"Interpenetration Isomerism" of Triptycene-Based Hydrogen-Bonded Organic Frameworks.

We describe an example of "interpenetration isomerism" in three-dimensional (3D) hydrogen-bonded organic frameworks (HOFs). By exploiting the crystallization conditions for a peripherally extended triptycene H6PET, we can modulate the interpenetration of the assembled frameworks, yielding a two-fold interpenetrated structure PETHOF-1 (acs-2c topology) and a five-fold interpenetrated structure PETHOF-2 (acs-5c topology) as "interpenetration isomers". In PETHOF-1, two individual nets are related by inversion symmetry and form an interwoven topology with a strikingly large guest-accessible volume of about 80%. In PETHOF-2, five individual nets are related by translational symmetry and are stacked in an alternating fashion. Additionally, the activated materials show permanent porosity with high Brunauer-Emmett-Teller (BET) areas exceeding 1100 m2•g-1. We believe that synthetic control over the framework interpenetration can serve as a new design strategy to construct diverse and complex supramolecular architectures from simple organic building blocks.