Nanoporous ZnO/SiO₂ aerogel and xerogel composites via a one-pot sol-gel process at room temperature

A series of nanoporous ZnO/SiO₂ aerogels and xerogels were synthesized via an epoxide-assisted sol-gel route, aimed at producing zinc-rich composite materials with tunable properties. By systematically varying the zinc precursor, incorporating lithium chloride, and modifying the drying process, the resulting materials exhibited significant differences in crystallinity, morphology, and porosity. X-ray diffraction and FTIR analyses revealed primarily amorphous Zn-Si networks, with dispersed nanoscale crystalline phases, including zinc hydroxide nitrate, smithsonite, and simonkolleite. The incorporation of zinc into the silica matrix was achieved with stoichiometric control. Upon heat treatment, hydroxide phases were converted into mesoporous ZnO clusters, while preserving high surface areas and thermal stability. The aerogels showed low bulk density and open mesoporosity, whereas the xerogels exhibited enhanced structural robustness with similar surface areas. Optimized heat-treated aerogels reached surface areas up to 260 m² g^-1, particle sizes down to 23 nm, and thermal stability beyond 800 °C. These findings confirm the successful design of hybrid Zn/SiO₂ nanomaterials with tunable architectures, positioning them as promising candidates for use in catalysis, adsorption, and thermal processing.