Unique composition-dependent basal expansion of CO3-Cl(H2O) layer double hydroxides

Layer double hydroxides of the form [(CO3)(0.195(1-x))Cl-0.39x(H2O)(y)]: [Zn0.61Al0.39(OH)(2)], 0 less than or equal to x less than or equal to 1, y = 0.4 + 0.2x have been synthesized. Dehydration studies indicate that water in the CO3 end-member (x = 0) is passive while sterically active in the Cl end-member (x = 1). This results from a Cl hydration shell whose water molecules tilt around their C-2v axes when y > 0.51 yielding an anomalously expanded basal spacing of the Cl end-member. The dehydrated system exhibits a unique basal response where the basal spacing is larger for the smaller CO3 ion. (C) 1998 Elsevier Science Ltd. All rights reserved.