DFT Study on Potassium Benzene Disulfonamide and Potassium Phthalimide Ionic Liquid Based Carbon Dioxide Absorption

This groundbreaking research rigorously investigated the CO₂ absorption potential of two potassium-based ionic liquids (ILs), namely potassium benzene disulfonamide [C₆H₄KNS₂O₄] and potassium phthalimide [C₈H₄KNO₂]. Driven by the urgent need for effective carbon capture technologies to combat climate change stemming from fossil fuel combustion, this study employed sophisticated Density Functional Theory (DFT) calculations using the M062X/6-31+G(d,p) method. The computational approach encompassed comprehensive geometry optimization, in-depth molecular interaction analyses, precise binding energy assessments, insightful Natural Bond Orbital (NBO) analysis, and a thorough evaluation of solvent effects. The findings unequivocally demonstrate that both ILs exhibit tangible interactions with CO₂, with binding energies ranging from -3.108 to -0.232 kcal/mol for C₆H₄KNS₂O₄ and -3.475 to -0.219 kcal/mol for C₈H₄KNO₂. These energies strongly suggest the viability of these ILs for CO₂ capture applications, potentially requiring minimal energy for regeneration. Crucially, the research established that potassium benzene disulfonamide [C₆H₄KNS₂O₄] displays superior CO₂ capture efficacy compared to potassium phthalimide [C₈H₄KNO₂]. This conclusion is robustly supported by compelling thermochemical and molecular interaction data. NBO analysis further elucidated that CO₂ interaction induces alterations in the IL geometry and facilitates charge transfer between the interacting species. Moreover, studies on cation-anion interactions revealed a stronger association between C₆H₄KNS₂O₄ and the potassium cation (K⁺). Investigation of isolated anion interactions with CO₂ echoed the preference for [C₆H₄NS₂O₄]. While solvent effects influenced thermochemical properties, they did not fundamentally alter the geometry of the anion-CO₂ complexes. In conclusion, the computational evidence unequivocally indicates the formation of stable complexes between the investigated IL pairs and CO₂ molecules. Most significantly, this study firmly establishes that C₆H₄KNS₂O₄ is a more promising candidate for efficient CO₂ absorption, offering a pathway towards the development of advanced and effective CO₂ capture technologies.