Unique Ligand Exchange Dynamics of Metal-Organic Polyhedra for Vitrimer-like Gas Separation Membranes

Abstract

Metal-organic polyhedra (MOPs) possess a microporous framework and impose hierarchical constraints on their surface ligands, leading to the long-ignored, logarithmic ligand exchange dynamics. Herein, polymer networks with MOP as nanoscale cross-linkers (MOP-CNs) can integrate unique ligand exchange dynamics and microporosity, affording vitrimer-like gas separation membranes with promising mechanical performance and (re)processability. All the ligands on the MOP surfaces are confined and correlated via a 3D coordination framework and their neighboring spaces, giving rise to a high energy barrier for ligand exchange. Therefore, MOP-CNs demonstrate high mechanical strengths at room temperature due to their negligible ligand dynamics. The thermo-activated ligand exchange process with integrated network topology enables facile (re)processing and high solvo-resistance at high temperatures. This facilitates Arrhenius type temperature dependence of flowability and stress relaxation, giving rise to the simultaneous achievement of promising mechanical strengths and (re)processability. Finally, the cage topologies of MOPs endow the materials with a bonus microporous feature and spur their applications as gas separation membranes.