Metal-organic framework driven metal-metal oxide complex catalyst sensitized on nanofiber scaffold: superior chemical gas sensors

Abstract

We report on novel sensitization of metal-metal oxide complex catalysts onto semiconductor metal ox-ide (SMO) nanofibers (NFs) achieved by metal-organic framework (MOF) templating and electrospinning routes. Pd nanoparticles (2~3 nm) encapsulated in the cavity of zeolite imidazole framework (ZIF-8, ~ 100 nm) were mixed with electrospinning solution and embedded in electrospun W precursor/polyvinylpyrrolidone composite NFs. After calcination process, Pd-loaded ZnO nanocubes (Pd-ZnO) derived from Pd embedded Zn based MOF were effectively sensitized on interior and exterior of $WO_3$ NFs, resulting in the build-up of multi-heterojunctions of Pd-ZnO and $ZnO-WO_3$. Surprisingly, the Pd-ZnO loaded $WO_3$ NFs exhibited a superi-or toluene sensitivity ($R_{air}/R_{gas} = 4.37 to 100 ppb$) and selectivity against other interfering analytes. Moreover, the gas responding speed was dramatically enhanced (~20 sec) compared to pristine $WO_3$ NFs (~44 sec). These results demonstrate that MOF-driven metal-metal oxide complex catalysts can be functionalized within metal-oxide nanofiber scaffold during electrospinning, thereby creating multi-heterojunctions for catalytic sensitization. This feature can pave a new way of complex catalyst synthesis for potential application in high performance chemical gas sensors.