Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected via diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm2V-1s-1. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.

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Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

10.26434/chemrxiv.7766786 ◽

2019 ◽

Cited By ~ 1

Author(s):

Simil Thomas ◽

Hong Li ◽

Raghunath R. Dasari ◽

Austin Evans ◽

William Dichtel ◽

...

Keyword(s):

Charge Transport ◽

Organic Semiconductors ◽

Density Functional ◽

Polymer Networks ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

X Ray Diffraction ◽

Zinc Porphyrin ◽

Design And Synthesis ◽

Predicted Values

We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected via diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm2V-1s-1. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.

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Buckling of Two-Dimensional Covalent Organic Frameworks Under Thermal Stress

10.26434/chemrxiv.7831727.v1 ◽

2019 ◽

Author(s):

Austin Evans ◽

Matthew Ryder ◽

Nathan C. Flanders ◽

Edon Vitaku ◽

Lin Chen ◽

...

Keyword(s):

Thermal Stability ◽

Thermal Stress ◽

Density Functional ◽

Structural Changes ◽

Gravimetric Analysis ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

X Ray Diffraction ◽

Excellent Thermal Stability ◽

X Ray

Two-dimensional Covalent organic frameworks (2D COFs) are periodic, permanently porous, and lightweight solids that are polymerized from topologically designed monomers. The predictable design and structural modularity of these materials make them promising candidates for applications including catalysis, environmental remediation, chemical separations, and organic electronics, many of which will require stability to mechanical and thermal stress. Based on their reinforced structures and high degradation temperatures as determined by thermal gravimetric analysis (TGA), many reports have claimed that COFs have excellent thermal stability. However, their stability to heat and pressure has not been probed using methods that report on structural changes rather than the loss of volatile compounds. Here we explore two structurally analogous 2D COFs with different polymerization chemistries using in operando X-ray diffraction, which demonstrates the loss of crystallinity at lower temperatures than the degradation temperatures measured by TGA. Density functional theory calculations suggest that an asymmetric buckling of the COF lattice is responsible for the observed loss of crystallinity. In addition to their thermal stability, x-ray diffraction of the 2D COFs under gas pressures up to 100 bar showed no loss in crystallinity or structural changes, indicating that these materials are robust to mechanical stress by applied pressure. We expect that these results will encourage further exploration of COF stability as a function of framework design and isolated form, which will guide the design of frameworks that withstand demanding application-relevant conditions.

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Design and synthesis of two-dimensional covalent organic frameworks with four-arm cores: prediction of remarkable ambipolar charge-transport properties

Materials Horizons ◽

10.1039/c9mh00035f ◽

2019 ◽

Vol 6 (9) ◽

pp. 1868-1876 ◽

Cited By ~ 16

Author(s):

Simil Thomas ◽

Hong Li ◽

Raghunath R. Dasari ◽

Austin M. Evans ◽

Ioannina Castano ◽

...

Keyword(s):

Charge Transport ◽

Transport Properties ◽

Experimental Investigations ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

Design And Synthesis

Theoretical and experimental investigations of diacetylene-linked COFs with remarkable charge-transport properties.

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Buckling of Two-Dimensional Covalent Organic Frameworks Under Thermal Stress

10.26434/chemrxiv.7831727 ◽

2019 ◽

Author(s):

Austin Evans ◽

Matthew Ryder ◽

Nathan C. Flanders ◽

Edon Vitaku ◽

Lin Chen ◽

...

Keyword(s):

Thermal Stability ◽

Thermal Stress ◽

Density Functional ◽

Structural Changes ◽

Gravimetric Analysis ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

X Ray Diffraction ◽

Excellent Thermal Stability ◽

X Ray

Two-dimensional Covalent organic frameworks (2D COFs) are periodic, permanently porous, and lightweight solids that are polymerized from topologically designed monomers. The predictable design and structural modularity of these materials make them promising candidates for applications including catalysis, environmental remediation, chemical separations, and organic electronics, many of which will require stability to mechanical and thermal stress. Based on their reinforced structures and high degradation temperatures as determined by thermal gravimetric analysis (TGA), many reports have claimed that COFs have excellent thermal stability. However, their stability to heat and pressure has not been probed using methods that report on structural changes rather than the loss of volatile compounds. Here we explore two structurally analogous 2D COFs with different polymerization chemistries using in operando X-ray diffraction, which demonstrates the loss of crystallinity at lower temperatures than the degradation temperatures measured by TGA. Density functional theory calculations suggest that an asymmetric buckling of the COF lattice is responsible for the observed loss of crystallinity. In addition to their thermal stability, x-ray diffraction of the 2D COFs under gas pressures up to 100 bar showed no loss in crystallinity or structural changes, indicating that these materials are robust to mechanical stress by applied pressure. We expect that these results will encourage further exploration of COF stability as a function of framework design and isolated form, which will guide the design of frameworks that withstand demanding application-relevant conditions.

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Cross-plane transport in a single-molecule two-dimensional van der Waals heterojunction

Science Advances ◽

10.1126/sciadv.aba6714 ◽

2020 ◽

Vol 6 (22) ◽

pp. eaba6714 ◽

Cited By ~ 1

Author(s):

Shiqiang Zhao ◽

Qingqing Wu ◽

Jiuchan Pi ◽

Junyang Liu ◽

Jueting Zheng ◽

...

Keyword(s):

Charge Transport ◽

Single Molecule ◽

Density Functional ◽

Electronic Materials ◽

2D Materials ◽

Molecular Layer ◽

Van Der Waals ◽

Density Functional Theory Calculations ◽

Two Dimensional ◽

Guest Molecules

Two-dimensional van der Waals heterojunctions (2D-vdWHs) stacked from atomically thick 2D materials are predicted to be a diverse class of electronic materials with unique electronic properties. These properties can be further tuned by sandwiching monolayers of planar organic molecules between 2D materials to form molecular 2D-vdWHs (M-2D-vdWHs), in which electricity flows in a cross-plane way from one 2D layer to the other via a single molecular layer. Using a newly developed cross-plane break junction technique, combined with density functional theory calculations, we show that M-2D-vdWHs can be created and that cross-plane charge transport can be tuned by incorporating guest molecules. The M-2D-vdWHs exhibit distinct cross-plane charge transport signatures, which differ from those of molecules undergoing in-plane charge transport.

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Controlling Molecular Assembly and Charge Transport of N-Type Organic Semiconductors with Sterically Demanding Substituents

10.21203/rs.3.rs-93683/v1 ◽

2020 ◽

Author(s):

Craig Yu ◽

Naoya Kojima ◽

Shohei Kumagai ◽

Tadanori Kurosawa ◽

Hiroyuki Ishii ◽

...

Keyword(s):

Charge Transport ◽

Organic Semiconductors ◽

Field Effect Transistors ◽

Molecular Assembly ◽

Fine Tuning ◽

Organic Field Effect Transistors ◽

Molecular Assemblies ◽

Design And Synthesis ◽

Sterically Demanding ◽

The Difference

Abstract Benzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) n-type organic semiconductors demonstrate unique multi-fold intermolecular hydrogen-bonding interactions that lead to excellent aggregated structures, charge transports, and electron mobility. However, the robust intermolecular anchoring of BQQDI presents challenges for further fine-tuning molecular assemblies and organic semiconductor properties. Herein, we report the design and synthesis of two BQQDI derivatives with sterically demanding phenyl- and cyclohexyl-substituted BQQDI (Ph–BQQDI and Cy6–BQQDI), where the two organic semiconductors show distinct molecular assemblies and degrees of intermolecular orbital overlaps. In addition, the difference in their packing motifs led to strikingly different band structures that give rise to contrasting charge-transport capabilities. As a result, Cy6–BQQDI shows excellent transistor performances in both single-crystalline and polycrystalline thin-film organic field-effect transistors.

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Unraveling the Effect of Defects, Domain Size, and Chemical Doping on Photophysics and Charge Transport in Covalent Organic Frameworks

Chemical Science ◽

10.1039/d1sc01262b ◽

2021 ◽

Author(s):

Raja Ghosh ◽

Francesco Paesani

Keyword(s):

Charge Transport ◽

Domain Size ◽

Chemical Doping ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

Physical Mechanisms

Understanding the underlying physical mechanisms that govern charge transport in two-dimensional (2D) covalent organic frameworks (COFs) will facilitate the development of novel COF-based devices for optoelectronic and thermoelectric applications. In this...

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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

Materials Horizons ◽

10.1039/d1mh00935d ◽

2022 ◽

Author(s):

Xiaojuan Ni ◽

Hong Li ◽

Feng Liu ◽

Jean-Luc Bredas

Keyword(s):

Electronic Structure ◽

Molecular Orbital ◽

Polymer Networks ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

Orbital Symmetry ◽

Structure Characteristics ◽

Flat Bands ◽

Lattice Symmetry ◽

2D Polymer

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...

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Approaching isotropic charge transport of n-type organic semiconductors with bulky substituents

Communications Chemistry ◽

10.1038/s42004-021-00583-2 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Craig P. Yu ◽

Naoya Kojima ◽

Shohei Kumagai ◽

Tadanori Kurosawa ◽

Hiroyuki Ishii ◽

...

Keyword(s):

Charge Transport ◽

Organic Semiconductors ◽

Field Effect Transistors ◽

Molecular Assembly ◽

Fine Tuning ◽

Organic Field Effect Transistors ◽

Design And Synthesis ◽

Semiconducting Properties ◽

Transfer Integrals ◽

The Difference

AbstractBenzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) is an n-type organic semiconductor that has shown unique multi-fold intermolecular hydrogen-bonding interactions, leading to aggregated structures with excellent charge transports and electron mobility properties. However, the strong intermolecular anchoring of BQQDI presents challenges for fine-tuning the molecular assembly and improving the semiconducting properties. Herein, we report the design and synthesis of two BQQDI derivatives with phenyl- and cyclohexyl substituents (Ph–BQQDI and Cy6–BQQDI), where the two organic semiconductors show distinct molecular assemblies and degrees of intermolecular orbital overlaps. In addition, the difference in their packing motifs leads to strikingly different band structures that give rise to contrasting charge-transport capabilities. More specifically, Cy6–BQQDI bearing bulky substituents exhibits isotropic intermolecular orbital overlaps resulting in equal averaged transfer integrals in both π-π stacking directions, even when dynamic disorders are taken into account; whereas Ph–BQQDI exhibits anisotropic averaged transfer integrals in these directions. As a result, Cy6–BQQDI shows excellent device performances in both single-crystalline and polycrystalline thin-film organic field-effect transistors up to 2.3 and 1.0 cm2 V−1 s−1, respectively.

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