Composites for destroying chemical and biological agents such as toxins and bacteria, and methods of preparing and using those composites are provided. According to the invention, the substance to be destroyed is contacted with the inventive composites which comprise finely divided metal oxide nanoparticles at least partially coated with carbon. Advantageously, the composites exclude water while not excluding the target compound or adsorbates. The desired metal oxide nanoparticles can be pressed into pellets for use when a powder is not feasible. Preferred metal oxide nanoparticles include MgO, SrO, BaO, CaO, TiO2, ZrO2, FeO, V2O3, V2O5, Mn2O3, Fe2O3, NiO, CuO, Al2O3, SiO2, ZnO, Ag2O, and mixtures thereof.