O2 isotopic exchange in the presence of O− anion radicals on the FeZSM-5 surface

18O2 + 16O−α ⇄ [O−3]α ⇄ 16O18O + 18O−α.The image exchange (image) is a new reaction pathway that appears at cryogenic temperatures and leads to isotope redistribution only between O2 molecules, not affecting the isotopic composition of Oα. This exchange mechanism is not quite clear. The necessity of the presence of Oα without its direct involvement in the exchange process seems to be quite surprising. The reaction may proceed via a hypothetical complex [O−5]α, which allows cleavage and redistribution of chemical bonds between two O2 molecules adsorbed on the α-oxygen. The cleavage and redistribution of such strong bonds at cryogenic temperatures with nearly zero activation energy are an intriguing phenomenon worthy of further study.