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

Abstract

Zwitterionic hydrogel, serving as carriers for hygroscopic salts, holdssignificant 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 structureof poly-3-[dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azaniumyl]propane-1-sulfonate(PDMAPS)zwitterionic hydrogel/TpPa-1covalent organic frameworks (COFs)/LiCl composite(named as PCL composite hydrogel) is proposed, whichleads tothe accelerated diffusion effect for water molecules. As a result, the vapor adsorption capacity of the optimal compositehydrogel (PCL-42)reaches 2.88g g-1within 12 hours under conditions of 25 ℃ and 90% RH. Simultaneously, themaximum temperature of PCL-42composite could reach 53.9 ℃ after 9 minutes under a simulated solar intensity of 1.0 kW m-2, releasing 91% of the adsorbed water in 3 hours,providing a promising prospect for efficient solar-driven atmospheric water harvesting.Onecycle could collect 7.55 g of fresh waterunder outdoor conditions, and the maximum daily water production may reach 2.71 kgkg-1.The reason lies in thatTpPa-1 COFs lead hydrogel to form a gradient pore structure, which may acceleratethe transport of water molecules, increase the loading capacity of LiCl and enhance the photothermal property.