LaCoO(3)-based nanocomposites were prepared by an in situ autocombustion procedure of a glycine-nitrate complex in mesoporous silica supports For this purpose two silica supports with different pore sizes (3 0 nm for the HMS-type silica 82 nm for the SBA15-type silica) were prepared The final materials were characterized using XRD TEM N(2)-sorption and reactivities evaluated using oxygen isotopic exchange (OIE) One interesting point is the limited pore plugging due to the low particle size obtained when synthesis is specifically performed in large pore silica support (SBA15) as suggested by the limited pore volume decrease with respect to the HMS-based system TEM coupled with EDXS analyses suggest the formation of crystalline mixed-oxide nanoparticles which have been observed with a cobalt to lanthanum ratio always close to 1 These nanoparticles exhibit high oxygen exchange capacity (1 2-2 3 times higher exchange capacities after 60 min of reaction) albeit a lower initial rate of exchange compared to the bulk reference sample (due to residual carbonate exchange) At the light of these results it has been concluded that this method is efficient for producing nanocrystalline particles dispersed in silica pore structure (C) 2010 Elsevier B V All rights reserved