Encapsulation of Highly Volatile Fragrances in Y Zeolites for Sustained Release: Experimental and Theoretical Studies

Volatility is an inherent fragrance attribute and typically implies a reduced perception over time. One possibility to elongate odor perception is utilizing controlled fragrance-delivery systems. Herein, the Y type of faujasite with different extra-framework cations (abbreviated as ZY, where Z represents Na⁺, Ca²⁺, or La³⁺) was examined as potential carriers for fragrance entrapment and delivery. d-Limonene (Lim) and linalool (Lol) as model fragrances were loaded in the pore space of Y zeolites, yielding composites FG@ZY (FG = Lim, Lol). It was found that the fragrance release profiles correlate highly with the cationic species located in the nonframework. The retention of fragrances in matrices increases in the order NaY < CaY < LaY for either limonene or linalool. Interestingly, the release rate of limonene was significantly slower than that of linalool when encapsulated in the same zeolite, although neat limonene has a much higher saturated vapor pressure than linalool. For instance, the total fraction of aroma released from Lim@LaY over 30 days was about 10%, while the value was ∼20% for Lol@LaY. Based on the density functional theory calculations, the above results could be well rationalized by the electrostatic attraction and shape selectivity of microporous matrices to the dopant molecules.