Metal‐ and Halide‐Free, Macroporous Hygroscopic Polymers for Efficient Atmospheric Water Harvesting

Hygroscopic materials based on highly hygroscopic salts are promising for atmospheric water harvesting (AWH), but the metal- or halide-containing highly hygroscopic salts often have leakage and corrosion issues. Here, the design and synthesis of metal- and halide-free, highly hygroscopic, and macroporous polymers from [2-(acryloyloxy)ethyl]trimethylammonium chloride simply via in situ foaming, solidification, and ion exchange are reported. The resulting polymers exhibit highly interconnected macroporous structure, robust compression, and leakage-free performance, and they also demonstrate relatively high moisture adsorption capacities (up to 1.24 g g^-1 water at 85% relative humidity, accelerated adsorption rates, and efficient desorption. The polymers can harvest 0.76 g g^-1 water per adsorption-desorption cycle and show high reusability, without obvious deterioration over 10 cycles of adsorption, desorption, and water collection. With the incorporation of carboxylic multi-walled carbon nanotubes into the hygroscopic polymers, solar-driven AWH is realized, without the requirement of additional energy. On the whole, the metal- and halide-free, highly hygroscopic polymers exhibit the advantages of ease of preparation, energy saving, environmental protection, and economic sustainability for AWH.