Single Open Sites on Fe Ions Stabilized by Coupled Metal Ions in CN-Deficient Prussian Blue Analogues for High Catalytic Activity in the Hydrolysis of Organophosphates.

CN-deficient Prussian blue analogues (PBAs), [M(HO)][Fe(CN)(NH)] (M = Cu, Co, or Ga), were synthesized and examined as a new class of heterogeneous catalysts for hydrolytic decomposition of organophosphates often used as pesticides. The active species of the CN-deficient PBAs were mainly C-bound Fe ions with only single open sites generated by liberation of the NH ligand during the catalytic reactions. [Cu(HO)][Fe(CN)(NH)] showed higher catalytic activity than [Co(HO)][Fe(CN)(NH)] and [Ga(HO)][Fe(CN)(NH)], although N-bound Cu species has been reported as less active than Co and Ga species in conventional PBAs. IR measurements of a series of the CN-deficient PBAs after the catalytic reactions clarified that a part of the NH ligands remained on [Co(HO)][Fe(CN)(NH)] and that hydrogen phosphate formed as a product strongly adsorbed on the Fe ions of [Ga(HO)][Fe(CN)(NH)]. Hydrogen phosphate also adsorbed, but weakly, on the Fe ions of [Cu(HO)][Fe(CN)(NH)]. These results suggest that heterogeneous catalysis of the Fe ions with single open sites were tuned by the M ions through metal-metal interaction.