Ti-O-Cr bond-mediated TiO2@MIL-101 heterojunctions for improved photocatalytic CO2 reduction

Carbon dioxide conversion represents a highly promising carbon reduction strategy, and photocatalytic conversion technology, characterized by greenness, non-toxicity, and sustainability, holds significant importance. However, enhancing CO 2 adsorption on photocatalysts and improving charge carrier separation efficiency remain substantial challenges. In this study, based on MIL-101, we designed a highly interconnected TiO 2 @MIL-101 bifunctional heterojunction by in-situ compositing TiO 2 on its surface through Ti-O-Cr bonding, aiming to achieve in-situ adsorption and conversion of carbon dioxide. This composite photocatalyst exhibits enhanced photocatalytic activity, with an average CO production rate of 35.39 μmol h −1  g −1 and a CH 4 production rate of 13.81 μmol h −1  g −1 . Compared to unmodified MIL-101 (Cr), these values are increased by 1.25-fold and 2.8-fold, respectively. Experimental results combined with DFT calculations demonstrate that the porous structure and high specific surface area of MIL-101 facilitate the diffusion of CO 2 on the photocatalyst surface and improve interfacial reaction kinetics. The synergistic effect between Ti-O-Cr bonds and the built-in electric field within the highly interconnected heterojunction accelerates the directional transfer of charge carriers at the heterointerfaces, effectively promoting the catalytic conversion of carbon dioxide.