Evidence for General Nature of Pore Interconnectivity in 2-Dimensional Hexagonal Mesoporous Silicas Prepared Using Block Copolymer Templates

Abstract

Two-dimensional (2-D) ordered mesoporous silicas were synthesized following the literature synthesis procedures using two different silica sources (tetraethyl orthosilicate and sodium silicate) and poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) triblock copolymer template under acidic and neutral synthesis conditions. The resultant SBA-15 and MSU−H silicas exhibited highly ordered mesoporous structures and pore sizes in the range from 7.5 to 10 nm. The silicas prepared under acidic conditions were clearly microporous, as seen from comparative analysis of adsorption data, whereas the comparative analysis did not indicate microporosity for the silica prepared under neutral conditions. The ordered mesoporous silicas were used as templates for the synthesis of carbon inverse replicas, and in all cases, the 2-D hexagonally ordered mesoporous carbons of CMK-3 type were obtained. This provided a strong evidence that the presence of connecting pores between uniform, ordered, mesoporous channels of 2-D hexagonally ordered silicas synthesized using polymer or oligomer templates with poly(ethylene oxide) blocks is a common feature of such materials and not merely an exceptional behavior restricted to certain SBA-15 silicas prepared under acidic conditions from TEOS.