<p>Reverse osmosis membranes are essential in wastewater treatment, water reuse and desalination, but conventional polyamide reverse osmosis membranes rely on toxic amine monomers such as <i>m</i>-phenylenediamine, posing notable health risks. Here we show that an interfacial catalytic polymerization strategy enables the development of sustainable polyester thin films for membrane desalination. This approach improves reaction kinetics and polymerization control, facilitating the efficient polymerization of nature-derived phenol and alcohol compounds as non-toxic, cost-effective and environmentally friendly alternatives to <i>m</i>-phenylenediamine. The interfacial catalyst enhances both monomer diffusion and polymerization, overcoming the limited reactivity of nature-derived monomers to produce homogeneous, dense polyester thin films. The resulting membranes exhibit excellent desalination performance (NaCl rejection 99.2%; flux 31.7 l m⁻² h⁻¹ at 15 bar), comparable to commercial BW30 membranes at both coupon and spiral-wound module scales, demonstrating their potential for practical membrane desalination. This work paves the way for further development of sustainable, nature-derived membrane materials for desalination technologies.</p>