A metamorphic inorganic framework that can be switched between eight single-crystalline states

Caihong Zhan,Jamie M Cameron,David Gabb,Stefan Glatzel,Laia Vilà-Nadal,Duncan H Gregory,Ross S Winter,Scott G Mitchell,Joachim Breternitz,Andrew Macdonell,De-Liang Long,Thomas Boyd,Leroy Cronin

doi:10.1038/ncomms14185

Abstract

The design of highly flexible framework materials requires organic linkers, whereas inorganic materials are more robust but inflexible. Here, by using linkable inorganic rings made up of tungsten oxide (P8W48O184) building blocks, we synthesized an inorganic single crystal material that can undergo at least eight different crystal-to-crystal transformations, with gigantic crystal volume contraction and expansion changes ranging from −2,170 to +1,720 Å3 with no reduction in crystallinity. Not only does this material undergo the largest single crystal-to-single crystal volume transformation thus far reported (to the best of our knowledge), the system also shows conformational flexibility while maintaining robustness over several cycles in the reversible uptake and release of guest molecules switching the crystal between different metamorphic states. This material combines the robustness of inorganic materials with the flexibility of organic frameworks, thereby challenging the notion that flexible materials with robustness are mutually exclusive.

Highlights

The design of highly flexible framework materials requires organic linkers, whereas inorganic materials are more robust but inflexible
We decided to use polyoxometalate anions[14], a type of molecular metal oxide, as functional building blocks for the construction of our crystal-based materials, as such assemblies have a vast number of significant intrinsic properties to exploit, such as electron storage[15], water splitting[16] and both acid and oxidative catalysis[17]
The parent compound, Li9K7W1Co10[H2P8W48O186] Á 132 H2O (1), is synthesized under relatively mild conditions, using a two-step approach involving the reaction of the pre-formed {P8W48} building block with Co(ClO4)[2] Á 6 H2O in aqueous media, and can be isolated in good yield (66%) as rectangular red crystals

Summary

Introduction

The design of highly flexible framework materials requires organic linkers, whereas inorganic materials are more robust but inflexible. The first of these crystal-tocrystal transformations was discovered by dehydrating compound 1 through heating the crystals at 80 °C in vacuum, where they underwent a distinct colour change from red to dark purple.

Results

Conclusion