Encapsulation of Menthylamide in β‐cyclodextrin Metal‐Organic Frameworks: Preparation, Characterization, and Sustained‐Release Properties

ABSTRACT Using menthylamide as the core material and β‐cyclodextrin (β‐CD) as well as its metal‐organic framework derivatives (β‐CD‐MOFs, including K‐β‐CD‐MOF and Na‐β‐CD‐MOF) as the wall materials, three types of composites‐menthylamide/β‐CD, menthylamide/K‐β‐CD‐MOF and menthylamide/Na‐β‐CD‐MOF were prepared via the coprecipitation and hybrid grinding method, respectively. The optimal preparation conditions were determined for each complex. Meanwhile, the prepared complexes were characterized by Fourier transform infrared (FTIR) spectroscopy, 1 H nuclear magnetic resonance ( 1 H NMR) spectroscopy, scanning electron microscopy (SEM), powder x‐ray diffraction (PXRD), nitrogen adsorption‐desorption analysis (BET), and thermogravimetric analysis (TGA). In addition, the effects of K + ‐ and Na + ‐ coordinated β‐CD‐MOFs on the encapsulation and thermal release of menthylamide were comparatively investigated. The results showed that the encapsulation percentage of menthylamide/Na‐β‐CD‐MOF reached 89.86%, which was higher than that of menthylamide/K‐β‐CD‐MOF. Characterization results confirmed that menthylamide had been successfully loaded onto the carriers, and its thermal stability was enhanced after loading. The 1 H NMR and BET results further supported the host‐guest interactions and changes in the pore structure after menthylamide loading. Furthermore, menthylamide/Na‐β‐CD‐MOF exhibited superior sustained‐release performance, and its release mechanism was better fitted with the Weibull model and proved to be relatively complex. Storage experiments further showed that both β‐CD‐MOF composites retained more than 95% of menthylamide after 15 days even at 50°C or 75% relative humidity, indicating favorable storage stability. These findings indicated that the loading of menthylamide onto Na‐β‐CD‐MOF could effectively improve its stability.