A Metallosupramolecular Shape‐Memory Polymer with Gradient Thermal Plasticity

Solid‐state plasticity by dynamic covalent bond exchange in a shape‐memory polymer network bestows a permanent shape reconfiguration ability. Spatio‐selective control of thermally induced plasticity may further extend the capabilities of materials into unexplored domains. However, this is difficult to achieve because of the lack of spatio‐control in typical polymer network synthesis. Metal–ligand interactions possess the high strength of covalent bonds while maintaining the dynamic reversibility of supramolecular bonds. Metallosupramolecular shape‐memory polymer networks were designed and prepared, which demonstrated solid‐state plasticity. The metallo‐coordination bonds within these networks permit facile tuning of the plasticity behavior across a wide temperature range, simply by changing the metal ion. By controlling the diffusion of two different metal ions during preparation of a polymer film, a plasticity behavior with a spatial gradient was achieved, providing a unique shape‐morphing versatility with potential in shape‐memory devices.     

Lock‐and‐Key and Shape‐Memory Effects in an Unconventional Synthetic Path to Magnesium Metal–Organic Frameworks

We report a new magnesium metal–organic framework (MOF) (CPM‐107) with a special interaction with CO₂. CPM‐107 contains Mg₂‐acetate chains crosslinked into a 3D net by terephthalate. It has an anionic framework encapsulating ordered extra‐framework cations and solvent molecules. The desolvated form is closed and unresponsive to common gasses, such as N₂, H₂, and CH₄. Yet, with CO₂ at 195 K, it abruptly opens and turns into a rigid porous form that is irreversible via desorption. Once opened by CO₂, CPM‐107 remains in the stable porous state accessible to additional gas types over multiple cycles or CO₂ itself at different temperatures. The porous phase can be re‐locked to return to the initial closed phase via re‐solvation and desolvation. Such peculiar properties of CPM‐107 are apparently linked to a convergence of factors related to both framework and extra‐framework features. The unusual CO₂ effect is currently the only available path to porous CPM‐107 which shows efficient C₂H₂/CO₂ separation.