In Situ Encapsulation of Cationic [2]Catenane in a Stable Zirconium Metal-Organic Framework

As an emerging class of porous supports, metal-organic frameworks (MOFs) can host multifarious guests to realize diverse applications. Among the guest-introducing approaches, the in situ encapsulation method is unique in its ability to incorporate a diverse range of guests, from small organic molecules and metal clusters to proteins and even more complicated guests. Previous investigations have focused on guests that are either neutral or negatively charged. The realization of the in situ encapsulation of cationic catenanes in MOFs under mild conditions, however, has rarely been investigated. Herein, we have accomplished in situ encapsulation of a cationic catenane (DA[2]C) within UiO-66-F₄─a MOF consisting of Zr₆ nodes and tetrafluoroterephthalic acid ligands─at room temperature using H₂O as a green solvent. Theoretical calculations elaborated that tetrafluoroterephthalic acid ligands interact strongly with the cationic DA[2]C. This observation is a result of electrostatic interactions between carboxylate anions and DA[2]C cations as well as the attraction of electronegative F atoms in tetrafluoroterephthalic acid to the cations. As a proof-of-concept application, the DA[2]C·4Cl/UiO-66-F₄ composite demonstrated heterogeneous catalytic detoxification of 2-chloroethyl ethyl sulfide to the sulfoxide with a complete conversion rate (>99%) and high selectivity (>97%). This method could also be extended to other organic cationic molecules, including dibenzyl benzoimidazoloimidazole chloride and a pyrene-functionalized cyclobis(paraquat-p-phenylene), rendering it as a universal platform for constructing host-guest MOF systems with various applications.