Statically and dynamically flexible hydrogen-bonded frameworks based on 4,5,9,10-tetrakis(4-carboxyphenyl)pyrene.

Aperture shape and size of flexible hydrogen-bonded organic frameworks (HOF) were statically modulated using various aromatic solvents, and dynamically changed by desorption and adsorption of the solvent molecules.

Single Crystalline, Non-stoichiometric Cocrystals of Hydrogen-Bonded Organic Frameworks.

Porous frameworks composed of non-stoichiometrically mixed multicomponent molecules attract much attention from a functional viewpoint. However, their designed preparation and precise structural characterization remain challenging. Herein, we demonstrate that cocrystallization of tetrakis(4-carboxyphenyl)hexahydropyrene and pyrene derivatives (CP-Hp and CP-Py, respectively) yields non-stoichiometric mixed frameworks through networking via hydrogen bonding. The composition ratio of CP-Hp and CP-Py in the framework was determined by single crystalline X-ray crystallographic analysis, indicating that the mixed frameworks were formed over a wide range of composition ratios. Furthermore, microscopic Raman spectroscopy on the single crystal indicates that the components are not uniformly distributed such as ideal solid solution, but are done gradationally or inhomogeneously.

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.