2D covalent organic framework via catenation

Molecular-level structural modification is a well-established approach to impart advanced functionality to materials that continues to be the focus of research and development in both academic and industrial laboratories. Here, we report the synthesis of an ordered two-dimensional (2D) poly[2]catenate from the simultaneous self-assembly of two organic ligands and a metal salt by the formation of catenate links using both metal coordination and imine condensation reactions. Subsequent chemical reduction of the imine bonds generated the corresponding demetallized poly[2]catenane, which was found to have greater non-rigid-body-like character than the poly[2]catenate as a result of the increased internal dynamics of the mechanical bonds and resulted in an 8-fold increase in elasticity. This synthetic approach allowed for the efficient incorporation of mechanically interlocked molecules (MIMs) within a 2D ordered structure and demonstrated their importance in improving the physical properties of materials by accessing molecular degrees of freedom that cannot be achieved by other means.