On the microporous nature of mesoporous molecular sieves

The combination of small-angle X-ray scattering and qualitative porosimetry is applied to the puzzling phenomenon of overly large specific surface are as in some mesoporous silicas. Geometrical calculations, considering the re lationship between structure, lattice parameter, and specific surface area, reveal the latter to be at least 1 order of magnitude smaller than experim ental values obtained from sorption experiments, indicating the presence of micropores. Selective investigation of the mesopore system reveals that up to 63% of the specific surface area is due to microporosity. A relationshi p between the undirected creation of porosity and supramolecular templating is discussed.