Metal Organic Framework UiO-66 Research Articles

UiO-67 metal-organic frameworks with dual amino/iodo functionalization, and mixed Zr/Ce clusters: Highly selective and efficient photocatalyst for CO2 transformation to methanol

Metal-organic frameworks (MOFs) are promising tools for photocatalytic CO2 reduction (PCR) to produce valuable added-value products. However, existing MOFs demonstrate significantly weaker potential for PCR to MeOH compared to fuels like CO, CHOOH, and CH4. This study address this challenge by exploring a series of bifunctional UiO-67 MOFs containing NH2 and I groups with varying Ce to Zr metal node ratios (0, 10, 20, 29, and 40 % Ce). These MOFs, denoted as Zr/CeX%-UiO-67(NH2, I), were probed for their ability to convert CO2 to MeOH under solar irradiation without the need for a photosensitizer. The results demonstrate a remarkable increase in both selectivity and efficiency for MeOH production with increasing Ce content. Notably, Zr/Ce29%-UiO-67(NH2, I) achieves 100 % selectivity for MeOH production, along with MeOH productivity of 44.7 µmolh−1g−1, significantly surpassing previously reported UiO-based MOFs for PCR-to-MeOH conversion. Furthermore, this MOF exhibits exceptional CO2 uptake capacity compared to pristine UiO-67 and many established MOFs, further highlighting its catalytic efficacy. The outstanding photocatalytic performance of Zr/Ce40%-UiO-67(NH2, I) can be attributed to a synergistic combination factors: (i) the optimal incorporation of redox-active Ce metal sites, (ii) enhanced CO2 capture facilitated by the cooperative interaction of NH2 and I groups, and (iii) the introduction of amino functions that broaden the light absorption range of the MOF. This work demonstrates a successful strategy for incorporating various functionalities into MOFs, paving the way for the design of highly selective and efficient PCR catalysts for MeOH production.

A Bioinspired Copper-Pair Catalyst in Metal-Organic Frameworks for Molecular Dioxygen Activation and Aerobic Oxidative C-N Coupling.

Open Cu sites were loaded to the UiO-67 metal-organic framework (MOF) skeleton by introduction of flexible Cu-binding pyridylmethylamine (pyma) side chains to the biphenyldicarboxylate linkers. Distance between Cu centers in the MOF pores was tuned by controlling the density of metal-binding side chains. "Interacted" Cu-pair or "isolated" monomeric Cu sites were achieved with high and low (pyma)Cu side chain loading, respectively. Spectroscopic and theoretical studies indicate that "interacted" Cu pairs can effectively bind and activate molecular dioxygen to form Cu2O2 clusters, which showed high catalytic activity for aerobic oxidative C-N coupling. On the contrary, MOF catalyst bearing isolated monomeric Cu sites only showed modest catalytic activity. Enhancement in catalytic performance for the Cu-pair catalyst is attributed to the remote synergistic effect of the paired Cu site, which binds molecular dioxygen and cleaves the O═O bond in a collaborative manner. This work demonstrates that noncovalently interacted metal-pair sites can effectively activate inert small molecules and promote heterogeneous catalytic processes.

Acetone Gas Sensing with Quartz Crystal Microbalance and Adsorption Characteristics for UiO-66 Metal–Organic Frameworks

Acetone Gas Sensing with Quartz Crystal Microbalance and Adsorption Characteristics for UiO-66 Metal–Organic Frameworks

Enhancing antimicrobial efficacy: 8-Hydroxyquinoline incorporation into metal-organic frameworks with iron ion coupling

The antimicrobial properties of 8-Hydroxyquinoline (8-Hq), a small organic compound known for its metal-chelating capabilities, hold significant promise. However, its limited solubility in water poses a challenge for practical applications. In this study, we address this limitation by augmenting the antimicrobial efficacy of 8-Hq through its integration into the metal-organic framework UiO-66 (named 8-Hq@UiO-66) and coupling it with iron ions (designated as Fe/8-Hq@UiO-66) via an adsorption process. The sorption isotherm and adsorption kinetics were meticulously examined using Langmuir's adsorption model and the pseudo-second-order kinetic model. Material characterization techniques including powder X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption isotherms, ultraviolet–visible spectroscopy, and photoluminescence spectroscopy revealed the coordination of zirconium clusters and iron with the nitrogen and hydroxyl groups of 8-Hq, respectively. Furthermore, our investigation into metal ion adsorption demonstrated that the 8-Hq@UiO-66 composite displayed a notable selectivity for iron ions over other metal ions in aqueous media. Under optimized conditions, the adsorption capacity for iron ions ranged from approximately 34–46 mg g−1. Importantly, the Fe/8-Hq@UiO-66 composite exhibited potent antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. These findings underscore the potential of incorporating 8-Hq into porous metal-organic frameworks and coupling it with iron ions to enhance its antimicrobial efficacy.

Synthesis of Cr(OH)3/ZrO2@Co-based metal-organic framework from waste poly(ethylene terephthalate) for hydrogen production via formic acid dehydrogenation at low temperature

Recycling waste polyethylene terephthalate (PET) bottles into value-added ligand materials for synthesizing metal-organic frameworks (MOFs) derived catalysts is an eco-friendly and economically viable process. The waste PET bottles were readily broken down into 1,4-benzenedicarboxylic acid (BDC) ligands in a highly alkaline environment. Herein, we fabricated a Co@Cr(OH)3/ZrO2 catalyst via the carbonization of PET-derived UiO-66 metal-organic frameworks for the catalytic dehydrogenation of formic acid at low temperatures. The as-prepared Co@Cr(OH)3/ZrO2 catalyst provides a turnover frequency of 7685 h−1 for hydrogen generation (120 mL in 1.5 min) at ambient temperature. This is due to the uniform dispersion of the fine metal nanoparticle (NPs) (Co NPs, ∼3.75 nm) and the synergistic effect of the Co NPs and Cr(OH)3/ZrO2 supports. In addition, the characterization results indicate that porous Zr-MOFs may effectively enclose tiny particles, which is favorable for enhanced dehydrogenation performance. In addition, the Co@Cr(OH)3/ZrO2 catalysts demonstrated excellent stability against aggregation and were recyclable over seven cycles without any significant catalytic loss. Thus, this study provides a sustainable methodology for the development of MOF-derived, effective, and stable catalysts for formic acid dehydrogenation towards hydrogen production.

Fabrication of phosphorylated UiO-66 for efficient selective removal of Pb2+ from acidic wastewater

Metal-organic framework (MOF) materials have emerged as promising candidates for treating heavy metal wastewater because of their controllable pore size, high specific surface area, and abundant active sites. Nevertheless, the currently reported MOFs usually require near-neutral environments (pH = 5–6) to achieve efficient removal of Pb2+ and cannot be applied to acidic environments (pH = 2–3). In this work, the structurally stabilized zirconium-based MOF UiO-66 was chosen as the object of study. Three phosphate ester-based MOFs (UiO-66-(OPO3)X) containing different amounts and spatial positions were designed and prepared by simple chemical modification and used to remove Pb2+. Adsorption experiments showed that they could reach adsorption equilibrium in 30 min with excellent adsorption rate. Owing to the unique ionization ability of the phosphate ester group, UiO-66-(OPO3)X maintains a high removal efficiency of Pb2+ even at pH = 2 and pH = 3. In addition, selectivity and competition experiments demonstrated that UiO-66-(OPO3)X possessed excellent selectivity and anticompetitive ability towards Pb2+.The excellent regeneration performance demonstrates their value for practical application. Moreover, the adsorption mechanism was investigated in detail by experiment combined with density functional theory (DFT).

Phosphine-incorporated Metal-Organic Framework for Palladium Catalyzed Heck Coupling Reaction.

As an emerging material with the potential to combine the high efficiency of homogeneous catalysts and high stability and recyclability of heterogeneous catalysts, metal-organic frameworks (MOFs) have been viewed as one of the candidates to produce catalysts of the next generation. Herein, we heterogenized the highly active mono(phosphine)-Pd complex on surface of UiO-66 MOF, as a catalyst for Suzuki and Heck cross coupling reactions. The successful immobilization of these Pd-monophosphine complexes on MOF surface to form UiO-66-PPh2-Pd was characterized and confirmed via comprehensive set of analytical methods. UiO-66-PPh2-Pd showed high activity and selectivity for both Suzuki and Heck Cross Coupling Reactions. This strategy enabled facile access to mono(phosphine) complexes which are challenging to design and require multistep synthesis in homogeneous systems, paving the way for future MOF catalysts applications by similar systems.

Anionic oxyl radical formed on CrVI-oxo anchored on the defect site of the UiO-66 node facilitates methane to methanol conversion.

The direct conversion of methane to methanol has attracted increasing interest due to abundant and low-cost natural gas resources. Herein, by anchoring Cr-oxo/-oxyhydroxides on UiO-66 metal-organic frameworks, we demonstrate that reactive anionic oxyl radicals can be formed by controlling the coordination environment based on the results of density functional theory calculations. The anionic oxyl radicals produced at the completely oxidized CrVI site acted as the active species for facile methane activation. The thermodynamically stable CrVI-oxo/-oxyhydroxides with the anionic oxyl radicals catalyze the activation of the methane C-H bond through a homolytic mechanism. An analysis of the results showed that the catalytic performance of the active oxyl species correlates with the reaction energy of methane activation and H adsorption energies. Following methanol formation, N2O can regenerate the active sites on the most stable CrVI oxyhydroxides, i.e., the Cr(O)4Hf species. The present study demonstrated that the anionic oxyl radicals formed on the anchored CrVI oxyhydroxides by tuning the coordination environment enabled facile methane activation and facilitated methanol production.

UiO-66 metal-organic frameworks as aldol condensation catalyst: Impact of defects, solvent, functionality on the catalytic activity and selectivity

Defected and amine-loaded zirconium-based metal–organic frameworks (MOF) UiO-66(Zr) have been characterized and chemically assessed in a condensation reaction of acetone and 4-nitrobenzaldehyde. The present work focuses primarily on the production of the aldol adduct as the main product while minimizing the formation of the enone adduct as a side product. Four analogues with varying numbers of missing linkers in the hexanuclear secondary building units, from one to four out of a total of 12, were synthesized. Thorough characterization showed that an increased number of defects results in an enhanced acidity, a higher internal surface area, and an increased accessibility of coordinatively unsaturated Zr-sites. The catalytic performance assessment revealed that defects, to a certain extent, positively affect the selectivity towards the aldol adduct, i,e. the catalyst, which is missing 3 of the 12 linkers, exhibits the highest activity in a solvent-free environment with a turnover frequency (TOF) amounting to 8.03 10-3 s−1. This TOF value is approximately double of the catalyst with 1.4 defects, which exhibited a TOF of only 4.41 10-3 s−1. Excluding more than three linkers more likely leads to 'missing cluster defects' and causes a decrease in the reaction rate towards the aldol adduct. A reduction in overall catalytic activity was observed upon functionalization with amine groups (UiO-66-NH2). Functionalization with L-proline (UiO-66Lpr) resulted in a shift from an acid to a basic reaction mechanism which was reflected by an improved selectivity towards the aldol adduct while maintaining a reasonable overall activity level. The best performances were obtained working solvent-free or with hexane as a solvent, while polar/semi-polar solvents hindered the catalyst performance. An 18-hour stability test demonstrated the robustness of defected and functionalized UiO-66.

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.

Phosphomolybdic acid regulated the defective metal-organic framework UiO-66 for electrochemical nitrogen reduction reaction

In recent years, electrochemical ammonia synthesis has been considered a green process with excellent application prospects. The nitrogen reduction process (NRR) needs more activation energy when NN bonds are broken, which decreases the ammonia yield rate and Faraday efficiency (FE) for ammonia synthesis. Herein, UiO-66-xHPMo electrocatalysts are effectively synthesized by regulating the defects of the metal-organic framework (UiO-66) using phosphomolybdic acid (HPMo) as a defect regulator. XRD, FT-IR, TEM, XPS, TPD, etc., characterized the catalysts. As a result, the reasons for the increase in NH3 yield rate (RNH3) are catalysts losing the ligand of terephthalic acid, exposing more Zr6 nodes as active sites, and providing numerous active sites for NN cleavage. However, introducing HPMo makes catalysts more alkaline and have lower charge transfer resistance, which are more inclined to adsorb H+ and enhance hydrogen evolution reaction (HER), reducing FEs. Thus, with a voltage of −0.3 V (vs. RHE) and a neutral electrolyte (0.1 mol L−1 Na2SO4), UiO-66–2HPMo has excellent NRR performance (RNH3: 36.61 μg h−1 mg−1, FE: 31.09%).

Locally controlled MOF growth on functionalized carbon nanotubes

Metal-organic frameworks (MOFs) are highly versatile materials because of their tunable properties. However, the typically poor electrical conductivity of MOFs presents challenges for their integration into electrical devices. By adding carbon nanotubes to MOF synthesis, a highly intergrown material with increased conductivity and chemiresistive sensing properties can be obtained. Here, we present a patterning technique to control MOF growth on predefined areas of one particular carbon nanotube. We found that electron beam pretreatment of -COOH functionalized multi-walled carbon nanotubes inhibits the growth of UiO-66 MOF on these multi-walled carbon nanotubes. By irradiating individual multi-walled carbon nanotubes, we show that MOF growth can be inhibited in predefined tube areas, creating MOF-free spaces on the nanotube. In this way, our method shows a possibility to pattern MOF growth on individual nanotubes.

UiO-66 metal–organic framework nanoparticles as electrocatalysis for direct sodium borohydride fuel cells

UiO-66 metal–organic framework nanoparticles as electrocatalysis for direct sodium borohydride fuel cells

Nitrogen oxide remediation through metal–organic frameworks with bi-functional absorption and photocatalytic characteristics

In the population increase and growing industrialization framework, NOx (NO and NO2) arises among the most important air pollutants responsible for various health and environmental conditions. Metal-organic frameworks, MOFs, are promising materials for NOx remediation.This study investigates the removal of nitrogen oxides (NOx) using metal–organic frameworks (MOFs). MOFs UiO-66, UiO-66-NH2, MIL-125, and MIL-125-NH2 were synthesized and characterized. The surface area of the MOFs was quantified, showing values like 1118 m2/g for UiO-66-NH2 and 1424 m2/g for MIL-125-NH2. The NOx removal efficiency using the NH2 functionalized MOFs reached 100 % efficiency under UV light. Moreover, the immobilization of MIL-125-NH2 in carrageenan/alginate matrices was investigated, maintaining significant NOx reduction capabilities ∼ 80 %. This work also emphasizes the potential of MOFs by combining adsorptive and photocatalytic properties, providing insights into NOx capture and transformation mechanisms, and proposing a viable approach for sustainable air remediation technologies. This work paves the way for the successful applications of MOFs and MOF-modified membranes for air pollution mitigation.

Determining Surface Areas and Pore Volumes of Metal-Organic Frameworks.

The surface area and pore volume of a metal-organic framework (MOF) can provide insight into its structure and potential applications. Both parameters are commonly determined using the data from nitrogen sorption experiments; commercial instruments to perform these measurements are also widely available. These instruments will calculate structural parameters, but it is essential to understand how to select input data and when calculation methods apply to the sample MOF. This article outlines the use of the Brunauer-Emmett-Teller (BET) method and Barrett-Joyner-Halenda (BJH) method for the calculation of surface area and pore volume, respectively. Example calculations are performed on the representative MOF UiO-66. Although widely applicable to MOFs, sample materials and adsorption data must meet certain criteria for the calculated results to be considered accurate, in addition to proper sample preparation. The assumptions and limitations of these methods are also discussed, along with alternative and complementary techniques for the MOF pore space characterization.

Carbon (IV) oxide adsorption efficiency of functionalized HKUST-1, IRMF-1, and UiO-66 metal organic frameworks

The ever-increasing consumption of fossil fuels to meet up with the global economic and industrial energy needs has led to climatic change due to uncontrollable emission of a major greenhouse gas (CO2). As a way of mitigating the amount of CO2 in the atmosphere, search for effective and efficient solid adsorbent has been at the front burner of current scientific research. A class of solid adsorbent known as metal organic frameworks (MOFs) have demonstrated immense potentials for CO2 adsorption due to its porous, high thermal and chemical stability, high versatility and ease of production. Upon functionalization, the adsorption efficiency of this class of materials was found to improve tremendously. In this review, the CO2 capture and sequestration potentials of three MOFs (UiO-66, HKUST-1, and MOF-5) and their composites were investigated in the search for economical, stable, and highly selective novel adsorbents for CO2 adsorption.

The cooperative performance of iodo and copper in a Zr-based UiO-67 metal-organic framework for highly selective photocatalytic CO2 reduction to methanol

Photocatalytic CO2 reduction (PCR) to fuels using metal-organic frameworks (MOFs) offers promising solutions for both enhancing energy supply and mitigating global warming. However, research addressing the selectivity towards MeOH production, the role of CO2 uptake in productivity, and the identification of intermediates remains limited. Herein, we present an iodo/copper functionalization strategy for the Zr-based UiO-67 MOF. The resulting bifunctional Cu/I2-Zr-BPDC/BPyDC exhibited remarkable selectivity in light-driven CO2 reduction to MeOH, revealing the first investigation of halogen bonding's effect on PCR. Crucially, Cu/I2-Zr-BPDC/BPyDC surpassed not only pristine Zr-BPyDC, I2-Zr-BPDC, and Cu-Zr-BPyDC, but also boasted the best catalytic performance among reported MOFs. Furthermore, Cu/I2-Zr-BPDC/BPyDC demonstrated a CO2 uptake capacity of 48.6 mg g−1, 1.7 times greater than non-modified Zr-BPyDC, suggesting a direct correlation between CO2 adsorption efficiency and CO2 conversion. In addition to assigning CuII ↔ CuI catalytic cycle, collaborative performance of I and Cu functions in CO2 activation was traced by infrared spectra that elucidate the CI…OCO interaction and Cu…CO2/CuCO2H complex formation. This work provides valuable insights for engineering selective and high-performance PCR catalyst through the rational incorporation of functionalities within MOFs.

Efferocytosis-Inspired Biomimetic Nanoplatform for Targeted Acute Lung Injury Therapy.

Acute lung injury (ALI) is a serious inflammatory disease that causes impairment of pulmonary function. Phenotypic modulation of macrophage in the lung using fibroblast growth factor 21 (FGF21) may be a potential strategy to alleviate lung inflammation. Consequently, achieving specific delivery of FGF21 to the inflamed lung and subsequent efficient FGF21 internalization by macrophages within the lung becomes critical for effective ALI treatment. Here, an apoptotic cell membrane-coated zirconium-based metal-organic framework UiO-66 is reported for precise pulmonary delivery of FGF21 (ACM@U-FGF21) whose design is inspired by the process of efferocytosis. ACM@U-FGF21 with apoptotic signals is recognized and internalized by phagocytes in the blood and macrophages in the lung, and then the intracellular ACM@U-FGF21 can inhibit the excessive secretion of pro-inflammatory cytokines by these cells to relieve the inflammation. Utilizing the homologous targeting properties inherited from the source cells and the spontaneous recruitment of immune cells to inflammatory sites, ACM@U-FGF21 can accumulate preferentially in the lung after injection. The results prove that ACM@U-FGF21 effectively reduces inflammatory damage to the lung by modulating lung macrophage polarization and suppressing the excessive secretion of pro-inflammatory cytokines by activated immune cells. This study demonstrates the usefulness of efferocytosis-inspired ACM@U-FGF21 in the treatment of ALI.

Chlorine retention in drinking water with UiO66 metal–organic framework

Chlorine retention in drinking water with UiO66 metal–organic framework

Reversible solvent interactions with UiO-67 metal-organic frameworks.

The utility of UiO-67 Metal-Organic Frameworks (MOFs) for practical applications requires a comprehensive understanding of intermolecular host-guest MOF-analyte interactions. To investigate intermolecular interactions between UiO-67 MOFs and complex molecules, it is useful to evaluate the interactions with simple polar and non-polar analytes. This problem is approached by investigating the interactions of polar (acetone and isopropanol) and non-polar (n-heptane) molecules with functionalized UiO-67 MOFs via temperature programmed desorption mass spectrometry and temperature programmed Fourier transform infrared spectroscopy. We find that isopropanol, acetone, and n-heptane bind reversibly and non-destructively to UiO-67 MOFs, where MOF and analyte functionality influence relative binding strengths (n-heptane ≈ isopropanol > acetone). During heating, all three analytes diffuse into the internal pore environment and directly interact with the μ3-OH groups located within the tetrahedral pores, evidenced by the IR response of ν(μ3-OH). We observe nonlinear changes in the infrared cross sections of the ν(CH) modes of acetone, isopropanol, and n-heptane following diffusion into UiO-67. Similarly, acetone's ν(C=O) infrared cross section increases dramatically when diffused into UiO-67. Ultimately, this in situ investigation provides insights into how individual molecular functional groups interact with UiO MOFs and enables a foundation where MOF interactions with complex molecular systems can be evaluated.