Construction of microporous polyimides with tunable pore size and high CO2 selectivity based on cross-linkable linear polyimides

Polyimides with intrinsic microporosity have been well developed and explored in the field of gas adsorption and separation. However, most linear polyimides without rigid and distorted segments do not have porous structure owing to the densely packed polymer chains. Two crosslinked polyimides (PEDA-PI-CL and PEQDA-PI-CL) were synthesized from 3,3’-bis(2,3,5,6-tetrafluoro-4-vinylphenoxy)-4,4’-biphenyldiamine (TFVBPA) with 2,5-bis(3,4-dicarboxyphenoxy)-4’-phenyl dianhydride (PEDA) and 2,5-bis(3,4-dicarboxyphenoxy)-4’-phenylethynyl phenyl dianhydride (PEQDA) through polycondensation and thermal crosslinking reactions. Here, the crosslinked structure is utilized to construct microporous polyimides because it can restrict the movement of polymer segments and prevent the polymer chains from dense packing. The micropore size, microporous structure and CO2 adsorption performance can be finely tuned by increasing the crosslinking density from PEDA-PI-CL to PEQDA-PI-CL. The micropore size reduces from 1.06 nm to 0....