Hexaazatriphenylene-Based Two-Dimensional Conductive Covalent Organic Framework with Anisotropic Charge Transfer

Abstract

The development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor-made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD-COF. With the support of theoretical calculations, we found that the HAT units in the HD-COF induce strong, eclipsed & pi;-& pi; stacking. The unique stacking of HAT units and the weak in-plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD-COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD-COF films showed an electrical conductivity as high as 1.25 S cm-1 after doping with tris(4-bromophenyl)ammoniumyl hexachloroantimonate. Electroactive hexaazatriphenylene (HAT)-dioxin linked covalent organic framework, denoted as HD-COF, was designed, and synthesized. The unique & pi;-& pi; stacking of HAT units and the weak in-plane conjugation of dioxin linkages in the HD-COF structure led to efficient anisotropic charge transport. In situ formed HD-COF film demonstrated enhanced electric conductivity as high as 1.25 S cm-1 after doping with magic blue.+image