Effect of the entanglement of microporous pillared MOFs on the uptake and release profiles of essential oil components

Metal-organic frameworks (MOFs) are a class of coordination polymers known for their intrinsic porosity. This property, combined with their ability to exhibit some degree of flexibility, makes them ideal materials for various innovative applications, like the inclusion and controlled release of active compounds for active packaging and agricultural applications. This study aimed to characterize the uptake and release behavior of an equimolar mixture of two phenolic essential oils (EOs), that is, carvacrol (CAR) and thymol (THY), encapsulated in two microporous Zn-based MOFs with different entanglement motifs: PUM168 is threefold interpenetrated and flexible, while PUM210 is fourfold polycatenated and rigid (PUM = Parma University Materials). The guest uptake was calculated using Nuclear Magnetic Resonance (1H NMR) spectroscopy and thermal gravimetric analysis (TGA) analysis, whereas the release profiles were investigated via headspace gas chromatography-mass spectrometry (HS-GC-MS) (Headspace-Gas Chromatography coupled with Mass-Spectrometry) analysis over a period of 15 days at room temperature. The monitoring revealed the superior ability of the flexible PUM168 for a stable and prolonged release of the volatile components, while the release from the rigid PUM210 was completed within 24 hours.