Energetics of Confinement of n-Hexane in Ca–Na Ion Exchanged Zeolite A

Study of the energetics of confinement of small organic molecules in microporous frameworks provides essential information for rational design and application of functional porous materials. Using immersion calorimetry and temperature-programmed desorption coupled with mass spectroscopy, we describe the complex guest–host interactions of a nonpolar organic molecule ( n -hexane) with a series of calcium-exchanged zeolite A materials whose pore accessibility was modified by varying the calcium content to achieve inaccessible, partially accessible, and fully accessible central cavities for n -hexane molecules. The overall magnitude and trend with the pore size of n -hexane–zeolite A interactions have been determined. In addition, the contributions to energetics from the external surface (Δ H wet ), tetrahedral framework (Δ H g-h ), and adjacent n -hexane molecules (Δ H g-g ) were separated, quantified, and interpreted.