Fig. 6: Behaviors of ZIOS in aqueous environment via molecular dynamics simulation and PXRD.

a Water penetrates into ZIOS within nanoseconds, based on a flat two-dimensional channel simulation (4 × 4 × 8 ZIOS unit cells were originally placed with periodic 3-nm water channels). b, c For a periodic-boundary condition simulation box having 2 × 2 × 3 ZIOS unit cells and equilibrated state, simulations indicate clear lattice expansion when ZIOS is exposed to water and subsequent lattice contraction as water is removed. Simulations were performed separately with differing numbers of water molecules per ZIOS unit cell. d Comparison of a simulated ZIOS powder pattern from Rietveld refinement of synchrotron single-crystal X-ray diffraction data (red) with PXRD patterns of ZIOS obtained 2 h after synthesis (black), 16 h after synthesis (gray), and after being immersed in water for 52 days (blue). Notably, the powder pattern collected following extended water exposure is largely unchanged from the simulated pattern. e Water transport in ZIOS through hopping movement shown by histograms of spatial displacement of water molecules from their original positions (inset: squared displacement of independent water molecules with time). A representative case of ten water molecules per ZIOS unit cell is presented. f Radial distribution function showing the interaction of water molecules with the critical atoms in ZIOS unit via hydrogen bonds. The case of five water molecules per ZIOS unit cell was used in this analysis. The most active hydrogen-bond acceptor sites are highlighted.