Organometallic Iridium(III) Complex Sensitized Ternary Hybrid Photocatalyst for CO2 to CO Conversion

Abstract A series of heteroleptic iridium(III) complexes functionalized with two phosphonic acid (−PO 3 H 2 ) groups ( dfppy IrP , ppy IrP , btp IrP , and piq IrP ) were prepared and anchored onto rhenium(I) catalyst (ReP)‐loaded TiO 2 particles (TiO 2 /ReP) to build up a new IrP ‐sensitized TiO 2 photocatalyst system ( IrP /TiO 2 /ReP). The photosensitizing behavior of the IrP series was examined within the IrP /TiO 2 /ReP platform for the photocatalytic conversion of CO 2 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 2 /ReP) mixed systems. Among the four IrP /TiO 2 /ReP photocatalysts, the low‐energy‐light (>500 nm) activated piq IrP immobilized ternary system ( piq IrP /TiO 2 /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 btp IrP /TiO 2 and TiO 2 ‐free btp 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 2 ‐based photolysis.