TY - JOUR
T1 - Unique pore selectivity for Cs+ and exceptionally high NH 4+ exchange capacity of the chalcogenide material K 6Sn[Zn4Sn4S17]
AU - Manos, Manolis J.
AU - Chrissafis, Konstantinos
AU - Kanatzidis, Mercouri G.
PY - 2006/7/12
Y1 - 2006/7/12
N2 - Highly selective ion-exchange properties and -exchange capacities of the open framework chalcogenide material K6Sn[Zn4Sn 4S17] (1) with Cs+ and NH4 + are reported. Because the structure of this framework is known in great detail, these studies are a rare example where structure/property relationships can be directly drawn. 1 possesses three types of micropore cavities. The largest pore of 1 presents an exact fit for Cs+ and exhibits high selectivity for this ion, as demonstrated by competitive ion-exchange experiments. The next largest pore has a greater capacity (up to four cations) and is well suited for NH4+ ions. This leads to a high ammonium-exchange capacity for 1 of 3.06 mequiv/gr, which is close to the NH4+-exchange capacities of natural zeolites. The single-crystal structures of ammonium-exchanged products at various stages reveal an unusual mechanism for the exchange process of 1 which involves diffusion of ammonium cations from the large cavity to the small ones of the framework. Thermal analysis of one of these ammonium-exchanged products, in combination with mass spectroscopy, showed the decomposition of NH 4+ cations to NH3 and H2S with the parallel transformation of the exchanged product to a mixture of crystalline phases. Since K6Sn[Zn4Sn4S17] can be grown in suitably large crystals (much larger than most zeolites), it defines an excellent model system in which ion-exchange processes and products can be characterized and studied in detail in various reaction stages.
AB - Highly selective ion-exchange properties and -exchange capacities of the open framework chalcogenide material K6Sn[Zn4Sn 4S17] (1) with Cs+ and NH4 + are reported. Because the structure of this framework is known in great detail, these studies are a rare example where structure/property relationships can be directly drawn. 1 possesses three types of micropore cavities. The largest pore of 1 presents an exact fit for Cs+ and exhibits high selectivity for this ion, as demonstrated by competitive ion-exchange experiments. The next largest pore has a greater capacity (up to four cations) and is well suited for NH4+ ions. This leads to a high ammonium-exchange capacity for 1 of 3.06 mequiv/gr, which is close to the NH4+-exchange capacities of natural zeolites. The single-crystal structures of ammonium-exchanged products at various stages reveal an unusual mechanism for the exchange process of 1 which involves diffusion of ammonium cations from the large cavity to the small ones of the framework. Thermal analysis of one of these ammonium-exchanged products, in combination with mass spectroscopy, showed the decomposition of NH 4+ cations to NH3 and H2S with the parallel transformation of the exchanged product to a mixture of crystalline phases. Since K6Sn[Zn4Sn4S17] can be grown in suitably large crystals (much larger than most zeolites), it defines an excellent model system in which ion-exchange processes and products can be characterized and studied in detail in various reaction stages.
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U2 - 10.1021/ja061342t
DO - 10.1021/ja061342t
M3 - Article
C2 - 16819882
AN - SCOPUS:33745959378
SN - 0002-7863
VL - 128
SP - 8875
EP - 8883
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 27
ER -