Experimental and theoretical study on the structure of acid orange 7-pillared layered double hydroxide

Acid orange 7-pillared layered double hydroxide (AO7-LDH) has been prepared by coprecipitation and studied with both experimental characterizations and theoretical calculations. XRD patterns indicate that the product has the typical intercalated structure of LDHs with a gallery height of 1.79 nm, showing that a kind of large anion has been intercalated into the interlayer space of the LDH. Infrared spectrum of AO7-LDH shows that the product has the characteristic absorption bands of both azo and hydrazone forms of AO7 anion, as well as the Mg–O and Al–O vibrations of LDH layers, well convincing the intercalation of AO7 anions successful. TG–DTA curves demonstrate clearly that the thermal stability of AO7 can be enhanced by nearly 130 °C when it is intercalated into the LDH layers. According to the size of AO7 anion (1.25–1.27 nm) obtained by density functional calculations of quantum chemistry at the level of B3LYP/6-31G(d,p), the AO7 anions should be vertical-arranging in the interlayer space, forming a interdigitated structure.