Organometallic Iridium(III) Complex Sensitized Ternary Hybrid Photocatalyst for CO 2 to CO Conversion

A series of heteroleptic iridium(III) complexes functionalized with two phosphonic acid (-PO H ) groups ( IrP, IrP, IrP, and IrP) were prepared and anchored onto rhenium(I) catalyst (ReP)-loaded TiO particles (TiO /ReP) to build up a new IrP-sensitized TiO photocatalyst system (IrP/TiO /ReP). The photosensitizing behavior of the IrP series was examined within the IrP/TiO /ReP platform for the photocatalytic conversion of CO into CO. The four IrP-based ternary hybrids showed increased conversion activity and durability than that of the corresponding homo- (IrP+ReP) and heterogeneous (IrP+TiO /ReP) mixed systems. Among the four IrP/TiO /ReP photocatalysts, the low-energy-light (>500 nm) activated IrP immobilized ternary system ( IrP/TiO /ReP) exhibited the most durable conversion activity, giving a turnover number of ≥730 for 170 h. A similar kinetic feature observed through time-resolved photoluminescence measurements of both IrP/TiO and TiO -free IrP films suggests that the net electron flow in the ternary hybrid proceeds dominantly through a reductive quenching mechanism, unlike the oxidative quenching route of typical dye/TiO -based photolysis.