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Spatiotemporal Control of Supramolecular Polymerization and Gelation of Metal-Organic Polyhedra

preprint
submitted on 18.12.2020, 06:28 and posted on 21.12.2020, 06:45 by alexandre legrand, Li-Hao Liu, Philipp Royla, Takuma Aoyama, Gavin Craig, arnau carne-sanchez, Kenji Urayama, Jan J. Weigand, Chia-Her Lin, Shuhei Furukawa
In coordination-based supramolecular materials such as metallogels, simultaneous temporal and spatial control of their assembly remains challenging. Here, we demonstrate that the combination of light with acids as stimuli allows for the spatiotemporal control over the architectures, mechanical properties, and shape of porous soft materials based on metal-organic polyhedra (MOPs). First, we show that the formation of a colloidal gel network from a preformed kinetically trapped MOP solution can be triggered upon addition of trifluoroacetic acid (TFA), and that acid concentration determines the reaction kinetics. As determined by time-resolved dynamic light scattering, UV-vis absorption and 1H NMR spectroscopies and rheology measurements, the consequences of the increase in acid concentration are (i) an increase in the cross-linking between MOPs; (ii) a growth in the size of the colloidal particles forming the gel network; (iii) an increase in the density of the colloidal network; and (iv) a decrease in the ductility and stiffness of the resulting gel. We then demonstrate that irradiation of a dispersed photoacid generator, pyranine, allows the spatiotemporal control of the gel formation by locally triggering the self-assembly process. Using this methodology, we show that the gel can be patterned into a desired shape. Such precise positioning of the assembled structures, combined with the stable and permanent porosity of MOPs, could allow their integration into devices for applications such as sensing, separation, catalysis, or drug release.

Funding

JSPS KAKENHI Grant Number 20K15366

JSPS KAKENHI Grant Number 18H01995

JSPS KAKENHI Grant Number 19H04575

History

Email Address of Submitting Author

shuhei.furukawa@icems.kyoto-u.ac.jp

Institution

Kyoto University

Country

Japan

ORCID For Submitting Author

0000-0003-3849-8038

Declaration of Conflict of Interest

The authors declare that they have no competing financial interests.

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