Covalently constructed porous polyamidoxime nanofibers for enhanced uranium capture

Uranium extraction from seawater is of great importance because of the sustainable development of nuclear energy. Though polyamidoxime-based adsorbents hold significant promise in this field, the entanglement of polymer chains greatly limits their adsorption rate and capacity. Herein, the strategy of constructing rigid aromatic fragments among polyamidoxime chains is reported for producing macroscopic and porous polyamidoxime-based nanofibers (P-PAO-NF). This chemical pore forming process can restrict the movement of polymer chains and expand the space around the functional groups, greatly improving the mass transfer and increasing the utilization efficiency of amidoxime groups. Moreover, this construction process also introduces assistant amide groups for amidoxime groups, which is beneficial to obtaining high uranium affinity. As a result, P-PAO-NF achieves rapid uranium uptake, high utilization rate of amidoxime groups (94.8%), and good uranium/vanadium selectivity (selectivity coefficient = 13.7). A high extraction capacity of 13.02 mg g^-1 from natural seawater is obtained in 15 days, which performs the uppermost property among currently available fibrous adsorbents and many other novel powdery adsorbents. This work develops a facile approach to improve the uranium extraction performance of polyamidoxime-based materials, providing economically feasible uranium adsorbents with industrial potential.