Three Mechanisms in One Material: Uranium Capture by a Polyoxometalate-Organic Framework through Combined...

The design and synthesis of uranium sorbent materials with high uptake efficiency, capacity and selectivity, as well as excellent hydrolytic stability and radiation resistance remains a challenge. Herein, a polyoxometalate (POM)-organic framework material (SCU-19) with a rare inclined polycatenation structure was designed, synthesized through a solvothermal method, and tested for uranium separation. Under dark conditions, SCU-19 can efficiently capture uranium through ligand complexation using its exposed oxo atoms and partial chemical reduction from U^VI to U^IV by the low-valent Mo atoms in the POM. An additional U^VI photocatalytic reduction mechanism can occur under visible light irradiation, leading to a higher uranium removal without saturation and faster sorption kinetics. SCU-19 is the only uranium sorbent material with three distinct sorption mechanisms, as further demonstrated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis.