Application of synthesized 2,5-bis(allyloxy)terephthalohydrazide functionalized covalent organic framework material as a fluorescence probe for selective detection of mercury (II)

The mercury ion Hg2+ is a highly toxic environmental contaminant that threatens both the ecosystem and human health. As such, in recent years, significant effort has been invested in developing novel strategies for ultrasensitive detection of Hg2+. Herein, we leveraged the inherent benefits of covalent organic frameworks (COFs) to design a fluorescent COF with the ability to detect Hg2+, then synthesized a 2,5-bis(allyloxy)terephthalohydrazide functionalized COF material, called BATHz-Bt, for selective Hg2+ recognition. Unlike other methods that rely on sulfur-based ligands, BATHz-Bt is comprised of a π-conjugated framework that serves as the signal transducer; and compact, evenly distributed allyloxy groups that function as the Hg2+ acceptor. In addition to the benefits provided by a stable, COF structure, the material is also re-usable, making it reliable, cost effective, and eco-friendly. Furthermore BATHz-Bt showed good detection performance, as evidenced by its high sensitivity, good selectivity, excellent pH stability, and reusability. Moreover, X-ray photoelectron spectroscopy (XPS) confirmed the presence of a robust and selective interaction between the BATHz-Bt allyloxy groups and Hg2+. Thus, while this study demonstrates the application potential of fluorescent COFs for Hg2+ detection, more importantly, it also provides a new, simple approach to environmental monitoring using functionalized COFs.