A Cage Structural Hollow-Mesoporous Microreactor Confining Extractant for Lithium Recovery from Salt-Lake Brine.

The sustainable and efficient lithium supply can effectively support the global energy transformation toward decarbonization and the development of electrified industries. However, current established solvent extraction technology suffers from extractant dissolution and low efficiency. Herein, a stable cage structural hollow-mesoporous microreactor with the confinement of lithium extractant, Na[FeCl₄·2TBP], in the hollow cavity is developed for enhancing lithium separation from salt-lake brine. Resultantly, the confinement effect can compartmentalize extractant into micron-sized droplets and prevent its dissolution into aqueous phase. The obtained hollow-mesoporous microreactor exerts outstanding separation performance of Li⁺ from brine, even at Mg/Li mass ratio up to 100:1, with high cyclic stability, adsorption quantity of 34.6 mg g^-1, and Li⁺/Mg²⁺ selectivity of nearly 1000 which is about six times higher than that for conventional extraction by Na[FeCl₄·2TBP]. The mesopores within shells serve as Li⁺ transport channels before reaction with the extractant confined in the hollow cavity. In this article, it is propose that the interfacial electric field generated by surface charges of mesopores can enhance Li⁺ dehydration and diffusion, which synergize with stronger binding capacity of Li⁺ with [FeCl₄·2TBP]^- to enhance the selectivity of Li⁺. These results constitute a novel perspective to design new approaches for lithium recovery from lithium-containing aqueous solutions.