Nondissociative activation of O2 for SO2 oxidation on metal-free N-doped carbocatalyst

•A nondissociative O2 activation mechanism is proposed on metal-free carbocatalyst.•The doped substrate and SO2 molecule synergistically result in O2 activation.•O dopant and CO/NO reactant doesn't maintain the same mechanism for O2 activation. Oxygen molecules (O2) are generally one of the most important and economic oxidants for a large range of chemical processes. Due to its intrinsically sluggish nature, exploring a suitable catalyst for activation has long been a challenging issue. Based on DFT calculations, we proposed a new mechanism for O2 activation, where O2 could be activated to form an adsorbed peroxide species on a metal-free carbocatalyst, rather than be dissociated to form two adsorbed O atoms as conventional. This kind of activation results in a SO2-O2 coadsorbed intermediate, which separates a high-barrier reaction into two concerted low-barrier (∼ 0.3 eV) reactions. The number of active electrons of the active C sites was proposed to be a descriptor of catalytic activity. Our results indicate a nondissociative mechanism for O2 activation on a metal-free carbocatalyst and provide new insight into SO2 catalytic oxidation at low temperature. [Display omitted] O2 can be activated without dissociation by the synergistic effect of the double graphitic-N dopant and SO2. 2N-doped carbocatalyst can divide the reaction into two low energy barriers processes with an intermediate SO2−O−O*. 1N-doped carbocatalyst proceeds this reaction with one single high energy barrier.