The atomically-dispersed and high-loading Co on graphitic carbon nitrogen (Co/C₃N₄-w, w representing the molar ratio of Co to melamine in the synthesis recipe) was synthesized by coupling the one-pot strategy with the electrostatic adsorption method and used for the solvent-free aerobic oxidation of cyclohexane. The characterization results of Co/C₃N₄-w revealed that the single-atom Co with the positive charge existed in the sixfold cavities of C₃N₄ and was stabilized by the CoN interaction along with the electron transfer from Co atoms to C₃N₄. The catalytic activity of Co/C₃N₄-w presented the positive correlation with the loading of the single-atom Co, and the superior catalytic performance with 21 % conversion and 95 % overall selectivity was obtained over Co/C₃N₄-0.02, which also exhibited the excellent universality to the aerobic oxidation of other cycloalkanes and alkyl aromatics. Experiments combined with density functional theory calculations demonstrated that the favored O₂ dissociation and intermediate cyclohexylhydroperoxide decomposition on the low-coordinated single-atom Co, and the promoted adsorption of cyclohexane on the electron-rich C₃N₄ surface, synergically boosted the cyclohexane oxidation. Distinctively, the high stability of Co/C₃N₄-0.02 in the cyclohexane oxidation originated from the robust single-atom Co structures and hydrophobic C₃N₄ surface.