Synthesis Of UiO-66 Research Articles

Rational Synthesis of UiO-66 and its Application in the Hydrogenation Reaction of p-Chloronitrobenzene

Hydrogenation is a widely used reaction in the oil processing and industrial organic synthesis. UiO-66 is a prom-ising porous organic-inorganic material that can be used as a support for catalytically active particles. The key part in the application of highly porous UiO-66 is the search of a simple synthesis method that meets international environmental standards. In this study, a "rational" method for the synthesis of MOFs was used to produce UiO-66. The use of pre-synthesized multinuclear zirconia clusters facilitates the synthesis of the desired network to-pology, enabling the process to be conducted in an environmentally friendly aqueous solution. The effects of re-action temperature, linker volume concentration and solvent type on the specific surface area and thermal properties were also evaluated in this work. We studied the composition, structure and physicochemical properties of the obtained compounds by IR spectroscopy, TGA and XRD analysis. The proposed procedure has been shown to yield UiO-66 with high specific surface area (SBET = 885 m2/g) and to extend the thermal stability range up to 490 °C. The post-synthetic modification of the obtained UiO-66 with the introduction of catalytically active Pd (Pd/UiO-66) was carried out, and high selectivity (83,0 %) of the obtained Pd/UiO-66 exhibited high selectivity in the hydrogenation reaction of p-chloronitrobenzene into p-chloroaniline in comparison with the traditional Pd/Al2O3.

Continuous, solvent-free, and mechanochemical synthesis of UIO-66 (Mn) by gas-solid two-phase flow and mechanism research

In this work, we introduced a novel gas-solid two-phase flow technique (GSF) for the continuous mechanochemical synthesis of the classic MOFs structure UIO-66(Mn). The synthesized product was thoroughly examined using Fourier transform infrared spectroscopy, powder X-ray diffraction, single crystal X-ray diffraction, differential thermal analysis, thermogravimetric analysis, XPS Method, and transmission electron microscopy. The results indicated that the product, synthesized using this method, was analytically pure and achieved a high yield without any by-products. We also explored its preparation mechanism by introducing the classical model of solid-phase reaction. The green chemistry metrics of this approach suggest it was significantly more environmentally friendly. Moreover, this work demonstrateed that the method can replace traditional solvothermal methods, offering a novel approach for the mechanochemical synthesis of MOFs.

Catalytic transfer hydrogenation of α-angelica lactone over Nickel(II) modified UiO-66 metal organic framework under mild conditions

In the realm of biomass valorization, catalysts play a pivotal role, and UiO-66(Zr), a type of metal organic framework (MOF), emerges as a promising heterogeneous catalyst. This study focuses on incorporating Ni2+ into UiO-66(Zr) for application in catalytic transfer hydrogenation (CTH) of bio-derived α-angelica lactone (a-AL) to ɣ-valerolactone (GVL). The synthesis of UiO-66(Zr) occurs through a solvothermal process at 120 °C for 24 h. Ni(II) modification, achieved through wet impregnation with loadings of 2.5 and 5.0 wt%, results in no observable diffraction peaks associated with Ni particles in XRD analysis. FTIR analysis indicates significant shifts, suggesting deprotonation of the carboxylic moiety from the ligand and coordination with Zr4+ metal ion. Nitrogen sorption isotherms show a reduction in surface area and pore volume upon Ni(II) incorporation. FESEM analysis reveals particle agglomeration and increased size with Ni(II) introduction. EDX and HRTEM confirm the presence of 0.9 and 1.8 wt% Ni(II) on UiO-66(Zr). TG/DTA analysis affirms that Ni(II) does not affect the thermal stability of UiO-66(Zr). Ultimately, the introduction of Ni(II) enhances the catalytic performance of UiO-66(Zr), increasing the conversion and selectivity towards ɣ-valerolactone from 67 to 83.3 % and 71.6 % to 97.4 %, respectively, under mild reaction conditions.

Continuously Tunable MOFs Enable Precise Mass Transfer for High-Performance Isomer Separation.

Modulating mass transfer is crucial for optimizing the catalytic and separation performances of porous materials. Here, we systematically developed a series of continuously tunable MOFs (CTMOFs) that exhibit incessantly increased mass transfer. This was achieved through the strategic blending of ligands with different lengths and ratios in MOFs featuring the fcu topology. By employing a proportional mixture of two ligands in the synthesis of UiO-66, the micropores expanded, facilitating faster mass transfer. The mass transfer rate was evaluated by dye adsorption, dark-field microscopy, and gas chromatography (GC). The GC performance proved that both too-fast and too-slow mass transfer led to low separation performance. The optimized mass transfer in CTMOFs resulted in an exceptionally high separation resolution (5.96) in separating p-xylene and o-xylene. Moreover, this study represents the first successful use of MOFs for high-performance separation of propylene and propane by GC. This strategy provides new inspiration in regulating mass transfer in porous materials.

In-situ growth of metal-organic frameworks on cellulose nanofiber aerogels for rapid adsorption of heterocyclic aromatic amines

Heterocyclic aromatic amines (HAAs) are the main carcinogens produced during thermal processing of protein-rich foods. In this paper, a composite aerogel (TOCNFCa) with a stabilized dual-network structure was prepared via a template for the in-situ synthesis of UiO-66 on cellulose for the adsorption of HAAs in food. The dual-network structure of TOCNFCa provides the composite aerogel with excellent wet strength, maintaining excellent compressive properties. With the in-situ grown UiO-66 content up to 71.89 wt%, the hierarchical porosity endowed TOCNFCa@UiO-66 with the ability to rapidly adsorb HAAs molecules with high capacity (1.44–5.82 μmol/g). Based on excellent thermal stability, adsorption capacity and anti-interference, TOCNFCa@UiO-66 achieved satisfactory recoveries of HAAs in the boiled marinade, which is faster and more economical than the conventional SPE method. Moreover, TOCNFCa@UiO-66 could maintain 84.55 % of the initial adsorption capacity after 5 times of reuse.

Facile Recycling Strategy of Dyed Polyester Waste by Template-Based Synthesis of UiO-66 for Value-Added Transformation into Self-detoxifying Fabrics.

Polyethylene terephthalate (PET) accounts for a significant portion of textile waste, and recycling strategies for this material have attracted much attention. This study proposes a facile and innovative PET recycling method applicable to environmental remediation that involves the conversion of dyed PET fabric waste into a value-added fabric. Herein, a template-based synthesis approach capable of growing a UiO-66 metal-organic framework (MOF) directly on a dyed PET fabric is reported. The advantage of this process lies in its simplicity, where the partial hydrolysis of PET followed by a zirconium chloride treatment results in the successful growth of UiO-66 on a dyed PET fabric with the concurrent removal of the dye without additional steps. The catalytic performance of the UiO-66-grown fabric was evaluated through the degradation of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant. The fabric produced by the simple metal treatment (Zr@PEThyd) exhibited excellent DMNP degradation performance with t1/2 = 43.3 min and maintained functional stability after a harsh washing procedure, an outcome attributed to the surface-assisted UiO-66 growth that ensured good bonding stability. The developed process is innovative in that it uses dyed PET waste as a template for the direct growth of UiO-66, simplifying the process without compromising the catalytic functionality. This research provides an informative option for a sustainable textile recycling strategy by transforming dyed PET waste into an advanced self-detoxifying material.

Insights into the Spray Synthesis of UiO-66 and UiO-66-NH2 Metal–Organic Frameworks: Effect of Zirconium Precursors and Process Parameters

UiO-66, a zirconium-based metal–organic framework, was synthesized using a one-step spray synthesis method to investigate the effects of preheating the precursor solution and Zr sources on crystallinity. Using ZrCl4 with water as a modulator requires preheating at 80 °C for 120 min or 120 °C for 30 min for the spray synthesis of UiO-66 to form secondary building units (SBUs). By contrast, the use of Zr(OnPr)4 with acetic acid (AcOH) as a modulator allowed the spray synthesis of UiO-66 and UiO-66-NH2 without preheating because of the rapid formation of SBUs with AcOH. The spray-synthesized UiO-66 using Zr(OnPr)4 exhibited a BET surface area of 1258 m2/g and a CO2 adsorption capacity of 3.43 mmol/g at 273 K and 1 bar, while UiO-66-NH2 exhibited a BET surface area of 1263 m2/g and a CO2 adsorption capacity of 6.11 mmol/g under the same conditions.

Room-temperature synthesis of a Zr-UiO-66 metal-organic framework via mechanochemical pretreatment for the rapid removal of EDTA-chelated copper from water.

Treatment of heavy metal pollution in complexed states within water bodies presents significant challenges in the current water treatment field. Adsorption as a means for the removal of heavy metals is characterized by its simplicity of operation, stable effluent, and minimal equipment requirements. Metal-organic frameworks (MOFs) as adsorbents hold significant interest for applications in water treatment. In this study, we investigated a green synthesis approach for the ball-milling pretreated synthesis of UiO-66(Zr) at room temperature, abbreviated as UiO-66(Zr)-rm. Besides having the same thermal stability and crystal structure as the product from microwave-assisted synthesis (UiO-66(Zr)-mw), the resulting UiO-66(Zr)-rm features smaller particle size and superior mesoporous structure. The adsorption efficiency and mechanism for removing EDTA-chelated copper (EDTA-CuII), a complexed heavy metal in water, were extensively analyzed. UiO-66(Zr)-rm presented a maximum adsorption capacity over EDTA-CuII of 43 mg g-1 and a much higher adsorption rate (0.16 g (mg h)-1) than UiO-66(Zr)-mw (0.06 g (mg h)-1). Hierarchically mesostructured defects allow the sorbate to have more effective diffusion in a shorter time to achieve faster adsorption kinetics. Benefiting from the mild synthesis conditions and nontoxic solvents, UiO-66(Zr) has the potential to be produced at a scaled-up level, thereby exhibiting excellent adsorption performance for the removal of complexed heavy metals in the future.

Development of MOF-MXene composite for the removal of dyes and antibiotic

Metal-organic framework composites have gained great attention in the adsorptive remediation of environmental pollutants because of their unique features such as tunable pore size and modification of their framework. The main objective of this study was to fabricate UiO-66/MXene (Ti3AlC2) composite through solvothermal method and newly synthesized adsorbent was characterized by utilizing powder X-Ray diffraction analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Exceptional adsorption properties of UiO-66/MXene composite were verified by adsorption of two model dyes i.e., methylene blue (MB), rhodamine B (RhB), and antibiotic i.e., tetracycline (OTC). Adsorption process was studied by applying different optimization parameters such as pH, contact time, adsorbent dose, and initial concentration of MB, RhB, and OTC. Results showed that UiO-66/MXene composite have best adsorption performance with removal rate of 98 % for MB, 97 % for RhB, and 99 % for OTC. Four kinetic models e.g., pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich models were applied, and results showed that kinetic process was well described by pseudo-second-order kinetic model for dyes and antibiotic. Maximum adsorption capacity (qm) of UiO-66/MXene composite was achieved up to 312, 285, and 476 mg/g for MB, RhB, and OTC respectively. Four different isotherm models are used such as Langmuir, Freundlich, Dubinin–Kaganer–Radushkevich (DKR), and Temkin, the study shows that the Langmuir isotherm model describes well for the adsorption of MB, RhB, and OTC. Thermodynamic studies suggested that the process of adsorption was spontaneous and endothermic for dyes and antibiotic. The results recommend that the successful synthesis of UiO-66/MXene composite offers beneficial visions in the development of MOF composites as adsorbents for water refining.

A Simple Method for Teaching Bragg’s Law in an Undergraduate Teaching Laboratory with the Use of Metal–Organic Frameworks

Metal–organic frameworks (MOFs) are a class of porous materials that are often crystalline with high surface area and structural tunability. In this laboratory experiment designed for inorganic chemistry students at the undergraduate level, students complete a two-step experiment where they will first (i) synthesize two isostructural zirconium-based MOFs, UiO-66 and UiO-67, and then (ii) isolate and characterize the materials using powder X-ray diffraction (PXRD). A simple solvothermal procedure was developed for the synthesis of UiO-66 and UiO-67 using the air/moisture-stable zirconyl chloride octahydrate as a starting reagent. Depending on the equipment available, the MOFs can be further characterized by nitrogen adsorption analysis for surface area determination using Brunauer–Emmett–Teller (BET) theory, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermogravimetric analysis (TGA), 1H nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). Upon synthesizing the MOFs and collecting the characterization data, students analyze and describe their results by answering a series of questions included in the laboratory manual. This exercise will allow students to develop practical laboratory skills while expanding their knowledge on some fundamental concepts in inorganic chemistry, materials chemistry, MOFs, crystallography, and other characterization techniques as availability allows.

Understanding the Role of Synthetic Parameters in the Defect Engineering of UiO-66: A Review and Meta-analysis

UiO-66 is one of the most significant and highly studied metal–organic frameworks to date due to its exceptional thermal and chemical stability and its demonstrated potential in a myriad of applications, such as the purification of contaminated waters, gas storage, and catalysis. Defective UiO-66, where either organic linkers or whole inorganic clusters are missing from the pristine framework structure, is of key interest as the unsaturated Zr sites left by these missed connections lead to enhanced catalytic and adsorptive performance, among other benefits such as increased surface area. A solvothermal approach with the inclusion of modulators is typically employed to synthesize defective UiO-66, but a complete understanding of the links between synthetic parameters and structural outcomes has yet to be reached. This review aims to address this gap by providing a thorough overview of the current literature and a detailed discussion of key aspects of the synthesis of UiO-66 and its resulting defectivity; this literature review is supported by a meta-analysis of representative experimental papers. The focus of the meta-analysis is to draw, where possible, quantitative connections between important synthetic parameters (namely, temperature, time, modulator acidity, and reagent concentration) and the structural features reported in the literature for defective UiO-66 (namely, quantitative defectivity, defect types, surface area, particle size, and pore volume). Despite significant limitations of the meta-analysis data set, we are able to determine some statistically significant relationships between parameters and provide recommendations for essential future experimental work. The research questions not conclusively answered by the meta-analysis are addressed by a thorough examination of individual papers discussing the various influencing factors. From this, we provide recommendations to aid the judicious choice of reagents and other synthetic parameters. Overall, this detailed analysis and review compiles critical experimental findings, provides key insights into optimizing defect formation in UiO-66, and highlights important research gaps in the current literature.

Facile synthesis of UiO-66/PAN adsorptive membrane for effective arsenic removal

Decreasing arsenic to below the discharge standard from potable water and wastewater with less energy consumption is crucial in water purification. Herein, a series of high-throughput adsorptive membranes have been successfully fabricated by blending polyacrylonitrile (PAN) copolymer with UiO-66 based on a facile non-solvent-induced phase separation process. Notably, UiO-66 contents within the resultant UiO-66/PAN adsorptive membranes can be flexibly modulated on demand, leading to variations of the structural features associated with pure water permeability, pore size, and hydrophilicity along with mechanical flexibility. Representatively, a sheet of M − 50 with a UiO-66/PAN mass ratio of 50% can effectively reduce trace arsenate (100 ppb) to below the permitted level (10 ppb) at the flux up to 1.0 × 103 L m−2 h−1. Moreover, M − 50 shows negligible leakage of UiO-66 nanoparticles during rinsed with acidic and alkaline solutions for 24 h. Furthermore, the spent M − 50 can be readily regenerated and maintain high removal efficiencies after multiple adsorption–regeneration cycles, rendering them promising sustainable materials. Hence, the designed UiO-66/PAN adsorptive membranes hold significant prospects for in-depth purification of arsenic-contaminated water.

Synthesis of UiO-66 with addition of HKUST-1 for enhanced adsorption of RBBR dye

Toxic dye removal, one of the most serious and common industrial pollutants released into natural water, is a critical issue for modern civilization. In this study, a series of UiO-66 composites was synthesized with addition of HKUST-1 using solvothermal method, which was used to remove RBBR dye. The structure, morphology and surface area of the composites were studied by several analyses. HK(5)/UiO-66 possessed a specific surface area of 557.63 m2/g and showed an adsorption capacity of 400 mg/g, higher than that of UiO-66 (261.92 mg/g) with a contact time of 50 min. Several adsorption parameters that influenced RBBR removal efficiency were investigated, such as pH, initial dye concentrations, and temperature. All the composites followed pseudo-first order kinetics and Langmuir isotherm adsorption. Moreover, the adsorption process occurred exothermically and spontaneously, indicating that the adsorption process was advantageous in terms of energy. The possible adsorption mechanism and cost analysis of the adsorbent were also studied in detail.

Experimental study on adsorption removal of SO2 in flue gas by defective UiO-66

Metal-organic frameworks (MOFs) with a high specific surface area, an adjustable pore structure, and functionalized pore environment have a broad application prospect in gas adsorption and separation. In this work, a series of defective UiO-66 (UiO-66-monocarboxylic acid) samples were prepared by adding different monocarboxylic acids during the synthesis of UiO-66. UiO-66-monocarboxylic acid samples (UiO-66-formic acid, UiO-66-acetic acid, UiO-66-benzoic acid, UiO-66-acrylic acid, and UiO-66-cyanoacetic acid) had a high specific surface area (1200–1400 m2/g) and a good thermal stability (560 °C). In the desulfurization experiment of simulated flue gas (SO2/CO2/O2/N2, 0.3/10.0/5.5/84.2 vol%), the breakthrough time of UiO-66-cyanoacetic acid for SO2 was higher (194 min/g), and the selectivity of SO2/CO2 reached 33.8. Through optimizing the moles of cyanoacetic acid added, the breakthrough time of SO2 on 18-UiO-66-cyanoacetic acid increased to 251 min/g. At a pressure of 1.0 bar and a temperature of 298 K, the adsorption capacity of SO2 by 18-UiO-66-cyanoacetic acid reached 762.1 mg/g. In addition, the adsorption behavior of 18-UiO-66-cyanoacetic acid for SO2 was considered as a combination of chemical and physical adsorption, and fractional chemisorption sites was provided by cyanoacetic acid.

Negatively Charged MOF-Based Composite Anion Exchange Membrane with High Cation Selectivity and Permeability.

Every metal and metallurgical industry is associated with the generation of wastewater, influencing the living and non-living environment, which is alarming to environmentalists. The strict regulations about the dismissal of acid and metal into the environment and the increasing emphasis on the recycling/reuse of these effluents after proper remedy have focused the research community’s curiosity in developing distinctive approaches for the recovery of acid and metals from industrial wastewaters. This study reports the synthesis of UiO-66-(COOH)2 using dual ligand in water as a green solvent. Then, the prepared MOF nanoparticles were introduced into the DMAM quaternized QPPO matrix through a straightforward blending approach. Four defect-free UiO-66-(COOH)2/QPPO MMMs were prepared with four different MOF structures. The BET characterization of UiO-66-(COOH)2 nanoparticles with a highly crystalline structure and sub-nanometer pore size (~7 Å) was confirmed by XRD. Because of the introduction of MOF nanoparticles with an electrostatic interaction and pore size screening effect, a separation coefficient (SHCl/FeCl2) of 565 and UHCl of 0.0089 m·h−1 for U-C(60)/QPPO were perceived when the loading dosage of the MOF content was 10 wt%. The obtained results showed that the prepared defect-free MOF membrane has broad prospects in acid recovery applications.

Enhanced CO2 adsorption performance on amino-defective UiO-66 with 4-amino benzoic acid as the defective linker

UiO-66(Zr), one of the Zr-based metal–organic frameworks (MOFs), is a potential adsorbent for gas separation owing to its large surface area, easily tunable pore structure, and high chemical/thermal stability. Nevertheless, its CO2 adsorption amount is somewhat modest in comparison to that of various MOFs. In this study, 4-aminobenzoic acid (PABA) as amino-defective linker was mixed to terephthalic acid at various compositions in a one-step synthesis of UiO-66(Zr) framework. This new restructuring strategy produced defective UiO-66(Zr) with enhanced porosity owing to the missing-linker defects, simultaneously formed –NH2 groups in the framework, leading to the improvement of the CO2 capture capacity. At 298 K and 100 kPa, the defective UiO-66 modified with 10% PABA exhibited the highest CO2 uptake capacity of ~ 2.47 mmol g−1 and ideal adsorbed solution theory (IAST)-based CO2/N2 selectivity of ~ 46, which surpass many other CO2 benchmark adsorbents. This opens a new perspective for developing defective UiO-66(Zr) adsorbent contained amine functional groups, which can improve CO2 separation performance.

Study of UiO-66 and UiO-66 Modulated with Acetic Acid as the Adsorbent for Eriochrome Black T Dye

UiO-66, as one of the metal-organic framework (MOF) compounds, has been used to treat some anionic and cationic dye waste. In order to determine the adsorption selectivity decisively, the synthesis of UiO-66 and UiO-66 modulated with acetic acid had been carried out, along with their adsorption tests for Eriochrome Black T (EBT) dye solution. The synthesis was performed by utilizing a solvothermal method with the reaction mixtures of zirconium (IV) chloride (ZrCl4) and terephthalic acid (H2BDC) as a ligand heated at 120 oC for 24 hours. Both UiO-66 (without acetic acid) and acetic acid modulated UiO-66 were obtained as a white powder. Acetic acid as a modulator was added and being investigated for the adsorption capability compared to the normal UiO-66. This study showed that normal UiO-66 exhibited better adsorption than acetic acid modulated UiO-66 with a mmol ratio of acetic acid:ligand varied from 50:1, 100:1, and 150:1. Acetic acid modulated UiO-66 with a mmol ratio of 50 exhibited the best crystallinity as observed by using x-ray diffraction. It can be concluded that the adsorption of EBT using normal and acetic acid modulated UiO-66 obeyed the pseudo-second-order reaction rate law as well as the Langmuir adsorption isotherm pattern.

Accelerated and scalable synthesis of UiO-66(Zr) with the assistance of inorganic salts under solvent-free conditions

The synthesis of UIO-66 (Zr) and its functionalized materials can be accelerated and scalable under solvent-free condition with the assistance of inorganic salts.

Improved continuous synthesis of UiO-66 enabling outstanding production rates

Optimization of the continuous synthesis of UiO-66 and derivatives with extremely high space time yield using a tubular reactor.

Synthesis of UiO-66 in Supercritical CO2 and Its Application in Dye Adsorption

UiO-66 nanocrystals were synthesized by supercritical reaction crystallization with anhydrous zirconium chloride as the metal precursor, terephthalic acid as the ligand, and a small amount of N,N-d...