Zirconium Metal Organic Framework Research Articles

Preparation and application of a nanocomposite of dopamine modified zirconium metal organic framework and polythiophene for solid-phase microextraction/gas chromatography of phenols released from polycarbonate materials

The zirconium metal-organic framework (MOF) UiO-66 was modified by dopamine (DA) and electrodeposited with Poly (3,4-ethylenedioxothiophene) (PEDOT) on an etched stainless steel wire to prepare a UiO-66-DA/PEDOT nanocomposite coating. The coating was characterized by scanning electron microscopy, energy dispersive spectrometer, Fourier transform infrared and thermogravimetric analysis, respectively. The coating has high specific surface area and more porous structure, which can be used to extract eight phenols, including 2-chlorophenol, o-cresol, m-cresol, 2, 4-dichlorophenol, 4-tert-butylphenol, 4-chlorophenol, 4-tert-octylphenol and α-naphthol. The adsorption behavior of the phenols on the UiO-66-DA/PEDOT coating had significant correlation with Langmuir isothermal model. A determination method for the eight phenols was established by combining with direct immersion solid-phase micro extraction and gas chromatography. Under the optimal experimental conditions, the detection linear range (LRs) was 0.05–50 μg mL−1 and the detection limit (LODs) was 0.01–0.08 μg mL−1 (S/N = 3). The method was applied for the migration detection of eight phenols in polycarbonate cups, which showed satisfactory recovery.

Structure Tuning of Hafnium Metal–Organic Frameworks through a Mixed Solvent Approach

The recent development of water-stable metal–organic frameworks (MOFs) has significantly broadened the application scope of this emerging type of porous material. Structure tuning of hafnium MOFs is less studied compared with zirconium MOFs. In this work, we report the synthesis of a mesoporous hafnium MOF, csq-MOF-1, through finely tuning the solvent mixture ratio. The successful synthesis of csq-MOF-1 also relies on the linker flexibility as linker bending and a symmetry decrease were observed in this framework as compared to its structural isomer NPF-300 (Hf). The mesoporous feature and permanent porosity were determined by the N2 adsorption at 77 K. Such a hierarchical pore feature is expected to enable a variety of applications through encapsulation of large functional molecules. The synthetic strategy of utilizing a mixed solvent and flexible linker is expected to inspire the development of new hafnium MOFs with diverse topological structures.

A Porous Sulfonated 2D Zirconium Metal-Organic Framework as a Robust Platform for Proton Conduction.

By using the strategy of pre-assembly chlorosulfonation applied to a linker precursor, the first sulfonated zirconium metal-organic framework (JUK-14) with two-dimensional (2D) structure, was synthesized. Single-crystal X-ray diffraction reveals that the material is built of Zr6 O4 (OH)4 (COO)8 oxoclusters, doubly 4-connected by angular dicarboxylates, and stacked in layers spaced 1.5 nm apart by the presence of sulfonic groups. JUK-14 exhibits excellent hydrothermal stability, permanent porosity confirmed by gas adsorption studies, and shows high (>10-4 S/cm) and low (<10-8 S/cm) proton conductivity under humidified and anhydrous conditions, respectively. Post-synthesis inclusion of imidazole improves the overall conductivity increasing it to 1.7×10-3 S/cm at 60 °C and 90 % relative humidity, and by 3 orders of magnitude at 160 °C. The combination of 2D porous nature with robustness of zirconium MOFs offers new opportunities for exploration of the material towards energy and environmental applications.

Zr-MOFs–catalyzed transfer hydrogenation of furfural to furfuryl alcohol: Unveiled performance of DUT-52

Catalytic transfer hydrogenation (CTH) of 2-furfuraldehyde (FALD) at 1 atm has potential industrial applications to produce furfuryl alcohol (FOL) and its derivatives mildly. The process was explored using alcohols in the absence of H2. Solvothermally prepared zirconium(IV) metal organic frameworks (Zr-MOFs) of DUT-52 (DUT: Dresden University of Technology) and UiO-66 (UiO: University of Oslo) were employed in the CTH. Energetic studies (GFN2-xTB level) revealed a similar Gibbs free energy of DUT-52 and UiO-66 when they were reacted by 2-propanol. Electrostatic potential (ESP) charges and Wiberg bond order (WBO) calculations showed that two Zr atoms available for FALD coordination had higher Lewis acidity in DUT-52 than UiO-66. DUT-52 successfully gave >99% of FOL in 3 h at 160 °C under 2-propanol with Ea of 61 kJ/mol and an equal turnover frequency (TOF) to UiO-66 (5.4 h−1). DUT-52 was also easily recyclable up to the 4th run with no significant performance loss.

Lipid membrane anchoring and highly specific fluorescence detection of cancer-derived exosomes based on postfunctionalized zirconium-metal-organic frameworks

Cancer-derived exosomes carry a variety of important biomarkers specific to the formation, invasion and metastasis of tumor tissue. Dynamic monitoring of exosomes originated from cancer cells has clinical significance. Here we proposed a novel method to employ zirconium-metal-organic frameworks (Zr-MOFs) for extracting and identifying exosomes from blood. At first UiO-66 was magnetically modified as the adsorbent to anchor exosomes by forming Zr–O–P bonds. Then UiO-66-NH2 modified with anti-EpCAM was used to construct the fluorescent probe to recognize the extracted EpCAM-positive exosomes by forming a “MOF-exosome-MOF” structure. The proposed fluorescence detection method was evaluated by quantifying MCF-7 cell-derived exosomes at the concentration as low as 16.72 particles/μl. This method was successfully applied to analyze exosomes in the plasma samples from healthy donors and breast cancer patients, demonstrating that our method might have a great potential in assisting the early diagnosis and in dynamically monitoring the efficacy of cancer treatment. We believe that the method could be extended to the detection of other biomarkers in exosomes derived from cancer cell.

A strongly hydrophobic ethane-selective metal-organic framework for efficient ethane/ethylene separation

The removal of ethane (C2H6) from ethylene (C2H4) is of great importance to afford polymer-grade C2H4 with purity greater than 99.95% as feedstock to produce polyethylene. Adsorptive separation with C2H6-selective metal-organic frameworks (MOFs) can directly produce high-purity C2H4, which has shown bright prospects for replacing the energy-intensive cryogenic distillation. Herein, we demonstrate a robust zirconium MOF possessing hydrophobic pores and oxygen-rich groups, namely MOF-841, can preferentially adsorb C2H6 over C2H4. Experimental adsorption isotherms and breakthrough show high separation performance for the gas mixture of C2H6 and C2H4 due to ultrahigh C2H6 uptake capacity (4.7 mmol/g) and distinctive C2H6/C2H4 uptake ratio (1.35) of MOF-841 at 298 K and 100 kPa. Computational studies reveal that aromatic rings and carboxylate oxygen atoms pointing towards the pore ascribed to trapping C2H6 through synergistic effects arising from multiple van der Waals interactions including C-H∙∙∙π and C-H···O, which are more potent than C2H4-framework interactions.

Zirconium-organic framework as a novel adsorbent for arsenate remediation from aqueous solutions

The removal of arsenic species in water is a global challenge due to its high toxicity and carcinogenicity. In this work, a stable zirconium metal-organic framework (Zr-MOF) has been synthesized for As(V) removal. The Zr-MOF adsorbed As(V) effectively in the pH range of 4–9 with the maximum adsorption capacity of 278 mg g−1. The experimental data modelling suggested a spontaneous adsorption process involving physicochemical forces. The spectroscopic analysis confirmed the binding of As(V) on the Zr-sites via a ligand-exchange mechanism involving ZrOH. Another possible mechanism was the interaction of As(V) with the dissociation of ZrO(linker) sites. These mechanisms were further confirmed by theoretical calculations, where the Zr(μ3-O) bridges (binding energy ∼4.38 eV) bind As(V) more strongly than the ZrOC linkages (binding energy ∼4.11 eV). The material regeneration was successfully carried out with HCl solution, where the regeneration efficacy remained ∼90% for five cycles. Thus, the study provided a detailed investigation on the As(V) adsorption over Zr-MOF.

Zirconium(IV) Metal Organic Frameworks with Highly Selective Sorption for Diclofenac under Batch and Continuous Flow Conditions

Diclofenac (DCF) is among the most effective non-steroidal anti-inflammatory drugs (NSAIDs) and at the same time one of the most consumed drugs worldwide. Since the ever-increasing use of diclofenac poses serious threats to ecosystems, its substantial removal is crucial. To address this issue, a variety of sorbents have been employed. Herein we present the diclofenac removal properties of two metal organic frameworks, namely [Zr6O4(OH)4(NH2BDC)6]·xH2O (MOR-1) and H16[Zr6O16(H2PATP)4]·xH2O (MOR-2). Batch studies revealed fast sorption kinetics for removal of DCF− from water as well as particularly high selectivity for the drug vs. common competitive species. Moreover, the composite MOR-1-alginic acid material was utilized in a sorption column, displaying remarkable removal efficiency towards DCF− anions. Significantly, this is the first time that column sorption data for removal of NSAIDs using MOF-based materials is reported.

A zirconium metal-organic framework with SOC topological net for catalytic peptide bond hydrolysis

The discovery of nanozymes for selective fragmentation of proteins would boost the emerging areas of modern proteomics, however, the development of efficient and reusable artificial catalysts for peptide bond hydrolysis is challenging. Here we report the catalytic properties of a zirconium metal-organic framework, MIP-201, in promoting peptide bond hydrolysis in a simple dipeptide, as well as in horse-heart myoglobin (Mb) protein that consists of 153 amino acids. We demonstrate that MIP-201 features excellent catalytic activity and selectivity, good tolerance toward reaction conditions covering a wide range of pH values, and importantly, exceptional recycling ability associated with easy regeneration process. Taking into account the catalytic performance of MIP-201 and its other advantages such as 6-connected Zr6 cluster active sites, the green, scalable and cost-effective synthesis, and good chemical and architectural stability, our findings suggest that MIP-201 may be a promising and practical alternative to commercially available catalysts for peptide bond hydrolysis.

Interfacial Reduction Nucleation of Noble Metal Nanodots on Redox-Active Metal-Organic Frameworks for High-Efficiency Electrocatalytic Conversion of Nitrate to Ammonia.

Electrochemically converting nitrate to ammonia is a promising route to realize artificial nitrogen recycling. However, developing highly efficient electrocatalysts is an ongoing challenge. Herein, we report the construction of stable and redox-active zirconium metal-organic frameworks (Zr-MOFs) based on Zr6 nanoclusters and redox-reversible tetrathiafulvalene (TTF) derivatives as inorganic nodes and organic linkers, respectively. The redox-active Zr-MOF can facilitate the in situ reduction of noble metal precursors free of external reductants and realize the uniform nucleation of noble metal nanodots (NDs) on Zr-MOF, achieving the preparation of M-NDs/Zr-MOF (M = Pd, Ag, or Au). The highly porous Zr-MOF with good conductivity can facilitate the mass transfer process. Among the M-NDs/Zr-MOF catalysts, Pd-NDs/Zr-MOF exhibits the highest electrocatalytic activity, delivering a NH3 yield of 287.31 mmol·h-1·g-1cat. and a Faradaic efficiency of 58.1%. The proposed interfacial reduction nucleation strategy for anchoring M NDs on Zr-MOFs can be applied to other challenging energy conversion reactions.

An aniline vapor sensor with efficient aniline/BTEX selectivity based on hydroxyl functionalized zirconium metal-organic framework

Adsorptive detection of aniline vapor is desired for its potential energy-efficient on replacing current methods. Realizing efficient selective aniline/BTEX adsorptive detection in the porous materials is challenging because of the lack of functional sites. By virtue of functionalization, we herein report a hydroxyl functionalized zirconium metal-organic framework (UIO-66(OH)2) for the efficient selective aniline/BTEX detection. UIO-66-(OH) 2 shows a significant aniline/BTEX response difference and selectivity under ambient conditions. Simulative calculation indicates that the hydrogen bond interaction between –OH and the –NH2 group of aniline enhances their selective adsorption.

Zirconium metal organic framework based opto-electrochemical sensor for nitrofurazone detection

The manuscript presents a zirconium metal–organic framework (Zr-MOF or UiO-66-NH2) based efficient sensing system to detect nitrofurazone (NFZ) antibiotic, by employing electrochemical-optical dual detection technique. The Zr-MOF was synthesized by solvothermal method and the success of synthesis was confirmed by using analytical techniques of characterization. For electrochemical determination of NFZ, electrodeposited gold nanoparticles supported zirconium metal–organic framework modified screen-printed electrode (AuNPs/UiO-66-NH2/SPCE) was used. As prepared electrochemical sensing platform showed a wide linear concentration range of 1x10−8 to 5x10−5 mol/L for NFZ. For fluorometric measurements, synthesized UiO-66-NH2 was employed under optimized conditions, and a turn-off behavior of NFZ towards UiO-66-NH2 was observed from a range of concentration 1x10−8 to 4.5x10−5 mol/L of NFZ. The proposed opto-electrochemical sensor attained low detection limit in nM range, showed selective behavior in presence of other antibiotics, and gave a reproducible signal with the RSD value less than 2.5% (n = 5). The prepared sensor was tested to detect NFZ in lake water samples and the results indicated good percentage recovery in the range 97.70–98.40 and 93.30–97.84%, for electrochemical and optical methods, respectively.

Effective adsorption of doxorubicin hydrochloride on zirconium metal-organic framework: Equilibrium, kinetic and thermodynamic studies

Zirconium metal organic framework (Zr-MOF) has been synthesized by hydrothermal method and various spectroscopic methods were used to characterize the samples. The adsorption of doxorubicin (DOX) onto Zr-MOF was studied. The effects of starting DOX concentration, contact time, solution pH, and temperature in an aqueous system in a batch mode were examined. Scanning electron microscopy (SEM) was used to determine surface properties of Zr-MOF. Nitrogen adsorption/desorption tests at 77 K revealed the surface area and pore volume of Zr-MOF to be 1498 m2/g and 0.957 cm3/g, respectively. The adsorption efficiency of Zr-MOF for DOX was at pH 6 than in alkaline solution, according to the results of the experiments. To characterize the equilibrium isotherms and estimate the isotherm values, the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption systems were used. The activation energy of adsorption was also determined to be 13.27 kJ/mol, showing that the adsorption mechanism involves chemisorption. The kinetic data were described using the pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich model. The pseudo-second-order kinetic data fit the dynamic data nicely. Isotherms include things like ΔGo, ΔHo and ΔSo The adsorption mechanism was computed and determined to be a spontaneous and endothermic reaction. The docking active place interactions were assessed to see if DOX might bind to the lung cancer 5C5S and liver cancer-2LEO receptor.

Polyoxometalate-Based Metal-Organic Frameworks as the Solid Support to Immobilize MP-11 Enzyme for Enhancing Thermal and Recyclable Stability.

The immobilization of enzymes has received much attention. Metal-organic framework (MOF) as the adsorbent for enzyme encapsulation provides an effective strategy. However, the encapsulation efficacy is not dependent solely on the specific surface area. Though leading into appropriate substrate with negative charge would enhance the encapsulation efficacy. Polyoxometalates (POMs) as the electron sponge would donate electrons without any structural change. In this study, Keggin-type phosphotungstic acid (PW12) was encapsulated in Zirconium metal-organic framework (PW12@UiO-67) as a heterogeneous adsorbent for the encapsulation of enzyme. Our following data proved that this composite cluster could enhance the adsorption of enzyme and the stability of MP-11 was then significantly improved after immobilization.

Effective Degradation of Novichok Nerve Agents by the Zirconium Metal-Organic Framework MOF-808.

Novichoks are a novel class of nerve agents (also referred to as the A-series) that were employed in several poisonings over the last few years. This calls for the development of novel countermeasures that can be applied in protective concepts (e.g., protective clothing) or in decontamination methods. The Zr metal-organic framework MOF-808 has recently emerged as a promising catalyst in the hydrolysis of the V- and G-series of nerve agents as well as their simulants. In this paper, we report a detailed study of the degradation of three Novichok agents by MOF-808 in buffers with varying pH. MOF-808 is revealed to be a highly efficient and regenerable catalyst for Novichok agent hydrolysis under basic conditions. In contrast to the V- and G-series of agents, degradation of Novichoks is demonstrated to proceed in two consecutive hydrolysis steps. Initial extremely rapid P-F bond breaking is followed by MOF-catalyzed removal of the amidine group from the intermediate product. The intermediate thus acted as a competitive substrate that was rate-determining for the whole two-step degradation route. Under acidic conditions, the amidine group in Novichok A-230 is more rapidly hydrolyzed than the P-F bond, giving rise to another moderately toxic intermediate. This intermediate could in turn be efficiently hydrolyzed by MOF-808 under basic conditions. These experimental observations were corroborated by density functional theory calculations to shed light on molecular mechanisms.

Constructing fluorine-doped Zr-MOF films on titanium for antibacteria, anti-inflammation, and osteogenesis

Implant infection, undesirable inflammation, and poor osseointegration are the primary reasons for implant failure, so it is pivotal to endow bone implants with antibacterial, anti-inflammatory, and osteogenic properties. Here, a multifunctional fluorine-doped zirconium-metal organic framework (Zr-MOF) film was constructed on the titanium to modify its biological performances. The fumaric acid, a common antioxidant, was selected as the ligand of Zr-MOF, and the hydrofluoric acid was used as the modulator to control the growth of Zr-MOF film. The obtained fluorine-doped Zr-MOF film possessed good biocompatibility and osteogenic ability, and it showed good antibacterial effects against both gram-positive S. aureus and gram-negative E. coli due to the release of fluoride ions. In addition, the doping of fluorine could reduce the stability of Zr-MOF by substituting fumaric acid, and stimulating the releases of fumaric acid. Furthermore, the fumaric acid released from Zr-MOF could down-regulate the expression of pro-inflammatory genes (NF-κB and IL-6), but up-regulate the expression of anti-inflammatory gene of IL-4 of macrophage, showing good anti-inflammatory ability. This study provided a reference for the modulation synthesis of MOF film, and proposed a promising strategy of designing Zr-MOF film to endow bone implants with antibacterial, anti-inflammatory, and osteogenic abilities.

Scalable robust nano-porous Zr-based MOF adsorbent with high-capacity for sustainable water purification

To find sustainable water solutions, the development of high capacity, scalable robust adsorbents and mechanistic insight about their performance offers the potential to effectively address the global challenges of water scarcity and water contamination. We herein rationally design Zr-cluster defective MOF-808 (MOF-808def) with exposed carboxyl groups, a robust zirconium metal–organic framework (Zr-MOF), exhibiting high adsorption capacity (qmax ∼ 296 mg·g−1) coupled with high selectivitity for tetracycline (TC) antibiotics, outperforming other water-stable MOFs, commercial and inorganic nano-adsorbents. MOF-808def functions well across a wide range of contaminant concentrations (from trace to high-concentration) and even in harsh conditions (e.g., high acidity and salinity). Both experimental and simulation results indicate that the mechanism of adsorption involves both physisorption and chemisorption via hydrogen bonding, electrostatic interactions (EIs) and C-O-C covalent bonding via esterification. Computational studies confirm that hydrogen bonding plays a key role in strong guest–host interactions between TCs and MOF-808def. Further, defects resulting from missing-Zr-clusters in MOF-808def are confirmed to enhance adsorption performance. Specifically, the defect sites present exposed carboxyl groups from MOF-808def linker ligands that selectively react with –OH groups (phenol and tertiary alcohol moieties) in TC via esterification. These defects drive highly selective adsorption even at low concentrations of TCs (e.g., 500 ppb). Aiming for more than enhanced performance, economic estimation and scalable engineered reactor tests revealed that MOF-808def and its nano-composites are free of environmental risks and offer promise for sustainable water treatment at pilot scale. The use of defect-engineering rationales is a molecule-level design concept that could be generally useful for the development of the next generation of MOF-based nano-adsorbents for sustainable water treatment applications.

Water Sorption Evolution Enabled by Reticular Construction of Zirconium Metal-Organic Frameworks Based on a Unique [2.2]Paracyclophane Scaffold.

Water vapor sorption by metal-organic frameworks (MOFs) has gathered significant interest because of its prominent potential in many applications such as moisture harvesting, dehumidification, heat pump regulation, and hydrolysis catalysis. However, the reticular design and exploration of robust and high-performing Zr-MOFs for such purposes remains a sought-after endeavor. In this work, we present the deployment of reticular chemistry to target a series of robust Zr-MOFs based on a unique [2.2]paracyclophane (PCP) scaffold. The ease of functionalization of PCP enables the desired synthesis of three carboxylate linkers, one ditopic and two tetratopic, which further assemble into a total of five Zr-MOFs with distinct topological structures, i.e., a new 2D net (NU-700), fcu (NU-405), flu (NU-1800), she (NU-602), scu (NU-913). Notably, the water vapor sorption performances of all the Zr-MOFs are highly dependent on their framework topology and pore metric, in which NU-602 and NU-913 with uniform 1D channels exhibit S-shaped water sorption isotherms with a steep pore-filling step and high uptake capacities of 0.72 g g-1 at 70% relative humidity (RH) and 0.88 g g-1 at 60% RH, respectively. Moreover, NU-913 displays exceptionally high working capacity of 0.72 g g-1 in the range of 40-60% RH. Additionally, we demonstrate that the hydrolytic stability and water adsorption-desorption recyclability of NU-913 can be remarkably improved by capping the Zr6 nodes with the more hydrophobic agent, trifluoroacetic acid, making it a potential candidate for water sorption-based applications.

Superradiance and Directional Exciton Migration in Metal-Organic Frameworks.

Crystalline metal-organic frameworks (MOFs) are promising synthetic analogues of photosynthetic light-harvesting complexes (LHCs). The precise assembly of linkers (organic chromophores) around the topology-defined pores offers the evolution of unique photophysical behaviors that are reminiscence of LHCs. These include MOF excited states with photoabsorbed energy that is spatially dispersed over multiple linkers defining the molecular excitons. The multilinker molecular excitons display superradiance─a hallmark of coupled oscillators seen in LHCs─with radiative rate constant (krad) exceeding that of a single linker. Our theoretical model and experimental results on three zirconium MOFs, namely, PCN-222(Zn), NU-1000, and SIU-100, with similar topology but varying linkers suggest that the size of such molecular excitons depends on the electronic symmetry of the linker. This multilinker exciton model effectively predicts the energy transfer rate constant; corresponding single-step exciton hopping time, ranging from a few picoseconds in SIU-100 and NU-1000 to a few hundreds of picoseconds in PCN-222(Zn), matches well with the experimental data. The model also predicts the anisotropy of exciton displacement with preferential migration along the crystallographic c-axis. Overall, these findings establish various missing links defining the exciton size and dynamics in MOF-assembled linkers. The understandings will provide design principles, especially, positioning the catalysts or electrode relative to the linker orientation for low-density solar energy conversion systems.

Insights into dual-functional modification for water stability enhancement of mesoporous zirconium metal–organic frameworks

This study revealed dual functions of the installed Facac ligands: enhancement of framework mechanical stability due to electrostatic interactions; and weaker capillary forces evaluated from free energies of dehydration during water evacuation.