Versatile Energetic Behavior of ZIF-8 upon High Pressure Intrusion–Extrusion of Aqueous Electrolyte Solutions

Abstract

Metal–organic materials (MOFs) constitute very attractive materials for storage, separation, catalysis, and drug delivery because of their crystalline hybrid organic–inorganic structures and their large porous volume. Here, we report the energetic behavior, in term of storage/restoration of mechanical energy, of ZIF-8 upon high pressure intrusion–extrusion of aqueous KCl, LiCl, and NaCl solutions of variable concentration. Comparison with the energetic performances of the “ZIF-8–water” system is performed. Whatever the nature of the electrolyte (KCl, LiCl, NaCl), an increase of the intrusion pressures and thereby of the stored energy are observed with the increasing of salt concentration. However, the three studied systems differ, at least for the highest concentrations, by behaving as a shock-absorber for KCl and as a bumper for NaCl and LiCl. A combination of several characterization techniques used before and after intrusion–extrusion experiments, i.e., X-ray diffraction, solid state NMR, and N2 adsorption–desorption experiments, allows us to establish that the ZIF-8 network is preserved after such a treatment.