Two-dimensional conducting MOF electrode activates molecular oxygen to generate singlet oxygen for non-free radical dominated water purification

Advanced oxide process (AOPs) mediated by singlet oxygen (¹O₂), an excited oxygen molecule, is considered as a promising decontamination method because of its high energy, electrophilicity and well anti-interference ability. In this paper, we propose a strategy to construct two-dimensional conducting MOFs (metal organic frameworks) growth on carbon fiber electrode (Cu-HHTP@CF) with excellent electrocatalysis ability of O₂ activation under low voltage conditions to generate ¹O₂ for highly efficient non-free radical dominated water purification. The atomic Cu site in planar CuO₄ node in the Cu-HHTP catalyst can convert oxygen to produce a large number of reaction intermediates superoxide radical (·O₂^–), and ultimately to ¹O₂, which were verified by electron paramagnetic resonance (EPR) and reactive oxygen species (ROS) quenching experiments. As a result, the designed Cu-HHTP@CF exhibited excellent electrocatalytic ability to degrade p-nitrophenol (PNP) under different aqueous environmental conditions, and achieve ∼ 99 % ultra-fast removal efficiency within 20 min. The degradation path of PNP by ¹O₂ was proposed by density functional theory (DFT) calculation and product analysis. In addition, various ROS produced by oxygen activation can cooperatively catalyze the degradation of pollutants and more effectively water purification. This study provides a guidance for generating ¹O₂ from molecular oxygen by electrocatalysis in water treatment processes.