Microporous Polyimides with Rationally Designed Chain Structure Achieving High Performance for Gas Separation

Polyimides of intrinsic microporosity are important polymers for gas separation. Achieving polyimides with high permeability and high selectivity relies on rationally designing their chain structure. In this work, new ladder-like diamines, Tröger’s Base (TB) derived diamines, are designed, and two microporous polyimides are constructed by polymerizing TB-derived diamines and spirobisindane based dianhydride, aiming at enhancing the stiffness of the whole backbone and thus achieving improved performance by taking advantage of the stiffness of both diamines and dianhydride. The two polyimides present excellent separation performance, surpassing the 2008 Robeson upper bound for gas pairs of H 2 /N 2 and O 2 /N 2 and approach the 2008 Robeson upper bound for gas pairs H 2 /CH 4 and CO 2 /CH 4 . Our results show that the designed polyimides have great potential for application especially for oxygen (O 2 /N 2 ) and hydrogen (such as H 2 /N 2 and H 2 /CH 4 ) related separation.