Harnessing Photons for Trifold Output: Chromic, Luminescent, and Mechanical Transformations in a Smart Material

By leveraging the dual photochemical activity of vinylpyridinium building blocks, the concurrent [2+2] photocycloaddition and photoinduced electron transfer are integrated within coordination polymer frameworks to achieve triple photoresponses, simultaneously generating photochromism, fluorescence modulation, and photomechanical actuation within a single crystalline system. The efficient photocycloaddition occurs in the interpenetrated framework despite the criss-crossed olefin arrangement, resulting in rapid stress accumulation and release that manifests as explosive photosalient behavior alongside optical switching. The framework-dependent ligand conformations produce distinct fluorescence readouts, allowing the progress of the cycloaddition to be monitored optically. When embedded in poly(vinyl alcohol) matrices, the crystal-level micro-strain is amplified into programmable macroscopic motions including straightening, crawling, and gathering under single-wavelength irradiation. This work provides a design strategy for integrating multiple photoresponses into a single material, contributing to programmable light-driven actuators and adaptive devices.