Hydroxyl-Mediated Adsorption Site Distribution on Titanium Dioxide@Covalent Organic Framework and Enhanced Selective...

This work designs a titanium dioxide@covalent organic framework composite material (TiO₂-COF), which optimizes the distribution of lead adsorption sites by adjusting the position of hydroxyl groups in the COF, thereby enhancing the separation efficiency of trace Pb²⁺ ions. The composite material integrates the advantages of metal oxides and porous materials, optimizing the separation performance of Pb²⁺ ions through a synergistic enhancement effect. Additionally, its multi-interface structural characteristics provide the material with multidimensional selectivity, resulting in a highly selective separation material. In selectivity experiments, the material demonstrated high adsorption selectivity for Pb²⁺ ions compared to several other metal ions. Thermodynamic and kinetic simulation results prove that the adsorption of Pb²⁺ ions by TiO₂-COF conforms to the pseudo-second-order kinetics and the Langmuir adsorption model. After multiple cycles of use, the material still maintains high adsorption efficiency, demonstrating its potential clean and green application value in the highly selective separation of metal pollutants. The constructed material was used for the separation and preconcentration of Pb²⁺ ions, establishing a detection system for trace Pb²⁺ ions. The detection limit of the method is 0.073 µg L^-1 (3σ/K, n = 9), with precision ranging from 0.55% to 11.7% (n = 11), and a linear range of 0.2-5 µg L^-1, exhibiting strong anti-interference capability. The constructed method achieves the determination of lead ions in real samples, with recoveries ranging from 95% to 103%. Moreover, the standard material GBW08607 was analyzed through the constructed system, and the t-test shows that the calculated t-value is 2.01, which is less than the tabulated t-value of 2.57 (n = 6), proving the reliability of the method. It provides a potential alternative material for the separation and analysis of other environmental pollutants.