Synthesis and morphology control of mesoporous Zr-SiO₂ under mildly acidic conditions

It is not very easy to directly dope Zr into the mesoporous SiO₂.This is due to Zr species are generally difficult to co-condensation with siliceous species and then be co-incorporated into the framework of the SiO₂ under strong acidic conditions. Therefore, a series of mesoporous Zr-SiO₂ were successfully synthesized by a one-step method in the mildly acidic solutions that contain surfactant, hydrochloride acid, zinc acetate, siliceous and zirconium species. Experimental results show that all Zr-SiO₂ samples synthesized with the Zr:Si molar ratio (r) equal to or less than 0.2:1 have the well-ordered mesostructures. The integrity of the mesostructure will decrease if further increase the r to 0.3 or 0.5. When the r in the initial reaction solution changes from 0.01 to 0.2, the cell parameter of the corresponding obtained material increases from 9.7 to 10.9 nm, and the wall thickness of the Zr-SiO₂ sample also enlarges from 1.4 to 2.6 nm, respectively. This confirms that Zr species are incorporated into the framework of mesoporous SiO₂. The morphology of the Zr-SiO₂ can be controlled by the incorporation of different amounts of Zr species. The highly regular fine particles with morphologies such as wormlike, grape-like and wheat grain-like are then obtained for the Zr-SiO₂ samples. The mesoporous Zr-SiO₂ materials present high adsorption abilities in the removal of methylene blue dye from aqueous solutions.