Thin Polymeric Nanoparticle Membrane Coupled With Photothermal Membrane for Unprecedented Solar-Driven VOCs Removal

The removal of trace volatile organic compounds (VOCs) from water through solar-driven evaporation is crucial for ensuring access to safe drinking water. However, the faster evaporation rate of VOCs compared to water presents a significant challenge in effectively removing these hazardous compounds. To address this issue, a thin polymeric nanoparticle separation membrane is integrated with a photothermal membrane, forming a dual-layer solar evaporator. The bottom layer, a hydrogen-bonding complexed  polymer nanoparticle (HCPN) membrane, is fabricated by complexing poly(acrylic acid) and poly(vinylpyrrolidone) into well-dispersed nanoparticles through hydrogen bonding. This HCPN membrane selectively impedes VOC transport while allowing water to pass. The top layer is an in situ-grown photothermal membrane that absorbs solar energy, converting it into heat to drive the water evaporation process. Together, the two layers enable efficient separation and evaporation. This dual-layer solar evaporator demonstrates unprecedented performance, achieving a water evaporation rate of 2.18 kg m^-2 h^-1 under 1 sun irradiation and over 98% rejection to VOCs. The system maintains stability during 30-h continuous operation and performs effectively under real sunlight conditions. With its high efficiency, stability, and adaptability to real-world conditions, this solar evaporator offers a promising solution for providing safe, clean water in remote and underserved areas.