Post-synthetic thiol modification of covalent organic frameworks for mercury(II) removal from water

Wei Wang; Minjuan Gong; Donghai Zhu; Mohammadtaghi Vakili; Zahra Gholami; Huanhuan Jiang; Shuangxi Zhou; Han Qu

doi:10.1016/j.ese.2023.100236

Post-synthetic thiol modification of covalent organic frameworks for mercury(II) removal from water

Environ Sci Ecotechnol. 2023 Jan 7:14:100236. doi: 10.1016/j.ese.2023.100236. eCollection 2023 Apr.

Authors

Wei Wang¹, Minjuan Gong¹, Donghai Zhu¹, Mohammadtaghi Vakili², Zahra Gholami², Huanhuan Jiang¹, Shuangxi Zhou¹, Han Qu³

Affiliations

¹ State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xi'ning, Qinghai Province, 810016, China.
² ORLEN UniCRE, a.s, Revoluční 1521/84, 400 01, Ústí nad Labem, Czech Republic.
³ Key Laboratory of the Three Gorges Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing, 400044, China.

Abstract

Various materials have been developed for environmental remediation of mercury ion pollution. Among these materials, covalent organic frameworks (COFs) can efficiently adsorb Hg(II) from water. Herein, two thiol-modified COFs (COF-S-SH and COF-OH-SH) were prepared, through the reaction between 2,5-divinylterephthalaldehyde and 1,3,5-tris-(4-aminophenyl)benzene, followed by post-synthetic modification using bis(2-mercaptoethyl) sulfide and dithiothreitol, respectively. The modified COFs showed excellent Hg(II) adsorption abilities with maximum adsorption capacities of 586.3 and 535.5 mg g^-1 for COF-S-SH and COF-OH-SH, respectively. The prepared materials showed excellent selective absorbability for Hg(II) against multiple cationic metals in water. Unexpectedly, the experimental data showed that both co-existing toxic anionic diclofenac sodium (DCF) and Hg(II) performed positive effect for capturing another pollutant by these two modified COFs. Thus, a synergistic adsorption mechanism between Hg(II) and DCF on COFs was proposed. Moreover, density functional theory calculations revealed that synergistic adsorption occurred between Hg(II) and DCF, which resulted in a significant reduction in the adsorption system's energy. This work highlights a new direction for application of COFs to simultaneous removal of heavy metals and co-existing organic pollutants from water.

Keywords: Covalent organic frameworks; Density functional theory calculation; Hg(II); Post-modification; Synergistic adsorption mechanism.