Metal-Organic Framework Templated Synthesis of Ultrasmall Catalyst Loaded ZnO/ZnCo 2 O 4 Hollow Spheres for Enhanced Gas Sensing Properties.

To achieve the rational design of nanostructures for superior gas sensors, the ultrasmall nanoparticles (NPs) loaded on ternary metal oxide (TMO) hollow spheres (HS) were synthesized by using the polystyrene (PS) sphere template and bimetallic metal-organic framework (BM-MOFs) mold. The zinc and cobalt based zeolite imidazole frameworks (BM-ZIFs) encapsulating ultrasmall Pd NPs (2-3 nm) were assembled on PS spheres at room temperature. After calcination at 450 °C, these nanoscale Pd particles were effectively infiltrated on the surface of ZnO/ZnCo2 O4 HSs. In addition, the heterojunctions of Pd-ZnO, Pd-ZnCo2 O4 , and ZnO-ZnCo2 O4 were formed on each phase. The synthesized Pd-ZnO/ZnCo2 O4 HSs exhibited extremely high selectivity toward acetone gas with notable sensitivity (S = 69% to 5 ppm at 250 °C). The results demonstrate that MOF driven ultrasmall catalyst loaded TMO HSs were highly effective platform for high performance chemical gas sensors.