Cerium-based metal-organic-frameworks with ligand tuning of the microstructures for fluoride adsorption: linear and...

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 (H₃BTC) 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-H₃BTC 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 NO₃^-, Cl^-, HCO₃^-, SO₄^2-, Br^-, CO₃^2-, and PO₄^3- 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.