Preparation and Photocatalytic Water Splitting of an NH2-MIL-125 / Pt@TpBpy-COF Composite Material

Abstract

The application relates to preparation of an NH2-MIL-125 / Pt@TpBpy-COF composite material and photocatalytic decomposition of water. The application provides a novel NH2-MIL-125 / Pt@TpBpy-COF composite material, and aims to solve the problems of low light utilization and easy recombination of electron holes in the photocatalytic decomposition of water of the existing TpBpy-COF. The method comprises the following steps: (1) preparation of Pt NPs; (2) preparation of NH2-MIL-125; and (3) preparation of the NH2-MIL-125 / Pt@TpBpy-COF composite material. The preparation process is simple and effective, the reagent consumption is small, and the performance is high; and the photocatalyst provided by the application can effectively improve the problem of low photocatalytic decomposition of water efficiency. The application is applied to the field of photocatalytic decomposition of water, and experiments show that the composite material has excellent photocatalytic decomposition of water performance, the hydrogen production rate can reach 294.2 mu mol.h ‑1 ·g ‑1 under visible light irradiation, and the oxygen production efficiency is 148.8 mu mol.h ‑1 ·g ‑1。

Description

Technical Field

[0001] This invention relates to the preparation of an NH2-MIL-125 / Pt@TpBpy-COF composite material and its photocatalytic water splitting. Background Technology

[0002] With the development of human society, the energy crisis has become a global problem. Traditional fossil fuels such as oil, natural gas, and coal are increasingly depleted, and their combustion has also caused serious environmental pollution. Therefore, finding a clean and sustainable energy source has become an important task for society. Photocatalytic water splitting is an effective way to solve the energy crisis. It utilizes solar energy to decompose water into hydrogen and oxygen through a photocatalytic reaction, releasing electricity in the process. With continuous technological advancements, photocatalytic water splitting technology has made significant progress, and its development will bring more innovation and applications, promoting sustainable development. Therefore, photocatalytic water splitting technology will become one of the important means to solve the energy crisis. However, single-component photocatalysts may experience rapid recombination of photogenerated electrons and holes, leading to low separation efficiency of photogenerated carriers, thus limiting their efficiency in the photocatalytic water splitting process. Therefore, constructing heterojunctions to more effectively utilize visible light and improve electron-hole separation efficiency for better water splitting has become a new research hotspot.

[0003] Covalent organic frameworks (COFs) are a class of crystalline network structures composed of organic molecules linked by covalent bonds. Unlike traditional organic framework materials (such as metal-organic frameworks, MOFs), the framework of COFs is entirely composed of carbon, hydrogen, nitrogen, and oxygen atoms, without any metal ions or coordinating groups. COFs possess porosity and tunable structural characteristics, providing abundant pore space, which is beneficial for the adsorption and storage of gases and liquids, as well as catalytic reactions. By rationally designing and selecting organic molecular units, the pore size and surface functional groups of COFs can be controlled, thereby endowing them with specific adsorption selectivity, catalytic activity, and other properties. COFs exhibit good physical and chemical stability and have broad application potential, such as in gas separation, energy storage, catalysis, and optoelectronic devices. Due to the high tunability of the structure and properties of COFs, scientists are continuously exploring and developing new COF materials in hopes of meeting more application needs. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of easy recombination of electrons and holes and low water splitting efficiency in single-component photocatalysts, and to provide a method for preparing NH2-MIL-125 / Pt@TpBpy-COF composite material and its application in photocatalytic water splitting.

[0005] The preparation method of the NH2-MIL-125 / Pt@TpBpy-COF composite material of the present invention is carried out according to the following steps: I. Preparation of NH2-MIL-125 / Pt@TpBpy-COF composite material: An N,N-dimethylacetamide (DMA) solution containing Pt NPs, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and NH2-MIL-125 were added to a heat-resistant glass tube. Then, o-dichlorobenzene and DMA were added sequentially. The mixture was sonicated at a frequency of 35–45 kHz for 30–35 min, followed by the addition of 6 mol·L⁻¹. -1 The glacial acetic acid solution was degassed three times by circulating it in liquid nitrogen. After sealing, it was heated at 120°C for 72 hours, filtered, and washed several times with DMA and ethanol. Then, it was extracted with a Soxhlet extractor until clean and dried under vacuum at 60°C to obtain a reddish-brown powder, which is the NH2-MIL-125 / Pt@TpBpy-COF composite material. The concentration of the DMA solution containing Pt NPs used in step one is 2.96 mg / ml; The mass ratio of Pt NPs to TpBpy-COF in step one is 0.05:1; The mass ratio of NH2-MIL-125 to TpBpy-COF in step one is 1:9-5:5; The molar ratio of 5,5-diamino-2,2-bipyridine and 1,3,5-trialdehyde phloroglucinol in step one is 3:2; The volume ratio of o-dichlorobenzene, DMA, and acetic acid in step one is 0.5:1.5:0.2. After sealing as described in step one, heat at 120°C for 72 hours. The above-mentioned NH2-MIL-125 / Pt@TpBpy-COF composite material is used in the photocatalytic water splitting process.

[0006] The beneficial effects of this invention: This invention uses a solvothermal method, with 5,5-diamino-2,2-bipyridine and 1,3,5-trialdehyde phloroglucinol as raw materials, to successfully synthesize Pt@TpBpy-COF through in-situ addition of Pt NPs. However, the efficiency of this material in splitting water under visible light is relatively low at 96.0 μmol·h⁻¹. -1 ·g -1 Therefore, this invention combines Pt@TpBpy-COF with another crystalline porous material, NH2-MIL-125, to synthesize an NH2-MIL-125 / Pt@TpBpy-COF composite material. This material effectively improves the photocatalytic water splitting performance, with a hydrogen production efficiency of 201.2–294.2 μmol·h⁻¹.-1 ·g -1 The oxygen production efficiency is 100.6–148.8 μmol·h⁻¹. -1 ·g -1 . Attached Figure Description

[0007] Figure 1 X-ray powder diffraction pattern of NH2-MIL-125 / Pt@TpBpy-COF material; Figure 2 Infrared spectrum of NH2-MIL-125 / Pt@TpBpy-COF material; Figure 3 The image shows the photocatalytic water splitting performance of the NH2-MIL-125 / Pt@TpBpy-COF material. Detailed Implementation

[0008] The present invention will be further illustrated below with examples. These examples are only for illustrating the method of the present invention and do not limit the scope of application of the present invention in any way.

[0009] Example 1: The preparation of an NH2-MIL-125 / Pt@TpBpy-COF material according to this embodiment is carried out according to the following steps: I. Preparation of Pt nanoparticles: Chloroplatinic acid solution, polyvinylpyrrolidone (PVP), ethylene glycol solution containing sodium hydroxide, and ethylene glycol were added to a three-necked flask. The mixture was stirred and heated under vacuum at 180°C for 3 minutes. After cooling to room temperature, the resulting solution was centrifuged with acetone, washed several times with n-hexane, and allowed to stand for one minute to allow the n-hexane to evaporate. 2 ml of DMA was then added to disperse the Pt nanoparticles. The concentration of the chloroplatinic acid solution mentioned in step one is 7.4 mg / ml; The concentration of the ethylene glycol solution containing sodium hydroxide mentioned in step one is 0.2 mol·L⁻¹. -1 ; The volume ratio of the chloroplatinic acid solution, the ethylene glycol solution containing sodium hydroxide, and ethylene glycol in step one is 0.5:1:5. The concentration of the DMA solution containing Pt NPs mentioned in step one is 2.96 mg / ml. II. Preparation of NH2-MIL-125: Take a clean beaker, add N,N-dimethylformamide (DMF) and methanol in a certain proportion, then weigh 2-aminoterephthalic acid and add it to the beaker with the solvent mixed evenly. Under ultrasonic treatment at an ultrasonic frequency of 35-45KHz, it is completely dissolved and becomes transparent. Then add tetrabutyl titanate and ultrasonicate again until it is evenly dispersed. Transfer it to a hydrothermal synthesis reactor and place it in an oven at 150℃ for 8 hours. After the oven cools down to room temperature, filter and centrifuge and wash the product three times each with DMF and methanol. Dry the product under vacuum at 60℃ to obtain a yellow powder, which is NH2-MIL-125. The volume ratio of DMF to methanol in step two is 7:3; After being transferred to the reactor as described in step two, the mixture is heated at 150°C for 8 hours. III. Preparation of NH2-MIL-125 / Pt@TpBpy-COF composite material: An N,N-dimethylacetamide (DMA) solution containing Pt NPs, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and NH2-MIL-125 were added to a heat-resistant glass tube. Then, o-dichlorobenzene and DMA were added sequentially. The mixture was sonicated at a frequency of 35–45 kHz for 30–35 min, followed by the addition of 6 mol·L⁻¹. -1 Acetic acid solution was circulated and degassed three times in liquid nitrogen, sealed, heated at 120°C for 72 hours, filtered, and washed several times with DMA and ethanol, and then vacuum dried at 60°C to obtain a reddish-brown powder, which is the NH2-MIL-125 / Pt@TpBpy-COF composite material. The concentration of the DMA solution containing Pt NPs used in step three is 2.96 mg / ml; The mass ratio of Pt NPs to TpBpy-COF in step three is 0.05:1; The mass ratio of NH2-MIL-125 to TpBpy-COF in step three is 1:9-5:5; The molar ratio of 5,5-diamino-2,2-bipyridine and 1,3,5-trialdehyde phloroglucinol in step three is 3:2; In step three, the volume ratio of o-dichlorobenzene, DMA, and acetic acid is 0.5:1.5:0.2. After sealing as described in step three, heat at 120°C for 72 hours.

[0010] Example 2: This embodiment differs from Example 1 in that the mass of NH2-MIL-125 in step two is 2.15 mg, while the other steps and parameters are the same as in Example 1; thus, an NH2-MIL-125 / Pt@TpBpy-COF composite material (mass ratio 1:9) is obtained.

[0011] Example 3: This embodiment differs from Example 1 or 2 in that the mass of NH2-MIL-125 in step three is 4.83 mg, while the other steps and parameters are the same as in Example 1 or 2; thus, an NH2-MIL-125 / Pt@TpBpy-COF composite material (mass ratio 2:8) is obtained.

[0012] Example 4: This embodiment differs from Examples 1 to 3 in that the mass of NH2-MIL-125 in step 3 is 8.28 mg, and the other steps and parameters are the same as in Examples 1 to 3; NH2-MIL-125 / Pt@TpBpy-COF (mass ratio of 3:7) composite material is obtained.

[0013] Example 5: This embodiment differs from Examples 1 to 4 in that the mass of NH2-MIL-125 in step three is 12.88 mg, and the other steps and parameters are the same as in Examples 1 to 4; NH2-MIL-125 / Pt@TpBpy-COF (mass ratio of 4:6) composite material is obtained.

[0014] Example 6: This embodiment differs from Examples 1 to 4 in that the mass of NH2-MIL-125 in step 3 is 19.32 mg, and the other steps and parameters are the same as in Examples 1 to 5; NH2-MIL-125 / Pt@TpBpy-COF (mass ratio of 5:5) composite material is obtained.

[0015] To verify the beneficial effects of this invention, the following experiments were conducted: To investigate the photocatalytic decomposition effect of the NH2-MIL-125 / Pt@TpBpy-COF material, its visible light photocatalytic decomposition performance was tested according to the following method. The test procedure is as follows: NH2-MIL-125 / Pt@TpBpy-COF (10 mg) was used as the photocatalyst, and distilled water was used as the reaction solution. Under visible light, the photocatalytic decomposition efficiency of Pt@TpBpy-COF alone for hydrogen production from water was relatively low, only 96.0 μmol·h⁻¹. -1 ·g -1 Oxygen production was only 40.6 μmol·h⁻¹ -1 ·g -1 The NH2-MIL-125 / Pt@TpBpy-COF composite material exhibited excellent photocatalytic water splitting performance, with a photocatalytic hydrogen production efficiency of 294.2 μmol·h⁻¹. -1 ·g -1 The oxygen production efficiency was 148.8 μmol·h⁻¹. -1 ·g -1 .

Claims

1. A method for preparing an NH2-MIL-125 / Pt@TpBpy-COF composite material, characterized in that, This method is performed in the following steps: I. Preparation of NH2-MIL-125 / Pt@TpBpy-COF composite material: An N,N-dimethylacetamide (DMA) solution containing Pt NPs, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and NH2-MIL-125 were added to a heat-resistant glass tube. Then, o-dichlorobenzene and DMA were added sequentially. The mixture was sonicated at 35-45 kHz for 30-35 min, followed by the addition of 6 mol·L⁻¹. -1 Acetic acid solution was circulated and degassed three times in liquid nitrogen, sealed, heated at 120 °C for 72 h, filtered, and washed several times with DMA and ethanol, and then vacuum dried at 60 °C to obtain a reddish-brown powder, which is the NH2-MIL-125 / Pt@TpBpy-COF composite material.

2. The method for preparing an NH2-MIL-125 / Pt@TpBpy-COF composite material according to claim 1, characterized in that, The mass ratio of NH2-MIL-125 to Pt@TpBpy-COF in step one is 3:7.

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