Recent techniques of hybrid ILs for CO2 capture, challenges, environmental and economic impact: Review study

The rising global demand to mitigate anthropogenic carbon dioxide emissions has intensified research into advanced separation technologies. Among these, ionic liquids (ILs) have emerged as promising materials for CO 2 capture due to their tunable structures, negligible vapor pressure, high thermal stability, and chemical design flexibility. This review summarizes recent developments in ILs and IL-hybrid systems for CO 2 separation, focusing on their molecular design, functionalization, hybridization strategies, adsorption mechanisms, and economic feasibility. Four generations of ILs have been developed, with task-specific ionic liquids (TSILs) showing significant potential for selective and reversible CO 2 capture through tailored functional groups such as amines, carboxylates, and carbonyls. These functionalities enhance chemical interactions via acid-base mechanisms and hydrogen bonding, leading to improved sorption performance. However, challenges such as high viscosity, synthesis complexity, and elevated production costs remain critical barriers to large-scale deployment. To overcome these limitations, hybridization approaches including IL blending with water, amines, or organic solvents, as well as immobilization on porous supports of silica, MOFs have been explored. These methods improve gas-liquid contact, lower regeneration energy, and increase stability while maintaining or enhancing CO 2 uptake. Economic analyses suggest that while laboratory-scale ILs are expensive, industrial-scale production and hybrid solvent systems can significantly reduce costs. Future research should focus on designing low-viscosity, cost-effective ILs, improving property databases, and scaling up hybrid systems. Ultimately, ILs represent a versatile platform with strong potential for integration into sustainable carbon capture technologies.