Tetragonal multilayered ZnO/CuO composites derived from Zn- and Cu-containing metal-organic framework: Effect of calcination temperature on physicochemical properties and photocatalytic activity

Tetragonal multilayered ZnO/CuO composites prepared by the annealing of a Zn- and Cu-containing pillar-layered metal-organic framework were characterized by using instrumental techniques and investigated as catalysts for the degradation of 4-nitrophenol (4-NP) under irradiation with UV–vis light. The as synthesized samples contained p-n junctions, amorphous-crystalline heterojunctions , which benefitted light absorption and charge separation. The calcination temperature significantly influenced both the physicochemical properties and photocatalytic activities of these composites. The sample obtained at 400 °C (TL-ZC-400) exhibited the best photocatalytic performance, achieving a 4-NP degradation efficiency of 93.93% after 40 min of illumination. The TL-ZC-400 still showed high photodegradation ability (97.2%) after four times recycling. Furthermore, the recombination of ZnO and CuO adjusted the band gap structure of TL-ZC-400. Radical trapping experiments showed that the degradation of 4-NP was mainly mediated by hydroxyl radicals and holes. A possible photocatalytic mechanism was also proposed in this study.