Ionic Liquids and Poly (Ionic Liquids) for CO2 Capture: A Comprehensive Review

The rising concentration of atmospheric carbon dioxide (CO2), driven largely by fossil fuel combustion, is a major contributor to global climate change and ocean acidification. As conventional CO2 capture technologies, primarily amine-based solvents, face challenges such as high energy requirements, volatility, and degradation, there is an urgent need for alternative materials that are both efficient and sustainable. Ionic liquids (ILs) and poly (ionic liquids) (PILs) have emerged as promising candidates due to their unique physicochemical properties, including negligible vapor pressure, high thermal and chemical stability, structural tunability, and strong CO2 affinity. This review provides a comprehensive overview of recent advancements in the design, synthesis, and application of ILs and PILs for CO2 capture. We examine the mechanisms of CO2 absorption in IL and PIL systems, analyze the structure-property relationships influencing capture performance, and compare their advantages and limitations relative to conventional solvents. Special attention is given to the role of functional groups, anion/cation selection, and polymeric architectures in enhancing CO2 uptake and reducing regeneration energy. Finally, the review highlights current challenges and future research directions for scaling up IL and PIL-based technologies in industrial carbon capture and sequestration systems.