Ionic-Functionalized Polymers of Intrinsic Microporosity for Gas Separation Applications.

Ionic-functionalized microporous materials are attractive for energy-efficient gas adsorption and separation processes and have shown promising results in gas mixtures at pressure ranges and compositions that are relevant for industrial applications. In this work, we studied the influence of different counterions (Li+, Na+, K+, Rb+, and Mg2+) on the porosity, carbon dioxide (CO2) gas adsorption, and selectivity in ionic-functionalized PIM-1 (IonomIMs), a polymer belonging to the class of linear and amorphous microporous polymers known as polymers of intrinsic microporosity (PIMs). It was found that an increase in the concentration of ionic groups led to a decrease in the free volume, resulting in a less porous polymer framework, and Mg2+-functionalized IonomIMs exhibited a relatively larger porosity compared to other IonomIMs. The CO2 adsorption capacity was affected by the different counterions for IonomIM-1, and a higher loading capacity for pure CO2 was observed for Mg2+. Furthermore, the IonomIMs showed an enhanced CO2 selectivity in CO2/CH4 and CO2/N2 gas mixtures at conditions used in pressure swing adsorption and vacuum swing adsorption applications. It was also observed that the concentration of ionic groups plays a vital role in changing the CO2 gas adsorption and selectivity.