Different types of Cu-based nanoparticles, namely Cu 2 O, Cu and CuO were homogeneously dispersed on cubic ordered mesoporous carbon CMK-8 (denoted as Cu 2 O@CMK-8, Cu@CMK-8 and CuO@CMK-8, respectively) and their performances for catalytic reduction of 4-nitrophenol (4-NP) were comparatively studied. The average particle size of Cu 2 O, Cu, and CuO nanoparticles confined in CMK-8 were estimated to be 4.0, 8.1, and 4.3 nm, respectively. In comparison to Cu@CMK-8 and CuO@CMK-8, the Cu 2 O@CMK-8 nanocomposite exhibits an outstanding rate constant of 2.21 × 10 −2 s −1 and an exceptionally high activity parameter of 203 s −1 g Cu −1 when the actual Cu loading is considered. The uniform particle size distribution along with high BET surface area and the ability to generate highly active nascent Cu(0) nanoparticles during the catalytic process activate both the 4-NP and BH 4 − to be efficiently adsorbed on the active sites of Cu 2 O@CMK-8. It is found that the catalytic properties of these Cu-based CMK-8 nanocomposites strongly depend on the state of Cu and their particle size. Furthermore, Cu 2 O@CMK-8 is highly reusable for five successive cycles without significant degradation of its activity.