Novel copolymers with intrinsic microporosity containing tetraphenyl-bipyrimidine for enhanced gas separation

Abstract

The gas separation of polymers of intrinsic microporosity (PIMs) was enhanced by incorporating bipyrimidine (bpy) into the polymer (PIM-bpy-x) through the polycondensation of a novel tetraphenyl-bipyrimidine monomer. The structures of PIM-bpy-x were investigated with 1H NMR and FT-IR. Because of the excellent heat resistance imparted by the tetraphenyl-bipyrimidine unit, PIM-bpy-x displayed better thermal stability than did PIM-1. These polymers displayed large Brunauer-Emmett-Teller (BET) surface areas, ranging from 656 to 728m2g−1. The BET surface area of PIM-bpy-5 was 728m2g−1, which was similar to that of PIM-1 (774m2g−1). PIM-bpy-x exhibited excellent gas separation performance. PIM-bpy-5 showed the highest CO2 permeability (5141 barrer), which was much higher than that of PIM-1 (4234 barrer). The increase in CO2 permeability is due to the affinity between the N-rich bipyrimidine units and CO2. Furthermore, PIM-bpy-x also showed greater resistance to aging than did PIM-1. All of the above indicate that introducing bipyrimidine units into the polymers can enhance the gas separation performance of PIMs.