Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2–5 nm-thick tactoids with a radial dimension of 0.2–0.5 μm.