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 degrees C and selective CO2 adsorption.

Automated summary

This study demonstrates a method to construct porous organic frameworks with interactive free sites using the concept of geometrically mismatched frameworks, resulting in the successful preparation of CP-Phen-1 framework with such sites. The framework undergoes a two-step structural transformation upon loss of solvent molecules, yet exhibits good thermal stability up to 360 degrees C and selective CO2 adsorption.