MOF-Derived SnO2 hollow spheres for Acetone Gas Sensing

A rational design of gas-sensing materials is critical in achieving shorter gas diffusion lengths, improved surface reaction, and relatively high sensor sensitivity. In this work, unprecedented Sn-MOF templating technique and high-temperature calcination were employed, to synthesize SnO₂ hollow spheres (SnO₂HS). The hollow morphology resulted from the inner gas evacuation and the inside-out Ostwald ripening during calcination in air. The SnO₂ HS were characterized by scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Barrett-Joner-Halenda, and Brunauer–Emmett–Teller methods, followed by an investigation of their gas-sensing performance. The SnO₂ HS were composed of nanoparticle aggregates with a crystallite size of 9.6 nm, and they exhibited an average diameter and shell thickness of 402 and 30.9 nm, respectively. The spheres showed an excellent response (R_a/R_g = 20.8), fast response (4.6 s), and good stability toward 5-ppm acetone at 350 °C in dry conditions. This work demonstrates that 2-methylimidazole is an effective ligand for the fabrication of SnO₂ HS with remarkable acetone-sensing performance, which can be extended for the synthesis of other metal oxides spheres.