Dual Activation and C–N Coupling of CO 2 and N 2 Mediated by Small Fe n + Clusters

Abstract We present a combined experimental and theoretical study on how small iron clusters activate dinitrogen (N2) and carbon dioxide (CO2) under ambient conditions. Mass spectrometry shows these clusters can cleave the N≡N triple bond, producing a range of odd-nitrogen species, with Fe3N7+ and Fe4N7+ appearing as major products. Introducing CO2 into the downstream flow-tube reactor yields distinct FenNmCO+ and FenNmO+ species, indicating that the CO2 also undergoes C═O bond dissociation under this condition. Thermodynamics and kinetics analyses reveal that the formation of Fe3,4N5CO+ proceeds via C–N coupling pathways and generates a stable N2O molecule. The empty d orbitals of Fe atoms facilitate the coordination of N2 and CO2; meanwhile, not only Fen+ but also the Fe3,4N7+ clusters exhibit delocalized electrons and superatomic states. This allows the half-filled superatomic P orbital to engage in superatom–atom bonding with carbon and oxygen atoms, thereby modifying the covalent coordination and active sites for reactions with N2 and CO2. These findings advance mechanistic insight into nitrogen fixation by iron clusters─highlighting the role of electron delocalization─and point to a promising route of plasma-assisted catalytic conversion of atmospheric CO2 and N2 into value-added products under mild conditions.