Direct CO2 photoreduction from flue gas by synergistic catalysis of a nickel metal-organic framework and a ruthenium polypyridyl complex

Direct photoreduction of CO2 from flue gas is an energy-saving avenue to realize the carbon-neutral cycle but it is still in its infancy. Herein, we constructed a new anionic metal-organic framework based on trinuclear Ni clusters and thiophenecarboxylic acid for CO2 photoreduction of exhaust gas from a power plant. Under visible-light irradiation, the yield of CO was 17.4-26.3 mmol g(-1) in diluted CO2 with a concentration of 5-20%. The apparent quantum yield (A.Q.Y.) under a 10% CO2 atmosphere was determined to be 2.1%, which ranks among the highest values of the reported photocatalysts under similar conditions. Importantly, in real flue gas containing 10% CO2, a selectivity of 90.4% was achieved and CO generation reached 18.2 mmol g(-1). In situ transient photovoltage (TPV) and density functional theory (DFT) calculations showed that the formation of a CO2 bridged photocatalytic interface between Ni-MOF1 and a Ru complex ([Ru(bpy)(3)]Cl-2/[Ru(bpy)(2)]Cl-2) was a crucial factor for the efficient CO2-to-CO conversion in diluted CO2.