Multilevel Salt Confinement of Graphene Oxide Aerogel Enables Ultrahigh Moisture Capture at Low Humidity Conditions

Sorption-based atmospheric water harvesting (SAWH) offers a sustainable route to alleviate freshwater scarcity, yet achieving high water uptake under low relative humidity (RH) remains challenging due to limited active sites and sluggish mass transport. Herein, we demonstrate a superhygroscopic aerogels (SHAs) based on a hierarchical salt confinement strategy within a graphene oxide (GO) framework, which exhibits unprecedented water uptake under low-humidity conditions. Through a multiscale in situ salt-incorporating approach, LiCl is hierarchically confined within macropore surfaces, mesoporous channels, and GO interlayer galleries of SHAs. This in situ confinement architecture markedly increases effective salt loading while preserving maximum accessibility of hygroscopic sites, overcoming the limitations of conventional postimpregnation methods. Concurrently, the continuous capillary network of the SHAs synergizes with the strong hygroscopicity of LiCl to promote rapid moisture infiltration and transport, substantially enhancing adsorption–desorption kinetics. As a result, the SHAs achieve a high water uptake of 1.35 g·g–1 within 6 h at 25 °C and 30% RH, representing the state-of-the-art in reported SAWH materials. Moreover, GO provides efficient photothermal conversion, allowing 85% of the absorbed water to be released within 155 min under 1.0 sun irradiation. Under natural sunlight, the SHAs produces water at a rate of 4.94 g·g–1day–1. This work highlights multilevel salt confinement in graphene oxide aerogels as a powerful design paradigm for high-efficiency SAWH in arid and low-humidity environments.