Super-microporous silicon material with high hydrothermal stability denoted as MCM-48-T has been prepared from mesoporous MCM-48 by high temperature treatment. The structural and chemical property of MCM-48-T has been characterized by variety of techniques such as small-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption-desorption, infrared spectroscopy (IR) and Si-29 MAS NMR, etc. The results showed that Si-OH groups are forced to condense by the treatment of high temperature and the pore size of MCM-48-T is around 1.03 nm in the super-microporous range. Besides, the ratio of Q(4)/Q(3) increases considerably. Compared with the original material (MCM-48), the hydrothermal stability of MCM-48-T has significantly enhanced. (C) 2009 Elsevier B. V. All rights reserved.