Defect-Driven Accelerated Reconstruction of Metal-Organic Frameworks Toward High-Performance Anion Exchange Membrane...

Metal-organic frameworks (MOFs) with tunable coordination environments provide model platforms for elucidating electrocatalytic structure-activity relationships. However, the development of highly efficient MOF-based oxygen evolution reaction (OER) catalysts has been hindered by the limited synthetic control over framework defects and their associated reconstruction pathways. Herein, we report a defect-engineering strategy where a bicarboxylate ferrocene ligand (Fc) and a monocarboxylate linker (benzoic acid, BA) are co-assembled on nickel foam to construct a defect-rich NiFcBA-MOF featuring abundant coordinatively unsaturated Ni sites. Compared to the defect-free NiFc-MOF, NiFcBA-MOF exhibits markedly accelerated electrochemical activation, undergoing rapid in situ transformation into highly active oxyhydroxide species under OER conditions. As a result, NiFcBA-MOF requires only 270 mV of overpotential to reach a current density of 100 mA cm^-2 in 1 M KOH, outperforming the NiFc-MOF (290 mV). When employed as the anode in an anion-exchange membrane water electrolyzer, NiFcBA-MOF delivers a current density of 1 A cm^-2 at 1.85 V and maintains stable operation for 100 h at 100 mA cm^-2. This work demonstrates that rational defect engineering in MOFs can tailor reconstruction kinetics toward highly active oxyhydroxides, offering a viable route to MOF-derived OER catalysts for technologically relevant electrolyzer systems.