MOF-derived hierarchical hollow ZnO nanocages with enhanced low-concentration VOCs gas-sensing performance

•Hierarchical hollow ZnO nanocages were constructed using self-sacrificial Zn-MOFs.•The ZnO nanocages show significantly enhanced chemical sensing sensitivity towards ppb or sub-ppm level acetone and benzene, respectively, and good selectivity towards acetone.•The enhanced sensing performance is ascribed to the well-developed porosity and abundant surface oxygen vacancies, facilitating the diffusion and surface reaction of oxygen and analyte molecules. The design and synthesis of nanostructured ZnO with high chemical sensing properties, especially towards ppb or sub-ppm level VOC gases is still highly desired and challengeable. Herein, the hierarchical hollow ZnO nanocages were synthesized by a facile strategy through the simple and direct pyrolysis of Zn-based metal-organic framework. The as-synthesized hollow ZnO products present the typical hierarchical structures with hollow interiors enveloped by interpenetrated ZnO nanoparticles as porous shell, providing structurally combined meso-/macro-porous channels for facilitating the diffusion and surface reaction of gas molecules. The gas-sensing experiments demonstrate that, in contrast with singular ZnO nanoparticles, the ZnO nanocages show significantly enhanced chemical sensing sensitivity and selectivity towards low-concentration volatile organic compounds, typically, acetone and benzene. Furthermore, the ZnO hollow nanocages perform sub-ppm level sensitivity with 2.3ppm−1 towards 0.1ppm benzene, and ppb level sensitivity with 15.3ppm−1 towards 50ppb acetone, respectively. The enhanced sensing performance of the MOF-derived ZnO nanocages is ascribed to the unique hierarchical structure with high specific surface area and abundant exposed active sites with surface-adsorbed oxygen.