MOF Composites Research Articles

Aromatic carboxylic acid derived bimetallic nickel/cobalt electrocatalysts for oxygen evolution reaction and hydrogen peroxide sensing applications

• NiCo(OH) 2 and NiCo-MOFs were developed sucessfully as an efficient electrocatalysts for both OER and H 2 O 2 sensor applications. • NiCo-ABDC has exhibited excellent OER action, and a lower tafel slope value when compared to other metal oxides and NiCo-MOFs. • Also, NiCo-ABDC composite has high sensitivity, a low detection limit, and a better selectivity for electro-reductive H 2 O 2 detection. Development of suitable electrocatalysts is crucial for both oxygen evolution reaction (OER) and sensing applications. In this study, we present a solvothermal approach for producing a Nickel/Cobalt based Metal-Organic Framework (NiCo-MOF) employing various organic linkers including Benzene-1,4-dicarboxylic acid (BDC), 1,3,5-Benzene tricarboxylic acid (BTC), and 2-Amino Benzene-1,4-dicarboxylic acid (ABDC). The synthesized NiCo-MOF composites were characterized using Fourier-transform infrared spectroscopy (FT-IR), X-ray Diffraction (XRD),Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and X-ray photoelectron spectroscopy (XPS). NiCo-ABDC showed enhanced catalytic behavior for Oxygen Evolution Reaction (OER) with low onset over potential of 330 mV along with a modest tafel slope value of 88 mV/dec. Besides, NiCo-ABDC exhibited attractive stability for 1000 cycles and improved durability over 24 h which shows advanced kinetics over the noble metal catalysts and other carboxylic derived MOFs. As an electrochemical sensor, the NiCo-ABDF modified electrode shows a lower limit of detection (0.18 mM), highersensitivity (0.08 μA mM −1 ), and wider linear response (0–7 mM). This study provides clear evidence for the preparation of Ni-Co MOF composites without anchoring any polymer or carbon sources like graphene oxide (GO) and reduced graphene oxide (RGO), revealing its outstanding catalytic activity towards both OER and sensing applications.

Hybrid Nanoarchitectonics with Cr, Fe-MOF/ Graphene Nanocomposite for Removal of Organic Sulfur Compounds from Diesel Fuel

Metal–organic frameworks (Cr-MOF and Fe-MOF) and their graphene hybride nano-composites were prepared via green solvo-themal method. The prepared samples were characterized by XRD, FTIR spectroscopy, N2 adsorption–desorption isotherm and XPS. The composites were used for the adsorption of thiophenic sulfur compound (thiophene, dibenzothiophene, 4,6-dimethyldibenzothiophene) in a model fuel oil. It was found that, graphene in the MOF composite has positive effect on sulfur removal. The removal efficiency increase from 62% to % 95.6 using Fe-MOF and Fe-MOF/Gr (9:1), respectively. This enhancement effect is attributed to a greater number of coordinatively unsaturated sites (CUS) in the composites. The results indicated that the adsorption reach to 96.6% for DBT adsorption from model diesel oil and 62% for diesel fuel on using Cr-MOF/Gr composite.

Magnetic Zr-Based Metal-Organic Frameworks: A Highly Efficient Au (III) Trapper for Gold Recycling.

In this work, the magnetic Zr-based MOF composites with excellent retrievability were prepared using Fe3O4@SiO2 as the core and UiO–66–NH2 as the shell. Fe3O4@SiO2 core could introduce mesopores and result in capillary condensation in MOF composites, which aggravated with the dosage of Fe3O4@SiO2. The as-synthesized MOF composites could be rapidly retrieved from aqueous solution via magnetic separation in 10 seconds. pH imposed an important effect on Au (III) adsorption by governing the ion exchange and electrostatic interaction between Au (III) anions and adsorbents, and the optimal adsorption happened at pH 7. The adsorption process fitted well with the pseudo-second order kinetics model and Langmuir adsorption model. The maximum adsorption capacity of Au (III) by FSUN–10 and FSUN–50 at 298 K were determined to be 611.18 mg∙g−1 and 463.85 mg∙g−1, respectively. Additionally, Au (III) uptakes increased with temperature. Beyond experiments, the adsorption mechanisms were thoroughly studied through systematic characterization, molecular dynamics simulation (MDS) and density functional theory (DFT) study. It was verified that Au (III) was adsorbed via coordination to hydroxyl and amino groups and was reduced to Au (I) and Au (0) by amino groups. The diffusion coefficient of Au (III) along UiO–66–NH2 was calculated to be 5.8 × 10−5 cm2∙s−1. Moreover, the magnetic Zr-based MOF composites exhibit great industrial value in gold recycling with high adsorption selectivity and good recyclability.

Noble‐metal free Suzuki–Miyaura reaction catalyzed by magnetically recyclable MOF composites

An effective metal–organic frameworks composite, Cu‐BTC@Fe3O4, was applied to catalyze Suzuki–Miyaura reaction under mild conditions and could achieve a good yield up to 98%. This magnetic noble‐metal free catalyst was proved excellent reusability for at least four cycles without loss of catalytic activity and crystallinity. X‐ray photoelectron spectroscopy confirmed that the binding energy of Fe‐2p shifted to a negative value by 0.3 eV in Cu‐BTC@Fe3O4 after catalysis; in the meantime, the binding energy of Cu‐2p shifted to a positive value by 0.1 eV. A possible bimetallic catalytic mechanism involved in this coupling reaction was proposed. In addition, the heterogeneous and recyclable properties of the catalyst were shown by hot filtration experiments, and the catalyst can be easily separated from reaction system in the presence of magnetic field.

Non-contact real-time detection of trace nitro-explosives by MOF composites visible-light chemiresistor.

To create an artificial structure to remarkably surpass the sensitivity, selectivity and speed of the olfaction system of animals is still a daunting challenge. Herein, we propose a core-sheath pillar (CSP) architecture with a perfect synergistic interface that effectively integrates the advantages of metal–organic frameworks and metal oxides to tackle the above-mentioned challenge. The sheath material, NH2-MIL-125, can concentrate target analyte, nitro-explosives, by 1012 times from its vapour. The perfect band-matched synergistic interface enables the TiO2 core to effectively harvest and utilize visible light. At room temperature and under visible light, CSP (TiO2, NH2-MIL-125) shows an unexpected self-promoting analyte-sensing behaviour. Its experimentally reached limit of detection (∼0.8 ppq, hexogeon) is 103 times lower than the lowest one achieved by a sniffer dog or all sensing techniques without analyte pre-concentration. Moreover, the sensor exhibits excellent selectivity against commonly existing interferences, with a short response time of 0.14 min.

Metal-organic framework-derived carbon nanotubes for broadband electromagnetic wave absorption

The widespread use of communication devices has exacerbated the deterioration of the electromagnetic environment, and thus there is an urgent need to develop more efficient electromagnetic wave (EMW) absorbing materials. Metal-organic frameworks are highly prized for their unique structures and excellent electrical conductivity. Here, in order to break the single way of designing MOF composites and compensate for its lack of magnetic loss capability, an attempt was made to prepare composites with magnetic Co/carbon nanotube (CNT) modification for EMW absorption. The carbon nanotube-encapsulated cobalt metal particles anchored in the matrix enable the composite to enhance electromagnetic wave absorption. Notably, the Co@CNTs/PC composite exhibits excellent EMW absorption performance. A minimum reflection loss of −56.23 dB and a maximum effective absorption bandwidth of 7.36 GHz were obtained at 2.3 mm thickness, respectively. In addition to this, the possible mechanisms involved in EMW uptake are elucidated in detail. These results demonstrate an environmentally friendly and simple strategy for the preparation of MOF substrate-based EMW absorbers.

Thermal steam reduction etching to construct POM@CuICuII-BTC with hierarchical porosity for adsorption property enhancement

Host MOFs with atomically precise characteristics and functional-oriented guest molecules are the key to assemble multifunctional host–guest MOF composites. We selected O−rich POM tungstophosphoric acid (TPA) and CuII-BTC with high stability and adjustable structure to synthesize host–guest TPA@CuII-BTC. Then thermal steam reduction etching was used to construct TPA@CuICuII-BTC with hierarchical pores at molecular scale, enlarging the pore space and making partially inaccessible sites of TPA@CuII-BTC more expose. Under the thermal methanol atmosphere, partial six-coordinated metal node Cu2+ was reduced slowly into Cu+ with lower coordination number, accompanied by the fracture of partial Cu−O coordination bonds. The generated TPA@CuICuII-BTC not only obtained larger pore and exposed more space in contrast to TPA@CuII-BTC, but also possessed more free hydroxyl oxygen sites due to the breaking of partial coordination bonds, promoting the contact and interaction of the composite with external substances. The Pb2+ adsorption experiment showed that TPA@CuICuII-BTC exhibited best adsorption ability to external Pb2+, and the adsorption capacity was 614.95 mg·g−1, which was 180.25 mg·g−1 and 243.45 mg·g−1 higher than that of TPA@CuII-BTC and CuII-BTC. This work has great reference significance for the construction of MOF composites with hierarchical porosity and the study of MOF composites on adsorption performance improvement.

Visible-light-assisted persulfate activation by SnS2/MIL-88B(Fe) Z-scheme heterojunction for enhanced degradation of ibuprofen

Herein, a highly efficient Z-scheme SnS2/MIL-88B (Fe) (SnSFe) heterojunction was successfully synthesized to use both as photocatalysts and persulfate (PS) activator for ibuprofen (IBP) degradation. Flower-liked SnS2 was uniformly loaded on MIL-88B (Fe), and SnSFe retained the original polyhedral morphology of MIL-88B (Fe). The highest removal of IBP was achieved in the presence of SnSFe with 0.5% SnS2(SnSFe0.5). Characteristic results and density functional theory calculations demonstrated that the enhanced degradation of IBP was due to the difference in Fermi energy levels of SnS2 and MIL-88B (Fe) leading to electrons transferred from SnS2 to MIL-88B (Fe), and SnO bond was formed in SnSFe. , OH and O2− were the main active species in SnSFe0.5/PS/visible light system. Z-scheme heterojunction of SnSFe was constructed to propose the degradation mechanism. This research revealed that the synergism of photocatalysis and PS activation using SnS2/Fe-based MOFs composites possessed great potentials in wastewater remediation.

Facile in-situ strategy for incorporating amphoteric dopamine into metal–organic framework with optimized degradation capacity of nerve agents simulant

Zr based metal−organic frameworks (Zr-MOFs) as the state-of-the-art catalytic materials have been revealed great potential for instantaneous degradation of the deadly toxic organophosphorus nerve agent. On account of the prerequisite of MOFs practically working in hydrolysis of organophosphorus toxicant is need volatile liquid base, the utility of MOFs on nerve agent degradation is greatly limited. Thus, developing catalytic materials with well performance in pure water is aa great challenge for catalytic hydrolysis of nerve agent under practical field. Herein, we report an in-situ strategy to synthesize MOF composites incorporated with dopamine (DA), a molecule contains amphoteric amino and catechol groups. The integration of DA onto internal structure of Zr-MOFs leads to the optimal performance and robustness for rapid nerve agent simulant degradation. The hydrolysis catalyzed by UiO-66-NH2@DA can reach to a half-life of 7 min, a considerable rapid rate compared to the more than 20 min of monotonic basic functional agents in a non-alkaline environment, besides, the optimized functional MOF, MOF-808@DA, outperformed most previously reported MOF-based catalysts with a half-life of 0.64 min and the time of 100% detoxification within 5 min.

Dye-Encapsulated Lanthanide-Based Metal-Organic Frameworks as a Dual-Emission Sensitization Platform for Alachlor Sensing.

As an important factor affecting global agricultural output, pesticides have a significant impact on the ecosystem. It is an urgent task to accurately and conveniently detect pesticide residues after their application. Herein, a fluorescent dye@MOF platform was designed via the encapsulation of rhodamine B (RhB) into the MOF structure (named RhB@HNU-48), which can significantly enhance the sensing sensitivity of alachlor with an ultralow detection limit of 0.59 ppb. The improved sensitivity of RhB@HNU-48 to pesticides was attributed to the host-guest interactions that affect the excitation and emission spectra of the composites. Based on the sensing capability of RhB@HNU-48, a logic gate was built to evaluate the safety level of alachlor residues in rivers and soil. The preparation of photofunctionalized MOF composites through modulation of host-guest interactions offers a promising strategy for the construction of desired sensors for agricultural residues.

Efficient removal of selenite in aqueous solution by MOF-801 and Fe3O4/MOF-801: Adsorptive behavior and mechanism study

Metal-organic framework materials (MOFs) and MOFs-based composite materials have been extensively applied to adsorb heavy metals due to their high specific surface area and high porosity. Herein, the MOF-801 and its complex Fe3O4/MOF-801 were respectively prepared and employed as adsorbents to capture the Se(IV) in an aqueous solution. And the Fe3O4/MOF-801 composite was post-synthesized from MOF-801 by a simple cryogenic hydrothermal process. The experimental results showed that the maximum adsorption capacity of MOF-801 and Fe3O4/MOF-801 was 101.2 and 206.6 mg/g under acidic conditions, respectively. The coexisting anions, except phosphate and sulfate ions, had negligible effect on the Se(IV) adsorption. The mechanism of Se(IV) removal by the two adsorbents was thoroughly analyzed by Zeta potential, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). And the results illustrates that the Se(IV) was captured on the surface hydroxyl sites of the MOF-801, while the Fe3O4/MOF-801 captured Se(IV) through electrostatic attraction, inner-sphere complexation, and the reduction effect. Furthermore, the existence of charge transfer in the Fe3O4/MOF-801, which facilitated the adsorption and reduction of Se(IV), was confirmed by the XPS analysis. This work provides a promising strategy to design high-performance magnetic MOFs composites for the removal of Se(IV) from wastewater.

Charge Separation by Creating Band Bending in Metal–Organic Frameworks for Improved Photocatalytic Hydrogen Evolution

AbstractMetal–organic frameworks (MOFs) have been intensively studied as a class of semiconductor‐like materials in photocatalysis. However, band bending, which plays a crucial role in semiconductor photocatalysis, has not yet been demonstrated in MOF photocatalysts. Herein, a representative MOF, MIL‐125‐NH2, is integrated with the metal oxides (MoO3and V2O5) that feature appropriate work functions and energy levels to afford the corresponding MOF composites. Surface photovoltage results demonstrate band bending in the MOF composites, which gives rise to the built‐in electric field of MIL‐125‐NH2, boosting the charge separation. As a result, the MOF composites present 56 and 42 times higher activities, respectively, compared to the pristine MOF for photocatalytic H2production. Upon depositing Pt onto the MOF, ∼6 times higher activity is achieved. This work illustrates band bending of MOFs for the first time, supporting their semiconductor‐like nature, which would greatly promote MOF photocatalysis.

Notably decreased dielectric loss of high dielectric constant P(VDF-TrFE)/CuBTC MOF composites through adding silica powder

Notably decreased dielectric loss of high dielectric constant P(VDF-TrFE)/CuBTC MOF composites through adding silica powder

A novel magnetic double MOF composite is synthesized for removing azole fungicides economically and efficiently

In this study, Fe3O4@ZIF-90@MIL-68(Al) composite was synthesized by a facile method and used as a reusable adsorbent to effectively remove azole fungicides from paddy field water. Notably, the introduction of ZIF-90 made the magnetic adsorbent more stable and significantly improved the adsorption performance. Specifically, a series of characterization analysis were carried out and this composite displayed a high specific surface area, excellent magnetic strength, and good thermal stability, which meet the expectations. Additionally, the adsorption behaviors and mechanisms of Fe3O4@ZIF-90@MIL-68(Al) toward azole fungicides were studied systematically. The pseudo-second-order kinetic model and Langmuir isotherm model was confirmed to be more suitable for describing this adsorption process. Besides, the adsorption process of azole fungicides onto Fe3O4@ZIF-90@MIL-68(Al) was mainly based on pore filling, surface complexation, covalent bonding, π-π stacking effect and hydrogen bonding. Interestingly, the maximum adsorption capacity of Fe3O4@ZIF-90@MIL-68(Al) toward prochloraz was 352.32 mg g−1, which was probably one of the highest adsorption capacities reported. Meanwhile, the magnetic adsorbent can be regenerated by methanol treatment and maintain a high adsorption capacity after the 10th cycle. Hence, this work provides an economical and feasible method for removing azole fungicides from field water samples.

Preparation of new MOF-808/chitosan composite for Cr(VI) adsorption from aqueous solution: Experimental and DFT study

In this study, a series of Zirconium-based MOF and chitosan composites (MOF-808/chitosan) were synthesized as efficient adsorbent for Cr(VI) ions elimination from aqueous solution. MOF-808/chitosan structure and morphology was characterized by FE-SEM, EDX, XRD, BET, zeta potential analysis, FT-IR, XPS techniques. The kinetic studies ascertained that Cr(VI) adsorption over MOF-808/chitosan followed pseudo-second-order kinetic model. The adsorption isotherms fitted the Langmuir isotherm model, implying on homogeneously adsorption of Cr(VI) on the surface of MOF-808/chitosan. According to the Langmuir model, the maximum capacity was obtained to be 320.0 mg/g at pH 5. Thermodynamic investigation proposed spontaneous (ΔG° < 0), disordered (ΔS° > 0) and endothermic (ΔH° > 0) for adsorption process. Besides, MOF-808/chitosan displayed an appropriate reusability for the elimination of Cr(VI) ions from their aqueous solutions for six successive cycles. DFT study of the adsorption process displayed and confirmed the role of hydrogen bonding and electrostatic attraction simultaneously.

Morphology-controlled CoNi/C hybrids with bifunctions of efficient anti-corrosion and microwave absorption

• The electromagnetic response of morphology-dependant porous/hollow hybrids was investigated. • Rod-shaped composites are endowed with excellent absorption properties. • Samples CoNi/C-r-700 and CoNi/C-d-700 present relatively high E corr and low I corr . Till now, fewer literatures have investigated the corrosion resistance of microwave absorbers, especially mental@C/carbon matrix derived from MOF composites, although it is known that carbon shells possess a protective effect. Herein, three kinds of morphology-controlled CoNi/C-N doped architectures were successfully fabricated via a sequence of processing, namely coprecipitation for ZIF-67, subsequent Ni 2+ exchange and ultimate carbonization. Apart from composition characterization, the effects of microstructure tailoring and temperature controlling on electromagnetic response as well as attenuation performance were revealed, where dodecahedron-shaped composites possessed the highest permittivity. By contrast, rod-shaped composites (CoNi/C-r-550 and CoNi/C-r-700) were endowed with superior comprehensive absorption properties, e.g., RL min : -49.8 dB and -64.0 dB; EAB: 5.7 GHz and 4.8 GHz, respectively. Besides, samples CoNi/C-d-700 and CoNi/C-r-700 present higher corrosion potential ( E corr ) and lower corrosion current ( I corr ). Hence, these corrosion-resistant microwave absorbers with outstanding absorption stability, wetting effect as well as environmental adaptability, can be used as a candidate/raw material for intelligent devices.

MOF composites derived BiFeO3@Bi5O7I n–n heterojunction for enhanced photocatalytic performance

BiFeO3 is a photocatalyst with excellent performance. However, its applications are limited due to its wide bandgap. In this paper, MIL-101(Fe)@BiOI composite material is synthesized by hydrothermal method and then calcined at high temperature to obtain BiFeO3@Bi5O7I composite material with high degradation capacity. Among them, an n–n heterojunction is formed, which improves the efficiency of charge transfer, and the recombination of light-generated electrons and holes promotes improved photocatalytic efficiency and stability. The result of photocatalytic degradation of tetracycline under visible light irradiation showed, BiFeO3@Bi5O7I (1:2) has the best photodegradation effect, with a degradation rate of 86.4%, which proves its potential as a photocatalyst.

MIL-53(Fe)@γ-Al2O3 nanocomposites incorporated cellulose acetate for forward osmosis membranes of high desalination performance

Forward osmosis (FO) membrane is a promising membrane technique. However, its application in desalination is limited. Thus, we synthesized MIL-53(Fe)@γ-Al2O3 via solvent-thermal method to fabricate MIL-53(Fe)@γ-Al2O3/cellulose acetate (CA) composite membranes of high desalination performance. MIL-53(Fe)@γ-Al2O3 and MIL-53(Fe) particles were studied using XRD, FITR, SEM, N2 adsorption-desorption isotherms, and AFM. The structural features of MIL-53(Fe)@γ-Al2O3/CA membrane and MIL-53(Fe)/CA membrane were analyzed using SEM, AFM and water contact angle. The reverse salt flux and water flux of the MIL-53(Fe)@γ-Al2O3/CA membrane reached 1.78 g m-2 h-1 and 37.1 L m-2 h-1, respectively, when the deionized water and 1 M NaCl solution were the feed solution and traction solution, respectively. Compared to the MIL-53(Fe)/CA membrane, the MIL-53(Fe)@γ-Al2O3/CA membrane demonstrated better perviousness and selectivity properties of the membrane. This study shows a potential advantage of MOF composites as additives for improvement in the desalination performance of forward osmosis membranes.

Metal–Organic Frameworks: A Robust Platform for Creating Nanoarchitectured Carbon Materials

ConspectusNanoporous carbon (NPC) materials with various architectures have attracted considerable attention because of their distinctive properties and great application potential in environmental remediation, energy conversion and storage, advanced sensors, and other applications. Traditional methods for the synthesis of NPCs, for example, the pyrolysis of natural products or polymers, template-assisted synthesis, and using deep-eutectic solvents, always involve toxic precursors and complex procedures, which greatly hinder further applications. Therefore, it is highly desirable to explore simple and feasible ways to prepare NPCs. Furthermore, to improve the performance and extend the application fields of NPCs, efficient strategies should be developed to regulate the components at the atomic level and construct multidimensional architectures.Metal–organic frameworks (MOFs, also known as porous coordination polymers), which consist of metal ions or clusters and organic ligands, are a new class of porous hybrid materials with reticular structures. As a result, MOFs show interesting characteristics, such as large surface areas, tailored compositions, and structural diversity, which make them ideal platforms for creating functional NPCs. Although significant progress has been made in MOF-derived NPCs with different architectures since the first reported MOF-derived NPC in 2008, this is still an emerging field with inexhaustible potential.In this Account, we highlight the concepts and strategies of our research on MOF-derived NPCs with different architectures, including zero-dimensional (0D) nanopolyhedral, core–shell, and hollow structures, one-dimensional (1D) nanofibers and nanotubes, two-dimensional (2D) nanoflakes and graphene nanomeshes, and three-dimensional (3D) nanoarrays, carbon aerogels, and gradient monoliths. First, we briefly introduce the history of MOFs and discuss their advantages as a platform for the preparation of NPCs. We then summarize the methods for the synthesis of 0D–3D NPCs from MOFs with controllable morphology, composition, and structure. Commonly, two major preparation concepts are involved: direct carbonation of MOFs and pyrolysis of MOF composites. For MOF composites, we have developed (i) electrospinning, (ii) in situ growth, (iii) freeze-drying, and (iv) chemical vapor deposition synthetic strategies for the generation of novel hybrid materials. Additionally, we describe the conversion mechanisms and how to precisely control the architectures in detail. The relationship between the chemical and physical properties of the parent MOFs and derived NPCs is also discussed. The potential applications of MOF-derived NPCs in energy, environmental, and catalysis fields are also demonstrated. Finally, the prospects and challenges for using MOFs as a precursor for designing NPCs are discussed. We believe that this Account will accelerate the development of MOF-derived NPCs and inspire the design and preparation of novel carbon materials.

Significant Enhancement on the Proton Conduction Performance of Composite Membrane by Photoacid Molecules

AbstractMimicking biological proton pump phenomenon to achieve stimulus‐responsive proton conduction behavior has received long‐term attention. The Pa@Zn‐MOF (Pa = photoacids) composites are successfully prepared through adsorption photoacid in Zn‐MOF, then, the composites are mixed into poly(vinyl alcohol) (PVA) to fabricate hybrid membranes Pa@Zn‐MOF‐PVA. When the hybrid membrane is activated through 375 nm violet light at room temperature, the value of proton conductivity after illumination is always superior to that before light irradiation. This phenomenon is attributed to the light‐induced ring‐closing reaction of the photoacid molecules to give the spiro‐forms (SPs) along with an abundant release of protons. The released protons jump into hydrogen bond networks and conveniently accelerate proton transport, resulting in higher proton conductivity. This is a noteworthy demonstration of dynamic control over proton conduction in composite membrane materials by adsorption of photoacid molecules in metal–organic framework.