Abstract Innovating new Co-based materials to outperform widely-used Co3O4-based ones for eliminating recalcitrant pollutants via peroxymonosulfate (PMS) activation is dauntingly challenging. Herein we highlight for the first time that Co4N is a new-generation PMS activator, and illuminate comprehensive understanding of intrinsic activity correlated with coordination environment of Co site. The nanocomposite comprising Co4N nanoparticles immobilized on rGO, derived from a metal-organic complex, presents remarkable catalysis for 4-chlorophenol degradation via PMS activation, particularly, up to 42 times of promotion is harvested relative to Co3O4-based catalyst with similar morphology (0.682 vs 0.016 min−1). Theoretical calculations unravel that with respect to the common-used Co3O4 and Co, Co4N featuring N incorporated into interstices of Co framework has more suitable electronic structure to render optimal binding strength for PMS activation. This work points to the potential of Co-based nitrides for PMS activation, and enlightens that subtle engineering over coordination environment and architecture promises boosted catalysis.