A series of iron-containing mesoporous silicas (Fe-HMS) with Fe contents up
to 5.7 wt.% have been prepared at room temperature using the neutral hexad
ecylamine as surfactant molecule. Characterization of these materials by a
variety of spectroscopic techniques, including EXAFS, EPR, Mossbauer and UV
-Vis spectroscopies, suggests that Fe species are tetrahedrally coordinated
in as-made materials. Tetrahedra are highly distorted with two long and tw
o short Fe-O bond distances due to hydrogen-bonding type interactions with
the organic molecules. Removal of the amines by solvent extraction does not
modify the chemical environment around the Fe species. Subsequent calcinat
ion leads to mainly 3-coordinated Fe species, readily converting to 4-coord
inated species in the presence of water. The solvent extraction appears to
be a key step to prevent the formation of extraframework iron oxide species
, which are formed in large amount when the surfactant is directly removed
from as-made materials by calcination in air at high temperature.