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

Abstract

Carbon nitride nanosheets (NS-C₃ N₄ ) were found to undergo robust binding with a binuclear ruthenium(II) complex (RuRu') even in basic aqueous solution. A hybrid material consisting of NS-C₃ N₄ (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/C₃ N₄ 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.