Hydrogen-bonded organic framework co-crystal, preparation method thereof and application thereof in photocatalytic degradation of pollutants

Abstract

The application discloses a hydrogen-bonded organic framework eutectic material, a preparation method thereof and application thereof in photocatalytic degradation of pollutants, and the hydrogen-bonded organic framework eutectic is a eutectic formed by assembling N,N'-di(5-m-phenylenediformyl) naphthalene diimide hydrogen-bonded organic framework and hexa-peri-hexabenzocoronene. The eutectic material has both porous structure and intermolecular charge transfer interaction. The hydrogen-bonded organic framework eutectic can efficiently photocatalyze removal of phenol which is difficult to degrade and highly toxic, and has great application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic semiconductor materials, in particular to a hydrogen-bonded organic framework eutectic, a preparation method thereof and application thereof in photocatalytic pollutant degradation. BACKGROUND

[0002] Since the discovery of the photocatalytic decomposition of water to produce hydrogen by titanium dioxide in 1972, photocatalytic technology has gradually developed rapidly in the fields of environmental remediation, energy conversion, etc. This method of converting solar energy into chemical energy has attracted the attention of governments and scientists around the world. Photocatalytic technology can not only be used in energy fields such as CO2 reduction, N2 reduction and hydrogen peroxide production, but also can drive redox reactions under room temperature conditions to degrade environmental pollutants and achieve deep mineralization. Therefore, photocatalytic technology is considered an ideal environmental pollution control technology. At present, photocatalytic technology has shown great potential in clean energy production and environmental pollutant degradation, and has great prospects for basic research and industrial application.

[0003] Organic semiconductor materials have natural advantages in controllability of molecular structure, aggregate structure and electronic structure, and availability of resources. In the past decade, research on organic semiconductor photocatalytic materials has been booming, and organic framework materials have received the most attention, such as covalent organic frameworks (COFs), metal-organic frameworks (MOFs) and hydrogen-bonded organic frameworks (HOFs). Unlike MOFs and COFs, which are linked by coordination bonds and covalent bonds to form ordered network structures, HOFs are self-assembled by hydrogen bonding interactions between organic ligands. Therefore, its synthesis conditions are relatively mild, and the structure is flexible and variable. HOFs are also considered as a kind of crystalline porous material that is expected to be popularized and researched after MOFs and COFs. However, some HOFs have small conjugated structures and weak response to visible light, which makes it difficult to be directly used in photocatalytic reactions, further limiting its application in water treatment. Co-crystallization as a functional material design strategy has the advantages of mild material preparation conditions, adjustable molecular structure, solution processing and easy batch production. At the same time, using the flexible framework structure of organic semiconductors and the stable and controllable intermolecular forces to regulate the structure and performance of HOFs is a very effective means. Therefore, it is of great significance to design and develop hydrogen-bonded organic framework eutectic photocatalysts with high catalytic activity and visible light response, and to reveal the structure-activity relationship between material structure characteristics and photocatalytic performance. SUMMARY

[0004] The purpose of the present application is to provide a hydrogen-bonded organic framework eutectic in view of the fact that HOFs have weak response to visible light in the prior art, which makes it difficult to be directly used in photocatalytic reactions and water treatment.

[0005] Another object of the present application is to provide a method for preparing the hydrogen-bonded organic framework co-crystal.

[0006] Another object of the present application is to provide an application of the hydrogen-bonded organic framework co-crystal in photocatalytic pollutant degradation.

[0007] The technical solution adopted to achieve the object of the present application is as follows:

[0008] A hydrogen-bonded organic framework co-crystal is assembled by N,N'-di(5-terephthalic acid) naphthalene diimide hydrogen-bonded organic framework and hexa-peri-hexabenzocoronene, wherein the structural formula of the N,N'-di(5-terephthalic acid) naphthalene diimide is as follows:

[0009]

[0010] The structural formula of the hexa-peri-hexabenzocoronene is as follows:

[0011]

[0012] In the above technical solution, the hydrogen-bonded organic framework co-crystal belongs to triclinic system, P-1 point group, and the unit cell parameters are as follows: α = 83.840°, β = 79.489°, γ = 86.234°.

[0013] In the above technical solution, the hydrogen-bonded organic framework co-crystal is prepared by the following method: dissolving N,N'-di(5-terephthalic acid) naphthalene diimide and hexa-peri-hexabenzocoronene in a solvent, and obtaining the molecular co-crystal material after a solvothermal reaction.

[0014] In the above technical solution, the ratio of the amount of substance of the N,N'-di(5-terephthalic acid) naphthalene diimide to the hexa-peri-hexabenzocoronene is 1:(2-3).

[0015] In the above technical solution, the solvent is a solvent formed by mixing N,N'-dimethylformamide and 1 mol / L hydrochloric acid at a volume ratio of (3-5):1.

[0016] In the above technical solution, the temperature of the solvothermal reaction is 90-120℃, and the time is 60-72 hours.

[0017] Another aspect of the present application also includes an application of the hydrogen-bonded organic framework co-crystal as a catalyst in photocatalytic pollutant degradation.

[0018] In the above technical solution, the catalyst is dispersed in sewage containing pollutants, and degradation is carried out under light with a wavelength range of 400-780 nm.

[0019] In the technical scheme, 0.1-2 mg of the catalyst is added to each mL of the sewage containing the pollutants.

[0020] In the technical scheme, the pollutants are phenol, rhodamine B, methylene blue, tetracycline hydrochloride, oxytetracycline, ciprofloxacin, chlorophenol or bisphenol A.

[0021] Compared with the prior art, the hydrogen-bonded organic framework eutectic material has the advantages that:

[0022] 1. The hydrogen-bonded organic framework eutectic material has a novel molecular packing structure, and has a porous structure and intermolecular donor-acceptor interaction. The hydrogen-bonded organic framework eutectic material has great research value in terms of crystal structure and material innovation.

[0023] 2. The hydrogen-bonded organic framework eutectic material has high catalytic performance, good universality and strong recycling performance when applied to photocatalytic degradation of pollutants.

[0024] 3. The hydrogen-bonded organic framework eutectic material has a high-efficiency free radical and non-free radical conversion path by synergizing the porous structure and charge transfer interaction in the degradation and mineralization mechanism of the pollutants. The hydrogen-bonded organic framework eutectic material has scientific value in basic research of water treatment processes. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The optical microscope photo of the hydrogen-bonded organic framework eutectic material obtained in Example 1;

[0026] Figure 2 The crystal structure diagram of the hydrogen-bonded organic framework eutectic material obtained in Example 1;

[0027] Figure 3 The fluorescence spectrum diagram of the hydrogen-bonded organic framework eutectic material obtained in Example 1;

[0028] Figure 4 The ultraviolet-visible absorption spectrum diagram of the hydrogen-bonded organic framework eutectic material obtained in Example 1;

[0029] Figure 5 The electron spin resonance signal of the hydrogen-bonded organic framework eutectic material obtained in Example 1;

[0030] Figure 6 The curve diagram of photocatalytic degradation of phenol by the hydrogen-bonded organic framework eutectic material obtained in Example 2;

[0031] Figure 7 The rate comparison diagram of photocatalytic degradation of phenol by the hydrogen-bonded organic framework eutectic material obtained in Example 2;

[0032] Figure 8 The mineralization degree change diagram of photocatalytic degradation of phenol by the hydrogen-bonded organic framework eutectic material obtained in Example 2;

[0033] Figure 9 Figure. Recycling performance of the hydrogen-bonded organic framework eutectic for photocatalytic degradation of phenol obtained from Example 2. DETAILED DESCRIPTION

[0034] The application will be further described in conjunction with specific examples. It should be understood that the specific examples described herein are intended to explain the application and not to limit the application.

[0035] Example 1

[0036] A method for preparing a hydrogen-bonded organic framework eutectic, 0.1 mmol of N,N'-di(5-m-phenylenedioxy) naphthalimide and 0.2 mmol of hexa- phenylbenzene were placed in a 15 mL pressure-resistant glass bottle, 4 mL of N,N'- dimethylformamide and 1 mL of 1 mol / L hydrochloric acid were added, and ultrasonic was applied for 60 minutes until complete dissolution. The above solution was placed in an oven at 100°C for 72 hours to obtain red parallelogram crystals, which were the hydrogen-bonded organic framework eutectic.

[0037] Figure 1 The optical microscope photograph of the obtained hydrogen-bonded organic framework eutectic is shown. The measurement was performed by a Leica DM2700 M upright metallographic microscope. As can be seen from the figure, the hydrogen-bonded organic framework eutectic formed by co-assembly of N,N'-di(5-m-phenylenedioxy) naphthalimide and hexaphenylbenzene is red, and the morphology is uniform, and the crystal size is large, reaching millimeter level.

[0038] Figure 2 The crystal structure of the obtained hydrogen-bonded organic framework eutectic is shown. The crystal structure analysis was performed by a Bruker SMART APEX-II instrument (X-ray emission target Cu-Ka, λ = 0.154 nm, 293 K) for data collection, and the single crystal structure analysis was performed by Olex 2 software. The hydrogen-bonded organic framework eutectic belongs to triclinic system, P-1 point group, and the cell parameters are a = 1. 1 1 nm, b = 1. 1 1 nm, c = 1. 1 1 nm, α = 83.840°, β = 79.489°, γ = 86.234°.

[0039] Figure 3 The fluorescence spectrum of the obtained hydrogen-bonded organic framework eutectic is shown. The measurement was performed by an Edinburgh FLS1000 fluorescence spectrometer. The fluorescence emission peak of N,N'-di(5-m-phenylenedioxy) naphthalimide is located at 450 nm, and the fluorescence emission peak of hexaphenylbenzene is located at 540 nm. The hydrogen-bonded organic framework eutectic formed by co-assembly of hexaphenylbenzene and N,N'-di(5-m-phenylenedioxy) naphthalimide shows red shift compared with the two single components, and the emission peak is located at 680 nm, corresponding to red fluorescence. The fluorescence emission spectrum preliminarily indicates that the hydrogen-bonded organic framework eutectic has charge transfer interaction.

[0040] ​Figure 4 UV-Vis absorption spectra of the obtained hydrogen-bonded organic framework co-crystal are shown. The measurements were performed by a Shimadzu UV-3600 Plus spectrophotometer. The absorption cut-off edge of N,N'-bis(5-carboxybenzoyl) naphthalimide is at 420 nm, and that of hexa-phenylbenzene is at 500 nm. The hydrogen-bonded organic framework co-crystal formed by the co-assembly of hexa-phenylbenzene and N,N'-bis(5-carboxybenzoyl) naphthalimide shows a red-shifted absorption compared to the two single components, and the absorption cut-off edge is at 600 nm. The UV-Vis absorption spectra further indicate the charge transfer interaction in the hydrogen-bonded organic framework co-crystal.

[0041] Figure 5 ESR signals of the obtained hydrogen-bonded organic framework co-crystal are shown. The measurements were performed by a Bruker EMXplus ESR spectrometer, and the same amount of solid powder was used for the test, so that the signal intensity can be directly compared. N,N'-bis(5-carboxybenzoyl) naphthalimide shows a weak spin signal peak at g = 2.003, and the signal intensity of the hydrogen-bonded organic framework co-crystal is greatly improved at the same position. This indicates that the degree of electron delocalization caused by the charge transfer interaction in the hydrogen-bonded organic framework co-crystal is increased.

[0042] Example 2

[0043] This example is the application of the hydrogen-bonded organic framework co-crystal prepared in Example 1 in photocatalytic degradation of phenol.

[0044] First, 20 mg of the hydrogen-bonded organic framework co-crystal was ultrasonically dispersed in 40 mL of deionized water. Then, 10 mL of a phenol aqueous solution with a concentration of 100 mg / L was added to obtain a 50 mL mixed solution; in the mixed solution, the concentration of phenol was 20 mg / L.

[0045] The beaker was wrapped with tin foil to achieve light shielding effect, and stirred for 60 minutes to ensure that the adsorption-desorption equilibrium was reached. After the adsorption equilibrium was reached, about 2 mL of the sample was taken, filtered through a filter head to remove the solid material therein, and the initial concentration Co was measured on a UV-Vis spectrophotometer.

[0046] A 300 W xenon lamp was used as the excitation light source to perform the simulated visible light catalysis experiment. The wavelength range of the xenon lamp used was 400-780 nm.

[0047] At the 30th, 60th, 90th, 120th, 150th, and 180th minutes of illumination, about 2 mL of the sample was taken, centrifuged, and the supernatant was saved. The concentration was measured on a UV-Vis spectrophotometer. The degradation degree was represented by C t / C0, where Co was the pollutant concentration after dark adsorption equilibrium, and C t was the concentration after sampling at a certain interval.

[0048] Figure 6 The degradation curve of the obtained phenol. After 150 minutes of light irradiation, the hydrogen-bonded organic framework eutectic can degrade more than 90% of the phenol. Under the same experimental conditions, the N,N'-di(5-terephthalyl)naphthalene diimide monomer can only degrade 15% of the phenol, and the hexa-peri-hexabenzocoronene monomer can only degrade 7% of the phenol.

[0049] Figure 7 The rate constant comparison chart of the obtained phenol degradation. The pseudo-first-order kinetic constant of the hydrogen-bonded organic framework eutectic degrading phenol is 0.015 min -1 The pseudo-first-order kinetic constant of the N,N'-di(5-terephthalyl)naphthalene diimide monomer degrading phenol is 0.0010 min -1 The pseudo-first-order kinetic constant of the hexa-peri-hexabenzocoronene monomer degrading phenol is 3.4 x 10 - 4 min -1 The rate of the hydrogen-bonded organic framework eutectic photocatalytic degradation of phenol is 44.12 times and 15.00 times that of hexa-peri-hexabenzocoronene and N,N'-di(5-terephthalyl)naphthalene diimide, respectively.

[0050] Figure 8 The degree of mineralization of the obtained phenol changes chart. After 180 minutes of light irradiation, the hydrogen-bonded organic framework eutectic can mineralize 86.06% of the phenol. Under the same experimental conditions, the N,N'-di(5-terephthalyl)naphthalene diimide monomer can only mineralize 10.06% of the phenol.

[0051] Figure 9 The obtained hydrogen-bonded organic framework eutectic recycling performance chart. After 5 consecutive cycles of 15 hours, the hydrogen-bonded organic framework eutectic can still maintain good photocatalytic degradation ability. Although the degradation ability decreases slightly, the hydrogen-bonded organic framework eutectic can still degrade 76% of the phenol after the 5th cycle.

[0052] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A hydrogen-bonded organic framework eutectic, characterized in that, It is formed by assembling an N,N'-bis(5-isophthaloyl)naphthalimide hydrogen-bonded organic framework and a hexabenzobenzene, wherein the structural formula of the N,N'-bis(5-isophthaloyl)naphthalimide is: The structural formula of the hexabenzobenzene is:

2. The hydrogen-bonded organic framework eutectic as described in claim 1, characterized in that, Hydrogen-bonded organic framework eutectics belong to the triclinic crystal system, point group P-1, and have the following unit cell parameters: α=83.840°, β=79.489°, γ=86.234°.

3. The hydrogen-bonded organic framework eutectic as described in claim 1, characterized in that, The hydrogen-bonded organic framework eutectic was prepared by the following method: N,N'-bis(5-isophthaloyl)naphthalimide and hexabenzobenzene were dissolved in a solvent, and the hydrogen-bonded organic framework eutectic was obtained by solvothermal reaction.

4. The hydrogen-bonded organic framework eutectic as described in claim 3, characterized in that, The molar ratio of N,N'-bis(5-isophthaloyl)naphthalimide to hexabenzobenzene is 1:(2-3).

5. The hydrogen-bonded organic framework eutectic as described in claim 3, characterized in that, The solvent is a mixture of N,N'-dimethylformamide and 1 mol / L hydrochloric acid in a volume ratio of (3-5):

1.

6. The hydrogen-bonded organic framework eutectic as described in claim 3, characterized in that, The temperature of the solvothermal reaction is 90-120℃, and the time is 60-72 hours.

7. The application of the hydrogen-bonded organic framework eutectic as described in claim 1 as a catalyst in the photocatalytic degradation of pollutants.

8. The application as described in claim 7, characterized in that, The catalyst was dispersed in wastewater containing pollutants and degraded under light irradiation in the wavelength range of 400-780 nm.

9. The application as described in claim 7, characterized in that, Add 0.1–2 mg of catalyst per mL of wastewater containing pollutants.

10. The application as described in claim 7, characterized in that, The contaminants are phenol, rhodamine B, methylene blue, tetracycline hydrochloride, oxytetracycline, ciprofloxacin, chlorophenol, or bisphenol A.

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