Synthesis of Hierarchically Porous Silica and Metal Oxide Beads Using Emulsion-Templated Polymer Scaffolds

Abstract

Uniform, hierarchically porous inorganic beads (SiO2, Al2O3, TiO2, and ZrO2) have been produced using emulsion-templated polymer beads as templates. The polymer scaffolds were prepared by oil-in-water-in-oil (O/W/O) sedimentation polymerization (Zhang, H.; Cooper, A. I. Chem. Mater. 2002, 14, 4017). The inorganic beads were prepared by simply immersing the polymer scaffold beads in a range of inorganic precursor solutions, followed by sol−gel condensation in air and subsequent calcination of the polymer phase. The hierarchical structures are composed of mesopores (diameters 2−5 nm), micropores (in the case of silica beads), and large emulsion-templated macropores of around 5−10 μm. All of the pores are highly interconnected. The inorganic beads exhibit high macropore volumes as characterized by mercury intrusion porosimetry. Polymer−silica composite beads with micropores and high macropore volumes were also produced. These large inorganic beads (diameters 1.0−1.5 mm) are easily handled and separated and m...