Catalytic Interface Engineering of Ce-Doped Cu-MOFs for Photothermal Desalination in a Flexible Electrospun Bilayer Membrane

The global shortage of freshwater, intensified by rising salinity in natural water sources, calls for scalable and energy-efficient desalination technologies. Interfacial solar-driven evaporation offers a promising solution, yet its practical implementation is hindered by high-cost photothermal materials and complex fabrication. Herein, we develop a flexible, self-floating electrospun bilayer membrane composed of Ce-doped Cu-based MOFs, multiwalled carbon nanotubes, polyvinylidene fluoride, and polyacrylonitrile, which was designed for efficient photothermal seawater desalination. A key distinguishing feature lies in the Ce doping strategy. During calcination, Cu-MOFs yield CuO and undesired Cu₂O, which reduce photothermal efficiency. The introduced cerium species form CeO₂/Ce₂O₃ can catalytically oxidize residual Cu₂O into CuO to enhance light absorption. X-ray photoelectron spectroscopy confirms the formation of CeO₂/CuO heterojunctions with improved interfacial synergy. Under 1 kW·m^-2 solar irradiation, the optimized membrane reaches a surface temperature of 61.4 °C and delivers a high evaporation rate of 1.98 kg·m^-2·h^-1. The membrane exhibits strong mechanical strength, reaching a tensile value of 9.92 MPa. It also demonstrates a rapid thermal response by cooling from 61.4 to 26.1 °C within 90 min, which highlights its focus on efficient evaporation dynamics rather than heat retention. This work offers a cost-effective and scalable strategy for interfacial solar-driven evaporation membrane fabrication and introduces a Ce-assisted catalytic route to enhance photothermal conversion via compositional control and interfacial engineering.