Indium-Based Silica Materials: Sustainable Syntheses Combined with a Challenging Insertion in SiO₂ Mesoporous...

Optimized sustainable procedures in both acidic and basic conditions are considered to meet some of the current environmental challenges of the scientific community. In this paper, the successful syntheses of two classes of indium-based silica nanomaterials are reported. Both procedures were conceived to enhance the sustainability of the synthesis methods and promote their preparations at room temperature while avoiding the hydrothermal treatment under static conditions at 100 °C. A fast, room-temperature synthesis of porous nanospheres was conceived together with an "acid-free" procedure for SBA-15-like materials. Moreover, the isomorphic substitution of silicon with indium was achieved. All the materials were deeply characterized to probe their structural, textural and morphological properties (e.g., transmission electron microscopy, N₂ physisorption, ss MAS NMR of ²⁹Si). The high specific surface area and the mesoporosity were always preserved even under the mild reaction conditions employed. The honeycomb structure and the spherical morphology of SBA-15-like materials and nanospheres, respectively, were also observed. The insertion of indium was confirmed via X-ray photoelectron spectroscopy (XPS) investigations.