Oriented 2D Covalent Organic Framework Thin Films on Single-Layer Graphene

Abstract

Covalent organic frameworks (COFs), in which molecular building blocks form robust microporous networks, are usually synthesized as insoluble and unprocessable powders. We have grown two-dimensional (2D) COF films on single-layer graphene (SLG) under operationally simple solvothermal conditions. The layered films stack normal to the SLG surface and show improved crystallinity compared with COF powders. We used SLG surfaces supported on copper, silicon carbide, and transparent fused silica (SiO(2)) substrates, enabling optical spectroscopy of COFs in transmission mode. Three chemically distinct COF films grown on SLG exhibit similar vertical alignment and long-range order, and two of these are of interest for organic electronic devices for which thin-film formation is a prerequisite for characterizing their optoelectronic properties.

Dirac Cones in two-dimensional conjugated polymer networks

“…1b using a trivalent 1,3,5-triazine connecting group. 2D COFs can now be synthesized using dynamic covalent chemistry in milligram quantities 9 organic monomers, with solvothermal 10 , microwave 11,12 and ionothermal 13,14 synthesis in solution or directly as monolayers on metallic 15 and graphitic 16,17 substrates. Solution-based monoand few-layer sheets can now be produced at micron diameters, highly crystalline 18 and largely defect-free 19 .…”

Nanoscale assembly into extended and continuous structures and hybrid materials

“…108 By synthesizing these materials in the presence of a single layer of graphene on a substrate, Dichtel prepared graphene surfaces functionalized with one or a few covalent organic framework (COF) sheets, in which the pores of the COF oriented normal to the surface (Figure 7b). 109 Better long range order improves the crystallinity of the COF on graphene relative to solution-assembled COFs, and direct routes for charge transport through the COF to graphene become apparent. This method works to assemble various COFs with pore sizes up to 4.7 nm, giving tubular pores that can be filled with complementary electronic materials, such as fullerenes, to give percolated networks ideal for PV applications.…”

A Toolbox for Controlling the Energetics and Localization of Electronic States in Self‐Assembled Organic Monolayers

“…When using organic semiconductors, quantum wells have been realized by a successive evaporation of layers with a thickness of only a few nanometers 15, 16, 17, 18, 19. A controlled periodic variation of the properties of organic structures within 2D layers has been discussed in the context of covalent organic frameworks (i.e., 2D polymers),20, 21 where wave‐function localization can be efficiently tuned by the chemical nature of the used building blocks 22. Beyond that also for more complex (metal–organic) interfaces adsorbate‐induced 1D or 0D quantum‐confinement effects have been discussed recently 23, 24…”