3D Printed Cellulose Nanofiber Aerogel Scaffold with Hierarchical Porous Structures for Fast Solar‐Driven Atmospheric Water Harvesting

Hygroscopic salt‐based composite sorbents are considered ideal candidates for solar‐driven atmospheric water harvesting. The primary challenge for the sorbents lies in exposing more hygroscopically active sites to the surrounding air while preventing salt leakage. Herein, a hierarchically structured scaffold is constructed by integrating cellulose nanofiber and lithium chloride (LiCl) as building blocks through 3D printing combined with freeze‐drying. The milli/micrometer multiscale pores can effectively confine LiCl and simultaneously provide a more exposed active area for water sorption and release, accelerating both water sorption and evaporation kinetics of the 3D printed structure. Compared to a conventional freeze‐dried aerogel, the 3D printed scaffold exhibits a water sorption rate that is increased 1.6‐fold, along with a more than 2.4‐fold greater water release rate. An array of bilayer scaffolds is demonstrated, which can produce 0.63 g g−1 day−1 of water outdoors under natural sunlight. This article provides a sustainable strategy for collecting freshwater from the atmosphere.