UiO-66 Series Research Articles

Thermochemical adsorption heat storage performance of functionalized UiO-66: Molecular simulation method

UiO-66 has broad application prospects in thermochemical adsorption heat storage owing to its great adsorption performance and stability. To further improve its performance, UiO-66 can be functionalized. Nevertheless, the adsorption and diffusion mechanism of UiO-66 and its functionalized structures is still unclear. Therefore, in this paper, it investigated the adsorption and diffusion performance of the UiO-66 series by molecular simulation. The effects of different functional groups were analysed, and the underlying mechanism was revealed. The results showed that adding –OH, –NH2, and –NH3+Cl- groups improved the adsorption capacity of UiO-66 at low pressure by 2.16, 3.22 and 4.25 times respectively, whereas adding –NO2 and −(OMe)2 groups reduced it by 46.05% and 86.84%. The adsorbent-water interaction was the strongest for UiO-66-NH3+Cl-, while UiO-66-(OMe)2 exhibited the weakest interaction. For the UiO-66 series, water molecules were preferentially adsorbed near the zirconium clusters, –OH, –NH2, and –NH3+Cl- groups. Then, they gradually filled around the organic ligands, and a very small amount gathered around the –NO2 and −(OMe)2 groups. Owing to the limitation of the pore volume, the water diffusion coefficient of all the structures initially increased and then decreased with the increase of water loading.

Novel Hydrophobic Functionalized UiO-66 Series: Synthesis, Characterization, and Evaluation of Their Structural and Physical-Chemical Properties.

A novel set of four functionalized hydrophobic UiO-66-NHR series were synthesized through postsynthetic procedures, utilizing various benzoyl chlorides and UiO-66-NH2 as starting materials. This synthesis method was carried out by employing p- (1) and o-toluoyl (2), as well as 2- (3) and 4-fluorobenzoyl (4) substituents. The analysis of the resulting compounds was performed using conventional spectroscopic methods such as FT-IR and 1H NMR to quantify the conversion rate into amide. Furthermore, SEM and XPS techniques were employed for morphological and surface analysis. Finally, the evaluation of the chemical stability and contact angle using the sessile drop method was performed to evaluate the technological potential of these compounds for application in aqueous and acidic media (such as selective separation of different metals and wastewater recovery).

Hierarchical porous UiO-66 composites modified by dual competitive strategy for adsorption of oxytetracycline

Adsorption is a popular technology for solving water-pollution problems because it is highly efficient, affordable and environmentally friendly. In this study, a dual competition strategy was developed to improve oxytetracycline adsorption by modulating the UiO-66 defects. A series of defect-rich hierarchical porous UiO-66 was prepared using the competitive strategy of bi-metal (Zn2+/Zr4+) and bi-ligand (terephthalic acid/monocarboxylic acid). Compared with the pristine UiO-66, the defect-rich hierarchical porous UiO-66 has a higher adsorption efficiency and faster adsorption rate. Among them, the greatest adsorption ability of But-HP-UiO-66 was 209.97 mg∙g−1 at pH= 6.0, which was 9.89 times greater than UiO-66. The kinetic and isotherm fitting results showed that the adsorption was consistent with the Elovich and Freundlich models. According to the response surface model design based on four factors (OTC concentration, pH, humic acid and SO42- intensity), But-HP-UiO-66 exhibited an excellent adsorption effect and strong anti-jamming ability. The prominent advantages of this composite are its rich pore structure and abundant defects. The adsorption mechanism showed that the electrostatic interactions, metal-organic complexation, pore adsorption, hydrogen bonding and π-π interactions performed vital functions. This study provides a promising method for manufacturing strongly hierarchical porous MOFs and strengthens their potential applications in antibiotic elimination.

Imperfect perfection: Selective induction of CO2 during diffusion in mixed matrix membranes

Metal-organic frameworks (MOFs) are one of the optimal choice to be endowed for designing high-performance CO2 separation membranes as the fillers, ascribing their unprecedented tunability and chemical functionalities. However, while pursuing more types of MOFs, researchers have slightly explored their inherent properties. Thus, we incorporated missing-linker defects into Zirconium Metal−Organic Framework for tailoring the superior CO2 transport channel through tune their microporosity. And a series of defect-engineered UiO-66 (UiO-AcOH) fillers were synthesized and mingled into PIM-based matrix with large free volume. Resistance model simulations and gas permeation tests confirmed that the defective UiO-66 can greatly improved the competitive adsorption of the dispersed phase in Mixed Matrix Membranes (MMMs), offering more degree of freedom for the transportation of CO2. At the optimal ratio, the CO2 permeability of the UiO-AcOH-1.4/PIM-15 wt% MMMs increased nearly 3.5 times (CO2 =11261 Barrer, and the CO2/N2 selectivity is 26, almost increasing 23% contrasted pure film. Moreover, MMMs possess excellent long-term working stability and anti-aging properties, showing excellent gas separation performance.

Synthesis of CNT/UiO-66-NH2 adsorbent and the selective adsorption of gallium in solution

To alleviate the supply–demand contradiction of gallium metal (Ga), this study reports a method of preparing 2-CNT/UiO-66-NH2 composite materials by combining carbon nanotubes (CNTs) with UiO-66 series metal–organic frameworks (MOFs) to improve the recovery and utilization efficiency of Ga in solution. The adsorbent material is used for selective adsorption and recovery of Ga in aqueous solutions. The physical properties of the composite adsorbent, such as morphology, structure, and elemental composition, were explored by analyzing the surface characteristics of the samples. The impacts of variables like the amount of adsorbent used, time, solution concentration, pH value, and coexisting ions on adsorption efficiency were explored during the experiment. The results indicate that ion exchange and chelation play a major role in the adsorption of Ga by 2-CNT/UiO-66-NH2, and Ga ions can be separated and recovered from the mixed solution through selective adsorption. At 313 K and pH = 8, the greatest amount of adsorption is 925.44 mg/g, and the rate at which it is absorbed can reach 99% when the adsorption time is only 1 h. The hybrid absorbent generally has a high adsorption efficiency and good selective adsorption performance for Ga, providing more efficient and economical technical assistance for the future recovery and exploitation of Ga supplies.

Solar-driven gas phase photocatalytic CO2 methanation by multimetallic UiO-66 solids decorated with RuOx nanoparticles

As there is an urgent need to produce solar fuels from CO2, we here report on the development of a series of multimetallic UiO-66(Zr/Ce/Ti) solids-supported RuOx nanoparticles as photocatalysts for selective gas phase CO2 methanation by H2 under simulated sunlight irradiation. The trimetallic UiO-66(Zr/Ce/Ti) based-photocatalyst exhibits higher activity (1,900 μmol g−1 of CH4 after 22 h) than analogous mono- [UiO-66(Zr) or UiO-66(Ce)] and bimetallic [UiO-66(Zr/Ce) or UiO-66(Zr/Ti)] derivatives, as well as higher than previous reports on metal–organic frameworks (MOFs). The experimental evidence on the observed order of photocatalytic activity and insights into the occurrence of a dual photochemical and photothermal mechanism for the most active trimetallic sample were obtained by means of spectroscopic techniques including fluorescence and laser flash photolysis, photoelectrochemical and additional photocatalytic measurements. This study exemplifies the benefits of developing multimetallic MOF-supported metal nanoparticles to achieve high photocatalytic activity for solar-driven gas phase CO2 conversion.

Weak Bonds, Strong Effects: Enhancing the Separation Performance of UiO-66 toward Chlorobenzenes via Halogen Bonding

Halogen bonding (HaB) is a weak interaction that assists in the recognition of nucleophilic molecules. However, HaB elements are currently under-investigated as a part of functional materials in separation science. Herein, we develop a novel approach for introducing HaB elements into UiO-66 to fine-tune the adsorption properties toward chlorobenzenes (CBs). A series of UiO-66 containing various contents of 2-iodoterephtalic acid (I-TA) (0%, 33%, 50%, 67%, and 100%) was prepared, characterized, and applied for the selective removal of CB contaminants from nonchlorinated aromatic analogues that cannot be separated by common distillation. Investigation of the structure–property relationship revealed that the highest adsorption capacity was achieved in the case of UiO-66 loaded with 50% I-TA (UiO-66-Iopt), and this was attributed to the balance between the number of HaB elements and the surface area of the UiO-66 structure. According to density functional theory calculations, the formation of a conjugate between dichlorobenzene and UiO-66-Iopt was more energetically favorable (up to 1.7 kcal/mol) than that of the corresponding conjugate with UiO-66. The formation of HaBs was experimentally verified by UV–vis, Raman, and X-ray photoelectron spectroscopies. To obtain functional materials for separation applications, waste polyethylene terephthalate (PET) was used as a support and feedstock for the surface-assisted growth of UiO-66-Iopt. The as-prepared PET@UiO-66-Iopt exhibited a close-to-perfect selectivity and reusability for the separation of a wide range of CBs from nonchlorinated aromatic analogues.

In Operando Spectroscopic Ellipsometry Investigation of MOF Thin Films for the Selective Capture of Acetic Acid.

The emission of polar volatile organic compounds (VOCs) is a major worldwide concern of air quality and equally impacts the preservation of cultural heritage (CH). The challenge is to design highly efficient adsorbents able to selectively capture traces of VOCs such as acetic acid (AA) in the presence of relative humidity (RH) normally found at storage in museums (40-80%). Although the selective capture of VOCs over water is still challenging, metal-organic frameworks (MOFs) possess highly tunable features (Lewis, Bronsted, or redox metal sites, functional groups, hydrophobicity, etc.) suitable to selectively capture a large variety of VOCs. In this context, we have explored the adsorption efficiency of a series of MOFs thin films (ZIF-8(Zn), MIL-101(Cr), and UiO-66(Zr)-2CF3) for the selective capture of AA based on a UV/vis and FT-IR spectroscopic ellipsometry in operando study (2-6% of relative pressure of AA under 40% of RH), namely conditions close to the realistic environmental storage conditions of cultural artifacts. For that purpose, optical quality thin films of MOFs were prepared by dip-coating, and their AA adsorption capacity and selectivity were evaluated under humid conditions by measuring the variation of the refractive index as a function of the vapor pressures while the chemical nature of the coadsorbed analytes (water and AA) was identified by FT-IR ellipsometry. While thin films of ZIF-8(Zn) strongly degraded upon exposure to AA/water vapors, films of MIL-101(Cr) and UiO-66(Zr)-2CF3 present a high chemical stability under those conditions. It was shown that MIL-101(Cr) presents a high AA adsorption capacity due to its high pore volume but exhibits a poor AA adsorption selectivity under humid conditions. In contrast, UiO-66(Zr)-2CF3 was shown to overpass MIL-101(Cr) in terms of AA/H2O adsorption selectivity and AA adsorption/desorption cycling stability because of its high hydrophobic character, suitable pore size for adequate confinement, and specific interactions.

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.

Preparation of Functionalized Zr-Based MOFs and MOFs/GO for Efficient Removal of 1,3-Butadiene from Cigarette Smoke.

Removal of 1,3-butadiene from cigarette smoke plays an important role in human health and environmental protection. Herein, a series of UiO-66 X% containing different ratios of the -NH2 group was synthesized via the solvothermal method by using terephthalic acid (H2BDC) and 2-aminoterephthalic acid (NH2-BDC) as ligands. Using GO as support, a series of UiO-66-NH2/GO Y% were prepared by controlling the ratio of UiO-66-NH2 and GO. The effects of -NH2 and GO contents on the structure and composition of MOFs were investigated. Finally, the different -NH2 contents of UiO-66 X% and the different GO contents of UiO-66-NH2/GO Y% were applied in 1,3-butadiene removal from cigarette smoke. The results showed that UiO-66 X% with the higher contents of -NH2 showed a higher rate of 1,3-butadiene removal, and UiO-66-NH2/GO Y% with the GO contents of 5% showed the highest removal rate of about 33.85%, which was 25.54% higher than that of activated carbon. In addition, the saturation capacity of the adsorbent materials for 1,3-butadiene was as high as 210.01-239.54 mg/g, showing great potential in reducing harmful components in cigarette smoke and environmental protection.

Synthesis of UiO-66 series metal–organic framework composites and the adsorption effect on gallium

It is an urgent problem to alleviate the contradiction between the supply and demand of gallium (Ga) resources and improve the extraction and utilization efficiency of Ga resources. The GO/UiO-66-NH2 composite adsorbent was synthesized by hydrothermal synthesis of graphene oxide (GO) and UiO-66-NH2 series metal–organic skeleton, which was employed for efficient recovery and extraction of Ga in solution. The morphology, structure, elemental composition, and chemical properties of the composite adsorbent were studied by a series of batch experiments, respectively. The effects of the amount of adsorbent, adsorption time, initial concentration, and pH value of the solution on the adsorption effect were investigated. Results found that the adsorption mechanism of Ga by 4-GO/UiO-66-NH2 is mainly ion exchange forming chelate, accompanied by electrostatic interaction. The optimized adsorption conditions for reaching the saturated adsorption capacity of 661.67 mg/g Ga were found to be pH 9 and the temperature 313 K. The results of thermodynamic study pointed out the adsorption of Ga is spontaneous and feasible. The aforementioned results demonstrate that GO/UiO-66-NH2 composite adsorbent has strong adsorption performance and application potential for the recovery and exploitation of Ga, offering practical and theoretical support for the future development and utilization of Ga resources.

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.

Ferrocene-boosting Zr-MOFs for efficient photocatalytic CO2 reduction: A trade-off between enhancing LMCT and frustrating Lewis acid

The introduction of rich-electron ligands is a promising strategy to improve the ligand-to-metal charge transfer (LMCT) ability of metal–organic frameworks (MOFs) for efficient photocatalytic CO2 reduction reactions (CO2RR), while the resulting impaired Lewis acid sites go against stable bonding with CO2 and hinder the electron transfering to CO2. It is thus the key to search a trade-off between increasing LMCT and frustrating Lewis acid. Herein, the ferrocene (Fc) modified UiO-66 series MOFs, NH2-UiO-66-Fc, have been prepared to optimize LMCT for boosting CO2RR through a simple solvent-assisted ligand incorporation (SALI) method. Theoretical calculation and systematic experiments, including photoelectrochemical measures, in situ electron paramagnetic resonance, fluorescence probe analysis and X-ray photoelectron spectroscopy indicate that with increasing Fc content, the LMCT energy of MOFs significantly decreases from 2.66 to 2.10 eV based on the established electron transfer double-channel mechanism, while the Lewis acidity of Zr sites reduces with the CO2 adsorption energy (Ead) ranging from −1.061 to −0.632 eV. Through introducing an optimal Fc content, NH2-UiO-66-Fc(2.0) integrating satisfactory LMCT ability and Lewis acidity shows superior photocatalytic CO2RR performance (CO yield: 90.65 μmol·g−1·h−1), about 13 times higher than that of the unmodified MOF and superior to most reported pristine MOF photocatalysts. DFT calculation demonstrates that the excellent performance of NH2-UiO-66-Fc(2.0) is attributed to the lowest energy barrier of 1.50 eV for the rate-limiting step of *COOH formation. In this work, such a simple post-modification strategy for facilitating the whole electron transfer path of photocatalytic CO2RR will provide a new way to construct high-performance MOFs-based CO2RR photocatalysts.

Comparative Studies on the Proton Conductivities of Hafnium-Based Metal-Organic Frameworks and Related Chitosan or Nafion Composite Membranes.

Hafnium (Hf)-based UiO-66 series metal-organic frameworks (MOFs) have been widely studied on gas storage, gas separation, reduction reaction, and other aspects since they were first prepared in 2012, but there are few studies on proton conductivity. In this work, one Hf-based MOF, Hf-UiO-66-fum showing UiO-66 structure, also known as MOF-801-Hf, was synthesized at room temperature using cheap fumaric acid as the bridging ligand, and then imidazole units were successfully introduced into MOF-801-Hf to obatin a doped product, Im@MOF-801-Hf. Note that both MOF-801-Hf and Im@MOF-801-Hf demonstrate excellent thermal, water, and acid-base stabilities. Expectedly, the maximum proton conductivity (σ) of Im@MOF-801-Hf (1.46 × 10-2 S·cm-1) is nearly 4 times greater than that of MOF-801-Hf (3.98 × 10-3 S·cm-1) under 100 °C and 98% relative humidity (RH). To explore their possible practical application value, we doped them into chitosan (CS) or Nafion membranes as fillers, namely, CS/MOF-801-Hf-X, CS/Im@MOF-801-Hf-Y, and Nafion/MOF-801-Hf-Z (X, Y, and Z are the doping percentages of MOF in the membrane, respectively). Intriguingly, it was found that CS/MOF-801-Hf-6 and CS/Im@MOF-801-Hf-4 indicated the highest σ values of 1.73 × 10-2 and 2.14 × 10-2 S·cm-1, respectively, under 100 °C and 98% RH and Nafion/MOF-801-Hf-9 also revealed a high σ value of 4.87 × 10-2 S·cm-1 under 80 °C and 98% RH, which showed varying degrees of enhancement compared to the original MOFs or pure CS and Nafion membranes. Our study illustrates that these Hf-based MOFs and related composite membranes offer great potential in electrochemical fields.

Extraction of metals by MOFs in simulation aqueous solution from nuclear plants

Since the use of traditional energy, such as oil and coal, has brought a very negative impact on the earth’s environment, relevant researchers have been carrying out relevant studies, hoping to find cleaner energy to replace the traditional energy for the relevant application. In this project, we synthesized a UiO-66 series MOFs material as the efficient absorbent for U extraction from the wastewater which is generated by nuclear energy plants. The UiO-66 product was then modified with Mn and amino and the Mn-doped Mn-UiO-66-NH2 was formed successfully. Through scanning electron microscope (SEM) investigation, it was found that the novel absorbent showed a spherical structure, with being core–shell structure. We then examined the extraction performance of the absorbent on U and the results showed that under low pH conditions (pH = 2–4), the extraction capacity was low. However, when the pH values increased to 5.5, the qe reached over 140 mg U/g absorbent. The results showed that the extraction performance on U was increased by introducing the additional metal element Mn and amino group and thus the new material is valuable in nuclear wastewater treatment.

Copper(II) invigorated EHU-30 for continuous electroreduction of CO2 into value-added chemicals

The doping of zirconium based EHU-30 and EHU-30-NH2 metal–organic frameworks with copper(II) yielded a homogeneous distribution of the dopant with a copper/zirconium ratio of 0.04–0.05. The doping mechanism is analysed by chemical analysis, microstructural analysis and pair distribution function (PDF) analysis of synchrotron total scattering data in order to get deeper insight into the local structure. According to these data, the Cu(II) atoms are assembled within the secondary building unit by a transmetalation reaction, contrarily to UiO-66 series in which the post-synthetic metalation of the MOF takes place through chemical anchorage. The resulting materials doubled the overall performance of the parent compounds for the CO2 electroreduction, while retained stable the performance during continuous transformation reaction.

Influence of the defects on selective hydrogenation of cinnamaldehyde to cinnamyl alcohol over UiO-66 supported Pt catalysts

UiO-66 supported metal catalysts have shown high catalytic activity and selectivity to cinnamyl alcohol (COL) in the selective hydrogenation (SHYD) of cinnamaldehyde (CAL), but the roles of missing-linker defects (MLDs) in UiO-66 on the catalytic performance of the UiO-66 supported metal catalysts have less been reported. Here, UiO-66 supports with the different amount of MLDs were used as the supports, and three series of UiO-66 supported Pt (Pt/U) catalysts were prepared by sol-impregnation, wet-impregnation as well as in-situ encapsulation methods, respectively. The influences of the MLDs in UiO-66 on the catalytic properties of the prepared Pt/U catalysts in the SHYD of CAL were investigated. The series of Pt/U-720 catalysts with the more MLDs showed higher CAL conversion and selectivity to COL than the corresponding Pt/U-F catalysts with fewer MLDs. The different preparing methods affect the location and dispersion of Pt species on UiO-66 supports and the metal-support interaction, but the location of the supported Pt species on UiO-66 is the critical factor affecting the catalytic properties of Pt/U catalysts. The presence of the MLDs in UiO-66 is the key to preparing UiO-66 supported Pt catalysts with high SHYD performance.

Solid Lewis acid-base pair catalysts constructed by regulations on defects of UiO-66 for the catalytic hydrogenation of cinnamaldehyde

A series of highly-defective UiO-66 were synthesized and utilized as catalyst in the hydrogenation of cinnamaldehyde (CALD) to cinnamylalcohol (CALH) in isopropanol. The physico-chemical properties of the catalysts were characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis and N2 adsorption-desorption. It was found that there are two kinds of atomic Lewis acid-base pairs existing in the defective UiO-66, exactly Zr4+-O2- and Zr4+-OH-, which are active sites for CALD hydrogenation to form CALH. UiO-66–0.3 with the most defects shows a much higher reaction rate constant, which is 5.5 times that of UiO-66–2.0, and gives the best CALD conversion of 85.5% and CALH selectivity of 94.0% at 140 ℃ after 3 h. The acid-base synergistic catalysis mechanism was proposed. Moreover, the defective UiO-66 showed good recyclability for up to 7 cycles with retention of catalytic activity as well as structural stability.

Superprotonic Conductivity of UiO-66 with Missing-Linker Defects in Aqua-Ammonia Vapor.

The design and preparation of proton-conducting metal-organic frameworks (MOFs) with superconductivity are of significance for the proton-exchange membrane fuel cell (PEMFC). Introducing functional structural defects to enhance proton conductivity is a good approach. Here, we synthesized a series of UiO-66 (first synthesized in the University of Oslo) with missing-linker defects and investigated the effect of defect numbers on the proton conductivity of the samples. Among them, 60-UiO-66-1.8 (60 represents the synthesis temperature and 1.8 the number of defects) prepared with 3-mercaptopropionic acid as a modulator has the best proton conductivity, which is 3 × 10-2 S cm-1 at 100 °C and under 98% relative humidity (RH). The acidic sites induced by missing-linker defects further promote the chemisorption of ammonia molecules, resulting in the formation of a richer hydrogen-bond network and hence boosting the proton conductivity to 1.04 × 10-1 S cm-1 at 80 °C, which is one of the highest values among the reported MOF-based proton conductor. Therefore, this work provides a new strategy for enhancing proton conduction in MOF-based materials.

Integration of mixed ligand into a multivariate metal-organic framework for enhanced UV-light photocatalytic degradation of Rhodamine B

BackgroundThe photocatalytic activity of a series of UIO-66 modified MOFs viz. UiO-66-NO2 [1], UiO-66-NH2 [2] and UiO-66-NO2/UiO-66-NH2 [3] materials for photocatalytic degradation of model aromatic dye Rhodamine B [Rh B] have been assessed. MethodsThe photocatalysis experiments indicated that the most efficient photocatalyst for the Rh B degradation is 3 which achieved 95.5% degradation under UV light irradiation and displayed excellent recyclability and reusability when compared to 1 and 2. The trapping experiments indicated that O2˙− radical anion is main ROS generated during the photocatalysis play major role in the Rh B degradation. The LC-MS experiments and band gap calculations have been performed which suggested initial protection of xanthene unit and confirmed the major contribution of O2˙− radical anion generated by ligand to ligand transition in 3 for photodegradation of Rh B. Significant FindingsThis facile approach inculcating benefits of mixed ligands in multivariate metal-organic framework, lays a new pathway to design effective photocatalytic systems for safe and sustainable degradation of aromatic dyes. This strategy led to suppression in rate of hole-electron pair recombination that concomitantly uplifted photocatalytic efficiency over single component counterparts.