Assembly of Functionalized MIL-101 ( Cr )- loaded Quartz Crystal Microbalance Gas Sensors for Formic Acid Detection

Volatile organic compounds(VOCs) are considered as one of the major components in atmospheric pollutants, and pose serious hazards to both human health and the environment. It is urgent to develop new highefficient detection techniques for VOCs. In this work, ethylenediamine(ED) and ethanolamine(EA) were grafted into MIL -101(Cr) to obtain ED - and EA -derived MIL -101(Cr) materials[labeled as MIL -101(Cr) -ED and MIL -101 (Cr ) -EA ], respectively. Then , these three MIL -101 (Cr ) materials were loaded on the surface of quartz crystal through dip coating to assemble three kinds of MIL -101 (Cr ) -modified quartz crystal microbalance (QCM ) gas sensors , respectively. Moreover , the sensing and recognition performance of these QCM sensors toward methanol , ethanol , 2 -propanol , acetone , cyclohexane , diethylamine , formic acid , formaldehyde , ammonia , and acetic acid were studied in detail. As indicated , MIL -101 (Cr ) -ED - and MIL -101 (Cr ) -EA -loaded QCM sensors showed better sensing performance for formic acid in comparison with the original MIL -101 (Cr ) -based sensor , and the oscillation frequency of these two sensors decreased by -375.6 and -232.1 Hz when the concentration of formic acid was 350 mg/L , respectively. Delta f value was linearly related to the concentration of formic acid in the range of 5 - 350 mg/L. In addition , the sensitivity of MIL -101 (Cr ) -ED -loaded QCM gas sensor was estimated to be 0.95 Hz <middle dot>L <middle dot>mg -1 and the limit of detection was 0.95 mg/L. As a result , this MIL -101 (Cr ) -modified QCM gas sensor demonstrated high sensitivity , low detection limit , and good repeatability. In brief , this research would provide some useful information for developing new QCM gas sensors in real -time VOCs detection.