Nanospace Decoration with Uranyl-Specific “Hooks” for Selective Uranium Extraction from Seawater with Ultrahigh Enrichment Index

Mining
uranium from
seawater is highly desirable for sustaining
the increasing demand for nuclear fuel; however, access to this unparalleled
reserve has been limited by competitive adsorption of a wide variety
of concentrated competitors, especially vanadium. Herein, we report
the creation of a series of uranyl-specific “hooks”
and the decoration of them into the nanospace of porous organic polymers
to afford uranium nanotraps for seawater uranium extraction. Manipulating
the relative distances and angles of amidoxime moieties in the ligands
enabled the creation of uranyl-specific “hooks” that
feature ultrahigh affinity and selective sequestration of uranium
with a distribution coefficient threefold higher compared to that
of vanadium, overcoming the long-term challenge of the competing adsorption
of vanadium for uranium extraction from seawater. The optimized uranium
nanotrap (2.5 mg) can extract more than one-third of the uranium in
seawater (5 gallons), affording an enrichment index of 3836 and thus
presenting a new benchmark for uranium adsorbent. Moreover, with improved
selectivity, the uranium nanotraps could be regenerated using a mild
base treatment. The synergistic combination of experimental and theoretical
analyses in this study provides a mechanistic approach for optimizing
the selectivity of chelators toward analytes of interest.