Applicability of classical methods of pore size analysis for MCM-41 and SBA-15 silicas

Two most popular ordered mesoporous silicas, MCM-41 and SBA-15, exhibiting uniform mesopores of approximately cylindrical shapes, have been used as model adsorbents for verification, improvement and/or development of adsorption-based methods for characterization nanoporous materials. While the applicability of the classical methods for pore size analysis was widely examined by employing MCM-41 materials, the largepore materials such as SBA-15 did not find adequate usage for this type of studies. The current work addresses the issue of applicability of classical methods such as Barrett–Joyner–Hallenda (BJH) and Broekhoff–de Boer (BdB) methods for pore size analysis of mesoporous silicas by using MCM-41 and SBA-15 materials as model adsorbents. In addition, the Kruk–Jaroniec–Sayari (KJS) method, which is based on the BJH algorithm and experimental relations for the pore width and statistical film thickness, is discussed too. While the MCM-41 materials cover the range of small mesopores (about 2–7 nm), the inclusion of SBA-15 materials allowed us to examine the range of the pore diameters up to about 12 nm. The high quality MCM-41 and SBA-15 samples are used to discuss the applicability and limitations of the aforementioned characterization methods and to propose some recommendations for pore size analysis of these materials.