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Mesoporous Thin Films of “Molecular Squares” as Sensors for Volatile Organic Compounds

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journal contribution
posted on 04.03.2000, 00:00 by Melinda H. Keefe, Robert V. Slone, Joseph T. Hupp, Kenneth F. Czaplewski, Randall Q. Snurr, Charlotte L. Stern
Mesoporous thin films of rhenium-based “molecular squares”, [Re(CO)3Cl(L)]4 (L = pyrazine, 4,4‘- bipyridine), have been utilized as sensors for volatile organic compounds (VOCs). The sensing was conducted using a quartz crystal microbalance with the target compounds present in the gas phase at concentrations ranging from 0.05 to 1 mM. Quartz crystal microbalance studies with these materials allowed for distinction between the following VOCs:  (1) small aromatic versus aliphatic molecules of almost identical size and volatility and (2) an array of benzene molecules derivatized with electron donating/withdrawing substituents. The experiments suggest that the mesoporous host materials interact with VOC guest molecules through both van der Waals and weak charge-transfer interactions. In addition, size selectivity is shown by exposure of the molecular squares to cyclic ethers of differing size.