Detection and Removal of Mercury Ions in Water by\na Covalent Organic Framework Rich in Sulfur and Nitrogen

Abstract

Hg/Hg­(II)\nis deemed to be the most toxic heavy metal to humans.\nTherefore, designing suitable adsorbents to simultaneously achieve\nhigh capacity, rapid mercury adsorption, and fluorescence detection\nis still an important challenge in overcoming Hg²⁺ pollution.\nHere, we report a flexible alkylamine covalent organic framework (TpTSC),\nwhich has been used as an efficient adsorbent and achieves the dual-functional\napplication of TpTSC for Hg²⁺, with a fluorescence detection\nlimit of 2 ppm and simultaneously a removal capacity of 1035 mg g^–1. It can remove 10 ppm mercury solution to below 2\nppb (drinking water standard) within 10 min, and the removal rate\nis as high as 99.98%. To a certain extent, it exceeds the recently\nreported thioether or thiol functionalized adsorbents. The kinetic\nstudy shows that TpTSC displays a very high <i>K</i>_d value, with <i>K</i>_d = 1.2 × 10⁹ mL g^–1, which has a strong affinity for\nmercury. In addition, TpTSC displays a good recycling capacity, with\na removal rate of over 90% after five cycles. In conclusion, sulfur\nmodification is a useful strategy for developing dual-functional COFs\nto simultaneously remove and detect toxic heavy metal ions.