Exo‐Functionalized Shape‐Persistent [2+3] Cage Compounds: Influence of Molecular Rigidity on Formation and Permanent Porosity

The bigger the better? Rigidity is more important than size for the construction of permanent porous crystals from organic cage compounds. Two [2+3] cage compounds have been synthesized by an imine condensation reaction. The one consisting of rigid subunits (figure left) has an accessible BET surface area of 744 m2 g−1, whereas the cage compound with flexible subunits is basically nonporous (BET surface area: 30 m2 g−1) although the shape-persistent cavity is larger (9.8 vs. 7.8 Å).