A Durable Metal–Organic Framework with a Hydrophobic sp ³ ‐Carbon‐Rich Nanospace Constructed from Flexible Medium‐Sized Ring Ligands

Despite the high design freedom of metal–organic frameworks (MOFs), flexible ligands that bear sp 3 ‐hybridized carbon atoms in their core are generally avoided as building blocks for MOFs because they may compromise framework stability. Herein, a 2D MOF (CBoard) is reported incorporating a dibenzocyclooctadiene with a flexible medium‐sized ring at the core as a flexible ligand. The moderate flexibility of the incorporated dibenzocyclooctadiene in CBoard reduces the strain induced by external stimuli on the coordination bonds, conferring cyclic stability upon guest adsorption–desorption. Furthermore, the sp 3 ‐hybridized carbon‐rich nanospace endows CBoard with water resistance and surface hydrophobicity. This hydrophobic nanospace preferentially captures ethanol over water, highlighting its potential for applications in ethanol–water separation in dilute aqueous solutions.