Through a pressure-induced infiltration experiment, it is validated that the degree of hydrophobicity of the nanopore surfaces of a MCM-41 can be increased through gas-solid treatment. Compared with the effects of liquid-solid treatment, the infiltration pressure does not vary much while the defiltration pressure is higher, indicating that the reversibility of confined liquid motion is improved; that is, the sorption curve is less hysteretic. The liquid composition and the post-treatment procedure also have considerable influences on the infiltration and defiltration behaviors. (C) 2008 Elsevier B.V. All rights reserved.