MOF Films Research Articles

Biosafe Cu-MOF loaded chitosan/gelatin-based multifunctional packaging film for monitoring shrimp freshness

As living standards improve, the demand for food freshness has gradually increased. Multifunctional packaging materials that monitor food freshness in real-time, delay spoilage, and are environmentally friendly have emerged as ideal solutions. This study synthesized an ammonia-sensitive copper-based metal-organic framework (Cu-MOF) and incorporated it into a matrix composed of chitosan (CS) and gelatin (Gel). The resulting film exhibits ammonia-sensitive color-changing properties, antibacterial activity, and excellent biodegradability. The effects of Cu-MOF incorporation on the structural, physical, and functional properties of the CS/Gel films were systematically evaluated. Results demonstrated that the Cu-MOF was uniformly distributed within the CS/Gel matrix, significantly enhancing the mechanical properties (tensile strength increased by 68.49%), oxygen/water vapor barrier properties, and UV-blocking capability of the films. Notably, the CS/Gel@Cu-MOF films exhibited excellent antibacterial performance, with sterilization rates of 94.2% against Escherichia coli and 99.6% against Staphylococcus aureus. Additionally, the films showed good biocompatibility, biodegradability, and a sensitive color response to ammonia. The films were successfully used to monitor shrimp freshness through color change, transitioning from light green to brown as spoilage occurred. These findings indicate that CS/Gel@Cu-MOF films have significant potential for real-time visual freshness monitoring in food packaging, contributing to reduced food safety risks and waste.

Three-dimensionally oriented organization of hexagonal MIL-96 microplates toward superior film microstructure

Preferential orientation control of MOF films is advantageous for maximizing pore uniformity and minimizing grain boundary defects. Nonetheless, the preparation of MOF films with both in-plane and out-of-plane orientations remains a grand challenge. In this study, we reported the preparation of three-dimensionally oriented MIL-96 layers through combining morphology control of MIL-96 seeds with addition of PVP surfactants and arachidonic acids. Three-dimensionally oriented MIL-96 film was readily obtained through in-plane epitaxial growth. It is anticipated that the above protocol can be effective for obtaining diverse MOF films with three-dimensionally oriented organization.

An Inhibitor-Loaded LDH- and MOF-Based Bilayer Hybrid System for Active Corrosion Protection of Aluminum Alloys.

A novel inhibitor-loaded bilayer hybrid system based on the LDH inner layer and MOF outer layer is designed on an aluminum alloy 2A12 surface to improve corrosion performance. The hybrid film system covers the inherent cavities and intercrystalline defects of the LDH film using the affinity between the LDH and the MOF compounds. The results demonstrate that the LDH-inhI precursor film is entirely covered by new Zn-based MOF microrods. The LDH-inhI precursor film is partially dissolved and recrystallized in favor of MOF crystal growth to strengthen the binding adhesion between LDH and MOF films. The LDH-inhI/MOF-inhII bilayer film shows significantly enhanced corrosion resistance through the synergistic action of LDH and MOF nanocontainers doped with different corrosion inhibitors (vanadates, 2,5-furandicarboxylic acid, and benzotriazoles). Due to the multiple loadings of the MOF film and the sustained-release of the LDH film, this method provides an effective approach to developing new anticorrosion systems and enhancing both the barrier ability and active corrosion protection performance of LDH-based conversion treatments.

Orthogonal stimulation of structural trans-formations in photo-responsive MOF films by linker functionalization

Controlling the magnitude of structural dynamics in flexible MOF films by an applied stimulus is largely desired for specific applications such as energy storage. Herein, by introducing chlorine substituents in...

Mixed-ligand based water-stable Mn(II)-MOF for quick, sensitive, and reusable IFE-PET-RET facilitated detection of formaldehyde and Cr(VI)-oxoanions in real-field samples like food and industrial water: experimental and theoretical insights.

We report the luminescence-based detection of Group-1 carcinogen formaldehyde (FA) and Cr(VI)-oxoanions with a mesoporous Mn(II)-MOF (1), featuring a uninodal 4-c net topology and linear 1D square channels forming a polymeric 2D network. The Mn-MOF i.e., [Mn(phen)(hia)(H2O)]∞ was solvothermally constructed using π-conjugated, chelating phenanthroline (phen) and µ3-η2:η1 binding 5-hydroxyisophthalic acid (hia) ligands. The 2D rod-like crystallites of 1 demonstrated excellent phase purity, high thermal and photostability, and robustness under harsh conditions. The SCXRD and XPS studies established the structural framework and elemental composition, while the Hirshfeld surface analysis and NCI-RDG plot confirmed the presence of π-π stacking and weak interactions in 1. We explored the bright-blue emission of 1 for recyclable and fast-responsive (∼70 s) 'turn-off' detection of FA, with a low limit of detection (LOD) of 8.49 µM. Based on this, a 04-input-03-output molecular logic gate was proposed, which can be useful as a molecular switch for future applications. Furthermore, a unique experimental setup using the MOF film demonstrated ∼57% quenching upon exposure to FA vapor (an indoor VOC). Additionally, 1 exemplified itself as an efficient probe towards Cr(VI)-oxyanions, depicting LODs of 79 and 170 ppb, Stern-Volmer constants (KSV) of 16.13 × 104 and 12.73 × 104 M-1, and response times of ∼48 and ∼40 s for CrO42- and Cr2O72-, respectively. DFT calculations and specific wet-chemical investigations elucidated the FA detection to be triggered by photo-induced electron transfer (PET), while the Cr(VI)-sensing involved a combination of PET, the inner-filter effect (IFE), resonance energy transfer (RET), and electrostatic H-bonding interactions. The FA detection was validated using food samples (fish and meat) and wastewater specimens, achieving excellent recovery rates of ∼92-95%. Furthermore, the MOF's efficacy in recognizing the Cr(VI)-species in complex matrices (coal mine wastewater, sewage, and tap water) was investigated to yield high KSV values (3.10-5.17 × 104 and 2.16-7.03 × 104 M-1 for CrO42- and Cr2O72-), which demonstrated the probe's consistency and reliability.

MOF based membranes in gas separation area

Microporous metal organic framework materials are a series of noticeable membrane materials for the separation of gas molecules and liquid molecules. MOFs can be functionalized through tuning pore size through the variation of ligand length, metal nodes and more, or through adjusting adsorption site such as functional sites, linker functional sites, and open metal sites. Membranes can provide higher structure stability for MOFs, however, addressing synthetic, processing, and design challenges is crucial to produce MOF films with excellent mechanical integrity, chemical stability, and high performance under relevant industrial conditions，such as interfacial compatibility issues towards Mixed-Matrix-Membranes (MMMs) and Pure-MOF film issues regarding chemical and thermal robustness, morphology, and orientation. The alkyne/alkene separation, alkane/alkene separation and more gas mixture has been proven can be achieved through the use of MOF-based membranes, moreover, compared to traditional methods, MOF-based membranes possess better performance on separating forementioned gas mixtures with higher selectivity, purity and less harm to the environment.

Metal–organic framework thin films: review of their room-temperature synthesis and applications

This review presents diverse growth methods employed in the fabrication of room temperature-synthesized MOF films, emphasizing their significant applications across various fields.

Enhanced carrier transport of monolayer MoSe2 through interlayer coupling with in situ grown metal-organic frameworks.

Exceptional interlayer coupling of organic-inorganic vdWHs is paramount for enhancing electron mobility. Herein, we report a novel transfer-free method to fabricate MoSe2/Ni3(HITP)2 vdWHs. The MOF film promotes interfacial charge transfer, leading to a threefold increase in electron mobility. This work provides a platform for developing high-performance optoelectronic devices.

A sunlight sensitive metal–organic framework film for the environment-friendly self-sterilization application

This work provides a sunlight sensitive MOF film with the unique advantage of easy and superfast preparation, and environmentally-friendly self-sterilization, offering a potential approach for the long-term usage of disposable protective equipment.

One-step electrodeposition of MWCNTs-Cu MOF films for the ratiometric electrochemical analysis of glyphosate.

Sensitive and accurate determination of glyphosate (GLYP) is vital for food safety and environmental protection. Herein, a novel electrochemical ratiometric biosensor was designed for the accurate quantification of GLYP through one-step electrodeposition of MWCNTs-Cu MOF films. MWCNTs-Cu MOF nanostructures were directly electro-synthesized in situ on the electrode from the precursor solution. The combination of Cu MOFs with MWCNTs not merely improved the conductivity of MOFs, but also enhanced the sensitivity of the biosensor. Furthermore, Cu sites within Cu MOFs were turned into CuCl to further amplify the current signal and enable the specific recognition of GLYP through competing reactions with the transformation of CuCl into non-electroactive Cu-GLYP. Meanwhile, internal reference molecules of methylene blue (MB) were incorporated to improve the measurement accuracy of GLYP for reducing unpredictable measurement errors aroused by environmental deviations. The ratiometric electrochemical sensor exhibited a high linearity with the logarithmic value of GLYP concentration from 0.5 nM to 400 nM. The detection limit was estimated to be as low as 0.014 nM. Finally, the present sensor with ratiometric signal export was applied for GLYP analysis in real samples with high sensitivity and accuracy. The simplicity and reliability of the ratiometric sensor make it a worthy and powerful tool for food and environmental monitoring. This design strategy also provides an avenue for the development of simple and efficient biosensors for other substances.

Zn-metal organic framework containing electron rich linkers and film preparation for applications in antibiotic detection

A Zn-metal organic framework has been synthesized, [Zn4(ad)3(BPTC)(H2O)4]·0.75ad ·0.25NO3·2.5DMF·2.5H2O (ZnAB MOF) (ad = adenine, BPTC = biphenyl-3,3′,5,5′-tetracarboxylic acid) and characterized by X-ray single crystallography. The crystal structure reveals a 3D framework with two differently sized channels with the structure confirmed by IR, TGA and elemental analysis. This MOF has also been prepared in the form of a MOF film on a Zn metal sheet in situ with one continuous layer 60 μm thick. The materials fluoresce at 352, 433 and 355, 423 nm (λex = 310 nm), for MOF powder and MOF film, respectively. The fluorescence is quenched by nitrofuran antibiotics allowing the MOF to be used in their detection. Specifically, the nitrofuran antibiotics nitrofurazone (NFZ) and nitrofurantoin (NFT) exhibit significant quenching. ZnAB MOF powder shows higher sensitivity than the ZnAB MOF film with higher fluorescence quenching, Stern-Volmer constant (KSV) and limit of detection (LOD). However, the ZnAB MOF film exhibits superior repeatability for nitrofuran detection. Fluorescence quenching of NFZ and NFT may occur via fluorescence resonance energy transfer (FRET) and/or photoinduced electron transfer (PET).

Recent Advances in Lanthanide Metal–Organic Framework Thin Films Based on Eu, Tb, Gd: Preparation and Application as Luminescent Sensors and Light-Emitting Devices

Lanthanide Metal–Organic Frameworks (LnMOFs), in recent years, have developed into an interesting subclass of MOFs. While the number of published papers, in particular, were dedicated to their synthesis and functional properties, along with the application mechanisms of MOFs, only a few of them have been focused on LnMOFs thin films independently. LnMOFs have become interesting thanks to their outstanding properties, for example, excellent structural flexibility, tunable pore size, surface area, functionality, and good chemical stability. Significant progress over the past two decades in the preparation of MOF films has been achieved, especially towards the development of green, or at least greener, synthesis approaches. We begin with insight into various types of MOFs and summarize recent achievements in the production of LnMOF films, along with various film preparation approaches. Afterward, we briefly discuss the applications of luminescence features of lanthanide ions in films and their potential as white-light source materials. We also covered films based on Eu, Tb, and Gd with particular accents on different design approaches. Moreover, specifically, luminescent features applied for sensing temperature, a variety of ions, gases, and biomolecules are highlighted. The review ends with a comprehensive conclusion about the state-of-art-potential of LnMOFs together with an outlook on the future of LnMOF films in future technologies.

Zeolite imidazolate framework composite membranes prepared on amine/tannic acid cross-linked polymeric hollow fiber substrates for enhanced gas separation

In this work, a continuous dense zeolite imidazolate framework (ZIF) composite membranes for enhanced gas separation were successfully prepared on diethylenetriamine (DETA) and tannic acid (TA) cross-linked polymeric hollow fiber substrates via the in-situ solvothermal method for the first time. With strong reactivity and small molecular volume, DETA connected various TA molecules and anchored TA molecules on the organic hollow fiber substrate to form a relatively tight spatial network. The modified polyvinylidene fluoride(PVDF) support contained abundant phenolic hydroxyl, carbonyl, and amine groups, providing a large number of active sites for heterogeneous nucleation and promoting the forming of continuous and non-defect MOF film. The synergistic effect between TA and DETA not only enhanced the stiffness and durability of the MOF composite membrane, but also improved the performance of membrane on gas separation. The morphology of the amine/TA modified to support and the MOFs composite membrane was analyzed by SEM, XRD, FTIR, XPS, etc. The fabricated TA-DETA-PVDF/ZIF-8 composite membrane with a continuously dense layer and unique structural stability displayed excellent H2 permeance of 1.01 × 10-7 mol·m−2 s−1 Pa−1 and competitive H2/N2 and H2/CH4 selectivity of 24.0 and 24.4, respectively.

Self-Powered Infrared Photodetectors with Ultra-High Speed and Detectivity Based on Amorphous Cu-Based MOF Films.

Amorphous metal-organic frameworks (aMOFs) start to challenge their crystalline equivalents due to their unique advantages, like lack of grain boundaries, isotropy, flexibility, numerous defects-induced active sites, etc. However, aMOFs are typically synthesized under rigorous conditions, and their properties and applications need to be further explored. In this work, highly transparent p-type amorphous Cu-HHTP films consisting of Cu2+ and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) were synthesized using a simple electrostatic spinning method and identified as p-a-Cu-HHTP. Besides, a p-a-Cu-HHTP/n-Si infrared photodetector (PD) operating on a self-powered basis with ultra-high speed (response time of 40 μs) and detectivity (1.2 × 1012 Jones) has been developed, with a response time and detectivity that are record values for a MOF-based photodetector. In particular, the p-a-Cu-HHTP/n-Si PD can withstand high temperatures up to 180 °C without property change. Moreover, a flexible metal-semiconductor-metal photodetector based on p-a-Cu-HHTP is constructed, which shows excellent mechanical stability and photoresponse that remain unchanged after bending 120 times, implying its suitability for wearable optoelectronics. The new method to fabricate aMOFs, the unique p-a-Cu-HHTP, and its PDs initiated in this work opens up a new avenue in organic-inorganic hybrid optoelectronics.

Hierarchical conductive metal-organic framework films enabling efficient interfacial mass transfer

Heterogeneous reactions associated with porous solid films are ubiquitous and play an important role in both nature and industrial processes. However, due to the no-slip boundary condition in pressure-driven flows, the interfacial mass transfer between the porous solid surface and the environment is largely limited to slow molecular diffusion, which severely hinders the enhancement of heterogeneous reaction kinetics. Herein, we report a hierarchical-structure-accelerated interfacial dynamic strategy to improve interfacial gas transfer on hierarchical conductive metal-organic framework (c-MOF) films. Hierarchical c-MOF films are synthesized via the in-situ transformation of insulating MOF film precursors using π-conjugated ligands and comprise both a nanoporous shell and hollow inner voids. The introduction of hollow structures in the c-MOF films enables an increase of gas permeability, thus enhancing the motion velocity of gas molecules toward the c-MOF film surface, which is more than 8.0-fold higher than that of bulk-type film. The c-MOF film-based chemiresistive sensor exhibits a faster response towards ammonia than other reported chemiresistive ammonia sensors at room temperature and a response speed 10 times faster than that of the bulk-type film.

Crystallization of NiCo MOF-74 on a Porous NiO Film as an Anode for the Urea/H2O2 Fuel Cell

NiCo-MOF-74 crystallized directly on the surface of porous NiO (p-NiO) film using a solvothermal method is proposed as an effective electrocatalyst for the anode in direct urea fuel cells. A nickel-to-cobalt ratio of 4:1 was found to show optimum catalytic activity toward urea oxidation with significant current enhancement in comparison to other electrodes, including Ni foil and p-NiO. At optimized conditions in an electrolyte solution of 3.0 M KOH and 1.0 M urea, a current density of around 110 mA cm–2 with a maximum power density of 4131 μW cm–2 can be produced. This is ascribed to the increase of the active surface area over conventional nickel-based anodes, providing an abundance of active sites for urea oxidation. Excellent stability and reproducibility over 15 h application in a direct urea fuel cell was obtained with cell voltage of ∼0.6 V. Powder X-ray diffraction shows the crystalline MOF film remains intact after chronoamperometry tests, and after fuel cell application, illustrating applicability in real devices.

Cathodic deposition of MOF films: mechanism and applications.

Metal-organic framework (MOF) thin films could be used for ion/molecular sieving, sensing, catalysis, and energy storage, but thus far no large-scale applications are known. One of the reasons is the lack of convenient and controllable fabrication methods. This work reviews the cathodic deposition of MOF films, which has advantages (e.g., simple operations, mild conditions, and controllable MOF film thickness/morphology) over other reported techniques. Accordingly, we discuss the mechanism of the cathodic deposition of MOF films which consists of the electrochemically triggered deprotonation of organic linkers and the formation of inorganic building blocks. Thereafter, the main applications of cathodically deposited MOF films are introduced with the aim of showing this technique's wide-ranging applications. Finally, we give the remaining issues and outlooks of the cathodic deposition of MOF films to drive its future development.

Correction: Surprisingly fast assembly of the MOF film for synergetic antibacterial phototherapeutics

Correction for ‘Surprisingly fast assembly of the MOF film for synergetic antibacterial phototherapeutics’ by Jie Gao, et al., Green Chem., 2022, 24, 5930–5940, https://doi.org/10.1039/D2GC00226D.

Ultrathin Metal-Organic Framework Nanosheets Exhibiting Exceptional Catalytic Activity.

Two-dimensional (2D) metal-organic framework nanosheets (MONs) or membranes are classes of periodic, crystalline polymeric materials that may show unprecedented physicochemical properties due to their modular structures, high surface areas, and high aspect ratios. Yet preparing 2D MONs from multiple components and two different types of polymerization reaction remains challenging and less explored. Here, we report the synthesis of MOF films via interfacial polymerization, which involves three active monomers for simultaneous polycondensation and polycoordination taking place in a confined interface. The well-defined lamellar structure of the MOF films allowed feasible and scalable exfoliation to produce free-standing 2D MONs with high aspect ratio up to 2000:1 and ultrathin thickness (∼1.7 nm). The pore structure was revealed by high-resolution TEM images with near-atomic precision. The imide-linkage of MONs provided superior thermal (up to 530 °C) and good chemical stability in the pH range from 3 to 12. More importantly, the MONs exhibited exceptional catalytic activity and superior reusability for the hydroboration reactions of alkynes, in which the turnover frequency (TOF) reached 41734 h-1, which is 2-4 orders of magnitude greater than that reported for homogeneous and heterogeneous catalysts.

One-Step Reductive Electrodeposition of MOF Film on Polymer Membrane

One-Step Reductive Electrodeposition of MOF Film on Polymer Membrane