Bioinspired hierarchical porous membrane for efficient uranium extraction from seawater

The oceans offer a virtually infinite source of uranium and could sustain nuclear power technology in terms of fuel supply. However, the current processes to extract uranium from seawater remain neither economically viable nor efficient enough to compete with uranium ore mining. Microporous polymers are emerging materials for the adsorption of uranyl ions due to their rich binding sites, but they still fall short of satisfactory performance. Here, inspired by the ubiquitous fractal structure in biology that is favourable for mass and fluid transfer, we describe a hierarchical porous membrane based on polymers of intrinsic microporosity that can capture uranium in seawater. This biomimetic membrane allows for rapid diffusion of uranium species, leading to a 20-fold higher uranium adsorption capacity in a uranium-spiked water solution (32 ppm) than the membrane with only intrinsic microporosity. Furthermore, in natural seawater, the membrane can extract as much uranium as 9.03 mg g−1 after four weeks. This work suggests a strategy to be extended to the rational design of a large family of microporous polymer adsorbents that could fulfil the vast promise of the oceans to fuel a reliable and potentially sustainable energy source.