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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. Water as an Eco-friendly Liquid-Assisted Grinding Agent (ecoLAGent) to Expand the Metal–Organic Framework “Library” for Green Enzyme Encapsulation

   https://doi.org/10.1021/acsami.5c14214  

   Dipti, Tyeaba Tasnim; Hasan, Md Zahidul; Armstrong, Zoe; Quadir, Mohiuddin; Liu, Liu; Wan, Caixia; Baker, Gary A; Feng, Li; MacRae, Austin; Yang, Zhongyu (October 2025, ACS Applied Materials & Interfaces)

   Enzymes are advanced biocatalysts, while immobilizing enzymes on solid supports, particularly metal–organic frameworks (MOFs), enhances enzyme stability, reusability, and substrate selectivity. One-pot cocrystallization (CC) of enzymes in MOFs in the aqueous phase avoids enzyme size limitation and leaching; our recent CC MOF “library” offers a collection of metal–ligand combinations for customizable enzyme immobilization [ACS Appl. Mater. Interfaces 2022, 14, 46, 51619–51629]. However, CC generally suffers from low yield and stability. Mechanochemical or liquid-assisted grinding (LAG) synthesis overcomes this issue, yet most current approaches use metals, ligands, and enzymes in powder states with organic solvents, limiting eco-friendliness and enzyme compatibility. Water as an eco-friendly LAG synthesis agent (eco-LAGent) offers a greener medium to preserve protein folding states, hydration shells, and conformational flexibility, essential for activity. However, only one MOF has been reported to be synthesized this way. Due to the different metal–ligand contact mechanisms, MOFs by CC or eco-LAGent synthesis may not have the same crystal structures either, yet there is a lack of data to compare. Here, we expand the “library” of enzyme@MOF biocatalysts synthesized in an eco-LAGent, water, using abundant, low-toxicity metal ions and ligands, achieving improved thermal and pH stability and significantly enhanced enzyme@MOF yields while proving the high chance of scaling up and eventually industrial applications. Grinding also impacted the interface of metal–ligand contact─compared to aqueous-phase CC, eco-LAGent synthesis increased the crystallinity in 3 MOFs, generated new MOF structures in another 3, and improved the thermal and pH stability across most resultant enzyme@MOF cocrystals. This study generalizes the eco-LAGent synthesis to more MOFs and opens a new avenue to encapsulate enzymes in high-quality crystals with a customized selection of metal ions and ligands (according to enzymes and applications) under green and scalable conditions. 

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3. Rapid Exciton Transport and Structural Defects in Individual Porphyrinic Metal Organic Framework Microcrystals

   https://doi.org/10.1021/jacs.3c12275  

   Afrin, Sajia; Yang, Xiaozhou; Morris, Amanda J.; Grumstrup, Erik M. (February 2024, Journal of the American Chemical Society)

   To date, spectroscopic characterization of porphyrin-based metal organic frameworks (MOFs) has relied almost exclusively on ensemble techniques, which provide only structurally averaged insight into the functional properties of these promising photochemical platforms. This work employs time-resolved pump–probe microscopy to probe ultrafast dynamics in PCN-222 MOF single crystals. The simultaneous high spatial and temporal resolution of the technique enables the correlation of spectroscopic observables to both inter- and intracrystal structural heterogeneity. The pump–probe measurements show that significant differences in the excited state lifetime exist between individual PCN-222 crystals of an ensemble. On a single PCN-222 crystal, differences in excited state lifetime and photoluminescence quantum yield are found to correlate to microscale structural defects introduced at crystallization. Pump probe microscopy also enables the direct measurement of excited state transport. Imaging of exciton transport on individual MOF crystals reveals rapid, but subdiffusive exciton transport which slows on the 10s of ps time scale. Time-averaged exciton diffusion coefficients over the first 200 ps span a range of 0.27 to 1.0 cm2/s, indicating that excited states are rapidly transported through the porphyrin network of PCN-222 before being trapped. Together, these single-particle-resolved measurements provide important new insight into the role played by structural defects on the photochemical functionality of porphyrin-based MOFs. 

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4. A New Electrically Conducting Metal–Organic Framework Featuring U-Shaped cis-Dipyridyl Tetrathiafulvalene Ligands

   https://doi.org/10.3389/fchem.2021.726544  

   Gordillo, Monica A.; Benavides, Paola A.; Spalding, Kaybriana; Saha, Sourav (October 2021, Frontiers in Chemistry)

   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. 

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5. A comparison of microcrystal electron diffraction and X-ray powder diffraction for the structural analysis of metal–organic frameworks

   https://doi.org/10.1107/S1600576724012068  

   Biehler, Erik; Pagola, Silvina; Stam, Daniel; Merkelbach, Johannes; Jandl, Christian; Abdel-Fattah, Tarek M (April 2025, Journal of Applied Crystallography)

   This study successfully implemented microcrystal electron diffraction (microED) and X-ray powder diffraction (XRPD) for the crystal structure determination of a new phase, TAF-CNU-1, Ni(C8H4O4)·3H2O, solved by microED from single microcrystals in the powder and refined at the kinematic and dynamic electron diffraction theory levels. This nickel metal–organic framework (MOF), together with its cobalt and manganese analogues with formula M(C8H4O4)·2H2O with M = MnII or CoII, were synthesized in aqueous media as one-pot preparations from the corresponding hydrated metal chlorides and sodium terephthalate, as a promising ‘green’ synthetic route to moisture stable MOFs. The crystal structures of the two latter materials have been previously determined ab initio from X-ray powder diffraction. The advantages and disadvantages of both structural characterization techniques are briefly summarized. Additional solid-state property characterization was carried out using thermogravimetric analysis, scanning electron microscopy and Fourier transform infrared spectroscopy. 

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