Interlayer surface modification of the protonated ion-exchangeable layered perovskite HLaNb2O7·xH2O with organophosphonic acids

Akira Shimada, Yoriyoshi Yoneyama, Seiichi Tahara, P. Hubert Mutin, Yoshiyuki Sugahara

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Abstract

The interlayer surface of a protonated form of the Dion-Jacobson-type ion-exchangeable layered perovskite, HLaNb2O7· xH2O (HLaNb), has been successfully modified with various organophosphonic acids [phenylphosphonic acid (PhPO(OH)2, PPA) and n -alkylphosphonic acids (n-CnH2n+1-PO(OH)2 with n = 4-18, APAs)] to produce graft-type organic derivatives using an n-decoxy derivative of HLaNb (C10O-HLaNb) as an intermediate. The interlayer distances of the products are changed from that of the intermediate, 2.73 nm, to 2.31 (PPA/C10O-HLaNb) and 2.31-5.26 (APAs/C10O-HLaNb) nm. IR and solid-state 13C CP/MAS NMR spectra of the products reveal that n-decoxy groups are removed and phenyl (PPA/C10O-HLaNb) or n-alkyl groups (APA/C10O-HLaNb) are introduced. Elemental analysis reveals that the amounts of PPA- and APA-moieties are 0.88-0.99 per [LaNb 2O7], corresponding approximately to the amount of the n-decoxy groups in C10O-HLaNb. The environment of interlayer species in PPA/C10O-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/C10O-HLaNb and n-butylamine (-NH2/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 C10O-HLaNb, this reaction is assumed to proceed via the formation of an (HO)NbO5 site and its subsequent reaction with PPA.Alinear relationship is clearly observed between the number of carbon atoms in the n-alkyl chains and the interlayer distances of APAs/C 10O-HLaNb, and a structural model of APAs/C10O-HLaNb with a n-alkyl chain tilt angle of 57° is proposed.

Original languageEnglish
Pages (from-to)4155-4162
Number of pages8
JournalChemistry of Materials
Volume21
Issue number18
DOIs
Publication statusPublished - 2009 Sep 22

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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