[Sn 2 S 6 ] 4- Anion-Intercalated Layered Double Hydroxides for Highly Efficient Capture of Iodine.

The development of low-cost and high-efficiency iodine sorbents is of great significance for the control of nuclear pollution. In this work, we intercalate the tin sulfide cluster of [Sn 2 S 6 ] 4- to Mg/Al-type layered double hydroxides to obtain Sn 2 S 6 -LDH, which exhibits highly efficient capture performance of iodine vapor and iodine in solutions. The dispersion effect of the positively charged LDH layers contributes to the adequate exposure of [Sn 2 S 6 ] 4- anions, providing plentiful adsorption sites. For iodine vapor, Sn 2 S 6 -LDH showed an extremely large iodine capture capacity of 2954 mg/g with a large contribution from physisorption. For iodine in solutions, a significantly large sorption capacity of 1308 mg/g was achieved. During iodine capture, I 2 molecules were reduced to I - ions (by S 2- in [Sn 2 S 6 ] 4- ), which then reacted with Sn 4+ to form SnI 4 , where the molar amount of captured iodine is 4-fold that of Sn. Besides, the as-reduced I - combined with I 2 again to generate [I 3 ] - , which then entered the LDH interlayers to maintain electric neutrality. While reducing iodine, S 2- itself in [Sn 2 S 6 ] 4- was oxidized to S 8 , which further combined with SnI 4 to form a novel compound of SnI 4 (S 8 ) 2 . The excellent iodine capture capability endows Sn 2 S 6 -LDH with a promising application in trapping radioactive iodine.