Humidity-resistant room-temperature VOC gas sensor based on a hydrophobically modified metal-organic framework with a hierarchical inverse-opal structure

초록

Metal-organic frameworks (MOFs) are attractive sensing materials for quartz crystal microbalance (QCM)-based gas sensors because of their high surface area, tunable pore structures, and strong adsorption capability at room temperature. However, their practical application is often limited by humidity interference caused by competitive water adsorption. In this study, a humidity-resistant room-temperature volatile organic compound (VOC) sensor was developed using a hierarchical inverse-opal sensing membrane derived from octadecylamine (ODA)modified Sn-BTC on a QCM platform. The sensing membrane combines hydrophobic surface characteristics that suppress water adsorption with an interconnected inverse-opal architecture that facilitates gas transport and improves access to adsorption sites within the porous sensing layer. The inverse-opal structure substantially enhanced the gas response compared with bare and flat-film-coated QCM sensors. The ODA-modified sensor exhibited a low humidity dependence of 0.21 Hz/%RH over the 0-80% RH range at 25 degrees C. It also showed systematic concentration-dependent responses over the range of 100-500 ppm, with sensitivities of 7.07, 4.83, 1.25, and 0.206 Hz ppm-1 for acetone, isopropanol, methanol, and toluene, respectively. The combination of hydrophobic functionalization and hierarchical structural engineering therefore provides an effective strategy for stable room-temperature VOC sensing under variable-humidity conditions.

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