MIL-125(Ti)@ZIF-67-derived MIL-125(Ti)@TiO2 hollow nanodiscs decorated with Co3S4 for remarkable photocatalytic CO2 reduction

Fabricating photocatalysts with customizable structure and composition using different metal–organic framework (MOF) building blocks has intriguing implications in chemistry and material science, but it is challenging to do so. Here, a two-step synthetic strategy was designed to prepare MIL-125(Ti)@TiO2 hollow nanodiscs decorated with Co3S4 nanoparticles for CO2 photoreduction. The Co-based zeolite imidazolium ester backbone (ZIF-67) nanolayer was first loaded on the prepared MIL-125(Ti) nanodiscs to form core@shell MIL-125(Ti)@ZIF-67 nanodiscs. The following sulfidation process under solvothermal condition led to the production of MIL-125(Ti)@TiO2 hollow nanodiscs decorated with Co3S4 nanoparticles (MIL-125(Ti)@TiO2\Co3S4). This ternary hybrid catalyst with hollow nanodisc structure possessed a significantly enhanced charge separation efficiency and visible light absorption, along with offering a huge number of active sites. Considering the above advantages, the CO2 photoreduction activity of the optimized MIL-125(Ti)@TiO2\Co3S4 catalyst was significantly increased when compared to single-component catalysts (MIL-125(Ti), TiO2, and Co3S4) and binary hybrid catalysts (MIL-125(Ti)@TiO2 and TiO2\Co3S4) under simulated sunlight irradiation. CO is the main product with a productivity of 587.50 μmol g−1 h−1, which is almost seven times higher than that of pure MIL-125(Ti). The potential photocatalytic mechanism of the hybrid photocatalyst has also been demonstrated. This study presents a simple and effective technique for fabricating MOF-based hybrid catalysts for photocatalytic applications.