Geometrically Mismatched Hydrogen‐bonded Framework Composed of Tetratopic Carboxylic Acid

Porous organic frameworks possessing interactive free sites in the pore have attracted much attention due to their potential to show the site‐originated specific functionalities. Herein, we demonstrate that such a framework could be constructed using a concept of geometrically mismatched frameworks composed of phenanthroline‐based tetratopic carboxylic acid CP‐Phen. Simple recrystallization of CP‐Phen yielded a solvent included porous framework CP‐Phen‐1, in which three of four carboxy groups form hydrogen‐bonded dimer to form a ladder‐shaped framework, while the remained one does not participate in framework formation due to geometrical mismatch and interacts with solvent molecules through weak hydrogen‐bonding. This result implies that our proposed strategy is effective to provide free interactive sites in porous frameworks. Although CP‐Phen‐1 undergoes two‐step structural transformation presumably accompanied by hydrogen‐bond rearrangements upon loss of solvent molecules, the activate framework shows good thermal stability up to 360 °C and selective CO2 adsorption. Geometrically mismatched assembly of CP‐Phen provides a ladder‐shaped hydrogen‐bonded framework with carboxy groups free from the framework formation.