Rationally Tailoring Pore and Surface Properties of Metal-Organic Frameworks for Boosting Adsorption of Dy³

The adsorption and recovery of dysprosium ions (Dy³⁺) from industrial wastewater are necessary but still challenging. Herein, we constructed a series of defect-containing metal-organic frameworks (MOFs) [UiO-66-(COOH)₂] using sodium benzoate (BCNa) as a modulator. Upon the formation of defects, the porosity and surface charge properties of the MOFs were improved, leading to a higher utilization ratio of active groups and higher adsorption capacities for Dy³⁺. The synthesized UiO-66-(COOH)₂-B10 with an optimal addition of BCNa exhibited a superior adsorption capacity of 150.6 mg g^-1. Fast adsorption occurred at ∼5 min, and equilibrium was reached at ∼60 min. Higher pH and temperature were found to be beneficial for boosting Dy³⁺ adsorption, and selective adsorption over other metal ions was achieved in a multicomponent solution. Further, FTIR spectroscopy and XPS investigations indicate that free carboxyl contributes to the capture of Dy³⁺. Thus, this work provides a promising strategy to enhance the utilization ratio of active groups and further adsorption performance.