Metal-organic Framework Materials Research Articles

Fabrication of abundant oxygen vacancies in MOF-derived (Fe,Co)3O4 for oxygen evolution reaction and as an air cathode for zinc-air batteries

Metal-organic frameworks (MOFs) find wide-ranging applications owing to their adjustable structures, diverse compositions, and large specific surface area. In this work, MOFs materials were grown in situ on carbon cloth, yielding self-supported electrodes VO-(Fe,Co)3O4@CC rich in oxygen vacancies through a simple high-temperature annealing treatment utilizing NaBH4 as an etchant. Thus the resulting self-supported electrode VO-(Fe,Co)3O4@CC exhibited excellent oxygen evolution reaction (OER) performance, achieving an overpotential of merely 288 mV at 10 mA cm−2, along with a low Tafel slope of 31.39 mV dec-1, and demonstrating robust long-term activity and stability. In addition, a liquid zinc-air battery was assembled utilizing the prepared VO-(Fe,Co)3O4@CC as an air cathode, achieving a high open-circuit voltage of 1.46 V and a high peak power density of 89.06 mW cm−2, and it maintained excellent cycling stability during cyclic charging and discharging (with a current density of 2 mA cm−2) over a 32 h period. Meanwhile, the self-supported electrode VO-(Fe,Co)3O4@CC served as an air cathode for assembling an all-solid-state flexible zinc-air battery (ZAB), demonstrating a high peak power density (38.21 mW cm−2) and exhibiting favorable cycling stability. This experiment offers insights into the potential application of MOF-derived electrocatalysts in water decomposition and zinc-air batteries.

Construction of MIL-100(Fe)-DMA material for efficient adsorption of Sr and Cs ions from radioactive wastewater

A novel metal-organic framework (MOF) material, MIL-100(Fe)-DMA, was synthesized using the solvothermal method. The structure of the MOF was characterized using scanning electron microscopy-energy dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. Batch adsorption experiments were performed to investigate the effects of initial Sr2+ and Cs+ concentrations, adsorption time, pH, and coexisting cations on the adsorption performance of the material. The adsorption mechanism was further elucidated using adsorption kinetics and isotherm models. The results indicated that the adsorption of Sr2+ and Cs+ does not significantly affect the MOF material structure. As reaction time and initial ion concentration increased, the adsorption capacity of MIL-100(Fe)-DMA for Sr2+ and Cs+ increased rapidly and then gradually reached equilibrium. Optimal adsorption occurred under alkaline conditions, with maximum adsorption capacity observed at pH = 8. The adsorption process for Sr2+ and Cs+ was well described by the pseudo-second-order kinetic model, the Weber–Morris model, and the Langmuir adsorption isothermal model. The adsorption process was mainly identified as monolayer chemical adsorption, influenced by multiple factors. Characterization combined with density functional theory calculations revealed that the unsaturated carboxylic acid groups on the surface of the MOFs play a crucial role in the interaction with Sr2+ and Cs+.

Aromatic pore engineering in microporous metal–organic frameworks for high-production one-step methane purification from ternary alkanes mixtures

The exploitation of competent isolation and purification technology of methane (CH4) is an imperative and challenging task for full utilization of clean natural gas in petrochemical industry. Compared to traditional energy-intensive low-temperature distillation, adsorptive separation using porous metal–organic framework (MOF) materials provides an alternative technique with low energy consumption and high efficiency. In this situation, an aromatic pore engineering strategy in a series of pillar-layered Zn-based MOFs by introducing organic linkers with different degrees of aromatic units was investigated to tune pore size and pore environment for simultaneously removing propane (C3H8) and ethane (C2H6) from C3H8/C2H6/CH4 mixtures. Compared to the other two analogues, i.e. Zn(BDC)(TED)0.5 and Zn(ADC)(TED)0.5, obtained Zn(NDC)(TED)0.5 showed high adsorption capacity for C3H8 (5.18 mmol/g) and C2H6 (5.04 mmol/g) and selectivity for C3H8/CH4 and C2H6/CH4 at 298 K and 1.0 bar. Breakthrough tests proved the three MOFs can effectively separate ternary C3H8/C2H6/CH4 mixtures, and Zn(NDC)(TED)0.5 especially exhibited excellent high-purity CH4 yield of 10.07 mmol/g. Computational simulations showed that suitable pore space and surface aromatic environment in Zn(NDC)(TED)0.5 created beneficial interactions with C3H8 and C2H6 molecules, which ultimately contributed to its favourable adsorption and separation property. This system work provides insights for the development of pore control method in MOF materials for natural gas purification.

Bifunctional In-MOFs for Selective and Sensitive Detection of Trace Nitrobenzene Compounds in Water and Possessing High Proton Conductivity.

With the escalating prevalence of terrorism and global environmental pollution, nitroaromatic compounds (NACs) have increasingly come into focus as the primary culprit. To counter these challenges, it is imperative to develop simple and efficient methods for detecting NACs. Considering the electron-deficient structure of NAC molecules, this paper constructed a novel three-dimensional In-MOF with permanent porosity using electron-rich organic molecules 4'-[1,2,2-tris(3',5'-dicarboxy[1,1'-biphenyl]-4-yl)ethenyl]-[1,1'-biphenyl]-3,5-dicarboxylic acid (H8ETTB) for fluorescence detection by photoinduced electron transfer. The results indicated that In-ETTB can sensitively detect trace NACs in water. In-ETTB exhibited the best detection performance for 3-NP, achieving a Ksv value of 8.75 × 104 M-1 with a limit of detection of 0.27 μΜ in aqueous solution; this belongs to a relatively high level among the reported metal organic framework (MOF) materials. Subsequently, anti-interference experiments revealed that In-ETTB exhibits strong specificity fluorescence recognition of NACs, and it could still maintain its structural integrity and fluorescence emission intensity even after 7 cycles of testing. We confirmed that the fluorescence detection of NACs was due to a combined effect of competitive absorption and photoinduced electron transfer through experimental collaboration DFT calculations in detail. Meanwhile, the proton conductivity reached 2.45 × 10-2 S·cm-1 at 98% relative humidity and 90 °C, which is also a high level in MOFs. This work provides a universal method theoretical basis for designing NAC detectors with practical application prospects.

Preparation of NH2-MIL-101(Fe) Metal Organic Framework and Its Performance in Adsorbing and Removing Tetracycline.

Tetracycline's accumulation in the environment poses threats to human health and the ecological balance, necessitating efficient and rapid removal methods. Novel porous metal-organic framework (MOF) materials have garnered significant attention in academia due to their distinctive characteristics. This paper focuses on studying the adsorption and removal performance of amino-modified MIL-101(Fe) materials towards tetracycline, along with their adsorption mechanisms. The main research objectives and conclusions are as follows: (1) NH2-MIL-101(Fe) MOF materials were successfully synthesized via the solvothermal method, confirmed through various characterization techniques including XRD, FT-IR, SEM, EDS, XPS, BET, and TGA. (2) NH2-MIL-101(Fe) exhibited a 40% enhancement in tetracycline adsorption performance compared to MIL-101(Fe), primarily through chemical adsorption following pseudo-second-order kinetics. The adsorption process conformed well to Freundlich isotherm models, indicating multilayer and heterogeneous adsorption characteristics. Thermodynamic analysis revealed the adsorption process as a spontaneous endothermic reaction. (3) An increased adsorbent dosage and temperature correspondingly improved NH2-MIL-101(Fe)'s adsorption efficiency, with optimal performance observed under neutral pH conditions. These findings provide new strategies for the effective removal of tetracycline from the environment, thus holding significant implications for environmental protection.

Sensitive detection of NH3 at room temperature at ppb level via facile ZIF calcination

This study introduces an innovative approach for preparing gas sensors involving the formation of metal oxides from metal–organic framework materials via a two-step calcination process. A gas-sensitive material capable of detecting NH3 at a concentration of 11 ppb at room temperature was developed using a simple and facile experimental method. Compared with materials produced in previous studies by one-step calcination, the C-doped ZnO developed in this study had a dispersed cubic porous morphology with a higher specific surface area and smaller pore size. During two-step calcination, urea acts as a structure-directing agent and increases the gas adsorption capacity of the final material. Additionally, the incorporation of urea slightly reduced the material's band gap. Further examinations confirmed the material's exceptional selectivity and long-term stability in detecting NH3, and response tests at 59 %, 75 %, and 85 % relative humidity indicated its tolerance to high-humidity environments. These outstanding characteristics suggest that the proposed fabrication method can produce metal-oxide materials with substantially enhanced gas-sensing performance.

Growth behavior of anisotropic monometallic MOFs derivatives with the high absorbing and thermal properties

The growth behavior and morphological characteristics of metal-organic frameworks (MOFs) should be considered as important factors in understanding their structure. Therefore, MOFs with atypical shapes, heterogeneous structures or abnormal properties that grow anisotropic can serve as components and templates for further directed assembly or conversion into MOF derivatives with excellent performance in electromagnetic wave absorption. Cobalt (Co) and nickel (Ni) metals have good magnetic properties and are common materials for the preparation of monometallic MOF-derived. In this study, various MOF materials with anisotropic properties, such as rod-like, flower-like, and braided, were prepared by adjusting the molar ratio of Co and Ni solvent to the organic ligand. Due to the rich inter-facial polarization and strong magnetic coupling network of the magnetic composites, Ni-MOF-b (Ni-MOF with braided shape) was prepared for the first time when the molar ratio of nickel nitrate to linker was 1:1.2. The Ni-C-b was obtained after pyrolysis of Ni-MOF-b, the minimum reflection loss of Ni-C-b was –50.7 dB at 4.0 mm. In addition, the thermal conductivity of the film prepared with Ni-C-b as filler is 2.2 W/mK. The film with integrated good heat dissipation and wave absorbing properties provides a research idea for the design of multifunctional integrated film.

Multimaterial Digital-Light Processing of Metal-Organic Framework (MOF) Composites: A Versatile Tool for the Rapid Microfabrication of MOF-Based Devices.

Patterning Metal-Organic Frameworks (MOFs) is essential for their use in sensing, electronics, photonics, and encryption technologies. However, current lithography methods are limited in their ability to pattern more than two MOFs, hindering the potential for creating advanced multifunctional surfaces. Additionally, balancing design flexibility, simplicity, and cost often results in compromises. This study addresses these challenges by combining Digital-Light Processing (DLP) with a capillary-assisted stop-flow system to enable multimaterial MOF patterning. It demonstrates the desktop fabrication of multiplexed arbitrary micropatterns across cm-scale areas while preserving the MOF's pore accessibility. The ink, consisting of a MOF crystal suspension in a low volatile solvent, a mixture of high molecular weight oligomers, and a photoinitiator, is confined by capillarity in the DLP projection area and quickly exchanged using syringe pumps. The versatility of this method is demonstrated by the direct printing of a ZIF-8-based luminescent oxygen sensor, a 5-component dynamic information concealment method, and a PCN-224-based colorimetric sensor for amines, covering disparate pore and analyte sizes. The multi-MOF capabilities, simplicity, and accessibility of this strategy pave the way for the facile exploration of MOF materials across a wide range of applications, with the potential to significantly accelerate the design-to-application cycle of MOF-based devices.

Enhancing Two-Photon Excited Fluorescence of Metal-Organic Framework Single Crystals through Modulation of Inorganic Nodes.

Regulation of the two-photon excited fluorescence (TPEF) emission intensity and wavelength of metal-organic framework (MOF) crystals with similar constitutions presents a significant challenge. In this study, two MOFs, Zn-BTPPA and Cd3-BTPPA, were constructed using tetrakis(1,1'-biphenyl-4-carboxylic acid)-1,4-benzenediamine (H4BTPPA) as the organic ligand and mononuclear Zn and trinuclear Cd3 inorganic nodes, respectively. The incorporation of H4BTPPA within the MOF structures enables effective TPEF emission in both Zn-BTPPA and Cd3-BTPPA. The TPEF results show that Zn-BTPPA and Cd3-BTPPA exhibited strong emissions at 523 and 463 nm, respectively, when excited with a 780 nm laser. Moreover, Zn-BTPPA and Cd3-BTPPA exhibited much higher two-photon absorption cross sections, approximately 4.9 and 5.2 times higher than that of the reported dinuclear MOF, Cd2-BTPPA, with a similar composition, respectively. With different inorganic nodes, the stacking of chromophores, π···π interactions, and ligand geometry were found to correlate with the enhanced TPEF in Cd3-BTPPA and the blue-shifted TPEF in Zn-BTPPA. This work serves as an inspiration for designing efficient TPEF MOF materials based on the structure-property relationship.

From Nanozymes to Multi-Purpose Nanomaterials: The Potential of Metal-Organic Frameworks for Proteomics Applications.

Metal-organic frameworks (MOFs) have the potential to revolutionize the biotechnological and medical landscapes due to their easily tunable crystalline porous structure. Herein, the study presents MOFs' potential impact on proteomics, unveiling the diverse roles MOFs can play to boost it. Although MOFs are excellent catalysts in other scientific disciplines, their role as catalysts in proteomics applications remains largely underexplored, despite protein cleavage being of crucial importance in proteomics protocols. Additionally, the study discusses evolving MOF materials that are tailored for proteomics, showcasing their structural diversity and functional advantages compared to other types of materials used for similar applications. MOFs can be developed to seamlessly integrate into proteomics workflows due to their tunable features, contributing to protein separation, peptide enrichment, and ionization for mass spectrometry. This review is meant as a guide to help bridge the gap between material scientists, engineers, and MOF chemists and on the other side researchers in biology or bioinformatics working in proteomics.

Biomedical Metal–Organic framework materials on antimicrobial therapy: Perspectives and challenges

As a barrier between the structure of the human body's internal organs and the outside environment, the skin serves crucial physiological tasks like protection, regulation, and metabolism. The skin's close interaction with the outside makes it particularly vulnerable to many injuries. Bacterial infections cause wound healing to take longer, raise the risk of chronic harm, and serve as a breeding ground for drug-resistant bacteria. As a result, it is critical to eliminate bacterial species from the wound region rapidly and efficiently. Metal-organic frameworks (MOFs), are critically adjustable hybrid materials that integrate organic ligands with coordination metals to generate a range of topologically isomorphic structures. MOFs' creation and shape are investigated by the metal source and ligand utilized in the reaction process, and the structural benefits of this near-infinite combination of structures allow boundless potential for their surface functionalization. MOF has a large effective surface area, tunable structure, adaptability, excellent biodegradability, high drug load, adjustable release of drugs, robust targeting, etc. It can be loaded with therapeutic materials and has programmability. It is more conducive to treating complex wounds while realizing the synergistic effects of antibacterial, anti-inflammatory, and pro-angiogenesis, effectively improving treatment safety. This review summarizes the most recent research advances on various MOFs for antimicrobial therapy, using diverse types of metal-ion-based MOFs as an entry point. Finally, it covers several important challenges in the antimicrobial treatment of metal-ion-based MOFs.

Enhanced peroxidase-like activity via Pt loading of Ni-MOF for colorimetric and smartphone-based bimodal determination of antioxidant capacity in aging cells

Total antioxidant capacity (TAC) serves as a vital indicator for evaluating cell senescence. Here, we synthesized a platinum-loaded nickel-based metal–organic framework material (Ni-MOF@Pt) via a solvothermal method for bimodal determination of TAC in aging cells. The Pt nanoparticle incorporation substantially enhanced the peroxidase-like catalytic activity of Ni-MOF. Ni-MOF@Pt exhibited a strong affinity for 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, with lower Km values compared to horseradish peroxidase (HRP). The Ni-MOF@Pt-TMB-H2O2 system was successfully applied for detecting antioxidants, including glutathione (GSH), ascorbic acid (AA), and cysteine (Cys) with impressive detection limits (121 nM for GSH, 119 nM for AA, 72 nM for Cys), highlighting the high sensitivity of this system. Additionally, a smartphone-assisted visual detection sensor was established using Ni-MOF@Pt for rapid, sensitive, and on-site TAC detection. Moreover, our established Ni-MOF@Pt method effectively determined the TAC of aging cells and demonstrated its ability to differentiate between normal, senescent, and cancerous cells. This research offers novel insight on fabricating nanozymes with potent peroxidase-like properties and manifests their practicality in TAC analysis.

Low-dose electron microscopy imaging for beam-sensitive metal-organic frameworks.

Metal-organic frameworks (MOFs) have garnered significant attention in recent years owing to their exceptional properties. Understanding the intricate relationship between the structure of a material and its properties is crucial for guiding the synthesis and application of these materials. (Scanning) Transmission electron microscopy (S)TEM imaging stands out as a powerful tool for structural characterization at the nanoscale, capable of detailing both periodic and aperiodic local structures. However, the high electron-beam sensitivity of MOFs presents substantial challenges in their structural characterization using (S)TEM. This paper summarizes the latest advancements in low-dose high-resolution (S)TEM imaging technology and its application in MOF material characterization. It covers aspects such as framework structure, defects, and surface and interface analysis, along with the distribution of guest molecules within MOFs. This review also discusses emerging technologies like electron ptychography and outlines several prospective research directions in this field.

Synthesis of a MOF derived porous graphene and pyrolytic carbon supported zinc stannate nanohybrid electrode with enhanced lithium-ion storage performances

Compositing nano-sized zinc stannate (Zn2SnO4) with supportive carbon skeleton usually brings in improved lithium-ion storage performances. One of the most challenging tasks is to effectively stabilize Zn2SnO4 nanocrystals via simplified preparation routes from eco-friendly raw materials. In this work, the water-soluble natural molecule gallic acid (GA) is directly employed to coordinate with Zn2+/Sn2+ ions, and the corresponding metal-organic framework (MOF) precursor samples of pure Zn-GA MOF and bimetallic ZnSn-GA MOF can be synthesized. The Zn-GA MOF and ZnSn-GA MOF precursors are further converted to a three-dimensional (3D) porous graphene sample (ZMG) and a pyrolytic carbon domain supported Zn2SnO4 nanocomposite (Zn2SnO4@C), respectively, by taking the advantages of the unique micro-structures and compositions of MOF materials. By rationally mixing the ZMG and Zn2SnO4@C in electrode fabrication, the finally obtained Zn2SnO4@C/ZMG nanohybrid electrode exhibits a high reversible capacity of 1117 mAh·g−1 after 500 cycles at a current density of 1000 mA g−1 in half-cells as well as inspiring full-cell performance. The favorable synergistic effect in lithium-ion storage for the Zn2SnO4@C/ZMG electrode has been investigated. The MOF derived samples and involved sustainable synthesis protocols can be further developed for wider applications.

Performance improvement photodetectors with high speed and detectivity using terbium-doped ZIF-8 and MOF-5 films

Crystal engineering is critical for improving the crystal quality and tuning the optoelectronic properties of metal-organic frameworks (MOFs) materials. Doping MOFs is one of the practical approaches to improve the optoelectronic properties of MOFs. Here, a simple and effective method is used to grow MOF nanoparticles as films on the surface of the material. MOF-5 and ZIF-8 nanoparticles can be uniformly grown as films on the Si substrates. The crystalline quality of MOF films is improved after doping with Tb. Meanwhile, two-dimensional conducting photodetectors and photodetector arrays were prepared with perovskite films. Meanwhile, planar conducting photodetector arrays were prepared with MOF films. The photoluminescence (PL) intensity of the Tb-ZIF-8 and Tb-MOF-5 films shows an improvement compared to both ZIF-8 and MOF-5 layers, which leads to improved charge carriers transfer. The maximum photocurrents were about 4 × 10−8 A and 3 × 10−8 A of exposed light at 525 and 425 nm, respectively, at a fixed bias of 10 V for Tb-ZIF-8. The highest photo response of approximately 2.4 × 10−7 and 1.2 × 10−7 A was measured under 525 and 450 nm for the Tb-MOF-5-based device, respectively. The photocurrent behavior is optimized in the visible range due to the increased number of photo-generated carriers at 525 nm. The Tb-MOF-5 based device is a more powerful photodetector than the Tb-ZIF-8 based device under the same conditions. In addition, the stability of Tb-MOF-5 and Tb-ZIF-8 based photodetectors was obtained 77 % and 30 %, respectively. The photodetectors of Tb-MOF-5 have higher stability and better performance than Tb-ZIF-8.

Nanozyme Decorated Metal-Organic Framework Nanosheet for Enhanced Photodynamic Therapy Against Hypoxic Tumor.

Photodynamic therapy (PDT) has attracted increasing attention in the clinical treatment of epidermal and luminal tumors. However, the PDT efficacy in practice is severely impeded by tumor hypoxia and the adverse factors associated with hydrophobic photosensitizers (PSs), including low delivery capacity, poor photoactivity and limited ROS diffusion. In this study, Pt nanozymes decorated two-dimensional (2D) porphyrin metal-organic framework (MOF) nanosheets (PMOF@HA) were fabricated and investigated to conquer the obstacles of PDT against hypoxic tumors. PMOF@HA was synthesized by the coordination of transition metal iron (Zr4+) and PS (TCPP), in situ generation of Pt nanozyme and surface modification with hyaluronic acid (HA). The abilities of hypoxic relief and ROS generation were evaluated by detecting the changes of O2 and 1O2 concentration. The cellular uptake was investigated using flow cytometry and confocal laser scanning microscopy. The SMMC-7721 cells and the subcutaneous tumor-bearing mice were used to demonstrate the PDT efficacy of PMOF@HA in vitro and in vivo, respectively. Benefiting from the 2D structure and inherent properties of MOF materials, the prepared PMOF@HA could not only serve as nano-PS with high PS loading but also ensure the rational distance between PS molecules to avoid aggregation-induced quenching, enhance the photosensitive activity and promote the rapid diffusion of generated radical oxide species (ROS). Meanwhile, Pt nanozymes with catalase-like activity effectively catalyzed intratumoral overproduced H2O2 into O2 to alleviate tumor hypoxia. Additionally, PMOF@HA, with the help of externally coated HA, significantly improved the stability and increased the cell uptake by CD44 overexpressed tumor cells to strengthen O2 self-supply and PDT efficacy. This study provided a new strategy of integrating 2D porphyrin MOF nanosheets with nanozymes to conquer the obstacles of PDT against hypoxic tumors.

UIO-66 (Zr)-Metal Organic Frameworks for oil orange SS adsorption from aqueous effluent towards eco-friendly wastewater management

Abstract Wastewater treatment is essential for efficient removal of harmful substances such as dyes and organic contaminants from aqueous streams. In this regard, metal-organic frameworks (MOFs) are introduced by academia owing to their superior properties that including efficient adsorbents as well as reliable semi-permeability. Thus, such characteristics are making them attractive for wastewater treatment applications. The experimental results revealed that the modified MOF structures namely, UIO-66 (Zr) possess a superior adsorption capacity for orange SS dye. The influence of pH value, the temperature, adsorption isotherm time, initial pollutant load, as well as coexisting ions is highlighted. Initially, 30-minutes of reaction contact time is monitored as the isotherm time. The experimental results demonstrate a maximum dye removal efficiency of 100% and an adsorption capacity of 2062.175 mg/g is investigated. Such outcomes confirm the efficient adsorption capacity of UIO-66 (Zr) based MOF material for dye elimination.

Electrospun metal-organic framework materials derived bimetallic oxides as high-efficiency anodes for lithium-ion battery

Energy devices are receiving more and more attention, and this is especially true for lithium-ion batteries. Moreover, applying novel nanostructures in multicomponent systems is a very effective way to promote the development of energy storage systems. This study synthesizes a nitrogen-doped carbon nanofiber encapsulating MOF-derived bimetallic oxide nanomaterial by combining electrospinning and MOF materials. Nitrogen-doped carbon nanofibers are porous and highly conductive, providing structural stability, a practical pathway for lithium ion diffusion, and an essential channel for rapid charge transfer during cycling. The bimetallic oxides derived from the MOF materials provide sufficient space for fast reaction sites and mitigate volume expansion during cycling. When the composite material FNO@NCNFs is used as the anode material for lithium batteries, its reversible capacity is maintained at 1105.4 mAh g−1 after 100 cycles at a current density of 0.1 A g−1. Its capacity reaches 748.5 mAh g−1 after 900 cycles at a current density of 1 A g−1, and at the same time, it exhibits excellent cycling stability, with the coulombic efficiency remaining above 98 %. The material also exhibits a small ion transfer resistance and good rate performance. The structural design approach based on combining MOFs with electrospinning in this study will provide new insights into the design and development of materials for advanced energy storage applications.

The detection of acetone in exhaled breath using gas Pre-Concentrator by modified Metal-Organic framework nanoparticles

Volatile organic compounds (VOCs) from exhaled breath are promising indicators for the diagnostics of human health conditions. However, the composition of breath is rather complex, including water vapors and various tiny amounts of gases and biomarkers. Pre-concentrator plays a significant role in capturing and concentrating target gas in the gas mixture. In this work, the MIL-101 (Cr) nanoparticles are coated with polydimethylsiloxane (PDMS) through physical vapor deposition process to concentrate acetone under high humidity and room temperature. Experimentally, the newly developed material exhibits significant improvement in signal intensity that is 76.3 times greater than a commercial reference material under relative humility of 80 %. The detection range is also proven to be desirable (from 100 ppb to 2500 ppb), capturing the spectrum of acetone concentrations typically found in human exhaled breath. Moreover, following a thermal desorption process, the device demonstrates a high degree of linearity with a coefficient of 0.9956. The modified metal–organic framework materials are made into a flexible thin-film-shape device, that could be embedded in a facemask. The proposed device could meet the critical requirements for sampling, concentrating and detecting of exhaled breath biomarkers, thereby opening a new opportunity as part of the flexible electronic systems on face masks to facilitate quantitative breath analyses.

Fabrication of metal‐organic frameworks macro-structures for adsorption applications in water treatment: A review

Metal-organic frameworks (MOFs) are emerging porous organic–inorganic hybrid materials composed of metal centers/clusters and various organic ligands, which are widely used in water and wastewater treatment applications due to their large specific surface area, high porosity, tunable chemical properties and abundant active sites. However, pure MOFs powders have limitations such as poor recovery, blocked pipelines and secondary contamination in practical water treatment processes. Enabling the magnetization of MOFs or immobilizing MOFs as macroscopic MOFs materials offers new opportunities to improve solid–liquid separation performances of powdered MOFs. Besides, macroscopic MOFs materials with outstanding adsorption performance and mechanical properties by the combining of 3D particles and 2D nanosheets MOFs with other substrates are widely used for water treatment. This paper provides a comprehensive review of recent advancements in MOFs macro-structures. We firstly summarized the synthesis strategies of magnetic MOFs composites and various MOFs macro-structures such as hydrogels/aerogels, membranes, beads/spheres, others composites, etc. which can be constructed by various methods, including in-situ growth, solvothermal method, direct mixing, self-assembly, layer-by-layer growth, etc. Innovative preparation strategies to improve the mechanical properties of MOFs macro-structures were highlighted. Next the article discusses its application for adsorptive removal of various pollutants (i.e., dyes, heavy metal ions, oils and organic pollutants) from water. Finally, the challenges of macroscopic MOFs materials and their practical applications are presented, while future research directions to overcome these existing limitations are also pointed out.