Probing the Influence of Defects, Hydration, and Composition on Prussian Blue Analogues with Pressure

• DOI: 10.1021/jacs.0c13181
• Publication Date: 2021-02-25T14:58:10Z
• Authors: Hanna L. B. Boström; Ines E. Collings; Dominik Daisenberger; Christopher J. Ri...; Nicholas P. Funnell; Andrew B. Cairns
• Keywords: PBA; Chemistry, Multidisciplinary; Materialkemi; interplay; 02 engineering and technology; bulk modulus; Biochemistry; Sociology; Space Science; Materials Chemistry; ELECTRON-TRANSFER; Multidisciplinary; DOUBLE PEROVSKITES; Prussian Blue Analogues; SPIN-CROSSOVER; use variable-pressure X-ray; Condensed Matter Physics; MAGNETIC-POLE INVERSION; phase transitions; flexibility; Chemistry; Physical Sciences; compressibility; Medicine; 03 Chemical Sciences; 0210 nano-technology; Den kondenserade materiens fysik; space group Pn; hydration; A-site cation; defect; Chemical Sciences not elsewhere classified; Biophysics; 530; NEGATIVE THERMAL-EXPANSION; METAL-ORGANIC FRAMEWORKS; neutron diffraction; phase behavior; low-energy distortions; pressure-induced phase transition; Rb; Evolutionary Biology; Science & Technology; PORE-SIZE; Interstitial water increases B 0; Cell Biology; General Chemistry; AQUEOUS SODIUM; ALKALI CATION; 1 GPa; insights aim; X-RAY; Physical Sciences not elsewhere classified; Developmental Biology

The vast compositional space of Prussian blue analogues (PBAs), formula AxM[M'(CN)6]y·nH2O, allows for a diverse range of functionality. Yet, the interplay between composition and physical properties-e.g., flexibility and propensity for phase transitions-is still largely unknown, despite its fundamental and industrial relevance. Here we use variable-pressure X-ray and neutron diffraction to explore how key structural features, i.e., defects, hydration, and composition, influence the compressibility and phase behavior of PBAs. Defects enhance the flexibility, manifesting as a remarkably low bulk modulus (B0 ≈ 6 GPa) for defective PBAs. Interstitial water increases B0 and enables a pressure-induced phase transition in defective systems. Conversely, hydration does not alter the compressibility of stoichiometric MnPt(CN)6, but changes the high-pressure phase transitions, suggesting an interplay between low-energy distortions. AMnCo(CN)6 (AI = Rb, Cs) transition from F4̅3m to P4̅n2 upon compression due to octahedral tilting, and the critical pressure can be tuned by the A-site cation. At 1 GPa, the symmetry of Rb0.87Mn[Co(CN)6]0.91 is further lowered to the polar space group Pn by an improper ferroelectric mechanism. These fundamental insights aim to facilitate the rational design of PBAs for applications within a wide range of fields.