The application of photothermal conversion type heteropolyacid hydrogels in efficient atmospheric water harvesting and liquid water storage

Atmospheric Water Harvesting (AWH) represents a feasible technological approach for mitigating water shortages, offering a potential strategy for the global issue of water scarcity. This study uses ether extraction to explore the synthesis of keggin-type Heteropolyacid Phosphomolybdenum tungstic Acid (HPA). The unique properties of this heteropolyacid, such as strong acidity, high specific surface area combined with a hierarchical pore architecture, and electrostatic interactions, make it highly effective for water adsorption. By modifying the HPA, a new class of copolymer monomers (HPAs) was developed and then copolymerized with acrylic acid, resulting in the creation of a multifunctional polymeric material (HPAs-PAA) that has excellent biphasic water adsorption capacity to adsorb both water vapor and liquid water. The synthesized material has significant performance characteristics, with an adsorbent capacity of 1837 g/g of water vapor, a wide hygroscopic range (25 % RH-90 % RH), and a maximum water vapor adsorption capacity of 1381.8 mg/g at 90 % RH. Furthermore, under standard solar irradiation conditions of 1 kW/m 2 , the material demonstrates a desorption rate of 0.29 kg/m 2 /h, showcasing exceptional desorption performance. After 30 adsorption–desorption cycles, the HPAs-PAA retains 84.57 % of its initial capacity (from 951.6 mg/g to 804.8 mg/g), indicating remarkable water vapor adsorption–desorption cycle stability. Furthermore, the material exhibits excellent moisture retention capabilities and holding properties, rendering it an ideal adsorbent for AWH in arid environments. It also provides a new approach to developing sustainable water harvesting materials.