Microporous Polyimides from Ladder Diamines Synthesized by Facile Catalytic Arene–Norbornene Annulation as High-Performance Membranes for Gas Separation

We synthesized a series of rigid ladder-type diamines from readily available bromoanilines and norbornadiene in one step using facile catalytic arene–norbornene annulation (CANAL). Polycondensation of CANAL ladder diamines with 4,4′-(hexafluoroisopropylidene)­diphthalic anhydride led to a series of microporous polyimides with different degrees of rotational freedom around the imide linkages. CANAL-PIs exhibited good solubility in a wide range of organic solvents, high thermal stability with decomposition temperature above 450 °C, high Brunauer–Emmett–Teller surface areas of ∼200–530 m2 g–1, and abundant micropore volume with variable pore size distributions. Mechanically robust membranes can be easily formed from CANAL-PIs and gave high gas permeabilities and moderate gas-pair selectivities. CANAL-PIs had higher permeability than and similar permselectivity to analogous PIs synthesized from Tröger’s base and carbocyclic Tröger’s base diamines under identical test conditions. CANAL-PIs also exhibited relatively slow physical aging. These favorable properties and performance make microporous polymers based on CANAL ladder motifs promising membrane materials for gas separation.