• CH 4 oxidation by H 2 O 2 undcr the presence of CO to oxygenates is investigated. • 46.8 mmol·g cat −1 ·h −1 can be acquired with 90.7 % selectivity of oxygenates over all products. • Atomically Rh species anchored on zeolites are identified as active sites. • CO promotes the generation of reaction radicals (·CH 3 and ·OH). The direct conversion of methane into valuable chemicals under mild conditions represents a promising technological pathway, yet achieving both high efficiency and selectivity remains a major challenge in catalysis. In this work, we report a rhodium catalyst atomically dispersed on ZSM-5 for catalytic conversion of methane to oxygenates using H 2 O 2 as oxidant under mild conditions. With carbon monoxide (CO) as a promoter, the catalyst achieved an oxygenates productivity of 46.8 mmol·g cat −1 ·h −1 (equivalent to 9360 mmol·g Rh −1 ·h −1 or 964.1 mol·mol Rh −1 ·h −1 ) with approximately 90.7 % overall selectivity (including liquid products and gaseous CO 2 ). The catalyst retained high activity over five recycling experiments. A combined investigation by HAADF-STEM, XAFS, and DRIFTS-CO analyses confirms that the active sites consist of atomically dispersed Rh species in a Rh 1 O 5 configuration anchored within the ZSM-5 micropores. Mechanistic studies, including controlled experiments, EPR, and in situ infrared spectroscopy, reveal that CO plays a dual role. It promotes the formation of ·OH radicals from H 2 O 2 and facilitates the activation of methane, leading to the generation of ·CH 3 species. Oxygenate products are produced via the direct coupling of ·CH 3 , ·OH, and CO molecules. This work highlights the potential of tailoring atomically dispersed metal catalysts and using CO as reactant and promoter to enable efficient methane transformation into valuable oxygenates.
Liu et al. (Mon,) studied this question.