Reactions between a layered aluminophosphate [AlPO4(OH)](C 6H5C2H4NH3) and an nalkylammonium ion [n-propylammonium (C3), n-butylammonium (C4) or n-hexylammonium ion (C6)] were examined. Upon reactions, the X-ray diffraction (XRD) patterns of the products showed changes in the interlayer distance from 1.97 nm to 1.66 nm (AlPO-C3), 1.86 nm (AlPO-C4), and 2.26 nm (AlPO-C6), and the interlayer distance thus increased linearly with increases in the length of the n-alkyl chains. Solid-state 13C nuclear magnetic resonance spectroscopy with cross polarization and magic angle spinning techniques ( 13C CP/MAS NMR) and infrared adsorption (IR) spectroscopy showed that C6H5C2H4NH3+ ions were eliminated and n-CnH2n+1NH3 + ions were introduced. Scanning electron microscopy (SEM) images showed, moreover, that the platy morphology of [AlPO4(OH)](C 6H5C2H4NH3) was maintained upon reactions. These results demonstrate that [AlPO 4(OH)](C6H5C2H4NH 3) underwent ion-exchange reactions with n-alkylammonium ions.