Single-Crystal Structures of Sr2+ and Cs+-Exchanged Zeolites X and Y, |Sr40Cs12|[Si100Al92O384]-FAU and |Sr29Cs17|[Si117Al75O384]-FAU

Abstract

Two single-crystals of fully dehydrated, Sr2+-and Cs+-exchanged zeolites X (|Sr40Cs12|[Si100Al92O384]-FAU (Si/Al = 1.09, crystal 1)) and Y (|Sr29Cs17|[Si117Al75O384]-FAU (Si/Al = 1.56, crystal 2)) were prepared by the flow method using a mixed ion-exchange solution whose Sr(NO3)2:CsNO3 mol ratio was 1:1 with a total concentration of 0.1 M. The crystals were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group $$Fd\overline{ 3}$$ and $$Fd\overline{ 3} m,$$ respectively, and were refined to the final error indices R 1/wR 2 = 0.070/0.209 and 0.052/0.155 for crystals 1 and 2, respectively. In the structure of |Sr40Cs12|[Si100Al92O384]-FAU, 40 Sr2+ ions per unit cell occupy three different equipoints; 16, 1.5, and 22.5 are at sites I, II′, and II, respectively. The 12 Cs+ ions per unit cell occupy three equipoints; 1, 6, and 5 are at sites II′, II, and IIIa, respectively. In the structure of |Sr29Cs17|[Si117Al75O384]-FAU, 29 Sr2+ ions per unit cell occupy four equipoints; 15, 1.5, 2.5, and 10 are at sites I, I′, II′, and II, respectively. The 17 Cs+ ions per unit cell are found at four different sites; 2.5, 9, 4, and 1.5 are at sites II′, II, IIIa, and IIIb, respectively. The Sr2+ ions occupy smaller pore size such as the centers of the double 6-rings and the positions near the center of single 6-rings planes, whereas, Cs+ ions preferentially occupy large-cavity sites in the supercage. Two single-crystals of fully dehydrated, Sr2+-and Cs+-exchanged zeolites X (|Sr40Cs12|[Si100Al92O384]-FAU (Si/Al = 1.09, crystal 1)) and Y (|Sr29Cs17|[Si117Al75O384]-FAU (Si/Al = 1.56, crystal 2)) were determined by single-crystal synchrotron X-ray diffraction techniques.