Flexible MXene-based Janus porous fibrous membranes for sustainable solar-driven desalination and emulsions separation

Sustainable solar energy driven seawater desalination technology is currently deemed as a promising pathway to overcome the shortage of freshwater resources, but solar water evaporation material suffers from serious salt-fouling, low freshwater yield, and poor long-term performance in seawater. Herein, a Janus photothermal porous fibrous membrane, composed of hydrophobic MXene/Poly(dimethylsiloxane) coatings and a hydrophilic polylactic acid/TiO2 nanofluids porous fibrous membrane, was prepared. During the solar-driven seawater desalination process, the hydrophilic fibrous membrane, functioned as salt-rejection barrier, induced by TiO2 nanofluids and transport seawater to the surface through its microporous channels; the MXene/PDMS coatings acted as a photothermal layer and generated localized heat at the water-vapor interface upon light irradiation. The solar-thermal test results show that, the Janus porous fibrous membrane displays stable solar-thermal conversion efficiency of 60%, freshwater yield of 1 kg m-2 h-1 and low ion concentration (≤1 ppm) under 1 sun irradiation in direct contact mode, which is superior to other literatures reported. With synergistic effect of TiO2 nanofluids and MXene, the Janus fibrous membrane exhibits a high salt rejection rate of 99.95%, and antibacterial activity as high as of 100%. Notably, benefiting from opposite wettability of Janus porous fibrous membrane, the as-prepared membranes also display excellent separation flux and high separation accuracy (>99.95%) in various surfactant-stabilized oil/water emulsions. It is anticipated that this versatility of Janus porous fibrous membrane has excellent photothermal conversion capability and separation properties, making it have great application potential in using sustainable solar energy to collect freshwater from seawater, medical service wastewater and other application in environmental protection.