Adsorption isotherms of argon, nitrogen and oxygen have been determined at 77 K on a sample of MCM-41, a novel form of aluminosilicate. All the isotherms are Type IV in the IUPAC classification. The argon and oxygen isotherms exhibit well defined hysteresis loops, whereas the nitrogen isotherm is completely reversible. This unusual character is attributed to capillary condensation taking place within a narrow range of tubular pores of effective width 3.3–4.3 nm. MCM-41 shows considerable promise as a model mesoporous adsorbent

Physisorption measurements of nitrogen and oxygen reveal that MCM-41 has a well defined mesoporous structure and is a highly promising model adsorbent.

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Adsorption isotherms of carbon dioxide, sulfur dioxide and water vapour have been determined on a well characterized sample of MCM-41. The shape of the carbon dioxide isotherm (at 195 K) is similar to that given by mesoporous hydroxylated silica, whereas the water isotherm (at 303 K) is of Type V in the IUPAC classification and its shape is therefore indicative of a more hydrophobic behaviour. lsosteric enthalpies of adsorption, calculated from the sulfur dioxide isotherms (at 254 and 273 K), reveal strong energetic heterogeneity in the adsorbent-adsorbate interactions and it appears that the high-energy sites occupy ca.

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