An alkaline route to prepare hydrothermally stable cubic Pm3n mesoporous silica using CTEA template

Cubic Pm3n mesoporous silica isomorphous to SBA-1 with three-dimensional inter-connected pore structures was prepared for the first time in alkaline condition (pH around 9) using sodium silicate as the silica source and cetyltriethylammonium (CTEA+) bromide as pore-directing agent with the aid of NaCl salt. In contrast to the conventional SBA-1 material prepared in the acidic environment, the mesostructure of the cubic Pm3n material, designated SBA-1-alk, was stable toward washing with water and hydrothermal treatment. The high stability is due to that the silicate condensation is more complete under the alkaline condition. The chemical forces governed the assembly of the surfactant and silicate in the alkaline condition was probed by pyrene fluorescence technique to be an S+I− type interaction. Moreover, the direct metal incorporation into the silica framework became very efficient through this alkaline route. The SBA-1-alk isomorphously substituted with Al(III) was found an efficient catalyst for the alkylation of 2,4-di-tert-butylphenol by cinnamyl alcohol to form flavan.