Synthesis of organic and carbon aerogels from phenol–furfural by two-step polymerization

An improved method of preparing phenol–furfural aerogels and related carbon aerogels was developed by dividing the sol–gel polymerization into two steps, i.e., the formation of gel precursors by prepolymerizing phenol and furfural with NaOH as a catalyst and subsequently the gelation of the precursors with HCl as a catalyst. The role of the cross-link density of the gel precursors in the preparation process was studied by investigating its effects on the yield, the drying shrinkage, the bulk density and the texture of organic and carbon aerogels obtained here. It was found that a proper increase in the cross-link density of the gel precursors by prepolymerizing with NaOH as a catalyst helps to increasing the yield of organic and related carbon aerogels but leads to an increase of the bulk density of organic and carbon aerogels. The nano-particle size and mesoporosity of organic and related carbon aerogels can be improved by an appropriate increase in the cross-link density of the gel precursors. But, the organic aerogels with a NaOH-catalyzed prepolymerization process (NCPP) experience a larger drying shrinkage than those without the NCPP.