A Broad Range of Aromatic Carboxylic Acids for Photocatalytic Methane Oxidation

Photocatalytic methane (CH₄) activation under mild conditions presents a sustainable strategy for converting methane into valuable chemicals. This study introduces a versatile class of conjugated aromatic carboxylic acids as efficient, metal-free photocatalysts for CH₄ oxidation in sodium chloride-trifluoroacetic acid (NaCl-TFA) media. Spectroscopic analysis and machine learning using spectroscopic features further elucidate key structural and electronic factors influencing catalytic activity, offering predictive insights for designing high-performance photocatalysts. The carboxyl group is important in generating electron-deficient carboxyl (RC(═O)O•) or carboperoxyl radicals (RC(═O)OO•), enabling selective hydrogen atom transfer (HAT) for CH₄ functionalization. Mechanistic investigations indicate the role of acyl chloride intermediates in enhancing reactivity. This work highlights the potential of aromatic carboxylic acids to address the challenges of methane functionalization, paving the way for greener chemical transformations and the utilization of inert feedstocks in sustainable chemistry.