Photoinduced passivation-directed growth of δ-MnO2 nanosheets with excellent hydrophilicity for advanced pervaporation desalination membranes

Designing stable, high-performance two-dimensional (2D) MnO 2 membranes for pervaporation (PV) desalination remains challenging. Herein, we present a photoinduced surface passivation strategy for the controlled growth of ultrathin single-layer δ-MnO 2 nanosheets, combined with layer-by-layer assembly to fabricate robust PV membranes. The e − / h +  dual-path mechanism of photoinduced synthesis of MnO 2 was firstly proposed. Comprehensive structural characterizations and DFT simulations reveal that h +  drives surface passivation stabilizes the thermodynamic configuration, while e − modulating growth kinetics to achieve narrow lateral size distributions of nanosheets. Moreover, the process generates Mn 3+ states (Mn (III) ≈ 49.96 %), abundant oxygen vacancies and surface hydroxyls, imparting exceptional hydrophilicity (water contact angle ≈ 10°) and enabling ultrafast water transport through the 2D channels during PV. The resulting MnO 2 membranes exhibit nearly complete salt rejection (99.9 %) and an impressive water flux of 36.53 kg m −2  h −1 in high-salinity feeds, outperforming state-of-the-art membranes. This work establishes photoinduced facet passivation as an effective route for precision-controlled growth of 2D nanosheets, opening promising avenues for next-generation PV membranes and other water purification technologies in harsh environments.