Ce-doped MOF-801 composite sponge for high-efficiency removal of F⁻ from wastewater: Experimental investigation and performance enhancement mechanism

Fluoride-containing wastewater pollution poses a serious threat to the global environment. Adsorption represents the most widely employed defluoridation process. Among various adsorbents, metal-organic frameworks (MOFs) demonstrate considerable potential. However, current zirconium-based MOFs for fluoride removal face challenges such as high cost, low adsorption capacity, insufficient mechanistic understanding, and difficulties in reuse due to the lack of stable immobilization methods. Herein, a zirconium‑cerium MOF (denoted as Zr/Ce-M) was prepared by doping MOF-801 with the low-cost metal cerium. At an initial F⁻ concentration of 26 mg/L, its actual adsorption capacity reached 213 mg/g. This represents a 326% improvement compared to conventional MOF-801 and is 66% higher than the adsorbent with the highest known adsorption capacity.Further, zirconium/cerium MOF-based sponge (Zr/Ce-MS) was prepared via a simple method. Zr/Ce-MS exhibited exceptional loading stability under mechanical stress and solvent corrosion. Regeneration tests confirmed effective fluoride removal after eight cycles. Computational results revealed an upward shift in the d-band center of metals and enhanced electron-donating capability after Ce doping. Monodentate coordination (Zr-F and Ce-F) proved more stable than μ₂- or μ₃-bridging configurations. Strong hybridization occurred between Zr d/Ce d and F p orbitals, with Ce doping strengthening electron transfer from Zr to F⁻. The defluoridation mechanism of Zr/Ce-MS involves ion exchange, electrostatic interactions, hydrogen bonding, and Lewis acid–base complexation.This work provides new insights for developing fluoride adsorbents and mechanistic analysis.