Formation of Cubic Ia3d Silicas and Metal Oxide-Loaded Silicas Using a Triblock Copolymer (EO₂₀PO₇₀EO₂₀)−Acetate Mixture as Structure Director in Aqueous Solution

Mesoporous silica with Ia3d structure has been successfully prepared utilizing a triblock copolymer (EO₂₀PO₇₀EO₂₀)−acetate mixture for structure direction in aqueous solution over a wide pH range, even above the isoelectric point of silica, where the pH value could be finely tuned by varying the concentration of HCl and/or acetate. Characterization by XRD, TEM, and N₂ sorption measurements show that the cubic Ia3d materials possess high surface areas (about 900 m²/g), large pore volumes (about 1.2 cm³/g), and uniform pore diameters (about 9.2 nm). Further, the phase diagram in the SiO₂−P123−ZnAc₂−H₂O−HCl system is drawn to map the range of cubic mesophase. Salt effect has been investigated during the phase transformation process, which reveals that the nature and concentration of cations can also determine the mesostructure. In addition, when two different acetates are introduced into the solution at one time, metal oxides-modified cubic mesoporous silica can be directly synthesized. Among others, copper-modified cubic samples, prepared by this direct method, display superior properties in the NO₂-TPD experiments. The lower acid concentration in the acetate-modulated synthetic system favors the direct incorporation of metal oxide species and this discovery may offer us a new perspective to better understand the formation mechanism of ordered mesoporous materials.