Intercalation of Fe(III) complexes into layered double hydroxides: Synthesis and structural preservation

In this study, intercalation of Fe(III) complexes [Fe(Ox)3]3− and [Fe(Cit)2]3− in Mg2Al layered double hydroxides (LDHs) had been carried out by different routes: direct self-assembly, reconstruction and anion exchange. The result of XRD indicated that these two kinds of Fe(III) complexes intercalated LDHs (LDHs/Fe-complexes) could be successfully synthesized by anion exchange obtaining two well crystallized LDHs both with a large basal spacing. The chemical environment of iron ion in the intercalated Fe complexes was determined by FTIR, XPS and XAFS, the results of which concertedly proved that the intercalated Fe complexes were well preserved in the interlayer of LDHs. The arrangement of the Fe(III) complexes anions in the galleries of LDHs was studied by one-dimensional electron density projection. The results showed that the [Fe(Ox)3]3− anions were probably accommodated in the gallery of LDHs as an interdigitated bilayer arrangement, and the [Fe(Cit)2]3− were perpendicularly arranged against the LDHs sheets. Through the research, it is proved that the obtained LDHs/Fe-complexes markedly enhanced the UV–vis absorption ability of Fe complexes.