Local and long-range cation ordering in ZnAl-NO3 layered double hydroxides

Layered double hydroxides (LDHs) are widely used as metal precursors for heterogeneous catalysts, and their cation distribution strongly affects their physicochemical properties and the homogeneity of mixed metal oxides formed upon calcination. This study investigates cation ordering in nitrate-intercalated Zn₂Al–NO₃ LDHs using powder X-ray diffraction (PXRD) and X-ray absorption spectroscopy (XANES and EXAFS). The results reveal the presence of locally ordered cation domains within the hydroxide layers, even though no long-range cation ordering is detected. These observations demonstrate that local chemical correlations can persist independently of long-range periodicity. The work highlights the complex relationship between local and extended cation ordering in LDHs and underscores the importance of combining diffraction and local spectroscopic techniques to obtain a comprehensive understanding of ordering phenomena in these materials.