Efficient Capture of Th(IV) and U(VI) by Radiation-Resistant Oxygen-Rich Ion Traps Based on a Metal-Organic Framework

Herein, based on a well-stabilized Ti-MOF (IEF-11), an oxygen-rich ion trap with synergy interaction of active atoms was proposed for the removal of Th(IV) and U(VI) from aqueous solutions. Due to the high coordination number of Ti and compact framework structure, IEF-11 has excellent resistance toward β-ray irradiation, even under 1000 kGy irradiation dosage. Meanwhile, owing to the special chelating effect of the oxygen-rich ion traps, the maximum adsorption amounts of IEF-11 for Th(IV) (pH = 3.0) and U(VI) (pH = 5.0) ions can reach 305.9 and 240.7 mg g^-1, and the separation coefficients exceed 200 for Th(IV)/Nd(III), Th(IV)/Sm(III), and Th(IV)/Eu(III) and 100 for U(VI)/Eu(III), U(VI)/La(III), and U(VI)/Sr(II). Moreover, IEF-11 shows fast adsorption kinetics with an equilibrium time of ∼100 min. The adsorption amount almost remains even after four adsorption-desorption cycles. Finally, experimental and theoretical calculations indicate that Th(IV) and U(VI) ions are anchored in the ion trap in the form of chemical bonds. Meanwhile, the circular pore trap (class I trap) than the long pore trap (class II trap) is considered to be the better adsorption site. We expect that our work will provide a new insight for constructing effective adsorbents for radioactive nuclides.