Biocompatible Cyclodextrin-Based Metal–Organic Frameworks for Long-Term Sustained Release of Fragrances

The encapsulation of volatile fragrances within porous materials is capable of increasing their stability for long-term controlled release; however, the introduction of low biocompatible carrier materials also increases safety concerns, thus limiting their applications. Here, we demonstrate the usage of a nontoxic biocompatible porous material, γ-cyclodextrin-based metal–organic framework (γ-CD-MOF), for the effective encapsulation and sustained release of fragrances. Two ester- and two terpene-type fragrances were used as model fragrances for encapsulation. Compared with γ-CD, the γ-CD-MOF nanocrystals showed higher encapsulation capability for the two ester-type fragrances and superior sustained release for all of the tested fragrances. The host–guest hydrophobic and hydrogen-bonding interactions between the fragrant molecules and the γ-CD units/γ-CD-MOFs were studied by Fourier-transform infrared spectroscopy and molecular docking. We find that the release profiles of the two ester-type fragrances are linear and can be fitted well by the zero order model, whereas those for terpene-type fragrances show an initial burst release with better fitting using the Weibull model.