POM Constructed from Super-Sodalite Cage with Extra-Large 24-Membered Channels: Effective Sorbent for Uranium Adsorption

A POMs-based sorbent functionalized by phosphate groups: H₃₃Na₁₄Mo^V₂₄Mo^VI₂(PO₄)₁₁O₇₃ has been successfully isolated under hydrothermal conditions. The cooperative assembly of the ring-shaped polyoxometalate structural building unit {P₄Mo₆} and MoO₄ tetrahedra linkers gives rise to an unprecedented supersodalite cage containing approximately spherical cavities with a 8.76 Å diameter. As POMs-based inorganic material, compound 1 was first applied as sorbent to adsorb U(VI) from aqueous solution, exhibiting good stability, high efficiency, and selectivity. The maximum sorption capacity reaches 325.9 mg g^-1, which may capture radionuclides through cooperative binding of the phosphate groups. The adsorbed U(VI) could be nearly drastically eluted when using 0.1 M Na₂CO₃ and the sorption capacity for U(VI) slightly decreased 10.16% through five successive sorption/desorption cycles. This work represents first application of POMs-based inorganic materials as sorbent to adsorb uranium from aqueous solution and provides a feasible approach for the entrapment and recovery of radionuclides.