(196d) First-Principles Investigation of Cu Ion Exchange and Siting Preference in FER Zeolite

Cu-exchanged zeolites, in particular Cu-SSZ-13, are known to be active materials for the selective catalytic reduction (SCR) of NO_x with NH₃. SCR activity is known to be associated with isolated, exchanged Cu ions, and thus the nature of Cu exchange is critical in understanding the relationship between catalytic activity and framework topology, Si:Al ratio, and co-cations. In SSZ-13, it is now well established that Cu²⁺ exchanges into the framework at proximal pairs of charge-compensating framework Al within a six-membered ring (6MR) to create Z₂Cu sites and at isolated framework Al to form ZCu²⁺OH sites. Construction of the composition phase diagram for SSZ-13 is facilitated by the high symmetry of the CHA lattice.

In this work, we explore extending this methodology to lower symmetry frameworks, with a particular emphasis on FER, chosen because FER is a 2-dimensional framework with multiple T-sites. We interrogate and compare Cu exchange in zeolites through first-principle simulations and statistical enumeration. We identify the sensitivity of the Cu speciation and siting preference to zeolite topology, which promises the potential of rational choice of zeolite topology to tailor the Cu speciation.This approach can be extended to calculate the Cu speciation of other zeolite topologies for specific catalytic applications of interest.