Metal–Organic Framework (MOF)-Derived SnO₂-ZnO Nanocomposites for Highly Sensitive NO₂ Detection

The presence of nitrogen dioxide (NO₂), a hazardous gas emanating from various sources including vehicles, industrial power plants, indoor combustion appliances, and tobacco smoke, underscores the importance of effective monitoring. Early risk assessment and continuous vigilance are vital to mitigate potential respiratory and cardiovascular consequences associated with prolonged exposure. To address this need, we have developed a cost-effective metal–organic framework (MOF)-derived SnO₂-ZnO-based gas sensor for NO₂ detection. Different combinations of SnO₂-ZnO were synthesized by varying the Sn/Zn molar ratio. The sensor SZ 1–0.5, having Sn/Zn = 1/0.5, demonstrated a superior response (R_g/R_a = 7.37) compared to bare SnO₂ and ZnO towards 100 ppm of NO₂ at 225°C. The fabricated SZ 1–0.5 sensor showed a good response time of 100 s with outstanding selectivity, cyclability, and repeatability. The enhanced gas-sensing characteristics of the sensor are attributed to the formation of heterojunctions. The gas-sensing mechanism is discussed in detail.