Intercalation of carboxymethyl-β-cyclodextrin into magnesium–aluminum layered double hydroxide†

Abstract

New intercalated compounds have been prepared by incorporating carboxymethyl-β-cyclodextrin (CMCD) into magnesium–aluminum layered double hydroxide (Mg/Al LDH). The sorptive uptake of CMCD(3) and CMCD(14), with a degree of carboxymethyl substitution of 3 and 14, respectively, by Mg/Al LDH was examined at 65 °C, and the resulting complexes were characterized using X-ray diffraction (XRD) and FT-IR spectroscopy. Results indicated that Mg/Al LDH retained approximately twice as much CMCD(3) as compared to CMCD(14). Results of XRD and FT-IR spectroscopy confirmed that both CMCD(14) and CMCD(3) could be intercalated into Mg/Al LDH interlayers due to an ion-exchange process. After exposure to CMCD(14) and CMCD(3), the d-spacing of Mg/Al LDH expanded from 8.74 to 15.48 and 20.63 Å, respectively. Intercalated CMCD(14) molecules formed monolayer coverage in the Mg/Al LDH interlayers, with the cavity axis perpendicular to the LDH layer, while CMCD(3) molecules adopted either a parallel-monolayered arrangement or a perpendicular-bilayer-like coverage. Both CMCD(14) and CMCD(3) molecules were believed to be loosely packed within the Mg/Al LDH interlayers.