually focused on developing general materials with high stability and high controllability. Therefore, constructing a new type of catalyst with both precise oxidation regulation ability and substrate universality has become the research focus in the field of environmental remediation.

[0003] Covalent organic frameworks are a class of crystalline porous polymers formed by covalently linking organic monomers. As a new type of crystalline porous material, covalent organic frameworks have characteristics such as high surface area, adjustable pore size, and good stability, and are widely used in the fields of gas separation and adsorption, sensing, catalysis, energy storage, drug delivery, etc. In addition, the benzo[c][1,2,5]oxadiazole group has good photophysical properties and electron transport properties. Therefore, introducing the benzo[c][1,2,5]oxadiazole group is expected to regulate the energy band structure and the separation efficiency of photo-generated carriers of the pyrazine-based organic framework, enhance its light absorption ability, achieve efficient catalysis for different sulfide substrates, and provide new ideas for environmental pollution treatment and green catalytic conversion. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a pyrazine-based covalent organic framework material, a preparation method thereof, and an application thereof, so as to overcome the disadvantage of the lack of a stable crystalline porous material system in the prior art.

[0005] The present invention provides a pyrazine-based covalent organic framework material, and the structural general formula of the pyrazine-based covalent organic framework material is: or ;

[0006] wherein, R 1 , R 2 are each independently selected from one of hydrogen, alkyl, alkoxy, and halogen atoms; X is each independently selected from one of oxygen, sulfur, and selenium atoms; Y is each independently selected from one of carbon and nitrogen atoms.

[0007] The present invention also provides a preparation method of a pyrazine-based covalent organic framework material, comprising the following steps:

[0008] Obtained from the Knoevenagel reaction of aromatic aldehyde monomers and 2,5-dimethylpyrazine; wherein, the general structural formula of the aromatic aldehyde monomers is: , at least one of; wherein, R 1 , R 2 are each independently selected from one of hydrogen, alkyl, alkoxy, and halogen atoms; X is each independently selected from one of oxygen, sulfur, and selenium atoms; Y is each independently selected from one of carbon and nitrogen atoms.

[0009] Preferably, the aromatic aldehyde monomer is at least one of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde and [1,1':4',1"-terphenyl]-3,3",5,5"-tetraaldehyde.

[0010] Furthermore, the preparation method of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde includes:

[0011] Mix 3,5-diformylphenylboronic acid pinacol ester, 4,7-dibromobenzo[c][1,2,5]oxadiazole, tetrakis(triphenylphosphine)palladium, potassium carbonate, pure water, and 1,2-dimethoxyethane, and then stir and react to obtain it.

[0012] Furthermore, the molar ratio of 3,5-diformylphenylboronic acid pinacol ester, 4,7-dibromobenzo[c][1,2,5]oxadiazole, tetrakis(triphenylphosphine)palladium, and potassium carbonate is 306:144:9:400.

[0013] Furthermore, the molar volume ratio of pure water and 1,2-dimethoxyethane is 1:5.

[0014] Furthermore, the temperature of the stirring reaction is 90~100 o °C, and the time is 48~72 h.

[0015] Furthermore, the Knoevenagel reaction system further includes benzoic anhydride and / or benzoic acid.

[0016] Furthermore, the molar ratio of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde, 2,5-dimethylpyrazine, and benzoic anhydride in the Knoevenagel reaction system is 1:2:3.

[0017] Furthermore, the molar ratio of [1,1':4',1"-terphenyl]-3,3",5,5"-tetraaldehyde, 2,5-dimethylpyrazine, benzoic anhydride, and benzoic acid in the Knoevenagel reaction system is 1:2:2:0.2.

[0018] Preferably, the conditions for the Knoevenagel reaction are as follows: the reaction temperature is 180 - 200 o °C, and the reaction time is 5 - 7 days.

[0019] The present invention also provides an application of the pyrazine-based covalent organic framework material in the field of photocatalytic oxidation.

[0020] Beneficial effects

[0021] (1) The present invention synthesizes an alkene-linked pyrazine-based covalent organic framework material by the Knoevenagel reaction, which has good chemical stability and can withstand 12 mol / L hydrochloric acid solution and 12 mol / L sodium hydroxide solution while maintaining an intact framework structure, breaking through the technical bottleneck that traditional imine-linked covalent organic framework materials are prone to structural collapse or degradation under harsh conditions.

[0022] (2) The present invention introduces a heterocycle to regulate the band gap structure of the covalent organic framework and adopts a melt polymerization preparation method, overcoming the limitations of the traditional solvothermal method.

[0023] (3) The pyrazine-based covalent organic framework material in the present invention is a type of organic semiconductor that can generate reactive oxygen free radicals under light irradiation, providing another method in addition to chemical oxidation, enabling the substrate sulfide to be converted into a high-value sulfoxide product. Description of the drawings

[0024] Figure 1 1H NMR spectrum of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde synthesized in Example 1.

[0025] Figure 2 Schematic diagram of the synthesis route of the pyrazine-based covalent organic framework material of the present invention; among them, the monomers involved are [1,1':4',1"-terphenyl]-3,3",5,5"-tetraaldehyde (TPTA), 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde (BODP), and 2,5-dimethylpyrazine (PZ); the pyrazine-based covalent organic framework materials involved are the pyrazine-based COF-BP material synthesized in Example 2 and the pyrazine-based COF-TP material synthesized in Example 3.

[0026] Figure 3 Fourier transform infrared spectra of the pyrazine-based COF-BP material synthesized in Example 2, and PZ and BODP.

[0027] Figure 4 Fourier transform infrared spectra of the pyrazine-based COF-TP material synthesized in Example 3, and PZ and TPTA.

[0028] Figure 5Powder X-ray diffraction pattern of the synthesized pyrazine-based COF-BP material in Example 2.

[0029] Figure 6 Powder X-ray diffraction pattern of the synthesized pyrazine-based COF-TP material in Example 3.

[0030] Figure 7 Nitrogen adsorption-desorption isotherm and BET specific surface area of the synthesized pyrazine-based COF-BP material in Example 2.

[0031] Figure 8 Nitrogen adsorption-desorption isotherm and BET specific surface area of the synthesized pyrazine-based COF-TP material in Example 3.

[0032] Figure 9 Carbon-13 nuclear magnetic resonance spectra of the synthesized pyrazine-based covalent organic framework materials in Examples 2 and 3.

[0033] Figure 10 Conversion rate comparison chart of four materials (COF-IM, AMP-BP, COF-TP, COF-BP) in Example 4 for catalyzing benzyl methyl sulfide under the same conditions.

[0034] Figure 11 Time-conversion rate bar chart of COF-BP material for catalyzing benzyl methyl sulfide in Example 5.

[0035] Figure 12 Conversion rate comparison chart of COF-BP material for catalyzing benzyl methyl sulfide in 10 cycles in Example 6.

[0036] Figure 13 Structure schematic diagram of a pyrazine-based covalent organic framework material of the present invention.

[0037] Figure 14 Conversion rates of COF-BP material for catalyzing different thioethers in Example 7. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0039] Raw material sources: 3,5-diformylphenylboronic acid pinacol ester (Shanghai Haohong Biopharmaceutical Technology Co., Ltd.), 4,7-dibromobenzo[c][1,2,5]oxadiazole (Shanghai Haohong Biopharmaceutical Technology Co., Ltd.), [1,1':4',1"-terphenyl]-3,3",5,5"-tetraformaldehyde (Jilin Zhongke Research Extension Technology Co., Ltd.), 2,5-dimethylpyrazine (Shanghai Merck Chemical Technology Co., Ltd.).

[0040] Example 1 Put 3,5-diformylphenylboronic acid pinacol ester (400.0 mg, 1.53 mmol), 4,7-dibromobenzo[c][1,2,5]oxadiazole (200.0 mg, 0.72 mmol), tetrakis(triphenylphosphine)palladium (80.0 mg, 0.045 mmol), and potassium carbonate (276.4 mg, 2.0 mmol) into a Schlenk flask (100 mL). Evacuate and backfill with nitrogen 3 times; Inject 1,2-dimethoxyethane (10 mL) and pure water (2 mL) into the Schlenk flask under a nitrogen atmosphere, ultrasonically vibrate for 20 min, and place it in a 100 o C oil bath and stir for reaction for 72 h. After the reaction is completed, filter to obtain yellow 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)diisophthalaldehyde (222.1 mg), and the yield is 76.4%.

[0041] The nuclear magnetic resonance hydrogen spectrum of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)diisophthalaldehyde obtained in this example is as Figure 1 shown.

[0042] Example 2

[0043] Put 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)diisophthalaldehyde (40.0 mg, 0.10 mmol) obtained in Example 1, 2,5-dimethylpyrazine (21.8 μL, 0.20 mmol), and benzoic anhydride (67.9 mg, 0.30 mmol) into an ampoule (2 mL), and ultrasonically disperse for 20 min. Evacuate and backfill with nitrogen 3 times, seal the ampoule under a vacuum environment, and place it in an 180 o C constant temperature oven for reaction for 7 d. After the reaction is completed, cool to room temperature. The obtained blocky product is ground in a mortar, filtered by suction in a sintered funnel, washed successively with N,N-dimethylformamide and methanol, and then dried in vacuo for 12 h to obtain a dark brown COF-BP material (46.3 mg), and the yield is 78.2%.

[0044] The synthetic route of the pyrazine-based COF-BP material obtained in this example is as Figure 2 shown, and the infrared spectrum is asFigure 3 As shown, the PXRD pattern is as Figure 5 shown, and the nitrogen adsorption - desorption curve is as Figure 7 shown, and the solid - state NMR carbon spectrum is as Figure 9 shown, and the structural general formula is as Figure 13 shown. From the above results, it can be seen that the prepared pyrazine - based COF - BP material has a crystalline framework, regularly arranged pores, and a large specific surface area.

[0045] Example 3

[0046] Put [1,1':4',1"-terphenyl]-3,3",5,5"-tetraformaldehyde (40.0 mg, 0.12 mmol), 2,5 - dimethylpyrazine (26.2 μL, 0.24 mmol), benzoic anhydride (54.3 mg, 0.24 mmol), and benzoic acid (2.9 mg, 0.024 mmol) into an ampoule (2 mL), and ultrasonically disperse for 20 min. Evacuate - backfill with nitrogen 3 times, seal the ampoule under vacuum, and place it in an oven at 180 o °C and react for 7 d. After the reaction, cool to room temperature. The obtained block - shaped product is ground with a mortar and then filtered by suction in a sintered - glass funnel. Wash successively with N,N - dimethylformamide and methanol and then dry under vacuum for 12 h to obtain a yellow COF - TP material (47.3 mg), and the yield is 76.3%.

[0047] The synthetic route of the pyrazine - based COF - TP material obtained in this example is as Figure 2 shown, and the infrared spectrum is as Figure 4 shown, and the PXRD pattern is as Figure 6 shown, and the nitrogen adsorption - desorption curve and BET specific surface area are as Figure 8 shown, and the solid - state NMR carbon spectrum is as Figure 9 shown, and the structural general formula is as Figure 13 shown. From the above results, it can be seen that the prepared pyrazine - based COF - TP material has a crystalline framework, regularly arranged pores, and a large specific surface area.

[0048] Comparative Example 1 Put 5,5'-(benzo[c][1,2,5]oxadiazole - 4,7 - diyl)diisophthalaldehyde (40.0 mg, 0.10 mmol) obtained in Example 1, 2,5 - dimethylpyrazine (21.8 μL, 0.20 mmol), and benzoic anhydride (67.9 mg, 0.30 mmol) into an ampoule (2 mL), and ultrasonically disperse for 20 min. Evacuate - backfill with nitrogen 3 times, seal the ampoule under vacuum, and place it in an oven at 180 oReact in a constant temperature oven at C for 3 d. After the reaction is completed, cool to room temperature. The obtained blocky product is ground in a mortar and then filtered by suction in a sintered funnel. Wash it successively with N,N-dimethylformamide and methanol and then dry it under vacuum for 12 h to obtain a black AMP-BP material (42.4 mg) with a yield of 71.6%.

[0049] Comparative Example 2 Add 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dim isophthalaldehyde (40.0 mg, 0.10 mmol) obtained in Example 1, p-phenylenediamine (21.6 mg, 0.20 mmol), N,N-dimethylacetamide (2 mL), mesitylene (0.5 mL), and acetic acid solution (9 mol / L, 0.3 mL) into an ampoule (5 mL), and ultrasonically disperse for 20 min. Evacuate and backfill with nitrogen 3 times, seal the ampoule under a vacuum environment, and place it in a 120 o React in a constant temperature oven at C for 3 d. After the reaction is completed, cool to room temperature. Filter the obtained product by suction in a sintered funnel, wash it successively with tetrahydrofuran and n-hexane and then dry it under vacuum for 12 h to obtain a yellow powdery COF-IM material (45.1 mg) with a yield of 77.8%.

[0050] Example 4

[0051] Weigh 5 mg of COF-BP, COF-TP, AMP-BP, and COF-IM obtained in Example 2, Example 3, Comparative Example 1, and Comparative Example 2 respectively and place them in a 5 mL round-bottom flask. Add benzyl methyl sulfide (36.0 μL, 0.30 mmol) and methanol (3 mL), and carry out a dark reaction for 30 min. Then, under light conditions (20 W, λ = 465 nm), stir while passing oxygen for 3 h. Centrifuge the obtained product 3 times, take the supernatant, evaporate it by rotary evaporation, and then conduct quantitative analysis by nuclear magnetic resonance hydrogen spectrum.

[0052] The conversion rates of benzyl methyl sulfide catalyzed by the four materials obtained in this example are as Figure 10 shown; the conversion rates of benzyl methyl sulfide catalyzed by COF-IM, AMP-BP, COF-TP, and COF-BP after 3 h of light are 27.5%, 35.9%, 88.5%, and 99.9% respectively.

[0053] Example 5

[0054] Place the COF-BP (5 mg) obtained in Example 2 in a 5 mL round-bottom flask, add benzyl methyl sulfide (36.0 μL, 0.30 mmol), methanol (3 mL), and after reacting in the dark for 30 min, stir while passing oxygen under light conditions (20 W, λ = 465 nm). Take the solutions at reaction times of 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, and 3 h respectively for 1H NMR analysis. The conversion rate of benzyl methyl sulfide catalyzed by the COF-BP obtained in this example is as Figure 11 shown. It can be seen that with the prolongation of time, the conversion rate of benzyl methyl sulfide gradually increases, and after 3 h of photocatalysis, COF-BP can completely oxidize benzyl methyl sulfide to benzyl sulfoxide.

[0055] Example 6

[0056] Place the COF-BP (5 mg) obtained in Example 2 in a 5 mL round-bottom flask, add benzyl methyl sulfide (36.0 μL, 0.30 mmol), methanol (3 mL), and after reacting in the dark for 30 min, stir while passing oxygen under light conditions (20 W, λ = 465 nm) for 3 h. Centrifuge the obtained product 3 times, take the supernatant, rotary evaporate it, and then perform quantitative analysis by 1H NMR. Collect the solid, dry it, and recycle the catalysis 10 times. The conversion rate of benzyl methyl sulfide catalyzed by the COF-BP obtained in this example is as Figure 12 shown. It can be seen that after 10 cycles, COF-BP still has a conversion rate of more than 97% for benzyl methyl sulfide.

[0057] Example 7

[0058] Place the COF-BP (5 mg) obtained in Example 2 in a 5 mL round-bottom flask, add different sulfides (0.30 mmol), methanol (3 mL), and after reacting in the dark for 30 min, stir while passing oxygen under light conditions (20 W, λ = 465 nm) for 3 h or 4 h. Centrifuge the obtained product 3 times, take the supernatant, rotary evaporate it, and then perform quantitative analysis by 1H NMR.

[0059] The conversion rates of pyrazine-based covalent organic framework materials for catalyzing different sulfides are as Figure 14 shown, where 1 represents different sulfide substrates, 2 represents different sulfoxide products, COF-BP represents the catalyst, and 2a - 2p represent different sulfoxide products and their reaction yields. It can be seen that the conversion rates of COF-BP for aromatic sulfides and aliphatic sulfides containing electron-donating and electron-withdrawing groups can basically reach more than 90%, proving that the COF-BP material has broad application prospects in the field of photocatalysis and can be applied to multiple fields such as environmental remediation and green chemistry.

Claims

1. A pyrazine-based covalent organic framework material, characterized in that: The structural general formula of the pyrazine-based covalent organic framework material is as follows: or ； Among them, R 1 , R 2 are each independently selected from one of hydrogen, alkyl, alkoxy, and halogen atoms; X is each independently selected from one of oxygen, sulfur, and selenium atoms; Y is each independently selected from one of carbon and nitrogen atoms.

2. A preparation method of a pyrazine-based covalent organic framework material, characterized in that: It includes the following steps: It is obtained by the Knoevenagel reaction of an aromatic aldehyde monomer and 2,5-dimethylpyrazine; wherein, the general structural formula of the aromatic aldehyde monomer is: , at least one of; wherein, R 1 , R 2 are each independently selected from one of hydrogen, alkyl, alkoxy, and halogen atoms; X are each independently selected from one of oxygen, sulfur, and selenium atoms; Y are each independently selected from one of carbon and nitrogen atoms.

3. The preparation method according to claim 2, wherein: The aromatic aldehyde monomer is at least one of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde and [1,1':4',1"-terphenyl]-3,3",5,5"-tetraaldehyde.

4. The preparation method according to claim 3, characterized in that: The preparation method of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde includes: Mix 3,5-diformylphenylboronic acid pinacol ester, 4,7-dibromobenzo[c][1,2,5]oxadiazole, tetrakis(triphenylphosphine)palladium, potassium carbonate, pure water and 1,2-dimethoxyethane, and then stir and react to obtain it.

5. The preparation method according to claim 3, characterized in that: The Knoevenagel reaction system also includes benzoic anhydride and / or benzoic acid.

6. The preparation method according to claim 5, characterized in that: In the Knoevenagel reaction system, the molar ratio of 5,5'-(benzo[c][1,2,5]oxadiazole-4,7-diyl)dimesitylaldehyde, 2,5-dimethylpyrazine and benzoic anhydride is 1:2:

3.

7. The preparation method according to claim 5, characterized in that: In the Knoevenagel reaction system, the molar ratio of [1,1':4',1"-terphenyl]-3,3",5,5"-tetraaldehyde, 2,5-dimethylpyrazine, benzoic anhydride and benzoic acid is 1:2:2:0.

2.

8. The preparation method according to claim 2, wherein: The reaction conditions of the von Braun reaction are as follows: the reaction temperature is 180~200 o °C, and the reaction time is 5~7 days.

9. Use of a pyrazine-based covalent organic framework material as described in claim 1 in the field of photocatalytic oxidation.

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