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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Charged Soft Matter, Polyelectrolytes and Ionic Liquids I

CPP 17.10: Vortrag

Dienstag, 19. März 2024, 12:15–12:30, H 0107

Dynamics of ions in confinement: tuning the nanoporous metal-organic framework host for ionic liquids — •Anemar Bruno Kanj, Rupal Verma, Micaela Vazquez, Zejun Zhang, Abhinav Chandresh, Modan Liu, Wolfgang Wenzel, and Lars Heinke — Karlsruher Institut für Technologie, Karlsruhe, Germany.

Room-temperature ionic liquids (ILs) are molten organic salts. Studying their dynamic properties under nanoporous confinement, such as in metal-organic frameworks (MOFs), is a crucial aspect of fundamental science and can enhance applications like batteries and super-capacitors. Here, we utilize experiments based on MOF thin films and impedance spectroscopy, combined with molecular dynamics simulations. This provides unique insights into their molecular properties: At low IL loadings, the IL cations and anions drift along the electric field in opposite direction. However, at higher concentrations, the ions in the pores mutually obstruct the pathways, leading to a decrease in mobility. This pore blockage results in non-uniform IL density and ion bunching in obstructed pores. By adding lithium in IL, the presence of lithium prevents the formation of Li-anion dimers and the pore blockage and the collapse in conductivity at elevated IL concentrations. The pore size of the MOF confinement also significantly impacts the ion mobility. Smaller pores hinder passage and cause concentration-dependent mobility, while larger pores have minimal interference. We show that the cut-off pore window size corresponds to the diameter of the IL cation-anion dimer. Therefore, optimizing pore size is critical for achieving highly mobile nanoconfined ILs.

Keywords: MOF; Ionic Liquid; mobility; confinement; nano porous