Alkyl modified cationic COFs for preferential trapping of charge dispersed perrhenate: Synergistic hydrophobicity and anion-recognition effects

Yingzhong Huo; Ruoxuan Guo; Chaofeng Zhao; Xinjie Ma; Tao Wen; Yuejie Ai

doi:10.1016/j.scitotenv.2023.169000

Alkyl modified cationic COFs for preferential trapping of charge dispersed perrhenate: Synergistic hydrophobicity and anion-recognition effects

Sci Total Environ. 2024 Feb 20:912:169000. doi: 10.1016/j.scitotenv.2023.169000. Epub 2023 Nov 29.

Authors

Yingzhong Huo¹, Ruoxuan Guo¹, Chaofeng Zhao¹, Xinjie Ma¹, Tao Wen¹, Yuejie Ai²

Affiliations

¹ MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, PR China.
² MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, PR China. Electronic address: aiyuejie@ncepu.edu.cn.

PMID: 38040349
DOI: 10.1016/j.scitotenv.2023.169000

Abstract

Charge dispersed oxoanionic pollutants (such as TcO₄^- and ReO₄^-) with low hydrophilicity are typically difficult to be preferentially extracted. Recently, cationic covalent organic frameworks (COFs) have received considerable attention for anions trapping. Two cationic COFs, denoted as Tp-S and Tp-D, were synthesized by incorporating ethyl and cyclic alkylated diquats into 2,2'-bipyridine-based COF. A synergistic effect of hydrophobic channel and anion-recognition sites were achieved by branched chains, which effectively surmounted the Hofmeister bias. Both Tp-S and Tp-D exhibited raising removal performance for surrogate ReO₄^- at high acidity with adsorption capacities of 435.6 and 291.4 mg g^-1, respectively. Obvious variations caused by side chains were displayed in microstructures and adsorption performance. Specially, compared with Tp-D, Tp-S demonstrated desirable priority in uptake capacity and selectivity. In a real-scenario experiment, Tp-S could remove 72.8 % of ReO₄^- in a simulated Hanford LAW stream, which was attributed to the spatial effects and charge distribution arising from the open and flexible side chains of Tp-S. Otherwise, the rigid cyclic chains endowed pyridine-base Tp-D material an unprecedented alkaline stability. Spectra and theoretical calculations revealed a mechanism of preferential capture based on electrostatic interaction and hydrogen bonding between charge dispersed ReO₄^-/TcO₄^- and Tp-S/Tp-D. This work provides an innovative perspective to tailored materials for the treatment of oxoanionic contaminants.

Keywords: (99)TcO(4)(−)/ReO(4)(−); Density functional theory; Ion exchange; Pyridine; Side chain effect.