Iron Oxidation State Governs the H 2 O 2 Activation Rate to Promote Direct Methane Oxidation to C1 Liquid Oxygenates

ABSTRACT The direct oxidation of methane to C1 liquid oxygenates under mild conditions has long been constrained by the inertness of C─H bonds and the high susceptibility of target products to over‐oxidation to CO 2 , making it difficult to achieve both high yield and high selectivity. Here, we prepared Fe/C, Fe 3 O 4 /C, and Fe 2 O 3 /C nanocatalysts with comparable morphologies from a common Fe 3 O 4 precursor, aiming to isolate the effect of iron oxidation state on the over‐oxidation route. Among them, Fe 2 O 3 /C, possessing optimal six‐coordinated Fe‐O structures, delivered a total yield of 0.51 mol·g cat −1 ·h −1 for C1 liquid oxygenates with nearly 100% selectivity. This performance is 5.77 and 2.11 times higher than that of Fe/C and Fe 3 O 4 /C, respectively, and remains stable over ten successive cycles. Mechanistic studies, including kinetic analyses, EPR spin trapping, and in situ DRIFTS, reveal that the Fe─O coordination dictates the partitioning of H 2 O 2 activation pathways. Fe 2 O 3 /C sustains moderate H 2 O 2 decomposition, directing it toward surface‐bound •OH and •OOH species that drive sequential C─H activation and stepwise oxygenation. In contrast, Fe/C and Fe 3 O 4 /C favor rapid O 2 evolution, which consumes these surface radicals and suppresses the radical‐mediated oxidation route. These findings provide an experimental foundation for designing efficient methane oxidation catalysts through Fe─O coordination tuning.