Recyclable IPN Photocatalysts Supported by Polymer Matrices: From Soluble Copolymers to Core-Polymer Brush Shell Nanostructures

: Functional polymeric materials have recently emerged as promising supports for organic photocatalysts (PCs), yet the effects of PC design and polymer architecture on catalytic performance remain underexplored. In this study, we present a versatile strategy for small-molecule activation using carbazolyl-dicyanobenzene-based PCs featuring an isophthalonitrile (IPN) core. These PCs feature thermally activated delayed fluorescence (TADF) properties and long-lived excited states, although they also suffer from an intrinsic chemical fragility that hampers their recyclability. A library of IPN derivatives was synthesized, characterized, and integrated into either soluble copolymers (by exploiting controlled radical polymerization) or grafted from inert silica nanoparticles (NPs) to yield PC-loaded spherical polymer brushes. Although soluble copolymers showed catalytic activity comparable to that of free PCs while testing model Povarov-type cycloadditions, PC recovery was only modest and relied on precipitation steps. In contrast, PC-loaded brushes on NPs achieved high yields and enabled efficient catalyst recovery and reuse (≥90%) over multiple cycles. This comparative approach highlights how the nature of the polymeric support, soluble vs. nanostructured, critically influences both catalytic performance and recyclability. More generally, the incorporation of IPN PCs into advanced polymer scaffolds is demonstrated to enhance their applicability, cost-efficiency, and sustainability.