Unraveling the Nature of Extraframework Catalytic Ensembles in Zeolites: Flexibility and Dynamics of the Copper-Oxo Trimers in Mordenite

Extraframework cations
define the chemical versatility of zeolite
catalysts. Addressing their structural complexity and dynamic behavior
represents one of the main fundamental challenges in the field. Herein,
we present a computational approach for the identification and analysis
of the accessible pool of intrazeolite extraframework complexes with
a Cu/MOR catalyst as an industrially important model system. We employ ab initio molecular dynamics for capturing the ensemble
of reactive isomers with the [Cu3O3]2+ stoichiometry confined in the mordenite channels. The high structural
diversity of the generated isomers was ensured by concentrating the
kinetic energy along the low-curvature directions of the potential
energy surface (PES). Geometrically distinct [Cu3O3]2+ complexes were identified via a series of clustering
procedures ensuring that one structure of each local minima is retained.
The proposed procedure has resulted in a set of previously unknown
peroxo-complexes, which are >50 kJ/mol more stable than the recently
hypothesized chair-shaped structure. Our analysis demonstrates that
the most stable peroxo-containing clusters can be formed under operando conditions from molecular oxygen and the Cu3O unit, similar to that in methane monooxygenase (MMO) enzymes.