The sluggish kinetics of air electrodes largely limits the practical applications of metal–air batteries. At present, preparing single-atom catalysts confined in ultrathin N-doped porous carbon (NPC) with a high surface area remains a challenge. Herein, a facile strategy by complexation of biomass and metal ions combined with the gas-foaming method was used to synthesize substantial Co–N 4 active sites on ultrathin NPC with a super-high specific surface area of 1977.9 m 2 g −1 . The catalyst owns brilliant oxygen reduction reaction properties with higher half-wave potential of 0.863 V and faster kinetics process (68.3 mV dec −1 ) than those of Pt/C (0.856 V and 80.46 mV dec −1 , respectively). Remarkably, it exhibits distinguished reversibility with a high initial cycle efficiency of 60.8% and satisfactory stability when used in Zn–air batteries. Moreover, the assembled Al–air battery displays preeminent discharge performance with ultrahigh power density (494 mW cm −2 ) and energy density (2387 W h kg −1 ) at 200 mA cm −2 . This study opens a new avenue to fully utilize biomass for constructing Co single-atom catalysts for metal–air batteries.