Cryo-EM structures of atomic surfaces and host-guest chemistry in metal-organic frameworks
Abstract
Host-guest interactions govern the chemistry of a broad range of functional materials. However, the weak bonding between host and guest prevents atomic-resolution studies of their structure and chemistry using transmission electron microscopy (TEM). This problem is exacerbated in metal-organic frameworks (MOF), in which the host framework is easily damaged by the electron beam. Here, we use cryogenic-electron microscopy (cryo-EM) to simultaneously address these two challenges and resolve the atomic surface structure of zeolitic imidazolate framework (ZIF-8) and its interaction with guest CO2 molecules. We image atomic step-edge sites on the ZIF-8 surface that provides possible insight to its growth behavior. Furthermore, we observe two distinct binding sites for CO2 within the ZIF-8 pore, which are both predicted by density functional theory (DFT) to be energetically favorable. This CO2 insertion induces an apparent ~3% lattice expansion along the <002> and <011> directions of the ZIF-8 unit cell. The ability to stabilize MOFs and preserve their host-guest chemistry opens a rich materials space for scientific exploration and discovery using cryo-EM.
- Publication:
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arXiv e-prints
- Pub Date:
- April 2019
- DOI:
- 10.48550/arXiv.1904.04173
- arXiv:
- arXiv:1904.04173
- Bibcode:
- 2019arXiv190404173L
- Keywords:
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- Condensed Matter - Materials Science
- E-Print:
- 10 pages, 5 figures