Probing zeolites with organic molecules: supercages of X and Y zeolites are superpolar

Abstract

Supercages of Li⁺- and Na⁺-exchanged X and Y zeolites are much more polar than even water. The extent of polarity depends on the nature and the number of cations present within a supercage. The polarity of Li⁺- and Na⁺-exchanged X and Y zeolites decreases in the presence of water. In presence of water the contribution of cations toward polarity is much smaller than water itself. In this study polarity has been monitored with organic probe molecules, Nile red, pyrene 1-carboxaldehyde and coumarin-500. A connection between "polarity" and "electric field" within a cage has also been established. Since the supercages are much more polar than all organic solvents, they can be characterized as "superpolar". Because of this one may be able to achieve excited-state switching of carbonyl compounds within a zeolite while such may not be possible in organic solvents. The nΠ*-ΠΠ* state switching of acetophenones is easily achieved within a zeolite while such does not occur in polar solvent methanol-ethanol mixture.