Separation and purification on molecular level from organic solvent mixtures are of paramount importance in industries. Organic solvent nanofiltration (OSN) is a pressure‐driven membrane separation process providing an attractive alternative to conventional energy‐intensive technologies. However, devising a solvent stable, scalable membrane with high permeability and excellent selectivity is still a challenge. Interfacially polymerized thin‐film composite (TFC) OSN membranes integrating an ultrathin selective layer and a porous substrate layer are expected to revolutionize advanced membrane separations. New materials and new strategies to achieve a solvent resistant, highly permeable, and highly selective membrane have been developed in recent years. This review analyses the development of the state‐of‐the‐art interfacially polymerized TFC OSN membranes from the view of structures, materials, and methodologies. First, the emerging structures of current TFC OSN membranes are discussed. The exploitation of new materials (polymers, (nano)fibers, inorganic materials) for the preparation of substrate layer is updated. The advances of new aqueous/organic monomers for synthesis of the selective layer are summarized. Furthermore, the proposed strategies for designing permselective TFC membranes are highlighted. Finally, the challenges together with the future prospects of interfacially polymerized TFC membranes for OSN are proposed.

Membranes with strong solvent resistance and efficient molecular separation are desirable in industries. Especially the fractionation of organic molecules in harsh organic solvents still remains a challenge in the pharmaceutical industry. Here, we report a flexible aliphatic–aromatic polyamide thin-film composite (TFC) membrane with high stability, permeability, and precise selectivity in mild solvents as well as in polar aprotic solvents. This composite organic solvent nanofiltration (OSN) membrane integrates a cross-linked sub-100 nm nanofilm and a nanofibrous sublayer. The flexible aliphatic chains in the polyamide network render the selective layer with a tunable free volume in different organic solvents. Consistent with the solvent swelling degrees, the membrane shows a cutoff in a sequence of dimethyl sulfoxide (DMSO, MWCO: 814 g mol–1) > N,N-dimethyl­formamide (DMF, MWCO: 648 g mol–1) > methanol (MWCO: 506 g mol–1, with DMF activation) > methanol (MWCO: 327 g mol–1). The membrane can precisely fractionate two molecules with difference in molar mass of <166 g mol–1 in a polar aprotic solvent, DMSO. Long-term filtration tests in DMF further demonstrate that the TFC membrane has an outstanding chemical stability and molecular selectivity in aggressive organic media. This work provides an efficient way to control OSN membrane separations by introducing flexible alkane chains into the rigid polymer structure followed by solvent activation. Additionally, the high permeance and excellent separation efficiency of the TFC membrane highlight its great potential for molecular separation in pharmaceutical and chemical industries.