Selective Binding and Removal of Aromatic Guests in a Porous Halogen-Bonded Organic Framework

Four binary porous halogen-bonded supramolecular organic frameworks (XOFs), namely, I@benzene, I@toluene, I@p-xylene, and I@o-xylene, have been synthesized by reactions of 1,4-difluoro-2,3,5,6-tetraiodobenzene and 1,2,4,5-tetra(4-pyridyl)benzene under the corresponding solvents. Single-crystal X-ray diffraction analysis shows that halogen bonding is responsible for the formation of the four dynamic porous XOFs. The frameworks in the four XOFs possess large flexible "breathing" one-dimensional channels which are able to bind aromatic guest molecules selectively. More interestingly, guest exchange studies have exhibited that a reversible single-crystal to single-crystal transformation accompanied reversible crystal expansion or shrinkage.