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

Abstract

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]Cl₂/[Ru(bpy)₂]Cl₂) was a crucial factor for the efficient CO₂-to-CO conversion in diluted CO₂.