Organic and carbon aerogels containing rare-earth metals: Their properties and application as catalysts

Abstract Lanthanide-doped organic and carbon aerogels were obtained based on the modified resorcinol-formaldehyde aerogel preparation procedure. The prepared materials were tested as catalysts for the Michael reaction. Organic aerogels were prepared by sol–gel polymerization of 2,6-dihydroxy-4-methylbenzoic acid (dHMBA) mixed with 5-methylresorcinol (MR) and formaldehyde. The resulting gels were doped with Ln(NO3)3 (Ln = Ce, La, Nd, Pr) by ion-exchange and further dried with supercritical CO2. Pyrolysis of organic aerogels at 900 °C in N2 atmosphere resulted in metal-doped carbon aerogels. The mostly mesoporous materials contained up to 12 wt.% of metal in organic aerogels and 22 wt.% in carbon aerogels. The materials were amorphous and crystal structures were not formed during pyrolysis. Ln-doped aerogels were tested as catalysts for Michael addition reaction. Organic aerogels doped with different lanthanides catalyze the Michael reaction efficiently with conversions ranging between 82 and 97% in 24 h. For Ln-doped carbon aerogels the conversion was modest (32%) to high (92%).