Metal-organic Framework Composite Materials Research Articles

Multi-electron transfer mechanism and band structures of CNTs in MOF-derived CNTs/Co hybrids for enhanced electromagnetic wave absorption property

Metal-organic framework (MOF)-derived magnetic metal/carbon nanocomposites have received widespread attention for electromagnetic wave (EMW) absorption. The present study introduces a novel approach to MOF composite material design by constructing composites modified with carbon nanotubes (CNTs) and magnetic Co nanoparticles. The carbon confinement effect in CNT/Co not only regulates the electronic structure of Co-C bonds, but also maintains the redox cycle of Co0/2→Co3+→Co0/2+, improving electronic activity and exhibiting synergistic integration characteristics of efficient electromagnetic wave absorption. Particularly, the maximum reflection loss (RLmin) of CNTs/Co-900 reached −52.7 dB at 4.67 GHz in the case of an absorber thickness of 1.6 mm. The excellent microwave absorption performance may be attributed to the interwoven structure formed by novel ZIF-67, CNTs, and Co metal nanoparticles and the double loss of magnetic Co and dielectric CNTs. In addition, the band gap of CNTs was calculated to be Eg = 0.27 eV by the semi-empirical tight-binding method with DFTB+. It is confirmed that CNTs have high electron migration ability, which is beneficial to conductive loss. It is confirmed that CNTs have high electron migration ability, which is beneficial to conductive loss. This study provides a novel strategy for the development of metal-organic framework-based magnetic particles/carbon nanocomposites for electromagnetic wave absorption.

Microenvironment modulation for enhanced photocatalytic hydrogen production in sandwich-structured metal-organic framework composite materials

Microenvironment modulation for enhanced photocatalytic hydrogen production in sandwich-structured metal-organic framework composite materials

Enhanced Active Sites and Stability in Nano-MOFs for Electrochemical Energy Storage through Dual Regulation by Tannic Acid.

The limited active sites and poor acid-alkaline solution stability of metal-organic frameworks (MOFs), significantly limit their wider application. In this study, the acid property of tannic acid (TA) was used as an etchant to etch the surface-active sites. Subsequently, the further chelation of the protonated TA with the exposed metal active site can effectively protect the metal ions. Meanwhile, the TA provided a large amount of phenolic hydroxyl groups, which can greatly improve the stability of imidazolate-coordinated MOFs. The electrochemical test results indicated that the MOFs composite materials synthesized using this scheme had high specific capacitance and stability. And the mechanism of its electrochemical reaction process was explored through in-situ XRD and theoretical calculations. In addition, the same treatment was carried out through a series of carboxyl-coordinated MOFs, which further confirmed the principle of this scheme to obtain a higher active site and stability. This paper explains the mechanism of functionalization of nano-MOFs by polyphenolic compounds, providing new ideas for the research of nano-MOFs.

Enhanced Active Sites and Stability in Nano‐MOFs for Electrochemical Energy Storage through Dual Regulation by Tannic Acid

AbstractThe limited active sites and poor acid‐alkaline solution stability of metal–organic frameworks (MOFs), significantly limit their wider application. In this study, the acid property of tannic acid (TA) was used as an etchant to etch the surface‐active sites. Subsequently, the further chelation of the protonated TA with the exposed metal active site can effectively protect the metal ions. Meanwhile, the TA provided a large amount of phenolic hydroxyl groups, which can greatly improve the stability of imidazolate‐coordinated MOFs. The electrochemical test results indicated that the MOFs composite materials synthesized using this scheme had high specific capacitance and stability. And the mechanism of its electrochemical reaction process was explored through in situ X‐ray diffraction (XRD) and theoretical calculations. In addition, the same treatment was carried out through a series of carboxyl‐coordinated MOFs, which further confirmed the principle of this scheme to obtain a higher active site and stability. This paper explains the mechanism of functionalization of nano‐MOFs by polyphenolic compounds, providing new ideas for the research of nano‐MOFs.

Rational post-synthesis of lipase-magnetic MOF conjugates with boosted enzymatic performance

Metal-organic frameworks (MOFs) have shown great potential as supports for enzyme immobilization, but their application is limited by separation difficulties due to their nanoscale size. Herein, magnetic MOFs (Fe3O4@MIL-53-NH2(Al)) were prepared under mild conditions, and an ionic liquid (IL) was used as linker to covalently immobilize lipase in Fe3O4@MIL-53-NH2-IL/PPL. The IL was composed of imidazolium cations and bis(trifluoromethylsulfonyl)imide anions, which enhanced the hydrophobicity of the support. The synthesized biocatalyst Fe3O4@MIL-53-NH2-IL/PPL showed excellent activity, 2.4 times higher than free lipase, and its denaturation, thermal, and storage stability were all satisfactory. The activity of the biocatalyst remained at up to 88.4% after ten recycles. The excellent magnetic responsiveness facilitated the collection of the biocatalyst, which may be beneficial to its reusability, and the multiple interactions between lipase and support may enhance the structural stability of lipase, which was investigated by circular dichroism spectroscopy. Compared to free lipase, both the substrate affinity and catalytic efficiency of Fe3O4@MIL-53-NH2-IL/PPL were improved. The magnetic MOF composite materials prepared through the post-synthesis method exhibited good potential in the field of lipase immobilization. The preparation method of immobilized lipase in this work provides a meaningful reference for the application of other MOF composites in the field of enzyme immobilization.

Silver Nanoparticle-Decorated Defective Zr-Based Metal–Organic Frameworks for Efficient Electrocatalytic Carbon Dioxide Reduction with Ultrahigh Mass Activity

Electrochemical reduction is considered to be a fascinating strategy to alleviate CO2 accumulation by converting it into value-added products. In this work, we used silver nanoparticle (Ag NP)-incorporated defective, thiol-functionalized UiO-66 metal–organic frameworks (MOFs) as a catalyst for the electrocatalytic conversion of CO2 to CO. We used a de novo defect engineering technique, coordination modulation, for defect incorporation as well as the functionalization of the MOF, where the introduced thiol moieties act as anchoring sites for the Ag NPs. Ag@UiO-66-SH catalyzed the CO2 reduction reaction to form CO with a Faradaic efficiency (FE) of 74% and a partial current density of 19.5 mA cm–2 at −1.1 V vs a reversible hydrogen electrode. This material showed remarkable catalytic stability, retaining the FE for CO without any significant loss in reduction current over 10 h and an excellent mass-specific activity of 218 A g–1. Density functional theory calculations further establish the enhanced catalytic CO2 reduction reaction (CO2RR) activity of Ag@UiO-66-SH compared to their pristine counterparts based on free energy calculations. This study demonstrates the use of metal NP–MOF composite materials with very less metal loading as an effective catalyst for CO2RR to CO.

Magnetic Fe3O4@ZIF-8 nanoparticles as a drug release vehicle: pH-sensitive release of norfloxacin and its antibacterial activity

Metal-organic frameworks (MOFs) have a high specific surface area and inherent biodegradability due to their unique structure and composition. As well, owing to the properties of nanomaterials and especially their magnetic features, Fe3O4 nanoparticles and MOFs composite materials have great potential in the design and application of drug release. The present work: firstly, investigated norfloxacin loading in magnetic metal organic framework (Fe3O4@ZIF-8); and secondly, studied the release of norfloxacin and its antibacterial activity. Results showed the release efficiencies reached 97 % at 310 K after 84 h (pH 7.4). Drug release behavior was tested at various pH levels and it was found that Fe3O4@ZIF-8 has pH-sensitive properties. Furthermore, the release model calculation illustrated that the release process fitted well to the Bhaskar model. The magnetic properties of Fe3O4@ZIF-8 confirmed that the composite has potential application for a targeted drug delivery system. The mechanism of pH-responsive norfloxacin release was combined with diffusion, ion exchange and electrostatic repulsion. Furthermore, the antibacterial activities of Fe3O4@ZIF-8 and NOR-Fe3O4@ZIF-8 were tested against Escherichia coli. Results showed that Fe3O4@ZIF-8 had good biocompatibility while NOR-Fe3O4@ZIF-8 can deter or inhibit the actions of microorganisms.

An easily-synthesized low carbon ionic liquid functionalized metal-organic framework composite material to remove Congo red from water

Congo red (CR) is documented as a typical azo dye compound that is widely used for industrial activities such as papermaking, textiles, leather and additives production, making it a main component of COD contaminants in industrial wastewaters. Excessive releases of CR have resulted in adverse impacts on water environments and ecological systems due to its non-biodegradable, toxic and carcinogenic properties. Therefore, the removal of CR from water environments is of important for wastewater treatment. Previous studies have proved that metal-organic frameworks (MOFs) were feasible for CR adsorption, but less stable in water environments. Several functionalized materials have therefore been used to produce MOF-derived composite material for better performance. To simplify the synthesis processes and reduce the energy consumption, an ionic liquid (IL) was used in this study for the synthesis of [BMIM][PF6]/ZIF-8 (BP/Z) composite material. The morphological structure of this material remained stable after the incorporation of IL. The equilibrium time of CR adsorption was 90 ​min with a maximum adsorption capacity of 1463 ​mg/g. Isotherm and kinetic studies revealed that the adsorption process was better described by Langmuir and pseudo-second-order model. Our results also presented that the IL/MOF composite material can be used within pH 5 and 6 with the presence of Na+, K+, Mg2+, Ca2+, Cl− and SO42−. It was also proved that the novel IL/MOF composites in this study have great potential to adsorb and remove organic dyes from water.

Exploring ionic liquid-laden metal-organic framework composite materials as hybrid electrolytes in metal (ion) batteries.

This review focuses on the combination of metal-organic frameworks (MOFs) and ionic liquids (ILs) to obtain composite materials to be used as solid electrolytes in metal-ion battery applications. Benefiting from the controllable chemical composition, tunable pore structure and surface functionality, MOFs offer great opportunities for synthesizing high-performance electrolytes. Moreover, the encapsulation of ILs into porous materials can provide environmentally benign solid-state electrolytes for electrochemical devices. Due to the versatility of MOF-based materials, in this review we also explore their use as anodes and cathodes in Li- and Na-ion batteries. Finally, solid IL@MOF electrolytes and their implementation into Li and Na batteries have been analyzed, as well as the design and advanced manufacturing of solid IL@MOF electrolytes embedded on polymeric matrices.

Waste-to-Resource Strategy to Fabricate Functionalized MOFs Composite Material Based on Durian Shell Biomass Carbon Fiber and Fe3O4 for Highly Efficient and Recyclable Dye Adsorption.

Recently, metal–organic frameworks (MOFs), which are porous inorganic–organic hybrid materials consisting of metal ions (clusters or secondary building units) and organic ligands through coordination bonds, have attracted wide attention because of their high surface area, huge ordered porosity, uniform structural cavities, and excellent thermal/chemical stability. In this work, durian shell biomass carbon fiber and Fe3O4 functionalized metal–organic framework composite material (durian shell fiber-Fe3O4-MOF, DFM) was synthesized and employed for the adsorption removal of methylene blue (MB) from wastewater. The morphology, structure, and chemical elements of the DFM material were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscope (XPS) techniques. Adsorption conditions such as pH, adsorption time, and temperature were optimized. The adsorption isotherm and kinetics results show that the adsorption process of DFM material to MB is more in line with the Freundlich model and pseudo-second-order kinetic model. Using these models, the maximum adsorption capacity of 53.31 mg/g was obtained by calculation. In addition, DFM material could be easily reused through an external magnet and the removal rate of MB was still 80% after five adsorption cycles. The obtained results show that DFM composite material, as an economical, environmentally friendly, recyclable new adsorbent, can simply and effectively remove MB from wastewater.

A Cu-BTC material encapsulated by chemical chromophore 1,3,6,8-tetrakis (p-benzoic acid) pyrene: Fluorescent sensing in recognition of the different ions

A kind of metal organic framework composite material was prepared by encapsulating chemical chromophore the 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4TBAPy) in Cu-BTC which has the large square-shaped pores, a reasonable degree of thermal stability and a capacity for chemical functionalization of the channel linings. Cu-BTC@H4TBAPy has superior luminescence performance than framework material Cu-BTC (H3BTC = 1, 3, 5-trimellitic acid). Base on its luminescence property, we performed fluorescence sensing experiments on heavy metal ions. The results show that the metal ion Fe3+ has a significant turn-off effect on Cu-BTC@H4TBAPy, while Al3+ has a significant turn-on effect on Cu-BTC@H4TBAPy. This indicates that Cu-BTC@H4TBAPy can play a role of fluorescent sensor switch in recognition of different ions.

Achieving High Performance Metal-Organic Framework Materials through Pore Engineering.

Achieving high performance functional materials has been a long-term goal for scientists and engineers that can significantly promote science and technology development and thus benefit our society and human beings. As well-known porous materials, metal-organic frameworks (MOFs) are crystalline open frameworks made up of molecular building blocks linked by strong coordination bonds, affording pore space for storing and trapping guest molecules. In terms of porosity, MOFs outperform traditional porous materials including zeolites and activated carbon, showing exceptional porosity with internal surface area up to thousands of square meters per gram of sample and with periodic pore sizes ranging from sub-nanometer to nanometers. Numerous MOFs have been synthesized with potential applications ranging from storing gaseous fuels to separating intractable industrial gas mixtures, sensing physical and chemical stimulus, and transmitting protons for conduction. Compared to traditional porous materials, MOFs are distinguished for their exceptional capability for pore adjustment and interior modification through pore engineering, which have made them a preeminent platform for exploring functional materials with high performance.Rational combinations of rigid building units of different geometry and multibranched organic linkers have provided MOFs with diverse pore structures, ranging from spherical to cylindrical, slit, and tubular ones isolating or interconnecting in different directions, which can be optimized for high-capacity gas storage. Based on the isoreticular principle and building blocks approach in MOF chemistry, the pore adjustment of porous materials can be performed with exquisite precision, making them suitable to address industrially important gas separation. The large pore cavities in MOFs are readily available for encapsulation of different functional guest species, resulting in novel MOF composite materials with various functions.In this Account, we summarize our recent research progress on pore engineering to achieve high-performance MOF materials. We have been able to tune and optimize pore structures, immobilize specific functional sites, and incorporate guest species into target MOF materials for hydrogen storage, methane storage, light-hydrocarbon purification, and proton conduction, especially for various industrially important gas separations including acetylene removal and ethylene and propylene purification. By engineering the porosity and pore chemistry that endows MOFs with multiple functionalities, our research endeavors have brought about the customization of high-performance MOF materials for corresponding application scenarios.

Enhancing in the hydrogen storage by SWCNT/HKUST-1 composites: Effect of SWCNT amount

Functionalized single-walled carbon nanotubes into HKUST-1 ([Cu3-(btc)2]; btc= 1,3,5-benzenetricarboxylate) metal organic framework composite materials were synthesized by solvothermal method and characterized using different techniques such as XRD, BET,TG, SEM, and in situ Raman spectroscopy. It is important to mention that for the first time the thermal stability of the materials was determined by in situ Raman spectroscopy. Our results demonstrated that the incorporation of functionalized SWCNTs into HKUST-1 a slight increase in the thermal stability of MOF was observed. Too, a significant enhancement in the hydrogen adsorption capacity from 23.5% at 77 K and 1 bar of in the composite materials was observed. After of 5 cycles, hydrogen uptake is still above 2.98 wt% for 0.5SW/HKUST-1 sample. The hydrogen adsorption isotherms in the composite materials were completely reversible, reflecting only the physisorption of hydrogen molecule in the structure surface. Our results showed that the composite material with small amount of carbon nanotubes can be a promising candidate for the hydrogen storage.

Modulated Synthesis of a Novel Nickel-Based Metal–Organic Framework Composite Material for the Adsorptive Desulfurization of Liquid Fuels

Modulated Synthesis of a Novel Nickel-Based Metal–Organic Framework Composite Material for the Adsorptive Desulfurization of Liquid Fuels

3D printing of metal–organic framework composite materials for clean energy and environmental applications

Rising CO2 levels strain the planet's ecosystems. New technologies are required to combat this climate emergency. Metal–organic frameworks and additive manufacturing provide options for gas storage and separations, water remediation, light generation, and catalysis.

Metal‐Organic Framework‐Based Catalysts for Oxidative Desulfurization

AbstractOxidative desulfurization (ODS) is emerging as the most promising methodology to remove refractive naturally occurring sulfides from fossil fuels. Metal‐organic frameworks (MOFs), a fascinating class of materials, are suitable as catalysts for this process due to the theoretical infinite number of combinations of polynuclear metal clusters and organic linkers. A rational fine‐tuning of the material structure, porosity and chemical functionality have given rise to a considerable number of MOF‐based catalytic active materials. Furthermore, MOFs can act as host, with programmable cavity sizes to accommodate catalytic species, forming novel robust catalytic MOF composite materials. Herein an account of this growing field of heterogeneous catalysis is reported and discussed, aiming to point out future outlooks and perspectives.

Production of microporous Cu-doped BTC (Cu-BTC) metal-organic framework composite materials, superior adsorbents for the removal of methylene blue (Basic Blue 9)

Abstract Cellulosic woven waste was used as a biomass material to prepare a Cu-doped BTC (Cu-BTC) adsorbent, which was then used to remove methylene blue (Basic Blue 9) from wastewater. Cellulosic woven waste was used as a biomass material to prepare a Cu-doped BTC (Cu-BTC) adsorbent, which was then used to remove methylene blue (Basic Blue 9) from wastewater. The Cu-BTC had higher adsorption capacity for methylene blue (BB9) than pure woven waste because it had high specific surface area and electrostatic interaction with cationic methylene blue molecules. The Cu-BTC removed methylene blue from wastewater rapidly and effectively and had an excellent adsorption capacity (197.90 mg/g). In batch process, the adsorption efficiency of the adsorbent for removal of BB9 was evaluated within 20 °C–60 °C, with initial BB9 concentrations of 50−200 mg/L and initial pH of 2−11. The Cu-BTC activation tailored the topological and textural properties of the obtained adsorbent, leading to a relatively large surface area of 1418.3 m2/g and pores with a volume of 0.491 cm3/g and an average size of 2.11 nm. The adsorption process fitted well with the Langmuir isotherm and the pseudo-second-order kinetic model. The possible mechanism for methylene blue removal mainly involved electrostatic attraction and micro pores. This study can serve as a guide for value-added utilization of cellulosic woven waste and as a practical method for the removal of methylene blue from wastewater. Adsorption of methylene blue onto the Cu-BTC is an effective and eco-friendly method for its removal from wastewater.

Facile preparation of magnetic covalent organic framework-metal organic framework composite materials as effective adsorbents for the extraction and determination of sedatives by high-performance liquid chromatography/tandem mass spectrometry in meat samples.

Sedatives, which are prone to cause residues in animals, have been abused in modern animal husbandry. Long-term consumption of contaminated meat products would be unfavorable to the human nervous system. Taking into account public health and food safety, it was essential to develop an effective method for the enrichment and detection of sedatives in meat. Fe3 O4 @TbBd@ZIF-8 composites were synthesized by using Fe3 O4 nanoparticles as a magnetic core and 1,3,5-triformylbenzene (Tb) and benzidine (Bd) as two building blocks to form Fe3 O4 @TbBd. Furthermore, the zeolitic imidazolate framework-8 (ZIF-8) was modified on the surface of the Fe3 O4 @TbBd. In addition, Fe3 O4 @TbBd@ZIF-8 was used as a magnetic solid-phase extraction (MSPE) adsorbent of typical animal sedatives in pork samples. Mass spectrometry analysis was conducted by electrospray ionization triple-quadrupole mass spectrometry in positive-ion multiple reaction monitoring mode. By combining the optimized MSPE approach with high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS), an accurate and sensitive method for the determination of sedatives was developed. The method exhibited good linearity in the range of 0.03-70 μg/kg with the correlation coefficient (R2 ) ranging from 0.9982 to 0.9999, high sensitivity with limits of detection (LODs) ranging from 0.04 to 0.2 μg/kg, and high precision with relative standard deviation (RSD) less than 5.5%. The adsorption behaviors of Fe3 O4 @TbBd@ZIF-8 towards sedatives were more suitably described by a pseudo-second-order kinetic and Freundlich isotherm model. The proposed MSPE-HPLC/MS/MS method was successfully applied to the determination of sedatives in real samples and showed excellent applicability. Several sedatives were detected in the selected meat samples. The developed method was shown to be facile, sensitive and accurate for sedative detection and also showed great prospects for determination of sedatives from other complex samples.

Core–Shell Metal–Organic Frameworks as the Stationary Phase for Hydrophilic Interaction Liquid Chromatography

A strategy based on in situ growth of a metal–organic framework composite material was proposed by introducing a sodium dodecyl benzenesulfonate (SDBS) group to increase the electrostatic interacti...

Microstructure of polymer-imprinted metal–organic frameworks determined by absorption edge tomography

Abstract Mechanochemically synthesized metal–organic framework material HKUST-1 in combination with acrylonitrile butadiene styrene polymer was used to form a polymer metal–organic framework composite material by a simple extruder. This composite filament was used for 3D printing. X-ray diffraction measurements were used to prove the homogeneous distribution of the metal–organic framework in the polymer on a centimeter scale, whereas X-ray Absorption Edge Tomography using a synchrotron radiation source was able to evaluate the 3D distribution of the metal–organic framework material both in the filament and the resultant printed sample with a resolution of a few μm. Our very first data indicate that, apart from a few clusters having significantly higher Cu concentration, HKUST-1 is distributed homogeneously down to the 100 μm length scale in both polymer bulk materials in the form of clusters with a size of a few μm. Absorption Edge Tomography in combination with data fusion also allows for the calculation of the metal–organic framework amount located on the external polymer surface.