N -Heterocyclic Carbene Gold Complexes in a Photocatalytic CO 2 Reduction Reaction.

Molecular catalysts that are durable and highly selective in the photocatalytic CO 2 reduction reaction (PCO 2 RR) are in high demand. Molecular gold complexes are underexplored in the CO 2 RR manifold despite heterogeneous gold-CO 2 reduction catalyst counterparts being frequently studied. In this report, a series of N -heterocyclic carbene (NHC)-ligated Au complexes are evaluated in the PCO 2 RR with an added photosensitizer (tris(2-phenylpyridine)iridium, Ir(ppy) 3 ). The complexes were each studied with and without an added activator used to open a coordination site on the Au complexes. Results show an example of an exceptionally durable PCO 2 RR catalyst lasting >100 h with high product selectivity for CO. Heterogeneity tests reveal no evidence of a nonhomogeneous active catalyst, and structure-activity relationships of the molecular complexes are discussed.