Polyelectrolyte Copolymer Nanoreactors: From Colloidal Assembly to Photoredox Activity in Water.

Performing organic photoredox reactions in water remains challenging because most catalysts cannot simultaneously solubilize substrates, control nanoscale organization, and maintain activity under aqueous conditions. We report a photoredox-active polyelectrolyte based on a polydehydroalanine (PDha) backbone covalently functionalized with polypyridyl complexes to address some of these limitations. The copolymer undergoes substrate-triggered self-assembly in water, forming photocatalytically active spherical colloidal nanostructures (∼30 nm), as confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The assemblies efficiently catalyze the hydroxylation of arylboronic acids, a representative water-insoluble photoredox transformation. Mechanistic studies using UV-visible spectroscopy, Raman spectroscopy, time-resolved emission spectroscopy, electrochemistry, and density functional theory (DFT) indicate that dual hydrogen bonding between PDha carboxylates and arylboronic acids governs both self-assembly and catalytic performance. The nanostructures retain high activity over multiple cycles. These findings establish adaptive polymer self-assembly as a general strategy for creating enzyme-like, water-compatible photoredox systems and provide a platform for transferring organic photoredox chemistry into aqueous media.