New Attempt at Directly Generating Superbasicity on Mesoporous Silica SBA-15

Abstract

Direct generation of superbasicity on mesoporous silica SBA-15 was realized by tailoring the host-guest interaction, and calcium species were selected as the guest in modifying SBA-15. The results show that calcium species could be homogeneously distributed on the surface of SBA-15. Because of the host-guest interaction, the decomposition of the supported calcium nitrate was apparently easier than the bulk one. Surprisingly, the calcium nitrates modified SBA-15 (CaNS) samples exhibited superbasicity with good preservation of the mesostructure after activation, differing from the potassium nitrate loaded SBA-15 samples that displayed weak basicity with collapsed mesostructure. The present superbasic CaNS materials also possess good water resistance and high surface areas, up to 429 m(2) g(-1), which is promising for their potential applications in adsorption and catalysis. Further investigation concerning the roles played by the guest in basicity formation on SBA-15 was conducted. The samples modified by Group 2 metal nitrates showed strong basicity with base strength (H-) of 22.5-27.0 and good preservation of mesostructure. In contrast, loading Group 1 metal nitrates on SBA-15 produced samples with weak basicity ( H-=9.3-15.0) and collapsed mesostructure after activation. Such differences can be related to the interaction between the resulting metal oxide and the silica support, as well as the mobility of the cations in the metal oxide.