Ultrafast degradation of refractory organic pollutants via PMS activation over Co3CuAl-LDH with coordinatively unsaturated Co-Cu dual active sites: Enhanced electron transfer mechanism

Peroxymonosulfate (PMS)-based advanced oxidation process is a promising technology for water treatment. However, there is still a great challenge on enhancing the PMS activation for the rapid removal of recalcitrant organic pollutants in complex waters. Herein, we developed an ultra-thin ternary CoCuAl-layered double hydroxide (LDH) catalyst with abundant oxygen vacancy (O_v), enabling the exposure of coordinatively unsaturated Co-Cu dual-metal active sites, which mediates “two birds with one stone” strategy to realize simultaneous PMS oxidation and reduction for ROS generation, achieving ultrafast elimination of refractory organic pollutants. Theoretical and experimental results reveal that the synergistic effect of Co-Cu paired sites accelerates redox cycles of Co²⁺/Co³⁺ and Cu⁺/Cu²⁺, strengthening PMS activation. Notably, the presence of O_v fine-tunes the electronic structure of adjacent Co/Cu sites, which enhances electron transfer between these unsaturated metal sites and PMS, enabling self-regeneration of metal sites, thereby synergistically promoting the productions of radicals (SO₄•⁻) and nonradicals (¹O₂). Consequently, the catalyst exhibits remarkable catalytic activity (13.27 min⁻¹) using sulfamethoxazole (SMX) as the probe, significantly surpassing those of state-of-the-art heterogeneous catalysts by approximately 15–393 times. The removal efficiency of SMX is still reached 100 % after 10 h of continuous operation in a scale-up experiment using a self-designed Fenton-like filter, and 84 % of chemical oxygen demand from real coal chemical wastewater (235 mg·L⁻¹) is removed under the same operating conditions, marking the alluring potential in advanced treatment of actual wastewater. This work provides valuable insights into electron transfer-enhanced PMS activation by LDH and elaborates its prospects in water treatment applications.