Binary CoOx–SiO2 Porous Nanostructures for Catalytic CO Oxidation.

Via integrative chemistry, the first CoOx–SiO₂(HIPE) self-standing monoliths of cobalt nano-oxides embedded within silica macro–mesocellular hosts have been prepared. These binary CoOx–SiO₂ porous nanostructure (MUB-100-(x)) materials present an average of 95% porosity. We found out that high cobalt concentration maintains the hexagonal-2D organization of the mesoscopic voids when applying the thermal treatment at 700 °C. Their specific surface areas fall between 400 and 500 m² g^–1 when assessed by Ar physisorption measurements. At the microscopic length scale, as revealed through magnetic investigations, the low cobalt content foams MUB-100(1) and MUB-100(2) are made of the amorphous β-Co-(OH)₂ phase coexisting with the silica network, whereas increasing the cobalt concentration during the one-pot syntheses (MUB-100(3) and MUB-(4) materials) favors the formation of the spinel Co₃O₄ and olivine Co₂SiO₄ crystalline nanoparticles embedded within silica. When considering the CO oxidation catalytic performance, the MUB-100(4) is able to totally convert the CO flow before 200 °C (starting at 125 °C) while achieving 50% conversion for a light-off temperature (T₅₀) of 145 °C, revealing the good efficiency of the MUB-100(4) in CO oxidation with which up to 4 catalytic cycles have been performed without disrupting drastically the catalytic performance and reaching thermodynamic stability from cycle 2 to cycle 4. [ABSTRACT FROM AUTHOR]