Tuning of textural properties of mixed metal oxides by changes in anionic composition of hydrotalcite-like precursors

Benzoate anions were introduced into the interlayer space of Mg–Al, Mg–Ni–Al and Mg–Cu–Al hydrotalcite-like compounds. The structure of the obtained samples was studied by XRD and UV–vis-DR spectroscopy. Differences in an orientation of the interlayer anions influenced by the cationic composition of the brucite-like sheets were observed. The mechanism of thermal decomposition of layered double hydroxides intercalated with benzoates was examined by thermal analysis methods (TG-SDTA-EGA). It was found that the thermal treatment of the hydrotalcite-like materials containing organic anions led to a formation of mixed metal oxides characterized by a very uniform pore size distribution. Moreover, these materials exhibited the BET surface area significantly higher compared to the calcined Mg–Al–CO3 hydrotalcite. The generation of the uniform porosity was strongly promoted by a modification of the starting layered structure with transition metal cations (Ni2+ and Cu2+). This effect was attributed to a catalytic role of transition metal cations in the burning of interlayer organic species. CO2 and H2O formed during the removal of the interlayer anions were found to be responsible for an improvement of textural properties of the hydrotalcite-derived samples.