Poly(ionic liquids-acrylic acid)-modified MIL-101(Cr) metal−organic frameworks: Preparation and efficient adsorption of europium☆

A novel composite material, Poly(IL-AA)@MIL-101(Cr), combining metal-organic framework, polymeric ionic liquid and acrylic acid, was synthesized for the selective and efficient adsorption of rare earths europium(III) (Eu 3+ ). Characterization of the materials was carried out using techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET). The results demonstrate successful incorporation of the polymeric ionic liquid onto the material surface while preserving the crystal structure and morphology of MIL-101(Cr). Adsorption experiments were conducted to explore parameters including solution pH, initial Eu 3+ concentration, and duration, with comprehensive analyses of adsorption kinetics, isotherms, and mechanisms. Findings reveal that Poly(IL1-AA)@MIL-101(Cr), Poly(IL3-AA)@MIL-101(Cr), and Poly(IL5-AA)@MIL-101(Cr) achieve adsorption equilibrium for Eu 3+ at approximately 9 h with an equilibrium pH of 6.2. The adsorption of Eu 3+ predominantly follows a pseudo-second-order kinetic model and Langmuir isotherm adsorption model. Moreover, the prepared composite material exhibits superior adsorption selectivity for Eu 3+ over other metal ions in the mixture (K + , Mg 2+ , Ni 2+ , Co 2+ , Zn 2+ , La 3+ , and Nd 3+ ). Even after five adsorption-desorption cycles, the composite material maintains satisfactory adsorption performance.