Effective mesoporous composite adsorbents of water vapor can be prepared using a novel "one-pot", sol-gel procedure with ethyl silicate 40 as a silica precursor. The multilayer mechanism of water adsorption appears to be responsible for high adsorption of water on the prepared samples. In the case of the lithium bromide doped samples this adsorption takes the form of a volume filling. The Dubinin-Astakhov equation very well portrays adsorption of water by the synthesized composites in relative pressures < 0.3, The values of the exponent r increase with the dopant content while those of the characteristic energy E are fairly constant.