Assessment of the energetic performances of various ZIFs with SOD or RHO topology using high pressure water intrusion-extrusion experiments

The energetic performances of seven SOD or RHO-topology ZIFs, with zinc or cobalt metal cation (ZIF-8, ZIF-90, Zn(dcim)(2)-SALE, ZIF-67, ZIF-7, ZIF-71, ZIF-11) were evaluated using water intrusion-extrusion under high pressure. The relationship between the structural parameters (in particular the pore system SOD or RHO, the type of linker, the metal cation nature) and the intrusion pressure was studied to better understand the mechanism of water intrusion and the energetic behaviour for a given ZIF crystal type. ZIF-8-water, ZIF-67-water and ZIF-71-water systems display a shock-absorber behaviour. A very important hysteresis for ZIF-71 and a slight difference between the first intrusion-extrusion cycle and the following ones for ZIF-67 were observed. ZIF-8 (SOD) with zinc cation and ZIF-67 (SOD) with cobalt cation display similar intrusion pressures. For ZIF-71 (RHO) material, the stored energy is more than doubled compared to ZIF-8 and ZIF-67 (SOD). This might be related to the topology. No water intrusion was observed after three water intrusion-extrusion cycles, for the ZIF-90 (SOD), Zn(dcim) 2-SALE (SOD), ZIF-7 (SOD) and ZIF-11 (RHO) materials. This is explained in term of hydrophilic feature as well as topology and linker effects.