Preparation method of pyrenyl covalent organic framework material and application of pyrenyl covalent organic framework material in photocatalytic hydrogen production

Abstract

The invention discloses a preparation method of a pyrenyl covalent organic framework material and application of the pyrenyl covalent organic framework material in photocatalytic hydrogen production reaction, and belongs to the field of heterogeneous catalysis. The novel pyrenyl COFs photocatalyst is synthesized by regulating and controlling the quantity of triphenylamine and integrating triphenylamine monomers with different contents into a pyrenyl covalent organic framework (COF) skeleton. The preparation method is simple to operate, mild in reaction condition, short in reaction time and high in repeatability, the obtained pyrenyl COFs have good light capture capacity and photon-generated carrier separation characteristic, electron-hole recombination can be effectively reduced, the excited state service life is prolonged, the reaction efficiency of photocatalytic hydrogen production is improved, and potential application prospects are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heterogeneous catalysis, and particularly relates to a preparation method of a pyrene-based covalent organic framework material and application thereof in photocatalytic hydrogen production. BACKGROUND

[0002] Converting solar energy into clean hydrogen energy through photocatalytic technology is a promising strategic path to solve the energy crisis and achieve carbon neutralization. The core of this technology lies in developing efficient and stable photocatalysts. However, most photocatalytic systems currently still fall short of ideal performance in hydrogen production, mainly due to low efficiency of photo-induced charge separation and transfer, short excited state lifetime, and other key scientific issues.

[0003] Therefore, designing and constructing new photocatalytic materials with high efficiency of charge separation and transfer, and long excited state lifetime, is of great significance to promote the practical application of photocatalytic hydrogen production technology. COFs materials have the property of structural designability, providing an ideal platform for structural regulation of photocatalysts. By rationally designing the structure of precursors, functional units can be introduced into the COF framework in an orderly manner, thereby precisely regulating the photoelectric properties and catalytic activity of the material. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a preparation method and application of a pyrene-based covalent organic framework material. By integrating different contents of triphenylamine (TPA) units into the COF framework, a new type of pyrene-based COFs photocatalytic material is synthesized. This type of material not only has good light capturing ability and suitable band gap, but also effectively promotes charge separation and transfer, significantly improves the excited state electron lifetime, thereby improving the photocatalytic hydrogen production reaction rate, and has potential application prospects.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme: A pyrene-based covalent organic framework material is prepared by uniformly mixing 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl) tetraphenylamine, aldehyde monomer, organic solvent, and acetic acid solution, then degassing by three cycles of freezing-extraction-melting in a 77 K liquid nitrogen bath, and then vacuumizing, sealing, and performing Schiff base reaction at high temperature. After the reaction is completed, the obtained solid is separated by solid-liquid separation, filtered and washed, then subjected to Soxhlet extraction with tetrahydrofuran, and finally dried to obtain the pyrene-based covalent organic framework material, the structure of which is shown as follows: .

[0006] Further, the molar ratio of 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl) tetraphenylamine to aldehyde monomer is 1:1.

[0007] Further, the aldehyde monomer is any one of 5',5'''-bis(4-formylphenyl)-[1,1':3',1'':4'',1''':3''',1''''-quaterphenyl]-4,4''''-diformaldehyde, 5'-(4-(bis(4-formylphenyl)amino)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diformaldehyde, and 4,4',4'',4'''-(1,4-phenylenebis(azatriyl))tetrakisbenzaldehyde.

[0008] Further, the organic solvent is a mixed solution of o-dichlorobenzene and n-butanol, and the volume ratio of o-dichlorobenzene to n-butanol is 1:1.

[0009] Further, the volume ratio of the organic solvent to the acetic acid solution is 10:1.

[0010] Further, the concentration of the acetic acid solution is 6 mol / L.

[0011] Further, the temperature of the Schiff base reaction is 120 ºC, and the time is 72 h.

[0012] The pyrene-based covalent organic framework material can be used for photocatalytic hydrogen production. Specifically, the triphenylamine-based covalent organic framework material is used as a photocatalyst for photocatalytic decomposition of water to produce hydrogen in an ascorbic acid-water-chloroplatinic acid system, and the reaction temperature is 12 ºC, the reaction time is 1 h, the concentration of the ascorbic acid aqueous solution in the system is 0.01 mol / L, and the content of chloroplatinic acid is 14 μL (2 wt%).

[0013] Compared with the prior art, the present application has the following advantages: (1) The present application discloses a pyrene-based covalent organic framework material and a preparation method thereof, and the material is applied to photocatalytic hydrogen production. The π-π conjugation effect between the lone pair electrons on the nitrogen atom in TPA and the benzene ring significantly enhances the electronic density and electronegativity of the system, which helps to improve the electron donor ability. By adjusting the amount of TPA, different amounts of TPA units are integrated into the COFs framework to synthesize a new type of pyrene-based COFs photocatalytic material. This type of material not only has good light capturing ability and suitable band gap, but also can promote charge separation and transfer, significantly improve the excited state electron lifetime, and effectively improve the photocatalytic hydrogen production reaction rate.

[0014] (2) The photocatalyst disclosed by the present application has the advantages of simple manufacturing process, low cost, and strong stability; the photocatalytic reaction conditions are mild and environmentally friendly, which is conducive to large-scale industrial production and application. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The synthesis flowchart of the pyrene-based material prepared in Examples 1-3 is shown in the figure. Figure 2 Powder X-ray diffraction pattern of pyrene-based material prepared for Examples 1-3; Figure 3 Fourier-transform infrared spectroscopy pattern of pyrene-based material prepared for Examples 1-3; Figure 4 Solid-state nuclear magnetic resonance spectroscopy pattern of pyrene-based material prepared for Examples 1-3; Figure 5 X-ray photoelectron spectroscopy pattern of pyrene-based material prepared for Examples 1-3; Figure 6 Reaction activity pattern (a) of pyrene-based material prepared for Examples 1-3 for photocatalytic hydrogen evolution from water and photocatalytic effect pattern (b) after 20 h of 2N-COF cycling. DETAILED DESCRIPTION

[0016] In order to make the content of the present application more convenient to understand, the technical solutions described in the present application will be further described below in combination with specific embodiments, but the present application is not limited thereto.

[0017] Preparation of pyrene-based COF material 0N-COF without triphenylamine motif for Example 1: In a single-necked flask, 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl) tetrakisphenylamine (0.06 mmol, 34 mg), 5',5'''-bis(4-formylphenyl)-[1,1':3',1'':4'',1''':3''',1''''-quaterphenyl]-4,4''''-dicarbaldehyde (0.06 mmol, 38.8 mg), o-dichlorobenzene (1 mL), n-butanol (1 mL) were added and homogenized by ultrasound, then acetic acid aqueous solution (6.0 mol / L, 200 μL) was added, and the mixture was rapidly frozen in a liquid nitrogen bath at 77 K. After three rounds of freeze-pump-thaw degassing, the flask was sealed under vacuum and then heated at 120 °C for 72 h. After cooling to room temperature, the solid was collected by filtration and washed with acetone and methanol until the effluent was colorless, then Soxhlet extraction with tetrahydrofuran at 100 °C for 24 h. The product was dried under vacuum at 60 °C for 12 h to obtain the yellow pyrene-based COF material 0N-COF without triphenylamine motif.

[0018] Preparation of pyrene-based COF material 1N-COF with one triphenylamine motif for Example 2: In a single neck flask was added 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetraphenylamine (0.06 mmol, 34 mg), 5'-(4-(bis(4-formylphenyl)amino)phenyl)-[1,1':3',1"-terphenyl]-4,4"-dicarbaldehyde (0.06 mmol, 36 mg), o-dichlorobenzene (1 mL), n-butanol (1 mL), homogenized by sonication, then acetic acid aqueous solution (6.0 mol / L, 200 μL) was added, rapidly frozen in a 77 K liquid nitrogen bath, degassed by three freeze-pump-thaw cycles, then sealed under vacuum, and heated at 120 °C for 72 h. After cooling to room temperature, the solid was collected by filtration, washed with acetone and methanol until the effluent was colorless, then Soxhlet extracted with tetrahydrofuran at 100 °C for 24 h. The product was dried under vacuum at 60 °C for 12 h to give the yellow pyrene-based COF material 1N-COF containing one triphenylamine unit.

[0019] Example 3. Preparation of pyrene-based COF material 2N-COF containing two triphenylamine units: In a single neck flask was added 4,4',4",4"'-(pyrene-1,3,6,8-tetrayl)tetraphenylamine (0.06 mmol, 34 mg), 4,4',4",4"'-(1,4-phenylenebis(nitrogen triyl))tetrakisbenzaldehyde (0.06 mmol, 30 mg), o-dichlorobenzene (1 mL), n-butanol (1 mL), homogenized by sonication, then acetic acid aqueous solution (6.0 mol / L, 200 μL) was added, rapidly frozen in a 77 K liquid nitrogen bath, degassed by three freeze-pump-thaw cycles, then sealed under vacuum, and heated at 120 °C for 72 h. After cooling to room temperature, the solid was collected by filtration, washed with acetone and methanol until the effluent was colorless, then Soxhlet extracted with tetrahydrofuran at 100 °C for 24 h. The product was dried under vacuum at 60 °C for 12 h to give the orange-yellow pyrene-based COF material 2N-COF containing two triphenylamine units.

[0020] Figure 2 The powder X-ray diffraction patterns of the prepared novel pyrene-based COFs materials. As can be seen from the figure, the pyrene-based COFs materials all have good crystallinity.

[0021] Figure 3 The Fourier transform infrared spectra of the prepared novel pyrene-based COFs materials. As can be seen from the figure, the stretching vibration peak at 1626 cm -1 belongs to the C=N bond, proving the successful condensation of amine monomers and aldehyde monomers.

[0022] Figure 4 The solid-state nuclear magnetic resonance spectra of the prepared novel pyrene-based COFs materials. The figure proves the existence of imine and triphenylamine skeleton carbon atoms.

[0023] Figure 5 X-ray photoelectron spectroscopy of the prepared novel pyrene-based COFs material. In the figure, the high-resolution C 1s XPS spectrum (a) can be decomposed into four main peaks located at ~284.8 eV, ~286.0 eV, ~286.5 eV and ~289.0 eV, which belong to C=C / C-C bond, C-N-C bond, C=N bond and unreacted C=O in the pyrene-based COFs material, respectively; in the N 1s spectrum (b), two main peaks are divided, which belong to N atoms on C=N (~398.7 eV) and C-N (~400.0 eV) in the pyrene-based COFs material.

[0024] Application Example 1: photocatalytic decomposition of water to produce hydrogen: 10 mg of pyrene-based COFs material was weighed into 100 mL of ascorbic acid (0.01 mol / L) aqueous solution, ultrasonically mixed uniformly and then poured into a reactor, and 14 μL of chloroplatinic acid (2 wt%) was added. After the air in the system was completely removed by a vacuum system, the reaction temperature was maintained at 12 °C, and a xenon lamp (300 W) was turned on for reaction. After the reaction was completed, the amount of hydrogen generated was analyzed by gas chromatography (Shimadzu GC-8A) injection.

[0025] Figure 6 The reaction activity diagram of the prepared novel pyrene-based COFs photocatalytic material for photocatalytic decomposition of water to produce hydrogen and the photocatalytic effect diagram after 2N-COF was recycled for 20 h. As can be seen from the figure, 2N-COF shows high catalytic activity, and still maintains high catalytic activity after 20 h of recycling.

[0026] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A method for preparing a pyrene-based covalent organic framework material, characterized in that: 4,4',4'',4'''-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine, aldehyde monomer, organic solvent, and acetic acid solution were mixed thoroughly and subjected to a Schiff base reaction under vacuum and high temperature conditions. After filtration, washing, and Soxhlet extraction, a pyrene-based covalent organic framework material was obtained. The structure of the pyrene-based covalent organic framework material is shown below: 。 2. The preparation method according to claim 1, characterized in that: The aldehyde monomer is any one of 5',5'''-bis(4-formylphenyl)-[1,1':3',1'':4'',1''':3''',1'''-pentaphenyl]-4,4''''-dicarboxaldehyde, 5'-(4-(bis(4-formylphenyl)amino)phenyl)-[1,1':3',1''-terphenyl]-4,4''-dicarboxaldehyde, and 4,4',4'',4'''-(1,4-phenylenebis(azatriyl))tetrabenzaldehyde.

3. The preparation method according to claim 1, characterized in that: The molar ratio of 4,4',4'',4'''-(pyrene-1,3,6,8-tetramethyl)tetraphenylamine to the aldehyde monomer is 1:

1.

4. The preparation method according to claim 1, characterized in that: The organic solvent is a mixed solution of o-dichlorobenzene and n-butanol, wherein the volume ratio of o-dichlorobenzene to n-butanol is 1:

1.

5. The preparation method according to claim 1, characterized in that: The volume ratio of the organic solvent to the acetic acid solution is 10:

1.

6. The preparation method according to claim 1, characterized in that: The concentration of the acetic acid solution is 6 mol / L.

7. The preparation method according to claim 1, characterized in that: The Schiff base reaction was carried out at a temperature of 120 ºC for 72 h.

8. A pyrene-based covalent organic framework material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the pyrene-based covalent organic framework material as described in claim 8 in photocatalytic hydrogen production, characterized in that: Using the aforementioned pyrene-based covalent organic framework material as a photocatalyst, a photocatalytic water splitting reaction to produce hydrogen was carried out in an ascorbic acid aqueous solution-chloroplatinic acid system.

10. The application according to claim 9, characterized in that: The reaction temperature was 12 ºC and the reaction time was 1 h; the concentration of the ascorbic acid aqueous solution was 0.01 mol / L.

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