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 Cu 2 O(111) via formation of Cu(NH 3 ) 2 + are explored. It is found that the diamine complexes form easily on Cu 2 O(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 NH 4 + from the zeolite to the Cu 2 O 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.