No abstract

UiO-66 with crystal size ranging from hundreds of nanometers to a few micrometers and with morphologies of cube and cuboctahedron were synthesized. Crystal size and morphology varied with the additive amount of hydrofluoric acid and the concentration of reactants (ZrCl 4 and H 2 BDC) during solvothermal synthesis. According to energy dispersive spectrometry (EDS) and 19 F MAS NMR measurements, fluorine ions directly bonded to Zr in SBUs (secondary building units) in the MOF framework due to their strongest electronegativity. The bonding of fluorine ions and Zr not only compensated the charge imbalance of the framework caused by missing linkers but also competed with the linkers to coordinate with Zr metal centers, thereby controlling the processes of nucleation and growth of UiO-66 crystals. The samples were further characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and Ar sorption isotherms, showing that the introduction of fluorine enhanced the thermostability and porosity of UiO-66.

No abstract