2D Conductive Metal Organic Frameworks Research Articles

Metal and ligand modification modulates the electrocatalytic HER, OER, and ORR activity of 2D conductive metal-organic frameworks

Metal and ligand modification modulates the electrocatalytic HER, OER, and ORR activity of 2D conductive metal-organic frameworks

De Novo Design and Facile Synthesis of Highly Crystalline 2D Conductive Metal-Organic Frameworks: A "Rotor-Stator" Strategy.

Two-dimensional conductive metal-organic frameworks (2D c-MOFs), which feature high electrical conductivity and large charge carrier mobility, hold great promise in electronics and optoelectronics. Nevertheless, the limited solubility of commonly used planar ligands inevitably brings challenges in synthesis and purification and causes laborious coordination conditions for screening. Moreover, most reported 2D c-MOFs are polycrystalline powders with relatively low crystallinity and irregular morphology, hindering the unveiling of the detailed structure-function relationship. Herein, we developed a "rotor-stator" molecular design strategy to construct 2D c-MOFs using a delicately designed nonplanar biscarbazole ligand (8OH-DCB). Benefiting from the special "rotor-stator" structure of the ligand, crystals of Cu-DCB-MOF were successfully prepared, allowing for the precise determination of their crystal structure. Interestingly, the crystals of Cu-DCB-MOF can be obtained in various organic solvents, indicating excellent solvent compatibility. The versatility of the "rotor-stator" molecular design strategy was further demonstrated by another two new ligands with a "rotor-stator" structure, and afford corresponding 2D c-MOF crystals (Cu-DCBT-MOF and Cu-DCBBT-MOF). The current work presents a facile approach toward the rational design and direct construction of highly crystalline 2D c-MOFs using nonplanar ligands.

2D Conductive Metal-Organic Frameworks Based on Tetraoxa[8]circulenes as Promising Cathode for Aqueous Zinc Ion Batteries.

Aqueous zinc-ion batteries (ZIBs) are the new generation electrochemical energy storage systems. Recently, two-dimensional conductive metal-organic frameworks (2D c-MOFs) are attractive to serve as cathode materials of ZIBs due to their compositional diversity, abundant active sites, and excellent conductivity. Despite the growing interest in 2D c-MOFs, their application prospects are still to be explored. Herein, a tetraoxa[8]circulene (TOC) derivative with unique electronic structure and interesting redox-active property are synthesized to construct c-MOFs. A series of novel 2D c-MOFs (Cu-TOC, Zn-TOC and Mn-TOC) with different conductivities and packing modes are obtained by combining the linker tetraoxa[8]circulenes-2,3,5,6,8,9,11,12-octaol (8OH-TOC) and corresponding metal ions. Three c-MOFs all exhibit typical semiconducting properties, and Cu-TOC exhibits the highest electrical conductivity of 0.2 S cm-1 among them. Furthermore, their electrochemical performance as cathode materials for ZIBs have been investigated. They all performed high reversible capacity, decent cycle stability and excellent rate capability. This work reveals the key insights into the electrochemical application potential of 2D c-MOFs and advances their development as cathode materials in ZIBs.

A Collaboration for Exploring Fundamental Property–Performance Relationships for Electrochemical Energy Storage

AbstractThis invited Team Profile was created by Jens Matthies Wrogemann. He and his collaborators at the MEET Battery Research Center, the Helmholtz‐Zentrum Berlin für Materialien und Energie GmbH (HZB), and Paderborn University recently published a research article about property–performance relationships of 2D conductive metal–organic frameworks. Flake‐ and rod‐like shaped particles were evaluated to investigate the impact of the particle morphology of MOFs on electrochemical Li+ ion storage. By optimization of the particle morphology, the diffusion limitation of the Faradaic process can be significantly reduced. “Overcoming Diffusion Limitation of Faradaic Processes: Property–Performance Relationships of 2D Conductive Metal–Organic Framework Cu3(HHTP)2 for Reversible Lithium‐Ion Storage”, J. M. Wrogemann, M. J. Lüther, P. Bärmann, M. Lounasvuori, A. Javed, M. Tiemann, R. Golnak, J. Xiao, T. Petit, T. Placke, M. Winter, Angew. Chem. Int. Ed. Engl. 2023, 62, e202303111.

A Collaboration for Exploring Fundamental Property-Performance Relationships for Electrochemical Energy Storage.

This invited Team Profile was created by Jens Matthies Wrogemann. He and his collaborators at the MEET Battery Research Center, the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), and Paderborn University recently published a research article about property-performance relationships of 2D conductive metal-organic frameworks. Flake- and rod-like shaped particles were evaluated to investigate the impact of the particle morphology of MOFs on electrochemical Li+ ion storage. By optimization of the particle morphology, the diffusion limitation of the Faradaic process can be significantly reduced. "Overcoming Diffusion Limitation of Faradaic Processes: Property-Performance Relationships of 2D Conductive Metal-Organic Framework Cu3 (HHTP)2 for Reversible Lithium-Ion Storage", J. M. Wrogemann, M. J. Lüther, P. Bärmann, M. Lounasvuori, A. Javed, M. Tiemann, R. Golnak, J. Xiao, T. Petit, T. Placke, M. Winter, Angew. Chem. Int. Ed. Engl. 2023, 62, e202303111.

Effects of Transition Metals on Metal-Octaaminophthalocyanine-Based 2D Metal-Organic Frameworks.

Metal-octaaminophthalocyanine (MOAPc)-based 2D conductive metal-organic frameworks (cMOFs) have shown great potential in several applications, including sensing, energy storage, and electrocatalysis, due to their bimetallic characteristics. Here, we report a detailed metal substitution study on a family of isostructural cMOFs with Co2+, Ni2+, and Cu2+ as both the metal nodes and the metal centers in the MOAPc ligands. We observed that different metal nodes had variations in the reaction kinetics, particle sizes, and crystallinities. Importantly, the electronic structure and conductivity were found to be dependent on both types of metal sites in the 2D cMOFs. Ni-NiOAPc was found to be the most conductive one among the nine possible combinations with a conductivity of 54 ± 4.8 mS/cm. DFT calculations revealed that monolayer Ni-NiOAPc has neither the smallest bandgap nor the highest charge carrier mobility. Hence its highest conductivity stems from its high crystallinity. Collectively, these results provide structure property relationships for MOAPc-based cMOFs with amino coordination units.

Linker Aromaticity Reduces Band Dispersion in 2D Conductive Metal–Organic Frameworks

Linker Aromaticity Reduces Band Dispersion in 2D Conductive Metal–Organic Frameworks

Molybdenum based 2D conductive Metal–Organic frameworks as efficient single-atom electrocatalysts for N2 reduction: A density functional theory study

Electrocatalytic nitrogen reduction reaction (NRR) is a sustainable and eco-friendly process to generate ammonia (NH3). However, there are significant challenges including low catalytic performance, instability, and poor selectivity, which hinder its rapid development. Herein, a series of two-dimensional (2D) conductive metal-organic frameworks (i.e., TM3(HHTT)2, TM = Sc, Ti, V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu and Zn) are investigated as single-atom catalysts (SACs) for NRR process by the density functional theory (DFT). The obtained results of Gibbs free energies of adsorption for N2, ∗NNH, ∗NH3, which are commonly used as activity descriptors to screen the effectiveness of catalysts, show that the Mo3(HHTT)2 monolayer (among all the TM3(HHTT)2 ones) can activate NN bonds, stabilize the adsorbed ∗NNH, and achieve the desorption of NH3. The Mo3(HHTT)2 monolayer also exhibits an excellent structural stability (with values of Ef = −2.96 eV and Udiss = 1.28 V). N2 can be effectively reduced into NH3 on the Mo3(HHTT)2 monolayer with a low limiting potential of −0.60 V along the distal pathway. Furthermore, the σ-donation and π∗ back-donation of N2 adsorbed onto the Mo3(HHTT)2 monolayer indicates an excellent electrical conductivity of Mo3(HHTT)2, which is beneficial for the effective electron transfer during the NRR process. Furthermore, the Mo3(HHTT)2 monolayer exhibits considerable selectivity for the NRR process over the hydrogen evolution reaction. Our study proved that this 2D c-MOFs carrying TM of the Mo3(HHTT)2 monolayer can be used as a promising catalyst for nitrogen fixation.

Direct Construction of 2D Conductive Metal-Organic Frameworks from a Nonplanar Ligand: In Situ Scholl Reaction and Topological Modulation.

Two-dimensional conductive metal-organic frameworks (2D c-MOFs) are an emerging class of promising porous materials with high crystallinity, tunable structures, and diverse functions. However, the limited topologies and difficulties in synthesizing suitable organic linkers remain a great challenge for 2D c-MOFs synthesis and applications. Herein, two layered 2D c-MOF polymorphs with either a rhombus structure (sql-TBA-MOF) or kagome structure (kgm-TBA-MOF) were directly constructed via in situ Scholl reaction and coordination chemistry from a flexible and nonplanar tetraphenylbenzene-based ligand (8OH-TPB) in a one-pot manner. Interestingly, the kgm-TBA-MOF comprising hexagonal and triangular dual pores exhibit higher conductivities of 1.65 × 10-3 S/cm at 298 K and 3.33 × 10-2 S/cm at 353 K than that of sql-TBA-MOF (4.48 × 10-4 and 2.90 × 10-3 S/cm, respectively). Moreover, the morphology and topology can be modulated via the addition of ammonium hydroxide as modulator. The present work provides a new pathway for design, synthesis, and topological regulation of 2D c-MOFs.

Defect Engineering To Tailor Metal Vacancies in 2D Conductive Metal-Organic Frameworks: An Example in Electrochemical Sensing.

Two-dimensional conductive metal-organic frameworks (2D conductive MOFs) with π-d conjugations exhibit high electrical conductivity and diverse coordination structures, making them constitute a desirable platform for new electronic devices. Defects are inevitable in the self-assembly process of 2D conductive MOFs. Arguably, defect engineering that deliberately manipulates defects demonstrates great potential to enhance the electrocatalytic activity of this family of novel materials. Herein, a facile and universal defect engineering strategy is proposed and demonstrated for metal vacancy regulation of metal benzenehexathiolato (BHT) coordination polymer films. Controllable metal vacancies can be produced by simply tuning the proton concentration during the confined self-assembly process at the liquid-liquid interface. This facile but universal defect design strategy has been proven to be effective in a class of materials including Cu-BHT, Ni-BHT, and Ag-BHT for physicochemical regulation. To further demonstrate the feasibility and practicality in electrochemical applications, the elaborately fabricated Cu-BHT films with abundant Cu vacancies deliver competitive performance in electrocatalytic sensing of H2O2. Mechanistic analysis revealed that the Cu vacancies act as effective active sites for adsorption and reduction of H2O2, and the tuned electronic structure boosts the electrocatalytic reaction. The developed advanced sensing platform confirms the excellent commercial potential of Cu-BHT sensors for H2O2. The findings provide insights into the molecular structure design of 2D conducting MOFs by defect engineering and demonstrate the commercial potential of Cu-BHT electrochemical sensors.

Electrochemical Sensor Based on Au NPs@NiPc-Cu MOFs Modified Electrode for the Rapid Detection of Luteolin

In this study, a novel electrochemical sensor was designed to detect luteolin (Lu) with the composite of gold nanoparticles and nickel phthalocyanine-based 2D conductive metal-organic frameworks (Au NPs@NiPc-Cu MOFs) for the first time. The NiPc-Cu MOFs exhibit excellent conductivity, large specific surface area, and porous structure, which can accelerate the mass transfer process of target molecules. To further improve the sensitivity of the sensing platform, Au NPs with outstanding conductivity were introduced to the surface of NiPc-Cu MOFs to prepare Au NPs@NiPc-Cu MOFs. The synergistic effect of NiPc-Cu MOFs and Au NPs endows the sensor with excellent electrocatalytic performance and outstanding sensitivity. Under optimal conditions, the electrochemical sensor has a wide linear range (0.1–40 μM). Moreover, the prepared sensor possesses good stability and anti-interference ability. This method does not require complicated sample pretreatment, simple operation, and short detection time, which can provide a new method for the rapid detection of Lu.

Conjugated Metal-Organic Macrocycles: Synthesis, Characterization, and Electrical Conductivity.

The dimensional reduction of solids into smaller fragments provides a route to achieve new physical properties and gain deeper insight into the extended parent structures. Here, we report the synthesis of CuTOTP-OR (TOTPn- = 2,3,6,7-tetraoxidotriphenylene), a family of copper-based macrocycles that resemble truncated fragments of the conductive two-dimensional (2D) metal-organic framework Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene). The planar metal-organic macrocycles self-assemble into ordered nanotubes with internal diameters of ∼2 nm and short interlayer distances of ∼3.20 Å. Strong π-π stacking interactions between macrocycles facilitate out-of-plane charge transport, and pressed pellet conductivities as high as 2(1) × 10-3 S cm-1 are observed. Peripheral alkyl functionalization enhances solution processability and enables the fabrication of thin-film field-effect transistor devices. Ambipolar charge transport is observed, suggesting that similar behavior may be operative in Cu3(HHTP)2. By coupling the attractive features of metal-organic frameworks with greater processability, these macrocycles enable facile device integration and a more nuanced understanding of out-of-plane charge transport in 2D conductive metal-organic frameworks.

Boosting photocatalytic hydrogen evolution of covalent organic frameworks by introducing 2D conductive metal–organic frameworks as noble metal-free co-catalysts

A conductive MOF Cu3(HHTP)2 is introduced as a non-noble metal co-catalyst into a Tp-Pa-2-COF to construct an efficient hydrogen evolution system.

Bimetallic Two‐Dimensional Metal–Organic Frameworks for the Chemiresistive Detection of Carbon Monoxide

AbstractThis paper describes the demonstration of a series of heterobimetallic, isoreticular 2D conductive metal–organic frameworks (MOFs) with metallophthalocyanine (MPc, M=Co and Ni) units interconnected by Cu nodes towards low‐power chemiresistive sensing of ppm levels of carbon monoxide (CO). Devices achieve a sub‐part‐per‐million (ppm) limit of detection (LOD) of 0.53 ppm toward CO at a low driving voltage of 0.1 V. MPc‐based Cu‐linked MOFs can continuously detect CO at 50 ppm, the permissible exposure limit required by the Occupational Safety and Health Administration (OSHA), for multiple exposures, and realize CO detection in air and in humid environment. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), density functional theory (DFT) calculations, and comparison experiments suggest the contribution of Cu nodes to CO binding and the essential role of MPc units in tuning and amplifying the sensing response.

Bimetallic Two-Dimensional Metal-Organic Frameworks for the Chemiresistive Detection of Carbon Monoxide.

This paper describes the demonstration of a series of heterobimetallic, isoreticular 2D conductive metal-organic frameworks (MOFs) with metallophthalocyanine (MPc, M=Co and Ni) units interconnected by Cu nodes towards low-power chemiresistive sensing of ppm levels of carbon monoxide (CO). Devices achieve a sub-part-per-million (ppm) limit of detection (LOD) of 0.53 ppm toward CO at a low driving voltage of 0.1 V. MPc-based Cu-linked MOFs can continuously detect CO at 50 ppm, the permissible exposure limit required by the Occupational Safety and Health Administration (OSHA), for multiple exposures, and realize CO detection in air and in humid environment. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), density functional theory (DFT) calculations, and comparison experiments suggest the contribution of Cu nodes to CO binding and the essential role of MPc units in tuning and amplifying the sensing response.

Efficiently Regulating the Electrical Properties of Flexible Fabric‐Based Cu3(BTC)2 Thin Film by Introducing Various Guest Molecules

AbstractRecently, the flexibility of 2D conductive metal–organic frameworks (MOFs) is an important precondition for manufacturing high‐performance smart electronic devices. Preparation of MOFs thin film has drawn much attention, and increasingly more MOF thin films have been deposited on different rigid substrates like glass, silicon, and metal electrodes. However, they do not meet the requirements for flexible materials, such as wearable electronic devices. Here, the fabric‐based composites (the integration of MOFs and fabric materials) can solve this problem. Insulating polyester fabric is chosen as a flexible substrate and atom layer deposition (ALD) and the layer‐by‐layer (LBL) method (also called the liquid phase epitaxy method) are combined to synthesize Cu3(BTC)2 thin film. 7,7,8,8‐tetracyanoquinodimethane (TCNQ) and polypyrrole (PPy) are chosen to improve the conductivity of the MOF thin films. The conductivity of Cu3(BTC)2 thin film is improved by more than four orders of magnitude compared to that of the original sample. This research shows that the large‐area lightweight fabric‐based Cu3(BTC)2 thin films, which possess excellent uniformity and flexibility and controllable thickness, can be prepared at room temperature; this allows MOFs to be applied in more areas, such as large‐area electronic devices and smart wearable sensing equipment.

Redox Ladder of Ni3 Complexes with Closed-Shell, Mono-, and Diradical Triphenylene Units: Molecular Models for Conductive 2D MOFs.

We report the isolation and characterization of a series of trinickel complexes with 2,3,6,7,10,11-hexaoxytriphenylene (HOTP), [(Me3 TPANi)3 (HOTP)](BF4 )n (Me3 TPA=N,N,N-tris[(6-methyl-2-pyridyl)methyl]amine) (n=2, 3, 4 for complexes 1, 2, 3). These complexes comprise a redox ladder whereby the HOTP core displays increasingly quinoidal character as its formal oxidation state changes from -4, to -3, and -2 in 1, 2, and 3, respectively. No formal oxidation state changes occur on Ni, allowing the isolation of singlet diradical, monoradical, and closed-shell configurations for HOTP in 1, 2, and 3, respectively, with a concomitant decrease in the spin coupling strength upon oxidation. Because the three complexes can be considered models of the smallest building blocks of 2D conductive metal-organic frameworks such as Ni9 HOTP4 , these results serve as possible inspiration for the construction of extended materials with targeted electric and magnetic properties.

Enhanced Capacitance Performance by Coupling 2D Conductive Metal–Organic Frameworks and Conducting Polymers for Hybrid Supercapacitors

Enhanced Capacitance Performance by Coupling 2D Conductive Metal–Organic Frameworks and Conducting Polymers for Hybrid Supercapacitors

Tricycloquinazoline‐Based 2D Conductive Metal–Organic Frameworks as Promising Electrocatalysts for CO2Reduction

Abstract2D conductive metal–organic frameworks (2D c‐MOFs) are promising candidates for efficient electrocatalysts for the CO2reduction reaction (CO2RR). A nitrogen‐rich tricycloquinazoline (TQ) based multitopic catechol ligand was used to coordinate with transition‐metal ions (Cu2+and Ni2+), which formed 2D graphene‐like porous sheets: M3(HHTQ)2(M=Cu, Ni; HHTQ=2,3,7,8,12,13‐Hexahydroxytricycloquinazoline). M3(HHTQ)2can be regarded as a single‐atom catalyst where Cu or Ni centers are uniformly distributed in the hexagonal lattices. Cu3(HHTQ)2exhibited superior catalytic activity towards CO2RR in which CH3OH is the sole product. The Faradic efficiency of CH3OH reached up to 53.6 % at a small over‐potential of −0.4 V. Cu3(HHTQ)2exhibited larger CO2adsorption energies and higher activities over the isostructural Ni3(HHTQ)2and the reported archetypical Cu3(HHTP)2. There is a strong dependence of both metal centers and the N‐rich ligands on the electrocatalytic performance.

Tricycloquinazoline-Based 2D Conductive Metal-Organic Frameworks as Promising Electrocatalysts for CO2 Reduction.

2D conductive metal-organic frameworks (2D c-MOFs) are promising candidates for efficient electrocatalysts for the CO2 reduction reaction (CO2 RR). A nitrogen-rich tricycloquinazoline (TQ) based multitopic catechol ligand was used to coordinate with transition-metal ions (Cu2+ and Ni2+ ), which formed 2D graphene-like porous sheets: M3 (HHTQ)2 (M=Cu, Ni; HHTQ=2,3,7,8,12,13-Hexahydroxytricycloquinazoline). M3 (HHTQ)2 can be regarded as a single-atom catalyst where Cu or Ni centers are uniformly distributed in the hexagonal lattices. Cu3 (HHTQ)2 exhibited superior catalytic activity towards CO2 RR in which CH3 OH is the sole product. The Faradic efficiency of CH3 OH reached up to 53.6 % at a small over-potential of -0.4 V. Cu3 (HHTQ)2 exhibited larger CO2 adsorption energies and higher activities over the isostructural Ni3 (HHTQ)2 and the reported archetypical Cu3 (HHTP)2 . There is a strong dependence of both metal centers and the N-rich ligands on the electrocatalytic performance.