MCM-41 Porosity: Are Surface Corrugations Micropores?

• Main Authors: Ángel Berenguer-Murcia, Diego Cazorla-Amorós, Ángel Linares-Solano
• Format: Article
• Language: English
• Published: Hindawi - SAGE Publishing 2011-06-01
• Series: Adsorption Science & Technology
• Online Access: https://doi.org/10.1260/0263-6174.29.5.443

Since the discovery of MCM-41, the interpretation of its structure and porous texture has evolved from a simple model of straight parallel mesopores to a much more complex model with a rough surface. The physisorption of nitrogen at 77.3 K and 87.5 K and of carbon dioxide at 273 K was carried out on both MCM-41 and a precipitated silica (PSIL). This silica was prepared for comparison purposes under identical conditions to those for MCM-41 but without the use of the surfactant. The adsorption characteristics of both materials for both adsorptives were indistinguishable at low adsorption pressures independent of the adsorption temperature employed, suggesting similarities in parts of their porosity (i.e. excluding mesoporosity). We propose that, in addition to its well-acknowledged mesoporosity, MCM-41 includes considerable surface roughness and/or heterogeneities similar to that shown by microporous silica. This surface structure appears to have adsorption characteristics indistinguishable from classical microporosity, and may also be an important feature of this material which is very often not taken into consideration in most of its applications.