Effective removal of toxic heavy metal ions from wastewater using boroxine covalent organic framework

Abstract

Elimination of toxic heavy metals from wastewater is a worldwide concern due to the severe detrimental effects that they can cause to the human life and to the surrounding environment. In this work, using density functional theory calculations and motivated by the first synthesis of a covalent organic framework based on the boronic acid (boroxine), we investigate an effective technique to remove toxic heavy metal cations (Cd2+, Hg2+, and Pb2+) from wastewater by the boroxine covalent organic framework. We proposed that the boroxine layer was an efficient material to capture the considered toxic heavy metal cations in the aqueous solution. We also found that the large HOMO-LUMO gap of the pristine boroxine can be reduced by adsorbing Cd2+, Hg2+, and Pb2+ pollutants. Furthermore, the results reveal that the cation/boroxine systems with higher electron transport rates, exhibit the higher binding energy as well as charge transfers between the cation and boroxine layer. Time-dependent density functional analysis showed “ligand to metal charge transfer” excitations for the studied complexes. In this respect, our theoretical resulta might be fruitful for experimental studies toward proposing high-efficient materials based on covalent organic framework for removing wastewater pollutants.