Effective visible-light driven CO ₂ photoreduction via a promising bifunctional iridium coordination polymer

A promising coordination polymer photocatalyst (Y[Ir(ppy)2(dcbpy)]2[OH]) (Ir-CP, ppy = 2-phenylpyridine, dcbpy = 2,2′-bipyridine-4,4′-dicarboxylate) based on a highly efficient light-harvesting Ir unit, Ir(ppy)2(Hdcbpy), has been obtained, with good stability and exhibiting visible-light absorption over a broad range, arising from the metal-to-ligand charge transfer (3MLCT) and ligand-to-ligand charge transfer (LLCT). The designed Ir-CP heterogeneous photocatalyst acts as both a photosensitizer to harvest visible light, and an active catalyst for CO2 photoreduction. Due to the broad absorption in the UV-visible region and long-lived excited states of Ir-CP, the photocatalyst can efficiently catalyze CO2 reduction under visible-light irradiation in a heterogeneous photocatalytic system. For the first time, the remarkable photocatalytic efficiency of Ir-CP under visible-light irradiation (38 μmol HCOO− was produced in 6 h) was shown. Moreover, Ir-CP shows high photostability during CO2 photoreduction, which promotes the recyclability of the heterogeneous photocatalyst.