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Anal. Chem., 2012, 84 (16), pp 7043–7051.
Alex L. Robinson , Vitalie Stavila , Todd R. Zeitler , Michael I. White , Steven M. Thornberg, Jeffery A. Greathouse , Mark D. Allendorf
Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185, United States
Sandia National Laboratories, P.O. Box 969, Livermore, California 94551, United States
Abstract
The use of metal–organic framework (MOF) thin films to detect water vapor across a wide concentration range is demonstrated using MOF-functionalized quartz surface acoustic wave (SAW) sensors. A range of 3–14 800 ppmv was obtained with thin films of the MOF Cu3(benzenetricarboxylate)2 (Cu-BTC) deposited by an automated layer-by-layer method. Devices coated by a manual technique demonstrated sensitivity from 0.28 to 14 800 ppmv, the limit of our test system. This exceeds the sensitivity of many commercially available sensors. Cu-BTC layers were covalently bonded directly to the silicon oxide surface, allowing devices to be heated beyond 100 °C to desorb water adsorbed in the pores without decomposition, thereby regenerating the sensors. Sensor response as a function of coating thickness was evaluated, showing that the SAW sensor response is bounded by maximum and minimum layer thicknesses. Computer simulation of H2O uptake shows a multistep adsorption isotherm defined by initial adsorption at open Cu-sites, followed by pore-filling and finally full saturation. Modeling and experimental results are consistent. Calculated uptake values suggest an efficient adsorption of H2O by Cu-BTC. These results provide the first convincing evidence that MOF functionalization of compact sensing technologies such as SAW devices and microcantilevers can compete with state-of-the art devices.
Copyright © 2012 American Chemical Society
