Porous organic and carbon xerogels derived from alkaline aqueous phenol–formaldehyde solutions

Abstract

Porous carbons were synthesized from the low cost precursors phenol and formaldehyde in aqueous solution, catalysed with NaOH. The xerogels were ambient pressure dried without prior solvent exchange. For an excess of formaldehyde, the resulting carbon xerogels show porosities up to 90%, with a predominant fraction of macroporosity, specific surface areas up to 768 m2/g and mesopore volumes up to 0.59 cm3/g. Small-angle X-ray scattering reveals fractal behaviour for many samples. Relevant sodium impurities up to 3–4 wt% in the organic and carbon samples cannot be avoided, even by washing of the samples. As possible reason for the high sodium content, the formation of crown ether like calix [6] arene is assumed. Overall, the sodium impurities detected confine the use of this system to applications, where higher ash contents are uncritical.