Out-of-Equilibrium Supramolecular Assembly Sustained by Photocatalysis.

Some supramolecular structures persist because they are stable; others persist because they work. Here, we report a platinum(II) supramolecular system in which catalytic activity is uniquely associated with a far-from-equilibrium aggregate. The complex forms two emissive species: a kinetically trapped, orange-emissive aggregate (PtA), and a thermodynamically stable, blue-emissive aggregate (PtB). Only PtA is catalytically active, acting as a single-component photocatalyst for hydrogen evolution in aqueous ascorbate without additional photosensitizers or co-catalysts, whereas PtB is completely inactive. Continuous irradiation drives and maintains PtA in an active, out-of-equilibrium state by coupling energy input directly to photocatalytic turnover, thereby preventing its conversion into the inactive thermodynamic PtB form. Upon removal of light, PtA irreversibly relaxes to PtB, and all photocatalytic activity is lost. This system demonstrates how catalytic function can be confined to an out-of-equilibrium assembly and sustained only through ongoing energy dissipation.