Chiral Motifs in Interpenetrated Metal-Organic Frameworks Formed from Achiral Tetrahedral Ligands

We demonstrate the formation of highly interpenetrated frameworks. An interesting observation is the presence of very large adamantane-shaped cages in a single network, making these crystals new entries in the collection of diamondoid-type metal-organic frameworks (MOFs). The frameworks were constructed by assembling tetrahedral pyridine ligands and copper dichloride. Currently, the networks’ degree of interpenetration is among the highest reported and increases when the size of the ligand is increased. Usually, highly interpenetrated frameworks have low surface contact areas. In contrast, in our systems, the voids take up to 63% of the unit cell volume. The frameworks are chiral and formed from achiral components. The chirality is manifested by the coordination chemistry frameworks around the metal center, the structure of the helicoidal channels and the motifs of the individual networks. Channels with both chiralities are present within the unit cells. This phenomenon shapes the walls of the channels, which are composed of 10, 16, or 32 chains correlated to the degree of interpenetration 10-, 16- and 32-fold. By changing the distance between the center of the ligand and the coordination moieties, we succeeded to tune the diameter of the channels. Relatively large channels were formed, having diameters up to 31.0 A × 14.8 A.