Nonsteroidal anti-inflammatory pharmaceuticals are emerging organic micropollutants in surface water, groundwater, and wastewater, whose removal is very important yet challenging. As a new class of porous functional materials, metal-organic frameworks (MOFs) have attracted extensive attention for their adsorption applications. Here, we report that Zr(IV)-based MOFs (defective UiO-66, and MOF-808) have extraordinary adsorption ability to remove nonsteroidal anti-inflammatory pharmaceuticals from water. Excellent adsorption performances are obtained for UiO-66 and MOF-808, particularly for UiO-66, of which the adsorption capacities are the highest in a wide series of adsorptive materials previously reported. It is elucidated that the incomplete-coordinated cationic Zr in the cluster has high affinity for the anionic pharmaceutical (chemical adsorption) and that the adsorption interaction between the benzene ring of the pharmaceutical and MOF's ligand is involved to enhance or as an alternative to the adsorption interactions (π-π interaction). In particular, adsorption of ibuprofen, ketoprofen, naproxen, indomethacin, and furosemide by UiO-66 and MOF-808 and the synergetic effect of chemical adsorption and π-π interaction are outstanding, leading to extremely higher binding energies ( Ebind) and sorption abilities.
Keywords: MOF-808; MOFs; UiO-66; chemical adsorption; pharmaceuticals removal; π−π interaction.