Synthesis and Characterization of Adipate-pillared LDHs

Layered double hydroxides (LDHs) or hydrotalcite-like materials of the type Mg₁-_xAl_x(OH)₂ (X^n-)_x/n · _zH₂O are most readily prepared when X^n-x is the carbonate ion. Although many other LDHs undergo facile ion-exchange reactions, the carbonate ion in LDHs is known to be very difficult to replace by conventional ion-exchange. We have developed a simple synthesis of adipate-pillared LDHs of the type Mg₄Al₂(OH)₁₂[O₂C(CH ₂)₄CO₂] · 4H₂O by direct reaction of free adipic acid with an LDH carbonate precursor. The materials obtained have been characterized by XRD, FT-IR and DTA. It is shown that by appropriate choice of reaction conditions, the carbonate ions in the precursor can be completely replaced by adipate ions. The adipate-pillared LDHs retain a layered structure with an interlayer distance of 1. 40nm. The interlayer adipate ions are lost on heating the material to 390°C.