Reversible solid-state chromatic luminescence photoswitching in a dual-emitting MOF hybrid for advanced...

The engineering of smart materials exhibiting solid-state chromatic photoluminescence (PL) switching under light stimuli remains critically imperative for next-generation anticounterfeiting technologies. Here, we present a dual-emitting metal organic framework (MOF) hybrid that exhibits light-responsive chromatic PL switching in the solid state. This hybrid is constructed by encapsulating spiropyran dye molecules within a robust, luminescent zirconium-based MOF host, PCN-128 W. The host features a highly porous structure with large open channels, which facilitate dye encapsulation and provide the necessary conformational freedom for spiropyran photoisomerization. The host-guest confinement not only ensures close proximity for efficient intermolecular coupling, but also significantly enhances the dye's PL efficiency by suppressing the nonradiative decay pathways that exist in solid aggregates. Leveraging efficient host-guest Förster resonance energy transfer (FRET), the resulting hybrid exhibits weak blue emission (481 nm) from the MOF and strong red emission (634 nm) from the dye. Upon visible light irradiation, spiropyran undergoes photoisomerization from its open-ring (MC) to closed-ring (SP) form, leading to a rapid PL color switch from red to blue. This transition is driven by enhanced host emission coupled with quenched dye emission due to FRET deactivation. The PL color change is fully reversible, with dark treatment triggering spiropyran's return to the MC form and FRET reactivation. Time-resolved PL measurements confirm the dynamic modulation of FRET via dye isomerization. Motivated by these results, we designed and fabricated anticounterfeiting patterns using a high-security triple-layered information encryption strategy, demonstrating the promising potential of this hybrid in advanced information anticounterfeiting.