Synthesis of bimodal mesoporous silica with coexisting phases by co-hydrothermal aging route with P123 containing gel and F127 containing gel

Abstract

Bimodal mesoporous silica materials with two coexisting phases were synthesized by co-hydrothermal aging (CHA) route. During the CHA process separately prepared P123 containing gel and F127 containing gel were mixed and the mixture underwent the hydrothermal aging together. The silica obtained through co-hydrothermal aging (CHAS) were characterized by XRD, N2 adsorption-desorption, TEM and SEM. CHAS was compared with the silica synthesized with the mixed templates (P123 and F127) through classic liquid crystalline templating route (LCTS). LCTS shows the regular mono-modal cylindrical mesopore, while CHAS shows obvious coexisting semi cubic arranged inkbottle small mesopores (2–5 nm) and hexagonal arranged cylindrical large mesopores (3–7 nm). Effects of synthetic conditions including the stirring time, the pH value and the mass ratio of P123 to F127 were studied in detail. It is found that CHAS can be synthesized within a wide range of stirring time before the mixing of the gels but too long stirring time after mixing will make the pore distribution of CHAS become wide. The mass ratio of P123 to F127 is an effective way to tailor the pore parameters of CHAS. The pH value control (below 3.0) is crucial for the formation of the bimodal mesoporous structure. The synthesis mechanism of the CHAS was suggested, the reaction step in the CHA process is decisive on the pore size of CHAS and the co-hydrothermal aging plays the key role in the formation of CHAS, in this step two phases were weaved together.