Hybrid inorganic/organic composites of Mg-Al layered double hydroxides intercalated with citrate, malate, and tartrate prepared by co-precipitation

Inorganic/organic composite materials composed of Mg-Al layered double hydroxides (Mg-Al LDHs) intercalated with citrate (C₆H₅O₇^3-), malate (C₄H₄O₅^2-), or tartrate (C₄H₄O₆^2-) anions were prepared by a co-precipitation technique and characterized by X-ray diffraction and compositional analyses. The molecular orientation of the organic component in the interlayer space was determined. At low intercalation levels, citrate ion was inclined at an angle of 26° relative to the brucite-like layers of Mg-Al LDH. At higher solution concentrations, both the Mg(C₆H₅O₇)^- complex and free C₆H₅O₇^3- were isotropically oriented in the interlayer space. For both malate·Mg-Al LDH and tartrate·Mg-Al LDH, the organic anions were inclined at 26° relative to the Mg-Al LDH layers regardless of anion concentration.