Nb2O5/SiO2 mesoporous monoliths synthetized by sol–gel process using ammonium niobate oxalate hydrate as porogenic agent

Niobium pentoxide/silica mesoporous monoliths were prepared by using silicon alkoxide and a bifunctional reactant, ammonium niobate (V) oxalate hydrate (NbOXA), as niobium pentoxide precursor and porogenic agent. The influence of the thermal treatment on the structural, textural characteristics of the samples was evaluated. The thermal stability of the porous network was also evaluated. The introduction of the NbOXA in the silica sol–gel network promoted an increase in pore size diameter and in the total pore volume. The Nb2O5 nanoparticles were well dispersed inside the mesoporous silica matrix and their presence prevented the pore shrinking of the nanocomposite monolith at high temperatures, maintaining the total pore volume of the nanocomposites higher than those of the silica xerogels. To test the availability of the mesoporous nanocomposites as photocatalysts, they were submitted to UV light for methylene blue photobleaching, used as a model waste compound. Only the nanocomposite treated at 900 °C showed morphology and textural proprieties adequate to be photoactive.