Molecularly porous cross-linked membranes (MPCMs) are described. For example, MPCMs prepared by interfacial polymerization of a reactive macrocycle monomer with intrinsic microporous structure are provided. Macrocycles with multiple reacting sites for cross-linking provide a hyper-cross-linked network suitable for molecular separations employing polar or apolar solvents including organic solvent nanofiltration (OSN).