SBA-15 templated mesoporous carbon: New insights into the SBA-15 pore structure

This work used a combination of designed synthesis conditions for SBA-15 to gain new insights into the genesis of micropores and secondary mesopores bridging the primary mesoporous channels. Different SBA-15 samples were prepared at low temperature (35 and 60 degrees C) without stirring to generate a simple monodispersed rodlike morphology. Sodium chloride was used to control the occurrence of micropores. All samples were used as templates for the synthesis of CMK-5 type (nanopipes) of porous carbons via carbonization of occluded poly(furfuryl alcohol). Detailed characterization of the silica templates, the carbon/silica composites, and the nanoporous carbons led to the following main conclusions: (i) Combination of inorganic salts with low synthesis temperature (ca. 35 degrees C) afforded SBA-15 silica free of micropores and secondary mesopores, akin to MCM-41. The corresponding carbon was fibrous in nature and did not retain the rodlike morphology of the template; (ii) the microporous as well as mesoporous bridges connecting the primary mesoporous channels of SBA-15 occur at temperatures as low as 60 degrees C. As the synthesis temperature increases, the microporous bridges tend to vanish, whereas the mesoporous bridges become more abundant. The corresponding carbon nanopipes, and by inference nanorods, exhibited the same morphology as the template.