Supramolecular Nanoassemblies Harness Radical Excited‐State Cascade Electron Transfer for Selective CO 2 Photoreduction

ABSTRACT Mimicking the efficiency of natural photosynthesis for multielectron CO 2 photoreduction remains a central challenge in solar fuel research. Toward this goal, we developed herein a noble metal free supramolecular ion‐pair assembly comprising rhodamine B ( RB ), an underexplored organic photosensitizer, and a cobalt(II) tris(2‐pyridylmethyl)amine complex ( 1Co ), which self‐assembles into core–shell nano/micro‐assembly via counterion‐mediated contact ion pairing. This confined ion pair architecture promotes counterion mediated, light‐driven hopping electron transfer, suppressing geminate recombination and enabling efficient charge migration, as demonstrated by optical spectroscopy, femtosecond–nanosecond transient absorption, electrochemical impedance spectroscopy, and 2D mass spectrometry studies. Orthogonal dual‐light excitation activates radical anion excited states (RB •−* ) within the assembly, enabling a diffusion‐independent cascade electron transfer pathway. This unique approach achieves selective CO 2 photoreduction to syngas under single‐light irradiation and switches product distribution toward methane generation under dual‐light conditions‐ a rare feat for photocatalytic CO 2 reduction systems. This work introduces a generalizable supramolecular ion‐pairing strategy for engineering spatially preorganized donor–acceptor architectures that harness high‐energy radical excited states for sustainable solar fuel generation.