MOF Sensors Based on Piezoresistivity

Industrial Catalysis and Separations Innovations for Process Intensification 

An example is HKUST-1, which, although small, shows adsorption-induced distortions when water, methanol, or ethanol are reversibly adsorbed. Allendorf et al. showed this property when a thin film of HKUST-1 was integrated with a microcantiveler surface [94]. The time-dependent responses to H O are shown in Fig. 3.12. It was also demonstrated that the sensor responds to CO2 when the MOF layer is dehydrated. The stress in this case was due to the coordination of COj with imsaturated copper sites in HUKST-1. Because the framework distortions were quite small, the group concluded that higher sensitivities can be achieved using more flexible MOFs. 

FIGURE 3.12 Temporal response of the cantilever piezoresistive sensor to water vapor diluted in (room temperature, 1 atm) [94]. (Reproduced with permission Allendorf, M.D. et al., J.4 i Chem Soc 130,14404 (2008), with permission). 

Thin films of MOF materials can also be applied on quartz crystal microbalances (QCMs). In this fashion, it is possible to take advantage of the extremely high sensitivity to mass changes on the QCM surface when an analyte interacts with the cavities of the MOF. Detection limits on the order of 

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