Asymmetric hydrophilicity-driven fast water diffusion enabling heterogeneous hygroscopic gels toward high-yield atmospheric water harvest

Abstract

Hygroscopic polymeric gels hold a promising avenue for sustainable sorption-based atmospheric water harvesting (SAWH). However, conventional designs relying on homogeneous hydrophilic networks face an inherent trade-off: strong hydrogen bond-mediated water retention and osmotic pressure-driven water transport. Here, we propose a strategy to construct heterogeneous structure composed of hydrophilic pectin shell and relatively hydrophobic graphene oxide (GO) sheets core for hygroscopic polymeric organgel integrated with glycerol. The pectin shell acts as a gas-liquid conversion interface, enabling continuous and efficient water condensation. The incorporation of pristine GO interlayers significantly reduces the interaction between adsorbed water molecules and hydrophilic functional groups. This configuration enhances glycerol-enabled osmotic pumping for rapid water transport into storage and supports efficient solar-driven water release. The resulting organgel exhibits a high water uptake capacity ranging from 0.83 to 6.57 g g^-1 across a broad relative humidity spectrum (30% to 90%). Under 1.0 sun illumination, it achieves a notable desorption rate of 2.06 kg m^-2 h^-1, contributing to a daily water yield of up to 2.86 L_waterkg_sorbent^-1day^-1. This heterogeneous structure challenges the conventional paradigm of maximizing hydrophilicity and supports the rational design of high-performance toward next-generation SAWH materials.