Gas separation membranes from polymers of intrinsic microporosity

When polymeric membranes are employed to remove selectively one component from a gaseous mixture, there is generally a trade-off between selectivity and permeability. Data are presented for two polymers of intrinsic microporosity, PIM-1 and PIM-7, which show a significant advance across the previous upper bound of performance for commercially important gas pairs, including O2/N2 and CO2/CH4. The exceptional properties of PIMs arise from their rigid but contorted molecular structures, which frustrate packing and so create free volume, coupled with chemical functionality giving strong intermolecular interactions.