Mesoporous and microporous silica substrates, each of these kinds endowed with unique textural characteristics, have been prepared via sol-gel and micelle-templating techniques and characterized through N-2 sorption. Materials consisting of a lattice of cage-like monodisperse cavities interconnected by narrow throats (SBA-16), a set of individual cylindrical pores of about the same size (SBA-15), a network of long sinuous ganglion-like sequences of bulges and throats (mesoporous glass, MG), or microporous arrangements of globular nanoparticles (microporous SiO2) have been developed. The N-2 sorption isotherms of rnicroporous silica at 76 K correspond to International Union of Pure and Applied Chemistry (IUPAC) type 1, while those of mesoporous SBA-16, SBA-15, and MG silica match a type IV with hysteresis loops of types H1 or H2 depending on the regularity and nature of the void elements constituting the substrate. A characteristic common to all kinds of porous SiO2 solids herein synthesized is the rigidity of the arrangements, since the total pore volumes attain limiting values. Pore-size distributions of mesoporous SiO2 materials can be calculated by density functional theory (DFT) and sometimes by Barrett-Joyner-Halenda (BJH) methods. The microporous SiO2 adsorbent depicts a larger amount of big micropores (supermicropores) rather than small micropores (ultramicropores). this being a very useful characteristic for the entrapment and ulterior release of volatile compounds. MG substrates depict a percolation vapor threshold while the SBA-16 material shows a cavitation phenomenon during capillary evaporation. Additional properties of SBA-16. SBA-15. MG silica substrates are studied via primary desorption scanning curves. (C) 2004 Elsevier B.V All rights reserved.