Mechanistic Insights Into Iron(II) Bis(pyridyl)amine‐Bipyridine Skeleton for Selective CO2 Photoreduction

Abstract A bis(pyridyl)amine‐bipyridine‐iron(II) framework (Fe(BPAbipy)) of complexes 1 – 3 is reported to shed light on the multistep nature of CO 2 reduction. Herein, photocatalytic conversion of CO 2 to CO even at low CO 2 concentration (1 %), together with detailed mechanistic study and DFT calculations, reveal that 1 first undergoes two sequential one‐electron transfer affording an intermediate with electron density on both Fe and ligand for CO 2 binding over proton. The following 2 H + ‐assisted Fe‐CO formation is rate‐determining for selective CO 2 ‐to‐CO reduction. A pendant, proton‐shuttling α‐OH group ( 2 ) initiates PCET for predominant H 2 evolution, while an α‐OMe group ( 3 ) cancels the selectivity control for either CO or H 2 . The near‐unity selectivity of 1 and 2 enables self‐sorting syngas production at flexible CO/H 2 ratios. The unprecedented results from one kind of molecular catalyst skeleton encourage insight into the beauty of advanced multi‐electron and multi‐proton transfer processes for robust CO 2 RR by photocatalysis.