Designing Polyethyleneimine-Based Electrospun Fibers via Hydrogen Bonding Reconstruction for Enhanced Uranium...

Polymer fibers that have the most industrial potential for uranium enrichment in seawater suffer from low adsorption site utilization because the polymer chains are often entangled due to intra-molecular interactions. Herein, a branched-linear intertwining electrospun fiber (PAN-bPEI-T/PVA) is obtained by co-grafting hyperbranched polyethyleneimine (bPEI) and linear triethylenetetramine (TEPA) for harvesting uranium from seawater. The fiber features a dendritic topology structure with a high density of distributed amino functional groups, which provide extensive pathways for uranium transport and contact. Meanwhile, the linear TEPA modulates the hydrogen bonding network by converting the strong intramolecular hydrogen bonds in bPEI into intermolecular hydrogen bonds, thereby enhancing the permeability and exposing more active sites. Compared to conventional bPEI polymer, the PAN-bPEI-T/PVA demonstrates higher accessibility and utilization of sites, achieving a capacity up to 806.4 mg g^-1 in uranium-spiked seawater, surpassing that of bPEI fiber by 2.5 times. The fiber retains over 95% capacity even after 7 cycles, demonstrating excellent reusability. Quantum-theoretical studies reveal that the flexible TEPA can form a synergistic adsorption network with bPEI, which undergoes adaptive adjustment in seawater to capture uranyl, improving both uranium uptake and selectivity. The proposed underlying mechanism of branched-linear intertwining provides a practical approach for designing high-performance uranium adsorbents.