Metal-Organic Framework Contracts upon Heating

  • Author:
  • Published: 23 May 2018
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Chemical Communications/Royal Society of Chemistry
  • Associated Societies: Royal Society of Chemistry (RSC), UK
thumbnail image: Metal-Organic Framework Contracts upon Heating

Metal-organic frameworks (MOFs) are porous materials with a wide range of applications. They are held together by relatively weak interactions, which results in large numbers of degrees of freedom within the networks. This can cause a rare effect: negative thermal expansion (NTE), meaning the material contracts when it is heated. Usually, this contraction appears in only one or two dimensions. Three-dimensional NTE is rare and usually only found in high-symmetry cubic phases of MOFs.

Xianran Xing and colleagues, University of Science and Technology Beijing, China, have found the first example of 3D anisotropic NTE in a low-symmetry MOF. The team studied the behavior of the MOF MIL-68(In), which has an orthorhombic structure (pictured). They activated the MOF at 220 °C overnight to remove guest molecules. Then the researchers used high-energy synchrotron X-ray diffraction (SXRD) and single crystal X-ray diffraction (SCXRD) to observe changes in the material's structure upon heating.

MIL-68(In) shows an anisotropic NTE between 125 K and 600 K, with coefficients of thermal expansion along the three axes of αa = –5.6·10–6 K–1, αb = –2.7·10–6 K–1, and αc = –4.0·10–6 K–1, respectively. The X-ray diffraction results show that the contraction in the ab plane is due to a vibration of phenyl rings in the MOF's organic ligands, while the contraction along the c axis can be attributed to a rotation of rigid indium octahedrons. According to the researchers, these insights could help with tailoring the thermal expansion of MOF materials and with designing new NTE materials.


Article Views: 804

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

Bookmark and Share

If you would like to reuse any content, in print or online, from, please contact us first for permission. more

CONNECT: on Facebook on Twitter on YouTube on LinkedIn Sign up for our free newsletter

A product of ChemPubSoc Europe (16 European Chemical Societies)and Wiley-VCH