A recent review has been published in Coordination Chemistry Reviews about the formation and development of triphenylene-based MOFs and COFs.
New publication in Coordination Chemistry Reviews journal entitled “Conductive properties of triphenylene MOFs and COFs” authored by Dr. Noemí Contreras-Pereda and Dr. Daniel Ruiz-Molina in collaboration with Dr. Salvador Pané (Multi-Scale Robotics Lab, ETH Zurich) and Dr. Josep Puigmartí-Luis (ChemInFlow Group, University of Barcelona). The review has been published in Open Access, thus allowing for free access to all interested researchers.
In this review article, the authors discuss the use of Triphenylene (TP) as the main ingredient for the formation of Metal-Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs). TP is a polycyclic aromatic hydrocarbon consisting of four orthofused benzene rings with one central ring surrounded by the other three in an alternate fashion (see Figure 1), resulting in a large electron cloud with 18 π delocalized electrons.
Figure 1. (a) Chemical structure of a TP molecule. When having identical hexasubstitutions different ligand arise being HHTP for 2,3,6,7,10,11 hexahydroxytriphenylene, HATP for 2,3,6,7,10,11 hexaaminotriphenylene and THT for 2,3,6,7,10,11 triphenylenehexathiol. (b) Schematic of stacking of TP moieties in DLCs forming 1D conducting channels. The supramolecular mesophase structure relies on weak interactions that can be broken upon external stimuli as temperature. (c) Schematic of the stacking of TP moieties in TP-based 2D MOFs and COFs. The crystalline packing ensures a robust structure formed by several hexagonally distributed 1D conducting channels.
There exists a wealth of derivatives of triphenylene as function of the groups R1 and R2 (Figure 1a). For instance, TPs exhibit a supramolecular packing mainly through π-π stacking, further optimized by Van der Waals interactions arising from hexasubstituted long alkyl chains that do not perturbate neither the planarity nor the electronic relocation of the TP core. Precisely, the significant electronic delocalization of the resulting supramolecular structures has made TP derivatives as suitable components for different devices, including sensors for neutral aromatic or cationic guests, molecular rotors, or in highly stable organic-oxygen cell batteries. However, in this review, the authors focus mainly on those where R1 and R2 are equal between them, and incorporate –OH (HHTP), –NH2 (HATP) or -SH (THT) groups.
Overall, the review focuses the attention on:
·Use of active metal ions/triphenylene ligands for the fabrication of MOFs and COFs.
·Synthesis approaches towards control grain boundaries and crystal anisotropy
Finally, a critical discussion regarding challenges and future steps needed in the area is presented to encourage researchers to overcome and fill the gap between the laboratories and the final devices.
ABSTRACT: Triphenylene (TP) based materials have experienced a great expansion in the latest years. TP molecules have interesting optoelectronic properties, arising from the aromatic core, which have been exploited in functional two-dimensional (2D) Metal-Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) aside other organic polymers. In this review we summarize synthetic approaches of TP-based 2D MOFs and COFs emphasizing on the resulting morphology, crystalline domains and orientation, proven to have great impact on the properties and performance of these materials in functional devices. Specifically, we report a detailed description on the different TP-based 2D structures detailing the influence of the chemical and crystalline structure on the electronic properties, specially the in-plane and out-of-plane contribution to the electrical conductivity. Finally, we give also attention and present several examples of functional devices made out with these electronic materials with great impact in the literature as well as in future technological applications.
Funding: This work was supported by grant RTI2018-098027-B-C21 from the Spanish Government funds and by the European Regional Development Fund (ERDF). The ICN2 is funded by the CERCA programme / Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, grant no. SEV-2017-0706). N. C.-P. acknowledges the support of fellowship from “laCaixa” Foundation (ID 100010434). The fellowship code is LCF/BQ/ES17/11600012. J. P.-L. acknowledges support from the European Research Council Starting Grant microCrysFact (ERC-2015-STG No. 677020), the Swiss National Science Foundation (project no. 200021_181988), and grant PID2020-116612RB-C33 funded by MCIN/ AEI /10.13039/501100011033. S.P. acknowledges support from the ERC-2017-CoG HINBOTS Grant No. 771565.