Selective Syngas Production from Partial Oxidation of Methane with Molecular Oxygen Catalyzed by a Rh ₃ O ₂ ^– Cluster

Catalytic partial oxidation of methane (POM) is a key technology for syngas production, yet its practical deployment is severely limited by poor product selectivity due to CO overoxidation and the high operating temperatures required by conventional processes. The development of catalysts capable of selectively converting methane to syngas under mild conditions remains a critical challenge. Herein, combining mass spectrometry with density functional theory calculations, we report that the Rh 3 O 2 – cluster enables the coconversion of CH 4 and O 2 to syngas and H 2 O (CH 4 + O 2 → H 2 + H 2 O + CO). Mechanistic investigations reveal that the catalytic cycle proceeds along two consecutive elementary steps: initial methane dehydrogenation by Rh 3 O 2 – to release a H 2 molecule, followed by oxidation of Rh 3 O 2 CH 2 – with O 2 to produce H 2 O and CO and regenerate the active Rh 3 O 2 – species. Kinetic analyses confirm that the syngas and water formation pathway is kinetically dominant, which effectively offsets its relative thermodynamic disadvantage, thus rendering highly selective syngas formation with complete suppression of CO overoxidation at room temperature. This work provides molecular-level insights into the selective POM mechanism and offers valuable guidance for the rational design of high-performance catalysts for methane conversion under mild conditions.