Defect-Driven Stepwise Activation of Metal–Organic Frameworks Toward Industrial-Level Anion Exchange Membrane Water Electrolysis

Abstract

Metal-organic frameworks (MOFs), featuring well-defined metal active sites and unique coordination environment, have recently emerged as ideal model catalysts for establishing precise structure-activity relationships in oxygen evolution reaction (OER). However, elucidating essential catalytic mechanisms responsible for dynamic reaction conditions remain challenging, primarily due to the complicated adsorption behavior and cross-step transfer of key adsorbates during OER. Herein, we propose a defect-driven stepwise activation strategy to meticulously control the adsorption behavior for defective Co-based MOF (termed D/CoFc-MOF) through tailoring the interplay between local coordination geometry and electronic configuration. Operando characterizations reveal that D/CoFc-MOF undergoes a unique stepwise activation during OER, progressing from pristine MOF state to intermediate α-FeOOH state, and ultimately to active CoFeOOH phase, which markedly differs from conventional single-step surface phase conversion. Theoretical calculations demonstrate that the electronic interaction between the active Co sites and OOH* intermediates of MOF-derived defective CoFeOOH can be effectively strengthened, thereby overcoming the high reaction barrier and enhancing OER activity. The D/CoFc-MOF anode, deployed in anion exchange membrane water electrolysis, achieves industrial-scale current densities of 1 A cm⁻² at 1.69 V and operates stably for 300 h. This approach provides a fundamental insight into designing catalysts prone to dynamic phase transitions.