Atomically Dispersed Mn Sites Promote O2 Activation for Oxidative Esterification of Furfural

The oxidative esterification of biomass-derived furfural is a sustainable pathway to value-added chemicals, yet current catalytic systems typically require harsh oxidants and alkali additives, which limit scalability and complicate downstream processing. Herein, a single-atom manganese catalyst (MnSA@CN) with atomically dispersed Mn-N4 sites is fabricated by coordinating Mn2+ with 1,4-diazabicyclo[2.2.2]octane (N(CH2CH2)3N, DABCO), followed by controlled thermal treatment and acid leaching. Under mild, additive-free conditions (90 °C, ambient-pressure air), MnSA@CN affords quantitative conversion of furfural to methyl furoate with >99% selectivity in a single step. Radical scavenging experiments combined with density functional theory calculations reveal a cooperative activation mechanism: the Mn-N4 sites synergistically activate O2 and furfural, generating methanol-derived hydroxyl radicals that mediate direct C-H oxidation and esterification, thereby bypassing the conventional furoic acid intermediate. This work highlights the pivotal role of isolated Mn-N4 centers in substrate-oxidant coactivation and delivers a scalable, noble-metal-free catalytic platform for sustainable biomass valorization, bridging fundamental single-atom catalysis with practical biorefinery transformations.