An emerging enol-based 1D covalent organic framework for trace water detection

The determination of trace water in organic solvents has been a long-standing research hotspot and is still evolving which requires further development. Ratiometric luminescent sensors with rapid response and accurate visualization of water assay based on porous materials are obviously prospective candidates for trace water detection, but remain a challenge. Herein, we firstly reported a novel one-dimensional (1D) covalent organic framework (COF, labeled as FZU-68) which was built from 2-hydroxyisophthalaldehyde (DIPh) and 1,3,6,8-tetra(p-aminophenyl)-pyrene (PyTTA). The COF displays comparative high specific surface area, narrow pore size distribution and prominent chemical/thermal stability. Besides, its solid state displays a bright red emission at 606 nm. More impressively, due to a water-induced enol-keto isomerization in its structure, the fluorescence of FZU-68 quenched in response to trace amounts of water, which sustain the limit of detection (LOD) in acetonitrile (MeCN) up to 0.05% (v/v). Besides, FZU-68 could be utilized several times in the above trace water detection experiments. This study not only presents the feasibility of integrating heteroatoms and functional groups into 1D COFs, but also sheds light on the application prospects of COFs in the field of chemical sensing.