Iron oxide-based catalysts can selectively covert CO 2 to added-value CO in parallel with on-purpose ethylene production via ethane dehydrogenation (CO 2 -EDH). The 5Fe/10NiMgZr catalyst, calcined at 700 °C for 5 h, reached 90% selectivity, at a single-pass C 2 H 6 conversion of ∼23.3%, during CO 2 -EDH at 650 °C. X-ray characterization techniques (XRD, XPS, XAS, and XRS), along with structural modeling were used to elucidate the nature of highly selective active sites toward C−H bond scission. Under reaction conditions, Fe atoms are incorporated into the support lattice, as it was exemplified by XRS at Mg L 2,3 -and O K-edges. The dynamic structural modifications, occurring during CO 2 -EDH, highlighted the pivotal role of the support, reaching an ethylene yield of 21%. Mg coordination altered from octahedral to tetrahedral. The latter was accompanied by an electronic modification, which had a strong impact on the catalyst acidity, based on Fourier transform infrared spectroscopy combined with in situ adsorption of pyridine, resulting in an unpresented ethylene selectivity for Fe oxide-based catalysts.