Nb2O5/SiO2 monoliths with tailored porosity: the role of polyethylene glycol as pore modulating agent

The role of polyethylene glycol (PEG) as pore modulating agent was studied in the preparation of monoliths formed by Nb2O5 nanoparticles dispersed in a silica matrix obtained by the sol–gel process. The obtained monoliths were characterized by gas adsorption, SEM and HRTEM (EELS coupled). The silica and nanocomposite monoliths showed high specific surface area and pore size varying between micro and macropores, depending on the amount of PEG used. The silica monoliths were transparent due to the micro and small mesopores, the nanocomposites with 1 and 5% of PEG were translucid and the nanocomposite with 3% of PEG were opaque due to spinodal decomposition induced by the interaction between the polymer and the niobium pentoxide precursor (ammonium niobate oxalate hydrate), which made it a promising candidate for flow catalysis or chromatographic columns.