Rapid and One‐Step Transformation of LiAlH4 to Inorganic and Organic Anion Intercalated Li‐Al Layered Double Hydroxides

Abstract

Monoclinic [LiAl2(OH)6]OH·2H2O was formed by the hydrolysis of LiAlH4 within few minutes of irradiation with microwaves as confirmed by powder X‐ray diffraction (PXRD), infrared, Raman, 27Al NMR spectroscopic, and thermal analysis experiments. The flaky morphology of crystallites was evident in microscopy images. The compound is mesoporous with surface area of 50 m2/g. When required amounts of corresponding mineral acids were added during the hydrolysis of LiAlH4, exchange of the interlayer hydroxide ion with nitrate and chloride ions was successful. This was verified by the hexagonal symmetry observed in the PXRD patterns together with the evidence gathered from infrared, 27Al NMR spectra, thermal analyses, and the substantial changes in ligand to metal charge‐transfer bands in their UV/Visible spectra. A host of Li‐Al LDH compounds intercalated with aliphatic dicarboxylate (oxalic, malonic, succinic, glutaric, adipic, and sebacic acid) anions were rapidly produced when a mixture of LiAlH4 and the respective acid was irradiated with microwaves for a few minutes. The basal spacing of the dicarboxylate anion intercalated systems increased linearly with the increase in the number of –CH2‐ groups in them. Microwave assisted reaction of ethylene glycol with [LiAl2(OH)6]OH·2H2O resulted in its intercalation.