Bottom-Up Synthesis of a Novel Sulfhydryl Functionalized Cofs with Heteropore for Ultrafast Removal of Trace Hg(Ii) from Water

Abstract

Covalent organic frameworks (COFs) are crystalline porous organic polymers with large porosity, adjustable pore size, high-density chelating sites, variable functional groups and easy surface modification. The development of functionalized COFs is critical to expanding their potential for removing toxic heavy metals from drinking water. Here, a new S-rich COFs (COFDBD-BTA) with heteropore is proposed use of “bottom-up” integrated by direct amine-aldehyde dehydration condensation between 2,5-diamino-1,4-benzenedithiol dihydrochloride (DBD) and [1,1′-biphenyl]-3,3′,5,5′-tetracarbaldehyde (BTA). The COFDBD-BTA has a hexagonal kgm structure and presents a sheet-like morphology. Particularly, there are dense S atoms in COFDBD-BTA, which can provide high-density Hg(II) adsorbing sites, for efficient and selective trace Hg(II) adsorption. COFDBD-BTA exhibited a high Hg(II) removal level from water with a saturated adsorption capacity of 644.81 mg g −1. Furthermore, when trace Hg(II) is present, COFDBD-BTA exhibited excellent performance, achieving rapid removal of Hg(II) from 30 μg L-1 to 0.71 μg L-1 below the allowable limit in drinking water (1 μg L-1) endorsed by the World Health Organization (WHO) within 10 seconds. Moreover, the adsorbent also exhibited a wide low concentration applicable range (6-500 μg L-1), a simple and feasible regeneration method and great Hg(II) removal potential from the actual tap water system. The excellent adsorption efficiency, outstanding recyclability and the one-step room temperature synthesis make the S-rich COFDBD-BTA a promising candidate for the elimination of Hg(II) from drinking water.

Keywords: COFs, drinking water, Trace heavy metals, Hg(II), adsorption