Novel Metal-Organic Framework-Assisted Synthesis of ZnO Nanoparticle-Decorated {221} SnO₂ Octahedrons for Improved Triethylamine Gas Sensing

The construction of composites based on metal oxideswith exposedhigh-energy facets is very significant in a wide range of applicationsincluding gas detection, catalysis, and energy storage. However, thesynthesis of such composites is always hindered by the smooth exposedsurface of metal oxides, which is difficult to nucleate and grow asecond component. To solve this problem, a novel metal-organicframework-assisted method was proposed to anchor ZnO nanoparticleson {221} facets of SnO2 octahedrons simply by a coatingand oxidation process of ZIF-8 on the smooth {221} surface. It wasfound that a high nucleation energy results from an appropriate ratioof Zn2+ and 2-methylimidazole, giving priority to the heterogeneousnucleation and growth process for ZIF-8 on the surface of SnO2 octahedral nanoparticles. The coverage of ZnO on the smoothsurface can also be modulated by the ZIF-8 film. Thanks to the newlydesigned composites with special structure, the gas-sensing performancesof {221} SnO2 were improved extensively, whose responsetoward 100 ppm triethylamine (TEA) can be increased more than tripletimes from 5.68 to 18.37 (R (a)/R (g)) by the combination of ZnO nanoparticles. This intensivelyimproved gas-sensing performance was attributed to the special structurewith extra sensitive depletion layers at the heterojunction as wellas the single-crystalline feature of SnO2 octahedral nanoparticles.These composites are thus promising gas-sensing materials for TEAdetection with excellent performances. More significantly, it canalso pave a new way to combine metal oxides with exposed high-energyfacets, providing a unique and effective means for enhancing the propertiesand functionality of materials in a range of fields.