Supramolecular Metal‐Organic Framework Electrocatalysts With Hydration‐Adaptive Gallery Expansion and Linker‐Mediated Distal Ni‐Co Cooperation Enable Framework‐Retentive Oxygen Evolution

ABSTRACT

Atomic‑level tailoring of electronic communication between spatially separated metal sites offers a route to accelerate multielectron electrocatalysis. We report Ni‐TPTC, Co‐TPTC, and heterobimetallic Ni‐Co‐TPTC supramolecular metal‐organic frameworks (SMOFs) for the oxygen evolution reaction (OER) built from a terphenyl‑tetracarboxylate (TPTC) linker. Single‐crystal X‐ray diffraction of heterobimetallic Ni–Co–TPTC reveals trans‐bis‐aqua octahedral chains assembled into a π‐stacked, hydrogen‐bonded lattice and confirms retention of the parent architecture, while powder X‐ray diffraction supports an isostructural Co analog. In 1.0 M KOH, Ni‐Co‐TPTC reaches 20 mA cm ⁻² at 350 mV and maintains operation at ∼60 mA cm ⁻² for 45 h with modest decay of the initial current. Time‑dependent ex situ diffraction shows dominant framework reflections with low‑angle shifts consistent with gallery dilation (d‑spacing ∼7.7 → ∼9.2 Å) during early operation, while Co K‑edge X‑ray absorption and microscopy reveal Co‑rich oxide/oxyhydroxide‑like domains at longer times that correlate with decay. X‑ray photoelectron spectroscopy, quantified by the Remote Binding‑Energy Differential, tracks composition‑dependent Ni‐Co polarization, and DFT free‑energy analysis suggests that a model Ni‐Co environment lowers the Co‑centered potential‑limiting step by ∼0.24 eV relative to the Co‑only framework. These results suggest that framework‑retentive expansion and distal Ni‐Co coupling can drive OER activity before gradual deligation and oxide formation mark longer‑time degradation.