Metal-organic frameworks cavity size effect on the extraction of organic pollutants.

• UiO-66 and UiO-67 MOFs have been used for the extraction of pollutants from aqueous solution. • Both materials present a high sorption capacity to remove the pollutants. • Sorption isotherms were obtained and revealed different mechanisms of sorption depending of the cavity size. Zirconium Metal-organic frameworks (MOFs, UiO-66 and UiO-67) have been used for the removal from aqueous solutions of persistent fluorinated pollutants, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The two isostructural materials differ in cavity size, defined by the ligand, bdc (benzene-dicarboxylic acid) or bpdc (biphenyl-dicarboxylic acid) for UiO-66 and UiO-67 respectively. Both materials enable efficient sorption of PFOA and PFOS. Sorption kinetics and isotherms have been experimentally determined, and thermodynamic parameters ΔH°, ΔS° and ΔG° have been determined. UiO-67 shows higher sorption capacities (up to 743 mg·g−1 for PFOA and 585 mg·g−1 for PFOS) compared to these of UiO-66 (388 and 160 mg·g−1 for the sorption of PFOA and PFOS respectively) with a change in the sorption mechanism. [ABSTRACT FROM AUTHOR]