Engineering of flat bands and Dirac bands in two-dimensional covalent organic frameworks (COFs): relationships among molecular orbital symmetry, lattice symmetry, and electronic-structure characteristics
TLDR
In this paper , the fundamental relationships among the COF electronic structures, the symmetries of their 2D lattices, and the frontier molecular orbitals (MOs) of their core and linker components are discussed.Abstract:
Two-dimensional covalent organic frameworks (2D-COFs), also referred to as 2D polymer networks, display unusual electronic-structure characteristics, which can significantly enrich and broaden the fields of electronics and spintronics. In this Focus article, our objective is to lay the groundwork for the conceptual description of the fundamental relationships among the COF electronic structures, the symmetries of their 2D lattices, and the frontier molecular orbitals (MOs) of their core and linker components. We focus on monolayers of hexagonal COFs and use tight-binding model analyses to highlight the critical role of the frontier-MO symmetry, in addition to lattice symmetry, in determining the nature of the electronic bands near the Fermi level. We rationalize the intriguing feature that, when the core unit has degenerate highest occupied MOs [or lowest unoccupied MOs], the COF highest valence band [or lowest conduction band] is flat but degenerate with a dispersive band at a high-symmetry point of the Brillouin zone; the consequences of having such band characteristics are briefly described. Multi-layer and bulk 2D COFs are found to maintain the salient features of the monolayer electronic structures albeit with a reduced bandgap due to the interlayer coupling. This Focus article is thus meant to provide an effective framework for the engineering of flat and Dirac bands in 2D polymer networks. read more
Citations
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Emergence of a Two-Dimensional Topological Dirac Semimetal Phase in a Phthalocyanine-Based Covalent Organic Framework
TL;DR: In this article , a two-dimensional topological Dirac semimetal phase in a phthalocyanine-based COF consisting of only light elements (H, C, N, and F) was realized via density functional theory calculations.
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Electronic Structure of Zinc-5,10,15,20-tetraethynylporphyrin: Evolution from the Molecule to a One-Dimensional Chain, a Two-Dimensional Covalent Organic Framework, and a Nanotube
Xiaojuan Ni,Jean-Luc Brédas +1 more
TL;DR: In this paper , the effects of dimensionality on the electronic structure of Zn-TEP by describing the fundamental relationship between the frontier molecular orbitals and the electronic bands in periodic lattices.
Journal ArticleDOI
On-Surface Synthesis toward Two-Dimensional Polymers.
TL;DR: In this article , the authors introduce exotic band structures of organic frameworks holding honeycomb, kagome, and Lieb lattices, and discuss how mesoscale ordered 2D polymers can be synthesized by means of choosing suitable monomers and optimizing growth conditions.
Journal ArticleDOI
Vanishing Electronic Band Gap in Two-Dimensional Hydrogen-Bonded Organic Frameworks
TL;DR: In this paper , the concept of two-dimensional donor-acceptor (DA) hydrogen-bonded organic frameworks (HOFs) was introduced as a general design strategy to realize low-band-gap flat-band materials.
Journal ArticleDOI
Understanding the electronic pi-system of 2D covalent organic frameworks with Wannier functions
TL;DR: In this article , a family of hexagonal 2D covalent organic frameworks (COFs) with phenyl and biphenyl spacer units and different chemical linker species is investigated.
References
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Journal ArticleDOI
The electronic properties of graphene
TL;DR: In this paper, the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations, are discussed.
Journal ArticleDOI
Quantum spin Hall effect in graphene
Charles L. Kane,Eugene J. Mele +1 more
TL;DR: Graphene is converted from an ideal two-dimensional semimetallic state to a quantum spin Hall insulator and the spin and charge conductances in these edge states are calculated and the effects of temperature, chemical potential, Rashba coupling, disorder, and symmetry breaking fields are discussed.
Journal ArticleDOI
Unconventional superconductivity in magic-angle graphene superlattices
Yuan Cao,Valla Fatemi,Shiang Fang,Kenji Watanabe,Takashi Taniguchi,Efthimios Kaxiras,Pablo Jarillo-Herrero +6 more
TL;DR: The realization of intrinsic unconventional superconductivity is reported—which cannot be explained by weak electron–phonon interactions—in a two-dimensional superlattice created by stacking two sheets of graphene that are twisted relative to each other by a small angle.
Journal ArticleDOI
Porous, Crystalline, Covalent Organic Frameworks
Adrien P. Côté,Annabelle I. Benin,Nathan W. Ockwig,Michael O'Keeffe,Adam J. Matzger,Omar M. Yaghi +5 more
TL;DR: Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid and hexahydroxytriphenylene to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms.
Journal ArticleDOI
An Extended Hückel Theory. I. Hydrocarbons
TL;DR: The Huckel theory, with an extended basis set consisting of 2s and 2p carbon and 1s hydrogen orbitals, with inclusion of overlap and all interactions, yields a good qualitative solution of most hydrocarbon conformational problems.