Bandgap Engineered λ‐MnO 2 for Highly‐Efficient Solar‐Driven Lithium Selective Extraction and Freshwater Generation from Saline Lake Brine

Abstract The rapid development of electric vehicles and renewable energy has driven increasing global demand for lithium (Li). However, conventional lithium extraction methods from ore or liquid lithium face challenges such as low efficiency, high costs and environmental concerns. Here, a multifunctional evaporator is developed based on narrow bandgap λ‐MnO 2 for simultaneous Li extraction and freshwater recovery from saline lakes. Three types of λ‐MnO 2 with varying bandgaps of 0.404 eV (HMO‐1), 0.256 eV (HMO‐2), and metallic properties (HMO‐3) are synthesized by regulating oxygen defect content to 3.19%, 6.57%, and 12.61%, respectively. Among these, HMO‐2 exhibits exceptional photothermal conversion performance and high selectivity for Li + . Subsequently, an HMO‐2/3D meta‐paper evaporator (MnPE) was fabricated by depositing HMO‐2 onto the 3D meta‐paper substrate, which achieves an evaporation rate of 3.83 kg m −2 h −1 and a Li + selectivity of 89.50% with the adsorption capacity of 27.6 mg g −1 under 1 sun irradiation. A large‐scale evaporator with a size of 20 × 30 cm is prepared, which also demonstrates comparable performance in outdoor tests. Life cycle assessment (LCA) results indicate that the MnPE has a low environmental impact across all categories, representing a ≈93.11% reduction compared to other methods. This work establishes a scalable, sustainable, and eco‐friendly lithium extraction pathway with global decarbonization goals.