To develop an efficient heterogeneous Fenton catalyst over a wide pH range without any external energy input is still a challenging work. In this study, the Fenton activity of mesoporous iron oxide was firstly extended to pH of 3.6-10.0 by the carbon quantum dots (CQDs) and Cu modification (CQDs/Cu-MIO). The characterization studies indicated that CQDs/Cu-MIO had a typical mesoporous structure and CQDs was highly dispersed on the surface of catalyst. While Cu element with Cu (I) and Cu (II) was introduced in the framework of iron oxide by chemical binding of Fe-O-Cu. Without the aids of UV, CQDs/CuMIO exhibited an excellent efficiency and the ofloxacin (OFX) degradation followed the pseudo-first order kinetic model with a reaction constant of 0.1109 min(-1). Moreover, the catalyst can be reused for 6 times with good stability, in which the maximum concentration of leaching Fe and Cu ions were 0.085 and 0.015 mmol/L. The optimum reaction condition was evaluated and the degradation process of OFX was further investigated by FT-IR spectrum. The reactive oxygen species involved in OFX degradation, the effects of mesoporous structure, Cu/Fe multivalent state and the excellent capability of electron transformation/energy exchange of CQDs on the enhancement of CQDs/Cu-MIO Fenton activity were also discussed. Finally, the heterogeneous Fenton reaction mechanism was proposed based on the experimental results. (C) 2017 Elsevier B.V. All rights reserved.