Facile synthesis of sub-nanometer Cd_4S~(6+) and Cd_2S~(2+) cluster in zeolite Y and its structural characterization

摘要

The Cd4S6+ and Cd2S2+ clusters in the sodalite cavities were synthesized by reaction of the fully Cd2+-exchanged zeolite Y (Si/Al = 1.56) and 0.1 M Na2S(aq) solution at 294 K for 2 days. The single-crystal structure was determined at 100(1) K by synchrotron X-ray diffraction techniques in the cubic space group Fd (3) over barm. The structure was refined using all intensities to the final error index R-1/wR(2) = 0.048/0.156 (for F-o 4 sigma(F-o)). Approximately 13 Cd2+ and 53 Na+ ions per unit cell were found at two and four crystallographically distinct positions, respectively: two site-IMODIFIER LETTER PRIME positions (in the sodalite cavities opposite double 6-rings (D6Rs)) are occupied by 5 and 7.5 Cd2+ ions, respectively, per unit cell. The 0.5 Cd2+ ions per unit cell are at site IIMODIFIER LETTER PRIME in the sodalite cavity. The 2 Na+ ion is located at the center of the D6R (site I). The 15.5 Na+ ions per unit cell are located at site IMODIFIER LETTER PRIME. Site-II position is occupied by 31.5 Na+ ions per unit cell. The remaining 4 Na+ ions per unit cell are located at sites IIIMODIFIER LETTER PRIME near triple 4-rings in the supercage. Finally, 0.5 and 1.5 S2- ions per unit cell, associated with Cd2+ ions, were found at the center of sodalite cavity and opposite 6-ring in the sodalite cavity, respectively. The 1 S2- ion at the center of the sodalite cavity is coordinated to 4 Cd2+ ions at site IMODIFIER LETTER PRIME to give a centered-tetrahedral cationic cluster, Cd4S6+, and the other S2- ion opposite 6-ring in the sodalite cavity bridges between two Cd2+ ions at site IMODIFIER LETTER PRIME to give a cationic cluster with a bent arrangement, Cd2S2+, in 6.3% and 18.8% of the sodalite cavities of zeolite Y (Si/Al = 1.56), respectively.