Unlocking Vacancy-Inherited Reconstruction of Metal-Organic Frameworks toward Water Oxidation

Abstract

Abstract Elucidating the dynamic reconstruction pathways of electrocatalysts under oxygen evolution reaction (OER) conditions is essential for understanding the origin of catalytic activity, yet remains challenging. Here, using an oxygen-vacancy-rich nickel-based metal-organic framework (Vo-Ni-MOF) as a model platform, we reveal a vacancy-inherited reconstruction pathway in which Vo-Ni-MOF undergoes in situ reconstruction into vacancy-retaining nickel oxyhydroxide (Vo-NiOOH) for efficient OER. By combining multimodal operando spectroscopy with theoretical calculations, we uncover a stepwise coordination evolution of Ni centres from octahedral NiO6 to penta-coordinated NiO5 and ultimately to a high-valent, tetra-coordinated NiO4 configuration under OER conditions. The resulting oxygen-vacancy-rich Vo-NiOOH exhibits enhanced OH– affinity, which facilitates O–O bond formation and subsequent OOH* intermediate generation, thereby lowering the thermodynamic demand of the O* → OOH* rate-determining step. Meanwhile, defect-induced local electronic reorganization enhances the spin polarization of Ni centres and strengthens their spin interaction with adsorbed OOH*, providing a favorable high-spin configuration for its subsequent spin evolution toward triplet O2. Notably, Vo-NiOOH delivers 500 mA cm–2 at 306 mV with over 600 h stability, and the self-assembled anion exchange membrane water electrolyzer sustains 500 mA cm–2 at 1.70 V for 500 h. This work advances the mechanistic understanding of catalyst reconstruction under OER conditions and provides guidance for the rational design of high-performance OER catalysts.