Metal-organic frameworks derived porous Co3O4 dodecahedeons with abundant active Co3+ for ppb-level CO gas sensing

Abstract

Co3O4 dodecahedeons with abundant trivalent cobalt cation (Co3+) and surface absorbed oxygen species were prepared via regulating calcination temperature and heating rate of Co-based metal-organic framework (ZIF-67) templates. The influence of the calcination temperature and heating rate on the relative content of trivalent cobalt cation has been discussed in detail. The gas-sensing experiment demonstrates that the Co3O4 dodecahedeons with abundant active Co3+ exhibit significantly enhanced response to CO and a low detection limit (≤500 ppb). The response value is 20 times higher than that of Co3O4 nanoparticles to CO at the relatively low temperature of 150 °C and exhibits rapid response-recovery, good stability, reproducibility and selectivity. Such superior sensing performance to CO is mainly due to the accessible octahedral trivalent cobalt cation active sites and abundant absorbed-oxygen species as well as the large specific surface area which is beneficial to CO absorption, diffusion and the surface redox reaction. This facile method sheds light on the reasonable design of Co3O4 with different relative content of trivalent cobalt ion. The results afford decisive insights to realize the influence of Co3+ on the gas-sensing performance to CO, which allows new choices to design highly sensitive gas sensors.