Confinement of Ionic Liquid Crystals into Covalent Organic Frameworks
Andreia F. M. SANTOS1, Sunny K. S. FREITAS1,4, Maria H. GODINHO2, J. L. FIGUEIRINHAS3, Madalena DIONÍSIO1, Pierre M. ESTEVES4, Luis C. BRANCO1
1LAQV-REQUIMTE, Department of Chemistry, NOVA School of Science and Technology, NOVA University of Lisbon, Campus de Caparica, Caparica, Portugal
2i3N/CENIMAT, Department of Materials Science, NOVA School of Science and Technology, NOVA University of Lisbon, Campus de Caparica, Caparica, Portugal
3CeFEMA and Department of Physics, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, Lisboa, Portugal
4Instituto de Química, Universidade Federal do Rio de Janeiro, Avenida Athos da Silveira Ramos, nº 149, Bloco A—7º andar Centro de Tecnologia—Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil
Covalent organic frameworks (COFs) have emerged in the past few years as a new class of crystalline porous organic polymeric materials, offering the possibility to modulate their pore size and final structure by choosing specific building blocks [1, 2]. Recent studies have shown that these frameworks can be extremely relevant in several fields, such as water purification, gas adsorption, batteries, catalysis and sensors [3, 4]. It is worthwhile noting that COFs can be used either as functional materials or as a matrix to increase the host performance. In this context, aiming to assess the impact of the nanoconfinement in the mesomorphic behaviour of the dodecyl-3-methylpyridinium bromide ([C12-3-Pic][Br]), an ionic liquid crystal, i.e., ionic liquid with liquid crystalline properties, two different covalent organic frameworks were selected as matrixes: RIO-23 (non-ionic COF) and RIO-54 (ionic COF). It is known that [C12-3-Pic][Br] exhibits a thermotropic smectic A phase, emerging at ~30°C, in the first heating run [5]. On the other hand, RIO-23 and RIO-54 were chosen considering their pore size and physicochemical properties, allowing to host other substrates with high stability. RIO-23 presents a heterogeneous porous matrix, containing simultaneously micro- and mesopores, while RIO-54 is intrinsically mesoporous, having a higher percentage of anions in its cavities. To the best of our knowledge, there are no studies about the use of COFs functionalized with ionic liquid crystals or their confinement into COFs. Herein, we present the characterization of these composite systems in terms of their mesomorphic properties.
Acknowledgments: This work was supported by the Associate Laboratory for Green Chemistry LAQV (UID/QUI/50006/2019), i3N (UID/CTM/50025/2019) and CeFEMAS (UID/CTM/04540/2019), which are financed by national funds from FCT-MCTES and by FEDER funds through the COMPETE 2020 Program. The authors also thank the National Funds through FCT-MCTES and POR Lisboa 2020, under the projects numbers POCI-01-0145-FEDER-007688, PTDC/CTM-REF/30529/2017 (NanoCell2SEC), European Topology Interdisciplinary Action (EUTOPIA CA17139) and CAPES/FCT-20181026020P. A. F. M. Santos also acknowledges FCT-MCTES for the PhD Grant (SFRH/BD/132551/2017).
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