Successful Decontamination of 99 TcO 4 - in Groundwater at Legacy Nuclear Sites by a Cationic Metal-Organic Framework with Hydrophobic Pockets.

⁹⁹ Tc contamination at legacy nuclear sites is a serious and unsolved environmental issue. The selective remediation of ⁹⁹ TcO ₄ ^- in the presence of a large excess of NO ₃ ^- and SO ₄ ^2- from natural waste systems represents a significant scientific and technical challenge, since anions with a higher charge density are often preferentially sorbed by traditional anion-exchange materials. We present a solution to this challenge based on a stable cationic metal-organic framework, SCU-102 (Ni ₂ (tipm) ₃ (NO ₃ ) ₄ ), which exhibits fast sorption kinetics, a large capacity (291 mg g ^-1 ), a high distribution coefficient, and, most importantly, a record-high TcO ₄ ^- uptake selectivity. This material can almost quantitatively remove TcO ₄ ^- in the presence of a large excess of NO ₃ ^- and SO ₄ ^2- . Decontamination experiments confirm that SCU-102 represents the optimal Tc scavenger with the highest reported clean-up efficiency, while first-principle simulations reveal that the origin of the selectivity is the recognition of TcO ₄ ^- by the hydrophobic pockets of the structure.
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