Ultrapermeable polymeric membranes based on particular ultra-rigid units for enhanced gas separation

To overcome the trade-off between permeability and selectivity of polymeric membranes and understand the influence of ultra-rigid units on gas separation performance, a series of PIMs (PIM-EN-x) based on spirodifluoranthene (EN) have been prepared. These polymers showed outstanding thermal stability. Their 5% weight loss temperature is higher than 503 °C. PIM-EN-x owned high BET surface area, ranging from 804 to 895 m2 g-1. With the increase of EN units, the gas permeability increased. The CO2 permeability of PIM-EN-40 is 11512 barrer, which is increased by 172% compared to PIM-1 with no loss in selectivity. The gas separation performance of PIM-EN-x surpassed the 2008 upper bound and near the latest upper bound. This work put forward a special structural unit to prepare polymers for CO2 separation and natural gas sweetening.