Preparation and characterisation of layered double hydroxides containing monovalent and divalent ions derived from 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid

Abstract

Mg-Al and Zn-Al layered double hydroxides (LDHs) have been prepared with interlayer monovalent and divalent counter-anions derived from 5-benzoyl-4-hydroxy-2-methoxy benzenesulfonic acid (BHMBS). The divalent ion, in which both the sulfonate and phenolic group are ionized, is readily ion exchanged into nitrate ion form LDHs to give materials with a 13.8 A basal spacing. Preparation of the monovalent ion form LDH (basal spacing 20 Å) by ion exchange is more difficult due to interconversion to the divalent ion within the LDH, and hence is better achieved by an acid-decomposition reaction with a carbonate-ion LDH. The 13.8 A divalent ion phase can be converted post-synthesis to a 15.4 A phase in which the BHMBS has an intermediate valence nature, and which has spectral properties (NMR, IR, UV) that are different from the 13.8 Å and 20 Å phases.