A comparative study of perfluorinated and non-fluorinated UiO-67 in gas adsorption

Metal–organic frameworks (MOFs) are perspective materials for application in gas storage, separation and purification. The perfluorination of organic linker is expected to change significantly the surface properties of a MOF and therefore, the adsorption behaviour due to small size, high electronegativity and polarizing ability of fluorine atoms. To reveal the effect of extensive linker fluorination on the properties of MOF, we have developed new method of synthesis of $${\hbox {Zr}}_{6}$$ MOF based on perfluorinated biphenyl-4,4 $$'$$ -dicarboxylate of UiO-67 structure denoted as UiO-67-F8. $${\hbox {N}}_{2}$$ adsorption at 77 K confirms that UiO-67-F8 is a microporous solid with the BET surface area of $$1629\,{\hbox {m}}^{2}\,{\hbox {g}}^{-1}$$ which is the best value for perfluorinated MOFs. Extensive investigations of properties of UiO-67-F8 reveal that hydrophobicity and hydrolytic stability are similar to the parent UiO-67. The low-pressure gas adsorption gravimetric uptakes ( $${\hbox {N}}_{2},$$ $${\hbox {CO}}_{2},$$ $${\hbox {CH}}_{4},$$ $${\hbox {C}}_{2}$$ -hydrocarbons) at 273 and 298 K are slightly lower for UiO-67-F8 due to larger density and lower pore volume. The results obtained show that the difference in IAST selectivity factors for UiO-67-F8 and UiO-67 are negligible and both non-fluorinated and perfluorinated surfaces are almost identical for adsorption of the most frequently studied gases.