Solvent-free synthesis of a new perfluorinated MIL-53(Al) with a temperature-induced breathing effect

We report on the solvent-free synthesis of the perfluorinated analogue of the well-known breathing metal-organic framework MIL-53(Al), i.e., F-4-MIL-53(Al), featuring tetrafluoroterephthalic acid as linker. The crystal structure was solved and refined from powder X-ray diffraction data and confirmed to be isoreticular with MIL-53(Al). As already reported for the MIL-53(Al) analogue, F-4-MIL-53(Al) displays a peculiar breathing effect solely induced by the temperature; however, in the latter case the transition occurs with almost no hysteresis and fast kinetics. This unique behavior is reported here for the first time and experimentally demonstrated using differential scanning calorimetry and variable temperature X-ray diffraction.