Synthesis of ZIF-8@TiO2 Nanoribbon Catalysts by Ultrasonication for Enhanced Photocatalytic CO2 Reduction Activity

Photocatalytic research on conventional semiconductors has been conducted for many years, but the conversion efficiency of solar energy remains low. Conventional semiconductor/metal–organic framework (MOF) hybrid photocatalysts have emerged as an alternative approach to enhance solar energy utilization due to their porous and well-defined surface structures. In this study, we present a composite nanophotocatalyst with efficient CO2 reduction capabilities driven by sunlight, referred to as ZIF-8@TiO2-NBS. This composite is prepared by externally decorating pure anatase-phase TiO2 nanoribbons with zeolitic imidazolate framework-8 (ZIF-8) through ultrasonic synthesis, with careful modulation of their ratio. The resulting composite exhibits an impressive specific surface area (optimized at 1352.31 m2/g) and maintains a stable mesoporous structure. Exceptional CH4 yield (29.53 μmol·g–1·h–1) and selectivity (71.97%) were achieved under solar irradiation. Further insights from X-ray photoelectron spectroscopy and in situ infrared tests indicate that the remarkable enhancement in the photocatalytic activity of ZIF-8@TiO2-NBS can be attributed not only to the well-designed surface structure but also to the synergistic effect between ZIF-8 and TiO2. This interaction leads to the redistribution of electron clouds and the creation of partial oxygen vacancy defects. Notably, the partnership between ZIF-8 and TiO2 notably enhances the separation of photogenerated carriers and the stability of the composite catalysts. This is evident in the increased presence of crucial reaction intermediate species (*COOH) in the ZIF-8/TiO2 composite catalysts, during both dark-adsorption and light-driven reaction phases. This study underlines the promising potential of combining MOFs with conventional semiconductor photocatalytic materials, providing theoretical insights and empirical data to further refine the selection and design of advanced photocatalysts.