Two Coordination Modes of CO in Zeolites: A Temperature-Dependent Equilibrium.

CO interacts with exchangeable cations M (gray spheres in the picture) of zeolites to form M ⋅⋅⋅CO and M ⋅⋅⋅OC species (C: black; O: white) which are in a temperature-dependent equilibrium. For Na-ZSM-5 (M =Na ) the difference in interaction energy amounts to 3.8 kJ mol , as determined by means of variable-temperature FT-IR spectroscopy.