New layered inorganic−organic magnesium organosilicates were prepared by a single-step template sol−gel synthesis through the reaction of magnesium ions with a synthetic homologous series of urea−alkoxysilanes with the general formula (CH3CH2O)3Si(CH2)3NHC(O)NH(CH2) n CH3, for n = 2, 4, and 6. The nanocomposites were characterized by elemental analysis, solid-state 29Si and 13C nuclear magnetic resonance, X-ray diffraction, and thermogravimetry. The results showed that the hybrid materials exhibit lamellar structures similar to those found in the natural inorganic silicate talc. The influence of the length of the organic group of the urea−alkoxysilane employed in the formation of these layered structures is clearly observed by 29Si NMR spectroscopy. A high degree of condensation for the hybrid synthesized with urea−alkoxysilane containing the longest alkyl chain was obtained. These materials seem to be promising as sorbents for solid-phase extraction of organic pollutant molecules, when dispersed in water, because of their highly hydrophobic character.