Abstract: It was earlier established that Zn2+ species loaded in zeolites promoted alkane C–H bond activation by Brønsted acid sites (BAS). It was found that the rate of H/D hydrogen exchange between alkane and zeolite BAS increased dramatically, and the activation barrier decreased for Zn2+-modified zeolite compared to H-form zeolite. However, it still remains unclear what the nature of the promoting effect of Zn2+ species on C–H bond activation is. In this work, the possible mechanisms of methane hydrogen exchange on the Zn2+/H-ZSM-5 zeolite have been analyzed by means of hybrid quantum chemical calculations (PBEh-3c/DLPNO-CCSD(T)). Four models representing various locations of Zn2+ ions in H-ZSM-5 differing in Al distribution and local geometry have been investigated. Zn2+ sites are found to be rather diverse in their adsorption properties and reactivity. The earlier accepted hypothesis of H/D hydrogen exchange promotion via the formation of a transient molecular complex of methane with Zn2+ sites has been disproven by the PBEh-3c/DLPNO-CCSD(T) calculations. Conversely, the two-step mechanism of hydrogen exchange in methane on Zn2+/H-ZSM-5 involving zinc-methyl species formation is concluded to be the most probable. Thus, the rationalization of how Zn2+ sites affect alkane C–H bond activation by BAS has been provided.

Cite: Lashchinskaya Z.N. , Gabrienko A.A. , Stepanov A.G.
How Do Zn2+ Ions Promote Methane Activation on Zinc-Modified Zeolites? A Hybrid Quantum-Chemical Study
Inorganic Chemistry. 2025. DOI: 10.1021/acs.inorgchem.5c02133 WOS Scopus AN PMID OpenAlex

Dates:

Submitted:	May 12, 2025
Accepted:	Jun 12, 2025
Published online:	Jun 17, 2025

Identifiers:

Web of science:	WOS:001520189900001
Scopus:	2-s2.0-105008331576
Chemical Abstracts:	2025:1366704
PMID:	40526139
OpenAlex:	W4411368994

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