Titanium-based metal-organic-framework-coated SnO2 nanowires with enhanced NO2 gas sensing capability in humid environment

Herein, the NO2 gas sensing features of SnO2 nanowires (NWs) and titanium-based metal–organic framework 901 (MOF-901)-coated SnO2 NWs were investigated. Both gas sensors showed excellent selectivity to NO2. At 200 °C, the responses of SnO2 NWs and MOF-901-coated SnO2 NWs to NO2 (10 ppm) were 9.7 and 8.2, respectively. However, in a humid atmosphere, the latter nanowires showed better performance, mainly because of their hydrophobic nature and the metal–organic framework layer. At relative humidities (RHs) of 20% and higher, the MOF-901-coated sensor showed higher performance than the pristine sensor. In particular, at 80% RH, responses of 6.6 and 4.0 were obtained for these two sensors to 10 ppm NO2, respectively. Furthermore, the MOF-901-coated SnO2 NWs showed better selectivity than the other sensor. We showed that MOF-901 behaved an important role in reducing the effects of water vapor and that it can be used as a molecular sieve for enhancing the NO2 gas response of SnO2 NWs in humid environments.