Figure 5.

The transition states of the ring-opening reaction upon exposure to CeO₂. The ring-opening reaction (a) is composed of two major mechanisms: the cleavage of the specific P–O bond via a transition state with a cyclic structure (i), as well as the nucleophilic attack on the P atom (ii) [199]. During the first interaction, the coordination reaction occurs between the phosphate group and a metal cation. This mechanism can explain the decontamination of toxic phosphotriesters [200]. With slight modifications, this model also shows the reaction resulting in 5′-AMP (b) and 3′-AMP (c). The excellent redox activities of the cerium cations in addition to the flexible structure of CeO₂ can justify why CeO₂ has considerably greater dephosphorylation activity than the oxides of neighboring elements. Reprinted with permission from [198].