Inclusion of alkali carboxylate salts at the two-dimensional space of layered alkali titanate via carboxylic acids intercalation

Abstract

The formation of organic salts trapped at the two-dimensional (2D) space of layered solids is typically not well-defined, lacks stoichiometric relation, and depends on the chain length of the organic moieties. In contrast to this conventional salt intercalation, we report herein the inclusion of alkali carboxylates by intercalation of carboxylic acids to lepidocrocite-type alkali titanate microcrystals. The intercalated organic content of 15.9–37.0 ​wt% is high for a solid with low specific surface area (3 ​m2/g). A small interlayer expansion (~0.7 ​Å) was observed with decanoic, palmitic, and sebacic acids which form the trapped carboxylate salts. Meanwhile, acetic acid produced a typical protonic titanate as with mineral acids. The inclusion of carboxylate anion and the accompanying carboxylic acid spectator was proven by their characteristics IR vibrations. Using K0.8MyTi2-yO4 (M ​= ​Zn, Ni, Co, Fe, Mg, Li), we showed that the host-guest, acid-base interaction influenced the thermal decomposition of the intercalated species. A correlation was observed between the partial charge at the O atom (normalized by the intercalate content) vs the decomposition temperature of the trapped species. The formation of sodium carboxylates similarly occurred with sodium titanate nanotubes.