Controlling the window size in mesoporous SBA-16.

The structure of the mesoporous silica SBA-16 has been interrogated by careful elimination of the organic templating agent using ozone treatment. It is shown that the as-synthesised material consists of large cages connected by very narrow, ca. 7 Å, windows. These windows open up to about 20 Å following a calcination treatment that suggests that the functionality of SBA-16 could be changed markedly depending upon the post-synthesis treatment. The structure of SBA-16 is compared with surfaces of constant mean curvature. This illustrates that although most of the structure conforms to a surface of constant mean curvature the necks in the structure near the windows deviate strongly. This confirms that attractive forces in this region during synthesis play an important role in shaping the final structure. Following calcination the structure changes as the silica framework relaxes to a constant surface energy.