Adsorption-responsive bionic photothermal ion pump for reversible seawater lithium extraction

Lithium-ion sieve (LIS)-based adsorption technology offers a promising solution for seawater lithium extraction, as it overcomes the challenge posed by the high Na+/Li+ ratio. However, its broader application is hindered by the performance degradation and dissolution loss of LISs after granulation, as well as the low Li+ concentration in seawater. Herein, we propose an Albizia julibrissin-inspired adsorption-responsive photothermal ion pump (APIP) for enhanced and reversible Li+ extraction from seawater. The APIP integrates an interpenetrating network hydrogel with confined hydrogen manganese oxide (HMO) via an innovative in-situ crosslinking and ion-exchange strategy, ensuring the uniform distribution of HMO. The specific adsorption-responsive swelling behaviour of APIP exposes more adsorption sites, resulting in a high Li+ extraction capacity of 34 mg g-1 HMO, even surpassing HMO powders. Moreover, the low free water characteristics and the selective chelation of the polymer chain on Mn2+ effectively mitigate Mn dissolution. Under solar irradiation, the Li+ extraction kinetics of the APIP increased by a remarkable 2.9-fold owing to the evaporative convection and photothermal effects. Collectively, APIP overcomes the application key limitations of powdered LISs, and opens new avenues for seawater utilization and the advancement of the Sustainable Development Goals.