Benzene hydroxylation with green oxidants such as dioxygen is a promising sustainable alternative to produce phenol, but the design of an easily available and efficient heterogeneous catalyst remains a challenge. In this work, the surface oxygen groups of commercially activated carbon were facilely modulated through post-treatment with an aqueous nitric acid solution and therefore an effective metal-free heterogeneous catalyst was obtained. This strategy led to the formation of abundant surface quinone carbonyl and phenolic hydroxyl groups, which acted as the active sites to produce hydroxyl radicals and then oxidized benzene to phenol. A satisfactory yield of 10.1% and well reusability were obtained. In addition, the formation of these surface oxygen species above to promote the activity was also observable in other modified activated carbon materials using aqueous hydrogen peroxide, sulfuric acid, or ammonium persulfate solutions and thus suggests a facile way to modulate the commercially active carbon for the establishment of an efficient metal-freesolutions and thus catalyst.