Our study on room-temperature phosphorescence control via water encapsulation and structural dynamics in a flexible hydrogen-bonded organic framework has been published in Journal of the American Chemical Society.

In collaboration work with Distinguished Prof. Susumu Kitagawa (iCeMS, Kyoto University), we have demonstrated that the encapsulation of water molecules in a flexible hydrogen-bonded organic framework (FHOF) can induce and regulate room-temperature phosphorescence (RTP) in concert with a structural phase transition. This work has been published in Journal of the American Chemical Society.

In this study, reversible switching between a closed-pore phase and an open-pore phase was achieved through the adsorption and desorption of water molecules. The accompanying structural dynamics were found to modulate intersystem crossing and triplet nonradiative deactivation pathways, resulting in an unconventional “RTP turn-on” behavior upon water uptake—opposite to the water-induced quenching often observed in phosphorescent systems.

Time-resolved photoluminescence spectroscopy further revealed that the RTP originates from radiative decay of the guest triplet state and that long-lived triplet excitons are generated via triplet–triplet energy transfer (TTET) from the host framework to the guest molecules.  In our lab, the time-resolved emission measurements were primarily carried out by Assistant Prof. Ogawa, Mr. Honda(D2), and Mr. Segawa(D1), and played a key role in elucidating the RTP mechanism in this system.

“Correlating Room-Temperature Phosphorescence with Structural Dynamics by Water Accommodation in a Flexible Hydrogen-Bonded Organic Framework“
Qiuyi Huang, Ziqian Xue, Kaito Segawa, Teruyuki Honda, Tomohiro Ogawa, Cheng Luo, Huangjun Deng, Zhenguo Chi, Takao Fujikawa, Kiyoshi Miyata, Ken Onda, Satoshi Horike, Ken-ichi Otake, and Susumu Kitagawa
J. Am. Chem. Soc. 147,46234-46242 (2025).