Decarbonating layered double hydroxides using a carbonated salt solution.

Layered double hydroxides (LDHs) intercalated with tunable anionic species are finding increasingly wide applications. While LDHs with intercalated CO 3 2- anions (LDH-CO 3 ) are usually synthesized to achieve high crystallinity, the substitution of the intercalated CO 3 2- with other desired anions is rather difficult because of the ultra-high affinity of CO 3 2- to LDHs' main plates. Herein, we report a novel and facile method to overcome this difficulty. LDH-CO 3 is decarbonated via submerging in a carbonated NaCl solution with CO 2 bubbling. Complete deintercalation of CO 3 2- is achieved quickly without damaging the main plates, i.e. , the hydroxide layers, even in the case of Mg 2 Al-LDH-CO 3 having the most stable CO 3 2- anions. It is shown that carbonic acid H 2 CO 3 in the salt solution reacts with intercalated CO 3 2- to form bicarbonate (HCO 3 - ), which exhibits a much lower affinity to the main plates and thus is easily substituted by chloride ions (Cl - ) from the salt solution.