Strain-based chemical sensing using metal-organic framework nanoparticles

Metal-organic frameworks (MOFs) have received much attention for their potential as chemical sensors, owing to unparalleled tunability of their host-guest response, high uptake and structural flexibility. However, because of the limited compatibility between MOF properties and sensor transduction mechanisms, very few MOFs have successfully been integrated into practical devices. We report the fabrication of the first strain-based sensor constructed from MOF nanoparticles deposited directly onto a membrane-type surface stress sensor (MSS) architecture, which exhibits unprecedented response times on the order of seconds and ppm-level sensitivity towards volatile organic compounds (VOCs). Finite element analysis is used to demonstrate that the sensor response is a result of analyte-induced strain in the MOF receptor layer. We show that an array of four types of MOF nanoparticles allows for clear discrimination between different classes of VOCs and even individual gases, using principal component analysis of their response profiles. This work opens up the possibility of VOC sensing using a wide range of MOFs, beyond those that are electrically conducting or those that form oriented thin films, with the added advantages of high sensitivity and rapid response compared to existing MOF strain-based sensors. A membrane-type surface stress sensor (MSS) featuring metal-organic framework nanoparticles shows rapid, discriminative and ppm-level responses to volatile organic compounds.