Nondestructive immobilization of cobalt and copper Schiff base complexes in silica aero-
and xerogels was achieved via the sol−gel method using a precursor N,N‘-ethylenebis(salicylidenaminato) (salen) ligand modified with pendant silyl ethoxy groups. Aerogels were
obtained by semicontinuous extraction of the wet gels with supercritical CO2 and xerogels
by conventional drying. Cobalt and copper(salen) containing silica gels were characterized
by FTIR, UV−vis, and XPS spectroscopy, laser ablation-ICP-MS, and EPR studies. Aero-
and xerogel incorporated salen compounds exhibited similar spectroscopic properties to cobalt/copper(salen) precursors and known metal(salen) compounds. BET measurements confirmed
the importance of supercritical CO2 drying in maintaining the mesoporous structure of the
aerogel. Laser ablation-ICP-MS and EPR studies of the aerogels showed that a uniform
distribution of the isolated metal(salen) complex was achieved via molecular mixing using
the sol−gel method. Stability of these materials was demonstrated by thermogravimetric
analyses in air and leaching studies conducted under typical liquid-phase oxidation
conditions. XPS analyses showed surface relative atomic concentrations in the modified gels
to be similar before and following leaching studies.
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