Facile preparation of self-floating photothermal membranes with simultaneous mechanical stability and antibacterial activity for solar-driven interfacial water evaporation is regarded as a practical approach for clean water production. Herein, a robust porous bi-layered photothermal membrane (carbon nanotube@polyethylene imine/mixed cellulose esters, CNT@PEI/MCE), where the top solar conversion layer of pristine CNTs is seamlessly connected to the bottom heat transfer barrier layer of hydrophilic MCE, is facilely prepared via a simple vacuum filtration. With the synergistic integration of MCE-mediated heating localization, CNT-mediated solar-heating, PEI-mediated hygroscopicity and noncovalent interactions, the CNT@PEI/MCE membrane can stay at the water–air interface with Wenzel's wetting behavior and can thus achieve a high interfacial water evaporation efficiency (72%) and a rapid evaporation rate (4.23 times higher than that of pure water) under simulated solar irradiation. Meanwhile, the CNT@PEI/MCE membrane exhibits good mechanical stability, strong operability, distinct antibacterial activity and high durability. This advanced membrane, together with its cost-effectiveness, provides a practical sustainable energy technique for clean water production.