The interlayer surface of a protonated form of the Dion-Jacobson-type ion-exchangeable layered perovskite, HLaNb 2 O 7 3 xH 2 O (HLaNb), has been successfully modified with various organophosphonic acids [phenylphosphonic acid (PhPO(OH) 2 , PPA) and n-alkylphosphonic acids (n-C n H 2nþ1 -PO(OH) 2 with n = 4-18, APAs)] to produce graft-type organic derivatives using an n-decoxy derivative of HLaNb (C 10 O-HLaNb) as an intermediate. The interlayer distances of the products are changed from that of the intermediate, 2.73 nm, to 2.31 (PPA/C 10 O-HLaNb) and 2.31-5.26 (APAs/ C 10 O-HLaNb) nm. IR and solid-state 13 C CP/MAS NMR spectra of the products reveal that n-decoxy groups are removed and phenyl (PPA/C 10 O-HLaNb) or n-alkyl groups (APA/C 10 O-HLaNb) are introduced. Elemental analysis reveals that the amounts of PPA-and APA-moieties are 0.88-0.99 per [LaNb 2 O 7 ], corresponding approximately to the amount of the n-decoxy groups in C 10 O-HLaNb. The environment of interlayer species in PPA/C 10 O-HLaNb is assumed to be monodentate PhPO(OH)(ONb) based on the IR results (the P-O stretching and P-OH stretching bands at ∼1030 and ∼950 cm -1 ) and the reaction between PPA/C 10 O-HLaNb and n-butylamine (-NH 2 /POH=1.0). Scanning electron micrographs of the products reveal that the morphology is clearly preserved during the reactions with PPA or APAs, indicating that they are graft-type rather than dissolution-recrystallization-type reactions. Because water is required for the reaction between PPA and C 10 O-HLaNb, this reaction is assumed to proceed via the formation of an (HO)NbO 5 site and its subsequent reaction with PPA. A linear relationship is clearly observed between the number of carbon atoms in the n-alkyl chains and the interlayer distances of APAs/C 10 O-HLaNb, and a structural model of APAs/C 10 O-HLaNb with a n-alkyl chain tilt angle of 57°is proposed.

Triethylphosphine oxide [(C2H5)3P[double bond, length as m-dash]O; TEPO] was intercalated into protonated Dion-Jacobson-type ion-exchangeable layered perovskites, HLaNb2O7·xH2O (HLaNb) and HCa2Nb3O10·xH2O (HCaNb), by hydrolysis of their n-decoxy derivatives (C10O-HLaNb or C10O-HCaNb) in the presence of TEPO. The interlayer distances of the products (TEPO/C10O-HLaNb and TEPO/C10O-HCaNb) were smaller than those of the corresponding n-decoxy derivatives, but still larger than those of anhydrous protonated forms of HLaNb and HCaNb. The solid-state (31)P NMR signals of the products observed at 94 ppm (TEPO/C10O-HLaNb) and 93 ppm (TEPO/C10O-HCaNb) exhibited large downfield shifts from that of the physisorbed TEPO. IR spectroscopy also showed decreases in the ν(P[double bond, length as m-dash]O) band wavenumbers upon the reactions. These results clearly indicate that TEPO is intercalated and interacted with Brønsted acid sites, the surface hydroxyl groups generated via hydrolysis of n-decoxy groups. The difference in ν(P[double bond, length as m-dash]O) band wavenumbers as well as that in gallery heights suggests that TEPO exhibited different orientations with respect to the inorganic layers. The chemical shifts of solid-state (31)P NMR signals suggested high Brønsted acidity of HLaNb and HCaNb.