Moderate Carbonization and Nanoconfinement Engineering for High-Performance Fluoride Electrosorption in UiO-66(Ce) Derivatives

Efficient and selective removal of fluoride from water remains a critical challenge in environmental remediation. In this work, we report a thermally modulated strategy to enhance the electrosorption performance of cerium-based metal–organic frameworks (UiO-66(Ce)) for fluoride removal. Rather than complete carbonization, controlled partial carbonization at 400 °C was found to be optimal, inducing the in situ formation of well-dispersed CeO₂ nanoparticles and the development of interconnected mesoporous channels. The evolution of the pore structure with different thermal treatment temperatures was comprehensively characterized by N₂ adsorption–desorption analysis and high-resolution transmission electron microscopy (HRTEM). This approach effectively balances electrical conductivity and active site availability, leveraging a nanoconfinement effect that restricts CeO₂ aggregation, preserves active sites, and facilitates efficient ion transport. The optimized UiO-66(Ce)-400 °C material exhibits a high electrosorption capacity of 73.7 mg·g^–1, rapid kinetics, and strong fluoride selectivity in the presence of competing anions. Finite element simulations and electrochemical analyses confirm that the synergy between enhanced mesoporosity, conductivity, and active site accessibility drives superior performance. Furthermore, the electrode demonstrates excellent regeneration and stability over five cycles. This study presents a versatile and scalable approach for engineering MOF-derived materials, offering valuable insights into the design of next-generation electrosorption systems for water treatment.