Polyhydroxy-Decorated 2D Covalent Organic Framework with Imine Active Sites toward Efficient Electrocatalytic Oxygen...

The development of metal-free electrocatalysts for the oxygen reduction reaction (ORR) is crucial for next-generation energy technologies, offering cost reduction, improved stability, and independence from scarce noble metals. Covalent organic frameworks (COFs) have emerged as promising candidates due to their tunable porosity, high surface area, and structural versatility. In this study, we report a hydroxyl-functionalized enamine- and imine-linked two-dimensional (2D) COFs (TFPh_DHPh_COF) as an efficient ORR electrocatalyst in alkaline media. The enamine (─C─NH─) linkages enhance structural integrity through hydrogen-bonding interaction, whereas imine (─C═N─) linkages contribute to electron density modulation, stabilizing key intermediates and facilitating a favorable four-electron ORR pathway. Natural bond orbital (NBO) analysis from computational study, reveals a partial positive charge (C^δ⁺ = 0.12) at the active site, promoting O₂ activation via end on binding and weakening the O═O bond (Pauling model). Electrochemical evaluation demonstrates a 0.72 V vs reversible hydrogen electrode (RHE) half-wave potential and exceptional durability, outperforming many metal-free catalysts under basic media. This study underscores the potential of functionalized COFs as a scalable and sustainable alternative to metal-based catalysts for fuel cells and metal-air batteries.