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Hidden diversity of vacancy networks in Prussian blue analogues

DOI: 10.1038/s41586-020-1980-y DOI Help

Authors: Arkadiy Simonov (University of Oxford; ETH Zürich) , Trees De Baerdemaeker (University of Oxford; KU Leuven) , Hanna L. B. Bostroem (Uppsala University; University of Oxford) , María Laura Ríos Gómez (Universidad Nacional Autónoma de México; University of Cambridge) , Harry J. Gray (University of Oxford) , Dmitry Chernyshov (European Synchrotron Radiation Facility) , Alexey Bosak (European Synchrotron Radiation Facility) , Hans-beat Bürgi (University of Zürich; University of Berne) , Andrew L. Goodwin (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature , VOL 578 , PAGES 256 - 260

State: Published (Approved)
Published: February 2020
Diamond Proposal Number(s): 13639 , 20876 , 22610

Abstract: Prussian blue analogues (PBAs) are a diverse family of microporous inorganic solids, known for their gas storage ability1, metal-ion immobilization2, proton conduction3, and stimuli-dependent magnetic4,5, electronic6 and optical7 properties. This family of materials includes the double-metal cyanide catalysts8,9 and the hexacyanoferrate/hexacyanomanganate battery materials10,11. Central to the various physical properties of PBAs is their ability to reversibly transport mass, a process enabled by structural vacancies. Conventionally presumed to be random12,13, vacancy arrangements are crucial because they control micropore-network characteristics, and hence the diffusivity and adsorption profiles14,15. The long-standing obstacle to characterizing the vacancy networks of PBAs is the inaccessibility of single crystals16. Here we report the growth of single crystals of various PBAs and the measurement and interpretation of their X-ray diffuse scattering patterns. We identify a diversity of non-random vacancy arrangements that is hidden from conventional crystallographic powder analysis. Moreover, we explain this unexpected phase complexity in terms of a simple microscopic model that is based on local rules of electroneutrality and centrosymmetry. The hidden phase boundaries that emerge demarcate vacancy-network polymorphs with very different micropore characteristics. Our results establish a foundation for correlated defect engineering in PBAs as a means of controlling storage capacity, anisotropy and transport efficiency.

Subject Areas: Materials, Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction

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