Electrocatalytic Dechlorination of Dichloromethane in Water Using a Heterogenized Molecular Copper Complex

Abstract

The remediation of organohalides from water is a challenging process in environment protection and water treatment. Herein, we report a molecular copper(I) complex with two triazole units, CuT2, in a heterogeneous aqueous system that is capable of dechlorinating dichloromethane (CH2Cl2) to afford hydrocarbons (methane, ethane, and ethylene). The catalytic performance is evaluated in water and presented high Faradaic efficiency (average 70% CH4) across a range of potentials (-1.1 to -1.6 V vs Ag/AgCl) and high activity (maximum -25.1 mA/cm2 at -1.6 V vs Ag/AgCl) with a turnover number of 2.0 × 107. The CuT2 catalyst also showed excellent stability for 14 h of constant exposure to CH2Cl2 and 10 h of CH2Cl2 exposure cycling. The control compound, a copper-free triazole unit (T1), was also investigated under the same condition and showed inferior catalytic activity, indicating the importance of the copper center. Plausible catalytic mechanisms are proposed for the formation of C1 and C2 products via radical intermediates. Computational studies provided additional insight into the reaction mechanism and the selectivity toward the CH4 formation. The findings in this study demonstrate that complex CuT2 is an efficient and stable catalyst for the dehalogenation of CH2Cl2 and could potentially be used for the exploration of the removal of halogenated species from aqueous systems.