Large-pore mesoporous silica with three-dimensional wormhole framework structures

Abstract

Large-pore mesoporous silica with 3D wormhole framework structures (denoted MSU-J) are prepared through a supramolecular hydrogen-bonding assembly pathway from low-cost sodium silicate as the silica source and commercially available mono- and tri-amine Jeffamine and Surfonamine surfactants as structure-directing porogens. The calcined mesostructures exhibit large pore sizes (up to 8.2 nm), surface areas (632–1030 m 2/g) and pore volumes (0.5–2.0 cm 3/g), depending on the surfactant chain length and synthesis temperature (25–65 °C). The textural properties of these new wormhole mesostructures are comparable to those of hexagonal SBA-15 derivatives and large pore MCM-48. However, unlike the SBA-15 structure type, wherein the 3D pore network is formed by connecting 1D cylindrical mesopores through micropores, MSU-J mesophases have wormhole framework structures containing fully interconnected 3D mesopores that can minimize the diffusion limitations often encountered in adsorption and chemical catalysis. Also, unlike large pore MCM-48, which requires cost-intensive tetraethylorthosilicate as a silica source and the use of a co-surfactant as a pore expander under strong acid conditions, MSU-J mesostructures are assembled from low-cost sodium silicate in the presence of a single Jeffamine or Surfonamine porogen at near-neutral pH.