High CO_(2) absorption capacity of metal-based ionic liquids: A molecular dynamics study

The absorption of CO_(2)is of importance in carbon capture,utilization,and storage technology for greenhouse gas control.In the present work,we clarified the mechanism of how metal-based ionic liquids (MBILs),Bmim[XCl_(n)]_(m)(X is the metal atom),enhance the CO_(2)absorption capacity of ILs via performing molecular dynamics simulations.The sparse hydrogen bond interaction network constructed by CO_(2)and MBILs was identified through the radial distribution function and interaction energy of CO_(2)-ion pairs,which increase the absorption capacity of CO_(2)in MBILs.Then,the dynamical properties including residence time and self-diffusion coefficient confirmed that MBILs could also promote the diffusion process of CO_(2)in ILs.That's to say,the MBILs can enhance the CO_(2)absorption capacity and the diffusive ability simultaneously.Based on the analysis of structural,energetic and dynamical properties,the CO_(2)absorption capacity of MBILs increases in the order Cl^-→[ZnCl_(4)]^(2-)→[CuCl_(4)]^(2-)→[CrCl_(4)]^-→[FeCl_(4)]^-,revealing the fact that the short metal–Cl bond length and small anion volume could facilitate the performance of CO_(2)absorbing process.These findings show that the metal–Cl bond length and effective volume of the anion can be the effective factors to regulate the CO_(2)absorption process,which can also shed light on the rational molecular design of MBILs for CO_(2)capture and other key chemical engineering processes,such as IL-based gas sensors,nano-electrical devices and so on.