Covalent organic framework with bidentate ligand sites as reliable fluorescent sensor for Cu2+

Selective and sensitive detection of heavy metal ions is a theme of increasing scientific interest, great technological importance and extensive public concern. To realize this target, design of high-efficient and fluorescent materials as sensor is crucial yet challenging task. In this work, we describes the synthesis and functions of a new hydroxyl and imine groups functionalized covalent organic framework (COFs). The synthesized COFs-DT integrates multi-functionality such as extended π-conjugation framework, tunable functionality, regular pore structure, specific sites to interact with targets as well as robust chemical and thermal stability. COFs-DT shows strong and stable fluorescence when dispersed in isopropanol. The fluorescent property together with the unique bidentate ligand sites enables COFs-DT in the construction of a high-performance fluorescent sensor for detection of Cu2+ with high sensitivity and selectivity. Furthermore, we use a series of characterizations to investigate the fluorescence quenching mechanism and found the quenching through a photoinduced electron transfer mechanism with COFs-DT as donor and Cu2+ as acceptor. Our strategy not only highlights opportunities for utilizing COFs with integrated multiple unique nature as new type of fluorescent materials, but also expends the encapsulation scope of COFs for ion sensor in environmental field.