Direct oxidative carbonylation of methane to acetic acid via high-valent iron-oxo mediated water activation

Abstract

Abstract Direct conversion of CH 4 into value-added chemicals is impeded by the inert C-H bonds and inefficient C-C coupling. We report a spatially separated Rh-O-Fe active-site architecture that decouples CH 4 and H 2 O activation through a high-valent-metal mediated radical mechanism, enabling selective CH 3 COOH synthesis. In-situ infrared, operando Mössbauer spectroscopy, and quasi in-situ high-field EPR reveal that O 2 oxidizes Rh and Fe to high valence states. Rh (III) activates CH 4 to •CH 3 , while Fe (IV)  = O dissociates H 2 O into •OH through a truncated water-gas shift pathway. •OH rapidly reacts with CO to form •COOH intermediates, which couples with •CH 3 within the zeolite to yield CH 3 COOH. This dual-site strategy circumvents kinetic limits of conventional water-gas shift and CO insertion steps. The catalyst achieves 18.2 mmol g cat -1 h -1 CH 3 COOH with 92% selectivity and 100-hour stability in continuous operation. This study establishes radical decoupling enabled by high-valent metal sites as a design principle for selective alkane oxidation.