O-EPR determination of the structure and dynamics of copper single-metal sites in zeolites.

The bonding of copper ions to lattice oxygens dictates the activity and selectivity of copper exchanged zeolites. By O isotopic labelling of the zeolite framework, in conjunction with advanced EPR methodologies and DFT modelling, we determine the local structure of single site Cu species, we quantify the covalency of the metal-framework bond and we assess how this scenario is modified by the presence of solvating HO or HO molecules. This enables to follow the migration of Cu species as a function of hydration conditions, providing evidence for a reversible transfer pathway within the zeolite cage as a function of the water pressure. The results presented in this paper establish O EPR as a versatile tool for characterizing metal-oxide interactions in open-shell systems.