Metal-organic Frameworks Research Articles

Portable foodborne pathogen detection via ratiometric fluorescence nanoprobe for adenosine triphosphate quantification based on DNA-functionalized metal-organic framework.

The increasing incidence of foodborne illnesses highlights the need for rapid, sensitive, and portable methods to detect pathogenic bacteria in food. In this work, we develop a portable method that utilizes a ratiometric fluorescence nanoprobe for adenosine triphosphate (ATP) quantification. The nanoprobe is constructed by encapsulating Ru(bpy)32+ within a zirconium-based metal-organic framework, followed by functionalization of double-stranded DNA (dsDNA). This design permits SYBR Green I (SGI) to intercalate into dsDNA, conferring the nanoprobe with dual-emission property. The presence of ATP disrupts dsDNA structure, quenching SGI fluorescence while maintaining Ru(bpy)32+ fluorescence, providing a stable reference signal. This differential response enables the nanoprobe to achieve ratiometric ATP detection with high precision and sensitivity, with a detection limit of 0.63 μM. Since ATP is a reliable biomarker for viable bacterial cells, a portable hydrogel kit was further developed by integrating the ratiometric fluorescence nanoprobe into an agarose hydrogel matrix. The validation of the kit was conducted using a smartphone application for color recognition, enabling the rapid and on-site detection of pathogens in milk samples. The kit exhibits exceptional sensitivity with a detection limit of 10 CFU/mL, making it a promising tool for real-time bacteria detection in food safety monitoring.

Energy-Level Alignment at TiO2@NH2-MIL-125 Interface for High-Performance Gas Sensing.

Metal oxide (MO)-based chemiresistive sensors have great potential in environmental monitoring, security protection, and disease diagnosis. However, the thermally activated sensing mechanism in pristine MOs leads to high working temperature and poor selectivity, which are the main challenges impeding practical applications. Precise modulation of the band structure at the heterojunction interfaces of MOs offers the opportunity to unlock unique electrical and optical properties, enabling us to overcome these challenges. Metal-organic frameworks (MOFs) with tunable structures are promising materials for aligning the energy levels at the heterojunctions of MOs. Herein, we report the energy-level structural engineering of MO@MOF heterojunctions to optimize chemiresistive sensing performance. The interface was flexibly modulated from a straddling gap to a staggered gap by -NH2 functionalization of TiO2@(NH2)x-MIL-125, varying x from 0 to 1 and 2, respectively. TiO2@(NH2)x-MIL-125 combines the advantages of MOs and MOFs to synergistically improve gas-sensing properties. As a result, TiO2@NH2-MIL-125 is the first light-activated material to detect NO2 at 1 ppb with a response time of < 0.3 min at room temperature. It also exhibited excellent selectivity and long-term stability. Our study underscores the potential of energy band engineering in creating high-performance sensors, offering a strategy to overcome current material limits.

Removal of Trace Benzene from Cyclohexane Using a MOF Molecular Sieve.

Cyclohexane (Cy), commonly produced by the catalytic hydrogenation of benzene (Bz), is used in large quantities as a solvent or feedstock for nylon polymers. Removing trace unreacted Bz from the Cy product is technically difficult due to their similar molecular structures and physical properties. Herein, we report that a metal-organic framework (MOF) adsorbent shows a molecular sieving effect for Bz and Cy with record-high Bz/Cy adsorption selectivities (216, 723, and 1027) in their liquid mixtures (v/v = 1:1, 1:10, and 1:20), and traps Bz molecules effectively even at low partial pressure in the vapor phase (e.g., 2.49 mmol/g at 8.2 Pa) or at low content in liquid-phase Cy (e.g., 128 mg/g at 20 ppm). Over 99% removal of trace Bz (1000 ppm) from liquid Cy could be achieved in one simple stripping step at room temperature using this sorbent, producing a Cy with >99.999% purity. Single-crystal structure analyses for guest-free and Bz-loaded phases of the MOF disclosed that a narrow slit-like pore aperture and the strong uniting of multiple weak host-guest and guest-guest interactions are the co-origin of its distinct adsorption property for Bz and Cy.

Self-Similar Ligand for 2D Zr(IV)-Based Metal-Organic Frameworks: Fluorescent Sensing and Catalysis.

Two-dimensional (2D) metal-organic framework sheets, in comparison to the 3D analogues, offer potential advantages for intercalation of guest components between the layers, exfoliation/dispersion into solutions, and processing into thin films. As a versatile platform for leveraging organic functions, the 2D Zr(IV)-carboxylate net here features a dendritic Sierpinski tritopic linker with conjugated alkyne branches and a photoactive triphenylamine core. The 2D solid can be easily dispersed in water and many other solvents, resulting in stable and fluorescent suspension for sensing nitro aromatic compounds and Fe3+ ions with high quenching efficiencies and ultralow limits of detection. Also, the neighboring alkyne units of the coordination solid undergo thermal cyclization (e.g., at 320 °C) to form cross-linked nanographene-like components to afford robust porosity, which substantially takes up PdCl2 (atomic ratio of Zr/Pd, 2.4:1) to afford a heterogeneous catalyst for Suzuki-Miyaura coupling reactions─direct in air and without the need for phosphine ligands.

Peptide-Induced Hydrogelation with Ordered Metal-Organic Framework Nanoparticles Generating Reactive Oxygen Species for Integrated Wound Repair.

Hydrogels, with their high water content and flexible nature, are a promising class of medical dressings for combating bacterial wound infections. However, their development has been hindered by low sterilization efficiency. Here, this issue is addressed by designing a peptide hydrogel that assembles ordered metal-organic framework (MOF) nanoparticles with photocatalytic bactericidal activity. Specifically, a short peptide, Nap-Gly-Phe-Phe-His (Nap-GFFH), is used to induce the assembly of zinc-imidazolate MOF (ZIF-8) into a hydrogel (NHZ gel). This innovative structure integrates three key features: 1) ZIF-8 nanoparticles are encapsulated within the hydrogel, overcoming their inherent brittleness, insolubility, and limited moldability; 2) the ordered ZIF-8 structure enhances charge transfer, enabling efficient generation of reactive oxygen species (ROS); and 3) ZIF-8 simultaneously improves the photocatalytic bactericidal efficiency and mechanical properties of the hydrogel. The NHZ gel demonstrates remarkable antibacterial performance, achieving >99.9% and 99.99% inactivation of Escherichia coli and Staphylococcus aureus, respectively, within 15 min of simulated solar radiation. Additionally, the NHZ gel exhibits excellent biocompatibility, water retention, and exudate absorption, highlighting its broad potential for wound healing.

Nitrogen-Rich Conjugated Macrocycles: Synthesis, Conductivity, and Application in Electrochemical CO2 Capture.

Here we report a series of nitrogen-rich conjugated macrocycles that mimic the structure and function of semiconducting 2D metal-organic and covalent organic frameworks while providing greater solution processability and surface tunability. Using a new tetraaminotriphenylene building block that is compatible with both coordination chemistry and dynamic covalent chemistry reactions, we have synthesized two distinct macrocyclic cores containing Ni-N and phenazine-based linkages, respectively. The fully conjugated macrocycle cores support strong interlayer stacking and accessible nanochannels. For the metal-organic macrocycles, good out-of-plane charge transport is preserved, with pressed pellet conductivities of 10-3 S/cm for the nickel variants. Finally, using electrochemically mediated CO2 capture as an example, we illustrate how colloidal phenazine-based organic macrocycles improve electrical contact and active site electrochemical accessibility relative to bulk covalent organic framework powders. Together, these results highlight how simple macrocycles can enable new synthetic directions as well as new applications by combining the properties of crystalline porous frameworks, the processability of nanomaterials, and the precision of molecular synthesis.

Synthesis and characterization of a composite featuring metal–organic frameworks, titania nanoparticles, and graphene oxide: a dual evaluation as a photocatalyst and electrochemical sensing platform

Synthesis and characterization of a composite featuring metal–organic frameworks, titania nanoparticles, and graphene oxide: a dual evaluation as a photocatalyst and electrochemical sensing platform

Water adsorption within PIM-1 polymer and CAU-23 MOF material from osmotic molecular dynamics simulations

Abstract In the context of post-combustion carbon dioxide capture, the existence of the Metal-Organic Framework (MOF) transparency effect, which can enhance carbon dioxide uptake under humid conditions, was recently demonstrated. It is, therefore, essential to first determine the water adsorption capacity within the MOF. In this work, the CAU-23 MOF material, which appears to possess the main chemical and structural characteristics necessary for MOF transparency to occur, was considered. In addition, Mixed Matrix Membrane (MMM) is now considered on an industrial scale for shaping purposes. Among polymers, the intrinsically microporous polymer PIM-1 has shown interesting adhesion properties with MOF surfaces. Thus, before investigating what happens within the MMM, we aim to examine the water adsorption within the bulk CAU-23 and PIM-1 materials using the recently developed osmotic molecular dynamics simulations. These preliminary results show that CAU-23 could be a promising material for enhancing the MOF’s transparency and increasing $$\hbox {CO}_2$$ CO 2 uptake. Graphic abstract

Metal‐Organic Frameworks for Advanced Electrochemical Ammonia Production in Water

AbstractSustainable ammonia synthesis, a key focus in electrochemistry, has seen significant advancements with the emergence of Metal‐Organic Frameworks (MOFs). This review provides a comprehensive analysis of the recent strides in MOF‐based materials for green ammonia production, reflecting the urgency to develop eco‐friendly and energy‐efficient chemical commodities. It explores the reaction mechanisms, emphasizing the importance of structure‐performance relationships in MOF optimization and the design of MOF‐based electrocatalysts, including metal node engineering and hybrid materials. The review also highlights in‐situ characterization techniques that are crucial for understanding MOF catalytic activity. It establishes a correlation between MOF features, synthesis methods, and material performance, showcasing their potential in catalysis. Finally, it identifies challenges and future directions for MOFs in green ammonia production, aiming to inspire innovation towards sustainable and economically viable processes.

A Flexible Metal‐Organic Framework for the Removal of Propyne from Propylene

AbstractEfficient removal of propyne impurities from propylene is essential for producing high‐purity propylene. In this study, we utilize the flexible metal‐organic frameworks (MOFs) material, MOF‐508, for C3H4/C3H6 separation. Propyne (C3H4) induces a “Gate‐opening” effect in MOF‐508, transitioning it from a narrow‐pore phase to a large‐pore phase at low pressure. In contrast, propylene (C3H6) only triggers this effect at a higher pressure of 0.55 bar. Notably, at 298 K and 0.5 bar, MOF‐508 adsorbs 71.9 cm3/g of C3H4, compared to just 7.9 cm3/g of C3H6. This selective adsorption significantly enhances C3H4/C3H6 separation (50/50, v/v), as further demonstrated by dynamic breakthrough experiments.

Self‐adaptive Coordination Evolution Mediated Pore‐Space‐Partition in Metal–Organic Frameworks for Boosting SF6/N2 Separation

AbstractThe controllable and precise structural regulation of metal–organic frameworks (MOFs) based on isoreticular chemistry is an effective strategy for creating functional material platforms, such as efficient porous adsorbents. Herein, for the first time, mediated by an unprecedented self‐adaptive coordination evolution (SACE) on pseudo‐D2h‐symmetric [M4(μ3‐O)2(COO)6] (M=Mn/Fe) clusters, two pore space partitioned MOFs (CTGU‐47‐Mn/Fe, CTGU=China Three Gorges University) have been successfully constructed. Owing to the more confined adsorption space and dense binding sites produced by pore space partitioning (PSP), the CTGU‐47‐Mn/Fe exhibit significantly enhanced performance in the capture or recovery SF6 (greenhouse/electronic specialty gas) from SF6/N2 mixture compared to their non‐partitioned homologous structures (CTGU‐46‐Mn/Fe) with adsorption selectivity increased from 37/72 to 634/157 (v/v, 10/90, 100 kPa). The theoretical calculations also elucidated that the implementation of PSP within CTGU‐47‐Mn/Fe leads to dramatically strengthened binding affinity for SF6 over N2 through extra multiple F⋅⋅⋅H interactions. This study represents a valuable advance in crystal engineering field: the SACE of polynuclear metal clusters is expected to be useful in the structural regulation of MOFs and the fabrication of advanced porous adsorbents.

Co-In Bimetallic Hydroxide Nanosheet Arrays With Coexisting Hydroxyl and Metal Vacancies Anchored on Rod-Like MOF Template for Enhanced Photocatalytic CO2 Reduction.

Layered double hydroxides (LDHs) can serves as catalysts for CO2 photocatalytic reduction (CO2PR). However, the conventionally synthesized LDHs undergo undesired aggregation, which results in an insufficient number of active sites and limits the desirable electron transfer required for CO2PR. The metal-organic framework (MOF) template-grown LDHs demonstrate excellent promise for exploiting the strengths of both MOFs and LDHs. Herein, the in situ growth of MIL-68(In)-NH2 MOF-templated Co-In bimetallic catalyst (CoIn-LDH/MOF) having an ultrathin nanosheet morphology on the preserved rod-like MOF template is demonstrated. Compared to the conventionally grown bimetallic LDH (CoIn-LDH), CoIn-LDH/MOF not only exposes more active sites but also possesses hydroxyl vacancies (VOH) and Co vacancies (VCo). Thus, CoIn-LDH/MOF performs a higher CO generation rate of 2320µmol g-1 h-1 during CO2PR, demonstrating improved activity and selectivity than those in CoIn-LDH. Experiments coupled with calculations reveal that the CoIn-LDH/MOF-driven CO2PR follows the *COOH pathway. The lower energy barriers for the formation of *COOH and CO(g) can be attributed to the coexistence of VOH and VCo in CoIn-LDH/MOF, effectively promoting charge transfer and enhancing CO2PR performance. This study provides a new strategy to obtain high-performant LDH-based catalysts with improved morphology.

Core‐Shell Upconversion Nanoparticle@Metal–Organic Framework Fluorescent Nanoprobes for the Detection of Ferric Ions and Ferrous Ions

AbstractIn this study, we report a core‐shell fluorescent nanoprobe consisting of upconversion nanoparticles (UCNPs) NaGdF4 : Yb3+, Er3+ and metal‐organic frameworks (MOFs) ZIF‐8. ZIF‐8 can specifically bind to ferric ions (Fe3+) to change the ultraviolet‐visible absorption spectrum of the probe, as a result the fluorescence of the probe was quenched and achieve the detection of Fe3+. At the same time, since rhodamine B (RhB) can quench the fluorescence of this probe, by introducing ferrous ions (Fe2+) and hydrogen peroxide, based on Fenton reaction, the fluorescence signal of this probe can be recovered after the degradation of RhB, so it also can be used to detect Fe2+. Importantly, as the first report of UCNP@MOF probes for detecting Fe3+ and Fe2+, respectively, this method exhibits a good selectivity and anti‐interference capability. Finally, it was used to detect Fe3+ and Fe2+ in the serum with excellent recoveries.

Imidazole Encapsulation Enabled by Confinement for I2 and CH3I Coremoval.

Nitrogen-rich small molecules are frequently doped into porous materials to enhance their iodine adsorption properties. To explore how imidazole confinement in metal-organic frameworks (MOFs) affects iodine adsorption, we obtained a UiO-66-based composite by embedding imidazole in UiO-66 pores via solid-phase adsorption (Im@UiO-66). Characterization confirmed that imidazole was successfully confined within the UiO-66 pores, with each unit of UiO-66 accommodating up to 27 imidazole molecules. The density functional theory (DFT) calculations suggested that the octahedral cages of UiO-66 are the primary sites for iodine capture. The adsorption studies revealed that Im@UiO-66 achieved maximum adsorption capacities for I2 and CH3I that were 12 and 7.9 times higher than those of UiO-66, respectively, reaching 6.42 g/g for I2 and 553 mg/g for CH3I. The spectroscopic analysis indicated that Im@UiO-66 absorbed iodine vapor and methyl iodide via charge-transfer interactions and N-methylation reactions. This study demonstrates that imidazole confinement can effectively enhance the adsorption performance of MOF-based materials, offering valuable insights for the design of iodine adsorbents.

Heterojunction Nanozyme Hydrogels Containing Cu-O-Zn Bonds with Strong Charge Transfer for Accelerated Diabetic Wound Healing.

The complex microenvironment of persistent inflammation and bacterial infection is a major challenge in chronic diabetic wounds. The development of nanozymes capable of efficiently scavenging reactive oxygen species (ROS) is a promising method to promote diabetic wound healing. However, many nanozymes show rather limited antioxidant activity and ROS-dependent antibacterial effects under certain circumstances, further weakening their ability to scavenge ROS. To meet these challenges, electronically regulated bioheterojunction (E-bio-HJ) nanozyme hydrogels derived from metal-organic frameworks (MOFs) were designed and prepared via an interface engineering strategy. Owing to the electron transfer and redistribution effects of the abundant and highly dispersed Cu-O-Zn sites at the heterogeneous interface, the E-bio-HJ nanozymes exhibited catalase (CAT)-like activity with ultrahigh hydrogen peroxide affinity (Km = 25.76 mM) and sustained ROS consumption. In addition, owing to the enhanced interfacial effect of E-bio-HJ and the good biocompatibility and cell adhesion of the methacryloylated gelatin (Gel) hydrogel, the E-bio-HJ gelatin hydrogel (E-bio-HJ/Gel) further reduced inflammation by inducing macrophage transformation to the M2 phenotype, accompanied by excellent antimicrobial properties and enhanced cell migration, angiogenesis, and collagen deposition, which synergistically promoted diabetic wound healing. This highly effective and comprehensive strategy offers a new approach for the rapid healing of diabetic wounds.

An Adaptive Metal-Organic Framework Discriminates Xylene Isomers by Shape-Responsive Deformation.

The separation of xylene isomers, especially para-xylene, is a crucial but challenging process in the chemical industry due to their similar molecular dimensions. Here, a flexible metal-organic framework, Ni(ina)2, (ina = isonicotinic acid) is employed to effectively discriminate xylene isomers. The adsorbent with adaptive deformation accommodates the shapes of isomer molecules, thereby translating their subtle shape differences into characteristic framework deformation energies. Through a combination of multiple local flexibility behaviors, Ni(ina)2 exhibits guest-specific structural transformations that energetically favor para-xylene over other isomers. Single-crystal X-ray diffraction, in situ powder X-ray diffraction, and theoretical investigations validate this "adaptive fitting" mechanism, where the degree of structural deformation scales with the mismatch between the molecular shape and pore geometry. As a result, Ni(ina)2 achieves exceptional para-xylene selectivity in both liquid and vapor phase separations, maintaining a high para-xylene purity and productivity. This work demonstrates a novel strategy of exploiting framework flexibility to address challenging molecular separations and provides fresh insights into the design of selective adsorbents.

Lab-on-Fiber Operando Deciphering of a MOF Electrocatalyst.

Despite the great success in deploying metal-organic frameworks (MOFs) as efficient electrocatalysts, the low adoption of operando methods hinders the understanding of underlying mechanism. By leveraging the subtle refractive index evolution, including both the real and the imaginary parts, an entirely new concept of a lab-on-fiber operando method and its feasibility for "pristine-immersion-operando-post analysis" of electrocatalyts are demonstrated. Concurrent collection of absorption spectra and surface plasmon resonance is achieved by engineering fiber-optic waveguidesto simultaneously induce guided light attenuation and plasmonic coupling. In situ-formed Co hydroxide and oxide reactive intermediates in zeolitic imidazolate framework-67 (ZIF-67) electrocatalyst are optically identified, whichshows its underlying self-reconstruction conversions at different stages during electrocatalytic oxygen evolution reactions, and address the gap in knowledge concerning whether ZIF-67 is a precatalyst for real catalyst production. This illuminating operando method offers intriguing opportunities to collect all the observables in a single fiber, provides an exciting potential of a new class of device with long-sought integration and miniaturization capability, and is expected to enable the electrocatalysis community to conquer challenges with conducting multimodal operando experiments outside the laboratory.

Divergent Adsorption Regulation in Metal-Organic Frameworks for Highly Efficient CF4/C2F6 Separation.

The efficient removal of low-concentration components from homologous mixtures is often hampered by the co-directional effect of traditional thermodynamic regulation approaches, typically leading to a trade-off between adsorption capacity and selectivity. Focusing this challenge on the critical task of purifying perfluorocarbons in electronics industry, a divergent regulation strategy is reported that significantly improves the separation efficiency of low-concentration hexafluoroethane (C2F6) from tetrafluoromethane (CF4). This approach involves the selective shielding of open metal sites and the modulation of channel geometry within an electron-deficient ligand-based pore environment, thereby facilitating a C2F6 dense-packing accommodation mode while weakening the CF4 affinity due to the reduced host-guest interactions. Simultaneously enhanced C2F6 adsorption and reduced CF4 adsorption are achieved, resulting in record-high low-pressure C2F6 uptake and C2F6/CF4 selectivity. Comprehensive insights into the unique separation mechanism are illustrated through a combination of solid-state MAS nuclear magnetic resonance(SSNMR), molecular simulations, and meticulously designed comparative experiments. As a result, benchmark C2F6/CF4 separation performance is achieved, as demonstrated by the unprecedented electronic-grade (over 99.999%) CF4 productivity (401 L kg-1) obtained from an industrially relevant C2F6/CF4 (3:97) mixture, as well as the excellent water/air/heat stability and recyclability.

In Situ Synthesis of Iron-Based Porphyrin Metal-Organic Frameworks for the Baeyer-Villiger Oxidation Using Air as an Oxidant.

Iron-based porphyrin metal-organic frameworks (PMOFs) are a new type of material with good stability, catalytic activities, and reusability, which have broad application prospects. However, the synthesis of iron-based PMOFs with different metalloporphyrin units requires a considerable amount of reagents and time. Herein, an in situ synthesis method was developed to simplify the synthetic process of iron-based PMOFs. A series of highly stable iron-based PMOFs (Msitu-PMOF-3(Fe) (M = Fe, Co, Ni, Cu, Pd)) were synthesized in one pot without the preparation of metalloporphyrin ligands in advance. This synthesis method is simpler and more efficient, saving considerable time and material costs. The resultant Msitu-PMOF-3(Fe) exhibits a high tolerance to aqueous solutions with pH ranging from 0 to 11, as well as various organic solvents. The catalytic experiments show that both Fesitu-PMOF-3(Fe) and Cositu-PMOF-3(Fe) can catalyze the Baeyer-Villiger oxidation of cyclohexanone using air as an oxidant at 35 °C. Moreover, when the mixtures of Fesitu-PMOF-3(Fe) and Cositu-PMOF-3(Fe) were employed as catalyst, they can exert a cooperative catalysis effect, resulting in a significantly enhanced catalytic activity compared to a single component. The mild reaction condition, high catalytic efficiency, and excellent selectivity endow this catalytic system with a good application prospect. This work not only provides a new approach for the synthesis of iron-based PMOFs but also offers guidance for the Baeyer-Villiger oxidation reactions using air under mild conditions.

Economically Scalable Cu-based MOFs: Vital Role of Structural Integrity towards Selectivity on Azeotropic Ethanol Dehydration.

A facile, green, and economical method for the scalable synthesis of hydrophilic copper-triazole metal-organic frameworks (Cu-trz) is demonstrated. Numerous open metal sites within the highly crystalline porous structure of Cu-trz are generated through mild thermal activation, enabling its application in liquid-phase ethanol dehydration under ambient conditions. The frameworks with distinct crystallinity and particle sizes were achieved by modifying the synthesis process. The high crystallinity of the framework plays an exclusive role in enhancing water adsorption capacity. With selective water adsorption comparable to commercial zeolite 3A, Cu-trz MOF emerges as a promising candidate for cost-effective water-ethanol separation.