Correlating Room-Temperature Phosphorescence with Structural Dynamics by Water Accommodation in a Flexible Hydrogen-Bonded Organic Framework

Organic room-temperature phosphorescence (RTP) materials have garnered significant interest in various crucial applications. While RTP emissions typically exhibit a water-induced quenching propensity, the impact of genuine water accommodation into porous materials on RTP properties remains unclear and confusing due to the lack of structural evidence and ambiguous mechanism of water-regulated RTP properties. Herein, we demonstrate the manipulation of RTP properties through water-accommodation-induced structural dynamics in a flexible hydrogen-bonded organic framework (FHOF) system. Through water accommodation in voids, a reversible structural transformation between the closed- and open-pore phases occurs, integrated with a counterintuitive turn-on RTP feature. Comprehensive photophysical, structural, and theoretical analyses reveal that the water-promoted RTP behavior is correlated with the structural transition, which results from the water-induced effective regulations of both the intersystem crossing process and the triplet nonradiative decays. Furthermore, the water adsorption events can be converted into direct, naked-eye-visible feedback, demonstrating great potential in time-resolved information delivery and encoding applications. This work elucidates the role of water accommodation in the manipulation of RTP properties, which not only establishes the correlation between water-regulated triplet exciton behaviors and structural dynamics but also opens new opportunities for the development of future multifunctional and intelligent flexible porous materials.