Sulfonated Polyethylene for Solar‐Driven Atmospheric Water Harvesting

Atmospheric water harvesting (AWH) is a promising approach to mitigate water scarcity, yet the practical deployment of many existing sorbents is hindered by cost, complex synthesis, and safety risks associated with additive leaching. Moreover, sorbent regeneration for water release often requires heating, which adds energy demand and operational expense. Here, we demonstrate sulfonated polyethylene (PE) as a low‐cost and scalable sorbent for AWH. Using a straightforward sulfonation process, hydrophilic sulfonic acid groups are introduced onto the PE backbone, transforming a hydrophobic commodity polyolefin into a hygroscopic material. Sulfonated PE shows strong water vapor sorption performance across a broad humidity range, reaching an uptake of up to 0.58 g g − 1 at 90% relative humidity (RH). Dynamic vapor sorption measurements further confirm excellent durability, with stable performance over 60 sorption cycles. In addition, without integrating solar absorbing fillers, the intrinsic photothermal feature of sulfonated PE enables an efficient solar‐driven water release without external energy input. This work presents a sustainable route to upcycle widely available polyolefin plastics effective sorbents for atmospheric water harvesting, supporting practical and energy‐efficient freshwater production.