An official website of the United States government
Abstract Due to their diverse potential in advanced electronics and energy technologies, electrically conducting metal‐organic frameworks (MOFs) are drawing significant attention. Although hexagonal 2D MOFs generally display impressive electrical conductivity because of their dual in‐plane (through bonds) and out‐of‐plane (through π‐stacked ligands) charge transport pathways, notable differences between these two orthogonal conduction routes cause anisotropic conductivity and lower bulk conductivity. To address this issue, we have developed the first redox‐complementary dual‐ligand 2D MOF Cu3(HHTP)(HHTQ), featuring a π‐donor hexahydroxytriphenylene (HHTP) ligand and a π‐acceptor hexahydroxytricycloquinazoline (HHTQ) ligand located at alternate corners of the hexagons, which form either parallel HHTP and HHTQ stacks (AA stacking) or alternating HHTP/HHTQ stacks (AB stacking) along the c‐axis. Regardless of the stacking pattern, Cu3(HHTP)(HHTQ) supports more effective out‐of‐plane conduction through either separate π‐donor and π‐acceptor stacks or alternating π‐donor/acceptor stacks, while promoting in‐plane conduction through the pushpull‐like heteroleptic coordination network. As a result, Cu3(HHTP)(HHTQ) exhibits higher bulk conductivity (0.12 S/m at 295 K) than single‐ligand MOFs Cu3(HHTP)2(7.3 × 10−2S/m) and Cu3(HHTQ)2(5.9 × 10−4S/m). This work introduces a new design approach to improve the bulk electrical conductivity of 2D MOFs by supporting charge transport in both in‐ and out‐of‐plane direcations.
more »
« less
This content will become publicly available on August 22, 2026
From an insulating Zn-porphyrin metallacage to electrically conducting inclusion complexes featuring extended π-donor/acceptor stacks
p-Donor/Acceptor charge-transfer (CT) interactions between redox-complementary p-systems often give rise to non-native optical and electronic properties that are beneficial for modern electronics and energy technologies. However, the formation of extended supramolecular p-donor/acceptor stacks capable of long-range charge transport requires ingenious design strategies that can help reinforce otherwise weak p-donor/acceptor noncovalent interactions. Herein, we demonstrate that a large tetragonal prismatic metal–organic cage (MOC28+) having two parallel p-donor tetrakis(4- carboxyphenyl)-Zn-porphyrin (ZnTCPP) faces located B14 Å apart can accommodate up to three redox-complementary planar aromatic guests (either three p-acceptor guests or two p-acceptors surrounding one p-donor guest) between the ZnTCPP faces, forming extended p-donor/acceptor stacks. While empty MOC28+ behaves as an insulator due to the lack of charge delocalization across its large cavity, its inclusion complexes saturated with p-acidic hexaazatriphenylene hexacarbonitrile (HATHCN) and hexacyanotriphenylene (HCTP) displayed noticeably higher electrical conductivity (8.7 10 6 and 1.3 10 6 S m 1, respectively) owing to more facile charge transport through the p-donor/ acceptor stacks composed of the p-acidic guests intercalated between the ZnTCPP faces. Thus, this work demonstrates that tetragonal prismatic metallacages with two parallel electroactive faces can facilitate the creation of extended p-donor/acceptor stacks by encapsulating redox-complementary planar guests, which in turn facilitates through-space charge delocalization, generating non-native electrical conductivity.
more »
« less
- PAR ID:
- 10630561
- Publisher / Repository:
- Royal Society of Chemistry, UK
- Date Published:
- Journal Name:
- Materials Advances
- ISSN:
- 2633-5409
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Two‐dimensional graphitic metal–organic frameworks (GMOF) often display impressive electrical conductivity chiefly due to efficient through‐bond in‐plane charge transport, however, less efficient out‐of‐plane conduction across the stacked layers creates large disparity between two orthogonal conduction pathways and dampens their bulk conductivity. To address this issue and engineer higher bulk conductivity in 2D GMOFs, we have constructed via an elegant bottom‐up method the first π‐intercalated GMOF (iGMOF1) featuring built‐in alternate π‐donor/acceptor (π‐D/A) stacks of CuII‐coordinated electron‐rich hexaaminotriphenylene (HATP) ligands and non‐coordinatively intercalated π‐acidic hexacyano‐triphenylene (HCTP) molecules, which facilitated out‐of‐plane charge transport while the hexagonal Cu3(HATP)2scaffold maintained in‐plane conduction. As a result, iGMOF1 attained an order of magnitude higher bulk electrical conductivity and much smaller activation energy than Cu3(HATP)2(σ=25 vs. 2 S m−1,Ea=36 vs. 65 meV), demostrating that simultaneous in‐plane (through‐bond) and out‐of‐plane (through πD/A stacks) charge transport can generate higher electrical conductivity in novel iGMOFs.more » « less
-
Abstract Conductive polymers largely derive their electronic functionality from chemical doping, processes by which redox and charge‐transfer reactions form mobile carriers. While decades of research have demonstrated fundamentally new technologies that merge the unique functionality of these materials with the chemical versatility of macromolecules, doping and the resultant material properties are not ideal for many applications. Here, it is demonstrated that open‐shell conjugated polymers comprised of alternating cyclopentadithiophene and thiadiazoloquinoxaline units can achieve high electrical conductivities in their native “undoped” form. Spectroscopic, electrochemical, electron paramagnetic resonance, and magnetic susceptibility measurements demonstrate that this donor–acceptor architecture promotes very narrow bandgaps, strong electronic correlations, high‐spin ground states, and long‐range π‐delocalization. A comparative study of structural variants and processing methodologies demonstrates that the conductivity can be tuned up to 8.18 S cm−1. This exceeds other neutral narrow bandgap conjugated polymers, many doped polymers, radical conductors, and is comparable to commercial grades of poly(styrene‐sulfonate)‐doped poly(3,4‐ethylenedioxythiophene). X‐ray and morphological studies trace the high conductivity to rigid backbone conformations emanating from strong π‐interactions and long‐range ordered structures formed through self‐organization that lead to a network of delocalized open‐shell sites in electronic communication. The results offer a new platform for the transport of charge in molecular systems.more » « less
-
Abstract Supercapacitors have emerged as an important energy storage technology offering rapid power delivery, fast charging, and long cycle lifetimes. While extending the operational voltage is improving the overall energy and power densities, progress remains hindered by a lack of stable n‐type redox‐active materials. Here, a new Faradaic electrode material comprised of a narrow bandgap donor−acceptor conjugated polymer is demonstrated, which exhibits an open‐shell ground state, intrinsic electrical conductivity, and enhanced charge delocalization in the reduced state. These attributes afford very stable anodes with a coulombic efficiency of 99.6% and that retain 90% capacitance after 2000 charge–discharge cycles, exceeding other n‐dopable organic materials. Redox cycling processes are monitored in situ by optoelectronic measurements to separate chemical versus physical degradation mechanisms. Asymmetric supercapacitors fabricated using this polymer with p‐type PEDOT:PSS operate within a 3 V potential window, with a best‐in‐class energy density of 30.4 Wh kg−1at a 1 A g−1discharge rate, a power density of 14.4 kW kg−1at a 10 A g−1discharge rate, and a long cycle life critical to energy storage and management. This work demonstrates the application of a new class of stable and tunable redox‐active material for sustainable energy technologies.more » « less
-
null (Ed.)A new electrically conducting 3D metal-organic framework (MOF) with a unique architecture was synthesized using 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (TCPB) a redox-active cis -dipyridyl-tetrathiafulvalene ( Z -DPTTF) ligand. While TCPB formed Zn 2 (COO) 4 secondary building units (SBUs), instead of connecting the Zn 2 -paddlewheel SBUs located in different planes and forming a traditional pillared paddlewheel MOF, the U-shaped Z -DPTTF ligands bridged the neighboring SBUs formed by the same TCPB ligand like a sine-curve along the b axis that created a new sine -MOF architecture. The pristine sine -MOF displayed an intrinsic electrical conductivity of 1 × 10 −8 S/m, which surged to 5 × 10 −7 S/m after I 2 doping due to partial oxidation of electron rich Z -DPTTF ligands that raised the charge-carrier concentration inside the framework. However, the conductivities of the pristine and I 2 -treated sine -MOFs were modest possibly because of large spatial distances between the ligands that prevented π-donor/acceptor charge-transfer interactions needed for effective through-space charge movement in 3D MOFs that lack through coordination-bond charge transport pathways.more » « less
