Rolling the 2D Sheets of Conjugated Covalent Organic Framework: Transforming into 1D Electronically Conductive Nanotubes

Abstract

Mimicking the interconvertible carbon allotropes of 2-dimensional (2D) graphene and 1-dimensional (1D) carbon nanotubes, herein we report the in-situ transformation of 2D conjugated covalent organic frameworks (COFs) sheet into 1D nanotubular structures via self-assembly the sheets at solvent interfaces. The facile “roll-the sheets” self-assembly resulted in coaxial nanotubes with uniform cross-sectional diameter, which was realized for aza-pyrene based COF instead of pyrene COF, although both possess very similar chemical structure. Upon replacing the carbon atoms at 2,7-positions of pyrene with nitrogen, contrasting optical and electronic properties was realized reflecting the rolled structure of the conjugated 2D sheets. The nanotubes exhibited semiconducting nature with stable conducting pathways at ambient conditions. The aza centers act as the point for charge carrier doping as evident from the photoconductivity and electrical conductivity results.