Stable and Uniform Extraframework Cations in Faujasite Zeolites

Abstract

Extraframework transition metal ions (TMIs) in zeolites can serve as active sites for adsorption and catalysis. However, due to the complexity and mobility of extraframework cation sites, their applications are significantly limited and the structure–performance relationship is poorly understood. In this Perspective, stable and uniform TMIs in zeolites are exemplified and their characteristics are discussed. A series of TMIs can be introduced to specific cation sites of faujasite via a ligand-protected in situ synthesis route to construct uniform TMIs in the zeolite matrix, namely, TMI@FAU (TMI= Co, Ni, Cu, Rh, and Pt). Coordinatively unsaturated TMIs within faujasite are active for small-molecule adsorption and activation, and therefore, TMI@FAU zeolites show unique properties in adsorption and catalysis. TMI@FAU zeolites appear to be ideal model systems, and the well-defined structure of TMI@FAU greatly facilitates the mechanism studies by spectroscopic investigations and theoretical simulations.

Zeolite-Encaged Luminescent Silver Nanoclusters

“…Taking FAU zeolite as an example, as shown in Figure 2 a, site I is located inside the D6r cage, sites II and III inside the sodalite cage, and sites IV and V inside the super cage, respectively. All the sites from I to V can be occupied by extra framework cations with different ionic radii, such as Li + , Na + , K + , NH 4+ , H + , and Ca 2+ [ 55 , 57 ]. The researchers studied the influence of extra framework cations on the luminescence properties of Ag NCs in the Na-FAUY zeolite and Li + , Ca 2+ partially exchanged zeolites.…”

“… Typical extra framework cation sites I(I’), II(II’, II*), III(III’), IV, and V in the structure of FAU zeolites ( a ) [ 57 ], and summary of the integrated emission intensity and peak position of MYxAg (M = 5Li, 2Li, Na, and 2Ca; x = 5, 10, 20, 30, and 50) ( b ) [ 29 ]. …”

Incorporating solvent effects in DFT: insights from cation exchange in faujasites

“…Given the intrinsically diverse behaviors of zeolites, there has been a concerted effort within the scientific community to comprehensively understand the cation distribution within distinct zeolite extra-frameworks. [27][28][29][30][31][32] Nevertheless, characterizing these systems can be intricate, especially when solvents are present.…”

Reversible Intrapore Redox Cycling of Platinum in Platinum-Ion-Exchanged HZSM-5 Catalysts

“…We were motivated by recent observations that aluminum concentrations in HZSM-5 critically influence platinum aggregation and redispersion processes. − Platinum loading and zeolite pore and particle sizes , also affect these processes. Brønsted acid centers at aluminum sites anchor platinum ions, and, we infer, influence the path of charged, mobile platinum species during redox cycles.…”