UiO-66 Type Research Articles

Lanthanide-Doped Nanoparticles Anchoring on Metal-Organic Frameworks with Thermally Enhanced Upconversion Luminescence for Sensitive Nanothermometers.

Nanothermometers can detect changes in the local temperature in living cells and in vivo, revealing fundamental biological properties. Despite the exploration of different temperature-responsive materials, the design and development of temperature-sensing probes with high brightness and high sensitivity remain a daunting challenge. Here, we employed the UiO-66 type metal-organic frameworks (MOFs) to anchor UNCPs on the surface of the MOFs for constructing MOF@UCNPs nanohybrids. The in situ composite method with MOFs leads to the coordination interaction between the ligands and the surface of UCNPs, enabling controlled composite formation between different MOFs and UCNPs. Remarkably, the surface interaction favors the anomalous thermo-enhanced luminescence, achieving a 35-fold enhancement of UiO-66@NaYF4:Yb/Tm at 413 K. Furthermore, these MOF@UCNPs nanohybrids with thermo-enhanced luminescence are developed as multifunctional biological probes for bioimaging and intracellular temperature sensing, demonstrating a high thermal sensitivity of 1.92% K-1 in the physiological temperature range. Based on these findings, temperature monitoring of the local position was successfully carried out by the designed MOF@UCNPs nanoprobes in vivo. These findings underscore the potential of MOF@UCNPs nanohybrids, opening up new avenues for the development of a multifunctional platform for biological analysis.

Instrument-free detection of natamycin in beer and wastewater based on Eu-MOF ratiometric fluorescence response

Excessive intake of natamycin (NAT) is harmful to human health, so it is of great significance and necessity to effectively detect the content of NAT in food. In this study, we synthesized a dual-emission fluorescence probe, Eu@UiO-66(OH)2/(COOH)2, which exhibited emission peaks at 439nm and 614nm. This probe was obtained through the europium post-modification of UiO-66 type metal-organic frameworks (Eu-MOFs), which consisted of two types of ligands, 2, 5-dihydroxyterephthalic acid and pyromellitic acid. As expected, this probe Eu@UiO-66(OH)2/(COOH)2 can specifically respond to NAT with distinguishable ratiometric fluorescence changed from purple-red to blue with low limit of detection (0.15μM, approximately 0.10mg/kg), wide linear range (0-100μM), fast response (less than 1min), good selectivity and interference resistance. Based on the ratiometric fluorescence responsiveness, Eu@UiO-66(OH)2/(COOH)2 had been successfully used for the quantitative detection of NAT in wastewater, beer, yoghurt, and juice, demonstrating good recovery through smartphone-based colorimetric analysis. Thus, this work provides a ratiometric fluorescent probe for rapid, instrument-free and on-site detection of NAT in real samples such as beverage and environmental water.

Incorporation of a carboxyl-functionalized imidazolium-based ionic liquid into a UiO-66 type MOF for chemical fixation of CO2 into carbonates

CO2 cycloaddition to epoxides using ionic MOFs.

Highly Stable Amide-Functionalized Zirconium-Organic Frameworks: Synthesis, Structure, and Methane Storage Capacity.

With the development of crystalline porous materials toward methane storage, the stability issue of metal-organic framework (MOF) materials has caused great concern despite high working capacity. Considering the high stability of zirconium-based MOFs and effective functions of amide groups toward gas adsorption, herein, a series of UiO-66 type of Zr-MOFs, namely, Zr-fcu-H/F/CH3/OH, were successfully designed and synthesized by virtue of amide-functionalized dicarboxylate ligands bearing distinct side groups (i.e., -H, -F, -CH3, and -OH) and ZrCl4 in the presence of trifluoroacetic acid as the modulator. Single-crystal X-ray diffraction and topology analyses reveal that these compounds are archetypal fcu MOFs encompassing octahedral and tetrahedral cages, respectively. The N2 sorption isotherms and acid-base stability tests demonstrate that the materials possess not only relatively high surface areas, pore volumes, and appropriate pore sizes but also great hydrolytic stabilities ranging pH = 3-11. Furthermore, the volumetric methane storage working capacities of Zr-fcu-H, Zr-fcu-F, Zr-fcu-CH3, and Zr-fcu-OH at 298/273 K and 80 bar are 187/217, 175/193, 167/187, and 154/171 cm3 (STP) cm-3, respectively, which indicate that the zirconium-based crystalline porous materials are capable of storing relatively high amounts of methane.

Performance of Zr-Based Metal-Organic Framework Materials as In Vitro Systems for the Oral Delivery of Captopril and Ibuprofen.

Zr-based metal-organic framework materials (Zr-MOFs) with increased specific surface area and pore volume were obtained using chemical (two materials, Zr-MOF1 and Zr-MOF3) and solvothermal (Zr-MOF2) synthesis methods and investigated via FT-IR spectroscopy, TGA, SANS, PXRD, and SEM methods. The difference between Zr-MOF1 and Zr-MOF3 lies in the addition of reactants during synthesis. Nitrogen porosimetry data indicated the presence of pores with average dimensions of ~4 nm; using SANS, the average size of the Zr-MOF nanocrystals was suggested to be approximately 30 nm. The patterns obtained through PXRD were characterized by similar features that point to well-crystallized phases specific for the UIO-66 type materials; SEM also revealed that the materials were composed of small and agglomerate crystals. Thermogravimetric analysis revealed that both materials had approximately two linker deficiencies per Zr6 formula unit. Captopril and ibuprofen loading and release experiments in different buffered solutions were performed using the obtained Zr-based metal-organic frameworks as drug carriers envisaged for controlled drug release. The carriers demonstrated enhanced drug-loading capacity and showed relatively good results in drug delivery. The cumulative percentage of drug release in phosphate-buffered solution at pH 7.4 was higher than that in buffered solution at pH 1.2. The release rate could be controlled by changing the pH of the releasing solution. Different captopril release behaviors were observed when the experiments were performed using a permeable dialysis membrane.

Terbium doping and energy level modification of zirconium organic frameworks as probes for the improved determination of histamine and visual inspection of food freshness

Food safety is a common concern among people, and the development of high-performance food freshness detection technology is crucial, but is still highly challenging. Fluorescent sensing based on metal organic frameworks is a promising technology to tackle this issue. In this work, three UiO-66 type Zirconium organic frameworks (ZrOFs) which are functionalized with varying numbers of hydroxyl groups to alter the energy levels, and partial replacement of Zirconium(IV) by Terbium(III) ions to introduce additional emitting centers, were explored as probes for the sensing of Histamine (His). With one hydroxyl group introduced, UiO-66-OH@Tb can be developed as ratiometric fluorescent probe with improved sensing performance, showing a wide detection range of 0 to 120 mg/L, and a low detection limit of 0.13 mg/L. UiO-66-OH@Tb can also be fabricated into composite film to function as visual sensing material of His. This work can provide instructions for the development of other fluorescent sensors.

A Chiral Nanocomplex for Multitarget Therapy to Alleviate Neuropathology and Rescue Alzheimer's Cognitive Deficits.

Alzheimer's disease (AD) is a severe neurodegenerative condition characterized by inflammation, beta-amyloid (Aβ) plaques, and neurodegeneration, which currently lack effective treatments. Chiral nanomaterials have emerged as a promising option for treating neurodegenerative disorders due to their high biocompatibility, strong sustained release ability, and specific enantiomer selectivity. The development of a stimulus-responsive chiral nanomaterial, UiO-66-NH2 @l-MoS2 QDs@PA-Ni (MSP-U), for the treatment of AD is reported. MSP-U is found to stimulate neural stem cell (NSCs) differentiation, promote in situ hydrogen (H2 ) production, and clear Aβ plaques. l-MoS2 QDs modified with l-Cysteine (l-Cys) effectively enhance the differentiation of NSCs into neurons through circularly polarized near-infrared radiation. Doped-phytic acid nickel (PA-Ni) improves the activity of l-MoS2 QDs in scavenging reactive oxygen species at the lesion site via photocatalytic H2 production. Loading l-MoS2 QDs with UiO-66 type metal oxide suppresses electron-hole recombination effect, thereby achieving rapid charge separation and improving transport of photogenerated electrons, leading to significantly improved H2 production efficiency. The photothermal effect of MSP-U also clears the generated Aβ plaques. In vivo evaluations show that MSP-U improves spatial cognition and memory, suggesting a promising potential candidate for the treatment of AD using chiral nanomaterials.

Effects of MOFs size and functional group on the pore structure and performance of thin-film nanocomposite membranes

Incorporation of nanomaterials into the selective layer during the interfacial polymerization process was an effective way to improve the perm-selectivity of the membranes. In this study, the piperazine enriched templates assisted interfacial polymerization method was proposed to enhance the salts rejection of thin-film nanocomposite (TFN) membranes. The mono-dispersed UiO-66 type MOFs with high amine adsorption ability were utilized as templates to increase the reaction region and promote the participation of piperazine (PIP) during the interfacial polymerization reaction, resulting in a denser polyamide (PA) layer with weaker surface electronegativity and higher nitrogen-containing group contents. The TFN membranes prepared with 236 nm UiO-66-OH and PIP concentration of 0.35 w/v% exhibited smaller mean pore size (0.636 nm) and reduced surface zeta potential (−26.0 mV) compared to the pristine TFC membranes (0.667 nm and −31.1 mV). Consequently, the rejection of 10 mM MgCl2, MgSO4 and Na2SO4 was increased from 44.7%, 97.7% and 98.3% to 84.3%, 99.2% and 99.5%, respectively, while the pure water flux was slightly decreased from 53.5 L m−1 h−1 to 37.4 L m−1 h−1 at 0.3 MPa. In addition, the size and functional group of the MOFs were found to have significant impacts on the pore structure and performance of the TFN membranes. The increasing of reaction region with relatively large MOFs and higher absorption ability were beneficial to obtain a thicker PA layer, while strong interaction between MOFs and PA oligomers was unfavorable for PA chain packing. Therefore, the TFN membranes prepared with UiO-66-NO2 exhibited a much narrow size distribution and high rejection to all salts, whether by divalent cationic salt or divalent anion salts, i.e., MgCl2 of 95.5%, MgSO4 of 98.9% and Na2SO4 of 99.1%, and the pure water flux was 28.6 L m−1 h−1 at 0.3 MPa. These results illustrated the influences of MOFs size and functional group on the interfacial polymerization process, which was crucial for the TFN membranes preparation.

Manipulating Lewis acid–base interactions in metal-organic frameworks for optimizing zinc-ion diffusion, deposition, and reaction behaviors

The dendrite growth and side reactions of Zn anodes severely impair the performance of aqueous rechargeable Zn metal batteries. Although various artificial protective layers (APLs) have been developed to address these issues, the engineering of multifunctional APLs at the molecular level remains a challenge. Herein, a strategy of manipulating the Lewis acid–base interactions at the molecular level within metal-organic frameworks (MOFs) was conducted to optimize the Zn2+ diffusion, deposition, and reaction behaviors for stabilizing Zn anodes. A series of APLs based on isostructural UiO-66 type MOFs with different functional groups (–NH2, –OH, –SO3H, and –COOH) were developed to systematically study the influence of different host-guest interactions for zinc deposition. The results show that the more Lewis base chemical groups result in the improved ability of MOFs in trapping Zn2+, transporting Zn2+, accelerating the desolvation of Zn2+, regulating pH values, and decreasing the side reactions, rendering suppressed dendrite growth. Thus, UiO-66-2COOH shows the best performance in regulating Zn2+ deposition, delivering an excellent Zn plating/stripping cycling of up to 2700 h at 1 mAh/cm2 and 1600 h at 5 mAh/cm2, as well as full cells with remarkably improved C-rate and cycling performance.

Utilizing Metal-Thiocatecholate Functionalized UiO-66 Framework for Photocatalytic Hydrogen Evolution Reaction.

Exploiting clean energy is essential for sustainable development and sunlight-driven photocatalytic water splitting represents one of the most promising approaches toward this goal. Metal-organic frameworks (MOFs) are competent photocatalysts owing to their tailorable functionality, well-defined structure, and high porosity. Yet, the introduction of the unambiguous metal-centered active site into MOFs is still challenging since framework motifs capable of anchoring metal ions firmly are lacking. Herein, the assembly using 1,4-dicarboxylbenzene-2,3-dithiol (H2 dcbdt) and Zr-Oxo clusters to give a thiol-functionalized UiO-66 type framework,UiO-66-dcbdt, is reported. The thiocatechols on the struts are allowed to capture transition metal (TM) ions to generateUiO-66-dcbdt-M(M = Fe, Ni, Cu) withunambiguous metal-thiocatecholate moieties for photocatalytic hydrogen evolution reaction (HER).UiO-66-dcbdt-Cuis found the best catalyst exhibiting an HER rate of 4.18mmol g-1 h-1 upon irradiation with photosensitizing Ru-polypyridyl complex. To skip the use of the external sensitizer,UiO-66-dcbdt-Cuis heterojunctioned with titanium dioxide (TiO2 ) and achieves an HER rate of 12.63mmol g-1 h-1 (32.3 times that of primitive TiO2 ). This work represents the first example of MOF assembly employing H2 dcbdtas the mere linker followed by chelation with TM ions and undoubtedly fuels the rational design of MOF photocatalystsbearing well-defined active sites.

Effect of Modulation and Functionalization of UiO-66 Type MOFs on Their Surface Thermodynamic Properties and Lewis Acid–Base Behavior

In this study, we investigated the surface thermodynamic properties of four MOF structures of the UiO-66 series, by employing seven molecular models, a thermal model, and three other methods using the inverse gas chromatography (IGC) technique at infinite dilution. We first determined the effect of the modulation of UiO-66 by an acid (e.g., formic acid and acetic acid) and on the other hand, we studied the effect of the functionalization of the organic linker by an amine group (NH2) on their dispersive component of the surface energy and on their Lewis acid–base properties. We found that all the studied MOFs presented an amphoteric character with a strong acidity whose acidity/basicity ratio is greater than 1 using all the models and methods in IGC. Moreover, the introduction of a modulator such as acetic acid or formic acid in the synthesis of these MOFs increased the number of structural defects and therefore increased the acidity of these MOFs. Similarly, the functionalization of the MOF by the NH2 group leads to an increase in the basicity constant of the functionalized MOF while remaining smaller than their acidity constant. In addition, the use of acids as modulators and amine groups as functional groups resulted in an increase in the dispersive component of the surface energy of the MOFs. Finally, comparing the results obtained by the different models and methods and based on the increasing order of the acidity of each MOF, it was clear that the thermal model resulted in more exact and precise values than the others. Our findings pave the way for the design and development of new acid catalysts based on UiO-66 structures.

Regulation and photocatalytic degradation mechanism of a hydroxyl modified UiO-66 type metal organic framework.

Photocatalytic performance can be effectively improved by modifying the functional groups on the organic ligands of metal organic frameworks (MOFs). Herein, the hydroxyl-modified UiO-66 type MOF: UIO-66-2OH(2,3), was successfully synthesized by the method of ligand exchange by the 2,3-dihydroxyterephthalic acid and UIO-66 as raw materials. The mechanism of photocatalytic degradation of methylene blue (MB) by UIO-66-2OH(2,3) shows that the hydroxyl functional group on the organic ligand regulates its electronegativity and expands its light absorption range. The decomposition of MB is carried out in multiple steps under the oxidation of the hydroxyl radical (˙OH). This research result shows the direction for guiding the synthesis of efficient photocatalysts and clarifying the light absorption of MOFs regulated by hydroxyl functional groups.

Ion conduction in Na＋ containing ionogels based on the UiO-66 metal organic framework

▪ conducting materials are critical to the development of solid-state sodium batteries which may enable the use of sodium metal anodes. Ionogels are hybrid liquid–solid electrolytes that are made by embedding an ionic liquid into a suitable solid framework. In this study, ionogels based on the UiO-66 type metal organic framework (MOF) porous structure were prepared. Three isostructural MOFs were synthesized and used: (i) the UiO-66 material, (ii) an amine functionalized MOF (UiO-66- ▪ ) and iii) a hydroxyl functionalized MOF (UiO-66- ▪ ). A mixture of sodium bis(fluorosulfonyl)imide (NaFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) was embedded in the pores of the MOFs. FTIR and conductivity spectroscopy were used to asses the interaction of the mobile species with the MOF structure as well as ion transport and electric relaxation properties of the materials. We found that the conductivity of the ionogels is strongly influenced by the functionalized linker used. The UiO-66- ▪ -based ionogels present an encouraging conductivity increase trend when sodium ions are present, whereas the UiO-66- ▪ -based ionogels present the highest conductivity in the order of 0.3 mScm−1 at 293 K, albeit this is very likely due to highly mobile protons. While further studies are needed to understand which species are dominating the ion conduction, this investigation offers an insight into the behavior of MOF-based ionogels and may guide further work in the field.

A luminescent Eu3+-functionalized MOF for sensitive and rapid detection of tetracycline antibiotics in swine wastewater and pig kidney

Tetracyclines (TCs), a type of antibiotics, are widely used in human therapy and animal husbandry. Public concerns about tetracyclines residues have been raised due to their negative impact on the environment and food, causing bacterias drug resistance and human health concerns. In this work, a luminescent europium MOF (EuUCBA) is constructed via post-synthetic attachment of Eu3+ into a UiO-66 type MOF. The luminescent of EuUCBA exhibits high stability in aqueous media in the pH range of 4–11. Among 36 common veterinary drugs, the synthesized probe is highly selective and sensitive to six tetracyclines with low detection limits of 0.118 μM, 0.228 μM, 0.102 μM, 0.138 μM, 0.206 μM, and 0.078 μM for oxytetracycline (OTC), chlortetracycline (CTC), methylenetetracycline (MTC), minocycline (MOC), tetracycline (TC), and doxycycline (DOXY), respectively. Furthermore, the probe shows good anti-interference ability and fast response. Finally, EuUCBA was successfully to detect DOXY in swine wastewater and pig kidney with good recoveries. This work provides an excellent fluorescent sensor for highly selective and rapid detection of TCs residues in wastewater and complex biological samples.

Hierarchical large-pore MOFs templated from poly(ethylene oxide)-b-polystyrene diblock copolymer with tuneable pore sizes.

Diblock copolymer poly(ethylene oxide)-b-poly(styrene) (PEO-b-PS) was adopted to template the synthesis of hierarchically porous Ce-based metal-organic frameworks (MOFs) for the first time. By extending the synergistic effect of Hofmeister ions and soft templates into the water-rich system, UiO-66 type Ce-MOFs with a mesopore size of about 15 nm were achieved. Mesopore size could be further tuned up to approximately 23 nm upon introducing 1,3,5-trimethylbenzene to the micelle core of PEO-b-PS.

The effect of non-ionic surfactants on the sustainable synthesis of selected MOFs

The MOFs selected in this work are NH2-MIL-53(Al), MIL-100(Fe) and UiO-66 type (Zr-BDC and NH2-Zr-BDC). We have tried to assist the sustainable synthesis of MOFs, at room temperature and in water as a solvent, with the presence of non-ionic surfactants: Pluronic F127 and P123. The parent MOFs prepared at room temperature with water solvent commonly grow in the form of agglomerates of small crystallites in all cases. The X ray diffraction patterns of surfactant templated NH2-MIL-53(Al) with F127 and MIL-100(Fe) with F127 and P123 show some differences in peak intensity indicating preferential crystal growth along one direction. This effect was confirmed by scanning and transmission electron microscopy, yielding long shaped crystals with more or less uniform morphology, notably larger than the parent MOFs. In the case of UiO-66 type (Zr-BDC and NH2-Zr-BDC) MOFs, the X ray diffraction profiles of the parent and the surfactant templated MOFs do not show noticeable difference, which might be due to the semi-amorphous nature of these MOFs. However, the scanning and transmission electron microscopy images show larger particles in surfactant templated UiO-66 type Zr-MOFs compared to their parent counterparts.

Amino-functionalized UiO-66 as a Novel Adsorbent for Removal of Perfluorooctane Sulfonate from Aqueous Solution

Perfluorinated compounds are a class of emerging organic water contaminants that pose risk to human health and the natural environment. Perfluorooctane sulfonate (PFOS) is the most extensively used perfluorinated compound worldwide owing to its applications in various fields. In this study, UiO-66 and UiO-66-NH2 were synthesized via a solvothermal method that uses hydrochloric acid. These were evaluated as potential adsorbents to remove PFOS from an aqueous solution. UiO-66-NH2 showed the highest adsorption capacity because its affinity for PFOS anions in water is improved despite the decrease in specific surface area caused by the introduction of amino groups. Previous studies have reported that a UiO-66 type framework is an effective PFOS adsorbent. This study presents a novel approach to enhance its adsorption performance by amino group modification.

Application of hard and soft acid base theory to uncover the destructiveness of Lewis bases to UiO-66 type metal organic frameworks in aqueous solutions

Metal organic frameworks (MOFs), emerging adsorbents and catalysts in the wastewater treatment field, are subject to destruction by Lewis bases in wastewater, such as F− and PO43−.

Modulation of the Bifunctional CrVI to CrIII Photoreduction and Adsorption Capacity in ZrIV and TiIV Benchmark Metal-Organic Frameworks

The presence of hexavalent chromium water pollution is a growing global concern. Among the currently applied technologies to remove CrVI, its adsorption and photocatalytic reduction to CrIII less mobile and toxic forms are the most appealing because of their simplicity, reusability, and low energy consumption. However, little attention has been paid to bifunctional catalysts, that is, materials that can reduce CrVI to CrIII and retain both hexavalent and trivalent chromium species at the same time. In this work, the dual CrVI adsorption–reduction capacity of two iconic photoactive water-stable zirconium and titanium-based metal–organic frameworks (MOFs) has been investigated: UiO-66-NH2 and MIL-125. The bifunctionality of photoactive MOFs depends on different parameters, such as the particle size in MIL-125 or organic linker functionalization/defective positions in UiO-66 type sorbents. For instance, the presence of organic linker defects in UiO-66 has shown to be detrimental for the chromium photoreduction but beneficial for the retention of the CrIII phototransformed species. Both compounds are able to retain from 90 to 98% of the initial chromium present at acidic solutions as well as immobilize the reduced CrIII species, demonstrating the suitability of the materials for CrVI environmental remediation. In addition, it has been demonstrated that adsorption can be carried out also in a continuous flux mode through a diluted photoactive MOF/sand chromatographic column. The obtained results open the perspective to assess the bifunctional sorption and photoreduction ability of a plethora of MOF materials that have been applied for chromium capture and photoreduction purposes. In parallel, this work opens the perspective to develop specific chemical encoding strategies within MOFs to transfer this bifunctionality to other related water remediation applications.

Roles of defects and linker exchange in phosphate adsorption on UiO-66 type metal organic frameworks: Influence of phosphate concentration

Recently, UiO-66 type metal organic frameworks (MOFs) have been studied as adsorbents for phosphate removal from wastewater; however, the adsorption mechanism with different concentrations of phosphate, especially the roles of defects and linker exchange, are not entirely clear. In this work, the phosphate adsorption mechanism in HCl-UiO-66 and HCl-NH2-UiO-66 were examined by testing the relationship between the adsorbed phosphate and released linker in the adsorption process. Adsorption kinetics studies (3.0 mM phosphate solution) and adsorption isotherm analyses (0.3–6.0 mM phosphate solution) revealed highly linear relationships (R2 = 0.8949–0.9978) between the adsorbed phosphate and released linker for both adsorbents. Further analysis showed that when the adsorbed phosphate was lower than 0.56 mmol/g for HCl-UiO-66 and 0.51 mmol/g for HCl-NH2-UiO-66, phosphate was preferentially adsorbed on the defect sites in the MOFs with no linker release. However, when the adsorbed phosphate exceeded these levels, the defects were saturated by phosphate and linker exchange became the major adsorption mechanism. Based on density functional theory calculations, the obtained strengths of the linkers (H2BDC: Terephthalic acid; NH2-H2BDC: 2-Aminoterephthalic Acid; NO2-H2BDC: 2-Nitroterephthalic Acid) and phosphate species as Lewis bases fall in the order, PO43- > HPO42- > NH2-BDC2- > BDC2- > H2PO4- > NO2-BDC2- > H3PO4, which clearly evidences why linkers can be exchanged by phosphate. Given the propensity for ligand exchange and the resulting structural destabilization, UiO-66 type MOFs is not suggested as ideal adsorbents for phosphate removal from wastewater with high phosphate concentrations.