Cu-doped resorcinol-formaldehyde (RF) polymer and carbon aerogels

Introduction of transition metal salt(s) onto the surface of porous carbons may increase the selectivity and/or efficiency of these adsorbents in catalysis or separation. Carbon aerogels with low pressure drop are particularly suited for these applications. Moreover the sol-gel process used in the synthesis of the resorcinol-formaldehyde polymer gel (RF) precursors offers an extra opportunity for introducing metal ions. Salts of different metals modify both the macroscopic texture and the porosity, depending on the synthesis protocol. In this paper we show, by means of low temperature nitrogen adsorption measurements and SEM, as well as small- and wide-angle X-ray scattering (SAXS and WAXS), how the addition of copper acetate at three different stages influences not only the specific surface area but also the resulting overall structure over a wide range of length scales. Posttreatment in either the polymer or the carbon aerogel stage provides a means of adjusting the copper content. While the Cu-containing carbon aerogels differ mainly in their micropore volume but not in the width of the distribution, their pore size window in the mesopore range can be tuned between 50 and 400 A by the protocol of Cu addition. The synthesis protocol also determines the chemical form of the copper.