Upgrading N2 and O2 into valuable C–N–O chemicals

Abstract Directly using abundant air as nitrogen and oxygen source for the co-construction of C–N and N–O bonds under mild conditions is highly significant for establishing a sustainable route of synthesizing high-value C–N–O chemicals. However, the efficient and controllable activation of N2, O2, and carbon source for the selective C–N and N–O coupling in a one-step process remains a formidable challenge. Herein, we report a plasma–ultrasound catalytic process that enables direct selective conversion of air and phenol to nitroaromatic chemicals (nitrosophenol and nitrophenol) under mild conditions, delivering an overall yield of 8.1% with a high selectivity of 92.5% using a CeO2 catalyst. Mechanistic investigations reveal a crucial effect of air plasma in generating reactive oxygen and NOx species and triggering the subsequent phenol oxidization and nitration reactions in the solution. Coupling ultrasound and CeO2 catalyst in the liquid phase further promotes the formation of reactive species and targeted nitroaromatic products combined with the enhancement of both mass transfer and reaction kinetics by the ultrasonic cavitation effect.