Enhanced adsorption of ketoprofen from water by the coordination defective UiO-66

In this study, acetic acid (HOAc) was applied to induce missing linker defects on UiO-66 via coordination competition strategy and its role on the outstanding adsorption capacity for ketoprofen (KTP) was investigated systematically. This strategy was proved to simultaneously modulate the defect sites and increase the pore size, pore volume, and surface area of the UiO-66. The missing linker defects constructed porous structure, which dramatically enhanced specific adsorption for KTP. Results showed that the surface area of UiO-66 possessed 27 % enhancement as defect sites increased (from 875.38 to 1439.86 m²/g) and exhibited good linearity (R² = 0.998) with adsorption capacity (from 645.5 to 1136.4 mg/g). The adsorption performance of UiO-66 on KTP was investigated on both kinetics and isotherms which were fit by the pseudo-second-order kinetic model and Langmuir model, respectively. According to the Arrhenius equation and Van't Hoff equation, the activation energy increased with missing linker defects and the adsorption is a spontaneous, exothermic and randomness-increasing process. Remarkably, the defective UiO-66 maintained high adsorption resilience across a broad pH range and demonstrated superior selectivity for KTP in the presence of competing ions and humic acid (HA). The results of characterization (FTIR, XPS) and DFT calculations indicated that the adsorption of KTP was primarily driven by chemisorption at the Lewis acid metal centers of UiO-66, accompanied by secondary interactions such as van der Waals forces and hydrogen bonding.