Encapsulation of Hydrophobic Guests within Metal-Organic Framework Capsules for Regulating Host-Guest Interaction

Metal-organic frameworks (MOFs) are suitable for studying host-guest chemistry by virtue of their component diversities, porous structures, and facile production. As the host materials, MOFs have been developed to incorporate various functional species, which not only entitle MOFs with new features originating from functional species but also significantly improve the intrinsic properties of MOFs and functional species. Although hydrophobic molecules are a kind of special functional species with promising properties, such as organic dyes, organic catalysts, and drugs, they are challenging in terms of encapsulation in MOFs mainly because of their intrinsic hydrophobic properties and poor solubility in aqueous media, thus strongly limiting their application. Herein, we propose a universal and flexible strategy for effectively encapsulating hydrophobic guests without complicated modification inside MOF capsules (MOF-Cs), which are constructed by self-assembly of MOF nanoparticles in a water-oil interface. MOF-Cs as large-capacity host materials can encapsulate various types of hydrophobic guests, which improve energy transfer and promote size-selective catalysis. Specifically, the interaction between MOF-Cs and the encapsulated hydrophobic dyes improve fluorescence resonance energy transfer.