Boric acid assisted formation of mesostructured silica: from hollow spheres to hierarchical assembly

Abstract

A boric acid assisted assembly approach has been provided to prepare mesostructured silica with various morphologies and porosities. The hollow siliceous spheres with ultrasmall size (∼15 nm) can be synthesized under an ultra-dilute CTAB/P123 surfactant concentration, with TEOS as the silica source in a weak acid system. It was also found the ratio of CTAB/P123, the concentration of boric acid and surfactant, the amount of TEOS and the addition of MgSO₄ had key roles in controlling the morphologies and porosities. The obtained mesostructure silica possessed ordered structure, uniform morphologies (hollow sphere, tubular and cage-like mesoporous silica), high surface area (304.2–742.0 m² g⁻¹), tunable large pore volume (0.55–2.07 cm³ g⁻¹) and pore size distribution (2.2–11.8 nm).