Coupling Self-Sensitized CO₂ Photoreduction of Silicon(IV)-Terpyridine Complexes with Organic Synthesis

Furthermore, the direct utilization of CO₂ reduction products in organic synthesis is a promising strategy for the valorization of CO₂. Herein, we report the first use of main-group silicon(IV) coordination complexes as self-sensitized molecular photocatalysts for the near-unity-selective reduction of CO₂ to CO without requiring an external photosensitizer.

Under visible-light irradiation, these Si(IV) complexes are photoexcited and can be reductively quenched by 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH). Mechanistic studies reveal five ligand-based reduction processes for Si(IV) complexes, with CO₂ reduction occurring at a five-electron-reduced state of the ligand. The self-sensitized process was further elucidated by theoretical calculations, spectroelectrochemical analysis, emission quenching experiments, controlled-potential electrolysis, and in situ DRIFTS measurements.