Rattan‐Based Solar Evaporator Hits 3.34 Kg·M −2 ·h −1 and Long‐Term Salt Resistance via Programmed Carbonization

Abstract Global water scarcity urgently demands sustainable purification solutions. A high‐performance solar evaporator crafted entirely from renewable biomass is reported, e.g., rattan, through an innovative programmed carbonization process. By applying controlled gradient heating, bimodal hierarchical porous structures are engineered within the plant material that optimize water transport, heat localization, and vaporization energy reduction. This yields a record evaporation rate of 3.34 kg m −2 h −1 under 1 sun, which is 1.69× faster than unprogrammed carbonization. Critically, the design achieves exceptional durability, withstanding continuous outdoor evaporation for over 14 days in high‐salinity brine (20 wt.% NaCl) without noticeable salt accumulation or microbial growth. Outdoor experiments further confirm its stable daily fresh water production (≈24.49 L) with high quality that meets World Health Organization (WHO) drinking standards. This work offers a scalable, eco‐friendly path to freshwater access, particularly for off‐grid communities, by leveraging globally abundant plants and requiring only sunlight.