CoNi metal-organic frameworks monolayers: metal nodes-dependent photocatalytic CO2-to-CO conversion

Metal-organic frameworks (MOFs) are emerging as promising catalysts towards CO2 photoreduction for providing high-density metal nodes as catalytic active sites. However, an in-depth understanding of metal nodes effect in CO2 photoreduction is still lacking. Through constructing a set of isostructural CoNi based MOFs monolayers (MOLs), herein we unravel the intrinsic relationships between metal nodes and CO2 photoreduction performance. Ni MOLs exhibits spectacular CO selectivity of 97.8 % with a highest apparent quantum yield of 2.2 % among analogous systems, significantly higher than those of Co MOLs. Experiments in dilute CO2 further amplify the superiority of Ni MOLs. Experimental and theoretical investigation demonstrate that initial adsorption of CO2 molecules onto MOLs is the pivotal step. The strong CO2 binding affinity of Ni MOLs is beneficial to stabilize the metal-CO2 adducts and facilitate CO2-to-CO conversion. The universality of the superiority of Ni for CO2 photoreduction has been further demonstrated. This work provides fundamental guidance for the rational design of metal-organic catalysts towards solar-to-fuels conversion.