Modular gradient-porous evaporator for efficient solar desalination and autonomous salt harvesting from high-salinity...

Solar-driven interfacial evaporation offers a promising approach for treating high-salinity brine, but the long-standing trade-off between evaporation efficiency and salt accumulation remains a major challenge to large-scale deployment. While most efforts have focused on salt rejection, the economic and environmental benefits of simultaneous salt harvesting have been largely overlooked. Herein, we develop a modular gradient-porous network (GPN) evaporator composed of three functionally coupled yet structurally distinct modules that enable efficient solar evaporation and autonomous salt harvesting. This architecture integrates photothermal conversion, fluid transport, and salt management into a single synergistic system. In a continuous 168-h test, the GPN achieves an evaporation rate of 4.03 kg m⁻² h⁻¹, a salt collection rate of 0.32 kg m⁻² h⁻¹, and a salt detachment rate of 95.6 %. Outdoor tests further validate its practicality, demonstrating a freshwater production rate of 3.35 kg m⁻² h⁻¹ and a salt collection rate of 0.26 kg m⁻² h⁻¹. This work redefines the design principle of solar evaporators, shifting from merely resisting salt to actively harvesting it, thereby enabling a circular-economy approach to brine management. Moreover, its compatibility with diverse photothermal materials provides a versatile platform for next-generation solar evaporators to address water scarcity and brine pollution.