Absorption of mechanical energy via formation of ice nanotubes in zeolites.

Molecular dynamics simulations are carried out for a heterogeneous system composed of bulk water and pure-silica zeolites of the AFI type. My simulations show, for the first time, the spontaneous crystallization of water in hydrophobic zeolite channels by compression, while the water outside remains liquid. The formation of ice nanotubes results in a molecular bumper behavior in the absence of chemical reactions, although the mechanism has been explained by the appearance of silanol defects. In contrast, the same zeolite-water system exhibits a weak shock-absorber behavior at higher temperatures. My study shows that the phase transitions of confined water dramatically change its intrusion/extrusion behavior and alter the energetic performance by varying the temperature alone. The results offer a new perspective for a better design of hydrophobic nanoporous materials utilized with water.