Pyrazinyl monomer and preparation method and application of covalent organic framework material of pyrazinyl monomer

Abstract

The invention belongs to the technical field of organic framework materials, and particularly relates to a pyrazinyl monomer and a preparation method and application of a covalent organic framework material of the pyrazinyl monomer. Three nitrogen-rich methyl monomers containing pyrazine groups are designed and synthesized, the monomers and aromatic dialdehyde can be subjected to a condensation reaction to form a series of vinyl covalent organic frameworks (COFs), and the prepared three nitrogen-rich vinyl COFs can be applied to the field of gas adsorption and separation.

Description

Technical Field

[0001] The invention belongs to the technical field of organic framework materials, and specifically relates to a preparation method and application of a pyrazine-based monomer and a covalent organic framework material thereof. Background Art

[0002] Covalent organic frameworks (COFs) are an emerging class of porous crystalline polymers that precisely integrate organic units into highly ordered network structures. 2 -C-linked COFs (olefin-linked or vinyl-linked) have attracted much attention due to their π-electron conjugated structure and irreversibility. However, vinyl COFs are relatively less developed compared to other types of COFs (such as imine COFs). This is because the carbon-carbon double bonds in the skeleton are mainly prepared by condensation reactions between methyl or methylene groups and aldehyde groups in the presence of specific catalysts, and the COFs currently used to synthesize vinyl links are very limited. Therefore, it is necessary to design more suitable monomers to enrich the types of vinyl COFs.

[0003] COFs have a high specific surface area, ordered structure and adjustable pore size, which has aroused great research interest in the field of gas separation. By introducing N atoms into the structure, the host-guest interaction between C2H2 molecules and N atoms is increased, thus achieving efficient separation of C2H2 / CO2. Summary of the invention

[0004] The purpose of the present invention is to provide a compound containing pyrazine groups and a covalent organic framework material and a preparation method thereof in view of the deficiencies of the prior art. The present invention designs three nitrogen-rich methyl monomers containing pyrazine groups, namely: DPZ, TPZ and HMB. Such monomers can undergo condensation reactions with aromatic dialdehydes to form a series of vinyl covalent organic frameworks (COFs).

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: A pyrazine-based monomer, wherein the pyrazine-based monomer is one of DPZ, TPZ and HMB, and has the following chemical structural formula: , , .

[0006] The preparation method of DPZ comprises the following steps: using 1,2,4,5-benzenetetraamine tetrahydrochloride as a raw material, reacting with 2,3-butanedione, sodium acetate and ethanol for 24 hours, filtering, and washing the reaction product with water and ethanol in sequence to obtain 2,3,7,8-tetramethylpyrazine[2,3-g]quinoxaline, namely DPZ; the molar ratio of the raw material to 2,3-butanedione and sodium acetate is 1:20:4.

[0007] The preparation method of TPZ monomer comprises the following steps: (1) Using 1,2,4,5-benzenetetramine tetrahydrochloride as a raw material, adding sodium acetate, and reacting in an air atmosphere to obtain an intermediate 2,3,7,8-phenazinetetramine trihydrochloride; (2) The intermediate 2,3,7,8-phenazinetetraamine trihydrochloride, 2,3-butanedione, sodium acetate and ethanol are reacted for 24 hours, filtered, and the reaction product is washed with water and ethanol in sequence to obtain 2,3,9,10-tetramethylpyrazine [2,3-b:2',3'i] phenazine, namely TPZ; the molar ratio of the intermediate to 2,3-butanedione and sodium acetate is 1:20:4.

[0008] The preparation method of HMB monomer is as follows: 2,3,6,7,10,11-hexaaminotriphenyl hexahydrochloride is used as a starting material, reacted with 2,3-butanedione, sodium acetate and ethanol for 24 hours, filtered, and the reaction product is washed with water and ethanol in sequence to obtain 2,3,8,9,14,15-hexamethylbenzo[1,2-g:3,4-g':5,6g'']triquinoxaline, which is HMB; the molar ratio of the raw material to 2,3-butanedione and sodium acetate is 1:30:6.

[0009] A covalent organic framework material is obtained by condensing any of the above pyrazine-based monomers with an aromatic dialdehyde.

[0010] Furthermore, the aromatic dialdehyde is terephthalaldehyde, and the molar ratio of the aldehyde group in the aromatic dialdehyde to the methyl group in the pyrazine monomer is 1:1.

[0011] Furthermore, the structure of the covalent organic framework material is as follows:

[0012] .

[0013] Furthermore, the specific surface area of ​​the organic framework material is 532.6-1246.4 m 2 / g.

[0014] The above-mentioned covalent organic framework material is used in gas adsorption separation, wherein the gases are C2H2 and CO2.

[0015] The beneficial effects of the present invention are: (1) The present invention can prepare three pyrazine group monomers through simple experimental steps without further purification.

[0016] (2) The three monomers prepared can all be used to obtain vinyl covalent organic frameworks through melt polycondensation, which broadens the types of vinyl covalent organic frameworks.

[0017] (3) The three prepared vinyl COFs have abundant N sites and show good gas selectivity for acetylene (C2H2) and carbon dioxide (CO2) mixtures. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 For DPZ 1 H-NMR spectrum.

[0019] Figure 2 For TPZ 1 H-NMR spectrum.

[0020] Figure 3 For HMB 1 H-NMR spectrum.

[0021] Figure 4 Schematic diagram of the synthesis of three COFs.

[0022] Figure 5 This is the topological structure diagram of DPZ-COF, where gray: C; blue: N; white: H.

[0023] Figure 6 This is the topological structure diagram of TPZ-COF, where gray: C; blue: N; white: H.

[0024] Figure 7 This is the topological structure diagram of HMB-COF, where gray: C; blue: N; white: H.

[0025] Figure 8 Thermogravimetric analysis spectra of DPZ-COF, TPZ-COF and HMB-COF under nitrogen.

[0026] Fig. 9 This is the BET diagram of DPZ-COF.

[0027] Fig.10 This is the BET diagram of TPZ-COF.

[0028] Fig.11 This is the BET diagram of HMB-COF.

[0029] Fig.12 This is the gas adsorption curve of DPZ-COF.

[0030] Fig.13 This is the gas adsorption curve of TPZ-COF.

[0031] Fig.14 Gas adsorption curve of HMB-COF.

[0032] Fig.15IAST gas selectivity curves of DPZ-COF, TPZ-COF and HMB-COF. DETAILED DESCRIPTION

[0033] In order to further disclose but not limit the present invention, the present invention is further described in detail below with reference to examples.

[0034] Example 1 Synthesis of DPZ (1) Under nitrogen atmosphere, 1,2,4,5-benzenetetraamine tetrahydrochloride (2.84 g, 10 mmol) was used as the starting material, and 2,3-butanedione (17 mL, 0.2 mol) and sodium acetate (3.3 g, 40 mmol) were refluxed in ethanol (250 mL) for 24 h, cooled to room temperature, filtered, and the reaction product was washed with water and ethanol in turn to obtain 2,3,7,8-tetramethylpyrazine [2,3-g] quinoxaline (DPZ) with a yield of 46.2%. The NMR data are 1 H-NMR (500 MHz, chloroform-d) δ (ppm): 2.84 (s, 12 H), 8.67 (s, 2 H).

[0035] The reaction equation is as follows:

[0036] Example 2 Synthesis of TPZ (1) 1,2,4,5-benzenetetramine tetrahydrochloride (0.642 g, 2.26 mmol) was used as the starting material. Sodium acetate (2.6 g, 31.64 mmol) and water (30 mL) were added and refluxed under compressed air for 5 h. The mixture was cooled to room temperature and filtered. The product was washed with water to obtain the intermediate product 2,3,7,8-phenazinetetramine trihydrochloride with a yield of 40.5%.

[0037] (2) The intermediate 2,3,7,8-phenazine tetraamine trihydrochloride (0.314 g, 0.9 mmol) was refluxed in ethanol (30 mL) for 24 h, cooled to room temperature, filtered, and the reaction product was washed with water and ethanol in turn to obtain 2,3,9,10-tetramethylpyrazine [2,3-b:2',3'i] phenazine (TPZ) with a yield of 98%. The NMR data are 1 H-NMR (500 M Hz, TFA-d) δ (ppm): 2.98 (s, 12 H), 7.67 (s, 4 H).

[0038] The reaction equation is as follows:

[0039] Example 3 Synthesis of HMB (1) Under nitrogen atmosphere, 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride (0.537 g, 1 mmol) was used as the starting material, and 2,3-butanedione (2.6 mL, 30 mmol) and sodium acetate (0.492 g, 6 mmol) were refluxed in ethanol (60 mL) for 24 h, cooled to room temperature, filtered, and the product was washed with water and ethanol to obtain 2,3,8,9,14,15-hexamethylbenzo[1,2-g:3,4-g':5,6g'']triquinoxaline (HMB) with a yield of 96.7%. The NMR data are 1 H-NMR (500 M Hz, TFA-d) delta (ppm): 3.34 (s, 18 H), 9.91 (s, 6 H).

[0040] The reaction equation is as follows:

[0041] Example 4 Synthesis of DPZ-COF DPZ (0.1 mmol, 23.8 mg), terephthalaldehyde (0.2 mmol, 26.8 mg), and benzoic anhydride (0.4 mmol, 90.5 mg) were added to a 5 mL Pyrex tube. The mixture was flash frozen at 77 K (using a liquid nitrogen bath) and then degassed by three freeze-pump-thaw cycles. It was then sealed in vacuum using a Schlenk line and an oil pump. The tube containing the mixture was heated to 200 ˚C for 5 days. After cooling to room temperature, the precipitate was collected by filtration and then washed with acetone and methanol in sequence. It was then Soxhlet extracted with tetrahydrofuran for 24 hours and dried in vacuum at 60 ˚C overnight to obtain 45.2 mg of dark brown powder with a yield of approximately 89%.

[0042] Example 5 Synthesis of TPZ-COF TPZ (0.05 mmol, 17 mg), terephthalaldehyde (0.1 mmol, 13.4 mg), and benzoic anhydride (0.2 mmol, 45.2 mg) were added to a 5 mL Pyrex tube. The mixture was flash frozen at 77 K (using a liquid nitrogen bath) and then degassed by three freeze-pump-thaw cycles. It was then sealed in vacuum using a Schlenk line and an oil pump. The Pyrex tube containing the mixture was heated to 180 ˚C for 5 days. After cooling to room temperature, the precipitate was collected by filtration, washed with acetone and methanol in sequence, and then Soxhlet extracted with tetrahydrofuran for 24 hours and dried overnight in vacuum at 60 ˚C to obtain 26 mg of dark brown powder with a yield of about 85%.

[0043] Example 6 Synthesis of HMB-COF HMB (0.04 mmol, 18.7 mg), terephthalaldehyde (0.12 mmol, 16.1 mg), and benzoic anhydride (0.24 mmol, 54.3 mg) were added to a 5 mL Pyrex tube. The mixture was flash frozen at 77 K (using a liquid nitrogen bath) and then degassed by three freeze-pump-thaw cycles. Subsequently, it was sealed in vacuum using a Schlenk line and an oil pump. The Pyrex tube containing the mixture was heated to 200 ˚C for 5 days. After cooling to room temperature, the precipitate was collected by filtration, washed with acetone and methanol in sequence, and then Soxhlet extracted with tetrahydrofuran for 24 hours and dried overnight in vacuum at 60 ˚C to obtain 32 mg of dark red powder with a yield of about 92%.

[0044] Figure 1-3 The three monomers of DPZ, TPZ and HMB synthesized in Examples 1-3 are 1 H-NMR spectrum, which shows the successful synthesis of three monomers.

[0045] Figure 4 The synthesis diagram of three COFs, DPZ-COF, TPZ-COF and HMB-COF, synthesized in Examples 4-6.

[0046] Figure 5-7 The topological structures of DPZ-COF, TPZ-COF and HMB-COF synthesized in Examples 4-6 are shown respectively. The results show that the three COFs are in AA stacking form.

[0047] Figure 8 Thermogravimetric curves of the three COFs, DPZ-COF, TPZ-COF and HMB-COF, synthesized in Examples 4-6 show that all COFs maintain good stability at temperatures below 400°C.

[0048] Figure 9-11 The nitrogen adsorption isotherms of the three COFs, DPZ-COF, TPZ-COF and HMB-COF, synthesized in Examples 4-6 show that the prepared COFs have a porous structure with a BET specific surface area of ​​876.6 m 2 / g,1246.4m 2 / g and 532.63 m 2 / g.

[0049] The three COFs DPZ-COF, TPZ-COF and HMB-COF synthesized in Examples 4-6 were used for the adsorption and separation of C2H2 and CO2. The specific steps were as follows: the adsorption isotherms of C2H2 and CO2 were collected using a specific surface area analyzer (BET). During the test, the dosage of DPZ-COF, TPZ-COF and HMB-COF was 50 mg.

[0050] Figure 12-14 The adsorption isotherms of the three COFs DPZ-COF, TPZ-COF and HMB-COF synthesized in Examples 4-6 for C2H2 and CO2 at room temperature (298 K). The results show that the adsorption amount of C2H2 by the three COFs is significantly higher than that of CO2, which is beneficial for gas separation applications.

[0051] Fig.15 The ideal adsorption solution theory (IAST) calculations of the three COFs DPZ-COF, TPZ-COF and HMB-COF synthesized in Examples 4-6 for two-component C2H2 / CO2 (50% / 50%) at 298 K. All three COFs are rich in N sites and can therefore be used in the field of gas adsorption separation. Compared with DPZ-COF, the increase in N atoms in the pores of TPZ-COF and HMB-COF is conducive to the improvement of IAST selectivity.

[0052] The above description is only a preferred embodiment of the present invention. All changes and modifications made within the scope of the patent application of the present invention are within the scope of the present invention.

Claims

1. A pyrazine monomer, characterized in that: The pyrazine monomer is one of DPZ, TPZ and HMB, and the chemical structure is as follows: ， ， 。 2. A method for preparing a pyrazine-based monomer as claimed in claim 1, characterized in that: 1,2,4,5-benzenetetraamine tetrahydrochloride is used as a raw material, reacted with 2,3-butanedione, sodium acetate and ethanol for 24 hours, filtered, and the reaction product is washed with water and ethanol in turn to obtain 2,3,7,8-tetramethylpyrazine [2,3-g] quinoxaline, namely DPZ; the molar ratio of the raw material to 2,3-butanedione and sodium acetate is 1:20:

4.

3. A method for preparing a pyrazine-based monomer as claimed in claim 1, characterized in that: The preparation method of TPZ monomer comprises the following steps: (1) Using 1,2,4,5-benzenetetramine tetrahydrochloride as a raw material, adding sodium acetate, and reacting in an air atmosphere to obtain an intermediate 2,3,7,8-phenazinetetramine trihydrochloride; (2) The intermediate 2,3,7,8-phenazinetetraamine trihydrochloride, 2,3-butanedione, sodium acetate and ethanol are reacted for 24 hours, filtered, and the reaction product is washed with water and ethanol in sequence to obtain 2,3,9,10-tetramethylpyrazine [2,3-b:2',3'i] phenazine, namely TPZ; the molar ratio of the intermediate to 2,3-butanedione and sodium acetate is 1:20:

4.

4. A method for preparing a pyrazine-based monomer as claimed in claim 1, characterized in that: 2,3,6,7,10,11-hexaaminotriphenyl hexahydrochloride is used as a starting material, reacted with 2,3-butanedione, sodium acetate and ethanol for 24 hours, filtered, and the reaction product is washed with water and ethanol in sequence to obtain 2,3,8,9,14,15-hexamethylbenzo[1,2-g:3,4-g':5,6g'']triquinoxaline, namely HMB; the molar ratio of the raw material to 2,3-butanedione and sodium acetate is 1:30:

6.

5. A covalent organic framework material, characterized in that: The covalent organic framework material is obtained by condensing any pyrazine monomer described in claim 1 with an aromatic dialdehyde; the molar ratio of the aldehyde group in the aromatic dialdehyde to the methyl group in the pyrazine monomer is 1:

1.

6. The covalent organic framework material according to claim 5, characterized in that: The aromatic dialdehyde is terephthalaldehyde.

7. The covalent organic framework material according to claim 5, characterized in that: The structure of the covalent organic framework material is as follows: ， ， 。 8. The covalent organic framework material according to claim 5, characterized in that: The specific surface area of ​​the organic framework material is 532.6-1246.4 m 2 / g.

9. Use of the covalent organic framework material according to claim 5 in gas adsorption separation, characterized in that: The gases are C2H2 and CO2.

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