Molecular regulation of metal-organic frameworks for rapid and efficient extraction of uranium from seawater

The development of novel metal-organic frameworks (MOFs) as solid adsorbents for rapid and efficient extraction of uranium from natural seawater is a long-term pursuit, yet remains challenging. In this work, we have prepared four two-dimensional (2D) vinylene-linked cyclic trinuclear units (CTUs) based MOFs. The metal nodes in the skeleton can be regulated, resulting in two Ag-CTU and two Cu-CTU-based MOFs with similar 2D hexagonal structures. These MOFs exhibit not only good stability in acid/base, γ-ray irradiation and natural seawater but also feature excellent anti-biofouling properties against five marine bacteria with inhibition rates as high as ∼99%. Interestingly, the alteration of Ag(I) to Cu(I) remarkably enhances the uranium sorption capacity due to the reduction of soluble U(VI) to insoluble U(IV) triggered by the chemical and photo-redox reaction of Cu-CTU. Due to the multiple functions, the Cu-CTU-based MOF delivers the best overall performance for uranium extraction from natural seawater with a high adsorption capacity of 7.96 mg g⁻¹ and adsorption rate of ∼1.00 mg g⁻¹ day⁻¹, which is much higher than most of reported representative solid adsorbents. Our work paves a new way for rationally designing synergistic MOFs with superior performance for extracting uranium from natural seawater.