Energetic Performances of “ZIF-71–Aqueous Solution” Systems: A Perfect Shock-Absorber with Water

Intrusion–extrusion experiments of water as well as electrolyte solutions (KCl 1 and 4 M) under high pressure were performed in metal–organic framework ZIF-71 (RHO-type structure) in order to study the performances of this system in energy absorption and storage. The experimental results reveal that “ZIF-71–water” system displays a perfect shock-absorber behavior, reproducible over several cycles. With this new studied system, the stored energy (25.5 J g–1) is almost doubled compared to that measured recently for “ZIF-8–water” system (13.3 J g–1) (SOD-type structure). When water is replaced by KCl aqueous solutions, a gain of intrusion pressure (74 and 96 MPa with KCl 1 and 4 M, respectively) is observed. However, for the highest salt concentration, the system evolves to a bumper behavior, and as confirmed by XRD analysis, the RHO-type structure collapses.