Ligating atom modulated metal-oxygen bonds for electrocatalytic water oxidation

Applying a positive potential to break the metal-oxygen (M-O) bonds in the electrocatalysts is essential for generating active sites that boost oxygen evolution reaction (OER). However, precisely modulating the M-O binding energy in traditional transition metal oxides remains an insurmountable challenge due to their robust ionic bonds and inflexible lattices. Here we demonstrate that spatially arranged ligating atoms—structural motifs that coordinate the metal center—can serve as key regulators of M-O bonds. Using terephthalate-derived polydentate ligands, we construct metal-organic frameworks (MOFs), in which heterogeneous ligand fields systematically re-engineer the electronic landscape of cobalt in Co-O linkages. Combined theoretical prediction and experimental evidence establish a monotonic correlation between OER activity and the field strength of ligating atoms, following the order of amino-Co-MOF > hydroxy-Co-MOF > thio-Co-MOF. Specifically, the N-ligating atoms in amino-Co-MOF facilitate the dynamic evolution of Co centers from an octahedral Co(II) initial state to a planar Co(III) active state during electrocatalysis by selectively weakening Co-O interactions. Consequently, amino-Co-MOF achieves an ultrahigh activity of 3 A cm-2 at 1.75 V, as well as exceptional stability at 1 A cm-2 over 2,100 hours with a decay rate of only 0.012 mV/h, in the anion exchange membrane water electrolyzer, surpassing 2026 DOE performance targets.