Deep learning and big data mining for Metal-Organic frameworks with high performance for simultaneous desulfurization and carbon capture

Carbon capture and desulfurization of flue gases are crucial for the achievement of carbon neutrality and sustainable development. In this work, the "one-step" adsorption technology with high-performance metal-organic frameworks (MOFs) was proposed to simultaneously capture the SO2 and CO2. Four machine learning algorithms were used to predict the performance indicators (NCO2+SO2, SCO2+SO2/N2, and TSN) of MOFs, with Multi-Layer Perceptron Regression (MLPR) showing better performance (R2 = 0.93). To address sparse data of MOF chemical descriptors, we introduced the Deep Factorization Machines (DeepFM) model, outperforming MLPR with a higher R2 of 0.95. Then, sensitivity analysis was employed to find that the adsorption heat and porosity were the key factors for SO2 and CO2 capture performance of MOF, while the influence of open alkali metal sites also stood out. Furthermore, we established a kinetic model to batch simulate the breakthrough curves of TOP 1000 MOFs to investigate their dynamic adsorption separation performance for SO2/CO2/N2. The TOP 20 MOFs screened by the dynamic performance highly overlap with those screened by the static performance, with 76 % containing open alkali metal sites. This integrated approach of computational screening, machine learning, and dynamic analysis significantly advances the development of efficient MOF adsorbents for flue gas treatment.

Calcium-based MOFs as scaffolds for shielding immobilized lipase and enhancing its stability

The enzyme immobilization technology has become a key tool in the field of enzyme applications; however, improving the activity recovery and stability of the immobilized enzymes is still challenging. Herein, we employed a magnetic carboxymethyl cellulose (MCMC) nanocomposite modified with ionic liquids (ILs) for covalent immobilization of lipase, and used Ca-based metal-organic frameworks (MOFs) as the support skeleton and protective layer for immobilized enzymes. The ILs contained long side chains (eight CH2 units), which not only enhanced the hydrophobicity of the carrier and its hydrophobic interaction with the enzymes, but also provided a certain buffering effect when the enzyme molecules were subjected to compression. Compared to free lipase, the obtained CaBPDC@PPL-IL-MCMC exhibited higher specific activity and enhanced stability. In addition, the biocatalyst could be easily separated using a magnetic field, which is beneficial for its reusability. After 10 cycles, the residual activity of CaBPDC@PPL-IL-MCMC could reach up to 86.9%. These features highlight the good application prospects of the present immobilization method.

Accelerating Oxygen Electrocatalysis Kinetics on Metal-Organic Frameworks via Bond Length Optimization

Metal-organic frameworks (MOFs) have been developed as an ideal platform for exploration of the relationship between intrinsic structure and catalytic activity, but the limited catalytic activity and stability has hampered their practical use in water splitting. Herein, we develop a bond length adjustment strategy for optimizing naphthalene-based MOFs that synthesized by acid etching Co-naphthalenedicarboxylic acid-based MOFs (donated as AE-CoNDA) to serve as efficient catalyst for water splitting. AE-CoNDA exhibits a low overpotential of 260 mV to reach 10 mA cm-2 and a small Tafel slope of 62 mV dec-1 with excellent stability over 100 h. After integrated AE-CoNDA onto BiVO4, photocurrent density of 4.3 mA cm-2 is achieved at 1.23 V. Experimental investigations demonstrate that the stretched Co-O bond length was found to optimize the orbitals hybridization of Co 3d and O 2p, which accounts for the fast kinetics and high activity. Theoretical calculations reveal that the stretched Co-O bond length strengthens the adsorption of oxygen-contained intermediates at the Co active sites for highly efficient water splitting.

DNA-functionalized MOF fluorescent probes for the enzyme-free and pretreatment-free detection of MicroRNA in serum

MicroRNA (miRNA) is a promising biomarker that plays an important role in various biomedical applications, especially in cancer diagnosis. However, the current miRNA detection technology has inherent limitations such as complex operation, expensive testing cost and excessive detection time. In this study, a dual signal amplification biosensor based on DNA-functionalized metal-organic frameworks (MOFs) fluorescent probes, MFPBiosensor, was established for the enzyme-free and pretreatment-free detection of the colon cancer (CC) marker miR-23a. DNA-functionalized MOFs NH2-MIL-53(Al) (DNA@MOFs) were synthesized as fluorescent probes with specific recognition functions. A single DNA@MOF carries a large number of fluorescent ligands 2-aminoterephthalic acid (NH2-H2BDC), which can generate strong fluorescence signals after alkaline hydrolysis. Combined with catalyzed hairpin assembly (CHA), an efficient isothermal amplification technique, the dual signal enhancement strategy reduced matrix interference and sensitized the signal response. The established MFPBiosensor successfully detected extremely low levels of miRNA in complex biological samples with acceptable sensitivity and specificity. With a single detection cost of $0.583 and a test time of 50 min, the excellent inexpensive and rapid advantage of the MFPBiosensor is highlighted. More importantly, the subtle design enables the MFPBiosensor to achieve convenient batch detection, where miRNA in serum can be directly detected without any pretreatment process or enzyme. In conclusion, MFPBiosensor is a promising biosensor with substantial potential for commercial miRNA detection and clinical diagnostic applications of CC.

A metal-organic framework and quantum dot-based ratiometric fluorescent probe for the detection of formaldehyde in food

A green and sensitive ratio fluorescence strategy was proposed for the detection of formaldehyde (FA) in food based on a kind of metal-organic frameworks (MOFs), MIL-53(Fe)-NO2, and nitrogen-doped Ti3C2 MXene quantum dots (N-Ti3C2 MQDs) with a blue fluorescence at 450 nm. As a type of MOFs with oxidase-like activity, MIL-53(Fe)-NO2 can catalyze o-phenylenediamine (OPD) into yellow fluorescent product 2,3-diaminophenazine (DAP) with a fluorescent emission at 560 nm. DAP has the ability to suppress the blue light of N-Ti3C2 MQDs due to inner filter effect (IFE). Nevertheless, Schiff base reaction can occur between FA and OPD, inhibiting DAP production. This results in a weakening of the IFE which reverses the original fluorescence color and intensity of DAP and N-Ti3C2 MQDs. So, the ratio of fluorescence intensity detected at respective 450 nm and 560 nm was designed as the readout signal to detect FA in food. The linear range of FA detection was 1-200 µM, with a limit of detection of 0.49 µM. The method developed was successfully used to detect FA in food with satisfactory results. It indicates that MIL-53(Fe)-NO2, OPD, and N-Ti3C2 MQDs (MON) system constructed by integrating the mimics enzyme, enzyme substrate, and fluorescent quantum dots has potential application for FA detection in practical samples.

Multifunctional MOF@COF Nanoparticles Mediated Perovskite Films Management Toward Sustainable Perovskite Solar Cells

Although covalent organic frameworks (COFs) with high π-conjugation have recently exhibited great prospects in perovskite solar cells (PSCs), their further application in PSCs is still hindered by face-to-face stacking and aggregation issues. Herein, metal-organic framework (MOF-808) is selected as an ideal platform for the in situ homogeneous growth of a COF to construct a core-shell MOF@COF nanoparticle, which could effectively inhibit COF stacking and aggregation. The synergistic intrinsic mechanisms induced by the MOF@COF nanoparticles for reinforcing intrinsic stability and mitigating lead leakage in PSCs have been explored. The complementary utilization of π-conjugated skeletons and nanopores could optimize the crystallization of large-grained perovskite films and eliminate defects. The resulting PSCs achieve an impressive power conversion efficiency of 23.61% with superior open circuit voltage (1.20 V) and maintained approximately 90% of the original power conversion efficiency after 2000 h (30-50% RH and 25-30 °C). Benefiting from the synergistic effects of the in situ chemical fixation and adsorption abilities of the MOF@COF nanoparticles, the amount of lead leakage from unpackaged PSCs soaked in water (< 5 ppm) satisfies the laboratory assessment required for the Resource Conservation and Recovery Act Regulation.

Ultrathin photonic crystal based on photo-crosslinked polymer and metal-organic framework for highly sensitive detection and discrimination of benzene series vapors

Volatile organic compounds (VOCs) have always been a major concern as a global environmental problem. As a low-cost, high-efficiency and visual sensor, photonic crystals (PCs) have been actively studied in VOCs detection. Herein, a one-dimensional PC sensor for visual sensing of highly toxic benzene series VOC vapors is prepared for the first time by integrating a new photo-crosslinked polymer-poly(styrene-benzoylphenyl acrylate) P(St-BPA) and a high specific surface area metal-organic framework (MOF) MIL-101(Cr). The PC can detect VOCs quantitatively and visually, and clearly distinguish 7 benzene series vapors. The detection limit of the benzene series VOCs is as low as 0.06-3.45 g/m3. Meanwhile, owing to the ultra-thin layer and porous structure, the PC can reach a response equilibrium to the VOCs within 1-2.6 s. Moreover, the PC has a good organic vapor tolerance and can maintain stable optical performance after 1000 times of reuse in VOCs. Besides, 4 other PCs assembled with different aryl polymers and MOFs are first fabricated and their sensing performance to benzene series VOCs are studied and compared, which provides a valuable reference for the selection of materials for the preparation of such PC sensors.

Hollow Metal-Organic Framework/MXene/Nanocellulose Composite Films for Giga/Terahertz Electromagnetic Shielding and Photothermal Conversion

With the continuous advancement of communication technology, the escalating demand for electromagnetic shielding interference (EMI) materials with multifunctional and wideband EMI performance has become urgent. Controlling the electrical and magnetic components and designing the EMI material structure have attracted extensive interest, but remain a huge challenge. Herein, we reported the alternating electromagnetic structure composite films composed of hollow metal-organic frameworks/layered MXene/nanocellulose (HMN) by alternating vacuum-assisted filtration process. The HMN composite films exhibit excellent EMI shielding effectiveness performance in the GHz frequency (66.8 dB at Ka-band) and THz frequency (114.6 dB at 0.1-4.0 THz). Besides, the HMN composite films also exhibit a high reflection loss of 39.7 dB at 0.7 THz with an effective absorption bandwidth up to 2.1 THz. Moreover, HMN composite films show remarkable photothermal conversion performance, which can reach 104.6 °C under 2.0 Sun and 235.4 °C under 0.8 W cm-2, respectively. The unique micro- and macro-structural design structures will absorb more incident electromagnetic waves via interfacial polarization/multiple scattering and produce more heat energy via the local surface plasmon resonance effect. These features make the HMN composite film a promising candidate for advanced EMI devices for future 6G communication and the protection of electronic equipment in cold environments.

Electrochemical sensing platform for detection of heavy metal ions without electrochemical signal

Heavy metal pollution has attracted global attention because of its high toxicity, non-biodegradability, and carcinogenicity. Electrochemical sensors are extensively employed for the detection of low concentrations of heavy metal ions (HMIs). However, their applicability is often limited to the detection of ions that exhibit electrochemical signals exclusively in aqueous solutions. In this study, we proposed a multi-responsive detection platform based on the modification of horseradish peroxidase@zeolitic imidazolate frameworks-8/thionine/gold/ionic liquid-reduced graphene oxide (HRP@ZIF-8/THI/Au/IL-rGO). This platform demonstrated its capability to detect various metal ions, including those without conventional electrochemical signals. The Au/IL-rGO composite structure enhanced the specific surface area available for the reaction. Furthermore, the in situ growth of HRP@ZIF-8 not only shielded the THI signal prior to detection but also protected the electrode material. It was important to note that the introduced edetate disodium dihydrate (EDTA) had the ability to complex with various HMIs. When excess EDTA was present, it could cleave ZIF-8 and release HRP. In the presence of hydrogen peroxide (H2O2), HRP promoted the oxidation of THI previously reduced by the electrode and thus showed excellent sensitivity for HMIs detection. The proposed method overcame the limitation of traditional electrochemical sensors, which solely relied on electrochemical signals for detecting metal ions. This offers a novel approach to enhance electrochemical ion sensing detection.

Building synergistic multiple active sites in branch-leaf nanostructured carbon nanofiber derived from MOF/COF hybrid for flexible wearable Zn-air battery

Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) have attracted growing attention in electrochemical energy storage and conversion systems (e.g., Zn-air batteries, ZABs) owing to their structural tunability, ordered porosity and high specific surface area. In this work, for the first time, the three-dimensional (3D) highly open catalyst (CNFs/CoZn-MOF@COF) possessing hierarchical porous structure and high-density active sites of uniform cobalt (Co) nanoparticles and metal-Nx (M-Nx, M = Co and Zn) is demonstrated, which is fabricated using electrospinning technique in combination with MOF/COF hybridization strategy and direct pyrolysis. Benefiting from the well-designed branch-leaf nanostructures, plentiful and uniform active sites on the MOF/COF-derived carbon frameworks, as well as the synergistic effect of multiple active sites, CNFs/CoZn-MOF@COF catalyst achieves superior electrocatalytic activity and stability towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a small potential gap (ΔE = 0.75 V). In situ Raman spectroscopy and X-ray photoelectron spectroscopy results indicate that the CoOOH intermediates are the main active species during OER/ORR. Significantly, both aqueous and all-solid-state rechargeable ZABs assembled with CNFs/CoZn-MOF@COF as the air cathode show high open-circuit potential, outstanding peak power density, large capacity and long cycle life. More impressively, the obtained all-solid-state ZAB also displays superb mechanical flexibility and device stability under different, showcasing great application deformations potential in portable and wearable electronics. This work provides a new insight into the design and exploitation of bifunctional catalysts from MOF/COF hybrid materials for energy storage and conversion devices.

A Three-Dimensionally Extended Metal-Organic Ladder Compound Exhibiting Proton Conduction

Ladder systems situated in the dimensional crossover region have attracted much attention because their electronic states and physical properties depend strongly on the electronic correlations among the constituent legs. Generally, two-/three-legged transition metal-oxide ladder compounds are studied as representative ladder systems, but two-/three-dimensional (2D/3D) extensions based on such ladder systems with a few numbers of legs are difficult because of the extreme synthesis conditions. Here, for the first time, we report the successful creation of a 3D extended two-legged ladder compound, [Pt(en)(dpye)I]2(NO3)4 ⋅ 2H2O (en=ethylenediamine; dpye=1,2-Di(4-pyridyl)ethane), which is obtained by simple oxidative polymerization of a small Pt macrocyclic complex using elemental I2. The unique 3D extended lattice consists of 1D mixed-valence halogen-bridged metal chains (⋅⋅⋅Pt-I-Pt-I⋅⋅⋅) and helically arranged macrocyclic units as the constituent legs and rungs, as confirmed by single-crystal X-ray diffraction. Diffuse X-ray scattering analyses and optical measurements revealed that the out-of-phase mixed-valence Pt2+/Pt4+ arrangement arises from the weak interchain correlation among adjacent legs. In addition, this compound shows an increase in proton conductivity by a factor of up to 1000, depending on humidity.

Ultrafine Ru nanoparticles stabilized by V8C7/C for enhanced hydrogen evolution reaction at all pH

The development of cost-effective electrocatalysts with high efficiency and long durability for hydrogen evolution reaction (HER) remains a great challenge in the field of water splitting. Herein, we design an ultrafine and highly dispersed Ru nanoparticles stabilized on porous V8C7/C matrix via pyrolysis of the metal-organic frameworks V-BDC (BDC: 1,4-benzenedicarboxylate). The obtained Ru-V8C7/C composite exhibits excellent HER performance in all pH ranges. At the overpotential of 40 mV, its mass activity is about 1.9, 4.1 and 9.4 times higher than that of commercial Pt/C in acidic, neutral and alkaline media, respectively. Meanwhile, Ru-V8C7/C shows the remarkably high stability in all pH ranges which, in particular, can maintain the current density of 10 mA cm-2 for over 150 h in 1.0 mol L-1 phosphate buffer saline (PBS). This outstanding HER performance can be attributed to the high intrinsic activity of Ru species and their strong interface interactions to the V8C7/C substrate. The synergistic effect of abundant active sites on the surface and the formed Ru-C-V units at the interface promotes the adsorption of reaction intermediates and the release of active sites, contributing the fast HER kinetics. This work provides a reference for developing versatile and robust HER catalysts by surface and interface regulation for pH tolerance.

Exploring the Gamma-Ray Enhanced NIR-Luminescence and Cytotoxic Potential of Lanthanide-Naphthalene Dicarboxylate based Metal-Organic Frameworks

In this investigation, we explore the integration of lanthanides into Metal-Organic Frameworks (MOFs) to enable Near-Infrared (NIR) emission. Specifically, we focus on Lanthanide-Naphthalene Dicarboxylate based MOFs (Ln-MOFs), incorporating elements such as Praseodymium (Pr), Samarium (Sm), Dysprosium (Dy), and Erbium (Er). The synthesis of Ln-MOFs is achieved via the hydrothermal method. The structure, morphology, thermal stability, and luminescence properties of synthesized Ln-MOFs have been evaluated through different characterization techniques. Upon photoexcitation at 350 nm, Ln-MOFs show the emission in the Visible and NIR region. Further, the luminescence intensity of Ln-MOFs enhanced by 2-3 folds in the visible region and 6-8 folds in NIR region after exposing to Gamma irradiation at 150 kGy. Cytotoxic effect on the viability of MDA-MB 231 and MDA-MB 468 Triple negative breast cancer (TNBC) cells was evaluated by MTT assay. The results revealed that among all synthesized MOFs, Pr-MOF exhibited an aggressive cytotoxic effect. Additionally, analysis of phase-contrast microscopy data indicates that Pr-MOF induces alterations in the morphology of both MDA-MB 231 and MDA-MB 468 TNBC cells when compared to untreated controls. The findings in this study reveal the utilization of Ln-MOFs for studying cytotoxicity and highlight their ability to enhance near-infrared (NIR) emission when exposed to gamma radiation.

Challenges and Opportunities in Preserving Key Structural Features of 3D-Printed Metal/Covalent Organic Framework

Metal-organic framework (MOF) and covalent organic framework (COF) are a huge group of advanced porous materials exhibiting attractive and tunable microstructural features, such as large surface area, tunable pore size, and functional surfaces, which have significant values in various application areas. The emerging 3D printing technology further provides MOF and COFs (M/COFs) with higher designability of their macrostructure and demonstrates large achievements in their performance by shaping them into advanced 3D monoliths. However, the currently available 3D printing M/COFs strategy faces a major challenge of severe destruction of M/COFs' microstructural features, both during and after 3D printing. It is envisioned that preserving the microstructure of M/COFs in the 3D-printed monolith will bring a great improvement to the related applications. In this overview, the 3D-printed M/COFs are categorized into M/COF-mixed monoliths and M/COF-covered monoliths. Their differences in the properties, applications, and current research states are discussed. The up-to-date advancements in paste/scaffold composition and printing/covering methods to preserve the superior M/COF microstructure during 3D printing are further discussed for the two types of 3D-printed M/COF. Throughout the analysis of the current states of 3D-printed M/COFs, the expected future research direction to achieve a highly preserved microstructure in the 3D monolith is proposed.

Control of the Hydroquinone/Benzoquinone Redox State in High-Mobility Semiconducting Conjugated Coordination Polymers

Conjugated coordination polymers (c-CPs) are unique organic-inorganic hybrid semiconductors with intrinsically high electrical conductivity and excellent charge carrier mobility. However, it remains a challenge in tailoring electronic structures, due to the lack of clear guidelines. Here, we develop a strategy wherein controlling the redox state of hydroquinone/benzoquinone (HQ/BQ) ligands allows for the modulation of the electronic structure of c-CPs while maintaining the structural topology. The redox-state control is achieved by reacting the ligand TTHQ (TTHQ=1,2,4,5-tetrathiolhydroquinone) with silver acetate and silver nitrate, yielding Ag4TTHQ and Ag4TTBQ (TTBQ=1,2,4,5-tetrathiolbenzoquinone), respectively. In spite of sharing the same topology consisting of a two-dimensional Ag-S network and HQ/BQ layer, they exhibit different band gaps (1.5 eV for Ag4TTHQ and 0.5 eV for Ag4TTBQ) and conductivities (0.4 S/cm for Ag4TTHQ and 10 S/cm for Ag4TTBQ). DFT calculations reveal that these differences arise from the ligand oxidation state inhibiting energy band formation near the Fermi level in Ag4TTHQ. Consequently, Ag4TTHQ displays a high Seebeck coefficient of 330 μV/K and a power factor of 10 μW/m ⋅ K2, surpassing Ag4TTBQ and the other reported silver-based c-CPs. Furthermore, terahertz spectroscopy demonstrates high charge mobilities exceeding 130 cm2/V ⋅ s in both Ag4TTHQ and Ag4TTBQ.

Hierarchically porous amino-functionalized nanoMOF network anchored phosphomolybdic acid for oxidative desulfurization and shaping application

The applications of hierarchically porous metal-organic frameworks (HP-MOFs) against traditional microporous counterparts for oxidative desulfurization (ODS) have triggered wide research interests due to their highly exposed accessible active sites and fast mass transfer of substrate molecules, particularly for the large-sized refractory sulfur compounds. Herein, a series of hierarchically porous amino-functionalized Zr-MOFs (HP-UiO-66-NH2-X) network with controllable mesopore sizes (3.5-9.2 nm) were firstly prepared through a template-free method, which were further utilized as anchoring support to bind the active phosphomolybdic acid (PMA) via the strong host-guest interaction to catalyze the ODS reaction. Benefitting from the hierarchically porous structure, accessible active sites and the strong host-guest interaction, the resultant PMA/HP-UiO-66-NH2-X exhibited excellent ODS performance, of which, the PMA/HP-UiO-66-NH2-9 with an appropriate mesopore size (4.0 nm) showed the highest catalytic activity, achieving a 99.9% removal of dibenzothiophene (DBT) within 60 min at 50 °C, far exceeding the microporous sample and PMA/HP-UiO-66. Furthermore, the scavenger experiments confirmed that •OH radical was the main reactive species and the density functional theory (DFT) calculations revealed that electron transfer (from amino group to PMA) made PMA react more easily with oxidant, thereby generating more •OH radical to promote the ODS reaction. Finally, from the industrial point of view, the powdered MOF nanoparticles (NPs) were in situ grown on the carboxymethyl cellulose (CMC) substrates and shaped into monolithic MOF-based catalysts, which still exhibited satisfying ODS performance in the case of model real fuel with good reusability, indicating its potential industrial application prospect.

Cobalt sulfide flower-like derived from metal organic frameworks on nickel foam as an electrode for fabrication of asymmetric supercapacitors

Metal-organic frameworks, as a kind of advanced nanoporous materials with metal centers and organic linkers, have been applied as promising electrode materials in energy storage devices. In this study, we are successfully prepared cobalt sulfide nanosheets (CoS) derived from the metal-organic framework on nickel foam (NF). The prepared electrodes are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda and electrochemical methods like voltammetry, galvanostatic charge-discharge curve and electrochemical impedance spectroscopy. The CoS/NF electrode demonstrates a high specific capacity of 377.5 mA h g-1 (1359 C g-1) at the current density of 2 A g-1, considerable rate performance and excellent durability (89.4% after 4000 cycles). A hybrid supercapacitor is assembled using CoS/NF as the positive electrode and activated carbon as the negative electrode, it shows a high energy density of 57.4 W h kg-1 at a power density of 405.2 W kg-1. The electrochemical results suggest that the CoS nanosheet arrays would possess excellent potential for applications in energy storage devices.

Janus Quasi-Solid Electrolyte Membranes with Asymmetric Porous Structure for High-Performance Lithium-Metal Batteries

Quasi-solid electrolytes (QSEs) based on nanoporous materials are promising candidates to construct high-performance Li-metal batteries (LMBs). However, simultaneously boosting the ionic conductivity (σ) and lithium-ion transference number (t+) of liquid electrolyte confined in porous matrix remains challenging. Herein, we report a novel Janus MOFLi/MSLi QSEs with asymmetric porous structure to inherit the benefits of both mesoporous and microporous hosts. This Janus QSE composed of mesoporous silica and microporous MOF exhibits a neat Li+ conductivity of 1.5 × 10-4 S cm-1 with t+ of 0.71. A partially de-solvated structure and preference distribution of Li+ near the Lewis base O atoms were depicted by MD simulations. Meanwhile, the nanoporous structure enabled efficient ion flux regulation, promoting the homogenous deposition of Li+. When incorporated in Li||Cu cells, the MOFLi/MSLi QSEs demonstrated a high Coulombic efficiency of 98.1%, surpassing that of liquid electrolytes (96.3%). Additionally, NCM 622||Li batteries equipped with MOFLi/MSLi QSEs exhibited promising rate performance and could operate stably for over 200 cycles at 1 C. These results highlight the potential of Janus MOFLi/MSLi QSEs as promising candidates for next-generation LMBs.

Laser-Induced and MOF-Derived Metal Oxide/Carbon Composite for Synergistically Improved Ethanol Sensing at Room temperature

Advancements in sensor technology have significantly enhanced atmospheric monitoring. Notably, metal oxide and carbon (MOx/C) hybrids have gained attention for their exceptional sensitivity and room-temperature sensing performance. However, previous methods of synthesizing MOx/C composites suffer from problems, including inhomogeneity, aggregation, and challenges in micropatterning. Herein, we introduce a refined method that employs a metal-organic framework (MOF) as a precursor combined with direct laser writing. The inherent structure of MOFs ensures a uniform distribution of metal ions and organic linkers, yielding homogeneous MOx/C structures. The laser processing facilitates precise micropatterning (< 2 μm, comparable to typical photolithography) of the MOx/C crystals. The optimized MOF-derived MOx/C sensor rapidly detected ethanol gas even at room temperature (105 and 18 s for response and recovery, respectively), with a broad range of sensing performance from 170 to 3,400 ppm and a high response value of up to 3,500%. Additionally, this sensor exhibited enhanced stability and thermal resilience compared to previous MOF-based counterparts. This research opens up promising avenues for practical applications in MOF-derived sensing devices.

Surface plasmon resonance Bismuth-modified NH2-UiO-66 with enhanced photocatalytic tetracycline degradation performance

For nearly a century, the misuse of antibiotics has gradually polluted water and threatened human health. Photocatalysis is considered an efficient way to remove antibiotics from water. Zirconium-based metal-organic frameworks have attracted much attention as promising photocatalysts for the degradation of antibiotics. However, single Zirconium-based metal-organic frameworks can still not achieve a more satisfactory photocatalytic efficiency, due to poor light absorption and charge separation efficiency. In this study, a novel metal-loaded metal-organic frameworks material was explored. As a potential photocatalytic material, the performance of NH2-UiO-66 in the photocatalytic degradation of tetracycline was greatly improved just by the loading of a single metal. Bismuth/NH2-UiO-66 photocatalysts of various compositions were physicochemically (TEM, SEM, XRD, XPS, BET, FTIR, UV-VIS, PL), and electrochemically (electrochemical impedance spectroscopy, photocurrent response) characterized. We evaluated the photocatalytic performance of Bismuth/NH2-UiO-66 composites by measuring their ability towards tetracycline decomposition in simulated sunlight irradiation conditions. The experimental results indicated that the introduction of metal Bismuth significantly boosts the photocatalytic activity of the composite catalysts. The final degradation rate of Bismuth/NH2-UiO-66 for tetracycline was found to be 95.8%, namely 2.7 times higher than pure NH2-UiO-66. This behavior is due to the surface plasmon resonance effect of Bismuth, which ameliorates the photocatalyst's electron-hole separation and strengthens the charge transfer. Apart from that, the presence of Bismuth magnifies the visible-light absorption range of Bismuth/NH2-UiO-66. In this study, an innovative approach for designing efficient and cost-effective metal-modified metal-organic frameworks photocatalysts is proposed.

Uncoordinated amino groups of MIL-101 anchoring cobalt porphyrins for highly selective CO2 electroreduction

Electrocatalytic carbon dioxide reduction reaction (CO2RR) presents a sustainable route to address energy crisis and environmental issues, where the rational design of catalysts remains crucial. Metal-organic frameworks (MOFs) with high CO2 capture capacities have immense potential as CO2RR electrocatalysts but suffer from poor activity. Herein we report a redox-active cobalt protoporphyrin grafted MIL-101(Cr)-NH2 for CO2 electroreduction. Material characterizations reveal that porphyrin molecules are covalently attached to uncoordinated amino groups of the parent MOF without compromising its well-defined porous structure. Furthermore, in situ spectroscopic techniques suggest inherited CO2 concentrate ability and more abundant adsorbed carbonate species on the modified MOF. As a result, a maximum CO Faradaic efficiency (FECO) up to 97.1% and a turnover frequency of 0.63 s-1 are achieved, together with FECO above 90% within a wide potential window of 300 mV. This work sheds new light on the coupling of MOFs with molecular catalysts to enhance catalytic performances.

Acute toxicity of nanoscale zeolitic imidazolate framework 8 (ZIF-8) to saltwater planktonic species Artemia salina and Nannochloropsis oculata

Zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) are metal-organic frameworks (MOFs) that have gained significant attention in various fields due to their unique properties. They have potential applications in drug delivery, gas storage, and catalysis. However, their increasing use raises concerns about their potential environmental impact. Our study evaluates the effects of ≈90 nm ZIF-8 NPs in two planktonic species, the green microalga Nannochloropsis oculata and the brine shrimp Artemia salina. After synthesis and characterization (SEM, EDS, BET, and DLS) of nanoporous ZIF-8 NPs, a growth inhibition test on microalgae (72 h) and acute immobilization test on instar I and II of Artemia nauplii (48 h) were conducted following, OECD 201 and ISO/TS 20787, respectively. The toxicity of ZIF-8 NPs to both species was time- and concentration-dependent. The 72-h median inhibitory concentration (IC50) of ZIF-8 NPs for N. oculata based on average specific growth rate and yield were calculated as 79.71 ± 8.55 mg L-1 and 51.73 ± 5.16 mg L-1, respectively. Also, the 48-h median effective concentration (EC50) of ZIF-8 NPs on immobilization rate of instar I and II were calculated as 175.09 ± 4.14 mg L-1 and 4.69 ± 0.34 mg L-1, respectively. Moreover, the swimming type of non-immobilized animals was affected by ZIF-8 NPs. These findings provide a good insight into the toxicity of nanoparticulate ZIF-8 to saltwater planktons and also confirm that instar II Artemia is more sensitive than instar I. This study demonstrated that ZIF-8 NPs, despite all their advantages, could have toxic effects on aquatic organisms. More studies are required to assess their potential environmental impact and develop strategies to mitigate their toxicity.

Graphene oxide dispersed mesoporous ZIF-8-encapsulated laccase for removal of toluidine blue with multiple enhanced stability

The extensive use and discharge of toluidine blue have caused serious problems to the water environment. As a green biocatalyst, laccase has the ability to decolorize the dyes, but it is limited by poor reusability and low stability. Metal-organic frameworks (MOFs) are a good platform for enzyme immobilization. However, due to the weak dispersion of MOFs, the enzyme activity is inevitably inhibited. Herein, we proposed to use graphene oxide (GO) as the dispersion medium of mesoporous ZIF-8 to construct MZIF-8/GO bi-carrier for laccase (FL) immobilization. On account of the narrower bandgap energy of FL@MZIF-8/GO (4.07 eV) than that of FL@MZIF-8 (4.69 eV), electron transport was enhanced which later increased the catalytic activity of the immobilized enzyme. Meanwhile, the improved hydrophilicity characterized by contact angle and full infiltration time further promoted the efficiency of the enzymatic reaction. Benefiting from such regulatory effects of GO, the composite showed excellent storage stability and reusability, as well as multifaceted enhancements including pH, thermal, and solvent adaptation. On the basis of the characterized synergistic effect of adsorption and degradation, FL@MZIF-8/GO was successfully applied to the degradation of toluidine blue (TB) with a removal rate of 94.8%. Even in actual treated wastewater, the highest removal rate still reached more than 80%. Based on the inner mechanism analysis and the universality study, this material is expected to be widely used in the degradation of pollutants in real water under complex environmental conditions.

Assembling Ag@CuO/UiO-66-NH2 nanocomposites for efficient photocatalytic degradation of xylene

Achieving efficient and stable photocatalytic degradation of xylene hinges on the advancement of photocatalytic materials with outstanding visible light activity. This low-carbon strategy serves as a promising solution to combat air pollution effectively. In this study, we synthesized a Z-scheme heterojunction Ag@CuO/UiO-66-NH2 nanocomposite by hydrothermal method to investigate its photodegradation properties for xylene gas under visible light conditions. XRD, XPS, SEM, FTIR, and UV-vis analyses were employed to confirm the presence of the Z-scheme heterojunction. The CuO/UiO-66-NH2 (CuU-2) composite has high photocatalytic activity, which is 2.37 times that of the original UiO-66-NH2. The incorporation of Z-scheme heterojunction facilitates efficient charge transfer and separation, leading to a substantial enhancement in photocatalytic activity. The Ag@CuO/UiO-66-NH2 (Ag-1@CuU) composite has the highest photocatalytic activity with a degradation efficiency of 84.12%, which is 3.36 times and 1.41 times that of UiO-66-NH2 and CuO/UiO-66-NH2, respectively. The silver cocatalyst improves the absorption capacity of the composite material to visible light, makes the ultraviolet visible absorption edge redshift, and significantly improves the photocatalytic performance. This study introduces a novel approach for xylene gas degradation and offers a versatile strategy for designing and synthesizing metal-organic framework (MOF)-based photocatalysts with exceptional performance.

Enzyme-mediated Ru@UiO-66@MnO2 NSs/thiamine-based ratiometric fluorescence sensor for visual detection of organophosphorus pesticide residues

In view of the potential hazards of organophosphorus pesticides (OPs), this paper constructed a ratiometric fluorescent probe utilizing a functionalized metal-organic framework to detect OPs. Ru(bpy)3Cl2 was encapsulated inside UiO-66 as a reference signal, and MnO2 nanosheets (MnO2 NSs) were grown on the surface to obtain Ru@UiO-66@MnO2 NSs. Acetylcholinesterase catalyzed the decomposition of acetylcholine into reductive thiocholine, which consumed MnO2 NSs, thus restoring the Ru@UiO-66 fluorescence. Due to the enzymatic inhibition of OPs and the redox reaction between MnO2 NSs and thiamine, this probe emitted blue fluorescence in the presence of OPs. The probe achieved linear responses to dichlorvos and chlorpyrifos with LODs of 9.99 × 10-6 μg mL-1 and 9.99 × 10-5 μg mL-1. The probe exhibited a satisfactory recovery rate for OPs in green tea. Furthermore, a hydrogel detection platform was developed by embedding the probe into sodium alginate. Overall, this work provides a visual approach to detect OPs in agricultural products.

Water-stable hydrophilic metal organic framework composite for the recognition of N-glycopeptides during diabetes progression by mass spectrometry

A hydrophilic Al-MOFs composite was prepared using cheap and available reagents in water via a suitable large-scale production, an economical and environment-friendly method for capturing N-glycopeptides. The prepared Al-MOFs composite with high hydrolytically stable and hydrophilic 1D channels exhibits an ultralow detection limit (0.5 fmol/μL), and excellent reusability (at least 10 cycles) in the capture of N-glycopeptides from standard bio-samples. Interestingly, the Al-MOFs composite also shows remarkable performance in practical applications, where 300 N-glycopeptides ascribed to 124 glycoproteins were identified in 1 µL human serum and were successfully applied in profiling the differences of N-glycopeptides during diabetes progression. Moreover, 12 specific glycoproteins used as biomarkers to accurately distinguish the progression of diabetes are identified. The present work provides a potential commercial method for large-scale glycoproteomics research in complex clinical samples while offering new guidance for the precise diagnosis of diabetes progression.

Interfacial reactivity-modulated fluorescent metal-organic frameworks for sensitive detection of interferon-γ towards tuberculosis diagnosis

A new aptamer-based method has been developed for interferon-γ (IFN-γ) detection by utilizing interface reactivity-modulated fluorescent metal-organic frameworks (MOFs). Specifically, the binding of IFN-γ to its aptamer decreases the interface reactivity between the biotin-labeled aptamer and the streptavidin-functionalized magnetic beads by generating significant steric effects. As a result, several biotin-labeled aptamers escape from the enrichment of magnetic beads and remain in the supernatant, which subsequently undergo the terminal deoxynucleotidyl transferase-catalyzed polymerization elongation. Along with the elongation, pyrophosphate is continuously produced as the by-product, triggering the decomposition of fluorescent MOFs to generate a remarkable fluorescent response with the excitation/emission wavelength of 610 nm/685 nm. Experimental results show that the method enables the detection of IFN-γ in the range 0.06 fM to 6 pM with a detection limit of 0.057 fM. The method also displays high specificity and repeatability with an average relative standard deviation of 2.04%. Moreover, the method demonstrates satisfactory recoveries from 96.3 to 105.5% in serum samples and excellent utility in clinical blood samples. Therefore, this work may provide a valuable tool for IFN-γ detection and is expected to be of high potential in tuberculosis diagnosis in the future.

Schiff base MOFs and their derivatives for sequestration and degradation of pollutants: present and future

Removal of contaminants via adsorption and catalysis have received a significant interest as energy and money-saving solutions for treating the world's wastewater. Metal-organic frameworks (MOFs), a newly discovered class of porous crystalline materials, have demonstrated tremendous promise in the removal and destruction of contaminants for water purification. In order to improve the interactions of MOFs with the target pollutants for their selective removal and degradation, the Schiff base functionalities emerged as promising active sites. Through pre- and post-synthetic alterations, Schiff base functionalities are integrated into the pore cages of MOF adsorbent materials. To understand the adsorptive/catalytic mechanism, potential interactions between the Schiff base sites and the target pollutants are discussed. Based on cutting-edge techniques for their synthesis, this paper examines current developments in the creation of Schiff base-functionalized MOFs as innovative materials for adsorptive removal and catalytic degradation of contaminants for water remediation.

Targeted drug delivery in pulmonary therapy based on adhesion and transmission of nanocarriers designed with a metal-organic framework

With the recent increase in lung diseases, especially with the onset of the coronavirus pandemic, the design of a highly efficient and optimal targeted drug delivery system for the lungs is crucial in inhaler-based delivery systems. This study aimed to design a magnetic field-assisted targeted drug delivery system to the lungs using three types of metal-organic frameworks (MOFs) and nanoliposomes. The optimization of the system was based on three main parameters: the surface density of the nanocarriers' (NCs) adherence to each of the lung branches, the amount of drug transferred to each branch, and the toxicity based on the rate of nanocarrier delivery to the branches. The study investigated the effect of increasing the diameter of the drug carriers and the amount of drug loaded onto the NCs in improving drug delivery to targeted areas of the lung. Results showed that the presence of a magnetic field significantly increased the adhesion of NCs to the targeted branches. The application of a magnetic field and the type of drug carrier had a significant effect on drug delivery downstream of the lung and reduced drug toxicity. The study found that Fe3O4@UiO-66 (iron-oxide nanoparticle attached to the surface of UiO-66, a type of MOF) and Fe3O4@PAA/AuNCs/ZIF-8 carriers, (iron-oxide nanoparticle attached to a hybrid structure composed of three different materials: poly (acrylic acid) (PAA), gold nanoclusters (AuNCs), and zeolitic imidazolate framework-8 (ZIF-8)), had the greatest drug delivery rate in diameters above 200 nm and less than 200 nm, respectively.

Air/liquid interfacial formation process of conductive metal-organic framework nanosheets

The air/liquid interface is a superior platform to create nanosheets of materials by promoting spontaneous two-dimensional growth of components. Metal-organic frameworks (MOFs)-intrinsically porous crystals-with π-conjugated triphenylene-based ligands show high electrical conductivities. Forming nanosheets of such conductive MOFs should enable their use in electronic devices. Although highly conductive MOF nanosheets have been created at the air/liquid interface, direct control of their continuity, morphology, thickness, crystallinity, and orientation directly influencing device performance remains as an issue to be addressed. Here, we present detailed insights into the formation process of electrically conductive MOF nanosheets composed of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) and Ni2+ ions (HITP-Ni-NS) at the air/liquid interface. The morphological and structural features of HITP-Ni-NS strongly depend on the standing time-the time without any external actions involved, but leaving the interface undisturbed after setting the ligand solution onto the metal-ion solution. We find that the fundamental features of HITP-Ni-NS are determined by the standing time with conductivity sensitively influenced by such pre-determined HITP-Ni-NS characteristics. These findings will lead towards the establishment of a rational strategy for creating MOF nanosheets at the air/liquid interface with desired properties, thereby accelerating their use in diverse potential applications.

Encapsulation of H4SiW12O40 into an Amide-Functionalized MOF: A Highly Efficient Nanocomposite Catalyst for Oxidative Desulfurization of Diesel Fuel

Production of hydrocarbon fuels containing sulfur in ultralow levels is in high demand and requires the development of novel catalytic systems for oxidative desulfurization (ODS). Herein, a new nanocomposite SiW12@ZSTU-10 catalyst containing H4SiW12O40 (SiW12) encapsulated into a zinc(II) 3D metal-organic framework (MOF) (ZSTU-10) was assembled and characterized. The intricate structure and porosity of ZSTU-10 permit efficient encapsulation of the catalytically active SiW12 cages. The impact of different experimental parameters on the ODS of model oil containing dibenzothiophene as a typical S-based contaminant was evaluated. The SiW12@ZSTU-10 catalyst exhibits remarkable activity with up to 99.8% sulfur removal in 30 min. Kinetic features, trapping tests, and mechanistic studies were also performed. Furthermore, the catalyst offered an outstanding thermal and chemical stability, without apparent leaching and decline in the activity after six cycles. Such an improved catalytic efficiency of SiW12@ZSTU-10 can be assigned to (i) size-matched occupation of the ZSTU-10 pores by SiW12-active species, (ii) prevention of polyoxometalate (POM) leaching from the MOF matrix, (iii) facilitation of the access of S-based substrates to the active sites of SiW12, and (iv) excellent stability and recyclability of the obtained nanocomposite. The preset work widens a family of promising nanocomposite catalysts for improving the desulfurization performance of hybrid POM-MOF catalytic systems.

Biocatalytic Buoyancy-Driven Nanobots for Autonomous Cell Recognition and Enrichment

Autonomously self-propelled nanoswimmers represent the next-generation nano-devices for bio- and environmental technology. However, current nanoswimmers generate limited energy output and can only move in short distances and duration, thus are struggling to be applied in practical challenges, such as living cell transportation. Here, we describe the construction of biodegradable metal-organic framework based nanobots with chemically driven buoyancy to achieve highly efficient, long-distance, directional vertical motion to "find-and-fetch" target cells. Nanobots surface-functionalized with antibodies against the cell surface marker carcinoembryonic antigen are exploited to impart the nanobots with specific cell targeting capacity to recognize and separate cancer cells. We demonstrate that the self-propelled motility of the nanobots can sufficiently transport the recognized cells autonomously, and the separated cells can be easily collected with a customized glass column, and finally regain their full metabolic potential after the separation. The utilization of nanobots with easy synthetic pathway shows considerable promise in cell recognition, separation, and enrichment.

Target-modulated mineralization of wood channels as enzyme-free electrochemical sensors for detecting amyloid-β species

Alzheimer's disease (AD) is an irreversible brain disorder, which has been found to be associated with neurotoxic amyloid-β oligomers (AβO). The early diagnosis of AD is still a great challenge. Herein, inspired by the hierarchical channel structure of natural wood, we design and demonstrate a low-cost and sensitive wood channel-based fluidic membrane for electrochemical sensing of AβO1-42. In this design, Zn/Cu-2-methylimidazole (Zn/Cu-Hmim) with artificial peroxidase (POD)-like activity was asymmetrically fabricated at one side of the wood channels by biomimetic mineralization and a subsequent ion exchange reaction. The strong affinity between Cu(II) and AβO1-42 enables Cu(II) species in Zn/Cu-Hmim to be extracted by AβO1-42, thus suppressing the POD-like performance via Zn/Cu-Hmim disassembly. Using Zn/Cu-Hmim to catalyze the oxidation reaction of 2,2'-diazo-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) by H2O2, the current-voltage (I-V) properties of wood channels are influenced by the generated oxidation product (ABTS•+), thus providing information useful for the quantitative analysis of AβO1-42. Importantly, the three aggregation states of Aβ1-42 (AβM1-42, AβO1-42, and AβF1-42) can also be identified, owing to the affinity difference and available reaction sites. The proposed wood membrane provides a novel, assessable, and scalable channel device to develop sensitive electrochemical sensors; moreover, the sustainable wood materials represent alternative candidates for developing channel-structured sensing platforms.

Sodium-alginate-laden MXene and MOF systems and their composite hydrogel beads for batch and fixed-bed adsorption of naproxen with electrochemical regeneration

Sodium alginate (SA)-laden two-dimensional (2D) Ti3C2Tx MXene (MX) and MIL-101(Fe) (a type of metal-organic framework (MOF)) composites were prepared and used for the removal of naproxen (NPX), following the adsorption and electrochemical regeneration processes. The fixed-bed adsorption column studies were also conducted to study the process of removal of NPX by hydrogels. The number of interactions via which the MX-embedded SA (MX@SA) could adsorb NPX was higher than the number of pathways associated with NPX adsorption on the MIL-101(Fe)-embedded SA (MIL-101(Fe)@SA), and the MX and MIL-101(Fe) composite embedded SA (MX/MIL-101(Fe)@SA). The optimum parameters for the electrochemical regeneration process were determined: charge passed and current density values were 169.3 C g-1 and 10 mA cm-2, respectively, for MX@SA, and the charge passed and current density values were 16.7 C g-1 and 5 mA cm-2, respectively, for both MIL-101(Fe)@SA and MX/MIL-101(Fe)@SA. These parameters enabled excellent regeneration, consistent over multiple adsorption and electrochemical regeneration cycles. The mechanism for the regeneration of the materials was proposed that the regeneration of MX@SA and MIL-101(Fe)@SA involved the indirect electrooxidation process in the presence of OH radicals, and the regeneration of MX/MIL-101(Fe)@SA involved the indirect oxidation process in the presence of active chlorine species.

Metal ion assistant transformation strategy to synthesize catechol-based metal-organic frameworks from Ti3C2Tx precursors

Chemical transformation strategy is capable of fabricating nanomaterials with well-defined structures and fascinating performance via controllable crystallization kinetics in the phase transformation. V2CTx MXene has been used as precursors to fabricate vanadium porphyrin metal-organic frameworks (V-PMOFs) via the coordination of deprotonated carboxylic acid ligands. However, the rational and in-depth exploration of synthesis mechanism with the aim of enriching the variety of MXene (i.e., Ti3C2Tx) and organic ligands (i.e., catechol-based) to design new MOFs is rarely reported. Herein, we have first developed a metal ion assistant transformation strategy to synthesize three-dimensional catechol-based TiCu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) MOFs with a non-interpenetrating SrSi2 (srs) framework using two-dimensional Ti3C2Tx as precursors. The unique synergetic transformation mechanism involves the electron transfer from Ti3C2Tx to electrostatically adsorbed Cu2+ ion for redox reaction, the subsequent Ti-C bond rupture for Ti4+ ion release, and the continuous chelation coordination between Ti4+/Cu2+ and HHTP. Ti3C2Tx precursors and auxiliary metal ion could be rationally substituted by V2CTx and Mn+ (e.g., Ni2+, Co2+, Mn2+, and Zn2+), respectively. This strategy lays the foundation for the design and synthesis of innovative and multifarious MOFs derived from MXene or other unconventional metal precursors.

Electrochemical chiral sensor for levofloxacin detection base on Cu/Fe-BTC amplification

The key to developing sensors for chiral drug determination is to exclude interference from enantiomers. In this study, metal-organic frameworks (MOFs) and molecularly imprinted polymer (MIP) were introduced to prepare a chiral sensor for levofloxacin detection. The MIP was electropolymerised on the surface of the Cu/Fe-benzene-1,3,5-tricarboxylate MOF (Cu/Fe-BTC)-modified Au electrode using levofloxacin as a template molecule. After eluting the levofloxacin, a chiral sensor with recognition sites for levofloxacin was obtained. With this site as a switch, a novel method for detecting levofloxacin was established. Because of the enhanced recognition effect, the sensor can effectively exclude the enantiomeric interference of d-ofloxacin. Moreover, Cu/Fe-BTC can effectively amplify the current response signal and improve the sensitivity of the sensor. The linear range of the sensor was 5 to 4000 × 10-11 mol L-1, and the detection limit was 2.07 × 10-11 mol L-1. When applied to detecting levofloxacin in actual samples, the sensor showed a 92.7-109.8% recovery.

A highly sensitive fluorescence "on-off-on" sensing platform for captopril detection based on AuNCs@ZIF-8 nanocomposite

Here, a novel fluorescent sensing strategy is established for the detection of captopril (CP) sensitively on the basis of a nanocomposite of gold nanoclusters (AuNCs) and metal-organic framework (AuNCs@ZIF-8). The aggregation-induced emission (AIE) effect will be triggered when AuNCs is encapsulated by metal-organic framework (MOF) which served as a carrier since it limits the molecular motion of AuNCs, and the fluorescence of AuNCs greatly enhanced about 5-time after forming the nanocomposites of AuNCs@ZIF-8. The strong orange-emission at 562 nm was quenched in the presence of mercury ions through dynamic quenching. After adding captopril, the quenched fluorescence of AuNCs@ZIF-8/Hg2+ system would be restored due to the specific interaction among captopril with mercury ions. Simultaneously, the restored degree of AuNCs@ZIF-8/Hg2+ fluorescence depended on the concentration of captopril. Hence, with AuNCs@ZIF-8 serving as reporter signal, the captopril content can be monitored by an "on-off-on" fluorescence sensing mode with a linear relationship of 1-100 μM, and the limit of detection for captopril was 0.134 μM.

Metal-organic frameworks modified melamine foam in pipette-tip for rapid solid-phase extraction of organophosphorus pesticides in fruits and vegetables

In this work, metal-organic frameworks (MOFs) including Fe-MIL-101 and Ti-MIL-125 were prepared and fixed on the melamine foam (MF) by polyvinylidene fluoride (PVDF) to prepare MF/PVDF/MOFs, which was used as adsorbents in pipette-tip solid-phase extraction (PT-SPE) for rapid extraction of organophosphorus pesticides (OPPs). Then, a gas chromatograph-flame thermionic detector (GC-FTD) was used for simultaneous analysis of Dimethoate (DMT), Iprobenfos (IBF), Parathion-methyl (PAM), and Chlorpyrifos (CPF). The morphology, crystal structure, and functional groups of MF/PVDF/MOFs were characterized, indicating that Ti-MIL-125 and Fe-MIL-101 were successfully synthesized and distributed on MF. The Fe-MIL-101 and Ti-MIL-125 showed good extraction ability for OPPs, which was mainly due to the π-π interaction and the multiple porous structures. Under the optimal conditions, the limit of detection (LODs) of four OPPs was 0.03-0.14 μg L-1 and the RSDs were less than 9.9%. The developed PT-SPE method showed a short extraction time (<3 min). The recoveries in fruits and vegetables (Celery, cabbages, and oranges) ranged from 75.3%-118.8% (RSDs<9.6%). The prepared MF/PVDF/MOFs demonstrated the efficient extraction performance of OPPs, contributing to the rapid pretreatment of OPPs from food and the environment.

Bioinspired microenvironment modulation of metal-organic framework-based catalysts for selective methane oxidation

Inspiration from natural enzymes enabling creationary catalyst design is appealing yet remains extremely challenging for selective methane (CH4) oxidation. This study presents the construction of a biomimetic catalyst platform for CH4 oxidation, which is constructed by incorporating Fe-porphyrin into a robust metal-organic framework, UiO-66, furnished with saturated monocarboxylic fatty acid bearing different long alkyl chains. The catalysts demonstrate the high efficiency in the CH4 to methanol (CH3OH) conversion at 50 °C. Moreover, the selectivity to CH3OH can be effectively regulated and promoted through a fine-tuned microenvironment by hydrophobic modification around the Fe-porphyrin. The long-chain fatty acids anchored on the Zr-oxo cluster of UiO-66 can not only tune the electronic state of the Fe sites to improve CH4 adsorption, but also restrict the amount of H2O2 around the Fe sites to reduce the overoxidation. This behavior resembles the microenvironment regulation in methane monooxygenase, resulting in high CH3OH selectivity.

A turn-on chemiluminescent assay for alkaline phosphatase using two-dimensional Fe-centered metal-organic frameworks as the signaling probe

Alkaline phosphatase (ALP) is an essential enzyme involved in cell phosphorus metabolism. Developing sensitive and accurate ALP quantitative assays is significant. In this study, a turn-on chemiluminescence (CL) analysis platform for the detection of ALP activity in human serum was established based on two-dimensional (2D) Fe-centered metal-organic frameworks with 1,3,5-benzene tricarboxylic acid as ligands (denoted as 2D Fe-BTC). The 2D Fe-BTC as the signaling probe reacts with ascorbic acid forming reduced Fe-BTC which catalyzes the luminol CL reaction producing a strong CL signal. The 2D Fe-BTC-based luminol CL reaction exhibited good CL responses when the concentration of ascorbic acid was in the range of 5-500 nM. By employing magnesium ascorbyl phosphate (MAP) as the substrate which can be hydrolyzed by ALP to generate ascorbic acid, a turn-on CL assay for the detection of ALP was established. Under optimal conditions, as low as 0.00046 U L-1 of ALP could be sensitively detected with a linear range of 0.001-0.1 U L-1. ALP in human serum can be detected after a simple dilution process without any other pretreatment.

Peroxymonocarbonate activation via Co nanoparticles confined in metal-organic frameworks for efficient antibiotic degradation in different actual water matrices

Traditional advanced oxidation processes suffer from low availability of ultrashort lifetime radicals and declining stability of catalysts. Co nanoparticles in hollow bimetallic metal-organic frameworks (Co@MOFs) were synthesized via a solvothermal method. Nanoconfinement and peroxymonocarbonate (PMC) degradation system endows Co@MOFs with high catalytic activity and stability even in the actual water matrices. The nanocomposites exhibited 100-200 nm polyhedron structure with irregular nanocavity between the 20 nm shell and multicores. Co nanoparticles were completely encapsulated by the FeIII-MOF-5 shell according to the X-ray diffraction and photoelectron spectra. Both 0.8 nm micropores and 3.6 nm mesopores were proven to be present. The yolk-shell Co@MOFs exhibited higher catalytic performance than that of Co nanoparticles, hollow FeIII-MOF-5 and its core-shell counterpart toward PMC activation during sulfamethoxazole degradation. The catalytic activities of Co@MOFs for the activation of unsymmetrical peroxides (PMC and peroxymonosulfate) were much higher than those for the symmetrical peroxides (H2O2 and persulfate) and the heterogeneous catalysis was dominant in the Co@MOFs activated H2O2 and PMC systems. The MOF stability was the highest and metal leakages were the least in the activated PMC system among the four peroxides because of mild reaction conditions and the alkalescent solution (pH = 8.3-8.4). Furthermore, the high removal efficiencies (>94%) and degradation rates could be maintained in the different actual water matrices due to the confinement effects. The contributions of carbonate and hydroxyl radicals were primary for sulfamethoxazole degradation, and superoxide anion and singlet oxygen also played essential roles according to scavenging experiments and time-series spin-trapping electron spin resonance spectra. Six degradation pathways were proposed according to 26 intermediate identification and the pharmacophores of more than 80% intermediates were destroyed, which would benefit subsequent biological treatment. Successful combination of nanoconfinement and PMC might provide a new effective solution for pollution remediation.

Nanoengineering Metal-Organic Frameworks and Derivatives for Electrosynthesis of Ammonia

Electrocatalytic synthesis under mild conditions has become increasingly important as one of the practical alternatives for industrial applications, especially for the green ammonia (NH3) industry. A properly engineered electrocatalyst plays a vital role in the realization of superior catalytic performance. Among various types of promising nanomaterials, metal-organic frameworks (MOFs) are competitive candidates for developing efficient electrocatalytic NH3 synthesis from simple nitrogen-containing molecules or ions, such as N2 and NO3-. In this review, recent advances in the development of electrocatalysts derived from MOFs for the electrosynthesis of NH3 are collected, categorized, and discussed, including their application in the N2 reduction reaction (NRR) and the NO3- reduction reaction (NO3RR). Firstly, the fundamental principles are illustrated, such as plausible mechanisms of NH3 generation from N2 and NO3-, the apparatus of corresponding electrocatalysis, parameters for evaluation of reaction efficiency, and detection methods of yielding NH3. Then, the electrocatalysts for NRR processes are discussed in detail, including pristine MOFs, MOF-hybrids, MOF-derived N-doped porous carbons, single atomic catalysts from pyrolysis of MOFs, and other MOF-related materials. Subsequently, MOF-related NO3RR processes are also listed and discussed. Finally, the existing challenges and prospects for the rational design and fabrication of electrocatalysts from MOFs for electrochemical NH3 synthesis are presented, such as the evolution of investigation methods with artificial intelligence, innovation in synthetic methods of MOF-related catalysts, advancement of characterization techniques, and extended electrocatalytic reactions.

Facile adsorption of organophosphate pesticides over HKUST-1 MOFs

The recovery of organophosphate pesticides (OPPs) from aqueous solutions is imperative considering their agricultural and environmental implications. Among various mitigation approaches used for OPPs' removal, adsorption offers many advantageous features for OPPs abatement owing to its benign nature, cost-effective processing, and non-requirement of excessive equipment. This research describes the adsorptive removal of three organophosphate pesticides (OPPs) namely chlorpyrifos (CPF), methyl parathion (MP), and malathion (MAL) by HKUST-1 (HKUST = Hong Kong University of Science and Technology) metal-organic framework (MOF). The synthesis of HKUST-1 MOFs was confirmed by various spectroscopic and microscopic techniques. The adsorption kinetics was systematically investigated by varying three parameters to include solution pH, contact time, and initial pesticide concentration. Among all the three pesticides, HKUST-1 showed enhanced removal of CPF in terms of pH, resulting in an adsorption capacity of 1.82 mg·g-1. However, under the effect of contact time at 60 min, the adsorption capacity of HKUST-1 for PM, MAL, and CPF were computed to be 1.83, 1.79, and 0.44 mg·g-1, respectively. Besides, HKUST-1 showed a remarkable performance towards adsorptive removal of MAL (14.01 mg·g-1 at 10 mg·L-1 concentration) with linear increase in adsorption capacity as the function of initial pesticide concentration. The MOFs were also able to retain ca. 50% of their adsorption efficiency over the course of five cycles of adsorptive removal of CP. In the future, a comprehensive data table showing the performance of various MOFs against various OPPs can be constructed on the basis of parameters used in this study.

Comprehensive evaluation of HKUST-1 as an efficient adsorbent for textile dyes

This study aimed to comprehensively assess the performance of HKUST-1, a metal-organic framework (MOF), as an adsorbent for various classes of textile dyes, including direct, acid, basic, and vinyl sulfonic reactive dyes. Real-world dyeing scenarios were simulated using carefully selected combinations of dyes to evaluate HKUST-1's effectiveness in treating dyeing process effluents. The results demonstrated that HKUST-1 exhibited highly efficient adsorption capabilities across all dye classes. Isolated direct dyes showed the best adsorption outcomes, with adsorption percentages exceeding 75% and reaching 100% for direct blue dye (Sirius Blue K-CFN). Basic dyes exhibited adsorption levels of nearly 85% for blue dye (Astrazon Blue FG), while the adsorption performance for the yellow dye (Yellow GL-E) was the poorest. The adsorption of dyes in combined systems followed a similar trend to that of isolated dyes, with the trichromy of direct dyes yielding the best results. Kinetic studies indicated that the adsorption of dyes followed a pseudo-second-order model, with nearly instantaneous adsorption observed in all cases. Furthermore, most dyes adhered to the Langmuir isotherm, further confirming the effectiveness of the adsorption process. The exothermic nature of the adsorption process was evident. Importantly, the study demonstrated the feasibility of reusing the HKUST-1, highlighting its potential as an exceptional adsorbent for removing hazardous textile dyes from effluents.

Enhanced catalytic oxidation of naproxen via activation of peroxymonosulfate by Fe-based metal-organic framework aerogels functionalized with Ag nanoparticles

In this study, Ag₃PO₄ and Fe-based metal-organic frameworks (MOFs)-functionalized three-dimensional (3D) porous gelatin aerogels (Ag/Fe@GMA) were fabricated and used as adsorbents and catalysts for the activation of peroxymonosulfate (PMS) for naproxen (NPX) removal from water. The morphology, crystallinity, surface functional groups, and surface chemical element compositions of the fabricated Ag/Fe@GMA was evaluated using various analytical techniques. Our results showed that as an adsorbent, Ag/Fe@GMA showed a 18.0 % higher NPX adsorption capacity compared with the pristine aerogels. This can be attributed to the well-embedded Ag₃PO₄ and MOFs, indicating a stronger interaction between functionalized aerogels and NPX. After adsorption, 99.9 % of total NPX removal was achieved within 15 min by activating PMS and effectively generating ^•OH and ^•SO₄^- in water. The PMS/Ag/Fe@GMA aerogel system also showed high removal performance for rhodamine B (99.5 %) and tetracycline (93.7 %). Moreover, the Ag/Fe@GMA aerogels showed excellent reusability to achieve 95.7 % NPX removal efficiency after six times of recycling. This study revealed that the Ag/Fe@GMA aerogels had good potential for PMS activation and NPX removal. In particular, as an alternative to powdery materials, 3D shape of Ag/Fe@GMA with excellent reusability facilitates its application in the treatment of water contaminated with organic contaminants.

Peptide-derived coordination frameworks for biomimetic and selective separation

Peptide-derived metal-organic frameworks (PMOFs) have emerged as a class of biomimetic materials with attractive performances in analytical and bioanalytical chemistry. The incorporation of biomolecule peptides gives the frameworks conformational flexibility, guest adaptability, built-in chirality, and molecular recognition ability, which greatly accelerate the applications of PMOFs in enantiomeric separation, affinity separation, and the enrichment of bioactive species from complicated samples. This review focuses on the recent advances in the engineering and applications of PMOFs in selective separation. The unique biomimetic size-, enantio-, and affinity-selective performances for separation are discussed along with the chemical structures and functions of MOFs and peptides. Updates of the applications of PMOFs in adaptive separation of small molecules, chiral separation of drug molecules, and affinity isolation of bioactive species are summarized. Finally, the promising future and remaining challenges of PMOFs for selective separation of complex biosamples are discussed.

Manganese cobalt-MOF@carbon nanofiber-based non-enzymatic histamine sensor for the determination of food freshness

Early detection of histamine in foodstuffs/beverages could be useful in preventing various diseases. In this work, we have prepared a free-standing hybrid mat based on manganese cobalt (2-methylimodazole)-metal organic frameworks (Mn-Co(2-MeIm)MOF) and carbon nanofibers (CNFs) and explored as a non-enzymatic electrochemical sensor for determining the freshness of fish and bananas based on histamine estimation. As-developed hybrid mat possesses high porosity with a large specific surface area and excellent hydrophilicity those allow easy access of analyte molecules to the redox-active metal sites of MOF. Furthermore, the multiple functional groups of the MOF matrix can act as active adsorption sites for catalysis. The Mn-Co(2-MeIm)MOF@CNF mat-modified GC electrode demonstrated excellent electrocatalytic activities toward the oxidation of histamine under acidic conditions (pH = 5.0) with a faster electron transfer kinetics and superior fouling resistance. The Co(2-MeIm)MOF@CNF/GCE sensor exhibited a wide linear range from 10 to 1500 µM with a low limit of detection (LOD) of 89.6 nM and a high sensitivity of 107.3 µA mM^-1 cm^-2. Importantly, as-developed Nb(BTC)MOF@CNF/GCE sensor is enabled to detect histamine in fish and banana samples stored for different periods of time, which thus indicates its practical viability as analytical histamine detector.

Fabricating Materials of Institute Lavoisier-53(Fe)/zeolite imidazolate framework-8 hybrid materials as high-efficiency and reproducible adsorbents for removing organic pollutants

Environmental pollution by emerging contaminants has become an urgent problem. Herein, novel binary metal-organic framework hybrids were constructed from Materials of Institute Lavoisier-53(Fe) (MIL-53(Fe)) and zeolite imidazolate framework-8 (ZIF-8) for the first time. A battery of characterizations were employed to determine the MIL/ZIF hybrids' properties and morphology. Furthermore, the MIL/ZIF towards toxic antibiotics (tetracycline, ciprofloxacin and ofloxacin) were studied to explore their adsorption abilities. The present work disclosed that the obtained MIL-53(Fe)/ZIF-8 = 2:3 possessed an eminent specific surface area with an admirable removal efficiency of tetracycline (97.4%), ciprofloxacin (97.1%) and ofloxacin (92.4%), respectively. The tetracycline adsorption process conformed to the pseudo-second-order kinetic model and this process was more compatible with the Langmuir isotherm model with the highest adsorption capacity of 215.0 mg g^-1. Moreover, the process of removing tetracycline was proved to be spontaneous and exothermic by the thermodynamic results. Furthermore, the MIL-53(Fe)/ZIF-8 = 2:3 towards tetracycline exhibited significant regeneration ability. The effects of pH, dosage, interfering ions and oscillation frequency on tetracycline adsorption capacity and removal efficiency were also investigated. The primary factors contributing to the decent adsorption ability between MIL-53(Fe)/ZIF-8 = 2:3 and tetracycline included electrostatic, π-π stacking, hydrogen bonding and weak coordination interactions. Additionally, we also investigated the adsorption ability in real wastewater. Thus, the proposed binary metal-organic framework hybrid materials can be deemed a promising adsorbent in wastewater purification.

Atomically Dispersed Dual-Metal Sites Showing Unique Reactivity and Dynamism for Electrocatalysis

The real structure and in situ evolution of catalysts under working conditions are of paramount importance, especially for bifunctional electrocatalysis. Here, we report asymmetric structural evolution and dynamic hydrogen-bonding promotion mechanism of an atomically dispersed electrocatalyst. Pyrolysis of Co/Ni-doped MAF-4/ZIF-8 yielded nitrogen-doped porous carbons functionalized by atomically dispersed Co-Ni dual-metal sites with an unprecedented N8V4 structure, which can serve as an efficient bifunctional electrocatalyst for overall water splitting. More importantly, the electrocatalyst showed remarkable activation behavior due to the in situ oxidation of the carbon substrate to form C-OH groups. Density functional theory calculations suggested that the flexible C-OH groups can form reversible hydrogen bonds with the oxygen evolution reaction intermediates, giving a bridge between elementary reactions to break the conventional scaling relationship.

Forward osmosis membrane doped with water-based zirconium fumarate MOFs to enhance dye pollutant removal and membrane antifouling performance

Metal-organic frameworks (MOFs) can be applied to enhance the property of forward osmosis membranes. However, organic solvents can easily remain in organic synthetic metal-organic frame materials and cause membrane fouling and a decrease in membrane permeability. In this study, water-based Zr-fumarate MOFs were synthesized and doped into the membrane active layer by interfacial polymerization to provide a water-based MOF-doped thin-film composite membrane (TFC membrane). It was found that doping the water-based MOFs effectively improved membrane hydrophilicity, and nanowater passages were introduced in the active layer to improve permeability. The water flux of the water-based MOF-doped TFC membranes was increased by 21% over that of the original membrane, and the selectivity performance of the membrane was improved while keeping the salt rejection basically unchanged. Additionally, the water-based MOF-doped TFC membrane showed good removal efficiency (R_d > 94%) and strong antipollution performance in the treatment of dye pollutants.