Interface-engineering in MOF-derived In2O3 for highly sensitive and dual-functional gas sensor towards NO2 and triethylamine

Nitrogen dioxide (NO2) and triethylamine (TEA) vapor are two typical reactive nitrogen species harmful to personal health and the environment. Thus, multi-functional and reliable sensors were momentous. Herein, the interface engineering of MOF-derived In2O3 with various contents of oxygen vacancy (OV) and different crystalline phases was achieved via pyrolysis of NH2-MIL-68(In) at different temperatures. High-proportional mixed hexagonal and cubic crystalline phases were presented in the MOF-derived In2O3 obtained by pyrolysis of NH2-MIL-68(In) at 400 °C (MOF-In2O3-400). Benefiting from the larger surface and interface area, MOF-In2O3-400 exhibited abundant OV and improved gas-sensing performance compared with the samples obtained at 500 °C and 600 °C. Interestingly, the MOF-derived In2O3 sensors exhibited dual-selective and ppb-level detection of NO2 and TEA vapor at distinct optimum operating temperatures. MOF-In2O3-400 exhibited ultra-high response of 1210 to 200 ppb NO2, and can detect as low as 1 ppb NO2 at 30 °C and TEA vapor as low as 500 ppb at 200 °C. It was also assessed for excellent long-term stability up to 120 days. As a practical demonstration, a prototype device was fabricated on an integrated circuit platform to issue a warning when NO2 or TEA concentrations exceeded the safety thresholds. The results indicate that the MOF-In2O3-400 is an excellent candidate in temperature-dependent dual-functional gas sensors towards NO2 and TEA vapor.