UiO-66 Materials Research Articles

Low pressure-drop CuO/CeO2/UiO-66 catalysts for H2 purification

Pressure drop is responsible of a great part of the energy cost in industry due the energy consumed by pumps driving a fluid through the installation, and heterogeneous catalysis industrial processes suffer from this pressure drop penalty. This study demonstrates that UiO-66 significantly improves the catalytic performance of the CuO/CeO2 active phase for preferential CO oxidation in H2 streams with regard to a conventional γ-Al2O3 carrier due to the particular porous and crystalline properties of MOF materials. A packed bed of UiO-66 produces very low-pressure drop in comparison to conventional catalytic carriers, such as γ-Al2O3 or beta zeolite, being 4 times lower for UiO-66 than for γ-Al2O3 under 2 L/min flow of N2, and this ratio increases and approaches ∞ for lower gas flow rates. This feature of UiO-66 not only decreases the energy required to pump gases through the catalytic bed, but also improves catalytic performance of UiO-66-supported catalysts due to the enhanced gas diffusion into the catalytic bed. The reaction gases flow through the interparticle space left by the catalyst in a packed bed of CuO/CeO2/γ-Al2O3, and this produces high pressure drop, preferential gas pathways and mass transport limitations, negatively affecting the reaction rate. On the contrary, the reaction gases are able to flow through the UiO-66 material without channel constrictions, and the CuO/CeO2/UiO-66 catalysts avoid the gas diffusion restrictions of conventional catalysts.

Cerium-Organic Framework UiO-66(Ce) as a Support for Nanoparticulate Gold for Use in Oxidation Catalysis.

An optimised synthesis of the metal-organic framework (MOF) UiO-66(Ce) is reported using a modulator-free route, yielding ~5 g of material with high crystallinity and 22% ligand defect. Two methods developed for loading gold nanoparticles onto the MOF. The first uses a double-solvent method to introduce HAuCl4 onto UiO-66(Ce), followed by reduction under 5% H2 in N2, while the second is a novel one-pot method where HAuCl4 is added to the synthesis mixture, forming Au nanoparticles within the pores of the UiO-66(Ce) during crystallisation. Analysis using powder X-ray diffraction (PXRD), nitrogen adsorption isotherms, transmission electron microscopy and small-angle X-ray scattering (SAXS) reveals that the two-step double-solvent method yields gold crystallites on the external surface of the MOF particles that are visible by PXRD. In contrast, the one-pot method forms smaller gold crystallites, with a distribution of sizes centred on ~4 nm diameter as seen by SAXS, with evidence from PXRD for the smallest particles being present within the MOF structure. The Au-loaded UiO-66(Ce) materials are evaluated for the catalytic oxidation of vanillyl alcohol to vanillin at 60 °C. Our findings indicate that incorporating Au nanoparticles via the one-pot synthesis method, enhances redox activity, achieving 43% conversion and 90% selectivity towards vanillin.

Catalytic Advantages of SO3H-Modified UiO-66(Zr) Materials Obtained via Microwave Synthesis in Friedel-Crafts Acylation Reaction.

The catalytic activity and stability of sulfonic-based UiO-66(Zr) materials were tested in the Friedel-Crafts acylation of anisole with acetic anhydride. The materials were prepared using microwave-assisted synthesis, producing microporous materials with remarkable crystallinity and physicochemical features as acid catalysts. Different ratios between both organic ligands, terephthalic acid (H2BDC) and monosodium 2-sulfoterephthalic acid (H2BDC-SO3Na), were used for the synthesis to modulate the sulfonic content. The sulfonic-based UiO-66(Zr) material synthesized with a H2BDC/H2BDC-SO3Na molar ratio of 40/60 exhibited the best catalytic performance in the acidic-catalyzed Friedel-Crafts acylation reaction. This ratio balanced the number of sulfonic acid sites and their accessibility within the UiO-66 microporous structure. The catalytic performance of this material increased remarkably at 200 °C, outperforming reference acids and commercial heterogeneous catalysts such as Nafion-SAC-13 and Amberlyst-70. Additionally, the best sulfonic-based UiO-66(Zr) material proved to be stable in four successive reaction cycles, maintaining both its catalytic activity and its structural integrity.

Complete chromium removal via photocatalytic reduction and adsorption using bimetallic UiO-66(Zr/Al)

Photocatalytic reduction is a widely researched method for removing heavy metal ions from water. This study successfully synthesized Zr-based bimetallic UiO-66(Zr/Al) materials via a solvothermal method, incorporating aluminum (Al) into the Zr-UiO-66 lattice. Characterization confirmed successful Al(III) doping without altering the fundamental framework. Among the synthesized materials, UZA-6 exhibited remarkable photocatalytic activity, achieving a 99.25 % removal rate of hexavalent chromium (Cr(VI)) from water within 60 min under simulated solar irradiation. Additionally, the catalyst effectively adsorbed the reduced trivalent chromium (Cr(III)) and maintained a removal rate of 97.73 %, thereby achieving complete removal of Cr element in water. Photoluminescence and electrochemical analyses revealed that the enhanced photocatalytic performance was due to improved separation of photogenerated electron-hole pairs and facilitated charge transfer, attributed to Al doping. This research offers valuable insights into developing effective MOF-based catalysts for water purification, highlighting the potential of UZA-6 for efficiently removing both Cr(VI) and Cr(III) from contaminated water.

Impact of the material hydroxylation on the possibility of pentane isomers separation by UiO-66 (Zr) MOF: A combined 2H NMR and MD study

The mobility of the pentane isomers in the hydroxylated UiO-66 metal-organic framework has been characterized. 2H NMR spectroscopy was applied to measure the jump rate of alkanes guest molecules between adjacent cages and estimate the diffusivity. It is inferred that the difference in diffusion coefficients defines the kinetic separation selectivity, which is higher for the linear alkanes. The adsorption of pentane isomers in UiO-66 has been modeled with molecular dynamics (MD) simulation. The adsorbed quantity of isopentane is higher than that for n-pentane, providing the possibility of separation with selectivity α ≈ 8 in stationary conditions. The impact of the UiO-66 MOF hydroxylation state on the mobility of pentane isomers has been characterized by comparison with results obtained for the dehydroxylated UiO-66 material. The hydroxylated state of UiO-66 MOF has 6-time higher separation selectivity for pentane isomers compared to its dehydroxylated state (αhyd ≈ 76). MD calculations show that hydroxylated UiO-66 MOF is more efficient, as the separation selectivity is 4 times lower in the dehydroxylated material. The UiO-66 hydroxylation effect is compared for the mobility of C4 and C5 alkanes. The optimal conditions for C4/C5 alkanes kinetic separation by UiO-66 MOF are established.

Recent Progress in the Applications of UIO-66 Materials: A Review

The integration of different disciplines is the core of the application orientation of UIO-66 materials, and it has expanded the boundaries of the application field of UIO-66 materials by exploring infinite space in chemical composition and material properties. Significant advancements have been achieved in utilizing the distinct characteristics of UIO-66 materials, both in basic and practical terms. In this review, our aim is to examine the key achievements in utilizing UIO-66 materials, encompassing areas like gas separation, catalysis, quartz crystal microbalance sensor and energy storage, and offer an essential viewpoint on their progress in practical applications. Finally, we succinctly address the primary obstacles that must be tackled in these domains to lay the groundwork for industrial utilization.

A Protective Layer of UIO-66/Reduced Graphene Oxide to Stabilize Zinc-Metal Anodes toward High-Performance Aqueous Zinc-Ion Batteries.

Rechargeable aqueous Zn-ion batteries with a Zn anode hold great promise as promising candidates for advanced energy storage systems. The construction of protective layer coatings on Zn anode is an effective way to suppress the growth of Zn dendrites and water-induced side reactions. Herein, we reported a series of UIO-66 materials with different concentrations of reduced graphene oxide (rG) coated onto the surface of Zn foil (Zn@UIO-66/rGx; x = 0.05, 0.1, and 0.2). Benefiting from the synergistic effect of UIO-66 and rG, symmetric cells with Zn@UIO-66/rGx (x = 0.1) electrodes exhibit excellent reversibility (e.g., long cycling life over 1100 h at 1 mA cm-2/1 mAh cm-2) and superior rate capability (e.g., over 1100 and 400 h at 5 mA cm-2/2.5 mAh cm-2 and 10 mA cm-2/5 mAh cm-2, respectively). When the Zn@UIO-66/rG0.1 anode was paired with the NaV3O8·1.5H2O (NVO) cathode, the Zn@UIO-66/rG0.1||NVO cell also delivered a high reversible capacity of 189.9 mAh g-1 with an initial capacity retention of 61.3% after 500 cycles at 1 A g-1, compared to the bare Zn||NVO cell with only 92 cycles.

Efficient Charge Transfer of p-n Heterojunction UiO-66-NH2/CuFe2O4 Composite for Photocatalytic Hydrogen Production

Using a p-n heterojunction is one of the efficient methods to increase charge transfer in photocatalysis applications. So, herein, p-type UiO-66 (NH2) and n-type CuFe2O4 (CFO) are used to form an effective p-n heterojunction. Due to their poor charge separation in their pristine form, both UiO-66 (NH2) and CFO materials cannot produce hydrogen; however, the composite p-n heterojunction formed between these materials makes fast charge separation and so hydrogen is efficiently produced. The optimized catalyst UCFO 25% produces a maximum of 62.5 µmol/g/h hydrogen in an aqueous methanol solution. The formation of a p-n heterojunction is confirmed by Mott–Schottky analysis and optical properties, crystallinity and the local atomic environment of the material was analyzed by various analytical tools like UV-Vis spectroscopy, XRD, and XANES.

UiO-66(Zr) as drug delivery system for non-steroidal anti-inflammatory drugs

The toxicity for the human body of non-steroidal anti-inflammatory drugs (NSAIDs) overdoses is a consequence of their low water solubility, high doses, and facile accessibility to the population. New drug delivery systems (DDS) are necessary to overcome the bioavailability and toxicity related to NSAIDs. In this context, UiO-66(Zr) metal-organic framework (MOF) shows high porosity, stability, and load capacity, thus being a promising DDS. However, the adsorption and release capability for different NSAIDs is scarcely described. In this work, the biocompatible UiO-66(Zr) MOF was used to study the adsorption and release conditions of ibuprofen, naproxen, and diclofenac using a theoretical and experimental approximation. DFT results showed that the MOF-drug interaction was due to an intermolecular hydrogen bond between protons of the groups in the defect sites, (μ3 − OH, and − OH2) and a lone pair of oxygen carboxyl functional group of the NSAIDs. Also, the experimental results suggest that the solvent where the drug is dissolved affects the adsorption process. The adsorption kinetics are similar between the drugs, but the maximum load capacity differs for each drug. The release kinetics assay showed a solvent dependence kinetics whose maximum liberation capacity is affected by the interaction between the drug and the material. Finally, the biological assays show that none of the systems studied are cytotoxic for HMVEC. Additionally, the wound healing assay suggests that the UiO-66(Zr) material has potential application on the wound healing process. However, further studies should be done.

A Multi-Functional Fluorescence Sensing Platform Based on a Defective UiO-66 for Tetracycline and Moxifloxacin

In recent years, the excessive use and disordered discharge of antibiotics have had sustained adverse effects on ecological balance and human health. The convenient and effective detection of these “emerging pollutants” has become one of the research hotspots in the environmental field. In this study, a defective UiO-66 material, namely UiO-66-D, was constructed for the sensitive and selective sensing of tetracycline (TC) and moxifloxacin (MXF) in water. By utilizing a modulated synthesis approach with concentrated HCl, stable blue fluorescence at 400 nm was achieved for UiO-66-D. The as-prepared UiO-66-D could conduct the inner filter effect (IFE) within a short time (10 s) when sensing TC and MXF, and the fluorescence of the UiO-66-D was quenched. In particular, when sensing MXF, a ratiometric signal response was generated due to the combined effect of the IFE and the fluorescence of MXF itself. The sensitive and selective detection of TC and MXF using UiO-66-D was free from the interference of common anions and cations in water samples. The detection limit (LOD) for TC was determined to be 70.9 nM (0–115 μM), while for MXF, it was found to be 33.1 nM (0–24 μM). Additionally, UiO-66-D was successfully used to recognize TC and MXF in lake water with good recoveries, demonstrating that UiO-66-D exhibits substantial potential in the recognition of pollutants in environmental waters.

Preparation of the N, P-Codoped Carbonized UiO-66 Nanocomposite and Its Application in Supercapacitors.

Preparing high-performance electrode materials from metal-organic framework precursors is currently a hot research topic in the field of energy storage materials. Improving the conductivity of such electrode materials and further increasing their specific capacitance are key issues that must be addressed. In this work, we prepared phosphoric acid-functionalized UiO-66 material as a precursor for carbonization, and after carbonization, it was combined with activated carbon to obtain nitrogen-/phosphorus-codoped carbonized UiO-66 composite material (N/P-C-UiO-66@AC). This material exhibits excellent conductivity. In addition, the carbonized product ZrO2 and the nitrogen-/phosphorus-codoped structure evidently improve the pseudocapacitance of the material. Electrochemical test results show that the material has a good electrochemical performance. The specific capacitance of the supercapacitor made from this material at 1.0 A/g is 140 F/g. After 5000 charge-discharge cycles at 10 A/g, its specific capacitance still remains at 88.5%, indicating that the composite material has good cycling stability. The symmetric supercapacitor assembled with this electrode material also has a high energy density of 11.0 W h/kg and a power density of 600 W/kg.

Defective UiO-66 by metal doping for highly efficient photocatalytic degradation of methyl mercaptan

Defective UiO-66 by metal doping exhibits considerable promise in the photocatalytic degradation of environmental contaminants, albeit how different metal doping affect formation of defects and its efficacy in the degradation of methyl mercaptan has yet to be comprehensively explored. In this study, a one-step solvothermal method was employed to successfully synthesize six distinct metal-doped UiO-66 with variations of defects by incorporating Ce, Al, Cu, Cr, Mg, and Fe. A systematic examination of the structural and photochemical attributes of these metal-doped UiO-66 materials was conducted through a series of characterisations. Metal doping creates defects in UiO-66, changes its colour and morphology and increases its specific surface area. Subsequently, the adsorption and photocatalytic degradation characteristics of these nanomaterials concerning methyl mercaptan were investigated. In comparison to pristine UiO-66, all metal-doped UiO-66 variants exhibited enhanced adsorption and photocatalytic degradation capabilities towards methyl mercaptan. Notably, among the prepared materials, FeUiO-66 demonstrated the most exceptional photocatalytic degradation performance, followed by CuUiO-66, AlUiO-66, CeUiO-66, CrUiO-66, and MgUiO-66 in that order. 1.0FeUiO-66 exhibiting the most remarkable performance, achieving a 99 % degradation of methyl mercaptan within 30 min. This represented a degradation rate 36.8 times higher than that of pure UiO-66, attributable to the incorporation of low-valence metals into the UiO-66 framework, resulting in the creation of oxygen vacancy defects. Furthermore, the presence of these metals facilitated electron transport, thereby enhancing the efficiency of photocatalytic degradation. This study underscores the potential of various metals-doped UiO-66 for adsorption and photocatalytic elimination of methyl mercaptan.

Controllable Synthesis of Defective UiO-66 for Efficient Degradation and Detection of Ozone.

Metal-organic framework (MOF) structures have gained significant attention for their exceptional catalytic performance in ozone degradation, even under high humidity conditions, which is attributed to the presence of unsaturated metal sites (MOF defects). However, the correlation between MOF defects and catalytic ozone remains ambiguous, and a general approach for the controllable synthesis of high-performance MOF structures is currently lacking. Herein, different defective UiO-66 materials with cluster or ligand defects were obtained by precisely controlling small molecular acid modulators. Their catalytic performance can be analyzed in real time through the specific cataluminescence (CTL) signal of ozone at the interface. The presence of ligand defects was found to be crucial for both catalytic degradation and luminescence of ozone, and the CTL signal exhibited a positive correlation with the endogenous hydroxyl group content in the material (R2 = 0.982), while external humidity further supplemented internal water molecules within the material. Furthermore, theoretical calculations were conducted to compare the adsorption behaviors of ozone on the defective UiO-66 under dry/wet conditions, leading to the proposal of two potential reaction pathways. Subsequently, UiO-66-DA with superior catalytic performance was employed to develop a highly efficient CTL sensor capable of accurately detecting ozone (LOD = 23.3 ppb). This study held significant value in elucidating the reaction site of ozone on MOFs and achieving optimal catalytic effects through the careful selection of modulators and humidity levels.

Structure optimization and support effect of metal-organic frameworks on Pd-Ir bimetallic nanoclusters

Structure optimization of metal nanoclusters supported on metal-organic framework (MOFs) materials is very important for understanding and improving their both catalytic activity and selectivity. In this paper, a systematic study on the structure optimization of Pd-Ir bimetallic nanoclusters on MOFs (UiO-66) is presented based on basin hopping genetic algorithm (BHGA) and density functional theory (DFT) calculation. In addition, the structural characteristics, electronic properties and the support effect of UiO-66 on Pd-Ir nanoclusters are explored by analyzing the adsorption energy, binding energy, skeleton deformation energy and charge transfer. The results show that Pd-Ir clusters tend to bind with organic connectomes and remain thermodynamically stable near the support site. Meanwhile, among the three Pd-Ir alloy clusters supported on UiO-66, Pd32Ir6 cluster has the strongest interaction with UiO-66 framework, while Pd6Ir32@UiO-66 has excellent thermodynamic stability. Importantly, the catalytic efficiency of Pd-Ir@UiO-66 is improved owing to the transferred electrons from Pd-Ir alloy clusters to UiO-66 framework. Furthermore, with the support effect of UiO-66 on Pd-Ir clusters, the Pd-Ir clusters dispersed in the UiO-66 pores to prevent metal clusters from agglomeration, but their thermodynamic stability are not changed after supporting on UiO-66 materials. In addition, the coordination number of Pd/Ir atoms in Pd-Ir clusters becomes fewer due to the support effect of UiO-66 on Pd-Ir nanoclusters. Moreover, the Pd-Ir clusters are firmly adsorbed on UiO-66, which contributes to improve the catalytic activities of Pd-Ir@UiO-66.

Solvent-Treated Zirconium-Based Nanoporous UiO-66 Metal–Organic Frameworks for Enhanced CO2 Capture

Metal–organic framework (MOF)-derived nanoscale porous materials are widely deployed in carbon capture, but the CO2 capacity is varied by different post-treatments, and its mechanism is still unclear. Herein, we prepared UiO-66 and treated it with methanol solvent and thermal activation approaches, which showed ∼3 times enhanced CO2 capacities from 15.1 to 45.0 mg/g and excellent recyclability of 10 cycles. The methanol treatment efficiently removes the residual guest molecules, including N,N-dimethylformamide, dangling organic linkers, and their derivatives, in the micropores (∼0.8 nm) of UiO-66 and improves the surface area, pore volume, and void fraction to enhance the CO2 capacity close to the ideal UiO-66 materials. The molecular dynamics simulation also proved a good linear relationship between the surface areas, void fraction, and CO2 capacity. This work provides a deep understanding of the MOF’s activation mechanism and its applications in CO2 capture.

The Boost of Toluene Capture in UiO-66 Triggered by Structural Defects or Air Humidity.

This work aimed to investigate the adsorption of toluene in UiO-66 materials. Toluene is a volatile, aromatic organic molecule that is recognized as the main component of VOCs. These compounds are harmful to the environment as well as to living organisms. One of the materials that allows the capture of toluene is the UiO-66. A satisfactory representation of the calculated isotherm steep front and sorption capacity compared to the experiment was obtained by reducing the force field σ parameter by 5% and increasing ε by 5%. Average occupation profiles, which are projections of the positions of molecules during pressure increase, as well as RDFs, which are designed to determine the distance of the center of mass of the toluene molecule from organic linkers and metal clusters, respectively, made it possible to explain the mechanism of toluene adsorption on the UiO-66 material.

Absorbing stress via molecular crumple zones: Strain engineering flexibility into the rigid UiO-66 material

Absorbing stress via molecular crumple zones: Strain engineering flexibility into the rigid UiO-66 material

One-Step Synthesis of Al-Doped UiO-66 Nanoparticle for Enhanced Removal of Organic Dyes from Wastewater

In this study, a series of Al-doped metal-organic frameworks (AlxZr(1-x)-UiO-66) were synthesized through a one-step solvothermal method. Various characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and N2 sorption measurement, suggested that the Al doping was uniform and barely influenced the crystallinity, chemical stability, and thermal stability of the materials. Two cationic dyes, safranine T (ST) and methylene blue (MB), were selected for investigating the adsorption performances of Al-doped UiO-66 materials. Al0.3Zr0.7-UiO-66 exhibited 9.63 and 5.54 times higher adsorption capacities than UiO-66, 498 mg/g and 251 mg/g for ST and MB, respectively. The improved adsorption performance can be attributed to π-π interaction, hydrogen bond, and the coordination between the dye and Al-doped MOF. The pseudo-second-order and Langmuir models explained the adsorption process well, which indicated that the dye adsorption on Al0.3Zr0.7-UiO-66 mostly occurred through chemisorption on homogeneous surfaces. A thermodynamic study indicated the adsorption process was spontaneous and endothermic. The adsorption capacity did not decrease significantly after four cycles.

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

Ultrahigh current output from triboelectric nanogenerators based on UIO-66 materials for electrochemical cathodic protection

Metals are the basic and key components of most of the stuff present all around us in our living environment. The corrosion of these metals is a natural phenomenon which can be avoided through application of electrochemical cathodic protection. The triboelectric nanogenerator (TENG) is used to convert the environmental energy into electric energy. Unfortunately, the current output of TENG is always lower which limits its applications in protection of metal corrosion. In this work, we report the fabrication of efficient TENG based on UIO-66, UIO-66-NO2 and UIO-66-NH2, and use it as a power supply to construct a self-powered anticorrosion system for cathodic protection on carbon steel. The introduction of nitrate (-NO2) and amine (-NH2) groups change the Fermi level of the material, allowing the TENG to transfer more electrons during the contact. It is observed that the performance of TENG based on UIO materials is fruitful, with a maximum short-circuit current as 50.0 μA and a maximum power as 122.5 μW·cm−2. In addition, dipping experiments and electrochemical measurements showed that the TENG is capable to offer notable cathodic protection to carbon steel. The demonstrated work introduces an efficient and cost-effective strategy for scavenging the mechanical energy from environment by employing the self-powered setup to effectually protect the metals from corrosion. The assembly of auspicious self-powered cathodic protection setup based on TENG offers a great potential for versatile applications in protection of metallic corrosion activities.