Dynamic electric field alignment of metal-organic framework micro- rods

Cheng, Fei; Young, Adam J; Bouillard, Jean-Sebastien G.; Kemp, Neil T.; Guillet-Nicolas, Rémy; Hall, Connor H; Roberts, David; Jaafar, Ayoub H; Adawi, Ali M.; Kleitz, Freddy; Imhof, Arnout; Reithofer, Mi-Chael R; Chin, Jia Min

Abstract

Alignment of Metal Organic Framework (MOF) crystals has previously been performed via careful control of oriented MOF growth on substrates, as well as by dynamic magnetic alignment. We show here that microrod crystals of the MOF NU-1000 can also be dynamically aligned via electric fields whilst suspended in bromobenzene, giving rise to rapid electrooptical responses. This method of dynamic MOF alignment opens up new avenues of MOF control which are important for integration of MOFs into switchable electronic devices as well as in other applications such as reconfigurable sensors or optical systems. Metal-organic frameworks, which are crystalline materials comprising of inorganic nodes linked by organic ligands, are of significant research interest due to their flexible choice of link-ers and metals which afford them wide-ranging applications 1-3 such as in optics, sensing, electronics, gas separations and energy storage. It should also be noted that as most MOFs possess lattice ani-sotropy along different crystallographic axes, their corresponding chemical and physical properties also significantly differ along different crystallographic directions. Therefore, to fully exploit directional functionality of MOFs, it is important to be able to control MOF particle orientation. However, as MOF materials are typically synthesized as loose colloidal powders, it is challenging to impose and integrate particle orientational control into their utilization. Research in this area has consequently focused on growth of MOF crystals on various sub-strates, to favour selective directional growth. 4-6 However, this is time-consuming, and significant care must be taken to control crystal growth. Furthermore, the growth conditions for one type of MOF cannot simply be applied wholesale to other MOFs, with considerations of MOF-substrate lattice matching and interfacial physicochemical interactions complicating the widespread application of this approach. 7 Significantly, this approach renders the MOF orientation static, hindering the use of MOFs in applications requiring dynamicity, such as in stimuli-responsive devices, whereby the MOFs can reorient themselves under changing conditions. Given the vast applicability of MOFs, the ability to control MOF alignment in a dynamic fashion will have significant implications for many areas. The long range molecular order imposed by the MOF lattices, and their tuneable physicochemical properties, also render MOFs especially attractive for use in electronic devices. 8 E-field control of MOFs is therefore particularly desirable and there are emerging reports of external E-field MOF manipulation. Examples current driven synthesis of ZIF-8, 9 field-driven rotation of MOF ligands, 10-11 as well as the E-field induced polymorph switching of ZIF-8 12 and MIL-53. 13-15 Reports pertaining to conFigure 1. a-c) View of NU-1000 lattice along the a, b and c crystallographic axes respectively, showing the lattice anisotropy; d) Scanning electron micrograph of NU-1000 microrods where the shape anisotropy of the particles can be clearly observed.

Citation

Cheng, F., Young, A. J., Bouillard, J.-S. G., Kemp, N. T., Guillet-Nicolas, R., Hall, C. H., Roberts, D., Jaafar, A. H., Adawi, A. M., Kleitz, F., Imhof, A., Reithofer, M.-C. R., & Chin, J. M. (2019). Dynamic electric field alignment of metal-organic framework micro- rods. Journal of the American Chemical Society, 141(33), 12989-12993. https://doi.org/10.1021/jacs.9b06320

• Journal Article Type: Article
• Acceptance Date: Aug 1, 2019
• Online Publication Date: Aug 5, 2019
• Publication Date: Aug 21, 2019
• Deposit Date: Oct 9, 2019
• Publicly Available Date: Aug 6, 2020
• Journal: Journal of the American Chemical Society
• Print ISSN: 0002-7863
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 141
• Issue: 33
• Article Number: 1
• Pages: 12989-12993
• DOI: https://doi.org/10.1021/jacs.9b06320
• Keywords: Colloid and Surface Chemistry; Biochemistry; General Chemistry; Catalysis
• Public URL: https://hull-repository.worktribe.com/output/2850774
• Contract Date: Oct 9, 2019