Solar-driven scalable hygroscopic gel for recycling water from passive plant transpiration and soil evaporation

In the face of escalating global water scarcity, intensified by population growth and agricultural demands, there is an urgent need to improve water efficiency in greenhouse cultivation. The rapid development of atmospheric water harvesting technology offers us an opportunity to address this issue. Here a novel, solar-driven, scalable hygroscopic gel, termed TCP-Li, that demonstrates exceptional water uptake capacity (3.38 g_water g_sorbent⁻¹) and rapid solar thermal water release was reported. As a proof-of-concept application, we utilize this material in a transpiration and evaporation adsorption device (TEAD), which leverages the properties of TCP-Li to efficiently harvest water vapour from plant transpiration and soil evaporation. TEAD operates passively, absorbing moisture at high relative humidity during the night and releasing water for irrigation during the day using natural sunlight. Greenhouse experiments confirmed the efficacy of TEAD in ensuring normal plant growth while providing additional irrigation water (87.1 g per plant and 1,890.6 g m⁻²), thereby achieving an average water-saving effect of 44.9%. This study introduces a groundbreaking solution aimed at enhancing water efficiency in greenhouse cultivation, offering substantial potential for commercial and large-scale agricultural applications and significantly contributing to mitigating the global water crisis and optimizing water use in modern agriculture.