Charge Transport Pathways of π‐Conjugated Metal–Organic Frameworks

2020 ◽  
Vol 41 (6) ◽  
pp. 592-594 ◽  
Author(s):  
Seok Min Yoon

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2372
Author(s):  
Christian Winkler ◽  
Egbert Zojer

In recent years, charge transport in metal-organic frameworks (MOFs) has shifted into the focus of scientific research. In this context, systems with efficient through-space charge transport pathways resulting from π-stacked conjugated linkers are of particular interest. In the current manuscript, we use density functional theory-based simulations to provide a detailed understanding of such MOFs, which, in the present case, are derived from the prototypical Zn2(TTFTB) system (with TTFTB4− corresponding to tetrathiafulvalene tetrabenzoate). In particular, we show that factors such as the relative arrangement of neighboring linkers and the details of the structural conformations of the individual building blocks have a profound impact on bandwidths and charge transfer. Considering the helical stacking of individual tetrathiafulvalene (TTF) molecules around a screw axis as the dominant symmetry element in Zn2(TTFTB)-derived materials, the focus, here, is primarily on the impact of the relative rotation of neighboring molecules. Not unexpectedly, changing the stacking distance in the helix also plays a distinct role, especially for structures which display large electronic couplings to start with. The presented results provide guidelines for achieving structures with improved electronic couplings. It is, however, also shown that structural defects (especially missing linkers) provide major obstacles to charge transport in the studied, essentially one-dimensional systems. This suggests that especially the sample quality is a decisive factor for ensuring efficient through-space charge transport in MOFs comprising stacked π-systems.



2020 ◽  
Author(s):  
Lilia S. Xie ◽  
Sarah S. Park ◽  
Michał J. Chmielewski ◽  
Hanyu Liu ◽  
Ruby A. Kharod ◽  
...  

<p>The extension of reticular chemistry concepts to electrically conductive three-dimensional metal-organic frameworks (MOFs) has been challenging, particularly for cases in which strong interactions between electroactive linkers create the charge transport pathways. Here, we report the successful replacement of tetrathiafulvalene (TTF) with a nickel glyoximate core in a family of isostructural conductive MOFs with Mn<sup>2+</sup>, Zn<sup>2+</sup>, and Cd<sup>2+</sup>. Different coordination environments of the framework metals lead to variations in the linker stacking geometries and optical properties. Single crystal conductivity data are consistent with charge transport along the linker stacking direction, with conductivity values only slightly lower than those reported for the analogous TTF materials. These results serve as a case study demonstrating how reticular chemistry design principles can be extended to conductive frameworks with significant intermolecular contacts.</p>



2020 ◽  
Author(s):  
Lilia S. Xie ◽  
Sarah S. Park ◽  
Michał J. Chmielewski ◽  
Hanyu Liu ◽  
Ruby A. Kharod ◽  
...  

<p>The extension of reticular chemistry concepts to electrically conductive three-dimensional metal-organic frameworks (MOFs) has been challenging, particularly for cases in which strong interactions between electroactive linkers create the charge transport pathways. Here, we report the successful replacement of tetrathiafulvalene (TTF) with a nickel glyoximate core in a family of isostructural conductive MOFs with Mn<sup>2+</sup>, Zn<sup>2+</sup>, and Cd<sup>2+</sup>. Different coordination environments of the framework metals lead to variations in the linker stacking geometries and optical properties. Single crystal conductivity data are consistent with charge transport along the linker stacking direction, with conductivity values only slightly lower than those reported for the analogous TTF materials. These results serve as a case study demonstrating how reticular chemistry design principles can be extended to conductive frameworks with significant intermolecular contacts.</p>



2020 ◽  
Author(s):  
Jesse Park ◽  
Brianna Collins ◽  
Lucy Darago ◽  
Tomce Runcevski ◽  
Michael Aubrey ◽  
...  

<b>Materials that combine magnetic order with other desirable physical attributes offer to revolutionize our energy landscape. Indeed, such materials could find transformative applications in spintronics, quantum sensing, low-density magnets, and gas separations. As a result, efforts to design multifunctional magnetic materials have recently moved beyond traditional solid-state materials to metal–organic solids. Among these, metal–organic frameworks in particular bear structures that offer intrinsic porosity, vast chemical and structural programmability, and tunability of electronic properties. Nevertheless, magnetic order within metal–organic frameworks has generally been limited to low temperatures, owing largely to challenges in creating strong magnetic exchange in extended metal–organic solids. Here, we employ the phenomenon of itinerant ferromagnetism to realize magnetic ordering at <i>T</i><sub>C</sub> = 225 K in a mixed-valence chromium(II/III) triazolate compound, representing the highest ferromagnetic ordering temperature yet observed in a metal–organic framework. The itinerant ferromagnetism is shown to proceed via a double-exchange mechanism, the first such observation in any metal–organic material. Critically, this mechanism results in variable-temperature conductivity with barrierless charge transport below <i>T</i><sub>C</sub> and a large negative magnetoresistance of 23% at 5 K. These observations suggest applications for double-exchange-based coordination solids in the emergent fields of magnetoelectrics and spintronics. Taken together, the insights gleaned from these results are expected to provide a blueprint for the design and synthesis of porous materials with synergistic high-temperature magnetic and charge transport properties. </b>



Author(s):  
Jiajun Song ◽  
Jianzhong Zheng ◽  
Anneng Yang ◽  
Hong Liu ◽  
Zeyu Zhao ◽  
...  

Two-dimensional (2D) conductive metal-organic frameworks (MOFs) can not only inherit the high porosity and tailorability of traditional MOFs but also exhibit unique charge transport properties, offering promising opportunities for applications...



2020 ◽  
Vol 11 (28) ◽  
pp. 7468-7478
Author(s):  
Ben A. Johnson ◽  
Sascha Ott

This report presents diagnostic criteria for determining the limiting processes of MOF-based catalysis: either mass/charge transport or the intrinsic reaction rate. This will facilitate future catalytic material design.



2020 ◽  
Vol 49 (15) ◽  
pp. 5601-5638 ◽  
Author(s):  
Víctor Rubio-Giménez ◽  
Sergio Tatay ◽  
Carlos Martí-Gastaldo

This review aims to reassess the progress, issues and opportunities in the path towards integrating conductive and magnetically bistable coordination polymers and metal–organic frameworks as active components in electronic devices.



2020 ◽  
Vol 59 (44) ◽  
pp. 19623-19626 ◽  
Author(s):  
Lilia S. Xie ◽  
Sarah S. Park ◽  
Michał J. Chmielewski ◽  
Hanyu Liu ◽  
Ruby A. Kharod ◽  
...  


2020 ◽  
Author(s):  
Grigorii Skorupskii ◽  
Mircea Dinca

Electrically conductive metal-organic frameworks (MOFs) provide a rare example of porous materials that can efficiently transport electrical current, a combination favorable for a variety of technological applications. The vast majority of such MOFs are highly anisotropic in both their structures and properties: only two electrically conductive MOFs reported to date exhibit cubic structures that enable isotropic charge transport. Here, we report a new family of intrinsically porous frameworks made from rare earths and hexahydroxytriphenylene that are cubic, porous, and intrinsically conductive with conductivities reaching 10−5 S/cm and surface areas of up to 780 m2/g. By expanding the list of MOFs with isotropic charge transport, these results will help improve our understanding of design strategies for porous electronic materials.<br>



ACS Nano ◽  
2016 ◽  
Vol 10 (7) ◽  
pp. 7085-7093 ◽  
Author(s):  
Tobias Neumann ◽  
Jianxi Liu ◽  
Tobias Wächter ◽  
Pascal Friederich ◽  
Franz Symalla ◽  
...  


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