[Sn₂S₆]^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 [Sn₂S₆]^4- to Mg/Al-type layered double hydroxides to obtain Sn₂S₆-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 [Sn₂S₆]^4- anions, providing plentiful adsorption sites. For iodine vapor, Sn₂S₆-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, I₂ molecules were reduced to I^- ions (by S^2- in [Sn₂S₆]^4-), which then reacted with Sn⁴⁺ to form SnI₄, where the molar amount of captured iodine is 4-fold that of Sn. Besides, the as-reduced I^- combined with I₂ again to generate [I₃]^-, which then entered the LDH interlayers to maintain electric neutrality. While reducing iodine, S^2- itself in [Sn₂S₆]^4- was oxidized to S₈, which further combined with SnI₄ to form a novel compound of SnI₄(S₈)₂. The excellent iodine capture capability endows Sn₂S₆-LDH with a promising application in trapping radioactive iodine.