Dendritic bio-inspired multidentate coordination aerogels for efficient uranium adsorption

Selective extraction of uranium from seawater presents significant challenges due to the competing ions, bio-fouling and price. Inspired by the branching structure of plants, a multi-site synergistic adsorption strategy was proposed. Utilizing affordable and available sodium alginate (SA) and carboxymethyl chitosan (CMC) as the scaffold, and incorporating dendritic molecules, a phosphorylated multidentate coordination aerogel adsorbent (named CSPP) has been developed. Within hours CSPP achieved an impressive capacity of 723.4 mg g^-1, surpassing the performance of most standalone SA, CMCs, and phosphate-based materials. Additionally, CSPP demonstrates an outstanding selectivity (K_d = 4.0 × 10⁴) in natural seawater, along with excellent stability, resistance to microbial contamination, and affordability (∼$200/kg U). The adsorption reaction accords with the pseudo-second-order model and is a spontaneous endothermic reaction. Both experimental and theoretical computational simulations have revealed a perfect tetradentate chelation: PO delivers the initial electrostatic attraction, CO tightens the angle, and the crown ether locks the equatorial plane of UO₂²⁺. This bio-mimetic, multi-site blueprint redefines the economic frontier uranium adsorption from seawater, and illustrates the broad applicability of biomimetic design and multisite synergistic adsorption of valuable target ions.