Metal‐Free Photocatalytic CO ₂ Reduction to Formate Driven by Visible Light via a Consecutive Photoinduced Electron Transfer Mechanism

Abstract

ABSTRACT Realizing efficient and selective photocatalytic CO 2 reduction (PCO 2 R) using metal‐free organic systems under visible light remains a significant challenge. Here, we report the first metal‐free, self‐sensitized molecular photocatalyst capable of driving visible‐light‐induced CO 2 ‐to‐HCOO − conversion via a consecutive photoinduced electron transfer (ConPET) mechanism. The rationally designed BPI‐OMe, featuring an electron‐donating group, demonstrates exceptional performance under visible light irradiation, achieving a formate production rate of 27.51 mmol g −1  h −1 with > 99% selectivity. This outstanding activity stems from its optimized electronic properties: a low excitation energy (2.98 eV), a long‐lived charge‐separated anion radical state ( τ = 806.94 ns), a high‐energy SOMO level (−3.47 eV), and strong CO 2 binding affinity (−0.147 eV). In situ ESR and ultrafast spectroscopic analyses reveal the ConPET process: sequential photon absorption enables electron transfer from ascorbic acid to BPI‐OMe, generating BPI‐OMe, followed by electron delivery to CO 2 to form CO 2 − , which is subsequently converted to formate through a hydrogen atom transfer. This work not only represents a breakthrough in metal‐free PCO2R but also provides a general molecular design strategy based on multi‐photon charge accumulation for enabling challenging solar‐to‐chemical transformations.