Ultrahigh molybdenum adsorption capacity of hierarchical MXene@UiO-66 composites for potential application in the 99Mo/99mTc generator

To overcome the problem of insufficient molybdenum adsorption capacity of commercially utilized alumina in 99 Mo/ 99m Tc generator, UiO-66(Ce)@MXene composites as potential molybdenum adsorbents were successfully prepared via in-situ growth method in this work. The adsorption performance and adsorption mechanism were investigated. The results indicate that the UM3 possesses superlative adsorption behavior compared to the other two samples. The adsorption kinetics are well described by the quasi-second-order model and the adsorption reaches equilibrium within 30 min. The adsorption isotherm can be well fitted with the Langmuir model, displaying the maximum molybdenum adsorption capacity of 833 mg/g at pH 3, superior to other reported adsorbents. The adsorption capacity manifests that polymolybdates are captured by the hydroxyl groups on MXene through hydrogen bonds. The monomolybdates can diffuse into micropores and are adsorbed on adsorption sites, e.g. missing-linker defects and Ce-OH groups. Consequently, the constructed hierarchical frameworks promote molybdenum adsorption and increase adsorption capacity significantly. The unrivalled adsorption performance of UiO-66(Ce)@MXene composites as molybdenum adsorbents have promising potential for the application in 99 Mo/ 99m Tc generator.