Cerium-based metal–organic-frameworks with ligand tuning of the microstructures for fluoride adsorption: linear and nonlinear kinetic and isotherm adsorption models

We present the synthesis and characterisation of three Ce-based metal–organic frameworks (Ce–MOFs) using fumaric acid (Fu), terephthalic acid (BDC), and trimesic acid (H 3 BTC) as linkers. The use of different linkers influenced the size of the MOF particles, surface area, crystallinity, and microporous structure. The successful implementation of Ce–Fu, Ce–BDC, and Ce–H 3 BTC MOFs for fluoride ion removal from wastewater was carried out, in which Ce–Fu MOFs exhibited a maximum adsorption capacity (AC) of 64.2 mg g −1 . The study also reveals that the use of ultrasound as a mediator for adsorption study over conventional method gives rapid adsorption rate, in which 85% of the fluoride uptake took place just in 10 min and achieved maximum AC in 30 min. The kinetics data were most accurately explained by the pseudo-second-order model (PSO). The existence of co-ions such as NO 3 − , Cl − , HCO 3 − , SO 4 2− , Br − , CO 3 2− , and PO 4 3− has a substantial effect on fluoride removal. The mechanism between the fluoride ions and the MOF surface took place via the electrostatic force and the ion exchange process, confirmed using X-ray photoelectron spectroscopy (XPS) and delsa nano. The material is sustained its relatively higher F − ions removal efficiency up to the five cycles. This research might help in the development of novel microporous Ce-based MOFs since it possesses a highly stable crystalline structure in water, suggesting a promising role in aqueous applications. Graphical Abstract