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

Abstract

Mesoporous thin films of rhenium-based “molecular squares”, [Re(CO)₃Cl(L)]₄ (L = pyrazine, 4,4‘-\nbipyridine), have been utilized as sensors for volatile organic compounds (VOCs). The sensing was conducted\nusing a quartz crystal microbalance with the target compounds present in the gas phase at concentrations\nranging from 0.05 to 1 mM. Quartz crystal microbalance studies with these materials allowed for distinction\nbetween the following VOCs: (1) small aromatic versus aliphatic molecules of almost identical size and\nvolatility and (2) an array of benzene molecules derivatized with electron donating/withdrawing substituents.\nThe experiments suggest that the mesoporous host materials interact with VOC guest molecules through\nboth van der Waals and weak charge-transfer interactions. In addition, size selectivity is shown by exposure\nof the molecular squares to cyclic ethers of differing size.