A Combined Neutron and Synchrotron X-ray Scattering Study of a MgAl-Layered Double Oxide

Owing to their vast chemical and structural flexibility, layered double hydroxides (LDHs) are among some of the most promising materials for many catalytic applications. Thermal decomposition below 700 °C leads to the formation of a complex semiamorphous mixed metal oxide (LDO). In this study, the product of calcination of aqueous miscible organic solvent-treated AMO-[Mg_0.70Al_0.30(OH)₂](CO₃)_0.15·yH₂O·zEtOH at 600 °C (AMO-Mg_2.33Al LDO) has been investigated using a synergistic combination of high-resolution synchrotron X-ray and neutron scattering techniques, as well as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), solid-state NMR (ssNMR), and thermogravimetric analysis coupled with mass spectrometry (TGA-MS). The local and extended structure of AMO-Mg_2.33Al LDO has been modeled by reciprocal and real space X-ray and neutron scattering analyses and is consistent with a modified rock salt structure consisting of octahedrally coordinated layers containing a small number of vacancies and the tetrahedrally coordinated Al³⁺ sites in contrast to previous reports.