SBA-15 versus MCM-41: are they the same materials?

摘要

SBA-15 materials have been used instead of MCM-41 in different applications for the last three years because of their large pores easy to synthesize. Large pore MCM-41 are obtained by adding swelling agents during the synthesis, which gives harder syntheses than SBA-15 due to the use of unstable nanoemulsions. But are SBA-15 the same material as MCM-41 differing only in their method of synthesis? The answer depends on the synthesis temperature of SBA-15. SBA-15 synthesized up to 100℃ possess micropores which lead to an overestimation of their surface areas, whereas higher synthesis temperatures allow to eliminate micropores producing SBA-15 materials with properties close to MCM-41. Proper equations are provided to evaluate the amount of micropores, the true surface area and the true wall thickness. The micropores which interconnect the mesopores in SBA-15 have a strong influence in adsorption measurement, nitrogen adsorption, ~(129)Xe NMR and in surface functionalization.