Preparation of inorganic–organic composites as acid–base catalysts using HCa₂Nb_3−xTa_xO₁₀ and quaternary onium salts

Abstract

Inorganic–organic composites have been prepared using Dion–Jacobson-type layered perovskite compounds as base catalysts. Dodecyltributylphosphonium bromide (C₁₂TBPBr), dodecyltriphenylphosphonium bromide (C₁₂TPPBr), or dodecyltrimethylammonium chloride (C₁₂TMACl) were used as the organic species of the inorganic–organic composite. It was suggested that C₁₂TBP⁺, C₁₂TPP⁺, or C₁₂TMA⁺ were intercalated by ion-exchange with interlayer H⁺ of HCa₂Nb₃O₁₀. The acid–base reaction was evaluated by consecutive deacetalization–Knoevenagel reactions. The product of the second-step reaction of the inorganic–organic composite catalysts was obtained, which suggested that the composites were acid–base bifunctional materials. For composites prepared using HCa₂Nb_3−xTa_xO₁₀ (x = 1, 2, and 3) as inorganic species, the base catalytic activity decreased with decreasing fraction of organic species. Therefore, the hydrophobicity of the layered compounds affected the catalytic activity of the composite. Various catalysts should be prepared using reported layered perovskite-type compounds having various compositions.