A Synthetic Protocol for Preparation of Binary Multi-shelled Hollow Spheres and Their Enhanced Oxidation Application

Multi-shelled hollow materials (MSHMs) with multifunctional compositions and multilevel interiors have received great attention by virtue of their hierarchical hollow structures and diverse applications. In this contribution, we present a new synthetic protocol to fabricate binary MSHMs with up to quadruple shells through a rapid thermal process. The binary MSHMs contain hexagonal ZnO (the primary phase) and monoclinic CuO (the secondary phase), wherein, the ZnO phase was derived from the straightforward degradation of a coordination polymer (for example, dandelion-like amorphous ZIF-90 ( a m ZIF-90)), and the CuO phase was derived from the preloaded copper nanoparticles on a m ZIF-90 which appear to enhance the oxidative degradation of a m ZIF-90. This protocol relies on the metal nanoparticle aided degradation of a m ZIF-90 in which the catalytic reactivity of metal was found in the order of Au < Co < Pt < Cu. Therefore, calcining a m ZIF-90/Au or a m ZIF-90 alone only led to the formation of nonhollow products. The number of layers in binary CuO/ZnO could be controlled by adjusting copper loading, annealing temperature, or heating ramp rate. Furthermore, the resultant binary CuO/ZnO MSHMs exhibited pronounced catalytic activity on the advanced oxidation process (AOP) toward dye wastewater treatment. This synthetic protocol may be employed for fabrication of other binary MSHMs from the enhanced oxidative degradation of ZIFs or their analogues.