A Scanning Tunneling Microscopy Study on Surface-Supported Imine-Based Covalent Organic Frameworks: a New Design for Robust 2D Materials.

Two-dimensional covalent organic frameworks (2D COFs) are bidimensional sheets of ordered crystalline porous material that stack and form a layered eclipsed structure with periodically aligned columns By decreasing their thickness down to the monolayer, an atom-thick sheet of crystalline organic material can be achieved. In this manner, graphene properties can be targeted, while maintaining COF advantages (e.g. chemical versatility). In order to achieve single-layer COFs, one possibility is to exfoliate the 2D bulk material. Alternatively, a bottom-up approach can be followed and use a surface to template the synthesis of the COF. By using a conductive substrate such as highly oriented pyrolytic graphite (HOPG), the on-surface synthetic process can be followed in situ by scanning tunneling microscopy (STM). This microscopy technique rises as a powerful tool to carefully scrutiny the reaction product.