Revisiting the Synthesis of Gibbsite, a Precursor for Li/Al LDH Synthesis and Its Use as a Support for Porphyrin Immobilization

In this work, some of the synthesis methods already reported for aluminum(III) hydroxide polymorphs with layered structure like gibbsite are revisited. Gibbsite was synthesized with high purity and yield by a simple route developed from modifications of a heating method proposed in the literature, making it possible to prepare gibbsite in regular glassware, avoiding the use of hydrothermal reactor and oven, as described in the literature. The proposed synthesis was conducted with a heating system under reflux conditions in a glass heating flask, using an oil bath, without the need for more sophisticated equipment. This is an accessible alternative method for crystalline gibbsite synthesis, with yield (76 wt.%). The obtained gibbsite was used as a precursor for the synthesis of a lithium/aluminum layered double hydroxide (LDH) from the intercalation method of Al(OH)₃ in aqueous solution of lithium chloride. Gibbsite and the obtained LDH Li/Al were used for the immobilization of an anionic porphyrin with a loading on the order of 10^-5 mol g^-1 of solid, thus being alternative solid supports for catalytic species such as porphyrins.

Keywords:
porphyrin; layered double hydroxide; gibbsite; intercalation; immobilization