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. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)