Dynamics of Water Molecules in a 3-Fold Interpenetrated Hydrogen-Bonded Organic Framework Based on Tetrakis(4-pyridyl)methane

Abstract

The 3-fold interpenetration of the β-quartz-type hydrogen-bonded organic framework (HOF) from the dication salts of tetrakis(4-pyridyl)methane develops a host–guest system featuring flexibility and durability in accordance with the state change of guest molecules. Water molecules are incorporated into HOF and form a one-dimensional helical-shaped molecular chain in nanopores. X-ray crystallographic analysis and the dielectric dispersion in the impedance measurements revealed that guest water molecules behave dynamically and show a concerted freezing process to produce water pentamers at 100 K. Structural changes in the host framework mediate interactions between guest water molecules within and between the nanopores through the weak host–guest interactions based on hydrogen-bonding interaction. In addition, the triangular arrangement of nanopores gives rise to the topologically unsettled guest molecules in the freezing process.