Functionalized conducting carbonaceous materials were easily prepared from sucrose and the clay mineral sepiolite. In a microwave assisted first step, sucrose is transformed into caramel that penetrates into the pores of sepiolite. A second step consists in the controlled thermal treatment of the intermediate caramel–sepiolite nanocomposites in the absence of oxygen to obtain carbon–sepiolite materials. These products were characterized as graphene-like nanostructured materials that can be further functionalized by grafting reactions using different organoalkoxysilanes. In this way, sulfonate groups that can act as cation exchanger were anchored to the carbon–sepiolite solids, following two different routes that involved the use of (2-phenylethyl)trichlorosilane and 2-(4-chlorosulfonylphenyl)-ethyltrichlorosilane. The graphene-like sepiolite nanocomposites can be used as electrode materials for rechargeable lithium batteries, showing better cyclability and Li-insertion properties than the nanostructured carbon without the silicate counterpart. The sulfonate derivatives, showing simultaneously ion-exchanging ability and conducting behavior, were used to develop ion-selective electrodes with specificity towards monovalent cations. The potential use of other organosilanes can open way to the development of other multifunctional materials for application in electrochemistry and other research fields.