Metal-organic framework-derived porous SnO2 nanosheets with grain sizes comparable to Debye length for formaldehyde detection with high response and low detection limit

The development of metal oxide semiconductors-based gas sensors that can simultaneously achieve high response and low detection limit towards formaldehyde (HCHO) remains a great challenge so far. In this work, we present the formation of porous SnO2 nanosheets via direct calcination of a Sn-based metal-organic framework that was prepared via a facile wet chemistry method with deionized water as solvent at 80 degrees C. The porous SnO2 nanosheets are found to be constructed by the interconnection of ultrafine nanoparticles with sizes of 4-9 nm, which is comparable to the Debye length of SnO2. The gas sensor based on the porous SnO2 nanosheets demonstrate a broad detection range towards HCHO (0.05-500 ppm), a low operating temperature (140 degrees C), very high response (540.8 to 50 ppm HCHO), extremely low detection limit (0.31 ppb), ideal selectivity, and outstanding reproducibility and durability. The excellent HCHO-sensing performance of the SnO2 sensor could be attributed to the high specific surface area (125.92 m2/g) of the porous SnO2 nanosheets, the ultrafine sizes of the SnO2 nanoparticles, and the presence of abundant of mesopores within the nanosheets. The porous SnO2 nanosheets with excellent HCHO-sensing characteristics may find widespread applications in fabricating gas sensors for detecting ppb-level HCHO.