Ligand engineering enhances Co-MOF/GF anode electrochemical degradation of atrazine

Atrazine (ATZ), a persistent chlorinated triazine herbicide, poses significant risks to aquatic ecosystems due to its high chemical stability and endocrine-disrupting properties. Although electrochemical oxidation (EO) has shown promise for pesticide removal, the rational design of anodes capable of selectively regulating reactive oxygen species (ROS) generation remains a critical challenge. This study uses ligand engineering with different carboxylic acid ligands to construct a series of cobalt-based metal-organic framework (Co-MOF) anodes on graphite felt (GF), achieving systematic regulation of the Co coordination environment and electrocatalytic behavior. Among them, the Co-MOF/GF anode based on 4,4'-biphenyldicarboxylic acid (BDA) exhibited superior ATZ degradation performance, achieving 95.2% removal within 60 min, which was approximately 1.3 times higher than that of bare GF. Mechanistic investigations combining quenching experiments and electron paramagnetic resonance (EPR) analysis demonstrated that singlet oxygen (¹O₂), rather than hydroxyl radicals, dominated the EO process. A synergistic pathway involving cathodic superoxide (•O₂^-) generation and anodic Co-MOF-mediated ¹O₂ formation was proposed. 19 ATZ degradation intermediates were identified by LC-MS, and the corresponding pathways revealed that selective dechlorination and dealkylation governed by ¹O₂ effectively reduced molecular toxicity, as further supported by ECOSAR predictions and luminescent bacteria inhibition rate. The Co-BDA/GF anode exhibited excellent operational stability over ten consecutive cycles and maintained high degradation efficiencies toward structurally diverse pesticides and antibiotics, demonstrating its versatility. This work provides new insights into ligand-engineered MOF anodes for selective ¹O₂-dominated electrochemical oxidation and offers a promising strategy for the efficient and environmentally benign remediation of triazine-based pesticides.