Effects of Cu2+ incorporation on ZnAl-layered double hydroxide

Abstract

To investigate the structural properties of Cu²⁺-incorporated ZnAl-layered double hydroxide, a series of CuZnAl-layered double hydroxides with various molar ratios was prepared by the constant pH co-precipitation method. The composition, structure and morphology of the synthesized products were analyzed by using XRD, SEM, TEM, FTIR, XPS and ²⁷Al–¹H MAS-NMR techniques. The results show that all samples with or without copper present crystalline LDH with a flower-like architecture, and no other impurity was observed. The interesting observation of the study was that the incorporation of copper influences the coordination number of aluminum. Comparing with the ZnAl-LDH layers, which contained only ZnO₆ and AlO₆ octahedra, in the Cu-containing LDH layers, in addition to CuO₆, ZnO₆, and AlO₆ species, the AlO₄ species is clearly observed. A simplified explanation for the formation of AlO₄ species is associated with the Jahn–Teller effect of copper. These results suggest that there are structural defects (Al–O–Al connectivities) in the form of AlO₄ species in the Cu-containing LDHs.