Carboxylate-intercalated layered double hydroxides aged under microwave–hydrothermal treatment

Carboxylate-intercalated (terephthalate, TA and oxalate, ox) layered double hydroxides (LDHs) are aged under a microwave–hydrothermal treatment. The influence of the nature of the interlayer anion during the ageing process is studied. Characterization results show that the microwave–hydrothermal method can be extended to synthesize LDHs with anions different than carbonate, like TA. LDH–TA compounds are stable under microwave irradiation for increasing periods of time and the solids show an improved order both in the layers and in the interlayer region as evidenced by powder X-ray diffraction (PXRD), 27Al MAS NMR and FT-IR spectroscopy. Furthermore, cleaning of the surface through removal of some organic species adsorbed on the surface of the particles also occurs during the microwave–hydrothermal treatment. Conversely, although the expected increase in crystallinity is observed in LDH–ox samples, the side-reaction between Al3+ and ox is also enhanced under microwave irradiation, and a partial destruction of the structure takes place with an increase in the M2+/M3+ ratio and consequent modification of the cell parameters.

Graphical AbstractThe influence of the nature of the interlayer anion during the ageing process of carboxylate-intercalated (TA and ox) hydrotalcite-like compounds (HTlcs) is studied. Well crystallized for TA-containing compounds were obtained. However, the non-desired side-reaction of ox with the aluminum of the layers is enhanced by the microwaves and a partial destruction of the structure takes place.Figure optionsDownload as PowerPoint slide