Porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst and its preparation and application

Abstract

The present invention discloses a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst and its preparation and application, which relates to the technical field of photocatalysts. In the present invention, zinc indium sulfide nanosheets are directionally induced to grow on the framework of porphyrin-based MOF by a solvothermal method to construct nanotubes with a binary shell heterostructure. The nanotubes have abundant active sites, well-matched band gaps, strong visible light capture ability and excellent charge migration efficiency, showing remarkable photocatalytic hydrogen production activity. Under visible light irradiation, the hydrogen evolution rate is as high as over 8000 μmol g–1 h–1, which is more than 20 times that of pure zinc indium sulfide.

Description

Technical Field:

[0001] The present invention relates to the technical field of photocatalysts, and particularly relates to a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst and its preparation and application. Background Art:

[0002] Due to its conjugated macrocyclic structure and adjustable active sites, porphyrin-based MOF shows extraordinary potential in the catalytic field. Porphyrin-based MOF is usually synthesized by selecting appropriate metal salts and porphyrin ligands, and a network structure is constructed by precisely controlling its synthesis conditions, involving single metal clusters / nodes and secondary building units. Many porphyrin-based MOFs have been widely used as photocatalysts for photocatalytic reactions, including nitrogen fixation reaction, CO2 reduction reaction, water splitting hydrogen / oxygen evolution reaction, degradation or transformation of organic compounds.

[0003] However, the performance of single-metal coordination porphyrin-based MOF photocatalysts is still limited by the rapid recombination of photoexcited electrons and holes. Therefore, the preparation of composite materials and the construction of multi-metal active sites have been proven to be important strategies to improve photocatalytic activity. It is worth emphasizing that to address the energy crisis, various photocatalysts have been developed for the field of efficient photocatalytic hydrogen production, including titanium dioxide, carbon nitride, zinc indium sulfide, etc. Among them, zinc indium sulfide, as a ternary sulfide with a layered structure and stable chemical properties, is a promising visible light-responsive photocatalyst. However, the photocatalytic activity of single-component catalysts is also still restricted by the rapid recombination of photoinduced electrons and holes. Therefore, the development of multi-component composite photocatalysts is of great significance for improving the mobility of carriers. Summary of the Invention:

[0004] The technical problem to be solved by the present invention is to provide a preparation method of a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst. By the solvothermal method, a porphyrin-based MOF / zinc indium sulfide heterojunction is successfully constructed, which broadens the visible light response range of pure zinc indium sulfide, successfully solves the disadvantage of high recombination rate of photogenerated electrons and holes in single-metal porphyrin-based MOF and pure zinc indium sulfide, realizes the efficient transfer of electrons, and further improves the photocatalytic performance, having very important practical application prospects.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] One of the objects of the present invention is to provide a preparation method of a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst, including the following steps:

[0007] S1. React a metal salt with 5,10,15,20-tetra(4-carboxyphenyl)porphyrin to obtain a porphyrin-based MOF;

[0008] S2. The porphyrin-based MOF reacts with a zinc source, an indium source, and a sulfur source to obtain a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst.

[0009] Preferably, the metal salt in step S1 is a hydrochloride or nitrate of Cu 2+ , Co 2+ , Ni 2+ , Fe 3+ , Ru 3+ , Pt 2+ , Pd 2+ or at least one of them.

[0010] Preferably, the mass ratio of the metal salt to 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin in step S1 is 1:(2-6).

[0011] Preferably, the reaction temperature of the metal salt and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin in step S1 is 110-140 °C, and the reaction time is 3-6 h.

[0012] Preferably, the zinc source in step S2 is at least one of zinc acetate and zinc chloride; the indium source is at least one of indium nitrate and indium chloride; the sulfur source is at least one of thioacetamide and thiourea.

[0013] Preferably, the mass ratio of the porphyrin-based MOF to the zinc source, the indium source, and the sulfur source in step S2 is 1:(1-1.5):(2-3):(5-10). By regulating the content of the porphyrin-based MOF, the dispersion degree of zinc indium sulfide nanosheets is controlled, and the absorption intensity of visible light is adjusted.

[0014] Preferably, the reaction temperature of the porphyrin-based MOF with the zinc source, the indium source, and the sulfur source in step S2 is 120-160 °C, and the reaction time is 4-10 h.

[0015] The second object of the present invention is to provide a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst obtained according to the foregoing preparation method. The present invention uses the porphyrin-based MOF as a carrier, utilizes the active sites of the carboxyl groups on the periphery of the porphyrin, and directionally induces the encapsulation of zinc indium sulfide nanosheets to form a tight heterostructure. Density functional theory (DFT) calculations show that the construction of the heterojunction establishes an electron transport channel with strong covalent interaction, and electrons accumulate and are consumed at the interface between the porphyrin-based MOF and zinc indium sulfide. The electron transfer pathway is from the porphyrin-based MOF to zinc indium sulfide.

[0016] A third object of the present invention is to provide an application of the aforementioned porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst in photocatalytic hydrogen production. This composite photocatalyst is used for photocatalytic hydrogen production under visible light irradiation. The formation of the heterojunction enables electrons to transition from the conduction band of the porphyrin-based MOF to the conduction band of zinc indium sulfide, greatly accelerating charge separation and thereby enhancing the photocatalytic hydrogen production activity.

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

[0018] 1. In the present invention, zinc indium sulfide nanosheets are directionally induced to grow on the framework of the porphyrin-based MOF by a solvothermal method to construct nanotubes with a binary shell heterostructure. These nanotubes have abundant active sites, well-matched band gaps, strong visible light capture ability, and excellent charge migration efficiency, showing remarkable photocatalytic hydrogen production activity. Under visible light irradiation, the hydrogen evolution rate is as high as 8000 μmol g –1 h –1 or more, which is more than 20 times the hydrogen evolution rate of pure zinc indium sulfide.

[0019] 2. The present invention provides a convenient and advanced prototype for synthesizing binary heterojunction photocatalysts with excellent charge separation and transfer efficiency, and is expected to be widely applied in actual production. Description of the Drawings:

[0020] Figure 1 are three-dimensional simulated structure diagrams of palladium porphyrin-based MOF (a), zinc indium sulfide (b), and palladium porphyrin-based MOF / zinc indium sulfide (c) prepared in Example 1 of the present invention;

[0021] Figure 2 are the N1s spectrograms of XPS of the raw material 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin and the palladium porphyrin MOF prepared in Example 1 of the present invention;

[0022] Figure 3 are the scanning electron micrographs of zinc indium sulfide (a), palladium porphyrin-based MOF (b), and palladium porphyrin-based MOF / zinc indium sulfide (c) prepared in Example 1 of the present invention;

[0023] Figure 4 are the solid absorbance curves of zinc indium sulfide, palladium porphyrin-based MOF, and palladium porphyrin-based MOF / zinc indium sulfide prepared in Example 1 of the present invention;

[0024] Figure 5 are the photoluminescence (PL) spectra of zinc indium sulfide, palladium porphyrin-based MOF, and palladium porphyrin-based MOF / zinc indium sulfide prepared in Example 1 of the present invention. Detailed Embodiments:

[0025] In order to make the technical means, creative features, achieved purposes and effects realized by the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments and illustrations.

[0026] Example 1

[0027] Preparation of palladium porphyrin MOF: 0.5 g of palladium nitrate, 1.20 g of 5,10,15,20-tetra(4-carboxyphenyl)porphyrin, and 70 mL of N,N-dimethylformamide were added to a beaker, stirred and sonicated to obtain a mixed solution; then the mixed solution was transferred to a reaction kettle and placed in an oven at 120 °C for 4 h, cooled to room temperature, filtered, washed, and dried at 70 °C to obtain palladium porphyrin-based MOF powder.

[0028] Preparation of zinc indium sulfide: 0.4 g of zinc chloride, 1.1 g of indium chloride, and 2.5 g of thioacetamide were dissolved in 30 mL of deionized water, stirred and sonicated to obtain a mixed solution; then the mixed solution was transferred to a reaction kettle and placed in an oven at 150 °C for 6 h, cooled to room temperature, filtered, washed, and dried at 80 °C to obtain zinc indium sulfide powder.

[0029] Preparation of heterostructured palladium porphyrin-based MOF / zinc indium sulfide: 0.4 g of zinc chloride, 1.1 g of indium chloride, and 2.5 g of thioacetamide were dissolved in 30 mL of deionized water, and then 0.3 g of the palladium porphyrin-based MOF powder prepared in Example 1 was added, stirred and sonicated to obtain a mixed solution; then the mixed solution was transferred to a reaction kettle and placed in an oven at 150 °C for 6 h, cooled to room temperature, filtered, washed, and dried at 80 °C to obtain palladium porphyrin-based MOF / zinc indium sulfide powder.

[0030] As Figure 2 shown, in the N1s spectrum of 5,10,15,20-tetra(4-carboxyphenyl)porphyrin, the C=N-C and C-NH-C groups of the porphyrin ring were observed, and the corresponding binding energies were located at 397.2 and 399.5 eV, respectively; in the N1s spectrum of palladium porphyrin MOF, an obvious change in the binding energy of N after palladium modification of porphyrin was observed, and the binding energy located at 398.2 eV corresponded to the Pd-N group, indicating that the central ring of 5,10,15,20-tetra(4-carboxyphenyl)porphyrin was metallized with palladium metal to form palladium porphyrin-based MOF.

[0031] From Figure 3 it can be seen that the morphological structure of zinc indium sulfide is a microsphere formed by aggregated nanosheets, the palladium porphyrin-based MOF is a rectangular block structure, and after the formation of the palladium porphyrin-based MOF / zinc indium sulfide heterojunction, it can be observed that the zinc indium sulfide nanosheets are uniformly dispersed on the skeleton of the palladium porphyrin MOF.

[0032] From Figure 4It can be seen that the palladium porphyrin-based MOF / zinc indium sulfide heterojunction synthesized in Example 1 has a significantly enhanced visible light absorption range.

[0033] Weigh 50 mg of the palladium porphyrin-based MOF powder prepared in Example 1, add it to 100 mL of an aqueous solution containing 10 mL of triethanolamine, install the reactor and evacuate it. Using a 300 W xenon lamp as the light source, a gas chromatograph (GC9790II-PLL-01) with a TCD detector and argon as the carrier gas is used to detect the generated hydrogen. After calculation, the hydrogen evolution rate reaches 590 μmol g –1 h –1 or more.

[0034] Weigh 50 mg of the palladium porphyrin-based MOF / zinc indium sulfide powder prepared in Example 1, add it to 100 mL of an aqueous solution containing 10 mL of triethanolamine, install the reactor and evacuate it. Using a 300 W xenon lamp as the light source, a gas chromatograph (GC9790II-PLL-01) with a TCD detector and argon as the carrier gas is used to detect the generated hydrogen. After calculation, the hydrogen evolution rate is as high as 8000 μmol g – 1 h –1 or more, which is more than 20 times the hydrogen evolution rate of pure zinc indium sulfide.

[0035] Weigh 50 mg of the zinc indium sulfide powder prepared in Example 1, add it to 100 mL of an aqueous solution containing 10 mL of triethanolamine, install the reactor and evacuate it. Using a 300 W xenon lamp as the light source, a gas chromatograph (GC9790II-PLL-01) with a TCD detector and argon as the carrier gas is used to detect the generated hydrogen. After calculation, the hydrogen evolution rate is 300 μmol g –1 h –1 or more.

[0036] From Figure 5 it can be seen that compared with the single-component photocatalyst, the PL emission intensity of the palladium porphyrin-based MOF / zinc indium sulfide heterojunction decreases sharply, confirming that the preparation of the binary shell heterojunction is beneficial to suppressing the recombination of photoexcited electron-hole pairs, thereby improving the photocatalytic hydrogen production performance.

[0037] Example 2

[0038] Preparation of the heterostructured palladium porphyrin-based MOF / zinc indium sulfide: Dissolve 0.8 g of zinc chloride, 2.5 g of indium chloride and 6.1 g of thioacetamide in 60 mL of deionized water, then add 0.9 g of the palladium porphyrin-based MOF powder prepared in Example 1, stir and ultrasonicate to obtain a mixed solution; then transfer the mixed solution to a reaction kettle, place it in an oven at 160 °C for reaction for 5 h, cool to room temperature, filter, wash, and dry at 70 °C to obtain the palladium porphyrin-based MOF / zinc indium sulfide powder.

[0039] Example 3

[0040] Preparation of palladium porphyrin-based MOF / zinc indium sulfide heterostructure: Dissolve 0.7 g of zinc acetate, 2.4 g of indium nitrate and 4.2 g of thiourea in 50 mL of deionized water, then add 0.7 g of the palladium porphyrin-based MOF powder prepared in Example 1, stir and ultrasonicate to obtain a mixed solution; then transfer the mixed solution to a reaction kettle, place it in an oven at 155 °C for reaction for 5 h, cool to room temperature, filter, wash, and dry at 60 °C to obtain palladium porphyrin-based MOF / zinc indium sulfide powder.

[0041] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Application of a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst in photocatalytic hydrogen production. The preparation method of the porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst comprises the following steps: S1. React a metal salt with 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin to obtain a porphyrin-based MOF; S2. React the porphyrin-based MOF with a zinc source, an indium source, and a sulfur source to obtain a porphyrin-based MOF / zinc indium sulfide heterojunction composite photocatalyst; The metal salt described in step S1 is the hydrochloride or nitrate of Pd 2+ ; In step S1, the mass ratio of the metal salt to 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin is 1:(2-6).

2. The application according to claim 1, wherein: In step S1, the reaction temperature of the metal salt and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin is 110-140 °C, and the reaction time is 3-6 h.

3. The application according to claim 1, wherein: In step S2, the zinc source is at least one of zinc acetate and zinc chloride; the indium source is at least one of indium nitrate and indium chloride; the sulfur source is at least one of thioacetamide and thiourea.

4. The application according to claim 1, wherein: In step S2, the mass ratio of the porphyrin-based MOF to the zinc source, the indium source, and the sulfur source is 1:(1-1.5):(2-3):(5-10).

5. The application according to claim 1, wherein: In step S2, the reaction temperature of the porphyrin-based MOF with the zinc source, the indium source, and the sulfur source is 120-160 °C, and the reaction time is 4-10 h.

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