Polymeric Membranes with Selective Solution-Diffusion for Intercepting Volatile Organic Compounds during Solar-Driven Water Remediation.

Solar evaporation through a photothermal porous material provides a feasible and sustainable method for water remediation. Several photothermal materials have been developed to enhance solar evaporation efficiency. However, a critical limitation of current photothermal materials is their inability to separate water from the volatile organic compounds (VOCs) present in wastewater. Here, a microstructured ultrathin polymeric membrane that enables freshwater separation from VOC pollutants by solar evaporation with a VOC removal rate of 90%, is reported. The different solution-diffusion behaviors of water and VOCs with polymeric membranes facilitate their separation. Moreover, owing to increased light absorption, enlarged liquid-air interface, and shortened mass transfer distance, the microstructured and ultrathin configuration of the membrane helps to balance the tradeoff between permeation selectivity and water production capacity. The membrane is not only effective for evaporation of simulated volatile pollutants in a prototype, but can also intercept complex volatile organic contaminants in natural water sources and produce water that meets drinking-water standards. With practical demonstration and satisfactory purification performance, this work paves the way for practical application of solar evaporation for effective water remediation.