FORMATION OF A METHOXY-MODIFIED INTERLAYER SURFACE VIA THE REACTION BETWEEN METHANOL AND LAYERED PEROVSKITE HLANB2O7-CENTER-DOT-XH(2)O

The reactions between methanol (CH3OH, CH3OD, CD3OD, (CH3OH)-C-13) and layered HLaNb2O7 . xH(2)O were investigated. X-ray powder diffraction (XRD) analysis showed that a peak corresponding to the basal spacing of HLaNb2O7 . H2O (1.05 nm) disappeared and a new peak appeared at 1.1 8 nm. Carbon-13 NMR spectra revealed the presence of two environments of the methyl group; the broad 67 ppm signal is ascribed to the rigid species located in the interlayer space, and the 50 ppm signal is ascr ibed to mobile methanol on the external surface. The amount of the lat ter species was negligibly small. Deuterium NMR spectra revealed the p resence of a Pake doublet with an effective quadrupole coupling consta nt (QCC) of 47 kHz and an asymmetry factor (eta) of zero, indicating t hat the CD3O group was rigidly bound to the interlayer surface. In add ition, when both CD3OD and CH3OD were used, no signal corresponding to the OD group was observed. Hence, although XRD results can be interpr eted as intercalation of methanol, the H-2 NMR results indicate that m ethanol was dissociatively adsorbed to the interlayer surface. The obs erved very high thermal stability of the methyl group is consistent wi th methoxy formation. The structure of the product is discussed on the basis of the results with larger n-alcohols.