  Starting from the planar molecule 1,3,5-trihydroxybenzene, Du et al. reported
synthesizing one of a couple of possible 2D materials: graphenylene or
3-carbophene. 3-carbophene is a member of a novel class of two-dimensional
covalent organic framework, [N]-carbophenes (carbophenes). Using a high
throughput method, we computed the formation energies and conduction properties
of 3-, 4-, 5-, and 6-carbophenes with hydroxyl (OH), carbonyl (CO), nitro
(NO$_2$), amine (NH$_2$), carboxyl (COOH) functional groups replacing hydrogen
terminating agents. Five hundred and nine structures with randomly picked
motifs, with functionalizations from a single functional group per cell to
fully functionalized were studied. Our results demonstrate a negatively sloped
linear relationship between the degree of functionalization and formation
energy when the type of functional group and type of carbophene are held
constant. The decrease in formation energy with functionalization makes Du's
synthesis of functionalized 3-carbophene more creditable. The type of
carbophene, type of functional group, and the degree of functionalization all
play a role in the band structure of the materials. For example, CO functional
groups may lead to a mid-gap state pinned to the Fermi level, whereas the other
functional groups studied keep the semiconducting nature of pristine
carbophene. Thus, because carbonyl functional groups are often present in
defected carbon systems, care should be taken to limit the amount of oxygen in
carbophene devices where the band gap is important. Thus, this work strengthens
the hypothesis of Junkermeier et al.'s hypothesis that Du et al. synthesized
3-carbophene and not graphenylene.
