Selective anion-exchange properties of second-stage layered double hydroxide heterostructures

The anion-exchange properties of second-stage [Zn2Cr(OH)(6)]Cl-0.5(succinate)(0.25)(.)nH(2)O (Zn2Cr-Succ/Cl) and [Zn2Cr(OH)(6)]Cl-0.5(tartrate)(0.25), nH(2)O (Zn2Cr-Tart/Cl) materials were investigated by means of time-resolved in situ energy-dispersive X-ray diffraction (EDXRD). Selective anion-exchange reactions were observed that were a result of the segregation between organic and inorganic anions. Indeed, the reaction of Zn2Cr-Succ/Cl and Zn2Cr-Tart/Cl second-stage compounds with either fluoride or adipate anions initially occurs with preferential replacement of the hydrophilic Cl ion with F or replacement of the hydrophobic succinate or tartrate anions with adipate; this leads to the formation of new second-stage intermediates Zn2Cr-Succ/F and Zn2Cr-Tart/F or Zn2Cr-Adip/Cl. The formation of such heterostructures offers new perspectives for LDH intercalation chemistry, particularly in the direction of multifunctional materials.