Valence modulation stimulates ligand vacancies to construct unsaturated Ce sites for robust low-concentration defluorination via capacitive deionization

Research into technologies with excellent fluoride removal properties is an effective strategy for cleaning water resources and safeguarding human health. We herein designed a Ce/N co-modified supramolecular porous carbon material (CePNC) electrode for capacitive deionization defluorination based on the chemical properties of metallic electron structure. In this work, we successfully modulated the Ce(III)/Ce(IV) ratio and left more unsaturated coordination numbers in the material. The formed massive coordination vacancies provided additional active centers, which significantly enhanced the fluoride ion electrosorption enrichment efficiency and capacity. In addition, the stable multidimensional laminar carbon framework ensured smooth ion transport channels and favorable activity of the electrical double-layer. Multiple synergistic effects endowed the CePNC electrode an amazing low-concentration electrosorption capacity for defluorination, with an electrosorption capacity of 23.43 mg g−1 for treating 10 mg L−1 F− solution at 1.2 V, which exceeded most of the reported records. The effluent concentration was as low as 0.93 mg L−1, which met all types of water quality standards and provided the possibility for practical application of CePNC. This research provides a new thought for efficient defluorination by electrosorption and demonstrates a profound understanding of it.