Filling vacancies in a Prussian blue analogue using mechanochemical post-synthetic modification

Abstract

Mechanochemical grinding of polycrystalline powders of the Prussian blue analogue (PBA) Mn[Co(CN)₆]_2/3□_1/3·xH₂O and K₃Co(CN)₆ consumes the latter and chemically modifies the former. A combination of inductively-coupled plasma and X-ray powder diffraction measurements suggests the hexacyanometallate vacancy fraction in this modified PBA is reduced by approximately one third under the specific conditions we explore. We infer the mechanochemically-driven incorporation of [Co(CN)₆]³⁻ ions onto the initially-vacant sites, coupled with intercalation of charge-balancing K⁺ ions within the PBA framework cavities. Our results offer a new methodology for the synthesis of low-vacancy PBAs.