Synthesis of Multilevel Structured MoS2@Cu/Cu2O@C Visible-Light-Driven Photocatalyst Derived from MOF–Guest Polyhedra for Cyclohexane Oxidation

Selective oxidation of cyclohexane to KA oil (cyclohexanol and cyclohexanone) is one of the most important industrial procedure. In this study, we reported a remarkably enhanced cyclohexane oxidation under visible-light irradiation by a novel MoS2@Cu/Cu2O@C composite photocatalyst with multilevel hierarchy, which was prepared by immersing (NH4)2MoS4 guest into Cu-metal–organic framework (MOF) polyhedra host and subsequently pyrolyzing the Cu-MOF–guest polyhedra to encapsulate MoS2 into Cu/Cu2O@C. Importantly, the composite photocatalyst showed much better photocatalytic cyclohexane oxidation performance than that of the simple mechanical mixture of MoS2 and Cu/Cu2O@C. The distinct photocatalytic performance of MoS2@Cu/Cu2O@C composite can be ascribed to its heterojunction band reconstruction and unique multilevel architecture to facilitate the separation of photoinduced electrons and holes and generation reactive species during photoirradiation. The Cu nanoparticles in the MoS2@Cu/Cu2O@C composite also effectively capture electrons and prevent electron–hole recombination due to the surface plasmon resonance (SPR). The photogenerated holes (h+) and ·OH radical were supposed to be predominant components of the valence band (VB) and oxidize cyclohexane (C6H12) to produce cyclohexyl radical (C6H11·), which can be further oxidized to cyclohexanol and cyclohexanone. According to the above results, a possible photocatalytic mechanism was proposed.