Copper-exchanged mordenites prepared by different methods, conventional and microwave assisted, have been investigated
by TG, DSC, temperature-programmed reduction (TPR), and EPR methods. TPR study of hydrated and annealed at
573 and 973 K samples revealed that the copper reduction occurs directly from Cu2? to Cu0, and Cu2? ions are in different
local environments. The microwave-assisted treatment leads to formation of [Cu–O–Cu]2? species in the main mordenite
channels. The most easily recoverable copper in the fully hydrated samples corresponds to the individual Cu2? ions
coordinated by H2O molecules, and the number of these [Cu(H2O)n]2? complexes does not depend on the preparation
method and the total copper content. According to the EPR study, upon sample dehydration, [Cu(H2O)n]2? species lose
water and approach the wall of the zeolite forming a bond with reversible charge transfer from a framework oxygen to
Cu2?.