Synthesis of ordered nanoporous carbons of tunable mesopore size by templating SBA-15 silica materials

Abstract

Ordered mesoporous carbons with controllable pore size distributions were synthesised by using mesostructured SBA-15 silica samples as templates. By varying the synthesis temperature of SBA-15 between 90 and 150 °C, it is possible to tune the size of silica mesopores between 7.2 and 11.3 nm. As the synthesis temperature of SBA-15 silica increases over this range, the size of the mesopores of templated carbons can be modified between 3.0 and 5.2 nm. Modification of the synthesis temperature of silica does not affect its structural order, which is that characteristic of SBA-15. Independent of the type of SBA-15 used as template, the prepared carbons are highly ordered. The porosity of the carbons synthesised from SBA-15 silica in one impregnation–carbonisation (N 2) cycle is made up of two types of mesopores, i.e. structural mesopores (derived from the silica skeleton) and mesopores confined within the carbon rods. The structure of a carbon with these characteristics is described by the CMK-3/5 model, which is presented here for the first time. When the impregnation–carbonisation cycle is repeated twice, the carbon rod confined mesopores disappear and the structure of the resulting carbon is well described by the CMK-3 model.