Sponge-like adsorption strategy for boosting nanoplastics removal on semi-flexible FeNi-layered double hydroxides via variable-valence doping

Micro/nanoplastics (NPs) have become a new ever-growing threat to the safety of ecosystems and human health. Their efficient capture through porous materials adsorption remains insufficiency to meet practical application requirements. Herein, we propose a sponge-like adsorption strategy for boosting NPs capture in aqueous solution via a novel semi-flexible FeNi-layered double hydroxides (Fe T Ni-LDH) microstructure engineered self-assembly using variable-valence doping approach. Highly-density Fe 3+ is successfully implanted into Ni-LDH through skillful Fe variable-valence (Fe 2+ /Fe 3+ ) doping. With the aid of electrostatic and hydrogen attraction, the rigid LDH nano-sheets are assembled into flexible nano-petals spheres with retractable structures. This Fe T Ni-LDH would be stretched and opened up to adsorb large amounts of NPs via unique sponge-like behavior, and achieve an order of magnitude increase in adsorption capacity (3490 mg·g - 1 ) compared state-of-the-art adsorbents. Moreover, in natural water system, Fe T Ni-LDH is also proved to a removal efficiency exceeding 90 % N-NPs and a significant decrease of the metal ions, broadening its applications in polluted water system. Interestingly, its semi-flexible structure would shrink back to its original petal-like spheres after NPs removal, showing high reproducible cycling performance. The semi-flexible structure design provides a smart sponge-like adsorption strategy for boosting NPs capture.