On-surface Synthesis of Single-layered 2D Covalent Organic Frameworks via Solid-Vapor Interface Reactions
Xuan-He Liu, Cui-Zhong Guan, San-Yuan Ding, Wei Wang, Hui-Juan Yan, Dong Wang, and Li-Jun Wan
J. Am. Chem. Soc., 2013, 135 (28), pp 10470–10474
Abstract: Surface covalent organic frameworks (SCOFs), featured by atomic thick sheet with covalently bonded organic building units, are promised to possess unique properties associated with reduced dimensionality, well-defined in-plane structure, and tunable functionality. Although a great deal of efforts has been made to obtain SCOFs with different linkages and building blocks via both “top-down” exfoliation and “bottom-up” on surface synthesis approaches, the obtained SCOFs generally suffer a low crystallinity, which impedes the understanding of intrinsic properties of the materials. Herein, we demonstrate a self-limiting solid-vapor interface reaction strategy to fabricate highly ordered SCOFs. The coupling reaction is tailored to take place at the solid-vapor interface by introducing one precursor via vaporization to the surface pre-loaded with the other precursor. Following this strategy, highly ordered honeycomb SCOFs with imine linkage are obtained. The controlled formation of SCOFs in our study shows the possibility to a rational design and synthesis of SCOFs with desired functionality.
Figure 1. The schematic diagram of SCOFs formation. (a) Condensation of two precursors A and B carrying different reactive partner groups results in the formation of SCOF. (b) Scheme diagram for solid-vapor interface reaction. c,d, Condensation of trigonal precursors TAPB or TFB and linear precursors TPA or PPDA can form SCOF-IC1 or SCOF-LZU1 respectively. The expected lattice parameters are indicated.
Figure 2. Schematic diagrams of the proposed formationmechanism of the SCOF. (a) The nucleation and enlargement of the SCOF flakes by self-limiting solid-vapor interface reaction strategy. (b) The less-ordered SCOF formation process in the control experiments by heating the substrate pre-loaded with two precursors.