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

This study presents the synthesis of a perfluorinated Zr-based metal-organic cage (ZrT-1-F4) using microwaveassisted 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 assynthesized ZrT-1-F4 demonstrated exceptional fluoride ion adsorption performance across diverse environmental conditions, including varying pH and ion concentrations. Under optimal conditions (pH = 5, 25 degrees C, 100 ppm fluoride concentration), ZrT-1-F4 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-secondorder kinetic models, indicating a monolayer process. The primary driving forces for fluoride ion adsorption were identified as electrostatic interactions and strong F center dot center dot center dot H-O hydrogen bonds, as confirmed by DFT simulations and XPS analyses. Furthermore, ESI-MS confirmed the structural integrity of ZrT-1-F4 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.