A Conductive 2D Conjugated Tetrathia[8]circulene-Based Nickel Metal–Organic Framework for Energy Storage

Herein, a novel D₄ symmetrical redox-active ligand tetrathia[8]circulene-2,3,5,6,8,9,11,12-octaol (8OH-TTC) is designed and synthesized, which coordinates with Ni²⁺ ions to construct a 2D conductive metal-organic framework (2D c-MOF) named Ni-TTC. Ni-TTC exhibits typical semiconducting properties with electrical conductivity up to ≈1.0 S m⁻¹ at 298 K. Furthermore, magnetism measurements show the paramagnetic property of Ni-TTC with strong antiferromagnetic coupling due to the presence of semiquinone ligand radicals and Ni²⁺ sites. In virtue of its decent electrical conductivity and good redox activity, the gravimetric capacitance of Ni-TTC is up to 249 F g⁻¹ at a discharge rate of 0.2 A g⁻¹, which demonstrates the potential of tetrathia[8]circulene-based redox-active 2D c-MOFs in energy storage applications.     

Manifestation of Strongly Correlated Electrons in a 2D Kagome Metal–Organic Framework

2D and layered electronic materials characterized by a kagome lattice, whose valence band structure includes two Dirac bands and one flat band, can host a wide range of tunable topological and strongly correlated electronic phases. While strong electron correlations have been observed in inorganic kagome crystals, they remain elusive in organic systems, which benefit from versatile synthesis protocols via molecular self-assembly and metal-ligand coordination. Here, direct experimental evidence of local magnetic moments resulting from strong electron–electron Coulomb interactions in a 2D metal–organic framework (MOF) is reported. The latter consists of di-cyano-anthracene (DCA) molecules arranged in a kagome structure via coordination with copper (Cu) atoms on a silver surface [Ag(111)]. Temperature-dependent scanning tunneling spectroscopy reveals magnetic moments spatially confined to DCA and Cu sites of the MOF, and Kondo screened by the Ag(111) conduction electrons. By density functional theory and mean-field Hubbard modeling, it is shown that these magnetic moments are the direct consequence of strong Coulomb interactions between electrons within the kagome MOF. The findings pave the way for nanoelectronics and spintronics technologies based on controllable correlated electron phases in 2D organic materials.     

Novel Metal–Organic Framework Cocrystal Strategy for Significantly Enhancing Photocatalytic Performance

Owing to their high carrier recombination speed and low spectral utilization, it is difficult to further improve the performance of photocatalysts. In this study, a novel metal–organic framework (MOF) self-assembled cocrystal material is developed. The guest molecule is inserted and self-assembled with the existing MOF ligand to form an organic cocrystal. The highly ordered molecular arrangement and tight intermolecular distances between donor and acceptor molecules promote a strong π–π charge transfer interaction, facilitating the migration and separation of photogenerated charge carriers. In addition, efficient redshifts in the absorption wavelength enhance the response to visible light. Further, the unique porous structure of MOFs is beneficial for increasing the interfacial area of photocatalytic reactions, and metal ions can become the center of photogenerated carrier capture, effectively inhibiting carrier recombination. Consequently, the MOF cocrystal demonstrates remarkable efficiency in the degradation of pollutants in water, achieving a noteworthy removal efficiency of 95.31% within 15 min. Moreover, the photocatalyic reaction kinetics constant of the MOF cocrystal is 46.5 times higher, indicating the success of this new strategy in developing highly efficient photocatalytic systems.     

Asymmetric Polymer Electrolyte Constructed by Metal–Organic Framework for Solid-State,Dendrite-Free Lithium Metal Battery

Solid-state polymer electrolytes (SPEs) with flexibility, easy processability, and low cost have been regarded as promising alternatives for conventional liquid electrolytes in next-generation high-safety lithium metal batteries. However, SPEs generally suffer poor strength to block Li dendrite growth during the charge/discharge process, which severely limits their wide practical applications. Here, a rational design of 3D cross-linked network asymmetric SPE modified with a metal–organic framework (MOF) layer on one side is proposed and prepared through an in-situ polymerization process. In such unique asymmetric SPEs, the nanoscale MOF layer acts as a shield that effectively suppresses the growth of Li dendrites and regulates the uniform Li⁺ transport, and the polymer electrolyte can be scattered in the whole cell to endow the smooth transmission of Li⁺. As a result, the asymmetric SPE exhibits high ionic conductivity, wide electrochemical window, high thermal stability and safety, which endows the Li/Li symmetrical cell with outstanding cyclic stability (operate well over 800 h at a current density of 0.1 mA cm⁻² for the capacity of 0.1 mAh cm⁻²).     

Synergistic Effect of Crosslinked Organic–Inorganic Composite Protective Layer for High Performance Lithium Metal Batteries

Maintaining a stable interface of lithium metal anodes (LMAs) by implementing a protective layer is a promising approach in extending the cycle life of lithium metal batteries (LMBs). Nevertheless, designing a protective layer with desired physicochemical properties is still a challenging task. Herein, an inorganic–organic composite protective layer consisting of fluorinated graphene oxide (FGO) (inorganic part) and polyacrylic acid (PAA) (organic part) that are in situ crosslinked via poly(ethylene glycol) diglycidyl ether (PEGDE) into a robust network is reported. The mechanical strength of FGO and the elasticity of the polymeric network jointly suppress the unwanted dendritic Li growth while fluorine-functional groups in FGO induce an LiF-enriched interface. This balanced inorganic–organic composite protective layer facilitates charge transfer kinetics for enhanced lithium-ion diffusion at the interface. Utilizing this protective layer, LMB full-cells with LiFePO₄ demonstrate negligible capacity loss for 100 cycles even under an extreme negative/positive capacity (N/P) ratio of 1.0. This study uncovers the possibility of highly robust, reliable LMBs by a sophisticatedly designed protective layer of widely used inorganic and organic components.     

Giant Magnetoresistance in a Metal–Organic Semiconductor–Metal Structure

Semiconductors - The article presents the results of investigation of the giant magnetoresistance effect in a magnetic metal–organic semiconductor–non-magnetic metal structure with a...     

Implanting of Single Zinc Sites into 2D Metal–Organic Framework Nanozymes for Boosted Antibiofilm Therapy

Design of nanozymes with catalytic active sites at atomic-scale not only improves the atomic utilization, but also provides a well-defined coordination structure for nanozymes’ catalytic mechanism research. Herein, a surfactant-assisted method is reported for preparing 2D metal–organic frameworks based single zinc sites nanozyme (SZN-MOFs) through assembling preformed Zn single-atom coordinated porphyrin precursors into ultrathin MOF nanosheets. The Zn atom loading weight ratio in SZN-MOFs is up to 4.6 wt.%. The SZN-MOFs exhibit extraordinary peroxidase-like activity, which can effectively catalyze H₂O₂ into hydroxyl radicals. The catalytical mechanism is elucidated and the origin of the high peroxidase-like activity of SZN-MOFs is rationalized using density functional theory calculations. Finally, it is demonstrated that the SZN-MOFs present great promises for in vitro and in vivo antibiofilm activity under a low concentration of H₂O₂. This study not only develops a surfactant-assisted method for fabricating MOF-based single sites nanozyme, but also manifests the applications in the field of antibiofilm therapy.     

Diverse Metal–Organic Framework Architectures for Electromagnetic Absorbers and Shielding

Metal–organic frameworks (MOFs) and their derivatives, featuring unique 3D microstructures and enhanced electromagnetic properties, are illuminating infinite possibilities for electromagnetic functional materials and devices, receiving significant attention from domestic and foreign researchers. Herein, the design strategy of the MOF monomer is investigated, and the electromagnetic response mechanism is systematically analyzed. Research is emphatically introduced regarding MOF-based materials in microwave absorption and electromagnetic interference shielding. Finally, a clear insight on the quickly growing field is given, and the current challenges and future research directions are summarized and predicted.     

A 3D Cu-Naphthalene-Phosphonate Metal–Organic Framework with Ultra-High Electrical Conductivity

A conductive phosphonate metal–organic framework (MOF), [{Cu(H₂O)}(2,6-NDPA)_0.5] (NDPA = naphthalenediphosphonic acid), which contains a 2D inorganic building unit (IBU) comprised of a continuous edge-sharing sheet of copper phosphonate polyhedra is reported. The 2D IBUs are connected to each other via polyaromatic 2,6-NDPA's, forming a 3D pillared-layered MOF structure. This MOF, known as TUB40, has a narrow band gap of 1.42 eV, a record high average electrical conductance of 2 × 10² S m⁻¹ at room temperature based on single-crystal conductivity measurements, and an electrical conductance of 142 S m⁻¹ based on a pellet measurement. Density functional theory (DFT) calculations reveal that the conductivity is due to an excitation from the highest occupied molecular orbital on the naphthalene-building unit to the lowest unoccupied molecular orbital on the copper atoms. Temperature-dependent magnetization measurements show that the copper atoms are antiferromagnetically coupled at very low temperatures, which is also confirmed by the DFT calculations. Due to its high conductance and thermal/chemical stability, TUB40 may prove useful as an electrode material in supercapacitors.     

In Situ Fabrication of Metal–Organic Framework Thin Films with Enhanced Pervaporation Performance

The intrinsic porosity in the periodic structures of metal–organic frameworks (MOFs) endows them with a great potential for membrane separation. However, facile fabrication of crystalline MOF membranes has been challenging and limited to few materials for economic and environmental considerations. Herein, a continuous Zr-MOF thin film with a thickness of ≈180 nm has been fabricated via in situ recrystallization of MOF nanoparticles on the porous support under formic acid vapor. Owing to the inherent microporosity and the well-established hydrophilicity during membrane fabrication, the MOF thin films exhibit excellent pervaporation performance with separation factors of 2630, 501 and fluxes of 1.45, 1.41 kg m⁻² h⁻¹) for n-butanol dehydration and methanol/methyl tert-butyl ether (MeOH/MTBE) separation, respectively. The structural stability of the film has been further confirmed by its steady performance in the 10-day pervaporation test. This in situ recrystallization method induced by a trace amount of acid vapor with no extra ingredients opens a new avenue for the facile membrane fabrication of various MOF materials to feasibly realize their versatile potential as membrane materials.     

Lithium Extraction by Emerging Metal–Organic Framework-Based Membranes

Lithium is mainly extracted from brine and ores; however, current lithium mining methods require large amounts of chemicals, discharge many wastes, and can have serious environmental repercussions. Metal–organic framework (MOF)-based membranes have shown great potential in lithium extraction due to their uniform pore sizes, high porosities, and rich host–guest chemistry compared to other materials. In this review, the processes and disadvantages of current lithium extraction technologies are introduced. The structure features and corresponding design strategy of MOFs suitable for Li⁺ ion separations are presented. Following, recent advances of polycrystalline MOF membranes, mixed matrix membranes, and MOF channel membranes for lithium-ion separation are discussed in detail. Finally, opportunities for future developments and challenges in this emerging research field are presented.     

Self-Assembled Nanoporous Metal–Organic Framework Monolayer Film for Osmotic Energy Harvesting

Osmotic energy represents a promising energy resource because it is sustainable and environmentally benign. Subnanoscale channels are considered as a competitive platform for generating this blue energy due to their highly selective and ultrafast ion transport. However, fabricating functional subnanochannels capable of high energy output remains challenging. Here, a heterogeneous subnanochannel membrane formed by coating a functionalized self-assembled metal−organic framework (MOF) monolayer (SAMM) film on a porous anodic aluminum oxide membrane, is reported. The SAMM film, with a thickness of ≈160 nm, is fabricated by self-assembly of poly(methyl methacrylate-co-vinylimidazole)-modified UiO-66-NH₂ nanoparticles at the water−air interface. In the SAMM, imidazole and NH₂ groups provide abundant positive charges, while the angstrom-scale windows act as ionic filters for selective screening of anions with different hydration diameters. As a result, the heterogeneous membrane exhibits excellent capacity for anion-selective transport, which contributes to an optimal osmotic power of 6.76 W m⁻² under a 100-fold NaCl gradient, as well as a high Cl⁻/SO₄²⁻ selectivity of ≈42.2. Further, the output power is increased to 10.5 W m⁻² by methylating imidazole moieties on the MOF surface. This work provides a facile and modular approach to fabricate subnanochannels for enabling highly selective and efficient osmotic energy conversion.     

Photocatalytic Valorization of Plastic Waste over Zinc Oxide Encapsulated in a Metal–Organic Framework

The conversion of waste plastic into high-value-added chemicals is regarded as a promising approach for relieving global plastic pollution and contributing to the circular economy. Herein, a partial calcination strategy is developed to fabricate a zinc oxide/UiO66-NH₂ (ZnO/UiO66-NH₂) heterojunction, in which ZnO is encapsulated in porous UiO66-NH₂ for the photocatalytic valorization of plastic. This strategy preserves the framework structure of UiO66-NH₂, thus enabling the formation of ZnO with ultra-small size distributed inside the skeleton. The synergistic effect of the obtained ZnO/UiO66-NH₂ heterojunction facilitates providing an efficient channel for carrier/mass transfer and guarantees structural stability. As a result, ZnO/UiO66-NH₂ exhibits high activity for converting polylactic acid (PLA) and polyvinyl chloride (PVC) into acetic acid, coupled with H₂ production. This work provides a feasible strategy for rationally designing heterojunction photocatalysts, as well as an insight into understanding the process of photocatalytic valorization of plastic.     

Laser-Induced Annealing of Metal–Organic Frameworks on Conductive Substrates for Electrochemical Water Splitting

The conventional thermal transformation of metal–organic frameworks (MOFs) for electrocatalysis requires high temperature, an inert atmosphere, and long duration that result in severe aggregation of metal particles and non-uniform porous structures. Herein, a precise and inexpensive laser-induced annealing (LIA) strategy, which eliminates particle aggregation and rapidly generates uniform structures with a high exposure of active sites, is introduced to carbonize MOFs on conductive substrates under ambient conditions within a few minutes. By systematically considering 8 substrates and 12 MOFs, a series of LIA-MOF/substrate devices with controllable sizes and good flexibility are successfully obtained. These LIA-MOF/substrate devices can directly serve as working electrodes. Remarkably, LIA-MIL-101(Fe) on nickel foam exhibits an ultralow overpotential of 225 mV at a current density of 50 mA cm⁻² and excellent stability over 50 h for facilitating the oxygen evolution reaction, outperforming most recently reported transition-metal-based electrocatalysts and commercial RuO₂. Physical characterizations and theoretical calculations evidence that the high activity of LIA-MIL-101(Fe) arises from the favorable adsorption of intermediates at its Ni-doped Fe₃O₄ overlayer that is formed during the laser treatment. Moreover, the LIA-MOF/substrate devices are assembled for overall water splitting. The proposed LIA strategy demonstrates a cost-effective route for manufacturing scalable energy storage and conversion devices.     

Bimetal Organic Framework–Ti3C2Tx MXene with Metalloporphyrin Electrocatalyst for Lithium–Oxygen Batteries

The gravest oxidation of MXenes has become a critical problem due to the formation of metal oxides, leading to the loss of their intrinsic properties. Herein, bimetallic cobalt–manganese organic framework (CMT) directly grown on a Ti₃C₂T_x MXene sheet via solvothermal treatment to obtain strong oxidation resistance in an open structured application and to enhance electrocatalytic properties for oxygen evolution and reduction reaction is reported. Inspired by ligand chemistry, the carboxyl acids in tetrakis(4–carboxyphenyl)porphyrin acting as an organic linker are grafted with the surface terminators of Ti₃C₂T_x MXene through the Fischer esterification and substitution reaction of fluorine, thereby greatly enhancing the antioxidation stability. Furthermore, the as-formed metalloporphyrin structure and unpaired electrons, produced between CMT and Ti₃C₂T_x MXene during solvothermal treatment, improve their electrocatalytic activity, durability, and electrical conductivity through an electron hopping mechanism. Consequently, the CMT@MXene demonstrates high stability as a bifunctional electrocatalyst at a fixed specific capacity of 1000 mAh g⁻¹ and a current density of 500 mA g⁻¹ for 247 cycles in lithium–oxygen (Li O₂) battery. This approach suggests new strategies for the synergistic coupling of MXenes and MOFs for future open structured applications.     

Chromium-Based Metal–Organic Framework as A-Site Cation in CsPbI2Br Perovskite Solar Cells

Inorganic CsPbI_xBr_3−x perovskite solar cells (PSCs) have gained enormous interest due to their excellent thermal stabilities. However, their intrinsically poor moisture stability hampers their further development. Herein, a chromium-based metal–organic framework group is intercalated inside the inorganic Pb I framework, resulting in a new multiple-dimensional electronically coupled CsPbI₂Br perovskite. In this structurally and electronically coupled perovskite, the π-conjugated terpyridyl can delocalize the excited valence electrons of metal Cr³⁺ ion, enabling multi-interactive charge-carrier transport channels within CsPbI₂Br perovskites. The stability and efficiency of the produced devices are substantially enhanced in comparison to their counterparts with only a pristine CsPbI₂Br active layer. The optimized all-inorganic PSC yields a power conversion efficiency (PCE) as high as 17.02%. Remarkably, the stabilized device retains 80% of its PCE after 1000 h in the ambient atmosphere. This study provides a new paradigm toward addressing the stability challenge of the inorganic perovskite while enhancing its carrier transport ability.     

Electrically Conductive Metal–Organic Framework Thin Film-Based On-Chip Micro-Biosensor: A Platform to Unravel Surface Morphology-Dependent Biosensing

Electrically conductive metal–organic frameworks (EC-MOFs) are suitable for electrochemical sensing because of their unique structure and properties. Herein, an on-chip electrochemical micro-biosensor is designed to study the electrocatalytic interfaces, which are generally buried between the solid support and liquid electrolyte in conventional electrochemical sensing methods. The gas–liquid interfacial reaction method is used to obtain a Cu-benzenehexathiol (Cu-BHT) thin film with a flat up-side surface and synaptic-like structure on the bottom-side surface. The effect of surface morphology on the film sensing performance is studied using the prepared Cu-BHT film-based on-chip micro-biosensor. The bottom-side surface exhibited significantly higher H₂O₂ sensing performance than that of the smooth up-side surface. The synaptic-like structure has dense crystal defects (ts-Cu), which act as nanozymes and play an important role in improving the H₂O₂ sensing performance. This study clarifies the role of crystal defects in Cu-BHT sensing using the micro-biosensor and allows the in-situ study of electrochemical interface of EC-MOF films during biosensing.     

Vanadium Oxide Intercalated with Conductive Metal–Organic Frameworks with Dual Energy-Storage Mechanism for High Capacity and High-Rate Capability Zn Ion Storage

Vanadium oxides (VO_x) feature the potential for high-capacity Zn²⁺ storage, which are often preintercalated with inert ions or lattice water for accelerating Zn²⁺ migration kinetics. The inertness of these preintercalated species for Zn²⁺ storage and their incapability for conducting electrons, however, compromise the capacity and rate capability of VO_x. Herein, Ni-BTA, a 1D conductive metal–organic framework (c-MOF), is intercalated into the interlayer space of VO_x by coordinating organic ligands with preinserted Ni²⁺. The intercalated Ni-BTA improves the conductivity of VO_x by π–d conjugation, facilitates Zn²⁺ migration by enlarging its interlayer spacing, and stabilizes the crystal structure of VO_x as interlayer pillars, thus simultaneously enhancing the material's rate capability and cycling stability. Meanwhile, a dual reaction mechanism of Zn²⁺ storage, i.e., the redox of V⁵⁺/V³⁺ in VO_x and the rearrangement of chemical bonds (CN/C N) in Ni-BTA, collaboratively contributes to an enhanced capacity. Consequently, this Ni-BTA-intercalated VO_x material exhibits a high Zn²⁺ storage capacity of 464.2 mAh g⁻¹ at 0.2 A g⁻¹ and an excellent rate capability of 272.5 mAh g⁻¹ at 5 A g⁻¹. This work provides a general strategy for integrating c-MOFs with inorganic cathode materials to achieve high-capacity and high-rate performance.     

Metal–Organic Framework Nanosheets: Programmable 2D Materials for Catalysis,Sensing, Electronics,and Separation Applications

Metal–organic framework nanosheets (MONs) have recently emerged as a distinct class of 2D materials with programmable structures that make them useful in diverse applications. In this review, the breadth of applications that have so far been investigated are surveyed, thanks to the distinct combination of properties afforded by MONs. How: 1) The high surface areas and readily accessible active sites of MONs mean they have been exploited for a variety of heterogeneous, photo-, and electro-catalytic applications; 2) their diverse surface chemistry and wide range of optical and electronic responses have been harnessed for the sensing of small molecules, biological molecules, and ions; 3) MONs tunable optoelectronic properties and nanoscopic dimensions have enabled them to be harnessed in light harvesting and emission, energy storage, and other electronic devices; 4) the anisotropic structure and porous nature of MONs mean they have shown great promise in a variety of gas separation and water purification applications; are discussed. The aim is to draw links between the uses of MONs in these different applications in order to highlight the common opportunities and challenges presented by this promising class of nanomaterials.     

Highly CO2 Selective Metal–Organic Framework Membranes with Favorable Coulombic Effect

The topology and chemical functionality of metal–organic frameworks (MOFs) make them promising candidates for membrane gas separation; however, few meet the criteria for industrial applications, that is, selectivity of >30 for CO₂/CH₄ and CO₂/N₂. This paper reports on a dense CAU-10-H MOF membrane that is exceptionally CO₂-selective (ideal selectivity of 42 for CO₂/N₂ and 95 for CO₂/CH₄). The proposed membrane also achieves the highest CO₂ permeability (approximately 500 Barrer) among existing pure MOF membranes with CO₂/CH₄ selectivity exceeding 30. State-of-the-art atomistic simulations provide valuable insights into the outstanding separation performance of CAU-10-H at the molecular level. Adsorbent–adsorbate Coulombic interactions are identified as a crucial factor in the design of CO₂-selective MOF membranes.