Tailoring Multiple Functional Domains of Lithium-Ion Sieves for Sustainable Lithium Extraction from Low-Quality...

Low-quality brines offer virtually infinite lithium sources to resolve the lithium shortage. Lithium-aluminum layered double hydroxides (LiAl-LDHs) have been commercialized as adsorbents in the lithium extraction industry. However, their application in low-quality brines still faces substantial challenges, including poor extraction efficiency limited by low Li⁺ concentration, and "poisoning effect" due to intercalated SO₄^2- encapsulating adsorption sites. Here, we propose a proof-of-concept polymer side-chain structure design (SCSD) strategy for LiAl-LDHs. This approach enables synergistic intralayer/interlayer engineering of LiAl-LDHs with functional polymers, achieving efficient and highly selective Li⁺ extraction from low-quality brines. Moreover, sustainable lithium extraction enables ppb-level residual concentration and production of high-purity Li₂CO₃ from the world's largest low-quality SO₄^2--type brine. By rational design of side chains of polymer building blocks, the local chemical microenvironment and spatial microstructure of LiAl-LDHs can be tailored to accommodate lithium extraction from diverse brines. This work provides a feasible strategy to expand accessible brine resources for the sustainable extraction and recovery of critical metals.