Ion engineering toward solar interfacial evaporation: From molecular mechanisms to systemic integration

Solar-driven interfacial water evaporation (SDIWE), characterized by low emissions, low energy consumption, and modular design, is emerged as a promising approach to addressing global water scarcity. Despite these advantages, salt crystallization and performance degradation remain significant challenges. Conventional salt-rejection systems often improve durability at the expense of evaporation efficiency. This review highlights ion engineering as an innovative strategy to overcome these limitations by incorporating functional ionic groups into polymer networks to enhance SDIWE performance. By leveraging the Donnan exclusion effect, anti-polyelectrolyte effect, and Hofmeister effect, ion engineering enables intrinsic salt resistance and maintains high vaporization efficiency even under high-salinity conditions. Recent advances in ion engineering for SDIWE are systematically summarized from the perspectives of the chemical design of ionic units, microstructural evolution, water-state modulation, and crystallization inhibition. Furthermore, this review bridges the gap between laboratory-scale research to practical applications and outlines future opportunities for the development of smart responsive materials and system-level optimization.