Tree-inspired nanofiber aerogel with vertically aligned microchannels for salt-resistant solar desalination and oil-in-water emulsion separation

Solar-driven water evaporation technology is considered a promising solution to the global water shortage due to its environment-friendliness, sustainable, and energy-efficient. Whereas, challenges remain as far as the relatively low water-transfer rates, unsatisfactory energy efficiency, and significant salt precipitation. Herein, inspired by water transportation and transpiration process of natural trees, biomimetic polyacrylonitrile (PAN)-based nanofibrous aerogels with vertically aligned channels were developed for solar-driven seawater desalination, water purification, and oil water separation. The honeycomb porous structure, vertically aligned channels, and good hydrophilicity, synergistically combined with the light absorption properties of sodium alginate (SA), tannic acid (TA), and Fe 3+ chelation, facilitate rapid water transportation and enhance multiple reflections of solar light. The aerogels exhibit excellent compressive fatigue durability, strong water-transfer capability, and high solar absorption efficiency of up to 91 %. In addition, the interconnected 3D structure drastically reduces the enthalpy of vaporization. The composite aerogels achieved a water evaporation rate of 1.6 kg m −2  h −1 and a high photothermal conversion efficiency of 96.73 % under 1 sun illumination. More importantly, the aerogels exhibit underwater superoleophobicity, enabling them to separate surfactant-stabilized oil-in-water emulsions with a high permeation flux (3106.12 L m −2  h −1 ) and separation efficiency (99.68 %), making it an ideal candidate for water purification.