Formation of mesoporous Co₃O₄ replicas of different mesostructures with different pore sizes

Mesoporous metal oxides Co₃O₄ are prepared via hard templating synthesis method by using various mesoporous silicas with different pore size as templates. The pore size of the mesoporous silicas with the symmetry of two-dimensional (2d)-hexagonal p6mm, bicontinuous cubic Ia over(3, ̄) d and Pn over(3, ̄) m have been controlled in the range of 6.6-10.7, 4.2-7.5 and 5.1-6.7 nm, respectively, by choosing different surfactants and co-surfactants and by adjusting either the aging temperature or the ionization degree of the surfactant. The pore size of the silica template has been considered to be an important factor that determines the mesostructure of the resulting metal oxides. It has been found that for p6mm, it is easier to replicate the mesoporous symmetry at large size of mesopores. For Ia over(3, ̄) d, at large-pore size two sets of bicontinuous meso-channels are replicated into mesoporous Co₃O₄, while small-pore Ia over(3, ̄) d leads to replication of both one set and two sets of meso-channels. Co₃O₄ can replicate both one set and two sets of bicontinuous Pn over(3, ̄) m meso-channels at all pore sizes that can be obtained (5.1-6.7 nm), indicating the existence of ordered complementary micropores within the silica walls.