Sulfate Radical-Mediated Methane Conversion to C-C and C-S Products in Water

Abstract

The direct conversion of CH4 into value-added chemicals under benign conditions is a fundamental goal of sustainable chemistry, though it is challenged by its inherent stability. Herein, we report a catalyst-free, photochemical strategy for the simultaneous C-S and C-C bond formation from CH4 in a purely aqueous system. By leveraging sulfate radicals (SO4• -) generated from UV irridiation of K2S2O8 at ambient temperature, our method circumvents the need for corrosive acids or complex catalysts. The approach affords a valuable mixture of products, including methanesulfonic acid (CH3SO3H), methyl bisulfate (CH3SO4H), CH3COOH, and CH3COCH3, with a combined selectivity of 90%. The efficiency of this green system was demonstrated in a photochemical flow reactor, achieving 5% methane conversion at ambient pressure and temperature.Mechanistic studies reveal that CH3SO4H as a key intermediate, whose subsequent reaction with a •CH3 radical not only forms the C-S product but also co-generates a methoxy radical to initiate C-C coupling. By uniquely harnessing sulfate radical reactivity in water, this work provides a simple and effective route for methane valorization under exceptionally mild conditions.