Metal-organic nanocages enhance fluoride adsorption through the synergy of ternary amino cryptands and metal sites

The rapid development of the fluorine chemical industry has resulted in serious fluoride pollution in water sources and the cost-effective removal of fluoride remain a critical challenge. In this study, PTiO2@UiO-66-NH2, a nanocage material with ternary amino cryptands cavities and Ti/Zr dual-metal sites, was synthesized through a stepwise assembly process involving: (i) oxidative polymerization of aniline on TiO2 nanotubes, followed by (ii) in-situ solvothermal growth of UiO-66-NH2. The material exhibits a fluoride adsorption capacity of 143.66 mg/g (298.15 K, pH = 3), surpassing most reported adsorbents, and maintains >89% efficiency over 5 regeneration cycles. Structural characterization (TEM, XPS, FTIR) confirms the unique ternary amino cryptands formed by amino groups, while DFT calculations reveal that their self-adaptive electron dispersion effect reduces the energy barrier for fluoride adsorption on metal sites by 49% (from 4.36 eV to 2.23 eV), enabling synergistic enhancement. This work provides a new strategy for designing high-performance adsorbents through electronic-structure-driven active-site cooperation.