Water sandwiched by a pair of aromatic rings in a proton-conducting metal-organic framework

The interactions between water molecules and aromatic rings are known to be common and important in physics, chemistry and life sciences. Benzene-water complexes are the main prototype systems for O-H center dot center dot center dot pi and lone-pair (lp)center dot center dot center dot pi interactions in theoretical research, however solid state examples are very rare. Here, the solid state example of water sandwiched by a pair of aromatic rings is observed in a silver-melli-tate framework, where lp center dot center dot center dot pi and O-H center dot center dot center dot pi interactions coexist. The coexistence of these two interactions has been further verified by theoretical calculations. In addition, ammonium ions and water molecules as proton sources, and strongly H-bonded nets as the pathway of proton transport, make the reported MOFs (metal-organic frameworks) exhibit distinct proton conduction.