A Colorimetric Sensor for the Highly Selective, Ultra-sensitive, and Rapid Detection of Volatile Organic Compounds and Hazardous Gases

We present a new colorimetric chemosensor of formula [Fe­(H2btm)2(H2O)2]­Cl2 (1) (H2btm = di­(1H-tetrazol-5-yl)­methane), allowing to detect at real time, with a high selectivity and ultra-sensitivity, 14 different volatile organic compounds (VOCs) and hazardous gases (HGs), in particular amines, which are detected very quickly (3), 0.62 ppm for hydrazine (NH2–NH2), 0.45 ppm for isobutylamine, and 0.71 ppm for diethylamine). The detection is accompanied by significant and fast color changes detectable by the naked eye at ambient conditions. In addition, different VOCs could be distinguished by simple and intuitive standard chemometric means using a handful smartphone-based analytical method, offering a large color panel depending on the detected molecules. The crystal lattice of 1 reconstructs after adsorbing VOCs vapors, reconstruction that is accompanied by a spin state and a color change. In addition to its high thermal stability (up to 170 °C), the colorimetric sensor showed excellent reusability by consecutive 7 cycles of adsorption–desorption. It operates at ambient conditions, is low cost, environmentally friendly, and easy to use, and shows excellent and fast detection performances. Such features offer attractive prospects for 1, which could be used for in-field detection and food safety control in environmental conditions.