Metal-Organic Framework Templated Catalysts: Dual Sensitization of PdO-ZnO Composite on Hollow SnO Nanotubes for Selective Acetone Sensors.

Metal-organic framework (MOF)-derived synergistic catalysts were easily functionalized on hollow SnO nanotubes (NTs) via electrospinning and subsequent calcination. Nanoscale Pd NPs (∼2 nm) loaded Zn-based zeolite imidazole framework (Pd@ZIF-8, ∼80 nm) was used as a new catalyst-loading platform for the effective functionalization of a PdO@ZnO complex catalyst onto the thin wall of one-dimensional metal oxide NTs. The well-dispersed nanoscale PdO catalysts (3-4 nm) and multiheterojunctions (PdO/ZnO and ZnO/SnO) on hollow structures are essential for the development of high-performance gas sensors. As a result, the PdO@ZnO dual catalysts-loaded hollow SnO NTs (PdO@ZnO-SnO NTs) exhibited high acetone response (R/R = 5.06 at 400 °C @ 1 ppm), superior acetone selectivity against other interfering gases, and fast response (20 s) and recovery (64 s) time under highly humid atmosphere (95% RH). In this work, the advantages of hollow SnO NT structures with high surface area and open porosity were clearly demonstrated by the comparison to SnO nanofibers (NFs). Moreover, the sensor arrays composed of SnO NFs, SnO NTs, PdO@ZnO-SnO NFs, and PdO@ZnO-SnO NTs successfully identified the patterns of the exhaled breath of normal people and simulated diabetics by using a principal component analysis.