Fig. 1. Rhenium bipyridyl photocatalysts for CO₂ reduction to CO and COOH^–. (A) The photocatalytic cycle starts with absorption of near-UV light, producing a metastable (∼60 ns) ³MLCT state that is reduced by electron transfer from an amine sacrificial donor. A solvent (or co-solvent) molecule substitutes the chloride and then dissociates leaving a radical, which subsequently binds CO₂ as a carboxylic acid. Further downstream steps lead to final production of CO or COOH^–. (B) Force-field optimized cluster of Re(bpy)(CO)₃Cl with five TEOA molecules, showing the donor–acceptor distance of roughly 5 Å.