Control of the pore wall thickness and thermal stability in low-cost bimodal porous silicas

Abstract A new hierarchical bimodal mesoporous silica, labelled as UVM-12 (acronym of University of Valencia Materials), has been prepared by using a solution of sodium silicate as low-cost silicon source. The final self-assembling between cationic micelles of CTAB and anionic inorganic Si-based oligomers occurs in a homogeneous aqueous medium. The reaction is carried out from low-sized building blocks through a bottom-up approach. The UVM-12 solids combine two mesopore systems according to N 2 adsorption-desorption isotherms, what is corroborated by TEM micrographs and XRD patterns. This material has been inorganically modified by incorporation of Al or Ti (M-UVM-12, M = Al, Ti) without alteration of the parent architecture. Moreover, we have carried out a study of the UVM-12 thermal stability by means of N 2 adsorption-desorption and XRD. For comparison, in this analysis we have included other two nanoparticulated bimodal silicas that share structure and morphology with UVM-12 (UVM-7 and UVM-10). Both the mesopore wall thickness and the condensation degree (measured through NMR) in the silica framework of each type of material successfully correlates with the thermal stability of their samples.