Microporosity Enhancement in a One-Dimensional Imidazolium Caged Metal-Organic Framework by Highly Selective Postsynthetic Removal of Inner Yttrium Clusters

Abstract

A one-dimensional (1D) metal-organic caged framework (YMOF-Y) was obtained via self-assembly of yttrium cations with a U-shape imidazolium based ligand and the structure was elucidated by single-crystal X-ray diffraction analysis. The YMOF-Y has a unique 1D chain structure composed of octa-imidazolium based cages. Inside the cage, an inner Y-4 cluster connected to yttrium cations of the cage through formate anions is present. The microporosity and flexibility of YMOF-Y can be improved by an unprecedented postsynthetic removal of the Y-4 clusters from the cage by washing with alkali metal solutions. The removal of the Y-4 cluster is reflected in a significant change in the properties of the metal-organic framework (MOF), as confirmed by carbon dioxide sorption measurements and variable temperature powder X-ray diffraction analysis.