Investigating the state of Fe and La in MCM-41 mesoporous molecular sieve materials

Fe-containing, La-containing, siliceous and aluminum silicate MCM-41 mesoporous materials were synthesized using water glass as silica source. The states of Fe(III) and La(III) species were investigated by thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), framework infrared (FTIR), electron spin resonance (ESR) and Mössbauer spectroscopic techniques. It was shown that Fe(III) or La(III) species was incorporated into framework. Because the Fe–O or La–O bond is longer than Si–O bond, Fe(III) or La(III) species was limited to insert into framework and transformed from tetrahedrally coordinated state to octahedrally coordinated state upon calcination to remove template.