Combined In Situ and In Silico Studies of Guest Intercalation into the Layered Double Hydroxide [LiAl2(OH)6]X·yH2O
Phosphonoacetate (PAA), diethyl phosphonoacetate (DPA), and sulfoacetate (SAA) anions have been intercalated into the galleries of the layered double hydroxide (LDH) [LiAl2(OH)6·X]·yH2O (LiAl-X; X = Cl, NO3). X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and elemental microanalysis confirmed the successful intercalation of the guest ions into the LDH. The guests could also be de-intercalated and recovered from the host intact. In situ XRD was used to probe the mechanisms of the reactions, and the intercalation of PAA proceeded via clear intermediate phases. In contrast, the SAA and DPA reactions did not show any intermediates, but the organic intercalates exhibited changes in their interlayer spacing as the reaction progressed. Molecular dynamics (MD) simulations were used to investigate the interlayer structure of the intercalation compounds. It was found that the intermediates observed in situ correspond to local energy minima in the MD simulations. MD can thus predict the course of an intercalation reaction and allow the a priori identification of intermediate phases. This is the first time that in silico and in situ measurements have been combined to unravel this level of understanding of intercalation reactions.