Preparation of PDI / Pt at TpBpy-COF composite material and photocatalytic water decomposition

Abstract

The invention relates to preparation of a PDI / Pt at TpBpy-COF composite material and photocatalytic water decomposition. The invention provides a novel PDI / Pt-coated TpBpy-COF composite material, and aims to solve the problems that the light utilization rate is low and electron holes are easy to compound when existing TpBpy-COF is used for photocatalytic decomposition of water. The method comprises the following steps: 1, preparing Pt NPs; 2, PDI treatment is carried out; and 3, preparing the PDI / Pt-coated TpBpy-COF composite material. The preparation process is simple and effective, the reagent consumption is low, and the performance is high; the photocatalyst provided by the invention can effectively solve the problem of low photocatalytic water decomposition efficiency. The composite material is applied to the field of photocatalytic water decomposition, experiments show that the composite material has excellent photocatalytic water decomposition performance, the water decomposition hydrogen production rate under visible light irradiation can reach 298.4 [mu] mol.h <-1 >. G <-1 >, and the oxygen production efficiency is 149.2 [mu] mol.h <-1 >. G <-1 >.

Description

Technical Field

[0001] The invention relates to the preparation of a PDI / Pt@TpBpy-COF composite material and photocatalytic water decomposition. Background Art

[0002] With the intensification of the global energy crisis and the increase in attention to environmental issues, it is crucial to find clean and renewable energy. Hydrogen energy has become an ideal energy carrier due to its high energy density and pollution-free combustion products. As the most abundant resource on earth, water is a very promising way to obtain hydrogen energy by photocatalytic decomposition of water to produce hydrogen and oxygen. Therefore, the preparation of photocatalysts for photocatalytic water splitting is an effective way to solve the energy crisis. It uses solar energy as energy, decomposes water into hydrogen and oxygen through photocatalytic reactions, and releases electrical energy at the same time. Therefore, the preparation of photocatalysts for photocatalytic water splitting technology will become one of the important means to solve the energy crisis. Traditional composite photocatalysts often ignore the internal electric field (i.e., interface electric field) of the heterostructure interface, which leads to a decrease in the separation efficiency of carriers. In addition, due to interface mismatch, the internal electron and hole transmission is hindered, resulting in unsatisfactory catalytic effect. Therefore, a heterojunction with an internal electric field and interface matching is constructed to effectively utilize visible light and improve the electron-hole separation efficiency to improve catalytic activity. It can be seen that designing and constructing efficient composite photocatalysts with band matching, interface matching, and built-in electric field to achieve efficient transmission of photogenerated electrons and holes is both challenging and of great significance in the research field of photocatalytic water splitting.

[0003] Covalent Organic Frameworks (COFs) are a class of crystalline porous polymers formed by organic units connected by covalent bonds. Due to their excellent light absorption properties, adjustable structure and large specific surface area, they are gradually regarded as important photocatalysts for water splitting. Covalent organic framework materials (COFs) are porous crystalline materials formed by light elements such as C, B, O, and N linked by covalent bonds. They have the advantages of light weight, low density, high specific surface area, regular structure, uniform pores, relatively stable structure, easy functional modification and a variety of building blocks. COFs show great potential for application in many fields such as gas storage and separation, catalysis, sensing, energy storage, and photoelectric conversion. Due to the strong controllability of the structure and performance of COFs, COFs are expected to become an important functional material in the future with the continuous improvement of synthesis technology and the continuous expansion of application fields. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that electron holes in a single-component photocatalyst are easy to recombine and the water decomposition efficiency is low, and to provide a preparation method of a PDI / Pt@TpBpy-COF composite material and its application in photocatalytic water decomposition.

[0005] The preparation method of a PDI / Pt@TpBpy-COF composite material of the present invention is completed by the following steps: 1. Preparation of PDI / Pt@TpBpy-COF composites: N,N-dimethylacetamide (DMA) solution containing Pt NPs, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and PDI were added to a heat-resistant glass tube, and o-dichlorobenzene and DMA were added in sequence. The mixture was ultrasonically treated at an ultrasonic frequency of 35 to 45 kHz for 30 to 35 min, and then 6 mol·L -1 The glacial acetic acid solution was cyclically frozen and degassed in liquid nitrogen three times, sealed, heated at 120°C for 72h, filtered and washed with DMA and ethanol several times, then extracted with a Soxhlet extractor until clean, and vacuum dried at 60°C to obtain a reddish-brown powder, which is the PDI / Pt@TpBpy-COF composite material. The concentration of the DMA solution containing Pt NPs used in step 1 was 2.96 mg / ml; The mass ratio of Pt NPs to TpBpy-COF in step 1 is 0.03:1; The mass ratio of PDI to TpBpy-COF in step 1 is 2:8; The molar ratio of 5,5-diamino-2,2-bipyridine to 1,3,5-trialdehyde phloroglucinol in step 1 is 3:2; The volume ratio of o-dichlorobenzene, DMA and acetic acid in step 1 is 0.5:1.5:0.2; After sealing as described in step 1, heat at 120°C for 72h. Application of the above-mentioned PDI / Pt@TpBpy-COF composite material in photocatalytic water decomposition.

[0006] Beneficial effects of the present invention: The present invention adopts a solvothermal method, uses 5,5-diamino-2,2-bipyridine and 1,3,5-trialdehyde phloroglucinol as raw materials, and adds Pt NPs in situ to successfully synthesize Pt@TpBpy-COF. However, the efficiency of water decomposition of this material under visible light is relatively low, which is 69.4 μmol·h -1 ·g -1 Therefore, the inventor combined Pt@TpBpy-COF with PDI to synthesize PDI / Pt@TpBpy-COF composite material, which effectively improved the photocatalytic water decomposition performance and the hydrogen production efficiency was 298.4μmol·h -1 ·g -1 , oxygen production efficiency is 149.2 μmol·h -1 ·g -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 X-ray powder diffraction pattern of PDI / Pt@TpBpy-COF material; Figure 2 This is the infrared spectrum of PDI / Pt@TpBpy-COF material; Figure 3 This is the photocatalytic water decomposition performance diagram of PDI / Pt@TpBpy-COF material. DETAILED DESCRIPTION

[0008] The present invention is further described below with reference to examples. These examples are only used to illustrate the method of the present invention and have no limitation on the scope of application of the present invention.

[0009] Example 1: The preparation of a PDI / Pt@TpBpy-COF material of this embodiment is completed by the following steps: 1. Preparation of Pt nanoparticles: Add chloroplatinic acid solution, polyvinyl pyrrolidone (PVP), ethylene glycol solution containing sodium hydroxide and ethylene glycol into a three-necked flask, stir and heat under vacuum, and keep at 180°C for 3 minutes. Cool to room temperature, centrifuge the resulting solution with acetone, wash it several times with n-hexane, let it stand for one minute until the n-hexane evaporates, and add 2 ml of DMA to disperse the Pt nanoparticles. The concentration of the chloroplatinic acid solution in step 1 is 7.4 mg / ml; The concentration of the ethylene glycol solution containing sodium hydroxide in step 1 is 0.2 mol·L -1 ; The volume ratio of the chloroplatinic acid solution, the ethylene glycol solution containing sodium hydroxide and ethylene glycol in step 1 is 0.5:1:5; The concentration of the DMA solution containing Pt NPs in step 1 is 2.96 mg / ml. 2. Treatment of PDI: Concentrated sulfuric acid and water were used to form a H2SO4 / H2O mixed solvent system. 0.1g of commercial PDINH (perylene-3,4,9,10-tetracarboxylic acid diimide) was dissolved in 10mL H2SO4 (good solvent) under ultrasonic treatment conditions, and then 100mL of deionized water (poor solvent) was added to the above solution at one time. Solid insoluble precipitates will appear immediately and these suspensions will be allowed to stand for another 0.5 hours, and the resulting dark red solids will be collected by filtration through a 0.45μm membrane filter, washed several times with deionized water, and then dried in a 60°C oven for subsequent use. The result is the self-assembled PDI supramolecule. 3. Preparation of PDI / Pt@TpBpy-COF composites: N,N-dimethylacetamide (DMA) solution containing Pt NPs, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and PDI were added to a heat-resistant glass tube, and o-dichlorobenzene and DMA were added in sequence. The tube was ultrasonically treated at an ultrasonic frequency of 35 to 45 kHz for 30 to 35 min, and then 6 mol·L -1 The acetic acid solution was refrigerated and degassed in liquid nitrogen three times, sealed, heated at 120°C for 72h, filtered, washed with DMA and ethanol several times, and dried in vacuum at 60°C to obtain a reddish-brown powder, which is the PDI / Pt@TpBpy-COF composite material; The concentration of the DMA solution containing Pt NPs used in step 3 was 2.96 mg / ml; The mass ratio of Pt NPs to TpBpy-COF in step 3 is 0.03:1; The mass ratio of PDI to TpBpy-COF in step 3 is 2:8; The molar ratio of 5,5-diamino-2,2-bipyridine to 1,3,5-trialdehyde phloroglucinol in step 3 is 3:2; The volume ratio of o-dichlorobenzene, DMA and acetic acid in step 3 is 0.5:1.5:0.2; After sealing as described in step 3, heat at 120°C for 72h.

[0010] To verify the beneficial effects of the present invention, the following test was conducted: To investigate the photocatalytic water decomposition effect of PDI / Pt@TpBpy-COF material, its visible light photocatalytic water decomposition performance was tested according to the following method. The test process is as follows: PDI / Pt@TpBpy-COF (10 mg) was used as the photocatalyst and distilled water (50 ml) was used as the reaction liquid. Under visible light conditions, the efficiency of hydrogen production from the photocatalytic water decomposition of Pt@TpBpy-COF alone was low, only 69.4 μmol·h -1 ·g -1 , oxygen production is only 34.7 μmol·h -1 ·g -1 The PDI / Pt@TpBpy-COF composite material exhibited excellent photocatalytic water splitting performance, with a hydrogen production efficiency of 298.4 μmol·h -1 ·g -1 , oxygen production efficiency is 149.2 μmol·h -1 ·g -1 .

Claims

1. Preparation of a PDI / Pt@TpBpy-COF composite material, characterized in that The method proceeds as follows:

1. Preparation of PDI / Pt@TpBpy-COF composites: N,N-dimethylacetamide (DMA) solution containing Pt NPs, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and PDI were added to a heat-resistant glass tube, and o-dichlorobenzene and DMA were added in sequence. The mixture was ultrasonically treated at an ultrasonic frequency of 35 to 45 kHz for 30 to 35 min, and then 6 mol·L -1 The acetic acid solution was cyclically frozen and degassed in liquid nitrogen three times, sealed, heated at 120°C for 72h, filtered and washed several times with DMA and ethanol, and vacuum dried at 60°C to obtain a reddish-brown powder, which is the PDI / Pt@TpBpy-COF composite material.

2. The preparation of a PDI / TpBpy-COF composite material according to claim 1, characterized in that Preparation of the S-type heterojunction of PDI and TpBpy-COF described in step 1.

3. The preparation of a PDI / Pt@TpBpy-COF composite material according to claim 1, characterized in that The mass ratio of PDI to Pt@TpBpy-COF in step 1 is 2:8.

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