Highly efficient, selective, and durable photocatalytic system for CO2 reduction to formic acid.

We discovered an extremely suitable sacrificial electron donor, 1,3-dimethyl-2-(o-hydroxyphenyl)-2,3-dihydro-1H-benzo[d]imidazole, for the selective photocatalytic reduction of CO2 to formic acid using a Ru(ii)-Ru(ii) supramolecular photocatalyst. The efficiency, durability, and rate of photocatalysis are significantly increased (ΦHCOOH = 0.46, TONHCOOH = 2766, TOFHCOOH = 44.9 min-1) in comparison with those using 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole or 1-benzyl-1,4-dihydronicotinamide.