amphitheatre (salle 1035)
5155, chemin de la rampe
Montréal (QC) Canada  H3T 2B2

Surface-supported covalent organic networks
Sylvain Clair
CNRS, Aix-Marseille Université
IM2NP, 13397 Marseille, France

Abstract: The concepts of supramolecular chemistry have been successfully applied in the last decades to create well-organized structures on surfaces. Precise control of the spatial arrangement of nanometer-sized elementary building-blocks during the “bottom-up” construction of two-dimensional monolayers is the key step to get well-defined functional surfaces. Recently, a fundamental progress has been made with the demonstration that covalent linkages between organic molecules can be created directly on a metal surface, leading to the emergence of the field of on-surface synthesis. In this way, original reaction pathways can be explored thanks to the strong catalytic activity of the underlying metal substrate.[1] However, difficulties are usually encountered during the delicate growth mode, and side reactions and undesirable by-product formation are difficult to control. The development of 2D covalent systems based on new and more efficient chemistries or with controllable growth conditions is highly necessary and will condition the future of this emerging technology.[2]

Boronic acids can undergo a self-condensation (dehydration) reaction to create rigid boroxine rings and a planar polymer sheet. By using 1,4-benzenediboronic acid (BDBA) evaporated onto a well-defined metal surface extended nanoporous 2D networks could grow. I will present scanning tunneling microscopy (STM) results of our group, [3-9] reflecting various efforts to control the growth process of these two-dimensional covalent organic networks (influence of the deposition parameters, local activation of the reaction, coupling with an Ullmann reaction, etc.).

In another work we investigated the catalytic behavior of well-defined low-index surfaces of single crystal silver substrates representing a model catalyst for the bimodal homo-coupling reaction of an indacene-tetrone precursor. Dehydrogenation of the precursor occurred upon adsorption, representing a first intermediate state. Covalent coupling was obtained after thermal activation and its chemical signature was measured by vibrational spectroscopy using HREELS (high resolution electron energy loss spectroscopy).[10] We found that on Ag(100) the temperature can achieve selectivity in the reaction pathway leading to distinct products. Most interestingly, the crystallographic symmetry of the supporting surface is very effective in controlling its catalytic strength and/or the reaction product type.[11] In particular, the (111)-oriented surface appeared to be the most reactive as compared to (100) or (110) surfaces.

1. Clair, S.; Abel, M.; Porte, L., Growth of boronic acid based two-dimensional covalent networks on a metal surface under ultrahigh vacuum. Chem. Comm. 2014, 50, 9627-9635.
2. Clair, S.; De Oteyza, D. G., Controlling a chemical coupling reaction on a surface: tools and strategies for on-surface synthesis. In preparation
3. Faury, T.; Dumur, F.; Clair, S.; Abel, M.; Porte, L.; Gigmes, D., Side Functionalization of Diboronic Acid Precursors for Covalent Organic Frameworks. CrystEngComm 2013, 15, 2067–2075.
4. Faury, T.; Clair, S.; Abel, M.; Dumur, F.; Gigmes, D.; Porte, L., Sequential linking to control the growth of a surface covalent organic framework. Journal of Physical Chemistry C 2012, 116, 4819.
5. Clair, S.; Ourdjini, O.; Abel, M.; Porte, L., Two-dimensional polymer as a mask for surface nanopatterning. Advanced Materials 2012, 24, 1252.
6. Clair, S.; Ourdjini, O.; Abel, M.; Porte, L., Tip- or electron beam-induced surface polymerization. Chemical Communications 2011, 47, 8028.
7. Ourdjini, O.; Pawlak, R.; Abel, M.; Clair, S.; Chen, L.; Bergeon, N.; Sassi, M.; Oison, V.; Debierre, J.-M.; Coratger, R.; Porte, L., Substrate-mediated ordering and defect analysis of a surface covalent organic framework. Phys. Rev. B 2011, 84, 125421.
8. Pawlak, R.; Nony, L.; Bocquet, F.; Olson, V.; Sassi, M.; Debierre, J. M.; Loppacher, C.; Porte, L., Supramolecular Assemblies of 1,4-Benzene Diboronic Acid on KCl(001). Journal of Physical Chemistry C 2010, 114, 9290-9295.
9. Zwaneveld, N. A. A.; Pawlak, R.; Abel, M.; Catalin, D.; Gigmes, D.; Bertin, D.; Porte, L., Organized Formation of 2D Extended Covalent Organic Frameworks at Surfaces. J. Am. Chem. Soc. 2008, 130, 6678-6679.
10. Kalashnyk, N.; Mouhat, K.; Oh, J.; Jung, J.; Xie, Y.; Salomon, E.; Angot, T.; Dumur, F.; Gigmes, D.; Clair, S., On-surface synthesis of aligned functional nanoribbons monitored by scanning tunneling microscopy and vibrational spectroscopy. Nat. Commun. 2017, 8, 14735.
11. Kalashnyk, N.; Salomon, E.; Mun, S. H.; Jung, J.; Giovanelli, L.; Angot, T.; Dumur, F.; Gigmes, D.; Clair, S., The Orientation of Silver Surfaces Drives the Reactivity and the Selectivity in Homo‐Coupling Reactions. ChemPhysChem 2018, 19, 1802-1808.

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Cette conférence est présentée par le RQMP Versant Nord du Département de physique de l'Université de Montréal et de Génie physique de la Polytechnique.

Surface-supported covalent organic networks - Sylvain Clair (CNRS, Aix-Marseille)