Theoretical investigation of dephosphorylation of phosphate monoesters on CeO2(111)

The dephosphorylation of neutral model phosphate monoesters on CeO2(111), including para-nitrophenyl phosphate and methyl phosphate, has been studied theoretically using self-consistent, periodic density functional theory calculations at the GGA + U-PW91 level. These phosphate monoesters interact strongly with CeO2(111) by forming a bond between the P atom and a surface lattice O atom. A surface-assisted hydrolysis mechanism is proposed for the catalytic dephosphorylation of the phosphate monoesters on CeO2(111), which involves P-O ester bond scission followed by phosphate hydration and product desorption. The energies of the transition states for the P-O ester bond scission are found to follow a linear scaling relation with respect to the energies of the dissociated fragments reasonably well. A nearly spontaneous transfer of one of the H atoms on the phosphate group to the alkoxide group produces the corresponding alcohol. The hydration of the remaining HPO3 group has a maximum activation energy of ca. 1.1 eV in vacuo. Thus although the nature of the alkoxide group affects the activation of the P-O ester bond, it should not affect the overall catalytic activity of CeO2(111) for dephosphorylation because the hydration of the phosphate group is rate-limiting.