Using state-of-the-art density functional theory (DFT) based approach; we investigated the catalytic activity of electron doped C2N monolayer (O -> N) for CO oxidation. Large surface-to-volume ratio and uniformly distributed holes of recently synthesized planar 2D C2N have made it a potential candidate as noble metal-free catalyst. However, pristine C2N monolayer is chemically inert and hinders the adsorption of O-2 and CO molecule on it. Oxygen doping in C2N brings additional electrons to the system and introduces donor state below E-F. Thus the reactivity of O-doped C2N (2OC(2)N) monolayer gets significantly enhanced, thereby opening up the possibility of its usage as a catalyst. This reactive 2OC(2)N surface adsorbs an incoming O-2 molecule along with the elongation of O-O bond, making it chemically active. Presence of this pre-adsorbed active O-2 greatly impedes the adsorption of another incoming CO, favoring Eiley-Rideal (ER) mechanism for CO oxidation. (C) 2017 Elsevier B.V. All rights reserved.