Robust Binding between Carbon Nitride Nanosheets and a Binuclear Ruthenium(II) Complex Enabling Durable, Selective CO2 Reduction under Visible Light in Aqueous Solution

Carbon nitride nanosheets (NS-C3N4) were found to undergo robust binding with a binuclear ruthenium(II) complex (RuRu′) even in basic aqueous solution. A hybrid material consisting of NS-C3N4 (further modified with nanoparticulate Ag) and RuRu′ promoted the photocatalytic reduction of CO2 to formate in aqueous media, in conjunction with high selectivity (approximately 98 %) and a good turnover number (>2000 with respect to the loaded Ru complex). These represent the highest values yet reported for a powder-based photocatalytic system during CO2 reduction under visible light in an aqueous environment. We also assessed the desorption of RuRu′ from the Ag/C3N4 surface, a factor that can contribute to a loss of activity. It was determined that desorption is not induced by salt additives, pH changes, or photoirradiation, which partly explains the high photocatalytic performance of this material.