Impact of ion mobility on the CO₂ solubility in ionic polymers

Increasing concentration of CO₂ in the atmosphere poses a significant threat to the environment, contributing to global warming and triggering disastrous weather events. Ionic polymers have become an important component in the CO₂ capture process. Similar to their monomeric counterparts (e.g., ionic liquids) polymers demonstrate unique solubility and selectivity in capturing CO₂. However, the mechanism underlying these processes remains unclear. In the case of ionic liquid, substantial research has been dedicated to deciphering the chemistry of the ions. It has been demonstrated that imidazolium–based ionic liquids show a remarkable solubility for CO₂ owing to their specific structural and chemical advantages. In case of polymers, the polymer's structural connectivity introduces an unknown variable of ion mobility to the equation, elevating the challenge of solving equation for CO2 transport to the next level.

In our study, we have conducted both experimental investigation and molecular modeling to explore the role of ion mobility in the polymers containing imidazolium-bistriflimide (TFSI) ion pair on the CO₂ solubility and diffusivity. From the experiment, we demonstrated that when TFSI is mobile, the material exhibits improved solubility and selectivity for CO2 compared to when TFSI is immobile. The simulations confirm that that TFSI ions have a greater affinity for CO₂ when it is mobile.