Structure, Dynamics and Thermodynamics of Intruded Electrolytes in ZIF-8

We report here the properties of LiCl aqueous solutions at various concentrations confined inside the pores of the ZIF-8 metal-organic framework, on the basis of classical molecular dynamics simulations. This system has been proposed for applications in the storage or dissipation of mechanical energy, using the liquid-phase intrusion of concentrated electrolytes in the hydrophobic framework. We describe the structure of the liquids and the influence of confinement, their dynamics, the mechanical properties of ZIF-8, and the impact of liquid intrusion on them. We show that the presence of the electrolyte has a moderate impact on the ZIF-8 framework whereas the presence of the ZIF-8 matrix strongly influences the behavior of the confined aqueous solution, affecting the overall properties of the system. We also computed the free energy profile for the entry of water molecules and ions into the nanopores, showing a difference between anions and cations.