TpPa-1 COFs-Enhanced Zwitterion Hydrogel for Efficient Harvesting of Atmospheric Water.

Zwitterionic hydrogel, serving as carriers for hygroscopic salts, holds significant potential in atmospheric water harvesting. However, their further application is limited by structural collapse in high-concentration salt solution and poor photothermal conversion performance. Herein, the graded pore structure of poly-3-[dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azaniumyl]propane-1-sulfonate (PDMAPS) zwitterionic hydrogel/TpPa-1 covalent organic frameworks (COFs)/LiCl composite (named as PCL composite hydrogel) is proposed, which leads to the accelerated diffusion effect for water molecules. As a result, the vapor adsorption capacity of the optimal composite hydrogel (PCL-42) reaches 2.88 g g within 12 hours under conditions of 25 °C and 90 % RH. Simultaneously, the maximum temperature of PCL-42 composite could reach 53.9 °C after 9 minutes under a simulated solar intensity of 1.0 kW m, releasing 91 % of the adsorbed water in 3 hours, providing a promising prospect for efficient solar-driven atmospheric water harvesting. One cycle could collect 7.55 g of fresh water under outdoor conditions, and the maximum daily water production may reach 2.71 kg kg. The reason lies in that TpPa-1 COFs lead hydrogel to form a gradient pore structure, which may accelerate the transport of water molecules, increase the loading capacity of LiCl and enhance the photothermal property.