Sorption of divalent Fe, Co, Ni, and mixed-valent Fe into mesoporous silica grafted with an aminopropyl group, and their adsorption properties

A reflux process was carried out for hybridization of aminopropyl-grafted mesoporous silica and metal cations at 110 and 140°C. For the sample hybridized with Fe2+, Co2+ and Ni2+, magnetite, Co2(OH)3Cl, and Ni2(OH)2CO3·4H2O particles of approx. 5-30 nm in diameter were formed. The amount of metal compounds was approx. 9-12 mol%. These compounds formed a porous aggregate on the outer surface of the mesoporous silica particles. For the hybrid with Fe2+ and Fe3+, magnetite approx. 3 nm in diameter formed not only on the outer surface but also within the mesopores derived from the mesoporous silica. The amount of magnetite achieved approx. 30 mol%. This hybrid shows an O2 adsorption property three times as high as the other samples. These results demonstrate that nanoscale magnetite shows significant O2 adsorption competence at room temperature.