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 (glum) 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 |glum| 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.