Control of metal-organic framework (MOF) crystal alignment and orientation by electric field

Hall, Connor Harry

Abstract

Due to most Metal-Organic Frameworks (MOFs) possessing anisotropic properties, it could prove extremely useful to control and manipulate their alignment and orientation. Such control of MOF crystal microrods has previously been demonstrated by use of a magnetic field as part of a collaboration between the University of Hull (UK), University of Vienna (Austria) and Northwestern University (USA). Following on this work, here we show that similar methods can be exploited in order to dynamically align MOF crystals NU-1000 by applying an electric field, making it directly compatible with device integration. Experiments have been performed on this MOF in the form of two different samples: i) an unfixed suspension in bromobenzene allowing for dynamic and reconfigurable alignment and ii) a solid sample with the MOF alignment fixed in place by resin curing. The alignment of the NU-1000 was then confirmed and quantified by studying the fluorescence emission under polarised excitation, taking advantage of the absorption anisotropy. A laser emitting light of wavelength 405nm was used to excite the samples and the resulting fluorescence was measured as a function of the incident angle of polarisation relative to the orientation of the NU-1000 crystal. In a second stage, the emission and absorption polarisation properties of the aligned MOF samples were measured. It was found that the fluorescence emission, as well as the absorption, are polarised along the MOF crystal long axis. This work and potential future work has applications in optics and electronics such as energy transfer, gas sensing and separation, display technology and optical switches.

Citation

Hall, C. H. (2020). Control of metal-organic framework (MOF) crystal alignment and orientation by electric field. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4223266

• Thesis Type: Thesis
• Deposit Date: Jul 8, 2021
• Publicly Available Date: Feb 23, 2023
• Keywords: Physics
• Public URL: https://hull-repository.worktribe.com/output/4223266
• Additional Information: Department of Physics and Mathematics, The University of Hull
• Award Date: Aug 1, 2020