Application of covalent triazine-based frameworks linked by bipyridine groups in photocatalytic decomposition of water for simultaneous hydrogen production and hydrogen peroxide

Abstract

The application discloses application of a bipyridyl group connected covalent triazine organic framework material in photocatalytic decomposition of water to simultaneously produce hydrogen and hydrogen peroxide, and belongs to the field of photocatalytic materials. The bipyridyl group connected covalent triazine organic framework material is synthesized by taking 2,4,6-tri(4-formylphenyl)-1,3,5-triazine and 5,5'-diamino-2,2'-bipyridine as reaction monomers, and then Pt is modified on the material by reduction to obtain a photocatalytic material capable of efficiently catalytically decomposing water into H2 and H2O2 under visible light. The bipyridyl group connected covalent triazine organic framework material synthesized in the application has more microporous structures, a narrower band gap width and a suitable energy band structure, and after loading the metal Pt on the material, the material can photocatalytically decompose water into H2 and H2O2 without using a sacrificial agent, so the material has great application potential.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials, specifically relating to the application of a covalent triazine organic framework material linked by a bipyridine group in the photocatalytic splitting of water to produce hydrogen and hydrogen peroxide (H2O2). Background Technology

[0002] Since the beginning of the new century, with the increasing demand for energy and awareness of environmental protection, covalent organic framework materials have become a hot research topic in modern science. The application of covalent organic framework materials in photocatalytic hydrogen production has been widely studied, but research on photocatalytic water splitting without sacrificial agents is relatively limited. This invention provides a bipyridine-linked covalent triazine organic framework material, which is a covalent organic framework formed by the condensation of aldehyde and amine groups to form imine bonds. It possesses excellent solvent and thermal stability, unique photoelectric properties, and good light absorption. With a suitable band gap and band structure, it meets the thermodynamic conditions for photocatalytic water splitting and can catalytically decompose water into clean energy sources such as H2 and H2O2 under visible light irradiation, which is of great significance for solving the Earth's energy problem. Summary of the Invention

[0003] The purpose of this invention is to provide an application of a bipyridine-linked covalent triazine organic framework material in the photocatalytic splitting of water to produce hydrogen and hydrogen peroxide.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The application of a bipyridine-linked covalent triazine organic framework material in the photocatalytic decomposition of water to produce hydrogen and hydrogen peroxide involves synthesizing a bipyridine-linked covalent triazine organic framework material TFPT-BPY COF using 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine (TFTP) and 5,5'-diamino-2,2'-bipyridine (BPY) as reactants. Then, Pt is post-functionalized on this material via reduction to obtain a photocatalytic material Pt@TFPT-BPY COF capable of efficiently decomposing water into H2 and H2O2 using visible light without the use of sacrificial agents.

[0006] Furthermore, the preparation of the photocatalytic material Pt@TFPT-BPY COF includes the following steps:

[0007] 1) TFTP and BPY were added to a mixed solution of mesitylene and dioxane, and acetic acid solution was added as a catalyst. The mixture was rapidly frozen and thawed in a liquid nitrogen bath, then evacuated three times until the internal pressure was 0 mbar, and then flame-sealed. The sealed reaction system was then heated from room temperature to 120°C and kept at that temperature for 3 days, and then cooled to room temperature. After filtration, washing and drying, the covalent triazine organic framework material TFPT-BPY COF was obtained.

[0008] 2) Disperse the obtained TFPT-BPY COF with 10 mg / mL of chloroplatinic acid hexahydrate in methanol, sonicate and stir for 1.5-3 h, then rotary evaporate the solution, add ice methanol and NaBH4 aqueous solution to the obtained powder, continue stirring for 2-6 h, and wash to obtain the photocatalytic material Pt@TFPT-BPY COF.

[0009] Furthermore, the molar ratio of TFTP and BPY used in step 1) is 2:3.

[0010] Further, in step 1), the volume ratio of mesitylene and dioxane in the mixed solution is 1:1.

[0011] Further, the concentration of the acetic acid solution in step 1) is 3~6 mol / L, and its amount is 1 / 10 of the volume of the mixed solution.

[0012] Furthermore, the volume of icy methanol used in step 2) is 50 times the volume of the aqueous solution of chloroplatinic acid hexahydrate.

[0013] Furthermore, in step 2), the amount of NaBH4 used is 10-12 times the mass of the Pt precursor used, and the concentration of the NaBH4 aqueous solution is 0.5 mol / L.

[0014] Furthermore, the Pt loading in the obtained photocatalytic material Pt@TFPT-BPY COF is 3wt%.

[0015] The specific application method of the photocatalytic material Pt@TFPT-BPY COF in photocatalytic water splitting to produce hydrogen and hydrogen peroxide is to add the photocatalytic material Pt@TFPT-BPY COF and deionized water into a reactor, and put the reaction system under vacuum. Then, under stirring conditions at 20°C, the reaction is carried out using a 300W xenon lamp with a 420nm cutoff filter as the light source.

[0016] This invention utilizes a solvothermal method to prepare a bipyridine-linked covalent triazine organic framework material under relatively mild conditions. This material is a type of crystalline porous material with a periodic network structure linked by covalent bonds, exhibiting a well-defined void structure, ordered pore structure, large specific surface area, high porosity, and low density. It possesses semiconductor properties, absorbing visible light in a certain wavelength range and exciting photoelectrons. Furthermore, the structural units of the covalent organic framework typically have a rigid π-type framework and multiple reaction sites, allowing for the flexible design of different functional groups within the framework. Pt is reduced and loaded onto this material using NaBH4 to prepare a photocatalytic material. The resulting photocatalytic material can catalytically decompose water into H2 and H2O2 in the visible light range without the use of sacrificial agents. This method is reproducible and offers good economic and environmental benefits.

[0017] The beneficial effects of this invention are as follows:

[0018] 1) This invention utilizes a solvothermal method to catalyze the reaction of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 5,5'-diamino-2,2'-bipyridine in a mixed solvent of mesitylene and dioxane to obtain a covalent organic framework material with bipyridine and triazine groups. This material has a large number of microporous structures, a narrow band gap, and a suitable band structure. After loading a metal onto this covalent organic framework material, it can perform photocatalytic water splitting under visible light.

[0019] 2) The process conditions of this invention are simple and highly reproducible; the chemical reagents and equipment used are reasonably priced, readily available, highly applicable, have high industrial application value, and are easy to promote and utilize. Attached Figure Description

[0020] Figure 1 The reaction principle diagram for preparing TFPT-BPY COF.

[0021] Figure 2 The X-ray powder diffraction pattern of the TFPT-BPY COF prepared in Example 1 is shown.

[0022] Figure 3 The Fourier transform infrared spectrum of the TFPT-BPY COF prepared in Example 1.

[0023] Figure 4 Scanning electron microscope image of TFPT-BPY COF prepared in Example 1.

[0024] Figure 5 Scanning electron microscope image of Pt@TFPT-BPY COF prepared in Example 2.

[0025] Figure 6The image shows the performance of Pt@TFPT-BPY COF photocatalytic water splitting in Example 3. Detailed Implementation

[0026] The preparation of a photocatalytic material Pt@TFPT-BPY COF for photocatalytic water splitting to produce hydrogen and hydrogen peroxide includes the following steps:

[0027] 1) TFTP and BPY were added to a mixed solution of mesitylene and dioxane (1:1, v / v) at a molar ratio of 2:3, and 3-6 mol / L acetic acid solution (1 / 10 of the volume of the mixed solution) was added as a catalyst. The mixture was rapidly frozen and thawed in a liquid nitrogen bath, then evacuated three times until the internal pressure reached 0 mbar, and then flame-sealed. The sealed reaction system was then heated from room temperature to 120°C and held at that temperature for 3 days, then cooled to room temperature. After filtration, washing, and drying, the covalent triazine organic framework material TFPT-BPY COF (e.g.) was obtained. Figure 1 );

[0028] 2) Disperse the obtained TFPT-BPY COF and chloroplatinic acid hexahydrate aqueous solution in methanol, sonicate and stir for 1.5-3 h, then rotary evaporate the solution, and add 50 times the volume of chloroplatinic acid hexahydrate aqueous solution in ice-cold methanol and 0.5 mol / L NaBH4 solution (the amount of NaBH4 is 10-12 times the mass of Pt precursor) to the obtained powder, continue stirring for 2-6 h, and wash to obtain Pt@TFPT-BPY COF photocatalyst with a Pt loading of 3 wt%.

[0029] To make the objectives, technical solutions, and advantages of this invention clearer and easier to understand, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined as long as they do not conflict with each other.

[0030] Example 1

[0031] The synthetic steps for bipyridine-linked covalent triazine organic framework materials are as follows:

[0032] 2,4,6-Tris(4-aldehydephenyl)-1,3,5-triazine (15.74 mg, 0.04 mmol) and 5,5'-diamino-2,2'-bipyridine (11.17 mg, 0.06 mmol) were placed in a Pyrex tube (approximately 5 mL in volume, 20 cm in length, and 1 cm in diameter). 0.5 mL of mesitylene and 0.5 mL of dioxane were added, and the mixture was sonicated for 20 minutes to ensure uniform dispersion. Then, 0.1 mL of 3 M acetic acid solution was added. The Pyrex tube was then rapidly frozen and thawed in a liquid nitrogen bath, followed by three evacuations to an internal pressure of 0 mbar, and then flame-sealed. The Pyrex tube was placed in an oven at 120 °C for 3 days. The precipitate was collected by filtration, washed three times with methanol, acetone, and tetrahydrofuran, and dried under vacuum overnight at 60 °C to obtain a solid powder, TFPT-BPY COF.

[0033] Figure 2 The X-ray powder diffraction pattern of the prepared TFPT-BPY COF is shown in the figure. As can be seen from the figure, the peak position is around 2.5° and there are no residual peaks of the two monomers, which is roughly consistent with the results of software simulation.

[0034] Figure 3 The image shows the Fourier transform infrared spectrum of the prepared TFPT-BPY COF. As can be seen from the figure, TFPT-BPY COF exhibits high activity at 1610 cm⁻¹. -1 The newly emerging characteristic peak can be regarded as the stretching vibration of the imine bond (-C=N-) formed by the condensation of aldehyde and amino groups. The weakening of the -C=O- stretching vibration of TFPT monomer and the -NH2- stretching vibration of Bpy monomer also confirms the synthesis of TFPT-BPY COF.

[0035] Example 2

[0036] The synthesis steps of Pt@TFPT-BPY COF are as follows:

[0037] The covalent triazine organic framework material TFPT-BPY COF (20 mg), 10 mg / mL chloroplatinic acid hexahydrate aqueous solution (60 μL), and methanol (3 mL) prepared in Example 1 were placed in a round-bottom flask and ultrasonically mixed for 5 min. The mixture was then stirred on a magnetic stirrer for 1 h. The stirred solution was then rotary evaporated to obtain TFPT-BPY COF containing Pt metal ions. Ice methanol (3 mL) and 0.5 M NaBH4 solution (1 mL) were added to the obtained powder, and stirring was continued for 2 h. After washing with a large amount of deionized water, the powder was placed in a vacuum drying oven at 60 °C and dried for 12 h to obtain Pt@TFPT-BPY COF with a loading of 3 wt%.

[0038] Figure 4 ,5 The images show scanning electron microscope (SEM) images of TFPT-BPY COF and Pt@TFPT-BPY COF, respectively. The comparison reveals that both the TFPT-BPY COF and Pt@TFPT-BPY COF exhibit a hollow rod-like structure composed of stacked nanosheets, indicating that Pt loading did not disrupt the structure of TFPT-BPY COF.

[0039] Example 3

[0040] The steps for applying Pt@TFPT-BPY COF in photocatalytic water splitting are as follows:

[0041] Weigh 10 mg of Pt@TFPT-BPY COF prepared in Example 2, add 50 mL of deionized water, stir and mix evenly, and sonicate in an ultrasonic machine for 20 min. Put the mixture into a quartz glass reactor, and bring the system to a vacuum state by three vacuuming processes. Irradiate the system for 4 hours with a 300W xenon lamp with a 420 nm cutoff filter as the light source. Detect the gas composition after the photocatalytic reaction using gas chromatography, and detect the H2O2 content in the photocatalytic reaction system using ultraviolet-visible absorption spectroscopy. This is used to test the water-decomposing performance of Pt@TFPT-BPY COF.

[0042] Figure 6 The graph shows the photocatalytic water splitting performance of Pt@TFPT-BPY COF. As can be seen from the graph, the H2 production after 4 hours of illumination is 3.64 μmol. Simultaneously, the H2O2 production calculated by UV-Vis absorption spectroscopy is 3.22 μmol, with a molar ratio of approximately 1:1.

[0043] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. The application of a bipyridine-linked covalent triazine organic framework material in photocatalytic water splitting to produce hydrogen and hydrogen peroxide, characterized in that: A covalent triazine organic framework material with a bipyridine group was synthesized using 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 5,5'-diamino-2,2'-bipyridine as reactants. Then, Pt was post-functionalized on it by reduction to obtain a photocatalytic material that can efficiently decompose water into H2 and H2O2 using visible light without the use of sacrificial agents.

2. The application according to claim 1, characterized in that: The synthesis of the bipyridine-linked covalent triazine organic framework material specifically involves rapidly freezing and thawing a mixture of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 5,5'-diamino-2,2'-bipyridine, and acetic acid solution in a liquid nitrogen bath. The mixture is then evacuated three times until the internal pressure reaches 0 mbar, followed by flame sealing. The sealed reaction system is then heated from room temperature to 120°C, held at that temperature for 3 days, cooled to room temperature, filtered, washed, and dried.

3. The application according to claim 2, characterized in that: The molar ratio of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 5,5'-diamino-2,2'-bipyridine used was 2:

3.

4. The application according to claim 2, characterized in that: The concentration of the acetic acid solution used is 3~6 mol / L.

5. The application according to claim 2, characterized in that: The mixture also contains mesitylene and dioxane as solvents, with a volume ratio of 1:

1.

6. The application according to claim 1, characterized in that: The post-functionalization modification specifically involves dispersing a covalent triazine organic framework material in methanol, adding an aqueous solution of a Pt precursor, sonicating, rotary evaporating, and then adding NaBH4 and stirring for 2-6 hours to reduce and load Pt onto the bipyridine-linked covalent triazine organic framework material.

7. The application according to claim 6, characterized in that: The concentration of the aqueous solution of the Pt precursor was 10 mg / mL, and the Pt precursor used was H2PtCl6▪6H2O.

8. The application according to claim 6, characterized in that: The amount of NaBH4 used is 10-12 times the mass of the Pt precursor used.

9. The application according to claim 1, characterized in that: The Pt loading in the photocatalytic material is 3 wt%.

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