As temperatures rise, the performance of membranes for separating gas molecules on the basis of size typically breaks down as a result of increased macromolecular dynamics that compromise the material’s sieving abilities. Now researchers led by Nieck E. Benes present a new method for creating ultrathin membranes that can separate gases at temperatures up to 300 °C (DOI: 10.1021/ja410047u). The unprecedented characteristics of these membranes are thanks to the hybrid organic−inorganic nature of the hypercross-linked films, which are made up of inorganic silicon oxide cage molecules known as polyhedral oligomeric silsquioxane (POSS), linked in a periodic network by organic aromatic imide bridges. Unlike the syntheses of other nanoengineered materials that have been demonstrated for high-temperature separations to date, the two-step synthetic process for generating the polyPOSS-imide films is suitable for largescale, defect-free production. The simple and reliable synthetic route makes the films compatible with industrial-scale applications that require the separation of hot gases, such as large-scale chemical processes and the development of advanced energy production technologies.