Three-dimensional azobenzene functionalized covalent organic framework intelligent response material and preparation method thereof

Abstract

The invention is applicable to the technical field of intelligent response materials, and provides a three-dimensional azobenzene functionalized covalent organic framework intelligent response material and a preparation method thereof. The three-dimensional azobenzene functionalized covalent organic framework intelligent response material is prepared by uniformly grinding 3, 3 ', 5'-tetra [(3 ', 5'-diformylphenyl)]-hexamethyl biphenyl and azobenzene-4, 4 '-diaminotriphenylamine, adding an organic solvent, adding a catalyst acetic acid aqueous solution, quickly freezing, emptying air, sealing with flame, heating after recovering to room temperature, and obtaining the three-dimensional azobenzene functionalized covalent organic framework intelligent response material. According to the invention, the azobenzene functionalized covalent organic framework material with a bcu topological structure is synthesized; the material has excellent photostimulation response CO2 adsorption performance; reversible control of CO2 adsorption capacity can be realized through ultraviolet light and heating conditions, at least five times of circulation can be maintained, and good circulation stability is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent responsive materials, and particularly relates to a three-dimensional azobenzene-functionalized covalent organic framework intelligent responsive material and a preparation method thereof. Background Art

[0002] Intelligent responsive materials can produce flexible self-adaptive responses under external stimuli such as light, temperature, pH, pressure, etc., and thus can be applied in various fields such as oil-water separation, biosensors, drug delivery, intelligent windows, etc., which has attracted great attention. COFs (covalent organic framework materials) have a well-defined topological structure, ordered channels, and a pre-designed adjustable structure, which is conducive to the precise reversible control of the structure of stimulus-responsive materials; azobenzene and its derivatives have become well-known photochromic molecules due to their stability, and they can undergo clean, rapid, and efficient reversible photoisomerization. Currently, there are only relevant studies on azobenzene and its derivatives in two-dimensional COFs, but the two-dimensional structure has only one-dimensional channels and a low specific surface area, which limits the performance and practical applications of the materials. If it is extended to 3D COFs, the utilization rate of azobenzene functional sites can be greatly improved, and its performance can be enhanced. Summary of the Invention

[0003] The purpose of the embodiment of the present invention is to provide a three-dimensional azobenzene-functionalized covalent organic framework intelligent responsive material, aiming to solve the problems proposed in the above background art.

[0004] The embodiment of the present invention is implemented as follows. The three-dimensional azobenzene-functionalized covalent organic framework intelligent responsive material has the following structural formula:

[0005]

[0006] Another purpose of the embodiment of the present invention is to provide a preparation method of a three-dimensional azobenzene-functionalized covalent organic framework intelligent responsive material, including the following steps:

[0007] After grinding 3,3',5,5'-tetrakis[(3”,5”-diformylphenyl)]-hexamethylbiphenyl and azobenzene-4,4”-diaminotriphenylamine evenly, an organic solvent is added, and then an aqueous solution of acetic acid as a catalyst is added, followed by rapid freezing, evacuating air and flame sealing, and then heating after returning to room temperature to obtain a three-dimensional azobenzene-functionalized covalent organic framework intelligent responsive material.

[0008] Preferably, the molar ratio of 3,3',5,5'-tetrakis[(3”,5”-diformylphenyl)]-hexamethylbiphenyl to azobenzene-4,4”-diaminotriphenylamine is 1:4 - 4.2; more preferably 1:4.

[0009] Preferably, the organic solvent is a mixed solvent of mesitylene and 1,4-dioxane, and the mixed volume ratio of mesitylene to 1,4-dioxane is 1:0.3 - 0.45; more preferably 1:0.43.

[0010] Preferably, the concentration of the aqueous acetic acid solution is 3 - 12 mol / L; more preferably 6 mol / L.

[0011] Preferably, the heating temperature is 85 - 150 °C and the time is 3 - 7 days; more preferably 120 °C and 5 days.

[0012] Preferably, the preparation method of 3,3',5,5'-tetrakis[(3'',5''-diformylphenyl)]-hexamethylbiphenyl comprises the following steps:

[0013] Add 3,3',5,5'-tetraiodo-hexamethylbiphenyl, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) isophthalaldehyde, bis(triphenylphosphine)palladium diacetate, and potassium carbonate into ultra-dry tetrahydrofuran and deoxygenated water in an environment of a constant-temperature oil bath, react under a nitrogen atmosphere. After the reaction, remove the solvent under reduced pressure, add dichloromethane, then wash, dry and filter the organic phase, and remove the solvent by rotary evaporation under reduced pressure to obtain a crude product. After purification, 3,3',5,5'-tetrakis[(3'',5''-diformylphenyl)]-hexamethylbiphenyl is obtained.

[0014] Preferably, the molar ratio of 3,3',5,5'-tetraiodo-hexamethylbiphenyl, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) isophthalaldehyde, bis(triphenylphosphine)palladium diacetate, and potassium carbonate is 1:4 - 5:0.25:25 - 27.

[0015] Preferably, the reaction temperature is 80 °C and stir for 3 days.

[0016] The three-dimensional azobenzene-functionalized covalent organic framework intelligent response material provided by the embodiments of the present invention condenses a linear diamine building unit with an azobenzene functional structure and a three-dimensional octahedral-connected aldehyde-based building unit based on hexamethylbiphenyl to synthesize a novel azobenzene-functionalized covalent organic framework material with a bcu topological structure, which has high crystallinity, permanent porosity and good thermal stability. Moreover, due to the introduction of azobenzene functional groups, the covalent organic framework obtained in the embodiments of the present invention has a photo-stimulated CO2 adsorption performance. Its CO2 adsorption capacity at 273 K and 1 standard atmospheric pressure is 45.11 cm 3 , 3 , ,

[0016] / g. Under ultraviolet light stimulation, its CO2 adsorption capacity can reach 67.52 cm 3 / g. After heating at 120 °C, it can return to the original CO2 adsorption capacity and can maintain at least five cycles, having good cycle stability. Brief Description of the Drawings

[0017] Figure 1 Powder X-ray diffraction pattern of JUC-687 prepared in Example 1 of the present invention;

[0018] Figure 2 Fourier transform infrared spectra of JUC-687, raw material monomer TDFBM and DTPA-Azo prepared in Example 1 of the present invention;

[0019] Figure 3 Thermogravimetric analysis diagram of JUC-687 prepared in Example 1 of the present invention;

[0020] Figure 4 Nitrogen adsorption diagram of JUC-687 prepared in Example 1 of the present invention;

[0021] Figure 5 Scanning electron microscope image of JUC-687 prepared in Example 1 of the present invention;

[0022] Figure 6 Solid ultraviolet diffuse reflection spectrum of JUC-687 prepared in Example 1 of the present invention;

[0023] Figure 7 CO2 gas adsorption diagrams of JUC-687 prepared in Example 1 of the present invention under 365 nm ultraviolet light irradiation and under normal conditions;

[0024] Figure 8 CO2 gas adsorption capacity cycle diagram of JUC-687 prepared in Example 1 of the present invention under 365 nm ultraviolet light irradiation and heating conditions. Detailed Description of the Invention

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] A three-dimensional azobenzene-functionalized covalent organic framework intelligent response material, and its preparation method includes the following steps:

[0027] (1) Prepare 3,3',5,5'-tetrakis[(3'',5'-diformylphenyl)]-hexamethylbiphenyl, and its chemical structural formula is as shown below:

[0028]

[0029] Its synthesis route is as shown below:

[0030]

[0031] In a glove box, 3,3',5,5'-tetraiodo-hexamethylbiphenyl, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) isophthalaldehyde, bis(triphenylphosphine)palladium diacetate, and potassium carbonate were successively added to a round-bottom flask. The round-bottom flask was fixed in a thermostatic oil bath. After adding ultra-dry tetrahydrofuran and deoxygenated water, the reaction was carried out under a nitrogen atmosphere. After the reaction, the solvent was removed under reduced pressure. Dichloromethane was added to dissolve the product, and then it was washed with deionized water and saturated brine respectively. The organic phase was dried over anhydrous sodium sulfate and filtered. The solvent was removed by rotary evaporation under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (dichloromethane / n-hexane, 2:1, v / v) to obtain 3,3',5,5'-tetrakis[(3'',5''-diformylphenyl)]-hexamethylbiphenyl;

[0032] (2) Preparation of an azobenzene-functionalized three-dimensional covalent organic framework intelligent responsive material, the structural formula of which is as follows:

[0033]

[0034] The synthetic route is as follows:

[0035]

[0036] The three-dimensional octanode building unit 3,3',5,5'-tetrakis[(3'',5''-diformylphenyl)]-hexamethylbiphenyl and the linear di-linking building unit azobenzene-4,4''-diaminotriphenylamine were ground evenly in a mortar and then added to a heat-resistant glass tube. An organic solvent was added, and then an aqueous acetic acid solution of a catalyst was added. The heat-resistant glass tube was quickly frozen in a liquid nitrogen bath, evacuated and flame-sealed, and then placed in a constant-temperature oven for heating after returning to room temperature to obtain the azobenzene-functionalized three-dimensional covalent organic framework material (JUC-687).

[0037] The following specifically describes the specific implementation of the present invention in combination with specific embodiments.

[0038] Example 1. A three-dimensional azobenzene-functionalized covalent organic framework intelligent responsive material, and its preparation method includes the following steps:

[0039] (1) 3,3',5,5'-tetraiodo-hexamethylbiphenyl (2.0 g, 2.7 mmol), bis(triphenylphosphine)palladium(II) diacetate (Pd[(PPh3)]2Ac2) (500 mg, 0.67 mmol), potassium carbonate (K2CO3) (10 g, 72 mmol), and 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) isophthalaldehyde (3.5 g, 13.4 mmol) were added to 80.0 mL of tetrahydrofuran (THF) and 20.0 mL of H2O. The mixture was stirred at 80 °C under a N2 atmosphere for 3 days. After removing the solvent, the remaining product was dissolved in CH2Cl2 (120 mL) and washed successively with H2O (120 mL) and saturated NaCl solution (120 mL). The organic phase was filtered and purified by silica gel column chromatography using dichloromethane / n-hexane (2:1, v / v) as the eluent. The obtained product was recrystallized from CH2Cl2 / methanol to give a white solid compound, namely 3,3',5,5'-tetrakis[(3'',5'-formylphenyl)]-hexamethylbiphenyl, with a yield of 72%;

[0040] (2) 3,3',5,5'-tetrakis[(3'',5'-formylphenyl)]-hexamethylbiphenyl (TDFBM, 13.8 mg, 0.018 mmol) and azobenzene-4,4''-diaminotriphenylamine (DTPA-Azo, 26.2 mg, 0.072 mmol) were ground evenly in a mortar and then added to a glass tube. Then, 0.7 mL of mesitylene, 0.3 mL of 1,4-dioxane, and 0.1 mL of acetic acid (6 mol / L) were slowly added. The glass tube was frozen in liquid nitrogen, evacuated, and sealed under a methane / oxygen flame. Finally, it was placed in an oven at 120 °C and heated for 5 days. After the reaction was completed, the glass tube was opened with a glass cutter, and the product was washed three times each with tetrahydrofuran and acetone, and then filtered. The solid product was dried in a vacuum drying oven at 75 °C for 8 hours to obtain the red target product, namely azobenzene-functionalized three-dimensional covalent organic framework material JUC-687, with a yield of 76%.

[0041] Performance test:

[0042] The red target product prepared in Example 1 was subjected to X-ray diffraction analysis. The obtained X-ray diffraction pattern was compared with the powder X-ray diffraction pattern simulated by Materials Studio software, and the results are as Figure 1 shown. According to Figure 1 it can be seen that the three-dimensional covalent organic framework material of the established target was synthesized in the example of the present invention;

[0043] The two building units TDFBM and DTPA-Azo and the prepared JUC-687 were subjected to spectral analysis, and the Fourier transform infrared spectrum was obtained asFigure 2 As shown, the disappearance of the -NH2 absorption peak of DTPA-Azo at 3439 - 3352 cm -1 and the -CHO absorption peak of TDFBM at 1700 cm -1 while the appearance of the infrared absorption peak of -C=N of JUC-687 at 1620 cm -1 proved the formation of imine bonds;

[0044] Thermogravimetric analysis was performed on JUC-687 prepared in Example 1, and the results are as Figure 3 shown. The weight loss of JUC-687 starting at 400 - 450 °C was due to the decomposition of the azobenzene functional group. Until around 500 °C, the COF framework began to collapse and there was another obvious weight loss, indicating that JUC-687 could withstand high temperatures of 400 °C;

[0045] Nitrogen adsorption analysis was performed on JUC-687 prepared in Example 1, and the results are as Figure 4 shown. The N2 adsorption of JUC-687 proved that the specific surface area of JUC-687 reached 1114.8 m 2 g -1 , and the pore size was microporous, mainly distributed around 1.0 nm and 1.88 nm;

[0046] Scanning electron microscopy analysis was performed on JUC-687 prepared in Example 1, and the results are as Figure 5 shown. It can be seen that the morphology of JUC-687 was a uniform rod-like shape with a size of about 500 nm;

[0047] Solid ultraviolet diffuse reflectance spectroscopy analysis was performed on JUC-687 prepared in Example 1, and the results are as Figure 6 shown. It can be seen that after irradiation with ultraviolet light at 365 nm, the solid ultraviolet characteristic peaks in the range of 400 nm decreased significantly, proving the isomerization of the azobenzene functional group in the JUC-687 material;

[0048] CO2 gas adsorption comparative analysis was performed on JUC-687 prepared in Example 1 under irradiation with ultraviolet light at 365 nm and under normal conditions, and the results are as Figure 7 shown. It can be seen that JUC-687 could adsorb up to 45.11 cm 3 / g of CO2 under the conditions of 273 K and 1 bar. After irradiation with ultraviolet light at 365 nm, the maximum amount of CO2 that could be adsorbed became 67.52 cm 3 / g;

[0049] The cyclic comparative analysis of the CO2 gas adsorption capacity of JUC-687 prepared in Example 1 was carried out under 365 nm ultraviolet light irradiation and heating conditions, and the results are as follows Figure 8 As shown, JUC-687 can achieve an intelligent response to the CO2 adsorption capacity under both 365 nm ultraviolet light irradiation and heating conditions, and can maintain at least 5 cycles of performance without obvious attenuation. For U-mazo in the prior art, it can also achieve the conversion of CO2 adsorption capacity under ultraviolet light and heating conditions. After 3 cycles, the efficiency decreases slightly (J. Mater. Chem. A, 2022, 10, 8303–8308). The performance of the material prepared in the embodiment of the present invention has been improved.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-dimensional azobenzene-functionalized covalent organic framework intelligent response material, characterized in that, The structural formula of the said material is as follows:

2. A preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material as described in claim 1, characterized in that, It includes the following steps: After grinding 3,3',5,5'-tetrakis[(3”,5”-diformylphenyl)]-hexamethylbiphenyl and azobenzene-4,4”-diaminotriphenylamine evenly, an organic solvent is added, then an aqueous acetic acid solution as a catalyst is added, followed by rapid freezing. After evacuating the air and flame-sealing, it is heated after returning to room temperature to obtain a three-dimensional azobenzene-functionalized covalent organic framework intelligent response material.

3. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 2, wherein, The molar ratio of 3,3',5,5'-tetrakis[(3”,5”-diformylphenyl)]-hexamethylbiphenyl to azobenzene-4,4”-diaminotriphenylamine is 1:4 - 4.

2.

4. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 2, characterized in that, The organic solvent is a mixed solvent of mesitylene and 1,4-dioxane, and the mixed volume ratio of mesitylene to 1,4-dioxane is 1:0.3 - 0.

45.

5. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 2, characterized in that The concentration of the aqueous acetic acid solution is 3 - 12 mol / L.

6. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 2, characterized in that, The temperature of the said heating is 85 - 150 °C, and the time is 3 - 7 days.

7. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 2, characterized in that, The preparation method of 3,3',5,5'-tetrakis[(3”,5”-diformylphenyl)]-hexamethylbiphenyl includes the following steps: 3,3',5,5'-tetraiodo-hexamethylbiphenyl, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)isophthalaldehyde, bis(triphenylphosphine)palladium diacetate, and potassium carbonate are added to ultradry tetrahydrofuran and deoxygenated water in an environment of a constant-temperature oil bath, and the reaction is carried out under a nitrogen atmosphere. After the reaction, the solvent is removed under reduced pressure, dichloromethane is added, followed by washing, drying, and filtering the organic phase. The solvent is removed by rotary evaporation under reduced pressure to obtain a crude product. After purification, 3,3',5,5'-tetrakis[(3”,5”-diformylphenyl)]-hexamethylbiphenyl is obtained.

8. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 7, characterized in that, The molar ratio of 3,3',5,5'-tetraiodo-hexamethylbiphenyl, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)isophthalaldehyde, bis(triphenylphosphine)palladium diacetate, and potassium carbonate is 1:4 - 5:0.25:25 - 27.

9. The preparation method of the three-dimensional azobenzene-functionalized covalent organic framework intelligent response material according to claim 7, characterized in that, The temperature of the said reaction is 80 °C, and it is stirred for 3 days.

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