Metal Organic Framework UiO-66 Research Articles

Green catalysis for the production of n-butyl acetate over phosphotungstic acid-encapsulated metal-organic framework UiO-67 catalyst: Catalyst preparation, characterization and reaction kinetics

In the present study, a composite of Keggin-type phosphotungstic acid encapsulated in sized-matched metal-organic framework UiO-67 (HPW@UiO-67) was successfully fabricated via a facile hydrothermal synthesis method and utilized for the preparation of n-butyl acetate. The as-synthesized composite catalyst was comprehensively characterized using FT-IR, PXRD, ICP-OES, N2 adsorption-desorption, SEM, TEM, NH3-TPD, TGA-DTG and XPS techniques. The characterization results confirmed that HPW was successfully immobilized in metal-organic framework without changing the structure of UiO-67. The asprepared HPW@UiO-67 catalyst exhibited higher esterification activity compared to the UiO-67 catalyst due to its suitable surface area and total volume, high dispersion of phosphotungstic acid and high total acidity. The kinetic study indicated that the process followed the second-order kinetic with the activation energy Ea = 53.1 kJ/mol. The catalyst exhibited good recovery and catalytic performance in the reuse study, maintaining the conversion of acetic acid above 63.1% after four reaction cycles. Moreover, the reaction mechanism for the synthesis of n-butyl acetate via esterification over HPW@UiO-67 was proposed.

Isoreticular Metal-Organic Frameworks Confined Mononuclear Ru-Hydrides Enable Highly Efficient Shape-Selective Hydrogenolysis of Polyolefins.

Upcycling nonbiodegradable plastics such as polyolefins is paramount due to their ever-increasing demand and landfills after usage. Catalytic hydrogenolysis is highly appealing to convert polyolefins into targeted value-added products under mild reaction conditions compared with other methods, such as high-temperature incineration and pyrolysis. We have developed three isoreticular zirconium UiO-metal-organic frameworks (UiO-MOFs) node-supported ruthenium dihydrides (UiO-RuH2), which are efficient heterogeneous catalysts for hydrogenolysis of polyethylene at 200 °C, affording liquid hydrocarbons with a narrow distribution and excellent selectivity via shape-selective catalysis. UiO-66-RuH2 catalyzed hydrogenolysis of single-use low-density polyethylene (LDPE) produced a C12 centered narrow bell-shaped distribution of C8-C16 alkanes in >80% yield and 90% selectivity in the liquid phase. By tuning the pore sizes of the isoreticular UiO-RuH2 MOF catalysts, the distribution of the products could be systematically altered, affording different fuel-grade liquid hydrocarbons from LDPE in high yields. Our spectroscopic and theoretical studies and control experiments reveal that UiO-RuH2 catalysts enable highly efficient upcycling of plastic wastes under mild conditions owing to their unique combination of coordinatively unsaturated single-site Ru-active sites, uniform and tunable pores, well-defined porous structure, and superior stability. The kinetics and theoretical calculations also identify the C-C bond scission involving β-alkyl transfer as the turnover-limiting step.

High efficiency removal of Congo red from wastewater by metal organic framework material UiO-66

Abstract The Zr-based metal organic framework UiO-66 was synthesized using the solvothermal method. The adsorption properties of UiO-66 for organic dye Congo red (CR) were studied. The results showed the excellent adsorption performance of UiO-66 toward CR. The adsorption equilibrium data were consistent with the Langmuir adsorption isotherm model. The adsorption kinetics, thermodynamics, and mechanism of CR on UiO-66 were studied. The results of cyclic adsorption experiments showed that UiO-66 could be used repeatedly to adsorb CR.

One-pot growth of metal-organic frameworks on polymers for catalytic performance enhancement in the CO2 cycloaddition to epoxides

A novel approach is reported to prepare 3D-printed polymers that incorporate metal-organic frameworks (MOFs) through a one-pot growth process, involving covalent grafting and growth onto 3D polymeric surfaces. The resulting hybrid materials were subjected to comprehensive characterization using techniques such as SEM, XRD, FTIR, Raman, and XPS. The findings demonstrated an excellent dispersion of the inorganic units on the polymer matrix while preserving their metal-organic structure. The hybrid materials exhibited the presence of Lewis acid and basic groups within the MOF. The catalytic performance of these hybrid materials was evaluated in the mild cycloaddition reaction of carbon dioxide (CO2) to epoxides. Notably, the polymers incorporating UiO-67 MOFs displayed remarkable activity, even at low CO2 pressures and in the absence of auxiliary co-catalysts or additives. The catalytic activity of these hybrid materials exhibited a significant improvement, up to two orders of magnitude higher than analogous bulk MOFs. This observation highlights the superior performance of the 3D-printed polymer/MOF hybrids in this catalytic transformation.

An iodo-functionalized UiO-67 metal–organic framework for sensing disinfection byproducts

An iodo-functionalized UiO-67 metal–organic framework for sensing disinfection byproducts

The Use of Rapid Precipitation to Synthesise Multivariate UiO-66 Metal–Organic Frameworks for Photocatalysis

A rapid synthesis method is used to form multivariate metal–organic frameworks (MTV-MOFs) with the UiO-66 structure, where precipitation occurs upon mixing solutions of ligands and metal salts at temperatures less than 60 °C. The materials include mixtures of metals and ligands, Ce/Zr-UiO-66(1,4-NDC/BDC), Ce/Zr-UiO-66(1,4-NDC/2,6-NDC), Ce/Zr-UiO-66(1,4-NDC), Ce/Ti-UiO-66(1,4-NDC), and Ce/Ti-UiO-66(BDC-NH2) (NDC = naphthalene dicarboxylate, BDC = benzene-1,4-dicarboxylate, BDC-NH2 = 2-amino-benzene-1,4-dicarboxylate). Phase purity was determined by powder X-ray diffraction (PXRD), with a broadening of the profile indicative of nanoscale crystallites, verified by scanning electron microscopy (SEM). The molar ratio of metals and organic ligands in Ce/Zr-UiO-66(1,4-NDC/2,6-NDC) was confirmed by X-ray fluorescence (XRF) and solution 1H nuclear magnetic resonance (NMR) after digestion, respectively. Analysis of the adsorption of dyes by the MTV-MOFs showed that a pseudo-first-order model accounts for the kinetics. The effectiveness of photocatalytic degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red and Alizarin Red S (AR)) dyes was studied under UV and visible light. The most effective photocatalytic degradation was found between 1 and 15 min towards both cationic and anionic dyes by Ce/Zr-UiO-66(1,4-NDC/2,6-NDC). Measurements of recyclability and photostability showed retention of crystallinity after five cycles of use and exposure to light for 17 h, as confirmed by PXRD.

Memristive behavior of UiO-66 metal-organic framework single crystal

Metal–organic frameworks (MOFs) have recently emerged as a new class of scalable and low energy consumptive materials for microelectronic applications. Here, we experimentally extend the list of MOFs with memristive behavior for electronic data storage. Using 15 µm single crystals of UiO-66 located in 10 µm gap between Au contacts, we demonstrate an electronic set/reset process upon 15 kV cm−1 of an electric field strength under normal conditions. Such low-energy data recording together with an endurance of more than 7 cycles for set/reset opens up prospects for the design of MOF-based electronic and opto-electronic devices.

Facile preparation of metal-organic framework beads for effective capture of indium ion

The adsorption and recovery of indium (In) ions from water is necessary while still faces challenges. Current adsorbents for this valuable metal commonly show powder states, which easily results in mass loss and goes against their convenient recovery. In this work, the nanoscale metal-organic framework UiO-66-(COOH)2 particles were successfully embedded in sodium alginate (SA)-calcium structure, to fabricate UiO-66-(COOH)2/SA composite beads. The beads show a homogenous size of ∼3 mm, cellular-like interior structure, and high MOF loading amount (70.4 wt%). Besides, their high water stability and anti-pressure property were proved. UiO-66-(COOH)2/SA beads exhibit a large adsorption amount for In3+ ions (81.2 mg g−1) and rapid adsorption equilibrium time (∼5 min) at low concentrations. Importantly, it is found that In3+ ions can diffuse into the interior frameworks of the beads via the transparent transmission channels. The optimal pH for adsorption locates at 4.0 and temperature may have only a slight effect. Furthermore, the beads can be regenerated based on a simple solvent elution method. The mechanism analysis confirms that the C–O–C and C–OH (or –COOH) groups from both SA and MOF contents contribute to the adsorption. So, our work provides an effective bead-state adsorbent for In3+ ions.

Developing Mixed Matrix Membranes with Good CO2 Separation Performance Based on PEG-Modified UiO-66 MOF and 6FDA-Durene Polyimide.

The use of mixed matrix membranes (MMMs) comprising metal-organic frameworks (MOFs) for the separation of CO2 from flue gas has gained recognition as an effective strategy for enhancing gas separation efficiency. When incorporating porous materials like MOFs into a polymeric matrix to create MMMs, the combined characteristics of each constituent typically manifest. Nevertheless, the inadequate dispersion of an inorganic MOF filler within an organic polymer matrix can compromise the compatibility between the filler and matrix. In this context, the aspiration is to develop an MMM that not only exhibits optimal interfacial compatibility between the polymer and filler but also delivers superior gas separation performance, specifically in the efficient extraction of CO2 from flue gas. In this study, we introduce a modification technique involving the grafting of poly(ethylene glycol) diglycidyl ether (PEGDE) onto a UiO-66-NH2 MOF filler (referred to as PEG-MOF), aimed at enhancing its compatibility with the 6FDA-durene matrix. Moreover, the inherent CO2-philic nature of PEGDE is anticipated to enhance the selectivity of CO2 over N2 and CH4. The resultant MMM, incorporating 10 wt% of PEG-MOF loading, exhibits a CO2 permeability of 1671.00 Barrer and a CO2/CH4 selectivity of 22.40. Notably, these values surpass the upper bound reported by Robeson in 2008.

UiO-66 metal organic framework as stable platform for non-linear optical applications

We report on the experimental study the non-linear optical properties of UiO-66 metal-organic framework with high thermal and chemical stability. We demonstrate the coherent conversion of high-intensity incoming radiation into the third harmonics ranging from 450 to 600 nm. Moreover, eclipse z - scan of single UiO-66 microcrystals made it possible to determine the saturable absorption coefficient (βeff = −1.415·10-2 cm/GW at 515 nm and −3.865·10-1 cm/GW at 1030 nm), thereby, bringing UiO-66 to the list of nonlinear and stable MOFs for real-life photonic applications.

Microwave-assisted synthesis of metal–organic frameworks UiO-66 and MOF-808 for enhanced CO2/CH4 separation in PIM-1 mixed matrix membranes

This study presents a sustainable microwave-assisted synthesis, based on the use of acetone and a water/acetic acid mixture instead of typical harmful DMF, to fabricate Zr-metal–organic frameworks (MOFs) UiO-66 and MOF-808 as fillers in a PIM-1 matrix for gas separation application. The mixed matrix membranes (MMMs) were prepared with varying loadings (2.5–10 wt%) of MOFs. The physicochemical properties (1H NMR, FTIR, XRD, N2 adsorption, TGA and SEM) of the resulting PIM-1, MOFs and MMMs were analyzed. The CO2/CH4 separation performance and membrane aging characteristics of the MMMs were evaluated. The incorporation of MOF fillers significantly improved CO2 permeability and CO2/CH4 selectivity, attributed to their CO2-philicity and narrow pore size (UiO-66 ≈ 0.6 nm and MOF-808 ≈ 1.8 nm). The MMMs with higher filler loadings (7.5 and 10 wt%) exhibited the most favorable separation performance. Due to the better crystallinity and textural properties, MOF-808 produced the best separation results at 10 wt% filler loading (a CO2/CH4 separation selectivity of 16.2 at 9090 Barrer of CO2 permeability). Aging led to a decrease in CO2 permeability but a slight increase in CO2/CH4 selectivity for all MMMs. Overall, the study highlights the potential of PIM-1/UiO-66 and PIM-1/MOF-808 MMMs as efficient materials for (CO2/CH4) separation comparing with the pristine PIM-1.

Highly Active Electrospinning Electrode Based on MOF for High-Performance Vanadium Flow Batteries

Electrospinning technology has demonstrated excellent prospects in the preparation of structurally controllable functional carbon nanofibers for vanadium flow batteries. However, traditional electrospinning carbon nanofibers used for vanadium flow batteries still suffer from defects in electrochemical activity. Herein, a highly active carbon nanofiber electrode based on metal-organic framework materials has been prepared. The introduction and carbonization of the metal-organic framework UiO-66 in the fibers increase the mesoporous structure of the electrode surface. Additionally, the carbonized UiO-66 forms catalytic ZrO2, which enhances the catalytic activity of the carbon nanofibers. Compared to traditional electrospinning carbon nanofibers, the carbon nanofiber electrode based on metal-organic framework exhibits significantly improved wettability and electrochemical properties, which enhance the mass transfer performance and electrochemical activity. The vanadium flow battery adopting active carbon nanofibers achieves an energy efficiency of 83.33% at 200 mA cm−2, and possesses excellent durability performance with unobvious decay after 1000 charge-discharge cycles at 200 mA cm−2. This study provides guidance for further synthesis of high-performance electrodes for vanadium flow batteries.

Highly stable lead-free perovskite Cs2AgBiBr6/UiO-66 Z-scheme heterostructures with enhanced photocatalytic activity for CO2 photoreduction and organic dyes degradation

Excessive combustion of traditional fossil fuels causes seriously global warming (Carbon dioxide, CO2) and energy crisis. Photocatalytic CO2 conversion to fuels has emerged as one of the most effective strategies. Herein, an environmentally friendly nanocomposite based on lead-free Cs2AgBiBr6 (CABB) perovskite nanocrystals and the UiO-66 metal–organic framework was fabricated by a facile ultrasonic process for efficient CO2 photoreduction. The obtained CABB/UiO-66 consisted of uniform CABB nanocrystals (10–12 nm) attached to the UiO-66 surface and exhibited a high surface area (1031 m2/g). The composite displayed enhanced light-harvesting capacity than the individual components and provided sufficient active sites for promoting photocatalytic activity. A typical Z-scheme heterostructure between the CABB and UiO-66 was realized by forming an inner electric field, leading to the occurrence of efficient excited state charge transfer. The efficient charge transfer of CABB/UiO-66 inspired its use as an active photocatalyst for the reduction of CO2 with significantly improved photocatalytic activity against its individual components. Specifically, CABB/UiO-66 exhibited 38 and 40-fold improvement in catalytic activity compared to respective CABB and UiO-66 in terms of the total yield of CO, CH4, and C2H6. Moreover, the nanocomposite displayed excellent activity towards the oxidative photocatalytic degradation of aqueous environmental contaminant rhodamine B. We believe that this work provides a guide for designing lead-free perovskite-based renewable catalysts and offers new opportunities for the photocatalytic conversion of CO2 photoreduction.

Efficient removal of organic dyes using electrospun nanofibers with Ce-based UiO-66 MOFs

Cerium-based UiO-66 (Ce-UiO-66) metal-organic frameworks (MOFs) were synthesized via a facile solvothermal method and fully characterized using FTIR, XRD, BET, SEM, EDX, and zeta potential techniques. The synthesized Ce-UiO-66 particles were embedded into an electrospun cross-linked polyvinyl alcohol (PVA)/chitosan (CTS) nanofiber (EPCNF), and then employed to remove organic dyes from water. The adsorption results demonstrated that the adsorption capacities of both anionic (Congo Red (CR), Methyl Orange (MO) and Methyl Red (MR)) and cationic (Methylene Blue (MB)) dyes over the fabricated electrospun nanofibers (ENFs) increased with increasing the loadings of Ce-UiO-66 MOFs. Accordingly, the adsorption performance of EPCNF-10 (containing 10 wt% of Ce-UiO-66 MOFs) adsorbent toward these organic dyes is in the order of CR (102.04 mg/g) > MO (87.71 mg/g) > MR (65.35 mg/g) > MB (34.24 mg/g). Moreover, it was found that the Freundlich isotherm model and the pseudo-second-order kinetic model were appropriate for describing the adsorption behaviors of EPCNF-10 adsorbent toward both anionic and cationic dyes. Thus, it can be proposed that the fabricated EPCNF-10 adsorbent would be effective adsorbent materials for the removal of anionic and cationic dyes from water due to its excellent adsorption performance, facile preparation, good regeneration, and simple separation from aqueous solutions.

Prediction of Carbon Dioxide and Methane Adsorption on UiO-66 Metal–Organic Framework via Molecular Simulation

The adsorption equilibrium of methane (CH4) and carbon dioxide (CO2) on the metal–organic framework (MOF) UiO-66 is studied via molecular simulation. UiO-66 is a versatile MOF with vast potential for various adsorption processes, such as biogas upgrading, CO2 capture, and natural gas storage. The molecular simulations employ the grand canonical Monte Carlo (GCMC) method, covering a temperature range of 298–343 K and pressures up to 70 bar for CH4 and 30 bar for CO2. The accuracy of different forcefields in describing the adsorption equilibria is evaluated. Two modelling approaches are explored: (i) lumping each hydrogen atom in the MOF framework to the heavy atom it is bonded to (united atom approximation) and (ii) considering explicit hydrogen atoms. Additionally, the influence of electrical charges on CO2 adsorption is also evaluated. The findings indicate that the most effective forcefield to describe the adsorption equilibrium is a united atom forcefield based on the TraPPE parametrization. This approach also yields an accurate calculation of the isosteric heat of adsorption. In the case of CO2, it is observed that the use of electrical charges enhances the prediction of the heat of adsorption, especially in the low-coverage region.

2-Propanol Dehydration on the Nodes of the Metal–Organic Framework UiO-66: Distinguishing Catalytic Sites for Formation of Propene and Di-isopropyl Ether

2-Propanol Dehydration on the Nodes of the Metal–Organic Framework UiO-66: Distinguishing Catalytic Sites for Formation of Propene and Di-isopropyl Ether

Nanoscale Ag2O decorated UiO-66 metal organic framework for simultaneous electrochemical sensing of heavy metals, Cd2+ and Hg2+

Herein, we come up with a new electrochemical sensing strategy for detecting heavy metal ions present in aqueous media using metal organic framework (MOF) electrode decorated with Ag2O nanoparticles (NPs). Post-synthesis modification route was followed to load the Ag2O NPs into zirconium-based MOF UiO-66 host. In the composite, the NPs were believed to act as the electric current enhancer while UiO-66 provided adsorption sites for heavy metal ions. The ITO electrodes were modified with as prepared composite for the electrochemical detection of Hg2+ and Cd2+ independently as well as simultaneously. The detection of heavy metals was performed by the modified electrodes through differential pulse stripping voltammetry (DPSV) which offered excellent selectivity and with sensitivity values up to 551 μA·μM−1·cm−2 for Cd2+ and 341.2 μA·μM−1·cm−2 for Hg2+. The limit of detection (LOD) for the respective cases, were estimated to be 0.008 μM and 0.003 μM. Technical viability of this approach can be further extended to real sample analysis in soil, river basin, waste land and even ground water for simultaneous detection of heavy metal ions as and when desired.

Heating-induced adsorption promoting the efficient removal of toluene by the metal-organic framework UiO-66 (Zr) under visible light

The removal of indoor/outdoor toluene by photocatalysis has drawn much attention due to its low energy consumption and easy availability. However, light inevitably generates heat, and pollutants desorb from catalysts as the temperature rises, which is not beneficial to degradation. Contrast to the frequently occurred phenomena, we firstly found that the adsorption capacity of UiO-66 (Zr) on toluene increased with increasing temperature as adsorption isotherms and in-situ Fourier transform infrared spectra (in-situ FTIR) showed. The optimum temperature was 30 °C. This stage in which adsorption capacity was positively correlated with temperature was called heating-induced adsorption, which achieved a toluene removal efficiency of 69.6 %. By density functional theory (DFT) calculations and changing the metal centers and organic ligands of UiO-66 (Zr) respectively, we disclosed that the heating-induced adsorption was mainly related to the π-π stacking interaction of MOF ligands and toluene. The analysis of samples before and after adsorption showed that the interaction between UiO-66 (Zr) and adsorbed toluene facilitated the charge transfer and prolonged the carrier lifetime, leading to the increase of hydroxyl radicals (•OH) in photocatalysis. Therefore, a synergistic effect between heating-induced adsorption and photocatalysis was proposed by analyzing the adsorption of toluene on UiO-66 (Zr) in detail. This work provided new viewpoint to understand the role of concomitant heat contributed to the adsorption and degradation of toluene during photocatalysis.

Optimization of Visible-Light-Driven Ciprofloxacin Degradation Using a Z-Scheme Semiconductor MgFe2O4/UiO-67.

A heterogeneous photocatalyst, MgFe2O4/UiO-67 (MU-x), was successfully synthesized by doping magnetic magnesium ferrite nanoparticles (MgFe2O4) with the UiO-67 metal-organic framework at various weight ratios (MgFe2O4: UiO-67 at 30, 50, 70, and 90 wt %). Various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) , Brunauer-Emmett-Teller (BET), photoluminescence (PL), vibrating sample magnetometry (VSM), electrochemical impedance spectroscopy (EIS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), were used to characterize the prepared photocatalysts. The photocatalytic performance of MU-x in the degradation of ciprofloxacin (CIP) under visible light was assessed. The CIP degradation efficiency was found to increase as the amount of MgFe2O4 in the composite was increased up to 70 wt %. Experimental conditions were optimized using response surface methodology (RSM) based on central composite design (CCD) with three factors: initial pH, catalyst loading, and CIP concentration. Using the obtained model, the optimal conditions were determined as follows: initial pH of 8.025, catalyst loading of 33.8 wt %, and CIP concentration of 10.8 mg/L. Under these optimal conditions, a notable improvement was achieved, with 99.62% of CIP removal achieved within 90 min, surpassing the performance of previously reported photocatalysts. Total organic carbon (TOC) analysis revealed a high degree of mineralization, at 81.25%. The degradation pathway of CIP was investigated based on liquid chromatography-mass spectrometry (LC-MS) analysis. Finally, the values of ECB and EVB of the photocatalyst were determined and the possible degradation mechanism of CIP was investigated based on Mott-Schottky and the applied scavengers. The hydroxyl radical (•OH) was identified as the dominant species in the removal of CIP through a trapping experiment. The photocatalyst with 70 wt % of MgFe2O4 (MU-70) exhibited excellent stability and recoverability with an external magnet, demonstrating 86.33% CIP removal after four cycles. According to the obtained results, MU-70 is a promising visible-light-active photocatalyst with great potential for water treatment applications and convenient recovery.

Incorporating of Cobalt into UiO-67 Metal–Organic Framework for Catalysis CO2 Transformations: An Efficient Bi-functional Approach for CO2 Insertion and Photocatalytic Reduction

Incorporating of Cobalt into UiO-67 Metal–Organic Framework for Catalysis CO2 Transformations: An Efficient Bi-functional Approach for CO2 Insertion and Photocatalytic Reduction