Microscopic Mechanical Force-Driven Amorphization of Metal-Organic Frameworks

While metal-organic frameworks (MOFs) are renowned for their highly ordered crystalline structures, the amorphization of MOFs reveals new functional properties and creates opportunities for material innovation. In this study, we present a novel microscopic mechanical force-driven amorphization that occurs within a polycrystalline metal-azolate framework (MAF-5) membrane. We show that vapor flow during pervaporation across the membrane generates localized mechanical stresses that disrupt the ordered crystalline lattice. This mechanical amorphization is significantly influenced by the physical properties of the permeating organic solvents, underscoring the importance of solvent-framework interactions. Our findings unveil a previously unknown mechanical mechanism that drives MOF amorphization and provide essential insights into their mechanical tunability, facilitating the design of amorphous MOF membranes with customized properties for advanced applications.

Double-Walled Mesoporous Hydrogen-Bonded Organic Frameworks with High Methane Storage Capacity

The development of mesoporous hydrogen-bonded organic frameworks (HOFs) is critically important for various applications, yet it poses significant challenges. Herein, we present the synthesis and characterization of a robust mesoporous HOF, RP-H200, constructed through the orchestration of π-π stacking and hydrogen bonding interactions in a 2-fold interpenetrated framework. RP-H200 features a unique double-walled structure with a pore size of 3.6 nm, representing the largest pore size among reported HOFs to date. The framework exhibits a high surface area of 2313 m2 g-1, with aromatic surfaces dominating the mesoporous channels. The methane storage performance of RP-H200 reaches a high capacity of 0.31 g g-1 at 270 K/100 bar and 0.25 g g-1 at 296 K/100 bar. The combination of large permanent mesoporosity, excellent thermal stability, and high surface area in RP-H200 makes it a promising candidate for clean energy storage and other functions.

Bispidine-Based Copper(II) Coordination Polymers with Remarkable Dynamic Properties, Selective Volatile Organic Compounds Adsorption, and Exchange Capabilities

This study presents novel bispidine-based Cu(II) coordination polymers (CPs) with remarkable dynamic properties, volatile organic compounds (VOCs) exchange, and selective adsorption capabilities. The coordination requirements of Cu(II) enable, as demonstrated by SC-XRD and Powder X-ray diffraction (P-XRD), the formation of either 1D ribbon-like (1-TCMSC and 1-H2OSC) or 2D (1-MeCNSC) extended frameworks depending on the ability of the trapped solvents to interact as hydrogen bond (HB) donor with the metal's counterion. Hirshfeld Surface (HS) analysis and in situ VT SC- and P-XRD experiments reveal different interchain interactions in 1D vs 2D CPs. Solvent exchange experiments on both single crystals (SCs) and microcrystalline samples, set up to evaluate differences in the CPs' dynamic nature, confirm the drastic effect of CP dimensionality. Additionally, an amorphous desolvated phase 1-AmorphPwd was tested for VOC adsorption and demonstrated to display affinity for acetonitrile and nitromethane, with high selectivity for the latter, but also to have the ability to trap aromatic VOCs, capturing up to ca. 2 mmol/g of solvent. The adsorption experiments, conducted at r.t., 1 atm, and no prior activation, underscore the potential of these materials for environmental and industrial applications. This work emphasizes the unique dynamic and selective behavior of bispidine-based CPs and provides a foundation for their scalability and practical implementation in VOCs capture technologies.

Discovering Ultra-Stable Metal-Organic Frameworks for CO2 Capture from A Wet Flue Gas: Integrating Machine Learning and Molecular Simulation

The rapid increase in atmospheric CO2, arising from anthropogenic sources, has posed a severe threat to global climate and raised widespread environmental concern. Metal-organic frameworks (MOFs) are promising adsorbents to potentially reduce CO2 emissions from flue gases. However, many MOFs suffer from structural degradation and performance deterioration upon exposure to water in flue gases. Aiming to discover stable and efficient MOFs for CO2 capture from a wet flue gas, we propose a hierarchical high-throughput computational screening (HTCS) strategy. Machine learning (ML)-assisted stability analysis is incorporated within the HTCS, leveraging prior experimental experience to predict ultrastable (including water-, thermal-, and activation-stable) MOFs from ∼280,000 candidates in the ab initio REPEAT charge MOF (ARC-MOF) database. Among 9755 shortlisted MOFs, molecular simulations identify 1000 top-performing MOFs. Remarkably, several vanadium-based MOFs are revealed to be ultrastable, exhibiting high CO2 capture capability of 3-7 mmol/g and CO2/N2 selectivity of 95-401. Subsequently, ML regressors are developed to derive design principles for MOFs capable of overcoming the trade-off effect. Furthermore, an ML classifier is developed to analyze the impact of water on CO2 capture by comparing dry and wet conditions. The proposed hierarchical HTCS and developed ML models lay a solid foundation for the potential transition of MOFs into practical applications.

Beyond Numerical Hessians: Higher-Order Derivatives for Machine Learning Interatomic Potentials via Automatic Differentiation

The development of machine learning interatomic potentials (MLIPs) has revolutionized computational chemistry by enhancing the accuracy of empirical force fields while retaining a large computational speed-up compared to first-principles calculations. Despite these advancements, the calculation of Hessian matrices for large systems remains challenging, in particular because analytical second-order derivatives are often not implemented. This necessitates the use of computationally expensive finite-difference methods, which can furthermore display low precision in some cases. Automatic differentiation (AD) offers a promising alternative to reduce this computational effort and makes the calculation of Hessian matrices more efficient and accurate. Here, we present the implementation of AD-based second-order derivatives for the popular MACE equivariant graph neural network architecture. The benefits of this method are showcased via a high-throughput prediction of heat capacities of porous materials with the MACE-MP-0 foundation model. This is essential for precisely describing gas adsorption in these systems and was previously possible only with bespoke ML models or expensive first-principles calculations. We find that the availability of foundation models and accurate analytical Hessian matrices offers comparable accuracy to bespoke ML models in a zero-shot manner and additionally allows for the investigation of finite-size and rounding errors in the first-principles data.

Luminescent Alkylaluminium Anthranilates Reaching Unity Quantum Yield in the Condensed Phase

Transition, post-transition and rare earth metal complexes supported by (O,N)- and (N,N)-type ligands dominate organometallic photochemistry. However, despite a vast number of aminobenzoate metal complexes having been reported, and aluminium being globally abundant, alkylaluminium anthranilates have not yet been considered as effective luminophores. Herein, using a family of commercially available ligands composed of anthranilic acid (anth-H2) and its N-substituted derivatives, we report the isolation and characterisation of a series of unique tetrameric chiral-at-metal alkylaluminium anthranilates, [(R'-anth)AlR]4. The resulting compounds are characterised using spectroscopic methods and single-crystal X-ray diffraction to analyse structure-determining factors in the solid state and solution. Moreover, by changing the N-substituents from H to Me and Ph, we have yielded a series of luminophores that exhibit poor-to-excellent performance, providing a [(Ph-anth)AlEt]4 derivative that achieves a unity photoluminescence quantum yield in the condensed phase, which is unprecedented for aluminium complexes.

Emerging frontiers in chiral metal-organic framework membranes: diverse synthesis techniques and applications

Chirality is a basic and universal property in nature, refering to the asymmetry of molecules, where they do not coincide with their mirror images. Chiral materials, in multiple forms, usually exhibit unique physical phenomena such as chiral luminescence and distinctive chemical properties. Metal-organic framework (MOF) membranes have high porosity and abundant active sites; thus, they are an excellent candidate for functionalization. With the involvement of chiral units, chiral MOF membranes demonstrate great potential in applications such as chiral sensing, separation and luminescence. In this review, we first introduce the up-to-date preparation methods for chiral MOF membranes, including direct and indirect methods, and then discuss their applications in enantiomer recognition, chiral separation, and circularly polarized luminescence. Finally, we summarize the challenges in developing chiral MOF membranes and provide a perspective on future developments.

Machine Learning Reveals In-Cavity Versus Surface Activity for Selective C─H Borylation by Metal-Organic Framework Catalysts

Metal-organic frameworks (MOFs) provide an expansive and tunable platform for heterogeneous catalysis, yet distinguishing between catalytic reactions occurring within their pores and those on their external surfaces remains a challenge. This study employs interpretable machine learning to elucidate structure-activity relationships in MOF-supported nickel (Ni) catalysts for selective sp3 and sp2 C─H borylation. By analyzing over 470 000 MOF structures, we developed a set of 45 concise and chemically meaningful descriptors that capture key structural variations across MOFs. These descriptors enabled us to identify the critical factors governing sp3 versus sp2 selectivity, revealing distinct activation mechanisms: sp3 C─H borylation preferentially occurs within MOF cavities via a radical-mediated hydrogen atom transfer (HAT) mechanism, whereas sp2 C─H borylation is associated with surface or defect sites, favoring a concerted metalation-deprotonation (CMD) pathway. Guided by these insights, we designed Ni catalysts that achieve up to 97.8% sp3 selectivity and 88.7% sp2 selectivity. This work provides a systematic framework for rational catalyst design and establishes generalizable principles for controlling activity preference in MOF-supported catalysis.

A Zirconium-Based Metal-Organic Framework as an Effective Green Catalyst for the Synthesis of Biodiesel

CAU-28 (CAU = Christian-Albrechts-University) is a zirconium-based metal-organic framework (MOF) that features a bio-renewable linker (furan-2,5-dicarboxylic acid) and can be obtained through a green synthesis. In this work, we report an optimized synthesis of CAU-28, substantially enhancing the yield from 2 to 53 %. Moreover, taking advantage of the high thermal and chemical stability of CAU-28 as well as the MOF's surface area (> 1000 m2 g-1), porosity, and four open metal sites per Zr6-cluster, we have demonstrated the high potential of CAU-28 as a green catalyst to produce biodiesel through esterification reactions. Under optimized catalytic conditions, CAU-28 is able to convert oleic acid to its fatty acid methyl ester counterpart with high selectivity, using a catalyst loading of only 5 wt % and 1:24 molar ratio of oleic acid:methanol, at 90 °C for 90 min. Furthermore, the catalyst also shows high stability, maintaining its activity for three reaction cycles.

Towards effective Pd nanoparticles immobilization on NH2-MIL-53(Al) coated cellulose fiber: A stable and efficient catalyst for Suzuki reaction

The modification of cotton fibers with sodium chloroacetate, followed by the incorporation of NH2-MIL-53(Al) through covalent bonding, has been successfully developed as a support for the immobilization of palladium nanoparticles. The integration of NH2-MIL-53(Al) into cellulose enhanced the specific surface area and introduced a significant number of amino groups and pore structures, which physically isolated the metal sites. Additionally, the introduction of nitrogen heteroatoms offers numerous anchoring points, effectively preventing the loss and aggregation of the metal species. Transmission electron microscopy (TEM) analysis demonstrated that palladium nanoparticles were uniformly distributed throughout the matrix, with an average particle size of 1.29 nm. The catalytic performance of this catalyst was evaluated in the Suzuki-Miyaura reaction, which facilitates the coupling of aryl halides with arylboronic acids in the presence of 0.006 mol% palladium species. Notably, the catalyst exhibited good reusability, maintaining its catalytic performance over four cycles without a significant loss of activity.

2D Rhodium-Isocyanide Frameworks

2D metal-organic frameworks (2D MOFs) are emerging organic van der Waals materials with great potential in various applications owing to their structural diversity, and tunable optoelectronic properties. So far, most reported 2D MOFs rely on metal-heteroatom coordination (e.g., metal-nitrogen, metal-oxygen, and metal-sulfur); synthesis of metal-carbon coordination based 2D MOFs remains a formidable challenge. This study reports the rhodium-carbon (Rh-C) coordination-based 2D MOFs, using isocyanide as the ligand and Rh(I) as metal node. The synthesized MOFs show excellent crystallinity with quasi-square lattice networks. These MOFs show ultra-narrow bandgaps (0.1-0.28 eV) resulting from the interaction between Rh(I) and isocyano groups. Terahertz spectroscopy demonstrates exceptional short-range charge mobilities up to 560 ± 46 cm2 V-1 s-1 in the as-synthesized MOFs. Moreover, these MOFs are used as electrocatalysts for nitrogen reduction reaction and show an excellent NH3 yield rate of 56.0 ± 1.5 µg h-1 mgcat -1 and a record Faradaic efficiency of 87.1 ± 1.8%. In situ experiments reveal dual pathways involving Rh(I) during the catalytic process. This work represents a pioneering step toward 2D MOFs based on metal-carbon coordination and paves the way for novel reticular materials with ultra-high carrier mobility and for versatile optoelectronic devices.

Modulation of interface structure on titanium-based metal-organic frameworks heterojunctions for boosting photocatalytic carbon dioxide reduction

Rational regulation of interface structure in photocatalysts is a promising strategy to improve the photocatalytic performance of carbon dioxide (CO2) reduction. However, it remains a challenge to modulate the interface structure of multi-component heterojunctions. Herein, a strategy integrating heterojunction with facet engineering is developed to modulate the interface structure of metal-organic frameworks (MOF)-based heterojunctions. A series of core-shell UiO-66 (Zr-MOF)-loaded MIL-125 (Ti-MOF) heterojunctions with exposed specific facets were prepared to enhance the separation efficiency of photogenerated electrons-holes in CO2 photoreduction. Impressively, MIL-125to@UiO-66 with exposed {1 1 1} facet exhibits an excellent CO production rate (56.4 μmol g-1 h-1) and selectivity (99 %) under visible light irradiation without any photosensitizers/sacrificial agents, being 1.4 and 11.3 times higher than individual MIL-125to and UiO-66, respectively. The type-II heterojunction significantly enhances the separation of photogenerated electrons-holes in physical space. The photogenerated electrons migrate from Zr in UiO-66 to Ti in MIL-125to, promoting a spatial synergy between CO2 reduction on MIL-125to and H2O oxidation on UiO-66. Compared with MIL-125rd@UiO-66 with exposed {1 1 0} facet and MIL-125ds@UiO-66 with exposed {0 0 1} facet, MIL-125to@UiO-66 with exposed {1 1 1} facet improves the exposure of surface-active Ti sites, thereby enhancing the adsorption/activation of CO2 to generate the *COOH intermediate. This work provides an effective strategy for designing MOF-based heterojunction photocatalysts to improve photocatalytic performance.

Interwoven Porous Pristine Cobalt-Based Metal-Organic Framework as an Efficient Photocatalyst for CO2 Reduction

As a desired utilization of the conversion of CO2 into valuable carbon fuel production under solar energy, it remains challenging due to the lack of efficient catalysts. Herein, a 3D interpenetrating metal-organic framework of [Co(Tipa)(HCOO)2(H2O)]·H2O (Co-Tipa) with 1D open channel is solvothermally synthesized using a semi-flexible ligand (Tipa = tri-(4-(1H-imidazol-1-yl)-phenyl)amine). The tridentate bridge ligand-oriented periodicity Co-Tipa MOF is combined with ruthenium-based photosensitizers under mild reaction conditions to form an efficient nonhomogeneous co-catalyst for photocatalytic CO2 reduction reaction (CO2RR). As a crystalline MOFs catalyst, the CO production rate, selectivity, and the quantum yield under visible light irradiation offer outstanding performance for the synergistic advantages of structural feature, metal center, and organic ligand. The stability and reusability of the Co-Tipa co-catalyst in the reaction system are profited from the robust 3D entangled framework. The mechanism of how to enhance CO2RR performance for the Co-Tipa is assisted in illustration through density functional theory (DFT) calculations. By leveraging the unique structural properties of entangled MOFs, this study offers innovative approaches for the development of more effective and s Co-Tipa catalysts that can selectively CO2 into valuable chemicals and fuels.

Atomic Force Microscopy Strategies for Capturing Guest-Induced Structural Transitions in Single Flexible Metal-Organic Framework Particles

Flexible metal-organic frameworks (MOFs) exhibit stepped adsorption isotherms due to structural transitions between narrow-pore (np) and large-pore (lp) states. This characteristic stepwise uptake at a certain pressure results in adsorptive high working capacities, making these materials highly effective for energy-efficient gas storage and separation processes. The transition pressure, which is key to enhancing separation efficiency, can be tuned by varying the particle size of flexible MOFs. However, a comprehensive understanding of size-dependent effects has been limited due to particle size distribution in samples. Conventional adsorption measurements provide only averaged isotherms for powder samples, and analyzing the size effect at the single-particle level requires experimental techniques that can capture transition behavior of individual particles separately. This study utilized atomic force microscopy coupled with thermodynamic analysis to investigate guest-induced structural transitions. Force application to a MOF particle triggered a structural change from the lp to np state, generating force profiles that were analyzed to uncover the underlying transition mechanisms and calculate transition pressures using free energy analysis. The evaluation revealed distinct transition mechanisms for two flexible MOFs: ELM-12 exhibited a step-by-step mechanism, while DUT-8(Ni) displayed an all-at-once transition. Force profile analysis enabled precise determination of the free energy changes and transition pressures for individual particles. This approach provided detailed insights into the transition mechanisms and their impact on overall adsorption isotherms, offering a novel perspective on how single-particle behavior influences bulk material performance.

Black Phosphorus: Paving the Way for Flexible Supercapacitors in Wearable Electronics

The utilization of flexible supercapacitors (FSCs) is gaining momentum in the realm of wearable electronics, owing to their multifarious advantages and immense potential for future applications. Black phosphorus (BP) is rapidly emerging as an auspicious material in the field of FSCs. The exceptional features of this material, including its remarkable surface area, excellent carrier mobility, anisotropic characteristics, impressive electrical conductivity, and rapid ion diffusion properties, render it highly suitable for practical applications. Some specifications, such as design, development, and safety concerns of emerging electrode materials for FSCs in wearable electronics, are highlighted here. This review briefly explains the various synthesis methods for bulk BP, single-layer and few-layer BP (FL-BP) fabrication methods, and black phosphorus quantum dots (BPQDs). Both top-down and bottom-up approaches are addressed for producing single/FL-BP. Also, this review discusses the interaction of BP with other 2D materials to make a synergistic effect and compares the electrochemical performance. Discover the latest breakthrough in wearable electronics with the first-ever review of BP-based FSC applications. From technical specifications to real-world applications, this review covers everything to know to stay ahead of the curve. So buckle up and get ready to explore the exciting world of BP-based FSC devices.

Construction of metal-organic nanostructures and their structural transformations on metal surfaces

Metal-organic nanostructures, composed of organic molecules as building blocks and metal atoms as linkers, exhibit high reversibility and flexibility and open up new vistas for the creation of novel metal-organic nanomaterials and the fabrication of functional molecule-based nanodevices. With the rapid development of emerging surface science and scanning probe microscopy, various metal-organic nanostructures, ranging from zero to two dimensions, have been prepared with atomic precision on well-defined metal surfaces in a bottom-up manner and further visualized at the submolecular (or even atomic) level. In such processes, the metal-organic interactions involved and the synergy and competition of multiple intermolecular interactions have been clearly discriminated as the cause of the diversity and preference of metal-organic nanostructures. Moreover, structural transformations can be controllably directed by subtly tuning such intermolecular interactions. In this perspective, we review recent exciting progress in the construction of metal-organic nanostructures on metal surfaces ranging from zero to two dimensions, which is mainly in terms of the selection of metal types (including sources), in other words, different metal-organic interactions formed. Subsequently, the corresponding structural transformations in response to internal or external conditions are discussed, providing mechanistic insights into precise structural control, e.g., by means of metal/molecule stoichiometric ratios (including through scanning probe microscopy (SPM) manipulations), thermodynamic control, introduction of extrinsic competing counterparts, etc. In addition, some other regulatory factors, such as the functionalization of organic molecules and the choice of substrates and lattices, which also crucially govern the structural transformations, are briefly mentioned in each part. Finally, some potential perspectives for metal-organic nanostructures are evoked.

Defect-Tailoring Metal-Organic Frameworks for Highly Fast-Charging Quasi-Solid-State Electrolytes Lithium Metal Batteries

Metal-organic frameworks (MOFs) show revolutionary potential in quasi-solid-state electrolytes (QSSEs) designed for high-energy-density batteries, owing to their tunable nanoporous structures and open metal sites (OMSs). However, their application is hindered by insufficient Li+ dissociation and low ionic conductivity, attributed to limited metal active sites. This study employed defect engineering to modulate hafnium-based MOFs, increasing OMS density while optimizing the pore microenvironment. The engineered defects improve the Lewis acid strength of OMSs, driving lithium salt dissociation and establishing strong chemisorption of TFSI- anions. By synergistically optimizing defect density, Lewis acidity, and structural stability, the defect-engineered Hf-MOF-QSSE achieved an ionic conductivity of 1.0 mS cm-1 at 30 °C and delivered a critical current density of 2 mA cm-2, surpassing previously reported MOF-QSSEs, underscoring the pivotal role of defect engineering in electrolyte optimization. Furthermore, Li||LiFePO4 cells exhibited excellent cycling stability and ultrahigh rate capability, retaining 93% of their capacity after 1500 cycles at 10C, while Li||NCM811 cells maintained a specific capacity of 85 mAh g-1 after 600 cycles at 5C.

Hierarchical Engineering of Single-Crystalline Mesoporous Metal-Organic Frameworks with Hollow Structures

Although the superiority of hierarchical structure has driven extensive demand for applications, establishing hierarchy in a long-range-ordered single crystal remains a formidable challenge due to the inherent competition and contradiction between single crystallinity and controllable hierarchical structure. Herein, we demonstrate a growth and dissociation kinetics cooperative strategy for synthesizing a family of hollow single-crystalline mesoporous metal-organic frameworks (meso-MOFs) with hierarchical structures. The approach employs a dual-template method, integrating both hard and soft templates. By adjusting the HCl/CH3COOH ratio, the reaction system's pH can be tuned to regulate the dissociation kinetics of the acid-sensitive seeds serving as hard templates for the formation of hollow structure, while simultaneously modifying the concentration of the dual acids to control the growth kinetics of meso-MOF shells. The competition between maintaining a single crystallinity and achieving a well-defined hierarchical structure can be effectively balanced. Driven by the two interfacial kinetics, we successfully obtained the octahedral meso-MOF nanoparticles that not only exhibit a well-defined hollow structure with precisely controllable hollow size (∼81-1120 nm) and tunable wall thickness (∼28.6-61.3 nm) but also retain their single-crystal integrity. Specifically, the dissociation kinetics of seeds governed the formation of hollow structures, while the growth kinetics of single-crystalline meso-MOF shells ensured uniform coverage and structural integrity. Based on this strategy, we further developed a series of novel hollow meso-MOFs with hierarchical nanostructures, including hollow open-capsule meso-MOFs, 2D hollow meso-MOFs, hollow interlayer-structured meso-MOFs, macro-meso-micro trimodal porous MOFs, and so on.

Modulator approach for the design and synthesis of anisotropic multi-domain metal-organic frameworks

Multi-domain metal-organic frameworks (MD-MOFs) consist of chemically-distinct interconnected MOF domains. Most commonly they are isotropic, with core-shell and stratified MOFs representing classic examples in which a core MOF is concentrically encased in one or more MOF shells. Anisotropic multi-domain MOFs (AMD-MOFs) are much rarer and are projected to exhibit unique properties that depend on domain sequence, composition, and 3-D spacial distribution. However, straightforward approaches for their synthesis and construction are underdeveloped. We present and describe a modulator-based strategy for preparing a diverse collection of AMD-MOFs. Designed coordination modulators were used to inhibit secondary domain growth along certain facets of seed MOF crystals. Through multistep syntheses, this strategy allows for controlled construction of AMD-MOFs with different domain distributions that depend on modulator identity and domain synthesis sequence. The reported results represent important steps toward realizing a more general synthetic approach for fabricating arbitrarily complex AMD-MOFs, which is crucial for enabling broader exploration and study of their properties, functions, and applications.

Metal Organic Framework Impregnated Nanofibrous Aerogels: A 3D Structured Matrix for CO2 Capture

This study explores the synthesis and functionality of mesoporous UiO-66-NH2 metal-organic framework (MOF) impregnated cellulose diacetate (CDA)-silica hybrid nanofibrous aerogels (NFAs) for selective CO2 capture. Mesoporous MOFs generally outperform microporous MOFs for CO2 capture, while NFAs provide a lightweight, highly porous material platform consisting of a three-dimensional (3D) network of interlinked nanofibers, offering both mechanical strength and a larger surface area. We exploit the attributes of these candidate materials by producing CDA-silica@UiO-66-NH2 NFA through a simple freeze-drying process involving a mixture of CDA-silica nanofiber dispersions and mesoporous UiO-66-NH2 nanoparticles in tert-butanol, avoiding cumbersome pre- or postprocessing typical in aerogel synthesis. The aerogels exhibit a hierarchical porous structure, allow for MOF loadings of up to 80 wt %, and demonstrate remarkable CO2 adsorption performance, with a direct correlation between MOF content and adsorption efficiency. Notably, an NFA containing 80 wt % MOF achieves a CO2 uptake of 2.5 mmol/g at 35 °C and atmospheric pressure. The CDA-silica@UiO-66-NH2 NFA also exhibits a strong preference for CO2 adsorption compared to N2 across all pressure levels when exposed to a gas mixture of CO2 and N2 in an 85:15 ratio. The CO2/N2 selectivity (Sads) usually calculated by using the ideal adsorption solution theory (IAST) reveals a value of 18.2 at 298 °K for this system. The NFA also displays strong mechanical resiliency including compressibility and fatigue resistance, and MOF integration without detachment during multiple compression cycles. Unlike traditional CO2 capture materials, our CDA-silica@UiO-66-NH2 NFA with a combination of high CO2 selectivity, structural integrity, and ease of fabrication thus offers a potentially scalable solution that addresses both performance and durability in real-world applications.

Crystal Phase Transition-Driven Integration of Enzymes into 2D Metal-Organic Frameworks

In situ encapsulation of enzymes within a metal-organic framework (MOF) represents a promising technique for engineering robust biocatalysts. However, the success of enzyme encapsulation is often constrained by intricate interfacial interactions between enzyme surfaces and MOF precursors, limiting the versatility of this MOF method. Herein, we introduce a phase transition strategy for encapsulating enzymes within a Zn-HHTP framework, demonstrating its effectiveness across a wide range of enzymes irrespective of their surface chemistry. In this approach, enzyme molecules are preloaded in a zinc oxide (ZnO) template through a simple yet efficient coprecipitation process, followed by a ZnO-to-Zn-HHTP MOF crystal phase transition in the presence of ligand precursors, resulting in the formation of a quasi-mesoporous hybrid Zn-HHTP MOF inside, for which the original enzymes are preserved. The long-range ordered quasi-mesopore channels enhance substrate accessibility to the immobilized enzymes, endowing enzyme@Zn-HHTP with higher catalytic activity compared to enzymes immobilized within the well-known MOF, ZIF-8, which has narrow apertures. Additionally, the resultant enzyme@Zn-HHTP exhibits exceptional structural stability across a broad pH range (3-14), and Zn-HHTP can provide robust protection against enzyme denaturation by heat, organic solvents, and proteases. This work offers a facile and reliable phase transition strategy for synthesizing active and robust MOF biocatalysts, advancing biocatalysis across various fields.

Synthesis and Characterisation of Multivariate Metal-Organic Frameworks for Controlled Doxorubicin Absorption and Release

The development of drug carriers with efficient absorption and controlled delivery properties is crucial for advancing medical treatments. Metal-organic frameworks (MOFs) with tunable porosity and a large surface area represent a promising class of materials for this application. Among them, NUIG4 stands out as a biocompatible MOF that exhibits exceptionally high doxorubicin (Dox) absorption (1995 mg dox/g NUIG4) and pH-controlled release properties. In this study, we report the synthesis and characterisation of multivariate MOFs (MV-NUIG4), which are analogues of NUIG4 that maintain the same topology while incorporating different functional groups within their framework. Eight new MV-NUIG4 MOFs have been synthesised through in situ reactions of the corresponding 4-aminobenzoic acid derivative with 4-formylbenzoic acid. The compounds were thoroughly characterised using a range of techniques, including powder X-ray diffraction, infrared spectroscopy, 1H-NMR, and single-crystal X-ray crystallography. The experimental ratio of the reagents and ligand precursors for the synthesis of MV-NUIG4 MOFs matched the ratio of the linkers in the final products. These structures incorporate additional functional groups, such as methyl and hydroxyl, in varying ratios. Computational modelling was used to provide further insight into the crystal structure of the MOFs, revealing a random distribution of the functional groups in the framework. The Dox absorption and release capacity of all analogues were studied, and the results revealed that all analogues displayed high drug absorption in the range of 1234-1995 mg Dox/g MOF. Furthermore, the absorption and release rates of the drug are modulated by the ratio of functional groups, providing a promising approach for controlling drug delivery properties in MOFs.

Nanochannel functionalization using POFs: Progress and prospects

Biomimetic nanochannels, inspired by natural ion channels found in living organisms, are synthetic systems designed to replicate the highly selective and efficient ion/molecule transport processes essential for various biological functions. These artificial channels mimic the structural and functional properties of their biological counterparts, offering precise control over ion and molecular transport. Porous organic framework materials (POFs), including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have emerged as promising materials for functionalizing nanochannels due to their unique structures and exceptional properties. This functionalization strategy not only enhances the performance of synthetic nanochannels but also broadens their application potential across various fields. This review comprehensively examines the recent progress in the preparation and application of POFs stereoscopic-functionalized solid nanochannels. Special emphasis is placed on their practical applications, including proton conduction, ion-selective membranes, photo-responsive materials, sensing and detection, chiral separation, and catalysis. Finally, the future development prospects and challenges in this research area are discussed, highlighting opportunities for advancing the design and application of biomimetic nanochannels.

Decoupled MOF Breathing: Pressure-Induced Reversal of Correlation Between Orthogonal Motions in a Diamondoid Framework

Responsive porous materials can outperform more rigid analogues in applications requiring precise triggering of molecular uptake/release, switching or gradual change in properties. We have uncovered an unprecedented dynamic response in the diamondoid MOF SHF-62, (Me2NH2)[In(BDC-NHC(O)Me)2] (BDC = 1,4-benzenedicarboxylate), by using pressure as a stimulus. SHF-62 exhibits two distinct framework "breathing" motions involving changes in 1) cross-section and 2) length of its 1D pores. Our study using synchrotron single-crystal X-ray diffraction in sapphire-capillary (p < 0.15 GPa) and diamond-anvil (0.15 < p < 5 GPa) cells reveals that different pressure regimes trigger positive and negative correlation between these two motions, requiring an unprecedented mechanical decoupling. Specifically, the DMF-solvated framework SHF-62-DMF, in DMF as pressure-transmitting medium, undergoes initial hyperexpansion of pore cross-section (p ≤ 0.9 GPa), due to DMF ingress, followed by reversal/reduction at p > 0.9 GPa while pore length contracts for all pressure increases, revealing decoupling of the two framework deformations. By contrast, nonpenetrating medium FC-70 imposes correlated compression (p < 1.4 GPa) of pore cross-section and length, resembling framework activation/desolvation motions but of greater magnitude. Similar behavior occurs for SHF-62-CHCl3 in CHCl3 (p < 0.14 GPa), suggesting minimal ingress of CHCl3. These findings change our understanding of MOF dynamic responses and provide a platform for future responsive materials development.

Two ratiometric fluorescent sensors originating from functionalized R6G@UiO-66s for selective determination of formaldehyde and amine compounds

Residual small amounts of harmful substances in food or medicine are potential threats to human health. In this work, amino-functionalized UiO-66 was firstly prepared, namely UiO-66-(a), then it was further treated with phosgene to obtain UiO-66-(b) with abundant carboxyl groups. By doping, the fluorescent Rhodamine 6G (R6G) was incorporated into the structures of the two functional UiO-66s to obtain R6G@UiO-66-(a) and R6G@UiO-66-(b), respectively. These two materials can both emit fluorescence based on UiO-66s and R6G, therefore, were employed as fluorescent probes to construct two ratiometric fluorescent sensors to detect formaldehyde and amine compounds, respectively. Based on the aldehyde-amine condensation reaction between -NH2 and -CHO and the specific condensation reaction between -COOH and -NH2, formaldehyde molecules and amine compounds can react with these two materials, respectively. Causing a change in the relative fluorescence intensity of functionalized MOFs, resulting in selective detection of formaldehyde and amine compounds with the detection limit of 0.058 μM and 0.0017 μM (ethylenediamine), respectively. These two ratiometric fluorescent probes were successfully applied for quantitative detection of formaldehyde in beer and ethylenediamine in anti-inflammatory agents, demonstrating great practical potential for residual hazardous substance monitoring in food or medicine.

Advancing Nanomaterial-Based Strategies for Alzheimer's Disease: A Perspective

Alzheimer's disease (AD) is a complex neurodegenerative disorder and the most common cause of dementia. By 2050, the number of AD cases is projected to exceed 131 million, placing significant strain on healthcare systems and economies worldwide. The pathogenesis of AD is multifactorial, involving hypotheses/mechanisms, such as amyloid-β (Aβ) plaques, tau protein hyperphosphorylation, cholinergic neuron damage, oxidative stress, and inflammation. Despite extensive research, the complexity of these potentially entangled mechanisms has hindered the development of treatments that can reverse disease progression. Nanotechnology, leveraging the unique physical, electrical, magnetic, and optical properties of nanomaterials, has emerged as a promising approach for AD treatment. In this Perspective, we first outlined the major current pathogenic hypotheses of AD and then reviewed recent advances in nanomaterials in addressing these hypotheses. We have also discussed the challenges in translating nanomaterials into clinical applications and proposed future directions, particularly the development of multifunctional and multitarget nanomaterials, to enhance their therapeutic efficacy and clinical applicability in AD treatment.

Mannosylated MOF Encapsulated in Lactobacillus Biofilm for Dual-Targeting Intervention Against Mammalian Escherichia coli Infections

Pathogenic bacterial infections pose a major concern, especially concerning mammalian enteritis and diarrhea. Compared to conventional antibiotic intervention, metal-organic frameworks (MOFs) exhibit superior antibacterial properties and lower cytotoxicity, demonstrating great promise in the treatment of pathogen-induced diarrhea. However, the achievement of their precise targeted delivery is still a significant challenge. Herein, a novel precision nano-system with a dual-targeting approach for treating intestinal infections caused by Escherichia coli (E. coli) is designed. First, Zn-MOF was synthesized based on ZnO, which possessed enhanced elimination of planktonic bacteria and biofilms. Through mannosylation, Zn-MOF@Man specifically recognized the FimH pili of E. coli, leading to its aggregation and subsequent eradication. Second, guided by whole genome sequencing, the encapsulation of Lactobacillus biofilm exertd immunomodulatory function, overcomed challenges related to intestinal targeting, and facilitated sustained drug release. Furthermore, Zn-MOF@Man/LRB maintaind microbiota equilibrium and promoted stem cell differentiation and barrier stability, ensuring consistent anti-diarrheal and anti-inflammatory efficacy in mice, piglets, and humans. This approach represents a novel dual-targeting antimicrobial strategy, combining probiotic biofilms and E. coli-oriented delivery, advancing safe and effective treatment that restores intestinal homeostasis for potential applications in both human medicine and animal husbandry.

Advancements in Carbon-Based Piezoelectric Materials: Mechanism, Classification, and Applications in Energy Science

The piezoelectric phenomenon has garnered considerable interest due to its distinctive physical properties associated with the materials involved. Piezoelectric materials, which are inherently non-centrosymmetric, can generate an internal electric field under mechanical stress, enhancing carrier separation and transfer due to electric dipole moments. While inorganic piezoelectric materials are often investigated for their high piezoelectric coefficients, they come with potential drawbacks such as toxicity and high production cost, which hinder their practical applications. Consequently, carbon-based piezoelectric materials have emerged as an alternative to inorganic materials, boasting advantages such as a large specific surface area, high conductivity, flexibility, and eco-friendliness. Research into the applications of carbon-based piezoelectric materials spans environmental remediation, energy conversion, and biomedical treatments, indicating a promising future. This review marks the first comprehensive attempt to discuss and summarize the various types of carbon-based piezoelectric materials. It delves into the underlying mechanisms by which piezoelectricity influences catalysis, biomedical applications, nanogenerators, and sensors. Additionally, various potential techniques are presented to enhance the piezoelectric performance. The design principles of representative fabrication strategies for carbon-based piezoelectric materials are analyzed, emphasizing their current limitations and potential improvements for future development. It is believed that recent advances in carbon-based piezoelectric materials will make a significant impact.

Direct Photopatterning of Zeolitic Imidazolate Frameworks via Photoinduced Fluorination

Precise and effective patterning strategies are essential for integrating metal-organic frameworks (MOFs) into microelectronics, photonics, sensors, and other solid-state devices. Direct lithography of MOFs with light and other irradiation sources has emerged as a promising patterning strategy. However, existing direct lithography methods often rely on the irradiation-induced amorphization of the MOFs structures and the breaking of strong covalent bonds in their organic linkers. High-energy sources (such as X-rays or electron beams) and large irradiation doses - conditions unfavorable for scalable patterning - are thus required. Here, we report a photoinduced fluorination chemistry for patterning various zeolitic imidazolate frameworks (ZIFs) under mild UV irradiation. Using UV doses as low as 10 mJ cm-2, light-sensitive fluorine-containing molecules covalently bond to ZIFs and enhance their stability in water. This creates a water-stability contrast between ZIFs in exposed and unexposed regions, enabling scalable direct photolithography of ZIFs with high resolution (2 μm) on 4-inch wafers and flexible substrates. The patterned ZIFs preserve their original crystallinity and porous properties while gaining increased hydrophobicity. This allows for the demonstration of a water-responsive fluorescent MOFs array with implications in sensing and multicolor information encryption.

Stabilization toward air and structure determination of pyrophoric ZnR2 compounds via supramolecular encapsulation

Dialkylzincs (ZnR2, R = Me or Et) are widely used reagents in organic synthesis and materials chemistry. However, at standard conditions, they exist as pyrophoric liquids reacting violently with water and dioxygen, thus being dangerous and difficult to use in daily laboratory work. Here, we show that these zinc dialkyls can be efficiently stabilized toward air by supramolecular encapsulation within a host system based on heteroleptic alkylzinc complexes. The noncovalent immobilization of ZnR2 molecules within the resultant crystalline networks allows their structural characterization in a new confined environment. The great potential of the reported assemblies is demonstrated by efficient separation of ZnMe2 from a mixture of ZnMe2/ZnEt2. The reported approach paves the way for original supramolecular systems for capture, stabilization, and storage of dangerous reagents.

Preparation of gold nanoparticles decorated UiO-66-NH2 incorporated epichlorohydrin and cyclodextrin as novel efficient catalyst in cross coupling and carbonylative reactions

This study presents a new, highly effective, and reusable catalyst: UiO-66-NH2@Epichlorohydrin@Cyclodextrin@Au-NPs. This innovative catalyst starts with the Zr-based UiO-66 material, which is functionalized with amino groups (-NH2). We enhanced its surface compatibility by modifying it with epichlorohydrin and cyclodextrin via a post-synthesis modification method. Gold nanoparticles were then stabilized on this modified composite, resulting in the UiO-66-NH2@Epichlorohydrin@Cyclodextrin@Au-NPs complex. We used this catalyst for C-C coupling and Carbonylative Sonogashira reactions in mild conditions. Its effectiveness was underscored by various analytical techniques, including XRD, EDS, SEM, FT-IR, TEM, BET, ICP, TGA, and elemental mapping. The catalyst exhibited exceptional performance in Sonogashira, Heck, Suzuki coupling, and Carbonylative reactions, achieving good to excellent yields. It proved to be highly recyclable, maintaining its catalytic activity for up to nine cycles with minimal loss.

Single-Atom Fe Catalysts With Improved Metal Loading for Efficient Ammonia Synthesis Under Mild Conditions

Ammonia synthesis is a cornerstone in the chemical industry. Given that the traditional Haber-Bosch (H-B) process requires very high temperature and pressure, it is imperative to develop catalysts capable of facilitating ammonia synthesis under mild conditions. In this work, a post-metal replacement strategy is developed to improve the Fe loading in single-atom Fe-implanted N-doped carbon catalysts. Starting from the Zn-Fe-N-C material with single-atom Zn and Fe sites coexisting in N-doped porous carbon pyrolyzed from porphyrinic metal-organic frameworks (MOFs), the replacement of single-atom Zn with Fe sites is performed, which significantly increases the Fe loading from 1.33 to 2.39 wt%. This effectively suppresses the migration and agglomeration of Fe, yielding Fe-N-C with high metal loading (FeHL-N-C). Notably, the FeHL-N-C catalyst exhibits a catalytic rate of 558 µmol·gcat -1·h-1 at 300 °C for ammonia synthesis at atmospheric pressure, far surpassing the performance of the traditional dominant fused iron and even Ru-based precious metal catalysts.

Real-Time Monitoring of Fe-Induced Stable γ-NiOOH in Binder-Free FeNi MOF Electrocatalysts for Enhanced Oxygen Evolution

Hydrogen energy is a promising renewable source, and metal-organic frameworks (MOFs) are considered potential electrocatalysts for water electrolysis due to their abundant active sites, high porosity, and large surface area. The synthesis of bimetallic iron-nickel-benzene-1,3,5-tricarboxylate/nickel foam (FeNi-BTC/NF) MOF is reported using a binder-free one-pot method by immersing nickel foam (NF) into a solution of benzene-1,3,5-tricarboxylic acid (BTC), N,N-dimethylformamide (DMF), and iron (Fe) salts. FeNi-BTC/NF exhibits a low overpotential of 276 mV at 100 mA cm- 2, a Tafel slope of 94 mV dec-1, and stability exceeding 120 h. The Fe-Ni interaction facilitates the formation of a stable gamma-nickel oxyhydroxide (γ-NiOOH) phase, preventing its reversion to nickel hydroxyide (Ni(OH)₂), which is crucial for improving oxygen evolution reaction (OER) performance. This phase transition, revealed via in situ Raman spectroelectrochemical analysis, enhances electrocatalytic activity. Additionally, high-valent Fe modulates the electronic structure of Ni, enabling FeNi-BTC/NF to transform into γ-NiOOH at higher potentials, with Fe and γ-NiOOH synergistically boosting OER efficiency. The findings offer insights into Fe/Ni atom interactions and phase transformations in FeNi-BTC/NF MOFs for enhanced water splitting.

Metal-Organic Frameworks: Unlocking New Frontiers in Cardiovascular Diagnosis and Therapy

Cardiovascular disease (CVD) is one of the most critical diseases which is the predominant cause of death in the world. Early screening and diagnosis of the disease and effective treatment after diagnosis play an important role in the patient's recovery. Metal-organic frameworks (MOFs), a kind of hybrid ordered micro or meso-porous materials, constructed by metal nodes or clusters with organic ligands, due to their special features like high porosity and specific surface area, open metal sites, or ligand tunability, are widely used in various areas including gas storage, catalysis, sensors, biomedicine. Recently, advances in MOFs are bringing new developments and opportunities for the healthcare industry including the theranostic of CVD. In this review, the applications of MOFs are illustrated in the diagnosis and therapy of CVD, including biomarker detection, imaging, drug delivery systems, therapeutic gas delivery platforms, and nanomedicine. Also, the toxicity and biocompatibility of MOFs are discussed. By providing a comprehensive summary of the role played by MOFs in the diagnosis and treatment of CVDs, it is hoped to promote the future applications of MOFs in disease theranostics, especially in CVDs.

Nanoconfined Solvothermal Synthesis of Defective 1T-MoS2 Monolayers with High Electrocatalytic Performance

Synthesizing 2D nanosheets in a controlled and scalable manner remains a significant challenge. Here, a nanoconfined solvothermal synthesis is presented of metallic phase MoS2 (1T-MoS2) monolayers at kilogram scale. The MoS2 nanosheets exhibit a remarkably high monolayer ratio of 97%, a 1T content of ≈89%, and a well-defined average lateral size ranging from ≈100 nm to 1.0 µm, with a narrow size distribution. Moreover, these nanosheets possesses abundant surface defects, and the defect density can be regulated in situ through changing the reaction conditions. Intriguingly, the monolayer MoS2 nanosheets demonstrate good dispersibility and high stability in various solvents, including water, ethylene glycol, dimethyl formamide and others, with a high concentration of up to 1.0 mg mL-1. They are also proven to be high-performance electrocatalysts for the hydrogen evolution reaction, exhibiting an overpotential of 315 mV at an industrial current density of 1000 mA cm-2 and maintaining constant current densities of 500 mA cm-2 for up to 100 h, surpassing the performance of the commercial 20 wt.% Pt/C. Our strategy represents a significant advancement in the controlled synthesis of monolayer MoS2 at scale, providing a promising avenue for the practical application of 2D materials.

Selectivity in Chemiresistive Gas Sensors: Strategies and Challenges

The demand for highly functional chemical gas sensors has surged due to the increasing awareness of human health to monitor metabolic disorders or noncommunicable diseases, safety measures against harmful greenhouse and/or explosive gases, and determination of food freshness. Over the years of dedicated research, several types of chemiresistive gas sensors have been realized with appreciable sensitivities toward various gases. However, critical issues such as poor selectivity and sluggish response/recovery speeds continue to impede their widespread commercialization. Specifically, the mechanisms behind the selective response of some chemiresistive materials toward specific gas analytes remain unclear. In this review, we discuss state-of-the-art strategies employed to attain gas-selective chemiresistive materials, with particular emphasis on materials design, surface modification or functionalization with catalysts, defect engineering, material structure control, and integration with physical/chemical gas filtration media. The nature of material surface-gas interactions and the supporting mechanisms are elucidated, opening opportunities for optimizing the materials design, fine-tuning the gas sensing performance, and guiding the selection of the most appropriate materials for the accurate detection of specific gases. This review concludes with recommendations for future research directions and potential opportunities for further selectivity improvements.

Piezoelectric Transition in a Nonpyroelectric Gyroidal Metal-Organic Framework

Among the thirty-two crystallographic point groups, 432 is the only one that lacks an inversion center but does not exhibit piezoelectricity. A gyroidal structure belongs to point group 432 and shows characteristic physical properties attributed to its distinctive strong isotropic network. Here, we investigate a gyroidal cobalt oxalate metal-organic framework (MOF) with disordered orientations of SO4 tetrahedra. Synchrotron X-ray diffraction experiments using a single crystal reveal a cubic-to-cubic structural phase transition at TS = 120 K. This transition involves a change in the point group from nonpiezoelectric 432 to piezoelectric 23. The symmetry change arises from the ordering of distorted SO4 molecules, leading to a three-dimensional helical arrangement of electric dipole moments. Furthermore, pyroelectric current measurements using polycrystalline pellet samples reveal that electric polarization emerges below TS depending on the magnitude of the pelletizing pressure, demonstrating piezoelectricity. The gyroidal MOF offers an opportunity to explore unique dielectric properties induced by the helical ordering of molecules and structural flexibility.

Three-Dimensional Covalent Organic Frameworks with jcg Topology Based on a Trinodal Strategy

The development of three-dimensional (3D) covalent organic frameworks (COFs) holds significant promise for various applications, but the conventional uninodal or binodal design strategies limit their structural diversity. In this work, we present a novel trinodal strategy for the synthesis of 3D COFs featuring both microporous and mesoporous nanochannels. Using powder X-ray diffraction (PXRD), computational simulations, and high-resolution transmission electron microscopy (HR-TEM), we demonstrate that employing an 8-c building block with reduced symmetry, which can be considered as 4- and 3-connected subunits, along with planar 4-c building blocks, results in an unprecedented [4 + 3 + 4]-c jcg net. This structure features rare saddle-shaped eight-membered rings and mirror-symmetrical chains. Furthermore, the incorporation of chromophore pyrene and redox-active triphenylamine components, coupled with structural conjugation, imparts tunable photophysical and electronic properties to these COFs, making them promising candidates for photocatalytic H2O2 production. This work highlights the potential of the trinodal strategy in creating intricate COF architectures and enhances their applicability in heterogeneous photocatalysis.

Engineering Photoluminescence of Lanthanide Doped Yttrium-MOF-76 for Volatile Organic Compound Sensing

A set of three-dimensional metal-organic frameworks, named MOF-76, belonging to the tetragonal P4322 space group, based on [Y(BTC)(H2O)](DMF)1.1 (1,3,5-benzenetricarboxylate) doped with Eu3+, Tb3+, and Eu3+/Tb3+ were obtained under solvothermal conditions and fully characterized by powder X-ray diffraction, thermal, and vibrational analyses. In addition, upon UV light excitation (280 nm), all the powdered samples exhibited fine 4f-4f transitions, of which the 5D0 → 7F2 (Eu3+) and 5D4 → 7F5 (Tb3+) were the most intense ones. All samples were photophysically analyzed by determining the luminescence lifetimes, and their emission colors were quantified by calculating their chromaticities and color purities. Moreover, the intrinsic quantum yield, radiative, and non-radiative constants were calculated and compared to establish a structure-property relationship. Specifically, the Eu/Tb co-doped sample was employed to monitor its hypersensitive emissions in the presence of small volatile organic compounds (VOCs), showing quenching or enhancement of emission in protic and non-protic solvents. Furthermore, DFT calculations were carried out to understand the energy transfer processes between the sensor and the respective analytes. These results are promising for the development of solid-state lighting devices and colorimetric chemical sensors for specific compounds.

Selective two-electron and four-electron oxygen reduction reactions using Co-based electrocatalysts

The oxygen reduction reaction (ORR) can take place via both four-electron (4e-) and two-electron (2e-) pathways. The 4e- ORR, which produces water (H2O) as the only product, is the key reaction at the cathode of fuel cells and metal-air batteries. On the other hand, the 2e- ORR can be used to electrocatalytically synthesize hydrogen peroxide (H2O2). For the practical applications of the ORR, it is very important to precisely control the selectivity. Understanding structural effects on the ORR provides the basis to control the selectivity. Co-based electrocatalysts have been extensively studied for the ORR due to their high activity, low cost, and relative ease of synthesis. More importantly, by appropriately designing their structures, Co-based electrocatalysts can become highly selective for either the 2e- or the 4e- ORR. Therefore, Co-based electrocatalysts are ideal models for studying fundamental structure-selectivity relationships of the ORR. This review starts by introducing the reaction mechanism and selectivity evaluation of the ORR. Next, Co-based electrocatalysts, especially Co porphyrins, used for the ORR with both 2e- and 4e- selectivity are summarized and discussed, which leads to the conclusion of several key structural factors for ORR selectivity regulation. On the basis of this understanding, future works on the use of Co-based electrocatalysts for the ORR are suggested. This review is valuable for the rational design of molecular catalysts and material catalysts with high selectivity for 4e- and 2e- ORRs. The structural regulation of Co-based electrocatalysts also provides insights into the design and development of ORR electrocatalysts based on other metal elements.

Engineering Supramolecular Binding Sites in an Ultrastable and Hydrophobic Metal-Organic Framework for C2H6/C2H4 Separation

The separation of ethane (C2H6) from ethylene (C2H4) is critical for obtaining polymer-grade C2H4. Adsorptive separation with C2H6-selective MOFs offers a viable alternative to energy-intensive cryogenic distillation, enabling the direct production of high-purity C2H4. In this study, we developed an ultrastable ethane-selective metal-organic framework, UiO-67-(CH3)2, which demonstrates enhanced C2H6 adsorption (4.10 mmol g-1 at 1 bar and 298 K), higher C2H6/C2H4 selectivity of 1.70, and an increased C2H6/C2H4 adsorption ratio of 1.53 compared to unmodified UiO-67. GCMC simulations demonstrate that C2H6 forms more C-H···π interactions with the surrounding benzene rings and more C-H···C interactions with methyl groups compared to C2H4, highlighting the synergistic effects of supramolecular interactions. Furthermore, the hydrophobic pore environment also minimizes water interference, with exceptionally low water uptake (0.019 g g-1 at 60% RH), ensuring robust separation capacity under high humid conditions. The introduction of methyl groups not only significantly enhances C2H6 adsorption performance and C2H6/C2H4 separation selectivity but also improves material's hydrophobicity.

The Cu─O─Co Asymmetric Bimetallic Sites Constructed by Ion-Exchange for Efficient Oxygen Evolution Reaction

Recently, constructing oxygen-bridged asymmetric bimetallic sites has proven to be an effective strategy for enhancing electrocatalytic activity. The strong electronic interaction between the metals regulates the d-band center, optimizing the adsorption and desorption of oxygen intermediates and lowering the oxygen evolution reaction (OER) energy barrier. However, examples of constructing such asymmetric sites in π-d conductive metal-organic frameworks (cMOFs) are still scarce. Here, the Co/Cu-DBC (DBC = Dibenzo-[g,p]chrysene-2,3,6,7,10,11,14,15-octaol) with high crystallinity and asymmetric Cu─O─Co bimetallic sites are prepared using an ion-exchange method. By varying the reaction temperature and time, the metal content can be precisely controlled. The Co/Cu-DBC shows excellent OER activity, with a small overpotential of 251 mV at 10 mA cm-2. Both experimental and density functional theory (DFT) calculations indicate that the construction of asymmetric Cu─O─Co sites leads to strong electronic interactions between Cu and Co through the axial oxygen atom, which regulates the d-band center energy (Ed) level and electronic structure to optimize the adsorption of intermediates and facilitate the formation of *O intermediates on the active Co sites toward fast OER kinetics. This work provides new insights for the synthesis and the design of efficient OER catalysts.

Encapsulation of Metal Nanoparticles by Metal-Organic Framework Imaged with In Situ Liquid Phase Transmission Electron Microscopy

Metal nanoparticle@metal-organic framework (NP@MOF) composites hold promise for potential applications in gas storage, catalysis, sensing, environmental monitoring, and biomedicine. Despite their importance, details of how MOFs encapsulate the NPs to form NP@MOF hybrid nanostructures are largely unexplored. Here, using ultra-low electron-flux in situ liquid phase transmission electron microscopy (LP-TEM), the encapsulation of Au NPs with zeolitic imidazolate framework-8 (ZIF-8) is visualized. These observations reveal that the speeds at which MOFs nucleate on the NP's surface impact the shell's shape. At low concentrations of MOF precursor, NPs are encapsulated with well-defined single-crystalline MOF shells, while at high concentrations, MOFs tend to nucleate and grow from multiple sites on the NP surface, resulting in irregularly shaped polycrystalline MOF shells. This approach, which uses a very low electron flux to image the synthesis of Au@ZIF-8 nanostructures, can be extended to imaging crucial processes in many other beam-sensitive materials and help design hybrid systems for a broad range of applications.

Periodic Patterning of Matter in Non-Equilibrium Liesegang-Type Structures

Bottom-up self-organization of unordered molecules into ordered, spatiotemporal patterns of complex structures through non-equilibrium reaction-diffusion (RD) processes is ubiquitous in nature across all scales. Unlike many RD processes that typically lead to transient patterns, periodic precipitation reactions governed by the Liesegang phenomenon are distinguished by the formation of stable, permanent structures. This unique characteristic makes them valuable tools in the development of hierarchical multifunctional materials, an area that has seen significant progress in recent decades. This review summarizes the fundamental aspects of the Liesegang phenomenon, focusing on the key characteristics, compositional features, inherent properties, and formation mechanisms of Liesegang patterns in chemical systems, while also highlighting their occurrence in biological and geological settings. We discuss recent advancements in applying periodic precipitation to address global challenges in microelectronics and environmental monitoring, concluding with a forward-looking perspective on the promising future applications of the Liesegang periodic precipitation in materials science, nanotechnology, medicine, and environmental engineering.

Revisiting Photocatalytic CO2 Reduction to Methanol: A Perspective Focusing on Metal-Organic Frameworks

Photocatalytic CO2 reduction to CH3OH, particularly with metal-organic frameworks (MOFs) as photocatalysts, has garnered significant attention due to its long-term potential to harness sunlight for converting CO2 into a valuable fuel and chemical feedstock. Numerous studies in the literature report the successful formation of CH3OH from photocatalytic CO2 reduction, sometimes supplemented with sacrificial agents, with claims substantiated by isotopic labelling measurements. However, in this Scientific Perspective, we note that much of the existing evidence has not been obtained under sufficiently rigorous experimental conditions to conclusively confirm the formation of a highly reactive product like CH3OH from the chemically stable CO2 molecule. This Scientific Perspective outlines best practices designed to provide robust evidence for CH3OH formation in photocatalytic processes, which could be instrumental in clarifying the state-of-the-art and accelerating the development of this technology toward practical applications.

Luminescent Cd(II) Fumarate Bridging 1D Coordination Polymer: Ultra-Trace Level Detection of Cu2+ in Aqueous Medium and Fabrication of Semiconducting Device

In addressing the Sustainable Development Goals (SDGs) the UNDP has fixed 17 issues out of them clean water (SDG-6) and affordable energy (SDG-7) serve as decisive points towards sustenance of the society. Material chemistry plays a vital role to design new chemical compounds and exploring versatile activities towards the solution of pressing challenges. Copper, third abundant metal in human body following iron and zinc, is useful to monitor many metabolic processes. Exposure to high level Copper or its deficiency can cause various health issues. It is essential to determine quantity of Cu2+ in a wide range of consumables. A luminescent coordination polymer (LCP) of Cd2+(d10) as a metal node, fumaric acid (fuma2 -) as a linker and tripod N-coordinated 4'-Chloro-2,2',6',2"-terpyridine (4-Cltpy) as end-capping ligand, {[Cd(fuma)₂(4-Cltpy)].(H2O)}n (CP1), has been used in this research for trace quantity detection of Cu2+ in aqueous solution (LOD: 0.0307 μM (Cu(II)) (WHO recommended toxicity limit of Cu(II) is 3.15 μM). The band gap of CP1 (experimental value by Tauc's plot, 3.56 eV and theoretically calculated band gap, 3.54 eV) directs to fabricate Schottky semiconducting device (ITO/CP1/Al) which determines electrical conductivity, 4.52×10-4 Sm-1 at room temperature. Therefore, CP1 is a promising candidate as a conductive material and a sensor. Because of its dual purpose, CP1 may be very beneficial for device applications and a breakthrough in material science in near future.

Ni(II)-Directed Supramolecular Metallogel: Stimuli Responsiveness and Semiconducting Device Fabrication

Metal-organic gels (MOGs) are a type of supramolecular complex that have become highly intriguing due to their synergistic combination of inorganic and organic elements. We report the synthesis and characterization of a Ni-directed supramolecular gel using chiral amino acid L-DOPA (3,4-dihydroxy phenylalanine) containing ligand, which coordinates with Ni(II) to form metal-organic gels with exceptional properties. The functional Ni(II)-gel was synthesized by heating nickel(II) acetate hexahydrate and the L-DOPA containing ligand in DMSO at 70 °C. The rheological tests have verified the gel with its mechanical stability, while a SEM image has shown a spherical aggregate morphology. The gel is photo-responsive in nature and exhibits gel to sol transformation upon adsorption of toxic gases like NH3 or H2S. Notably, electrical conductivity of the gel was observed in electronic metal-semiconductor (MS) junctions' devices with a measured conductivity of 0.9×10-6 Sm-1. These devices also exhibited Schottky barrier diode characteristics, underscoring the multifunctional potential of the Ni(II)-gel.

A Copper(I) Catenane Decorated Metal-Organic Layer as a Heterogenous Catalyst for Dehydrogenative Cross-Coupling

While earth-abundant metals are green and sustainable alternatives to precious metals for catalytic chemical conversions, the fast ligand exchange involving most of the base metals renders their development into robust, reusable catalysts very challenging. Described in this work is a new type of heterogeneous catalyst derived from a 2D metal-organic layer (MOL) grafted with catenane-coordinated Cu(I) complexes. In addition to the good substrate accessibility, easy functionalization, and other favorable features due to the MOL support, the mechanical bond in the anchored catenane ligands also represents a new mechanism to dynamically confine the coordination environment and kinetically stabilize the coordinated Cu(I) to give a well-defined, active yet stable heterogeneous catalyst. Pilot catalytic studies using a model dehydrogenative C─O cross-coupling reaction showed that the Cu(I) catenane-grafted MOL led to exclusive formation of the C─O coupled product, whereas control catalysis using a similar Cu(I) catalyst supported by non-interlocked macrocyclic ligands was found to also give a C─C coupled by-product, whose formation was found to be mediated by the uncontrolled oxidation of the Cu(I) to Cu(II), highlighting the distinctive roles and untapped potential of the catenane coordination in developing base metal-derived catalysts for challenging catalytic conditions.

Robust MOF-Based Composite Solid-State Electrolyte Membrane for High-Performance Lithium-Metal Batteries

In this work, we construct a robust MOF-based flexible composite membrane based on PVDF-HFP, UIO-66, and ionic liquid (IL). Through their synergistic reinforcement effect, the obtained solid-state electrolytes can simultaneously achieve high ionic conductivity, good mechanical properties, and flame retardance. The abundant pores of the MOF are capable of loading IL, which not only builds continuous ion channels and facilitates the dissociation of Li+ but also balances the mechanical properties and electrochemical performance. Consequently, the as-prepared electrolyte membranes exhibit excellent ionic conductivity (5.55 × 10-4 S cm-1), high Li+ transference number (0.52), moderate electrochemical window (4.3 V), outstanding mechanical properties (tensile strength of 6.63 MPa and elongation of 232%), and good interfacial stability (stable Li plating/stripping behavior). Meanwhile, the assembled LiFePO4//Li battery exhibits an excellent rate capability and long cycle stability. This work demonstrates a realistic strategy for the fabrication of MOF-based composite SSEs toward next generation high-performance lithium metal batteries.

Unlocking coordination sites of metal-organic frameworks for high-density and accessible copper nanoparticles toward electrochemical nitrate reduction to ammonia

Ordered pore engineering of metal-organic framework (MOF)-based catalysts by soft-template strategies can facilitate the mass transfer of reactants during heterogeneous electrocatalysis. Besides, the abundant open coordination sites generated by the removal of surfactants also open up a new avenue for incorporating active moieties within the framework; however, such studies are still limited. Herein, a mesoporous cerium-based MOF, MUiO-66(Ce), is synthesized by introducing a pluronic triblock copolymer as a template, where abundant open coordination sites are found to be present on the hexa-cerium nodes. By providing rich Ce-OH/Ce-OH2 sites, plenty of copper moieties are installed on the framework (denoted as Cu-MUiO-66(Ce)). After the in situ reduction process, a high density of copper nanoparticles is confined within MUiO-66(Ce), and Cu@MUiO-66(Ce) is thus obtained. With a high loading of active copper sites and efficient diffusion of reactants, the Cu@MUiO-66(Ce)-modified electrode can achieve an ammonia production rate of 1.875 mg h-1 mgcatalyst -1 and a faradaic efficiency of 88.7% for nitrate-to-ammonia reduction. Findings here shed light on the importance of pore engineering of MOF-based catalysts for unlocking open coordination sites and facilitating the mass transfer to enhance the electrocatalytic activity.