A salt-resistant porous evaporator for solar desalination enabled by hydration-regulated water–ion interactions

A carbon–chitosan–PVA porous foam evaporator achieves 2.47 kg m −2  h −1 with 91.1% efficiency under one sun. • Stabilized interfacial water suppresses ion dehydration and prevents surface salt crystallization. • Interconnected porous architecture enables rapid capillary-driven water supply and efficient heat localization. • Stable desalination is maintained without salt accumulation during long-term operation in saline conditions. Developing efficient, stable, and scalable solar-driven desalination systems remains a critical challenge for sustainable water treatment, particularly under high-salinity and complex wastewater conditions. Herein, a three-dimensional chitosan-based porous foam evaporator is fabricated via a facile foaming–crosslinking strategy, integrating a hydrophilic polymer network with broadband photothermal components for continuous desalination. The interconnected porous structure ensures rapid capillary-driven water supply and effective heat localization, enabling sustained vapor generation. Notably, a hydration-regulated water–ion interaction mechanism is established, in which stabilized interfacial water structures suppress ion dehydration and facilitate continuous salt back-diffusion, thereby preventing salt crystallization and maintaining a salt-free evaporation interface during long-term operation. As a result, the optimized CCA-70-2 achieves an evaporation rate of 2.47 kg·m −2 ·h −1 with an energy efficiency of 91.1% under 1 sun illumination, and maintains 2.07 kg·m −2 ·h −1 during continuous operation in 3.5 wt% NaCl. The system demonstrates robust desalination performance in seawater, dye-containing wastewater, and heavy-metal-contaminated water, producing clean condensate with effective contaminant removal, and achieves 1.27 kg·m −2 ·h −1 under outdoor conditions. This work presents a robust and scalable evaporator design for stable desalination under complex conditions and provides a low-cost pathway toward practical solar-driven water treatment systems. Download: Download high-res image (279KB) Download: Download full-size image