Thermal behaviors and grafting process of LDH/benzene derivative hybrid systems

Thermal behaviors of four hybrid layered double hydroxide (LDH) phases have been studied by thermogravimetric analyses coupled with mass spectroscopy, temperature dependence of X-ray powder diffraction measurements, and temperature dependence of infrared spectroscopy measurements. Inorganic zinc–aluminium LDH main layers (with a Zn2+/Al3+ cationic ratio of 2) inserted the following four organic anions: benzene carboxylate, 4-hydroxy-benzene carboxylate, benzene sulfonate and 4-hydroxy-benzene sulfonate. The four LDH hybrids have been synthesized by the coprecipitation method. The as-prepared samples have been characterized and their compositions were determined. Thermal evolution of the crystalline phases during the dehydration (occurring before 200 °C) and the dehydroxylation (occurring between 200 and 300 °C) gave evidence for organic anion grafting onto the inorganic main layer. The thermal stability of the LDH hybrid system depends on the nature of the intercalated aromatic anion. The thermal grafting process can be monitored, as well as its thermal reversibility, by choosing the functionalizations of the benzenic anion and the temperature of the applied heat treatment.

► Orientation of the organic entities between the layers of the mineral network.
► Influence of the organics functional group on the stability of the hybrid material.
► Demonstration of three different behaviors in terms of the grafting process.