Cascaded Energy Transfer in Supramolecular Assemblies Enables Amplified and Photoswitchable Circularly Polarized Luminescence

Photoresponsive circularly polarized luminescence (CPL) materials are promising for optical information processing and anti‐counterfeiting. However, integrating high luminescence dissymmetry factor ( g lum ) with high‐contrast reversible switching within a single system remains a significant challenge. In this study, we present a supramolecular CPL nanoplatform that combines hierarchical chirality amplification with light‐gated cascaded Förster resonance energy transfer (FRET). Selective host–guest recognition between a TPE‐functionalized chiral pillar[5]arene ( TPEP5 ) and a polymeric guest forms emissive supramolecular polymers with amplified chirality. Confined co‐assembly with the achiral relay dye 4,7‐di(2‐thienyl)‐benzo[2,1,3]thiadiazole (DBT) enables efficient FRET from TPEP5 to DBT, accompanied by concomitant chirality transfer, generating red‐shifted CPL with enhanced | g lum | values of 10 − 2 . Eventually, diarylethene (DAE) is incorporated as a final photoresponsive “gatekeeper”: UV irradiation induces DAE ring closure, activating FRET pathway and quenching CPL; subsequent visible‐light irradiation reverses the process, fully restoring emission and CPL activity. This orthogonal design preserves the structural integrity of the chiral scaffold over repeated switching cycles, achieving robust, fatigue‐resistant, and architecture‐preserving CPL on/off control. Therefore, our strategy provides a generalizable blueprint for intelligent chiral photonic materials with built‐in security functionality.