Developing high-performance catalysts suitable for a wide pH range in catalytic ozonation system remains a significant challenge, primarily owing to the limitations imposed by metal species and the pH at the point of zero charge. In this study, an O doped g-C₃N₄/CuO (CNO-CuO) catalyst was synthesized via a facile method. Compared to pristine g-C₃N₄/CuO (CN-CuO), CNO-CuO dramatically enhanced the degradation efficiency of pollutants from 25% to 100% in acidic solutions. Moreover, it exhibited the efficient degradation efficiencies across a broad pH range (3–10), demonstrating that introduction of O atoms considerably improved the universality of CNO-CuO. Experimental and theoretical studies revealed that the synergistic interaction between CuO and C–O bonds was responsible for the remarkable catalytic ozonation activity over a wide pH range. Crucially, the incorporation of O atoms contributed to reversible formation of Cu⁺, ensuring the continuous regeneration of active sites and the sustained formation of ·OH. Additionally, the C–O bond acted as a potential catalytic active site, further enhancing treatment efficiency as pH increased. This work provided a feasible strategy for broadening catalyst applicability in catalytic ozonation systems through heteroatom doping.