Beyond Molecular Design: Cocrystallization in Hydrogen‐Bonded Organic Frameworks for Energy‐Conserving Dehydration and Real‐Time Luminescent Humidity Detection
Wen‐Zhu Sun, Weijie Zhang, Xu Jing, Dan‐Qing Liu, Bei‐Qi Ou, Ling Chen, Jia‐Wen Ye, Xiao‐Ming Chen
Abstract
ABSTRACT Luminescent probes attract increasing attentions for the unique superiorities like visually real‐time detecting. However, for optical humidity sensing, it is still quite challenging to attain facile dehydration/activation in sensing materials, due to the high polarity of water molecules, which limits their applications in real‐time detection and energy‐conserving applications. Here, we report two fluorescent hydrogen‐bonded organic frameworks (HOFs), HPISF‐H 2 O and TPISF . HPISF‐H 2 O achieves water absorption in low humidity, but needs an energy‐intensive step (heating to ∼92°C in air) to dehydrate. Conversely, despite only a hydroxyl group being replaced, TPISF cannot bind to H 2 O at all. In other words, real‐time detection is not readily achieved through straightforward molecular design. Therefore, we propose a cocrystallization strategy to adjust their water‐binding capacity. As a result, the HOF cocrystals are adjusted to have both good H 2 O absorptivity and very gentle desorbing operation without heating (dry gas blowing or vacuuming). Benefiting from this strategy, appreciable advantages for an effective humidity sensor are realized, including real‐time detection (second‐scale response/recovery) and distinguishing fluorescence variation. Efficient sensing across a broad relative humidity (RH) range (10.0%–80.0%) was further achieved. Moreover, the mechanistic insight of fluorescent sensing was ascertained through detailed analyses of structural transformation, spectroscopic data, and theoretical approach.