Dithia-Crown-Ether Integrated Self-Exfoliated Polymeric Covalent Organic Nanosheets for Selective Sensing and Removal of Mercury

Abstract

Divalent mercury (Hg2+) is highly toxic in nature and extensively found in different natural water bodies worldwide. Thus, rapid trace-level monitoring of Hg2+, as well as its effective removal from contaminated natural water resources, is a key ongoing concern for sustainable public health and environmental protection purposes. To address this challenging task, herein we adopted a strategy of combining the inherent benefits of fascinating porous covalent organic frameworks (COFs) and macrocyclic chemistry via judicious design and synthesis of monomers to create a dual functional polymeric platform for simultaneous ultra-trace-level detection and effective removal of Hg2+ from aqueous solution. While doing so, a bottom-up self-assembly approach was adopted under solvothermal conditions to prepare a beta-ketoenamine linked two-dimensional self-exfoliated luminescent covalent organic nanosheet (CON), a derivative of COFs, using a rationally designed and synthesized aromatic diamine (Mc-L1) building block grafted with a pendent naptho-1,4-dithia-15-crown-5 (Mc) macrocyclic receptor acting as a highly specific Hg2+ binding unit. The as-synthesized robust Mc-CON selectively and efficiently detected ppb levels of Hg2+ together with high capacity removal capability (605 mg/g) from contaminated aqueous solution under a wide range of pH (3-9) with excellent recyclability, making Mc-CON a potential candidate for realistic open-air applications.