Single‐Atom Iron‐Catalyzed Oxidative Esterification: From Methylarenes to the Upcycling of Polystyrene and Lignin‐Derived Feedstocks

ABSTRACT The catalytic oxidation of C─H bonds represents a transformative strategy for converting abundant hydrocarbons into high‐value functional molecules. We report a sustainable heterogeneous methodology for the oxidative esterification of methyl (hetero)arenes and the oxidative C─C bond cleavage of alkyl arenes to synthesize aromatic methyl esters using molecular oxygen in water. This process is driven by an atomically dispersed iron catalyst supported on N‐doped porous carbon (Fe‐SAC), featuring well‐defined Fe‐N 4 active sites. The catalyst exhibits exceptional activity and selectivity, effectively overcoming the intrinsic inertness of C(sp 3 )─H and C─C bonds without the need for noble metals or hazardous additives. Mechanistic investigations, combining kinetic studies, in situ DRIFTS, and DFT simulations, identify superoxide radicals (O 2 ●− ) as key reactive species and pinpoint benzylic C─H bond cleavage as the rate‐determining step. Beyond small molecules, the Fe‐SAC system demonstrates high efficiency in the valorization of lignin derivatives and the chemical upcycling of polystyrene waste into value‐added esters. Its remarkable stability, ease of recycling, and use of an eco‐friendly solvent/oxidant system make this iron‐catalyzed process a cost‐effective and green alternative to traditional esterification methods.