Application of ZnIn2S4 / UiO-66-NH2 composite photocatalyst in photocatalytic reduction of carbon dioxide

Abstract

This invention relates to the application of a ZnIn₂S₄ / UiO-66-NH₂ heterojunction composite photocatalyst in the photocatalytic reduction of carbon dioxide, belonging to the field of photocatalytic materials and carbon resource utilization technology. The composite catalyst is constructed by in-situ growth of ZnIn₂S₄ on the surface of UiO-66-NH₂ via a solvothermal method, wherein the mass fraction of UiO-66-NH₂ is 20%–80%. This method is simple, mild, and produces a tightly bonded material, which facilitates the separation and migration of photogenerated electron-hole pairs and enhances the adsorption and activation capacity for CO₂ molecules. When applied to a visible light-driven CO₂ reduction reaction system, the catalyst achieves highly efficient conversion of CO₂ to carbon monoxide and / or formic acid in the presence of a sacrificial agent, exhibiting high generation rate and selectivity, and good cycle stability. This invention provides a structurally controllable, high-performance composite photocatalytic material and its application scheme for CO₂ resource utilization, with promising application prospects.

Description

Technical Field

[0001] This invention relates to the application of a ZnIn2S4 / UiO-66-NH2 (amino-functionalized metal-organic framework) composite photocatalyst in the photocatalytic reduction of carbon dioxide, specifically the application of a ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst in the photocatalytic reduction of carbon dioxide (CO2) to prepare carbon monoxide (CO) and / or formic acid (HCOOH). This invention achieves high CO2 conversion efficiency and product selectivity under visible light-driven conditions, significantly improves the separation efficiency and catalytic stability of photogenerated carriers, and shows promising application prospects. Background Technology

[0002] In recent years, with the massive consumption of fossil fuels and the continuous increase in greenhouse gas emissions, carbon dioxide (CO2) concentrations have been rising, triggering a series of environmental problems such as global climate change. How to achieve efficient CO2 conversion and resource utilization has become a research hotspot in the energy and environment fields. Photocatalytic CO2 reduction technology utilizes solar energy to drive semiconductor materials to convert CO2 into high-value-added chemicals such as carbon monoxide, formic acid, and methanol. However, due to the stable molecular structure of CO2, the high bond energy of the C=O bond, and problems such as the rapid recombination rate of photogenerated electrons and holes and low quantum efficiency in the photocatalytic process, the conversion efficiency and product selectivity of existing photocatalytic systems still need to be improved.

[0003] Metal sulfide semiconductor materials such as ZnIn₂S₄ possess suitable band gap structures and good visible light response capabilities, attracting widespread attention in photocatalytic CO₂ reduction and organic pollutant degradation. ZnIn₂S₄ has a layered structure, a large specific surface area, and a relatively negative conduction band position, theoretically favorable for CO₂ reduction reactions. However, the rapid recombination of photogenerated electrons and holes in its single-component system limits further improvements in its catalytic performance.

[0004] Metal-organic frameworks (MOFs) exhibit unique advantages in photocatalysis due to their high specific surface area, tunable structure, and abundant active sites. Among them, the amino-functionalized zirconium-based MOF, UiO-66-NH2, possesses excellent chemical stability and visible light response characteristics, enabling it to participate in photocatalytic reactions through ligand-to-metal charge transfer. Furthermore, the porous structure of UiO-66-NH2 facilitates the adsorption and activation of CO2 molecules. However, UiO-66-NH2 itself has poor electrical conductivity and limited photogenerated carrier migration efficiency, resulting in relatively low catalytic activity when used alone.

[0005] To overcome the limitations of single materials, constructing heterojunction composite photocatalytic systems has become an important strategy for improving catalytic performance. By combining ZnIn2S4 with UiO-66-like materials, effective charge separation channels can be formed at the interface, promoting the spatial separation of photogenerated electrons and holes, and improving reaction activity and stability. Previous studies have explored the ZnIn2S4 / UiO-66 composite system. For example, in published patent CN116103499A, a ZnIn2S4 / UiO-66 photocatalyst was loaded onto a graphite felt substrate to prepare a photoelectrode, constructing a dual-photoelectrode system, which achieved photoelectrochemical leaching of valuable metal resources from spent lithium batteries. This method is simple to operate, has mild reaction conditions, does not require strong acids, strong bases, or additional redox agents, and exhibits high metal leaching rates and environmental friendliness, indicating that the ZnIn2S4 / UiO-66 system has good application potential in the field of photoelectrocatalysis.

[0006] Furthermore, patent CN117225475A reports a UiO-66-NH2 / IISERP-COF12 composite material. After preparing UiO-66-NH2 via a solvothermal method, the composite structure was constructed in situ for photocatalytic CO2 reduction. Under 300 W xenon lamp irradiation, the CO generation rate was significantly higher than that of single-component materials. This technology effectively improves the problem of easy recombination of photogenerated electrons and holes by constructing a heterostructure, proving that the composite strategy is an effective way to improve the efficiency of photocatalytic CO2 reduction. However, this system is mainly based on the coupling between MOF and COF materials, and there is still room for improvement in overall conductivity and reduction capacity.

[0007] In summary, although existing technologies have improved photocatalytic efficiency to some extent by constructing heterojunctions or composite structures, the following problems still exist: First, the interfacial bandgap matching and charge migration path design are not yet sufficient, resulting in room for improvement in the photogenerated carrier separation efficiency; second, the adsorption and activation capabilities of catalysts for CO2 molecules need to be enhanced; and third, the structural stability and large-scale application potential of the materials still require further optimization. Therefore, developing a composite photocatalytic material with tight interfacial bonding, reasonable bandgap structure matching, high carrier separation efficiency, and excellent CO2 reduction activity remains of significant research importance and application value. Summary of the Invention

[0008] The purpose of this invention is to provide an application of a ZnIn2S4 / UiO-66-NH2 composite photocatalyst in the photocatalytic reduction of carbon dioxide. This catalyst is produced by growing ZnIn2S4 on the surface of UiO-66-NH2 via an in-situ solvothermal method, constructing a tightly bonded heterojunction structure that forms an effective charge transport channel. The constructed heterojunction structure facilitates the separation and directional migration of photogenerated electron-hole pairs, improving visible light utilization efficiency and reduction reaction activity.

[0009] Applying the aforementioned composite photocatalyst to the photocatalytic reduction of CO2 enables highly efficient conversion of CO2 to carbon monoxide (CO) and / or formic acid (HCOOH), solving the problems of severe photogenerated carrier recombination, low conversion efficiency, and insufficient product selectivity in existing single ZnIn2S4 or UiO-66-NH2 catalytic systems. The preparation method of this invention is simple, operates under mild conditions, has adjustable composition ratios, and exhibits a stable composite interface, making it suitable for large-scale preparation.

[0010] This invention enhances the adsorption and activation capacity of materials for CO2 by constructing a structurally stable and tightly coupled ZnIn2S4 / UiO-66-NH2 heterojunction composite system. Simultaneously, it optimizes the bandgap matching relationship and improves the utilization efficiency of photogenerated electrons in the reduction reaction. Under visible light irradiation, it achieves high CO2 conversion rate and target product selectivity, exhibiting good catalytic stability and recyclability, demonstrating broad application prospects in the field of CO2 resource utilization.

[0011] This invention provides an application of a ZnIn2S4 / UiO-66-NH2 composite photocatalyst in the selective reduction of CO2 to prepare CO and / or HCOOH. The preparation method of the ZnIn2S4 / UiO-66-NH2 composite photocatalyst involves introducing UiO-66-NH2 as a substrate material into a solvothermal reaction system containing a zinc source, an indium source, and a sulfur source, so that ZnIn2S4 is grown in situ on its surface to form a heterojunction structure. The mass fraction of UiO-66-NH2 is 20%–80%, preferably 30%–50%, and more preferably 40%.

[0012] This invention provides a method for preparing a ZnIn2S4 / UiO-66-NH2 composite photocatalyst. UiO-66-NH2 is introduced during the solvothermal synthesis of ZnIn2S4, allowing ZnIn2S4 to grow in situ on its surface, constructing a tightly bonded heterojunction structure. The specific steps are as follows: 1) Preparation of precursor solution Weigh 1.5 mmol ZnCl2, 1.5 mmol InCl3, and 6 mmol thioacetamide (TAA) according to the stoichiometric ratio, and add them to 60 mL of deionized water or ethylene glycol-water mixed solution; then add a certain mass of UiO-66-NH2 powder (accounting for 20%–80% of the final composite material mass, preferably 30%–50%), and ultrasonically disperse for 10 min to make it uniformly suspended.

[0013] 2) Uniformly dispersed The zinc source, indium source, sulfur source and UiO-66-NH2 were magnetically stirred at room temperature for 30 min to ensure full contact and uniform dispersion, forming a homogeneous precursor mixture solution.

[0014] 3) In-situ solvothermal growth The above mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined reactor, placed in an oven and heated to 160 °C, and the reaction was maintained for 8–12 h to allow ZnIn2S4 to grow in situ on the UiO-66-NH2 surface, forming a heterojunction structure with close interfacial contact.

[0015] 4) Washing and Separation After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting precipitate was then separated by centrifugation and washed three times each with deionized water and anhydrous ethanol to remove unreacted precursors and surface residues.

[0016] 5) Drying and grinding The washed sample was dried in a vacuum oven at 60 °C for 12 h, and then lightly ground to obtain the ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst.

[0017] By adjusting the amount of UiO-66-NH2 added, ZnIn2S4 / UiO-66-NH2 composite photocatalysts with mass fractions of 20%, 30%, 40%, 60%, and 80% can be prepared, among which 40% exhibits preferred photocatalytic performance.

[0018] This invention provides an application of a ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst in the photocatalytic reduction of carbon dioxide (CO2). The specific application method involves dispersing the catalyst in a reaction system containing a sacrificial agent under visible light irradiation, introducing CO2 gas to carry out the reduction reaction, and then quantitatively analyzing the reaction products using high-performance liquid chromatography after the reaction is complete. The visible light source is a xenon lamp or an LED visible light source, with a main wavelength range of 400–500 nm, an optical power of 100–500 W, and an illuminance of 50–150 mW·cm⁻²; the amount of catalyst used is 10–50 mg. The reaction system has a solution volume of 50–150 mL, and CO2 is introduced for 10–60 min before the reaction to reach saturation; The sacrificial agent is one or more of triethanolamine, methanol or isopropanol, with a volume fraction of 10%–30%; The reaction time is 2–8 h; The reaction temperature is 20–40 ℃; The reduction products include carbon monoxide and formic acid.

[0019] This invention has the following significant features: 1) In-situ construction of heterogeneous structures In-situ growth of ZnIn2S4 on the UiO-66-NH2 surface can be achieved through a one-step solvothermal method, resulting in tight interfacial bonding. The preparation method is simple, reproducible, and suitable for large-scale preparation.

[0020] 2) Promote carrier separation and migration An effective bandgap matching structure is formed between ZnIn2S4 and UiO-66-NH2, constructing a heterojunction interface electric field, which significantly promotes the separation and directional migration of photogenerated electron-hole pairs and improves electron utilization efficiency.

[0021] 3) Enhances CO2 adsorption and activation capabilities UiO-66-NH2 has a high specific surface area and abundant pore structure, which is conducive to the adsorption and activation of CO2 molecules and enhances the concentration at the reaction interface. 4) Improved reducing activity and selectivity It achieves high CO2 conversion and target product selectivity under visible light conditions. Under optimal ratio conditions, the CO2 conversion is significantly improved, and the yields of CO and / or HCOOH are significantly better than those of single ZnIn2S4 or UiO-66-NH2 materials, demonstrating excellent catalytic activity and selectivity, while also exhibiting good cycle stability, showing promising application prospects. Attached Figure Description

[0022] Figure 1 X-ray diffraction (XRD) patterns of composite photocatalysts with different proportions of ZnIn2S4 / UiO-66-NH2.

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the ZnIn2S4 / UiO-66-NH2 heterojunction composite catalyst.

[0024] Figure 3 This is a transmission electron microscope (TEM) image of the ZnIn2S4 / UiO-66-NH2 heterojunction catalyst.

[0025] Figure 4 The UV-Vis DRS spectra of ZnIn2S4 / UiO-66-NH2 composite photocatalysts with different proportions are shown.

[0026] Figure 5 This is a high-resolution spectrum of the S 2p orbital in the X-ray photoelectron spectroscopy (XPS) of the catalyst before and after recombination.

[0027] Figure 6A comparison of the performance of ZnIn2S4 / UiO-66-NH2 composite catalysts with different UiO-66-NH2 addition ratios in the photocatalytic reduction of CO2.

[0028] Figure 7 This is a schematic diagram of the band structure and possible charge transfer mechanism of the ZnIn2S4 / UiO-66-NH2 heterojunction. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Experimental methods, reagents, and equipment not specifically described in the embodiments are all based on conventional conditions in the art or commercial products. Example

[0030] Preparation of ZnIn2S4 catalyst Weigh 1.5 mmol ZnCl2, 1.5 mmol InCl3, and 6 mmol thioacetamide, add them to 60 mL of deionized water, and stir magnetically for 30 min at room temperature to form a homogeneous solution. Transfer the resulting solution to a 100 mL polytetrafluoroethylene-lined reactor and react at 160 °C for 10 h. After naturally cooling to room temperature, collect the product by centrifugation and wash three times each with deionized water and anhydrous ethanol. Dry the sample in a vacuum oven at 60 °C for 12 h, and grind it to obtain ZnIn2S4 powder catalyst. Example

[0031] Preparation of 40% UiO-66-NH2 / ZnIn2S4 composite catalyst 1.5 mmol ZnCl2, 1.5 mmol InCl3, and 6 mmol thioacetamide were weighed and dissolved in 60 mL of deionized water. UiO-66-NH2 powder (40% of the final composite material mass) was separately weighed and ultrasonically dispersed in the above solution for 10 min. After stirring at room temperature for 30 min, the mixture was transferred to a reactor and reacted at 160 ℃ for 10 h to allow ZnIn2S4 to grow in situ on the UiO-66-NH2 surface. The product was centrifuged, washed, vacuum dried at 60 ℃, and then ground to obtain a 40% UiO-66-NH2 / ZnIn2S4 heterojunction composite catalyst, named ZIS / NU-4. Example

[0032] Preparation of composite catalysts with different UiO-66-NH2 ratios Based on Example 2, ZnIn2S4 / UiO-66-NH2 composite catalysts with mass fractions of 20%, 40%, 60%, and 80% were prepared by adjusting the amount of UiO-66-NH2 added. The remaining preparation steps were the same as in Example 2, and they were named ZIS / NU-2, ZIS / NU-4, ZIS / NU-6, and ZIS / NU-8, respectively. Example

[0033] Application of ZnIn2S4 / UiO-66-NH2 composite catalyst in photocatalytic reduction of CO2 The ZIS / NU-4 heterojunction composite catalyst prepared in Example 2 was used to test its photocatalytic reduction performance of CO2. The specific procedure is as follows: 20 mg of catalyst was weighed and dispersed in 100 mL of a mixed solution (80 mL of deionized water and 20 mL of triethanolamine, 20% by volume, as a sacrificial agent). After ultrasonic dispersion for 5 min, the solution was transferred to a 200 mL sealed quartz photocatalytic reactor. Before the reaction, high-purity CO2 (99.999%) gas was introduced for 30 min to remove air from the system and ensure the solution reached CO2 saturation. The reaction system was then sealed under a continuous CO2 atmosphere.

[0034] A 300 W xenon lamp was used as the light source, equipped with a 420 nm cutoff filter to ensure visible light illumination. The light intensity, measured by an optical power meter, was 100 mW·cm⁻². The distance between the light source and the reaction liquid surface was approximately 10 cm. During the reaction, a circulating cooling water system was used to maintain the system temperature at 5 ± 2 ℃, and the system was kept uniformly dispersed under magnetic stirring (400 rpm). The reaction time was set to 4 h, and a certain volume of gas sample was extracted every 1 h for analysis.

[0035] After the reaction, gas phase products were quantitatively analyzed using gas chromatography (GC-TCD / FID) to detect the generated carbon monoxide (CO) and a small amount of methane (CH4); liquid phase products were detected by ion chromatography, with formic acid (HCOOH) being the main product. The results showed that under the above conditions, the CO generation rate of the ZIS / NU-4 heterojunction composite catalyst reached 19.6 μmol·g⁻¹·h⁻¹, and the HCOOH generation rate was 439.4 μmol·g⁻¹·h⁻¹, significantly better than that of single ZnIn₂S₄ or UiO-66-NH₂ materials.

[0036] Experimental results show that by constructing a tight heterojunction interface between ZnIn2S4 and UiO-66-NH2, the separation and migration of photogenerated electron-hole pairs can be effectively promoted, the utilization efficiency of electrons participating in the CO2 reduction reaction can be improved, and thus the photocatalytic reduction activity and product selectivity of CO2 can be significantly enhanced.

[0037] Catalytic performance data:

[0038] The results showed that the ZnIn2S4 / UiO-66-NH2 composite catalysts all exhibited better catalytic performance than ZnIn2S4 alone, with the composite catalyst containing 40% UiO-66-NH2 showing the best overall performance. Example

[0039] Catalyst stability test The ZIS / NU-4 composite catalyst from Example 2 was used in a cyclic experiment. Each reaction lasted 4 hours. After the reaction, the catalyst was recovered by centrifugation, washed with deionized water, dried, and reused.

[0040] The results showed that the catalytic activity decreased only slightly after 5 cycles, maintaining about 94% of the initial activity, demonstrating good structural stability and reusability.

[0041]

[0042] Comparative Example Comparative Example 1: After reacting for 4 h without a catalyst, no CO or HCOOH was detected.

[0043] Comparative Example 2: The reaction was carried out under dark conditions, and no reduction products were detected.

Claims

1. The application of a ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst in the catalytic reduction of carbon dioxide; wherein the ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst is formed by introducing UiO-66-NH2 during the formation of ZnIn2S4, so that ZnIn2S4 is grown in situ on the surface of UiO-66-NH2, forming a heterojunction structure with close interfacial contact, wherein the mass fraction of UiO-66-NH2 is 20%–80%.

2. The application according to claim 1, characterized in that... The mass fraction of UiO-66-NH2 is 30%–50%; preferably 40%.

3. The application according to claim 1, characterized in that... The ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst is prepared by introducing UiO-66-NH2 during the preparation of ZnIn2S4. The specific steps are as follows: 1) Weigh 1.5 mmol ZnCl2, 1.5 mmol InCl3 and 6 mmol thioacetamide according to the stoichiometric ratio, and dissolve them in 60 mL of deionized water or water-alcohol mixture; 2) Add a certain proportion of UiO-66-NH2 powder, making it account for 20%–80% of the final composite material mass, and magnetically stir for 30 min or ultrasonically disperse for 10 min at room temperature to make it uniformly dispersed. 3) The resulting mixed solution was transferred to a polytetrafluoroethylene-lined reactor and reacted at 120–180 °C for 6–12 h to allow ZnIn2S4 to grow in situ on the UiO-66-NH2 surface and form a heterojunction structure. 4) After the reaction is complete, allow the mixture to cool naturally to room temperature, and wash the product with deionized water and anhydrous ethanol 2–4 times in sequence. 5) The washed sample was dried under vacuum at 50–80 °C for 8–24 h and then ground to obtain the ZnIn2S4 / UiO-66-NH2 heterojunction composite photocatalyst.

4. The application according to claim 1, characterized in that... The ZnIn2S4 has a sheet-like structure and is uniformly loaded on the surface of the UiO-66-NH2 porous framework or the outer wall of the pores.

5. The application according to claim 1, characterized in that... The specific application method is as follows: under visible light irradiation, the catalyst is dispersed in a reaction system containing a sacrificial agent and CO2 gas is introduced to carry out a reduction reaction. After the reaction is completed, the reaction products are quantitatively analyzed by high performance liquid chromatography. The visible light source is a xenon lamp or an LED visible light source, with a main wavelength range of 400–500 nm, an optical power of 100–500 W, and an illuminance of 50–150 mW·cm⁻²; the amount of catalyst used is 10–50 mg. The reaction system has a solution volume of 50–150 mL, and CO2 is introduced for 10–60 min before the reaction to reach saturation; The sacrificial agent is one or more of triethanolamine, methanol or isopropanol, with a volume fraction of 10%–30%; the reaction time is 2–8 h; and the reaction temperature is 20–40 °C. The reduction products include carbon monoxide and formic acid.

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