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.