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 CO32− anions (LDH-CO3) are usually synthesized to achieve high crystallinity, the substitution of the intercalated CO32− with other desired anions is rather difficult because of the ultra-high affinity of CO32− to LDHs’ main plates. Herein, we report a novel and facile method to overcome this difficulty. LDH-CO3 is decarbonated via submerging in a carbonated NaCl solution with CO2 bubbling. Complete deintercalation of CO32− is achieved quickly without damaging the main plates, i.e., the hydroxide layers, even in the case of Mg2Al-LDH-CO3 having the most stable CO32− anions. It is shown that carbonic acid H2CO3 in the salt solution reacts with intercalated CO32− to form bicarbonate (HCO3−), which exhibits a much lower affinity to the main plates and thus is easily substituted by chloride ions (Cl−) from the salt solution.