Tailoring the pore environment of Zr-based metal-organic frameworks: Synergistic effects of pore expansion and functional groups on the adsorption of selected pharmaceuticals

Pharmaceutical residues occur widely in aquatic environments, making high-performance adsorbents essential for selectively capturing diverse pollutants. This study applied pore-structure design and functionalization strategies to overcome the limitations inherent in the zirconium-based metal–organic framework UiO-66. By extending the organic linker from 1,4-benzenedicarboxylate to 4,4′-biphenyldicarboxylate, we synthesized UiO-67 with a significantly enlarged pore size, and further prepared an amino-functionalized analog, UiO-67-NH 2 . The adsorption behavior of six pharmaceuticals with distinct charge characteristics, classified as positively charged (propranolol and verapamil), neutral (antipyrine and 17α-ethynylestradiol), and negatively charged (ketoprofen and naproxen), was systematically evaluated. Pore expansion markedly improved the access of bulky drug molecules to the internal active sites, and both expanded frameworks exhibited much higher adsorption capacities than pristine UiO-66 for all tested compounds. UiO-67 achieved excellent capacity for 17α-ethynylestradiol through π–π stacking and hydrophobic interactions provided by the biphenyl skeleton, whereas UiO-67-NH 2 showed enhanced affinity for anionic naproxen through electrostatic interactions and hydrogen bonding from the introduced amino groups. Mechanisms were elucidated by integrating kinetics, isotherm modeling, pH effect, regeneration, and physicochemical analysis. These results demonstrate that combining pore expansion with functional group introduction offers a complementary, rational strategy for designing porous adsorbents to control pharmaceutical contaminants in water.