Crystallographic Observation of Dynamic Gas Adsorption Sites and Thermal Expansion in a Breathable Fluorous Metal–Organic Framework

Playing accordion : Cooling a single crystal of a microporous fluorous metal–organic framework under ambient atmosphere leads to very large breathing upon gas adsorption, during which multiple N 2 molecules are filled into channels and cages (see picture). While the framework exhibits remarkable positive thermal expansion under vacuum, a gigantic apparent negative thermal expansion takes place when the crystal is exposed to N 2 at ambient pressure.