Intercalation behavior of n-alkylamines into an A-site defective layered perovskite H2W2O7

Intercalation behavior of n-alkylamines into a protonated form of an A-site defective layered perovskite H2W2O7 has been investigated. Results from XRD indicate these materials are layered with the corresponding interlayer spacing governed by the n-alkylamine chain length, and a reversible intercalation and deintercalation property is observed among these intercalation compounds. The IR spectra of the intercalation compounds with n-alkylamines clearly show that n-alkyl chains possess an all-trans conformation, and H2W2O7 accommodate n-alkylamines (CnH2n+1NH2: n=3, 4, 7, 8, 12, 16) to form intercalation compounds via an acid–base mechanism. A linear relationship between the interlayer distance and the number of carbon atoms in n-alkyl chains is observed to show a bilayer arrangement of the n-alkyl chains with a tilt angle of ∼71.6°. Elemental analysis studies reveal that the amounts of intercalated n-alkylamines are about 2.0 mol per [W2O7]. Despite the surface geometry of H2W2O7 is almost identical to those of layered perovskites H2[An−1BnO3n+1], the amounts of intercalated n-alkylamines of them are different. A reasonable explanation is given through our research.

Graphical abstractH2W2O7 can accommodate n-alkylamines (CnH2n+1NH2: n=3, 4, 7, 8, 12, 16) to form intercalation compounds via an acid–base mechanism. After intercalation, the [001] reflections of H2W2O7 shift to lower angles. The basal space of the intercalation products with n-alkylamines increases with an increase of the number of carbon atoms in n-alkyl chain. The relationship between the interlayer distance, d and the number of carbon atoms in the n-alkyl chain, n, is demonstrated in figure. A linear relationship is clearly observed, as expressed with d=0.241n+0.67.Figure optionsDownload full-size imageDownload as PowerPoint slide