All-Weather Atmospheric Water Harvesting Enabled by Hygroscopic Hydrogel Paint

Hygroscopic hydrogels have been receiving widespread attention as effective atmospheric water harvesters due to their freshwater production capabilities for alleviating water scarcity stress in arid regions. Nevertheless, not only can the hydrophilic networks notably hinder water release but also harsh preparation conditions (UV light and oxygen-free environment) are required to achieve free-radical polymerization. Herein, facile and processable moisture-harvesting hydrogel paints (MHPs) have been developed to address these challenges. Benefiting from the high tunability and processability, the MHPs can be optionally cured into moisture-harvesting hydrogels (MHGs) with different sizes by various operations according to actual circumstances, manifesting their potential for multiscenario applications. Via the synergistic effect of thermal-responsive networks and hygroscopic components, the MHGs can harvest atmospheric water with a broad range of relative humidities (RH, 10–90%), high water uptake (highest ∼50% of hydrogel's own weight at ∼90% RH, 25 °C within 24 h), fast moisture-absorbing rate (up to ∼0.23 g g–1 h–1 at ∼90% RH, 25 °C), low energy, rapid water release rate (∼0.2 g g–1 h–1 at ∼90% RH, 4 °C), and outstanding cycling stability. Also demonstrated is a proof-of-concept outdoor water-collecting system, which possesses ∼2.5 mL g–1 (L kg–1) water yield per day to satisfy an adult's daily water demand. Our low-cost and easy-to-scale-up MHGs can provide a viable solution to design next-generation atmospheric water harvesters for achieving efficient, sustainable, and multiscenario applications.