Cerium-Based Nanoporous Metal–Organic Frameworks Incorporated with Different Metals for the Remediation of Fluoride Ions from Water

The adsorption capacity (AC) of the material can be significantly enhanced by the composite synergy between various metals, which in turn modifies the morphology, structure, and functional groups of the material. In this view, the nanoporous bimetal metal–organic frameworks (MOFs) using metals (Ce, Fe, Al, and La), namely, Ce@Fe1:1, Ce@Al1:1, and Ce@La1:1, were synthesized via a one-pot method. The nanoporous bimetal MOFs applied to remove F– ions from drinking water followed the order of Ce@Fe1:1 > Ce@Al1:1 > Ce@La1:1. Based on the above findings, Ce@Fe1:1 was further synthesized using cerium and iron at different molar ratios to optimize the best possible compositions, namely, Ce-Fu, Ce@Fe2:1, Ce@Fe1:1, Ce@Fe1:2, and Fe-Fu. These nanoporous bimetal MOF composites were applied to remediate the F– ion from wastewater and Ce@Fe1:1 exhibited the maximum AC of 84.4 mg g–1 at 288 K. It is worth mentioning that the utilization of ultrasonication as a mediator for the adsorption study over the conventional method gives excellent relaxation in time as it enhances the reaction kinetics. As a result, the study demonstrated rapid adsorption kinetics, which follows the pseudo-second-order (PSO) model. Moreover, coexisting ions such as NO3–, Cl–, HCO3–, and SO42– had less effect on the adsorption of fluoride. The adsorption mechanism of Ce@Fe1:1 bimetal MOFs supports the electrostatic attraction and ligand exchange processes, which were confirmed using characterization instruments, such as X-ray photoelectron spectroscopy (XPS) and zeta potential.