Molecular-enabled lithium-locking for stable sorption-based atmospheric water harvesting

Abstract

Sorption-based atmospheric water harvesting (SAWH) is a sustainable technology for freshwater supply. Lithium chloride (LiCl) is a widely used adsorbent in SAWH. However, lithium leakage occurs frequently owing to the weak binding force between LiCl and the substrate, resulting in poor stability of the SAWH system. Herein, a molecular-enabled lithium-locking sponge (ultra-sponge) is developed for atmospheric water harvesting. Specifically, polyethylene oxide (PEO) is introduced onto the substrate to establish robust multidentate coordination with lithium ions (Li⁺) to achieve the fixation of Li⁺. In comparison, the binding energy is significantly increased by 50%. Owing to this lithium-locking strategy, ultra-sponge maintains a high water absorption rate of 1.75 g g⁻¹ (25 °C, 70% RH) even after 100 cycles, making it one of the most stable materials in the cutting-edge field of SAWH. Furthermore, outdoor experiments have demonstrated the potential applicability of ultra-sponge in agricultural irrigation, achieving an average water-saving effect of 43.2%. The molecular-enabled lithium-locking strategy successfully addresses the longstanding issue of lithium leakage and offers innovative insights for the development of next-generation materials in SAWH.