Layered double hydroxides with low Al content and new intercalate structures

Layered double hydroxides (LDHs) containing Mg2 + and Al3 + as divalent and trivalent cations, respectively, have been synthesized by a procedure based on hydrolysis of a mixture of metal alcoholates, and have been characterized mainly by Wide Angle X-ray diffraction (WAXD) and Fourier Transform Infrared (FTIR) measurements. The used procedure is suitable to prepare LDHs with Al molar fractions, xAl = Al/(Al + Mg), as low as 0.1. The same LDH preparation procedure, for xAl < 0.1, produces thermally stable intercalates with alkoxy anions, exhibiting layers similar to those of brucite, which maintain a high degree of order only in the hexagonal packing of the hydroxide groups. In particular, the basal periodicity increases from nearly 0.8 nm up to nearly 1.3 nm, due to the parallel staking of hexanolate groups in the clay galleries.

► LDHs with Al molar fractions as low as 0.1, by hydrolysis of metal alcoholates. ► Intercalates with hexanolate anions and dbasal = 1.3 nm, for low Al content. ► Intercalates with high degree of order only in the packing of the hydroxides. ► Intercalates stable up to nearly 530 K.