Ordered hexagonal mesoporous silica materials (SBA-15) with additional disordered large-mesopore networks formed by gaseous expansion

Abstract

Ordered hexagonal mesoporous silica materials with additional disordered large-mesopore networks (DL-SBA-15s) have been prepared by one-pot process using urea as a producer of gas. Combined characterizations of XRD, SEM, and TEM techniques show that DL-SBA-15s not only have ordered 2D hexagonal mesopores (about 10 nm) similar to SBA-15, but also have another disordered large-mesopore network (about 20 nm) interconnected with hexagonal mesoporous channels, which are confirmed by nitrogen isotherms. The ordered hexagonal mesopores are templated by polymer surfactant micelle, and disordered large-mesopores are formed by gaseous expansion due to the decomposition of urea added in the silica gel. 29Si MAS NMR and FT-IR spectra show DL-SBA-15s have high degree of silica condensation and low silanols on the surface, compared with SBA-15. Furthermore, we have compared the adsorption capacity of myoglobin over conventional SBA-15 and DL-SBA-15 samples, and the results show that DL-SBA-15s exhibit much higher adsorption rate than conventional SBA-15 due to the presence of additional disordered large-mesopore networks and larger pore volume, which is potentially important for immobilization of enzymes on ordered mesoporous materials.