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Exceptional Perrhenate/Pertechnetate Uptake and Subsequent Immobilization by a Low-Dimensional Cationic Coordination Poymer: Overcoming the Hofmeister Bias Selectivity

日期:2017-6-1 20:57:28 人气:52 

Abstract

We report on of the most efficient scavenger materials, a cationic crystalline coordination polymer SBN for trapping ReO4-, a surrogate for 99TcO4-, as an anionic radioactive contaminant of great concern. The uptake capacity for ReO4- reaches 786mg/g, a value noticeably higher than the stats of art anion-exchange resins and other inorganic or hybrid anion sorbents. Once being captured, ReO4- is greatly immobilized, as most no ReO4- can be eluted using large excess of nitrate, carbonate and phosphate anions. The processes are featured by a complete and irreversible single-crystal to single-crystal structural transformation from SBN to the ReO4- incorporated phase (SBR). The coordination environments of NO3- and ReO4- probed by single-crystal structure clearly unravel the underlying mechanism, where each ReO4- in SBR binds to multiple Ag+ sites forming strong Ag-O-Re bonds, and to 4,4’-bipyridine through a dense hydrogen bond network. These structural insights lead to a significant difference in solubility product constants between SBN and SBR, which is further confirmed by first principle calculations showing a large binding energy difference of 35.61kcal/mol. To the best of our knowledge, SBR is the least soluble perrhenate/pertechnetatesalt reported, which may be considered as a  potential waste form for direct immobilization of TcO4-.