Phase Transition Engineering of Metal–Organic Frameworks Induces Multiphase Complexation for Enhancing the Oxygen Evolution Reaction

Phase transition engineering of metal-organic frameworks (MOFs) presents a promising strategy for enhancing electrocatalytic performance in water splitting applications. In this study, we demonstrate a controlled phase transition strategy to synthesize a multiphase composite (op&cp) composed of open phase (op) and closed phase (cp) through precise desolvation treatment. When used as an alkaline water electrocatalyst, op&cp exhibits exceptional oxygen evolution reaction (OER) performance, achieving a remarkably low overpotential of 140 mV under 10 mA cm^-2 and maintaining stable operation for over 75 h at 100 mA cm^-2. In situ Raman spectroscopy and X-ray photoelectron spectroscopy show that the catalytically active substance NiOOH is formed on the engineered phase with a lower potential (1.2 V vs RHE) than the single-phase material (1.3 V vs RHE). This work establishes phase transition engineering as a viable strategy for improving MOF-based catalysis and explores the fundamental mechanism of the dynamic evolution of active sites during the OER.