Common methods for fabricating membrane-based scaffolds for tissue engineering with (hydrophobic) polymers include thermal or liquid-phase inversion, sintering, particle leaching, electrospinning and stereolithography. However, these methods have limitations, such as low resolution and pore interconnectivity and may often require the application of high temperatures and/or toxic porogens, additives or solvents. In this work, we aim to overcome some of these limitations and propose a one-step method to produce large porous membrane-based scaffolds formed by air-water interfacial phase separation using water as a pore-forming agent and casting substrate. Here, we provide proof of concept using poly (trimethylene carbonate), a flexible and biocompatible hydrophobic polymer. Membrane-based scaffolds were prepared by dropwise addition of the polymer solution to water. Upon contact, rapid solvent–non-solvent phase separation took place on the air-water interface, after which the scaffold was cured by UV irradiation. We can tune and control the morphology of these scaffolds, including pore size and porosity, by changing various parameters, including polymer concentration, solvent type and temperature. Importantly, human hepatic stellate cells cultured on these membrane-based scaffolds remained viable and showed no signs of pro-inflammatory stress. These results indicate that the proposed air-water interfacial phase separation represents a versatile method for creating porous membrane-based scaffolds for tissue engineering applications.