Natural Resin Nanofilms through Flexible Coordination for Molecular Separation

Abstract Forestry biomass, with its diverse functionalities and abundant resources, holds great potential for the sustainable development of thin‐film technologies. However, high brittleness arising from the rigid structural units of most forestry biomass materials significantly hinders thin‐film processing. We demonstrate the transformation of rosin, a typical brittle forestry resin, into mechanically robust nanofilms with flexible chemical linkages. Carboxylic rosin derivatives solubilized in turpentine, a natural oleoresin solvent, were chemically assembled into nanofilms via interfacial coordination with aqueous metal ions. Tunable metal‐rosin coordination enables precise structural modulation of nanofilms to achieve exceptional stiffness (Young's modulus>120 GPa) while its dynamic nature renders nanofilms high elasticity for pliable integration. The resulting nanofilm composite membranes exhibit durable and efficient molecular sieving during nanofiltration, with pressure resistance up to 20 bar and superior permselectivity. As an emerging form of natural resin, these nanofilms may revolutionize the paradigm of biomass‐based thin films by overcoming brittleness through flexibility.