Cocatalyst-free Photocatalytic Hydrogen Evolution with Simple Heteroleptic Iridium(III) Complexes

A simple heteroleptic iridium(III) photosensitizer, Ir-1, containing two ligands S-(trifluoromethyl)-2-phenylpyridine ((C) over capN-CF3) and bipyridine ((N) over capN) has for the first time been studied for cocatalyst-free photocatalytic hydrogen evolution (PHE). The complex Ir-1 produces a hydrogen production rate (eta H-2) of 3.2 mmol g(-1) h(-1), which is over 3.6-fold higher than that of the control complex Ir-2 (0.9 mmol g(-1) h(-1)) containing bipyridine and 2-phenylpyridine ligands without CF3 groups. The higher eta H-2 of Ir-1 could be ascribed to the high light-harvesting property, longer triplet electron lifetime, and more appropriate driving force for accepting electrons from the sacrificial donor, which enable efficient charge separation and transfer of electrons for hydrogen evolution. Additionally, the photostability issues of Ir-1 and Ir-2 are addressed by the selection of suitable organic solvent/water photocatalytic systems.

Automated summary

The iridium complex Ir-1 shows significantly enhanced photocatalytic hydrogen evolution efficiency compared to the control complex Ir-2, attributed to its high light-harvesting property, longer triplet electron lifetime, and appropriate driving force for electron transfer. The selection of suitable organic solvent/water photocatalytic systems addresses the photostability issues of Ir-1 and Ir-2.