Organic linker engineering of metal–organic frameworks for enhanced oxygen evolution reaction

Abstract

The development of efficient, stable, and low-cost electrocatalysts for oxygen evolution reaction (OER) is essential for advancing alkaline water electrolysis and rechargeable metal air batteries. Metal–organic frameworks (MOFs), owing to their modular design and structural versatility, offer a unique platform for engineering catalytic materials with tailored electronic, morphological, and stability characteristics. In this study, a series of cobalt-based metal–organic frameworks (Co-MOFs) were engineered through systematic linker modification to enhance their structural, electronic, and catalytic properties. Three catalysts Co-BTC, Co-bpy-BTC, and a tuned Co-MOF were synthesized, followed by pyrolysis at 700 °C under N₂ to obtain conductive, defect-rich Co-based nanostructures. Electrochemical evaluation in both 0.1M and 1M KOH revealed that the tuned Co-MOF-700 exhibited a significantly lower onset potential (0.330 V), reduced overpotential, and faster kinetics in LSV and CV measurements. Oxygen reduction reactions (ORR) studies showed improved half-wave potential and diffusion-controlled behavior, confirming bifunctional activity. The cycling durability tests confirmed long-term operational stability, with minimal performance loss even after 10 hours of continuous operation and 500 cycles, respectively. Comprehensive physicochemical characterization supported electrochemical performance. XRD confirmed partial MOF-to-oxide/carbon conversion, while SEM and TEM revealed uniform nanoscale morphology and defect-rich carbon frameworks. EDS and XPS verified homogeneous elemental distribution, nitrogen incorporation, and the presence of mixed-valence Co species (Co²⁺/Co³⁺), which collectively facilitated improved electron transport and catalytic activity. This work highlights the effectiveness of linker engineering and pyrolysis-driven structural transformation in designing next-generation Co-MOF-derived catalysts for highly efficient and durable OER/ORR electrocatalysis