In Situ Ozone Generated on the Surface of Water Microdroplets Mediates Selective Aromatic Oxidation

Abstract Microdroplet-mediated ozone (O₃) oxidation offers an alternative route for organic transformations compared to the commonly studied hydrogen peroxide (H₂O₂)-dominated systems. Here, we demonstrate efficient O₃ oxidation at the microdroplet interface, achieving selective conversion of naphthalene (NA) to dimethyl phthalate (DP) with 11.6% yield. When an aqueous methanol solution of NA is atomized into ~ 7.0 µm microdroplets under O₂ atmosphere, the system operates without external catalysts or oxidants while outperforming typical microdroplet oxidation methods. The generation of O₃ is unequivocally confirmed by indigo disulfonate spectrophotometry and high-resolution mass spectrometry. Combined with radical trapping experiments and DFT calculations, these results establish a surface-activated O₃-mediated oxidation mechanism. Key intermediates were further confirmed by mass spectrometry. This work not only advances microdroplet O₃ chemistry beyond analytical detection to preparative synthesis, but also provides new insights into interfacial oxidative processes.