Monolithic silica with bimodal pore size distribution fabricated by self-separated sol–gel composite materials

The sol–gel process of tetraethoxysilane involving the simultaneously occurring cationic polymerization of furfuryl alcohol has been used to fabricate large amounts of monolithic silica having hierarchical bimodal pore size distribution with regular arrayed mesopores. In the key step of the sol–gel polymerization a phase separation on micrometer scale takes place and two different poly(furfuryl alcohol)/silica composite material portions are formed. Each phase consists of a poly(furfuryl alcohol)/silica composite of different quantitative elemental compositions as determined by electron probe microanalysis. The final step involves the thermal decomposition of the poly(furfuryl alcohol)/silica composite material at 900 °C. The discovery of the phase separation among the sol–gel process demonstrates that morphological control can be achieved without additional templates, but under limited molar ratio of tetraethoxysilane/furfuryl alcohol used. The specific advantage of this synthesis is that large amounts in the 100 g scale can be produced using this procedure.