Microwave-assisted synthesis of perfluorinated Zr-based metal-organic cage for defluoridation of water

• High-purity ZrT-1-F 4 was synthesized by microwave-assisted synthesis method. • Zirconium-based organic cages were first used as adsorbents for the adsorptive removal of fluoride ions. • The maximum adsorption capacity of ZrT-1-F 4 for fluoride ions can reach 97.96 mg g -1 . • DFT simulations indicated that fluoride ion adsorption was due to electrostatic and hydrogen bonding interactions. This study presents the synthesis of a perfluorinated Zr-based metal-organic cage (ZrT-1-F 4 ) using microwave-assisted techniques, followed by an in-depth investigation of its adsorption capabilities for fluoride ions in aqueous solutions. The incorporation of fluorine functional groups improved the hydrophobic nature. The as-synthesized ZrT-1-F 4 demonstrated exceptional fluoride ion adsorption performance across diverse environmental conditions, including varying pH and ion concentrations. Under optimal conditions (pH = 5, 25 °C, 100 ppm fluoride concentration), ZrT-1-F 4 exhibited outstanding fluoride ion adsorption, with a maximum capacity of 97.96 mg g -1 . The experimental data were well fitted to the Langmuir isotherm model and pseudo-second-order kinetic models, indicating a monolayer process. The primary driving forces for fluoride ion adsorption were identified as electrostatic interactions and strong F···H O hydrogen bonds, as confirmed by DFT simulations and XPS analyses. Furthermore, ESI-MS confirmed the structural integrity of ZrT-1-F 4 before and after adsorption. This work marks the first application of Zr-based metal-organic cages (Zr-MOCs) to fluoride ion adsorption, achieving promising results and paving the way for further environmental applications of Zr-MOCs. The perfluorinated Zr-MOC was synthesized using microwave-assisted method, exhibiting good adsorption performance towards fluoride ions.