Boosting Cascade Electron Transfer for Highly Efficient CO₂ Photoreduction

Artificial photosynthesis converting carbon dioxide into chemical fuels with a high added value is a promising solution to both fossil fuel shortage/pollution and global climate change; however, the development of highly efficient photocatalysts toward this goal is still largely bereft of fresh ideas. Herein, we propose a “cascade electron transfer” strategy through spurring both interfacial and inner electron transfer rates for a 0D/2D photocatalyst of CsPbBr₃/CuTCPP metal organic framework (MOF). Upon photoexcitation, the heterojunction structure with an appropriate band alignment facilitates an ultrafast interfacial electron transfer rate of 1.4 ps from CsPbBr₃ segment to CuTCPP MOF and subsequent ultrafast internal electron transfer of 21 ps from CuTCPP ligand to the Cu node within the enlarged 2D framework. The efficient electron transfer ensures efficient charge separation favorable for photocatalytic reactions: The photocatalyst exhibits an outstanding yield of 47.2 μmol g⁻¹ h⁻¹ (CO and CH₄ combined) superior to previous reports. Rational design of hierarchical heterojunctions with matching electronic bandgap not only expedites cascade charge transfer but also prevents holes from recombining with electrons or oxidizing the photocatalysts without the necessity of sacrificial reagents. This work thus provides useful insight for boosting photocatalytic efficacy from a dynamic perspective.