Structures of the Subnanometer Clusters of Cadmium Sulfide Encapsulated in Zeolite Y: Cd₄S⁶⁺ and Cd(SHCd)₄⁶⁺

Abstract

The structures of the subnanometer clusters of CdS that form in zeolite Y (FAU), prepared as follows, have been determined. A single crystal of Cd 2+ -exchanged zeolite Y was prepared by the exchange of Na 75 −Y (|Na 75 |[Si 117 Al 75 O 384]−Y with aqueous Cd(NO 3 ) 2 at 294 K, followed by vacuum dehydration at 723 K (crystal 1). A second crystal, similarly prepared, was exposed to 6.7 × 10 4 Pa of dry H 2 S(g) for 6 h at 294 K and evacuated (crystal 2). Their structures were determined crystallographically using synchrotron X-rays and were refined using all data to the final error indices (calculated using only0.040/0.156 and 0.049/0.186, respectively. In crystal 1, Cd 2+ ions primarily occupy sites I and II. In crystal 2, |Cd 27 (Cd 4 S 6+ ) 0.6 (Cd-(SHCd) 4 6+ ) 0.9 H 12 |[Si 117 Al 75 O 384 ]−FAU, tetrahedral Cd 4 S 6+ ions center about 7.5% of the sodalite cavities and tetrahedral Cd(SHCd) 4 6+ ions center about 11% of the supercages. In Cd(SHCd) 4 6+, a Cd 2+ ion at the center of a supercage bonds tetrahedrally to four SH − ions, each of which bonds in turn to an 8-ring Cd 2+ ion. Of the 36.5(9) Cd 2+ ions per unit cell (indicating complete or nearly complete Cd 2+ exchange) before treatment with H 2 S(g), only 6.9 participate in the above clusters. Most, 27, remain uncomplexed, and 2.6 have left the zeolite as CdS(s). No neutral clusters of formula Cd n S n are present within the zeolite.

Quantum Dots of [Na4Cs6PbBr4]8+, Water Stable in Zeolite X, Luminesce Sharply in the Green

“…For example, the “CdS QDs” in zeolite Y were found crystallographically to be the cationic clusters Cd 4 S 6+ and Cd(SHCd) 4 6+ , multiple in a 1:1 ratio. [ 23 ] Quite generally, QDs in zeolites can be expected to carry a charge; otherwise they should be more stable in their own phases outside the zeolite. The composition, structures, and charges of intrazeolitic clusters are generally governed by the framework structure of the zeolite, its anionic charge density, and the charges, sizes, and positions of its extraframework cations.…”

Supramolecular Organization in Confined Nanospaces

“…In principle, the clusters can form both in the sodalite cage and in the supercage of zeolite Y (Figure a, b). Recently, a structural model based on X‐ray diffraction (Figure c) has been proposed, suggesting that a tetrahedral ion (Cd 4 S 6+ ) occupies the SOD cage (similar to natural sodalite, Figure ), while a larger tetrahedral guest, Cd(SHCd) 4 6+ , is located in the supercage . A recent review thoroughly discusses the synthetic strategies to achieve, for example, the selective occupation of only one type of cages, and the broad spectrum of potential applications of these composite materials .…”

“…[37] c) X-rays structure of tetrahedral Cd 4 S 6 + ion in the sodalite cage (left) and tetrahedral Cd(SHCd) 4 6 + ion in the supercage (right) of zeolite Y (adapted with permission from Ref. [483] Copyright 2016 American Chemical Society). 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 visible spectrum [471] and with remarkable quantum efficiencies.…”

“…Recently, a structural model based on X-ray diffraction (Figure 29c) has been proposed, suggesting that a tetrahedral ion (Cd 4 S 6 + ) occupies the SOD cage (similar to natural sodalite, Figure 27), while a larger tetrahedral guest, Cd(SHCd) 4 6 + , is located in the supercage. [483] A recent review thoroughly discusses the synthetic strategies to achieve, for example, the selective occupation of only one type of cages, and the broad spectrum of potential applications of these composite materials. [37] For instance, photovoltaic solar cells based on CdS and PdS quantum dots encapsulated in zeolite Y have been realized, and the performance of such devices was found to depend, besides from the chemical nature of the nanospecies, on the homogeneity of their distribution inside the zeolite matrix.…”

The Different Organization of Water in Zeolite L and Its MOF Mimic

“…For these reasons, the realization of organized supramolecular systems in nanoporous frameworks is a steadily growing research area 9 . Zeolite cages have long been exploited to create confined nanostructures for optoelectronics 11 , like metal clusters, [12][13][14] quantum dots, 10,15,16 or lanthanide complexes 17 , and the practical applications of zeolite-based functional composites from effect pigments 18 , to theranostic agents 19,20 , keep on increasing in number and performances.…”