An acylhydrazone-based covalent organic framework material, its preparation method and application

Abstract

The present invention relates to a hydrazone-based covalent organic framework material, a preparation method thereof and an application thereof. An electrically neutral hydrazone-based covalent organic framework material (n-COF) is synthesized through a Schiff base reaction, and the transformation of the charge property of the framework material skeleton is realized by adjusting the acidity and alkalinity of the solution. The synthesized electrically neutral framework material has high chemical stability, is protonated under acidic conditions to obtain a positively charged framework material (c-COF), and is deprotonated under alkaline conditions to obtain a negatively charged framework material (a-COF). The hydrazone-based covalent organic framework material of the present invention has the property of adjustable framework charge and has potential application value in the fields of pollutant adsorption and photocatalytic degradation.

Description

Technical Field

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

[0002] Water pollution, especially from industrial pollutants such as synthetic dyes, heavy metals, and organic compounds, poses significant environmental and health risks. Traditional water treatment methods, including physical adsorption and chemical degradation, often fail to effectively treat complex mixtures of pollutants that vary in charge, size, and chemical composition. To overcome these limitations, increasing research has focused on developing advanced materials that can selectively capture and degrade pollutants under different conditions. Therefore, the development of a multifunctional material that can integrate physical adsorption and photocatalytic degradation is a research focus in the field of environmental remediation.

[0003] Covalent organic frameworks are a class of crystalline porous polymers formed by the covalent bonding of organic building blocks. As a new type of crystalline porous material, hydrazone-based covalent organic frameworks have great potential in various applications due to their structural features such as high surface area, adjustable pore channels, heteroatom sites, good stability, and easy functionalization, such as adsorption / separation, chemical sensing, catalysis, and energy storage. Therefore, a postsynthetic modification strategy can be used to transform the neutral framework into an ionic framework, thereby achieving efficient adsorption and photocatalytic degradation of organic dyes with different charge characteristics. Summary of the Invention

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

[0005] The present invention provides a hydrazone-based covalent organic framework material, which is a neutral framework material, and its structural general formula is as follows:

[0006] ; wherein, R 1 , R 2 , R 3 , R 4 are each independently selected from one of hydrogen, alkyl, and alkoxy.

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

[0008] 5,5'- (benzene[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl)) diisophthalaldehyde and terephthalohydrazide monomer compound are subjected to a Schiff base reaction to obtain the hydrazone-based covalent organic framework material.

[0009] Preferably, the structural general formula of the terephthalohydrazide monomer compound is as follows:

[0010] ; wherein, R 1 、R 2 、R 3 、R 4 are each independently selected from one of hydrogen, alkyl, and alkoxy. Preferably, R 1 、R 3 are ethoxy groups, and R 2 、R 4 are hydrogen atoms.

[0011] Furthermore, the Schiff base reaction system further includes a solvent and an acid catalyst; the solvent is n-butanol and 1,2-dichlorobenzene, and the acid catalyst is acetic acid solution. Preferably, the volume ratio of n-butanol, 1,2-dichlorobenzene, and acetic acid solution is 8:2:1.

[0012] Furthermore, the molar ratio of 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde to the terephthalohydrazide monomer compound is 1:2.

[0013] Furthermore, the Schiff base reaction temperature is 100 - 150 o °C, and the reaction time is 48 - 72 h.

[0014] Furthermore, the preparation method of 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde includes:

[0015] Mix ethynylisophthalaldehyde, 4,7-dibromobenzo[c][1,2,5]thiadiazole, triethylamine, bis(triphenylphosphine)palladium dichloride, copper iodide, and N,N-dimethylformamide, and then stir and react to obtain it.

[0016] Furthermore, the molar ratio of ethynylisophthalaldehyde, 4,7-dibromobenzo[c][1,2,5]thiadiazole, bis(triphenylphosphine)palladium dichloride, and copper iodide is 16:8:1:4.

[0017] Furthermore, the temperature of the stirring reaction is 60 - 80 o °C, and the time is 48 - 72 h.

[0018] Furthermore, the preparation method of ethynylisophthalaldehyde includes:

[0019] It is obtained by mixing 5-((trimethylsilyl)ethynyl)isophthalaldehyde, potassium carbonate and methanol, and then stirring and reacting them.

[0020] Furthermore, the molar ratio of 5-((trimethylsilyl)ethynyl)isophthalaldehyde to potassium carbonate is 1:1.

[0021] Furthermore, the temperature of the stirring reaction is 20 - 30 o °C, and the time is 12 - 18 h.

[0022] Furthermore, the preparation method of 5-((trimethylsilyl)ethynyl)isophthalaldehyde includes:

[0023] It is obtained by mixing 5-bromoisophthalaldehyde, ethynyltrimethylsilane, diisopropylamine, bis(triphenylphosphine)palladium dichloride, copper(I) iodide and tetrahydrofuran, and then stirring and reacting them.

[0024] Furthermore, the molar ratio of 5-bromoisophthalaldehyde, ethynyltrimethylsilane, bis(triphenylphosphine)palladium dichloride to copper(I) iodide is 100:100:4:3.

[0025] Furthermore, the temperature of the stirring reaction is 20 - 30 o °C, and the time is 12 - 18 h.

[0026] The present invention also provides an acylhydrazone-based covalent organic framework material. The neutral framework material is subjected to protonation or deprotonation reactions under acidic or alkaline conditions to obtain a positively charged framework material or a negatively charged framework material, as Figure 15 shown. The framework material of the present invention has the ability to recover crystallinity, that is, the disappearance of crystallinity caused by interlayer stacking after alkali treatment can be restored by treatment with an acidic solution.

[0027] Preferably, the protonation condition is a liquid with a pH less than 7, such as a hydrochloric acid solution (with a concentration of 12 mol / L or less); the deprotonation condition is a liquid with a pH greater than 7, such as a sodium hydroxide solution (with a concentration of 6 mol / L or less).

[0028] The present invention also provides an application of the neutral framework material in the field of photocatalytic degradation.

[0029] The present invention also provides an application of the positively charged framework material or the negatively charged framework material in the field of water purification and adsorption.

[0030] Beneficial effects

[0031] (1) The present invention synthesizes a neutral acylhydrazone-based covalent organic framework material by Schiff base reaction. The material has excellent chemical stability and can withstand acidic and alkaline solutions while maintaining crystallinity and porosity.

[0032] (2) The present invention uses acid-base solutions to regulate the charged properties of the acylhydrazone-based covalent organic framework skeleton. The operation is simple and reversible switching can be achieved, breaking through the barrier that traditional covalent organic frameworks only have a single charge property, and controllable synthesis can be carried out according to specific usage scenarios.

[0033] (3) The neutral acylhydrazone-based covalent organic framework material synthesized in the present invention is an organic semiconductor, which can generate free radical active species under light irradiation to degrade organic pollutants in aqueous solution, providing another solution in addition to physical adsorption, and degrading pollutants into small molecules harmless to the environment. Description of the Drawings

[0034] Figure 1 1H NMR spectrum of 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde synthesized in Example 1 1 H NMR spectrum.

[0035] Figure 2 Fourier transform infrared spectrum of the neutral acylhydrazone-based covalent organic framework material synthesized in Example 2

[0036] Figure 3 Powder X-ray diffraction spectrum of the neutral acylhydrazone-based covalent organic framework material synthesized in Example 2

[0037] Figure 4 For the neutral acylhydrazone-based covalent organic framework material synthesized in Example 2 13 13C NMR spectrum.

[0038] Figure 5 Zeta potential diagrams of the neutral, positively charged, and negatively charged acylhydrazone-based covalent organic framework materials synthesized in Examples 2 and 3

[0039] Figure 6 Powder X-ray diffraction spectra of the neutral, positively charged, negatively charged, and transformed acylhydrazone-based covalent organic framework materials synthesized in Examples 2, 3, and 4

[0040] Figure 7 Nitrogen adsorption-desorption curves and BET specific surface areas of the neutral, positively charged, negatively charged, and transformed acylhydrazone-based covalent organic framework materials synthesized in Examples 2, 3, and 4

[0041] Figure 8 Solid-state nuclear magnetic carbon spectra of the neutral, positively charged, negatively charged, and transformed acylhydrazone-based covalent organic framework materials synthesized in Examples 2, 3, and 4

[0042] Figure 9Fourier transform infrared absorption spectra of the neutral, positively charged, negatively charged, and transformed acylhydrazone-based covalent organic framework materials synthesized in Examples 2, 3, and 4.

[0043] Figure 10 UV-Vis absorption spectra of the neutral, positively charged, and negatively charged acylhydrazone-based covalent organic framework materials after adsorbing sodium fluorescein dye solution in Example 5.

[0044] Figure 11 UV-Vis absorption spectra of the neutral, positively charged, and negatively charged acylhydrazone-based covalent organic framework materials after adsorbing methylene blue dye solution in Example 5.

[0045] Figure 12 UV-Vis absorption spectra of the positively charged and negatively charged acylhydrazone-based covalent organic framework materials after separating the mixed dye of methylene blue and sodium fluorescein in Example 6.

[0046] Figure 13 UV-Vis absorption spectra of the neutral acylhydrazone-based covalent organic framework material after degrading rhodamine B dye in Example 7.

[0047] Figure 14 Bar chart of the efficiency of the neutral acylhydrazone-based covalent organic framework material for 10 degradation cycles of rhodamine B dye in Example 7.

[0048] Figure 15 Schematic diagram of the transformation of the neutral acylhydrazone-based covalent organic framework material and the ionic acylhydrazone-based covalent organic framework material of the present invention. Detailed implementation manners

[0049] 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.

[0050] Source of raw materials: 5-bromoisophthalaldehyde (Shanghai Haohong Biopharmaceutical Technology Co., Ltd.), ethynyltrimethylsilane (Shanghai Titan Technology Co., Ltd.), 4,7-dibromobenzo[c][1,2,5]thiadiazole (Shanghai Bide Pharmaceutical Technology Co., Ltd.), 2,5-diethoxyterephthalohydrazide (Shanghai Haohong Biopharmaceutical Technology Co., Ltd.).

[0051] Example 1

[0052] 5-Bromo-isophthalaldehyde (2.3 g, 10.82 mmol), ethynyltrimethylsilane (2.8 mL, 19.81 mmol), bis(triphenylphosphine)palladium(II) dichloride (231.6 mg, 0.33 mmol), and copper(I) iodide (79.5 mg, 0.42 mmol) were placed in a Schlenk flask (250 mL). The flask was evacuated and backfilled with nitrogen three times. Under a nitrogen atmosphere, tetrahydrofuran (25 mL) and diisopropylamine (25 mL) were injected into the Schlenk flask, sonicated for 20 min, and stirred at room temperature for 12 h. After the reaction, the mixture was filtered and the filtrate was retained. The resulting product was separated and purified by flash chromatography to obtain 5-((trimethylsilyl)ethynyl)isophthalaldehyde. After standing for 12 h, a white solid was obtained with a yield of 67.9%.

[0053] The obtained 5-((trimethylsilyl)ethynyl)isophthalaldehyde (1.46 g, 6.38 mmol) and potassium carbonate (1.03 g, 7.51 mmol) were placed in a 250 mL Schlenk flask. The flask was evacuated and backfilled with nitrogen three times. Under a nitrogen atmosphere, methanol (45 mL) as the solvent was injected into the Schlenk flask, sonicated for 20 min, and stirred at room temperature for 12 h. After the reaction, the mixture was filtered and the filtrate was retained. The filtrate was extracted by adding dichloromethane to water and taking the organic phase. Then, the organic phase was separated twice with saturated sodium chloride solution. The resulting solution was evaporated in vacuo to obtain ethynylisophthalaldehyde as a white solid powder with a yield of 94.4%.

[0054] The obtained ethynylisophthalaldehyde (62.9 mg, 0.4 mmol), 4,7-dibromobenzo[c][1,2,5]thiadiazole (36.0 mg, 0.12 mmol), bis(triphenylphosphine)palladium(II) dichloride (10.0 mg, 0.014 mmol), and copper(I) iodide (18.6 mg, 0.1 mmol) were placed in a Schlenk flask (50 mL). The flask was evacuated and backfilled with nitrogen three times. Under a nitrogen atmosphere, N,N-dimethylformamide (4 mL) and triethylamine (4 mL) were injected into the Schlenk flask, sonicated for 20 min, and stirred in an oil bath at 70 o °C for 72 h. After the reaction, the mixture was filtered to obtain 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde as a yellow solid powder with a yield of 78.2%.

[0055] The NMR spectrum of 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde obtained in this example is as Figure 1 shown.

[0056] Example 2

[0057] 5,5'-(Benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde (10.0 mg, 0.0334 mmol), 2,5-diethoxyterephthalohydrazide (12.5 mg, 0.0669 mmol), n-butanol (0.8 mL), 1,2-dichlorobenzene (0.2 mL), and acetic acid solution (3 mol / L, 0.1 mL) were added to a Schlenk flask (10 mL), and ultrasonically dispersed for 20 min. The Schlenk flask was evacuated and backfilled with nitrogen three times, sealed under vacuum, and placed in an oven at 120 o °C for 72 h. After the reaction was completed, it was cooled to room temperature, and suction filtration was carried out in a sintered funnel. The obtained product was washed successively with tetrahydrofuran and n-hexane. The washed sample was dried in a vacuum oven for 12 h to obtain a neutral acylhydrazone-based covalent organic framework material with a yield of 91.1%.

[0058] The infrared spectrum of the neutral acylhydrazone-based covalent organic framework material obtained in this example is as Figure 2 shown, and the PXRD pattern is as Figure 3 shown, and the solid-state nuclear magnetic carbon spectrum is as Figure 4 shown.

[0059] Example 3

[0060] The neutral acylhydrazone-based covalent organic framework was placed in hydrochloric acid solution (12 mol / L) and sodium hydroxide solution (6 mol / L) respectively, stirred at room temperature for 1 h, and after the reaction was completed, suction filtration was carried out and washed with a dilute acid-base solution. After drying with a freeze dryer, powders of positively and negatively charged acylhydrazone-based covalent organic frameworks were obtained. The powder treated with acid was bright yellow, and the powder treated with base was brown.

[0061] The Zeta potential of the positively and negatively charged acylhydrazone-based covalent organic framework materials obtained in this example is as Figure 5 shown, the PXRD pattern is as Figure 6 shown, the nitrogen adsorption-desorption curve and BET specific surface area are as Figure 7 shown, the solid-state nuclear magnetic resonance carbon spectrum is as Figure 8 shown, and the infrared absorption spectrum is as Figure 9As shown. In this example, the neutral acylhydrazone-based covalent organic framework has the property of regulating charge by acid and base. From the above results, it can be seen that the synthesized neutral acylhydrazone-based covalent organic framework material can achieve reversible protonation and deprotonation by adjusting the pH value of the solution, obtaining materials with positive and negative charges respectively. The crystallinity and porous properties of the obtained negatively charged material disappear, but it can be known from the test results of solid-state nuclear magnetic resonance carbon spectrum and infrared absorption spectrum that its chemical structure remains good.

[0062] Example 4

[0063] The alkali treatment was carried out, that is, the negatively charged acylhydrazone-based covalent organic framework powder was placed in hydrochloric acid solution (12 mol / L), and bright yellow powder was obtained instantly, that is, the transformed neutral acylhydrazone-based covalent organic framework material.

[0064] The PXRD pattern of the transformed neutral acylhydrazone-based covalent organic framework material obtained in this example is as Figure 6 shown, the nitrogen adsorption-desorption curve is as Figure 7 shown, the solid-state nuclear magnetic resonance carbon spectrum is as Figure 8 shown, and the infrared absorption spectrum is as Figure 9 shown. This example proves that the neutral acylhydrazone-based covalent organic framework material has reversible regulation properties, its two-dimensional layer structure is not destroyed and there is good reversibility, and it has a unique "crystalline-amorphous" reversible switching characteristic.

[0065] Example 5

[0066] 5 mg of neutral, positively charged, and negatively charged acylhydrazone-based covalent organic framework materials were respectively placed in methylene blue (MB) solution (cationic dye, 50 ppm, 10 mL) and sodium fluorescein (FSs) solution (anionic dye, 50 ppm, 10 mL), and stirred for 24 h in a completely dark environment. The obtained solution was filtered to obtain the filtrate. The filtrate was processed to a pH environment that does not affect the dye color development, and diluted 3 times, and ultraviolet-visible absorption spectroscopy was performed to characterize the remaining content.

[0067] The ultraviolet-visible absorption spectrum of the acylhydrazone-based covalent organic framework material after adsorbing sodium fluorescein dye is as Figure 10 shown. The ultraviolet-visible absorption spectrum of the acylhydrazone-based covalent organic framework material after adsorbing methylene blue dye is as Figure 11 shown; it can be seen that the positively charged acylhydrazone-based covalent organic framework material has a better adsorption effect on sodium fluorescein dye, and the negatively charged acylhydrazone-based covalent organic framework material has a better adsorption effect on methylene blue dye.

[0068] Example 6

[0069] Place 10 mg of neutral acylhydrazone-based covalent organic framework powder in a chromatography column and compact it by applying pressure. First, pass the hydrochloric acid solution (12 mol / L) through the powder, then pass 20 mL of the mixed dye solution (methylene blue with a concentration of 50 ppm and sodium fluorescein in a ratio of 1:1) through the powder, and collect the resulting filtrate. Pass the sodium hydroxide solution (6 mol / L) through the powder, then pass 20 mL of the mixed dye solution through the powder, and collect the resulting filtrate.

[0070] The UV-Vis absorption spectra of the positively and negatively charged acylhydrazone-based covalent organic framework materials after separating the mixed dyes are as Figure 12 shown. The positively and negatively charged acylhydrazone-based covalent organic framework materials can achieve selective separation of the mixed dyes by regulating the charge properties of the framework.

[0071] Example 7

[0072] Place 10 mg of neutral acylhydrazone-based covalent organic framework powder in a 20 mL sample bottle, add 5 mL of rhodamine B (50 ppm) dye solution, and stir for about 1 h under light conditions (20W blue LED lamp, 465 nm). Filter the resulting solution to obtain the filtrate. Repeat this operation 10 times.

[0073] The UV-Vis absorption spectral curve of the neutral acylhydrazone-based covalent organic framework material obtained in this example after photocatalytic degradation of the rhodamine B (RB) solution is as Figure 13 shown, and the cyclic test efficiency is as Figure 14 shown. The neutral acylhydrazone-based covalent organic framework material can effectively photocatalytically degrade the rhodamine B dye, with a degradation rate of 99.9% in 1 h, and still maintaining a removal efficiency of over 99% after ten cycles.

Claims

1. A hydrazone-based covalent organic framework material, characterized in that: The acylhydrazone-based covalent organic framework material is an electrically neutral framework material, and its structural general formula is as follows: ; wherein, R 1 , R 2 , R 3 , R 4 are each independently selected from the group consisting of hydrogen, alkyl, and alkoxy.

2. A method for preparing the acylhydrazone-based covalent organic framework material according to claim 1, comprising the following steps: 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde and terephthalohydrazide monomer compound react through a Schiff base reaction to obtain the acylhydrazone-based covalent organic framework material.

3. The preparation method according to claim 2, characterized in that: The structural general formula of the terephthalohydrazide monomer compound is as follows: ; wherein, R 1 , R 2 , R 3 , R 4 are each independently selected from the group consisting of hydrogen, alkyl, and alkoxy.

4. The preparation method according to claim 2, characterized in that: The preparation method of the 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalaldehyde comprises: Mix ethynylisophthalaldehyde, 4,7-dibromobenzo[c][1,2,5]thiadiazole, triethylamine, bis(triphenylphosphine)palladium dichloride, copper iodide and N,N-dimethylformamide, and then stir and react to obtain it.

5. The preparation method according to claim 4, characterized in that: The preparation method of the ethynylisophthalaldehyde comprises: Mix 5-((trimethylsilyl)ethynyl)isophthalaldehyde, potassium carbonate and methanol, and then stir and react to obtain it.

6. The preparation method according to claim 5, characterized in that: The preparation method of the 5-((trimethylsilyl)ethynyl)isophthalaldehyde comprises: Mix 5-bromoisophthalaldehyde, ethynyltrimethylsilane, diisopropylamine, bis(triphenylphosphine)palladium dichloride, copper iodide and tetrahydrofuran, and then stir and react to obtain it.

7. A hydrazone-based covalent organic framework material, characterized in that: Protonate or deprotonate the electrically neutral framework material according to claim 1 under acidic or alkaline conditions to obtain a positively charged framework material or a negatively charged framework material.

8. The acylhydrazone-based covalent organic framework material according to claim 7, wherein: The protonation condition is a liquid with a pH less than 7; the deprotonation condition is a liquid with a pH greater than 7.

9. An application of the electrically neutral framework material according to claim 1 in the field of photocatalytic degradation.

10. An application of the positively charged framework material or negatively charged framework material according to claim 7 in the field of water purification and adsorption.

Images