Solar-driven interfacial evaporation via leaf-inspired membranes: Toward efficient seawater desalination and wastewater treatment

Solar-driven interfacial evaporation offers a promising pathway for seawater desalination and wastewater treatment. However, the practical implementation of advanced evaporators faces challenges in heat localization and water transport. Here, we report a leaf-inspired membrane (LIM) that integrates hierarchical structural design with multifunctional materials engineering to enable high-efficiency solar evaporation. The LIM adopts a Janus architecture and mimics the vein networks and porous microstructure of natural leaves. This design presents 94.9 % solar absorption and reduces water evaporation enthalpy by 42.4 %. Under a unidirectional flow and suspension mode, the evaporator achieves an evaporation rate of 2.86 kg m⁻² h⁻¹ for pure water and 2.48 kg m⁻² h⁻¹ for 20 wt% brine under 1-sun irradiation. Shaping the membrane into a 3D sinusoidal configuration and introducing bidirectional fluid transport enhances thermal energy recycling, boosting the rate of pure water to 3.10 kg m⁻² h⁻¹. The asymmetric Janus structure spatially separates the processes of evaporation and salt crystallization, enabling continuous freshwater production alongside salt recovery—thus supporting zero liquid discharge. Outdoor field trial confirms that the 3D-structured evaporator operates reliably under natural sunlight (0.35–0.82 kW m⁻²), yielding 13.91 kg m⁻² of water vapor and 0.48 kg m⁻² of salt over an 8-hour period, while reducing ion concentrations by 3–4 orders of magnitude. Beyond desalination, the LIM also demonstrates versatile purification capabilities for diverse wastewater, including dye-laden effluents, emulsions, suspensions, and corrosive solutions. This biomimetic design bridges material engineering with fluidic control, offering a scalable strategy for sustainable water-energy solutions.