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1. Dominant Role of Hole Transport Pathway in Achieving Record High Photoconductivity in Two‐Dimensional Metal–Organic Frameworks

   https://doi.org/10.1002/anie.202309505  

   Wang, Denan; Ostresh, Sarah; Streater, Daniel; He, Peilei; Nyakuchena, James; Ma, Qiushi; Zhang, Xiaoyi; Neu, Jens; Brudvig, Gary W; Huang, Jier (December 2023, Angewandte Chemie International Edition)

   Abstract Metal–organic frameworks (MOFs) with mobile charges have attracted significant attention due to their potential applications in photoelectric devices, chemical resistance sensors, and catalysis. However, fundamental understanding of the charge transport pathway within the framework and the key properties that determine the performance of conductive MOFs in photoelectric devices remain underexplored. Herein, we report the mechanisms of photoinduced charge transport and electron dynamics in the conductive 2D M−HHTP (M=Cu, Zn or Cu/Zn mixed; HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene) MOFs and their correlation with photoconductivity using the combination of time‐resolved terahertz spectroscopy, optical transient absorption spectroscopy, X‐ray transient absorption spectroscopy, and density functional theory (DFT) calculations. We identify the through‐space hole transport mechanism through the interlayer sheet π–π interaction, where photoinduced hole state resides in HHTP ligand and electronic state is localized at the metal center. Moreover, the photoconductivity of the Cu−HHTP MOF is found to be 65.5 S m⁻¹, which represents the record high photoconductivity for porous MOF materials based on catecholate ligands. 

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2. 2D Copper Tetrahydroxyquinone Conductive Metal–Organic Framework for Selective CO ₂ Electrocatalysis at Low Overpotentials

   https://doi.org/10.1002/adma.202004393  

   Majidi, Leily; Ahmadiparidari, Alireza; Shan, Nannan; Misal, Saurabh_N; Kumar, Khagesh; Huang, Zhehao; Rastegar, Sina; Hemmat, Zahra; Zou, Xiaodong; Zapol, Peter; et al (February 2021, Advanced Materials)

   Abstract Metal–organic frameworks (MOFs) are promising materials for electrocatalysis; however, lack of electrical conductivity in the majority of existing MOFs limits their effective utilization in the field. Herein, an excellent catalytic activity of a 2D copper (Cu)‐based conductive MOF, copper tetrahydroxyquinone (CuTHQ), is reported for aqueous CO₂reduction reaction (CO₂RR) at low overpotentials. It is revealed that CuTHQ nanoflakes (NFs) with an average lateral size of 140 nm exhibit a negligible overpotential of 16 mV for the activation of this reaction, a high current density of ≈173 mA cm⁻²at −0.45 V versus RHE, an average Faradaic efficiency (F.E.) of ≈91% toward CO production, and a remarkable turnover frequency as high as ≈20.82 s⁻¹. In the low overpotential range, the obtained CO formation current density is more than 35 and 25 times higher compared to state‐of‐the‐art MOF and MOF‐derived catalysts, respectively. The operando Cu K‐edge X‐ray absorption near edge spectroscopy and density functional theory calculations reveal the existence of reduced Cu (Cu⁺) during CO₂RR which reversibly returns to Cu²⁺after the reaction. The outstanding CO₂catalytic functionality of conductive MOFs (c‐MOFs) can open a way toward high‐energy‐density electrochemical systems. 

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3. Tuning the Structure–Property Relationships of Metallophthalocyanine-Based Two-Dimensional Conductive Metal–Organic Frameworks with Different Metal Linkages

   https://doi.org/10.1021/jacs.4c15272  

   Noh, Hyuk-Jun; Cline, Evan; Pennington, Doran L; Lin, Hao-Yu Greg; Hendon, Christopher H; Mirica, Katherine A (March 2025, Journal of the American Chemical Society)

   Metallophthalocyanine (MPc)-linked conductive two-dimensional (2D) metal−organic frameworks (MOFs) hold tremendous promise as modular 2D materials in sensing, catalysis, and energy-related applications due to their combinatory bimetallic system from the MPc core and bridging metal nodes, endowing them with high electrical conductivity and multifunctionality. Despite significant advances, there is a gap in fundamental understanding regarding the periodic effects of metal nodes on the structural properties of MP-linked 2D MOFs. Herein, we report a series of highly crystalline MOFs wherein copper phthalocyanine (CuPc) is linked with Ni, Cu, and Zn nodes (CuPc-O-M, M: Ni, Cu, Zn). The prepared CuPc-O-M MOFs exhibit p-type semiconducting properties with an exceptionally high range of electrical conductivity. Notably, the differences in the 3d orbital configurations of the Ni, Cu, and Zn nodes in CuPc-O-M MOFs lead to perturbations of the interlayer stacking patterns of the 2D framework materials, which ultimately affect material properties, such as semiconducting band gaps and charge transport within the framework. The Cu2+ (3d9) metal node within the eclipsed interlayer stacking of CuPc-O-Cu MOF demonstrates excellent charge transport, which results in the smallest band gap of 1.14 eV and the highest electrical conductivity of 9.3 S m−1, while the Zn2+ (3d10) metal node within CuPc-O-Zn results in a slightly inclined interlayer stacking, leading to the largest band gap of 1.27 eV and the lowest electrical conductivity of 2.9 S m−1. These findings form an important foundation in the strategic molecular design of this class of materials for multifaceted functionality that builds upon the electronic properties of these materials. 

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4. Simulating CO2 diffusivity in rigid and flexible Mg-MOF-74 with machine-learning force fields

   https://doi.org/10.1063/5.0190372  

   Zheng, Bowen; Gu, Grace_X; Santos, Carine_dos; Neumann_Barros_Ferreira, Rodrigo; Steiner, Mathias; Luan, Binquan (May 2024, APL Machine Learning)

   The flexibility of metal–organic frameworks (MOFs) affects their gas adsorption and diffusion properties. However, reliable force fields for simulating flexible MOFs are lacking. As a result, most atomistic simulations so far have been carried out assuming rigid MOFs, which inevitably overestimates the gas adsorption energy. Here, we show that this issue can be addressed by applying a machine-learning potential, trained on quantum chemistry data, to atomistic simulations. We find that inclusion of flexibility is particularly important for simulating CO2 chemisorption in MOFs with coordinatively unsaturated metal sites. Specifically, we demonstrate that the diffusion of CO2 in a flexible Mg-MOF-74 structure is about one order of magnitude faster than in a rigid one, challenging the rigid-MOF assumption in previous simulations. 

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5. Metal‐Organic‐Framework‐Based Electrochemical Nanosensor for Hydrogen Peroxide

   https://doi.org/10.1002/celc.202200373  

   Hesari, Mahdi; Jia, Rui; Mirkin, Michael_V (June 2022, ChemElectroChem)

   Abstract Electrochemical applications of metal organic frameworks (MOFs) are of considerable current interest. Due to the large surface area exposed to solution, MOFs are potentially useful electrode materials for sensing inner‐sphere analytes, such as reactive oxygen species. Herein, we electrodeposited copper benzene tricarboxylate MOF (HKUST‐1) into the cavity of an open carbon nanopipette (CNP) to produce a CNP‐MOF nanoelectrode. Unlike electronically conductive metal or carbon electrodes, the electrochemical response of CNP–MOFs relies on oxidation/reduction of Cu(I)/Cu(II) nodes in the porous nanostructure. Nevertheless, sigmoidal steady‐state voltammograms with a well‐defined plateau current have been recorded for simple redox mediators, for example, ferrocenemethanol. A linear calibration curve obtained for the hydrogen peroxide reduction suggests that CNP–MOFs can potentially be useful as nanosensors for peroxide. 

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