Bisulfate-mediated selective methane oxidation under mild aqueous conditions

The selective oxidation of methane under mild conditions remains a formidable challenge because of the inert C─H bond and the ease of over-oxidation. Here we report a facile strategy that enables methane conversion at room temperature and ambient pressure using molecular O 2 and commercially available Cu powder in dilute aqueous H 2 SO 4 . The reaction is capable of proceeding with only trace CO 2 formation, producing methyl bisulfate and methanol as the primary partial oxidation products. In situ Raman spectroscopy indicates that an in situ O 2 -derived Cu 2 O surface is the reaction-relevant phase associated with C─H bond activation. The observed selectivity arises from bisulfate adsorption on this Cu 2 O surface, which suppresses methanol over-oxidation, together with the interception of surface-generated methyl intermediates to form oxidation-resistant methyl bisulfate. This Cu/O 2 -H 2 SO 4 system demonstrates that methane can be selectively oxidized under mild aqueous conditions and provides mechanistic insight into Cu/O 2 -mediated oxidation, suggesting a bisulfate-assisted approach to suppressing over-oxidation that may be applicable to other substrates.