Boosting atmospheric water harvesting with a solar-driven humidity-adaptable membrane device

Atmospheric water harvesting (AWH) is vital to supplying freshwater in arid regions. Sorbent-based harvesting stands out because it can adapt to weather conditions and utilize low-grade energy. Current harvesting research focuses on sorbent material preparation, particularly solid sorbents, such as metal-organic frameworks (MOFs), but they show poor adaptability to changing relative humidities and temperatures in real-world applications. We present a solar-driven multi-stage membrane-based AWH device using a liquid hygroscopic solution as the sorbent. The design of our device helped boost water production and adapt to changing weather conditions. The device could produce 6.27, 2.41, and 0.82 kg of freshwater/m²/day at relative humidities of 69%, 35%, and 19% at 25°C, respectively, using solar energy. The corresponding water production capacities are 1.76 × 10⁻⁷, 0.64 × 10⁻⁷, and 0.26 × 10⁻⁷ kg/J.