Mechanism for Solid-State Ion Exchange of Cu+ into Zeolites

Density functional theory calculations are used to investigate solid-state ion exchange of copper into zeolites. In particular, the energetic conditions for functionalization of chabazite (CHA) with copper ions from Cu2O(111) via formation of Cu(NH3)(2)(+) are explored. It is found that the diamine complexes form easily on Cu2O(111) and diffuse with low barriers over the surface and in the CHA framework. The charge neutrality of the systems is maintained via counterdiffusion of H+ in the form of NH4+ from the zeolite to the Cu2O surface where water can be formed. The efficient solvation of Cu+ and H+ by ammonia renders the ion-exchange process exothermic. The present results highlight the dynamic character of the Cu ion sites and provide means to understand zeolite functionalization.