Understanding the origin of serrated stacking motifs in planar two-dimensional covalent organic frameworks

Winkler, Christian; Kamencek, Tomas; Zojer, Egbert

doi:10.1039/d1nr01047f

Cited by 12 publications

(34 citation statements)

References 81 publications

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“…The reason for this evolution is that the equilibrium distance results from an interplay between van der Waals attraction (which drops with diminishing lateral overlap of neighboring pentacenes), Pauli repulsion (which also depends on the overlap and essentially scales with the widths of the occupied bands), 36 and Coulombic interaction (mostly attractive due to charge penetration effects), 52−54 which again drop with the overlap of neighboring molecules. 36,37 These factors then typically play out such that the intermolecular overlap has only rather little impact on the equilibrium distance and, consequently, the equilibrium distance changes only slightly upon increasing the stacking distance (see schematic drawing in Figure 2e). This triggers a continuous increase of the tilt angle of the π-planes relative to the a 1 ,a 2plane from 55.2°to 68.0°for the considered range of a 3 values, as shown in the Supporting Information.…”

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confidence: 99%

“…The crucial advantage is that in such MOFs the relative arrangement of the π-systems can be controlled via the network structure rather than following from the direct interactions of the conjugated units. This is insofar relevant, as interactions between π-conjugated materials favor packings with unfavorable transport properties, as this also minimizes intermolecular exchange repulsion. − Suitably designed MOFs have the potential to overcome this driving force. Nevertheless, the through-space charge carrier mobilities of MOFs are typically ≪1 cm 2 V –1 s –1 .…”

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confidence: 99%

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Maximizing the Carrier Mobilities of Metal–Organic Frameworks Comprising Stacked Pentacene Units

Zojer

Winkler

2021

J. Phys. Chem. Lett.

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Charge transport properties of metal–organic frameworks (MOFs) are of distinct interest for (opto)electronic applications. In contrast to the situation in molecular crystals, MOFs allow an extrinsic control of the relative arrangement of π-conjugated entities through the framework architecture. This suggests that MOFs should enable materials with particularly high through-space charge carrier mobilities. Such materials, however, do not yet exist, despite the synthesis of MOFs with, for example, seemingly ideally packed stacks of pentacene-bearing linkers. Their rather low mobilities have been attributed to dynamic disorder effects. Using dispersion-corrected density functional theory calculations, we show that this is only part of the problem and that targeted network design involving comparably easy-to-implement structural modifications have the potential to massively boost charge transport. For the pentacene stacks, this is related to the a priori counterintuitive observation that the electronic coupling between neighboring units can be strongly increased by increasing the stacking distance.

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confidence: 99%

Maximizing the Carrier Mobilities of Metal–Organic Frameworks Comprising Stacked Pentacene Units

Zojer

Winkler

2021

J. Phys. Chem. Lett.

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“…This decomposition scheme combines the electron densities of the isolated fragments to calculate the classical electrostatic energy. 65 , 67 − 69 These calculations were performed with a code designed for periodic systems (see ref ( 65 ) for details). To emulate a cluster system, the molecules were placed in a 25 × 25 × 50 Å unit cell.…”

Section: Methodsmentioning

confidence: 99%

Interfacial Charge Transfer Influences Thin-Film Polymorphism

et al. 2022

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The structure and chemical composition are the key parameters influencing the properties of organic thin films deposited on inorganic substrates. Such films often display structures that substantially differ from the bulk, and the substrate has a relevant influence on their polymorphism. In this work, we illuminate the role of the substrate by studying its influence on para -benzoquinone on two different substrates, Ag(111) and graphene. We employ a combination of first-principles calculations and machine learning to identify the energetically most favorable structures on both substrates and study their electronic properties. Our results indicate that for the first layer, similar structures are favorable for both substrates. For the second layer, we find two significantly different structures. Interestingly, graphene favors the one with less, while Ag favors the one with more electronic coupling. We explain this switch in stability as an effect of the different charge transfer on the two substrates.

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“…In conclusion, intensive investigations in COF films started a decade ago and topped last year. Thus, the recent developments on the characterization methods with adaptation of advanced techniques will indeed improve the understanding on the fundamental properties of COFs, which will surely lead to their better utilization [84,85,[110][111][112]. Furthermore, increasing numbers of consortiums on solar fuel production will pave the way for further collaborations with expert researchers in organo-electronics and porous materials, which will probably result in better integration of COFs to organic electronic devices, and help them to demonstrate their full potential.…”

Section: Outlook and Conclusionmentioning

confidence: 99%

Have Covalent Organic Framework Films Revealed Their Full Potential?

Bildirir

2021

Crystals

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Porous organic polymers provide high accessible surface areas, which make them attractive for gas storage, separation, and catalysis. In addition to those classical usage areas, such compounds are particularly interesting for electronic applications since their high dimensional, electron-rich backbone provides advanced electronic and photophysical properties. However, their non-soluble nature is a challenge for their processability, especially in the case of film formation, hence their limited utilization in organic electronic devices so far. Nevertheless, there are several techniques presented in the literature to overcome that issue, most of which were on the crystalline porous organic polymers, namely covalent organic frameworks (COFs). In this perspective, the developments on COF film formation and prospects for the improvements are discussed with suggestions to further their performances in organic electronics.

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Understanding the origin of serrated stacking motifs in planar two-dimensional covalent organic frameworks

Abstract: Covalent organic frameworks (COFs) have attracted significant attention due to their chemical versatility combined with a significant number of potential applications. Of particular interest are two-dimensional COFs, where the organic...

Cited by 12 publications

References 81 publications

Maximizing the Carrier Mobilities of Metal–Organic Frameworks Comprising Stacked Pentacene Units

Maximizing the Carrier Mobilities of Metal–Organic Frameworks Comprising Stacked Pentacene Units

Interfacial Charge Transfer Influences Thin-Film Polymorphism

Have Covalent Organic Framework Films Revealed Their Full Potential?

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