High-valent cobalt-oxo species mediated oxidation of pollutants by ZIFs-derived single-atom cobalt-activated peroxymonosulfate

Abstract

The high-valent metal–oxo species (HVMO) has been identified as an excellent reactive oxygen species (ROS) for the selective degradation of pollutants in peroxymonosulfate (PMS)-based advanced oxidation processes. However, there are still significant challenges to achieve selective oxidation of pollutants by actively designing catalysts for targeted generation of HVMO. In this study, the cobalt single-atom catalyst (Co_SA-N/C) was synthesized through pyrolysis of a bimetallic zeolitic-imidazole frameworks (Zn/Co − ZIFs) regulated by cetyltrimethylammonium bromide. As experimental results, the high-valent cobalt-oxo species (Co(IV) = O) was identified as the main ROS instead of •OH, SO₄^•−, O₂^•−, and ¹O₂, achieving efficient degradation of sulfamethoxazole (SMX). Particularly, the competitive kinetics calculation displayed that the Co_SA-N/C achieves 91.87 % Co(IV) = O formation selectivity superior to unmodulated Co-N/CR (64.57 %), and exhibited excellent SMX degradation performance with both impressive catalytic activity (0.701 min⁻¹) and PMS consumption (58.8 %). Moreover, the Co_SA-N/C@SA highly dispersed in fixed bed volumes for a continuous-flow reactor, enabling continuous and efficient removal of SMX (> 98 % after 48 h operation). Overall, this work presents a new scheme for selective removal of pollutant by Co-N/C catalyst and Co(IV) = O during water purification.