Fuente: Molecules - Revista científica (MDPI) Molecules, Vol. 30, Pages 4725: A Stable Tetraphenylethylene-Based Charge-Assisted Hydrogen-Bonded Organic Framework for Turn-On Fluorescence Sensing of Al3+ Ions
Molecules doi: 10.3390/molecules30244725
Authors:
Yingjia Deng
Yijin Wang
Xiangyu Gao
Yunke Jin
Jiabao Liu
Guanglai Mo
Yixuan Guo
Lanlu Lu
Peng Li

The development of stable and sensitive fluorescent sensors for metal ion detection remains a challenge in materials chemistry. Although hydrogen-bonded organic frameworks (HOFs) have shown great potential in luminescent applications, their practical use is often limited by structural instability. In this work, we present a novel charge-assisted HOF, termed FDU-HOF-21 ([H(NH2Bpy)]2(TPE)), constructed from a tetraphenylethylene (TPE)-based carboxylic acid ligand (H4TCPE) and 2,2′-bipyridine-5,5′-diamine (NH2Bpy). Single-crystal X-ray diffraction (SCXRD) reveals a stable three-dimensional framework stabilized by an extensive hydrogen-bonding network and reinforced by charge-assisted hydrogen bonds (CAHBs), and it exhibits exceptional stability across various solvents and pH conditions. Moreover, FDU-HOF-21 serves as a highly sensitive and selective fluorescent turn-on sensor for Al3+ ions, with a lowest limit of detection (LOD) of 1.7 × 10−6 M. Characterization and time-dependent density functional theory (TDDFT) calculations reveal that the fluorescence enhancement originates from the suppression of non-radiative decay likely due to the reduction in intermolecular charge transfer (Inter-CT) during the emission process, coupled with the restricted intramolecular rotation upon Al3+ chelation.