Microwave Regeneration and Thermal and Oxidative Stability of Imidazolium Cyanopyrrolide Ionic Liquid for Direct Air Capture of Carbon Dioxide

Abstract

AbstractUnderstanding the oxidative and thermal degradation of CO2sorbents is essential for assessing long‐term sorbent stability in direct air capture (DAC). The potential degradation pathway of imidazolium cyanopyrrolide, an ionic liquid (IL) functionalized for superior CO2capacity and selectivity, is evaluated under accelerated degradation conditions to elucidate the secondary reactions that can occur during repetitive absorption‐desorption thermal‐swing cycles. The combined analysis from various spectroscopic, chromatographic, and thermal gravimetric measurements indicated that radical and SN2 mechanisms in degradation are encouraged by the nucleophilicity of the anion. Thickening of the liquid and gas evolution are accompanied by 50 % reduction in CO2capacity after a 7‐day exposure to O2under 80 °C. To prevent long exposure to conventional thermal heating, microwave (MW) regeneration of the CO2‐reactive IL is used, where dielectric heating at 80 and 100 °C rapidly desorbs CO2and regenerates the IL without any measurable degradation.