Single-crystal and Humidity-controlled Powder Diffraction Study of the Breathing Effect in a Metal-organic Framework Upon Water Adsorption/desorption

Herein we report a study on water adsorption/desorption-triggered single-crystal to single-crystal transformations in a MOF, by single-crystal and humidity-controlled powder X-ray diffraction and water-sorption measurements. We identified a gate-opening effect at a relative humidity of 85% upon water adsorption, and a gate-closure effect at a relative humidity of 55 to 77% upon water desorption. This reversible breathing effect between the "open" and the "closed" structures of the MOF involves the cleavage and formation of several coordination bonds.