Monolithic tin oxide aerogels synthesized using the epoxide technique were characterized with X-ray diffraction, diffusive reflectance spectroscopy, infrared spectroscopy, particle induced X-ray emission and photoluminescence. Our results indicate that the resulting aerogel is an electrical semi-insulator. This happens due to an incomplete chemical reaction that leaves chloride and hydroxide ions unreacted. These ions form complexes with oxygen vacancy sites producing electron trapping. Furthermore, ions of Cu, Zn and Fe were identified as naturally occurring impurities in the gel matrix, substituting Sn+4 ions. •High surface area tin oxide aerogel was grown using the epoxide technique.•We study the electronic structure of the material using spectroscopy and photoluminescence.•The absence of electrical conductivity is a consequence of high electron trapping.•Ions of Cu, Fe and Zn were identified by PIXE as naturally occurring impurities.