Formation of a nanometer-thick water layer at high humidity on a dynamic crystalline material composed of multi-interactive molecules.

Crystalline powders self-assembled from interactive discrete molecules reversibly transformed from a porous structure to a 2D one with a nanometer-thick H2O layer by hydration/dehydration. Multi-point weak intermolecular interactions contributed to maintenance of each phase. This structure transformation induced a humidity-dependent ion conductivity change from insulator to 3.4 × 10(-3) S cm(-1).