Synthesis of Magnetic Al-Based Metal-Organic Frameworks (MIL-53@Fe3O4) for perfluorooctanoic acid capture from water

Aluminum-based metal-organic frameworks (Al-MOFs) were grown on micrometric magnetite (Fe3O4) particles using green solvothermal and solvent-free methods. The resulting magnetic micrometric Fe3O4 particles coated with the Al-MOFs (Al-MOF@Fe3O4) were evaluated for the removal of perfluorooctanoic acid (PFOA) from contaminated water. Three organic ligands with different affinities, ranging from hydrophilic to fluorophilic, were investigated: 2-amino-terephthalic acid (NH₂-BDC), terephthalic acid (H₂BDC) and tetrafluoro-terephthalic acid (F₄-BDC). PXRD, SEM-EDS and TEM confirmed the formation of a MOF-based crystalline coating on Fe3O4 microparticles, FTIR-ATR assessed the presence of the corresponding functional groups and the Al-MOF@Fe3O4 surface areas were determined by BET analyses. In PFOA remediation, the ethanol-solvated MIL-53(Al)@Fe₃O₄ and the solvent-free fluorinated F4-MIL53(Al)@Fe3O4 achieved removal efficiencies of 99.8% and 95.7%, respectively. Moreover, MIL-53(Al)@Fe3O4 showed a regeneration efficiency equal to 82.9%. These results demonstrated that solvents and ligands influenced synthesis, adsorption efficiency and reusability of Al-MOF@Fe3O4 hybrid systems, outlining their potential as promising materials for PFAS remediation.