Abstract
Nature can efficiently recognize specific ions by exerting second-sphere interactions onto well-folded protein scaffolds. However, a considerable challenge remains to artificially manipulate such affinity, while being cost-effective in managing immense amounts of water samples. Here, we propose an effective approach to regulate uranyl capture performance by creating bio-inspired nano-traps, illustrated by constructing chelating moieties into porous frameworks, where the binding motif’s coordinative interaction towards uranyl is enhanced by introducing an assistant group, reminiscent of biological systems. Representatively, the porous framework bearing 2-aminobenzamidoxime is exceptional in sequestering high uranium concentrations with sufficient capacities (530 mg g−1) and trace quantities, including uranium in real seawater (4.36 mg g−1, triple the benchmark). Using a combination of spectroscopic, crystallographic, and theory calculation studies, it is revealed that the amino substituent assists in lowering the charge on uranyl in the complex and serves as a hydrogen bond acceptor, boosting the overall uranyl affinity of amidoxime.
Highlights
Nature can efficiently recognize specific ions by exerting second-sphere interactions onto well-folded protein scaffolds
Taking the abovementioned into account, we demonstrate a promising approach to meet these challenges by creating uranium nano-traps that integrate the metrics of nature and artificial systems with the following features: a bio-inspired uranium coordination environment where the de novo introduced assistant group reinforces the interaction between the chelating site and uranyl, enhancing the affinity
To enhance the affinity of chelating groups to uranyl ions, an amino group was de novo introduced to improve coordinative binding interactions by providing a secondary coordination sphere, which alters the electron density of the complex to lower the overall charge on uranyl and provides an additional site allowing a hydrogen bond to align uranyl species in a favorable coordination mode
Summary
Nature can efficiently recognize specific ions by exerting second-sphere interactions onto well-folded protein scaffolds. Such uranium nano-traps can be targeted by constructing judiciously designed bio-inspired chelating systems into porous organic polymers (POPs) due to their exceptional chemical stability as well as flexible molecular design and tunable pore structures[25,26,27,28,29,30] These features provide excellent opportunities to introduce hierarchical porosity and offer a high density of the chelating moieties in the resultant adsorbent materials to achieve both efficient binding kinetics and high adsorption capacities to meet the challenges posed by the enormous volumes of wastewater or seawater[2,3]
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