Metal-organic Framework Composites Research Articles

Ligand-engineered Ru-doped cobalt oxides derived from metal-organic frameworks for large-current-density water splitting

The influence of the preorganized structure and chemical composition of metal-organic frameworks (MOFs) on the morphology, surface properties, and catalytic activity of the MOFs-derived metal oxides is yet to be revealed. In this work, two types of Co-MOFs with different coordination configurations are synthesized for the preparation of the structure-engineered ruthenium (Ru)-doped cobalt oxides. The effect of the preorganized coordination structure of the MOFs on the morphology and surface properties is investigated. Interestingly, the oxalate-based MOFs derived Ru-doped cobalt oxide (OX-Co3O4-Ru) exhibits much better surface wettability and more oxygen vacancies than the zeolitic imidazolate framework-67 derived Ru-doped cobalt oxide. As expected, the OX-Co3O4-Ru owns excellent catalytic properties towards both hydrogen evolution reaction and oxygen evolution reaction with an overpotential of 49 and 286 mV, respectively at a current density of 100 mA cm−2 in 1.0 M KOH. Importantly, the bifunctional OX-Co3O4-Ru catalyst offers an extremely high current density of 500 mA cm−2 at a cell voltage of 1.71 V for overall water splitting and as well demonstrates robust working stability.

Metal-organic framework composite Mn/Fe-MOF@Pd with peroxidase-like activities for sensitive colorimetric detection of hydroquinone

The construction of highly sensitive detection methods for hydroquinone (HQ) in environment and cosmetics is of great significance for environmental protection and human health. In this work, a novel detection method for HQ was successfully developed by constructing a metal-organic framework mimic enzyme colorimetric sensor (Mn/Fe-MOF@Pd1.0) with excellent peroxidase-like activity, which was synthesized by doping manganese ions into Fe-MOF by introducing bimetallic active centers, thereby improving the peroxidase-like activity of Fe-MOF, and the acid resistance and stability of Mn/Fe-MOF were improved by supporting palladium (Pd NPs). It is proven that Mn/Fe-MOF@Pd1.0 promoted the decomposition of hydrogen peroxide (H2O2) to generate active species, therefore, oxidized chromogenic substrate discoloration. On this basis, the detection of HQ based on the Mn/Fe-MOF@Pd1.0 colorimetric sensor was constructed, in which the limit of detection (LOD) was 0.09 μM in the linear range of 0.3–30 μM. Furthermore, Mn/Fe-MOF@Pd1.0 was successfully used for detecting HQ in hydroquinone whitening cream and actual water samples. The successful synthesis of Mn/Fe-MOF@Pd1.0 may provide new insights for further study of the enzyme-like activity of metal-organic framework composites, and the constructed facile and sensitive sensor system could broaden the application prospects of HQ detection.

Adsorption investigation of a composite of metal-organic framework and polyethylene oxide hydrogel

Though adsorption techniques are eco-environmentally friendly, most lack the effectiveness of complete contaminant elimination leading to increasing concerns about the presence of aqueous contaminants on humans. Thus, synergistic combination of low adsorption capacity adsorbents may be an effective method to enhance their aqueous contaminant uptake. Sol-gel synthesized lanthanum-1,4-benzene dicarboxylate metal organic framework (LaBDC MOF) and polyethylene oxide (PEO) hydrogel were combined to prepare a synergistic composite adsorbent (PEO-LaBDC) for aqueous methylene blue (MB) adsorption. Major properties of the pristine LaBDC MOF and PEO hydrogel were expressed in the characterized composite indicating successful preparation. PEO-LaBDC composite MB removal rate of MB was at least twice as fast (60 min) to those of the pristine LaBDC MOF (120 min) and PEO hydrogel (125 min). The fitting of kinetics model was fractal in nature, and optimum adsorption was on the alkaline end of the pH spectrum for all adsorbents (pH = 12, 10, and 10, respectively). Comparatively, the composite exhibited a better adsorption performance of ≈177% higher than the pristine LaBDC MOF; buttressing the idea that synergistic combination of adsorbents in composites could enhance adsorption processes. Therefore, the PEO-LaBDC composite is a promising adsorbent for the remediation of aqueous MB.

A composite of metal-organic framework and MXene for efficient and rapid uranium extraction from seawater

A composite of metal-organic framework and MXene for efficient and rapid uranium extraction from seawater

Computational Discovery for Crafting Multi-Dimensional and Multi-Functional Metal–Organic Framework Composites

Computational Discovery for Crafting Multi-Dimensional and Multi-Functional Metal–Organic Framework Composites

Acoustomicrofluidic synthesis of ZIF-8/HRP metal–organic framework composites with enhanced enzymatic activity and stability

Encapsulating enzymes within metal–organic frameworks (MOFs) constitute a promising strategy to circumvent their fragile nature in harsh environments, although deleterious molecular conformational changes and decreased substrate accessibility within the pores of the MOF during enzyme loading can often result in decreased catalytic activity. Herein, we report a rapid (within seconds) and facile one-pot aerosol-based method for simultaneous MOF crystallisation and enzyme encapsulation for the synthesis of ZIF-8/horseradish peroxidase (HRP) biocomposites using a high frequency acoustomicrofluidic nebulisation platform. As a consequence of the enhanced mixing and fast crystallisation afforded by the acoustic coupling into the precursors, the resultant combination of enhanced porosity, missing-linker/metal-node defect creation, pore activation and favourable conformational changes to the enzyme secondary structure allows for more efficient enzyme loading and greater enzyme–substrate interactions, and hence stronger enzyme binding within the MOF structure. Together, these culminate in a biocomposite that possesses four times greater enzymatic activity compared to that for the same material synthesized using conventional bulk-solution techniques, and endows the enzyme with increased protective effect (by approximately three to seven times) against high temperature and organic solvents, even after several exposure cycles. Such a possibility facilitates better potential for the enzyme to be recycled—an important factor given their typically high costs and the difficulty in recovering free enzymes in solution.

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.

Bimetal Metal-Organic Framework-Derived Ni-Mn@Carbon/Reduced Graphene Oxide as a Cathode for an Asymmetric Supercapacitor with High Energy Density.

As is known, metal-organic frameworks (MOFs) are a versatile class of materials in energy storage applications including supercapacitors. However, the individual kind of metal nodes connected by organic ligands to form a topological structure still limits the potential storage capacity of MOFs. Herein, a bimetal-based Ni-Mn MOF composite is configured with a one-pot hydrothermal method to derive a composite with a synergic effect to maximize the properties. Moreover, reduced graphene oxide (rGO) sheets are added as a conductive network to anchor the MOF-derived composite of Ni-Mn@C/rGO, which is expected to increase the conductivity of the materials system. The resulting composite exhibited a high specific capacitance of 1674 F g-1 at a current density of 0.3 A g-1, suggesting excellent energy storage performance. The composite was then integrated as the cathode in an asymmetrical supercapacitor with a 3D rGO aerogel anode, resulting in energy densities of 24.1 and 17.5 W h kg-1 at power densities of 88.9 and 444.4 W kg-1, respectively. Additionally, the device demonstrated remarkable long-term stability, with 90% capacitance retention after 10 000 charge-discharge cycles at 10 A g-1.

In Situ Monitoring of Nanocrystal Formation and Ion Migration in Lead Halide Perovskite Metal–Organic Framework Composites

AbstractCombining all‐inorganic perovskites (CsPbX3) with metal–organic frameworks (MOFs) offers great promise for efficient optoelectronic applications, but a lack of understanding of the microscopic mechanisms of host‐guest interactions that lead to stability limits their further advancement. Herein, a series of CsPbX3‐MOF composites is studied based on twinned Pb‐X‐based MOFs (X = Cl, Br) to explore the effect of the local ionic environment on their crystallization kinetics and the local photoluminescence (PL) properties by in situ fluorescence microscopy. Real‐time monitoring of the crystal growth process and PL characterization after complete crystallization shows a large compositional heterogeneity in the embedded mixed halogen perovskites. This heterogeneity is a result of the local ionic environment of the individual nanocrystals (NCs). In addition, the compositional heterogeneity is a dynamic phenomenon, manifested as spectral fluctuations of individual NCs on the time scales of tens of seconds under excitation. Compositional changes correlated over distances of micrometers point to collective ionic diffusion present in the system. This use of the in situ PL spectroscopy enables unique insights into the fundamental photophysical properties of perovskite‐MOF composites and will provide essential feedback for their further development and potential applications such as light‐emitting diodes and ion sensors.

One-pot synthesis of NH2-MIL-101(Fe) and α – Fe2O3 composite as efficient heterojunction for multifunctional photocatalytic membranes: Towards zero waste generation

Here in, one-pot synthesis of amine functionalized iron-based Metal-Organic Framework (MOF) namely NH2-MIL-101(Fe) is systematically tuned such that it also results in formation of morphology-oriented iron-oxide (α-Fe2O3) along with MOF, without adding any additional precursor. Ligand deficiency facilitates the free amine group of ligands to drive the formation of metal oxide (MO). This composite of MO and MOF behaves as a heterojunction that efficiently separates charge carriers and allows good photocatalytic activity, with more than 95 % degradation of methylene blue (MB) dye. The composite was then integrated into nanofiber membranes for water treatment, it resulted in overall 94 % rejection, with 20 % of MB being degraded simultaneously during this rejection and, this can be considered as fairly good for an emerging process that comprises of simultaneous degradation and separation. The new thermally stable and self-cleaning heterojunction MOF membranes developed in this study have sparked hopes as promising materials for near to zero waste generation in water treatment.

An enhanced field emission for display devices arises from the assembling of ZnO@MOF/MWCNTs

In this study, we propose a new, simple technique for raising the efficiency of field emission devices based on metal organic framework composites. Multi-walled carbon nanotubes (MWCNTs) and ZnO are used in the fabrication of metal-organicframeworks (MOFs) in this technique. This is explained by the composites unique structural structure, which offers a lot of easily available electro active sites, low surface work function, and improved electronic conductivity. One of the less complicated and more economical synthesis methods is used to synthesize the ZnO@MOF/MWCNTs composite. The material's precise morphological and structural features have all been investigated using Raman, FE-SEM, EDX, FTIR, and UV–Visible investigations. The ZnO@MOF/MWCNTs field emitter show impressive and stable field emission properties, such as a low turn-on electric field 0.50 V/μm and a high emission current density 219.15 mA/cm2.Our research revealed an easier way for boosting the electron field emission utilized in different field emission display systems that are based on MOFcomposites.

Zwitterionic metal–organic framework with highly dispersed ionic liquid for enhancing CO2 capture

Ionic liquids (ILs) have been often incorporated into metal–organic framework (MOF) to improve the performance of gas adsorption and separation. However, ILs are prone to agglomerate in the pores of MOFs, which causes insufficient exposure of their active sites, thus significantly reducing the separation efficiency. Herein, we report a zwitterionic MOF UiO-66-SO3−-NH3+ with both positive and negative charges for enhanced ILs dispersion and CO2 capture. When the ILs were introduced into UiO-66-SO3−-NH3+, they can be highly dispersed in the pores of MOF through the electronic interaction between positive and negative charges of MOF and anion and cation of ILs, and the active sites of IL can be adequately exposed. Notably, this is the first report of IL@zwitterionic MOF composites for CO2 capture. Compared with the single group modified counterparts, namely IL@UiO-66-NH2 and IL@UiO-66-SO3H, IL@UiO-66-SO3−-NH3+ exhibits higher CO2 affinity, which increases its CO2 adsorption capacity by 36–45%. Moreover, the CO2/N2 and CO2/CH4 adsorption selectivities of UiO-66-SO3−-NH3+ are 3.6–5.0 times and 2.1–2.5 times higher than that of single-group modified counterparts, respectively. This work not only provides a method to realize the high dispersion of ILs in MOF via constructing the zwitterionic MOF, but also reports an excellent adsorbent for CO2 capture.

Systematic designs of single metal compounds synthesized using ammonia fluoride-based complex as structure directing agents for energy storage

Tailoring morphology and composition of metal organic frameworks (MOF) can improve energy storage by establishing high surface area, large porosity and multiple redox states. Structure directing agents (SDA) is functional of designing surface properties of electroactive materials. Ammonium fluoride has functional abilities for designing MOF derivatives with excellent energy storage abilities. Systematic design of MOF derivatives using ammonia fluoride-based complex as SDA can essentially create efficient electroactive materials. Metal species can also play significant roles on redox reactions, which are the main energy storage mechanism for battery-type electrodes. In this work, 2-methylimidazole, two novel SDAs of NH4BF4 and NH4HF2, and six metal species of Al, Mn, Co, Ni, Cu and Zn are coupled to synthesize MOF derivatives for energy storage. Metal species-dependent compositions including hydroxides, oxides, and hydroxide nitrates are observed. The nickel-based derivative (Ni-HBF) shows the highest specific capacitance (CF) of 698.0F/g at 20 mV/s, due to multiple redox states and advanced flower-like surface properties. The diffusion and capacitive-control contributions of MOF derivatives are also analyzed. The battery supercapacitor hybrid with Ni-HBF electrode shows a maximum energy density of 27.9 Wh/kg at 325 W/kg. The CF retention of 170.9% and Coulombic efficiency of 93.2% are achieved after 10,000 cycles.

Synthesis and spectroscopic characteristics of chitosan composite of zinc-based metal-organic framework for rapid adsorption of organic pollutants from aqueous media

ABSTRACT The efficiency of the metal-organic framework of zinc (MOF-74) and its chitosan composite (CS/MOF-74) as a potential sorbent for the elimination of azo in addition to thiazine-type dyes from water by subsequent adsorption was studied. The synthesized adsorbents were characterized by various characterization techniques. The chitosan composite exhibited tremendous adsorption properties toward methyl orange (MO) and methylene blue (MB) at pH < 5.5 and pH > 5.5, respectively. The equilibrium data were evaluated by Dubinin-Radushkevich, Langmuir, Freundlich, and Tempkin isotherm models where the Langmuir model was best fitted to the adsorption data. The mono-layer sorption capacity values were found to be in the order 2047 mg/g and 1363 mg/g for MO and MB respectively onto CS/MOF-74 which are almost 6–8 epochs superior to MOF-74 and CS. In addition, pseudo-first, pseudo-second, intraparticle diffusion and Richenberg kinetic models were assessed to the kinetic data where the pseudo-second-order fitted very well to the adsorption data. The higher values of diffusion coefficient confirmed the greater involvement of the film diffusion than the pore and surface diffusion for the elimination of basic as well as acidic dyes onto CS/mOF-74. Thermodynamically, the negative value of isosteric heat of adsorption (Δ H ˉ ) concluded that the current study was found exothermic in nature. Moreover, electrostatic interactions, hydrogen bonding, and electron donor–acceptor interactions were suggested as probable mechanisms in the current adsorption process. The current study estimates the industrial importance of a chitosan composite of MOF-74 as it requires a short adsorption equilibrium time for the removal of the dyes and is satisfactorily reusable.

Selective adsorption of mercury ion from water by a novel functionalized magnetic Ti based metal-organic framework composite

In the context of industrialization and severe wastewater pollution, mercury ions pose a major threat due to their high toxicity. However, traditional adsorbents and common metal-organic framework (MOF) materials have limited effectiveness. This study focuses on combining magnetic materials with functionalized titanium-based MOF composite (SNN-MIL-125(Ti)@Fe3O4) to improve mercury ion adsorption. Through comprehensive characterization and analysis, the adsorption performance and mechanism of the material were studied. The optimal adsorption of the material was achieved at pH 5, exhibiting a pseudo-second-order adsorption model and the Hill theoretical capacity of 668.98 mg/g. Hill and Tempkin models confirmed the presence of chemical and physical adsorption sites on the material surface. Thermodynamic experiments showed a spontaneous endothermic process. Despite the presence of interfering ions, the material exhibited high selectivity for mercury ions. After four cycles, adsorption performance decreased by only 8%, indicating excellent reusability. Nitrogen- and sulfur-containing functional groups played a key role in mercury ion adsorption. In conclusion, SNN-MIL-125(Ti)@Fe3O4, as a magnetic MOF adsorption material, showed potential for effective remediation of mercury-contaminated wastewater. This study contributes to the development of efficient adsorption materials and enhances the understanding of their mechanism.

Linker Engineering of Sandwich-Structured Metal-Organic Framework Composites for Optimized Photocatalytic H2 Production.

While the microenvironment around catalytic sites is recognized to be crucial in thermocatalysis, its roles in photocatalysis remain subtle. Herein, a series of sandwich-structured metal-organic framework (MOF) composites, UiO-66-NH2 @Pt@UiO-66-X (X means functional groups), have been rationally constructed for visible-light photocatalytic H2 production. By varying -X groups of UiO-66-X shell, the microenvironment of Pt sites and photosensitive UiO-66-NH2 core can be simultaneously modulated. Significantly, the MOF composites with identical light absorption and Pt loading present distinctly different photocatalytic H2 production rates, following -X group sequence of -H > -Br > -NA (naphthalene) > -OCH3 > -Cl > -NO2 . UiO-66-NH2 @Pt@UiO-66-H demonstrates H2 production rate up to 2708.2μmol g-1 h-1 , ∼222 times that of UiO-66-NH2 @Pt@UiO-66-NO2 . Mechanism investigations suggest that the variation of -X group can balance the charge separation of UiO-66-NH2 core and proton reduction ability of Pt, leading to the optimal activity of UiO-66-NH2 @Pt@UiO-66-H at the equilibrium point. This article is protected by copyright. All rights reserved.

Porphyrin-Based MOF Thin Film on Transparent Conducting Oxide: Investigation of Growth, Porosity and Photoelectrochemical Properties.

Synthesizing metal-organic frameworks (MOFs) composites with a controlled morphology is an important requirement to access materials of desired patterning and composition. Since the last decade, MOF growth from sacrificial metal oxide layer is increasingly developed as it represents an efficient pathway to functionalize a large number of substrates. In this study, porphyrin-based Al-PMOF thin films were grown on conductive transparent oxide substrates from sacrificial layers of ALD-deposited alumina oxide. The control of the solvent composition and the number of atomic layer deposition (ALD) cycles allow us to tune the crystallinity, morphology and thickness of the produced thin films. Photophysical studies evidence that Al-PMOF thin films present light absorption and emission properties governed by the porphyrinic linker, without any quenching upon increasing the film thickness. Al-PMOF thin films obtained through this methodology present a remarkably high optical quality both in terms of transparency and coverage. The porosity of the samples is demonstrated by ellipsometry and used for Zn(II) insertion inside the MOF thin film. The multifunctional transparent, porous and luminescent thin film grown on fluorine-doped tin oxide (FTO) is used as an electrode capable of photoinduced charge separation upon simulated sunlight irradiation.

Selective enrichment of licorice triterpenoid saponins from complicated samples by magnetic poly(ionic liquid)-functionalized metal-organic framework

Licorice is a frequently-used natural sweetener and herbal medicine, and triterpenoid saponins are the main sweet constituents. This study provided a novel method for selective enrichment of licorice triterpenoid saponins by Fe3O4@UiO-66-(SH)2@p[VBAI]Cl, a new magnetic poly(ionic liquid)-functionalized metal-organic framework composite. Triterpenoid saponins had strong electrostatic interactions with p[VBAI]Cl, namely poly[1-(4-vinyl)benzyl-3-alkylimidazolium chloride], and UiO-66-(SH)2 further increased the adsorption ability. Fe3O4@UiO-66-(SH)2@p[VBAI]Cl could selectively enrich triterpenoid saponins from licorice-containing commercial products and plasma/tissue samples after oral consumption, and enrichment conditions were optimized with the representative compound glycyrrhizic acid. Based on this, two quantitative analysis methods were established combined with HPLC and LC-MS analysis, respectively, which were used to efficiently determine triterpenoid saponin content in in vitro and in vivo samples. The achieved LC-MS detection sensitivity was higher than previous studies. This is the first study for selective enrichment of natural products by poly(ionic liquid)-based magnetic solid phase extraction, and the method can contribute to quality assessment and mechanistic study of licorice.

A novel doped metal–organic skeleton MnDUT-52 as a sorbent for dispersive solid phase extraction of diphenyl ether herbicides in the water environment

A manganese doped metal–organic framework composite (MnDUT-52) was fabricated by a facile solvothermal method and applied as an adsorbent for dispersive solid phase extraction (DSPE) of trace diphenyl ether herbicides (Des) in water samples. The doped material exhibited large surface area (527.3 m2/g) and a higher zeta potential (43.2 mV) compared with its precursor (8.57 mV). And the quantitative parameters affecting the DSPE process (i.e., adsorbent amount, adsorption time, pH, ionic strength, desorption solvent and desorption volume) were optimized in detail. Under the optimal conditions, MnDUT-52 exhibited good reusability (6 times reuse, RSDs ≤ 5.8 %). Notably, the conjugation, hydrophobic and electrostatic interactions contributed to the good adsorption of Des by MnDUT-52. Finally, a method coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) was developed. It provided wide linear range (0.2–300 ng/mL), low detection limits (0.06–0.10 ng/mL) and extraction recovery (82.4–102.5 %). The developed method was successfully applied for the fast and sensitive determination of Des in water samples.

Fabrication of granular MOF@γ-Al2O3 composites as promising dual-function adsorbents for the efficient capture of iodine and dyes

As reported herein, we have designed an effective way to achieve in-situ loading of metal-organic frameworks (MOFs) into the pores of activated γ-Al2O3 particles to prepare low-cost, easy-to-obtain and high-yield granular MOFs composites (GMCs). MOF-5, ZIF-8, Ni-BTC, and Co-BTC have been selected to prepare GMCs via in-situ synthesis methods, thereby leading to the GMCs MOF-5-X@γ-Al2O3, ZIF-8-X@γ-Al2O3, Ni-BTC-X@γ-Al2O3, and Co-BTC-X@γ-Al2O3 (X = NO3 or OAc), respectively. The physical and chemical properties of the as-prepared MOF@γ-Al2O3 GMCs were characterized in detail. The results show that MOF-5-X@γ-Al2O3 and ZIF-8-X@γ-Al2O3 exhibit selective adsorption behavior for anionic dye. The adsorption capacities of MOF-5-X@γ-Al2O3 are 1388.01 mg g−1 (for CR and X = NO3), 1431.25 mg g−1 (for CR and X = OAc), 406.50 mg g−1 (for MO and X = NO3), and 234.16 mg g−1 (for MO and X = OAc), respectively, while the adsorption capacities of ZIF-8-X@γ-Al2O3 are 1426.85 mg g−1 (for CR and X = NO3), 1543.91 mg g−1 (for CR and X = OAc), 477.03 mg g−1 (for MO and X = NO3), and 451.02 mg g−1 (for MO and X = OAc), respectively. Moreover, ZIF-8-X@γ-Al2O3 has high adsorption performance for iodine molecules in solution, and the adsorption capacity reaches 630.63 mg g−1 for ZIF-8-NO3@γ-Al2O3 and 583.92 mg g−1 for ZIF-8-OAc@γ-Al2O3, respectively. This method is universal and can be used as an effective approach to prepare GMCs. In addition, the materials prepared by this method can be widely used in the adsorption of small molecules.