Benzene Dicarboxylate Research Articles

Ag nanoparticles incorporated metal organic framework (Ag@ZnBDC): Highly sensitive and selective detection of Hg2+ ions

Heavy metal ions (HMIs) pollutants pose remarkable hazards to humans and the environment. Their toxicity is a concern for both aquatic life and humans. HMIs directly threaten humans when consumed through drinking water or aquatic species such as fish. Therefore, detecting, quantifying, and removing these pollutants from water sources is necessary. In this study, we fabricated a highly selective and sensitive Hg2+ ion electrochemical sensor using a solvothermally synthesized composite of silver nanoparticles (Ag NPs) and zinc benzene dicarboxylate (ZnBDC) (Ag@ZnBDC) metal–organic framework (MOF) at trace levels. The synthesized Ag@ZnBDC MOFs composite was studied using various characterization techniques: structural, spectroscopic, thermal, Brunauer-Emmett-Teller surface area, morphological, elemental, and electrochemical techniques. The electrochemical sensor was fabricated by drop-casting the Ag@ZnBDC composite onto a glassy carbon electrode, and its sensing properties were evaluated using cyclic voltammetry and differential pulse voltammetry techniques. Remarkably, the sensor exclusively and highly selectively responded to Hg2+ ions among Cd2+, Cr3+, Cu2+, Fe3+, and Pb2+ ions at a concentration of 1 μM. The Ag@ZnBDC sensor showed a limit of detection of 4.16 nM in the linear response within the concentration range of 1–10 nM for Hg2+ ions.

A comprehensive study of ferroelectric, dielectric and optical properties of europium-doped SBD metal- organic framework

The synthesis of Europium-doped Strontium based benzene dicarboxylate dimethylformamide metal–organic framework- Eu([Sr(μ-BDC)(DMF)])- with short form as Eu:SBD@MOF was carried out using the solvothermal method. The investigation involved characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), CHN analysis, and energy-dispersive X-ray (EDX) elemental analysis. The results confirmed the formation of metal–organic crystals in the framework. The XRD characterization shows good alignment with the simulated pattern of SBD. The experimental absorption spectrum displays distinct transitions of the Eu (III) ion alongside transitions of the ligands. Calculations of line strengths for all observed transitions have been conducted. The Judd-Ofelt theory has been employed to determine intensity parameters, transition probabilities, branching ratios, and radiative lifetimes for the Eu: SBD@MOF. These JO parameters further aid in calculating various excited state properties. When excited by ultraviolet and visible photons, the complex exhibits emission in the red region respectively. The crystal’s dielectric loss and dielectric constant were investigated for their frequency dependence. It was observed that by virtue of DMF, a molecule linked to the crystal, a synthesized MOF exhibits a good dielectric characteristic and when the temperature is raised to 558 K, the dielectric constant drops sharply as DMF molecule could not stand after this temperature. Further ferroelectric studies reveal that the Eu: SBD@MOF has maximum polarization of 0.27 C/cm2 which is greater than Rochelle salt and other MOF’s. Exploring the broadband dielectric response of metal–organic frameworks (MOFs) open up new avenues in research, potentially leading to innovative applications in smart optoelectronics, terahertz sensors, high-speed telecommunications, and microelectronics.

Synthesis of novel Cu/Fe based benzene Dicarboxylate (BDC) metal organic frameworks and investigations into their optical and electrochemical properties

In the recent past Metal-organic frameworks (MOFs) based thin films have demonstrated superior performance in various technological applications such as optical and optoelectronic devices, electrochemical energy storage, catalysis, and sensing. Herein we report tuning the optical performance of stable complexes using Cu and Fe metal ions with carboxylate benzene dicarboxylic (BDC), leading toward the formation of novel MOF structures. The formation of Cu-BDC and Fe-BDC were confirmed by XRD and SEM studies. The thermal stability of two MOFs was investigated, indicating that, the Cu-BDC is more stable than Fe-BDC. Further, the optical properties were investigated in the wavelength range 325–1100 nm, and the Fe-BDC exhibited greater optical transmission properties than Cu-BDC by 33 %, as investigated by Wemple-DiDomenico and Tauc models. The dispersion parameters related to optical studies for Cu-BDC were better in comparison to Fe-BDC, which could be attributed to the increase in Cu valence electrons due to an increase in the number of cations. The electrochemical behavior in terms of CV measurements shows the presence of pseudo capacitance in both Fe-BDC and Cu-BDC MOFs. The improved CV performance of Cu-BDC MOF suggests that it could be used as a storage material. This work successfully demonstrates the tailoring of optical properties related to MOF thin films through the formation of stable complexes using BDC as a potential material for the fabrication of OLED's and Solar cells. The improved CV performance suggests that these MOF based materials could be used as anodes in fabrication of batteries or supercapacitors.

Torsional flexibility in zinc-benzenedicarboxylate metal-organic frameworks.

We explore the role and nature of torsional flexibility of carboxylate-benzene links in the structural chemistry of metal-organic frameworks (MOFs) based on Zn and benzenedicarboxlyate (bdc) linkers. A particular motivation is to understand the extent to which such flexibility is important in stabilising the unusual topologically aperiodic phase known as TRUMOF-1. We compare the torsion angle distributions of TRUMOF-1 models with those for crystalline Zn/1,3-bdc MOFs, including a number of new materials whose structures we report here. We find that both periodic and aperiodic Zn/1,3-bdc MOFs sample a similar range of torsion angles, and hence the formation of TRUMOF-1 does not require any additional flexibility beyond that already evident in chemically-related crystalline phases. Comparison with Zn/1,4-bdc MOFs does show, however, that the lower symmetry of the 1,3-bdc linker allows access to a broader range of torsion angles, reflecting a greater flexibility of this linker.

Unlocking the potential of phosphogypsum waste: Unified synthesis of functional metal-organic frameworks and zeolite via a sustainable valorization route

Phosphogypsum (PG) is one of the hazardous wastes generated during phosphate fertilizers production. Valorizing PG into value-added materials is needed to overcome the environmental threat of accumulating PG stockpiles. The primary chemical constituents of PG are CaSO4·2H2O, SiO2, Al2O3, P2O5, and trace metals. Herein, we employed unified strategic synthesis method to transform the main components of PG into two classes of functional porous materials in subsequent steps. The alumina and silica components were isolated to fabricate cancrinite zeolite (CAN) while the residual calcium was directed to grow Ca-based metal–organic frameworks (Ca-MOFs) in the subsequent step. The resulting zeolite with a Si/Al ratio of ∼2.2 showed enhanced CO2 capture property, which, in many respects, is better than those achieved by similar frameworks from other precursors. The unveiled MOF synthesis approach was proven to be adaptable, allowing the preparation of different Ca-MOFs from organic linkers of diverse connectivity, namely Ca-BDC, Ca-BTC, and Ca-TCPB (SBMOF-2), using the linear ditopic benzene dicarboxylate, the tritopic benzene tricarboxylate, and tetracarboxylate-based linkers, respectively. The successful assembly of the porous materials was confirmed using various characterization techniques, including XRD, SEM-EDX, FTIR, and TGA-MS. The porosity of the materials was also probed using N2 at 77 K, CO2 at different temperatures, and H2O at 298 K sorption analyses. The Ca-BTC MOF with the optimal pore aperture size (∼3.4 Å) shows a potential for water/alcohol separation with a steep and fast moisture adsorption profile and negligible alcohol uptake. The synthetic transformation approach presented in this work represents the first example of a valorization route to form extended porous structures from PG waste.

Metal–organic framework-reduced graphene oxide (Zn-BDC@rGO) composite for selective discrimination among ammonia, carbon monoxide, and sulfur dioxide

The structural diversity and high surface reactivity of the metal–organic frameworks (MOFs) offer an ideal material platform for various applications such as gas storage, gas separation, catalyst, etc. However, their use in chemiresistive gas sensing is limited due to the requirement of optimized gas adsorption properties with electrical conductivity. In the present investigation, we have modulated the electrical properties of zinc benzene dicarboxylate (Zn-BDC) MOF by modifying it with partially reduced graphene oxide (rGO). The Zn-BDC and rGO composite (Zn-BDC@rGO) was synthesized by utilizing a solvothermal method and multiparametrically tested by various techniques such as X-Ray diffraction (XRD), UV–visible spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and I–V characteristics, for its structural, spectroscopic, morphological, surface area analysis, thermal stability, and electrical characterization, respectively. The synthesized Zn-BDC@rGO composite was deposited via drop casting method on the copper electrodes on a glass substrate (100 µm gap) using the shadow mask technique by the e-beam evaporator, and tested for the detection of ammonia, carbon monoxide, and sulfur dioxide using chemiresistive modality. The principal component analysis (PCA) indicates that the developed sensor selectively discriminates among the NH3, CO, and SO2 gases with low response/recovery time, i.e., 60/120 s at 20 ppm, which is far below the permissible exposure limit (PEL) suggested by The Occupational Safety and Health Administration (OSHA), USA for CO and NH3 and very close to the PEL level of SO2.

Green valorization of PET waste into functionalized Cu-MOF tailored to catalytic reduction of 4-nitrophenol

Metal-organic frameworks (MOFs) are attractive functional materials due to their high surface area, high porosity, and flexible compositions. However, the high precursor cost and complex synthetic processes hinder their large-scale applications. Herein, a novel green approach has been developed toward the synthesis of Cu-based MOF by a solvent-free mechano-synthesis method and utilizing consumed polyethylene terephthalate (PET)-derived benzenedicarboxylate (BDC) as the linker. The as-prepared CuBDC and aminated CuBDC (CuBDC-NH2) act as green catalysts for the reduction of deleterious 4-nitrophenol (4-NP) into the value-added 4-aminophenol (4-AP). Compared with CuBDC, CuBDC-NH2 shows increased adsorption capability and reduction efficiency. The mechanism and thermodynamic studies suggest that the adsorption of 4-NP on CuBDC-NH2 is an endothermic, spontaneous, favorable, and physical adsorption process. Furthermore, CuBDC-NH2 can expedite the reduction of 4-NP by participating in an adsorptive catalytic process. With the CuBDC-NH2 catalyst, the catalytic normalized kinetic rate of 4-NP was achieved 11.28 mol/min. mg, outperforming state-of-the-art catalysts, and a complete reduction occur in 5 min for a concentrated effluent (200-ppm 4-NP). The plastic waste-derived MOF-mediated catalytic valorization of organic pollutants demonstrated here opens an avenue for the green recycling/utilization of plastic waste, providing meaningful insights into the sustainable management of organic pollutants in wastewater.

Chloride-Less Approach Using Waste Linker Source in Zirconium-based Metal-Organic Framework (UiO-66)

UiO-66 was synthesized using a chloride-less approach with waste plastic bottles as a possible organic linker at room temperature. UiO-66 features an arrangement of structure from the coordination of zirconium-based metal clusters interconnected by benzene dicarboxylate (BDC) linkers. BDC can be extracted from waste plastic bottles by depolymerization. The structural comparison of UiO-66 using a pristine linker and PET-derived BDC linker was investigated with and without the presence of chloride ions. The (011), (111), (002), and (022) reflection planes from X-ray diffraction peaks for all samples show successful UiO-66 crystal formation. Thermal analysis on as-synthesized samples exhibited the decomposition in three stages of weight loss which are attributable to the solvent’s evaporation at ca. [Formula: see text]C, loss of water molecules physisorbed in the structure at ca. [Formula: see text]C, and mass reduction at ca. [Formula: see text]C due to decomposition of organic linkers, respectively. FT-IR spectra exhibited absorption peaks corresponding to the stretching vibration ([Formula: see text]-H) in asymmetric and symmetric C–H bonds in aromatic compounds originating from BDC. By using the Scherrer equation, the primary crystallite size was calculated at a range of ca. 15–32[Formula: see text]nm. The crystallite size calculated showed a similar value to the grain observed using a Williamson–Hall (WH) plot in the range of ca. 14–29[Formula: see text]nm. However, the WH plot for samples without chloride ions showed small crystallite sizes as well as low relative crystallinity suggesting loose agglomerations of the particles.

Influence of Molecular Separation on Through‐Space Intervalence Transient Charge Transfer in Metal–Organic Frameworks with Cofacially arranged Redox Pairs

AbstractWe demonstrate direct evidence of photoinduced through‐space intervalence charge transfer (IVCT) between two cofacially arranged redox‐active pairs in metal–organic frameworks and their dynamic variation with their molecular separation. Two homologous MOFs [Co2(NDC)2(DPTTZ)2]. DPTTZ. DMF, 1 and [Co2(BDC)2(DPTTZ)2]. DMF, 2 (where NDC=naphthalene dicarboxylate, BDC=benzene dicarboxylate, DPTTZ=N, N′‐di(4‐pyridyl)thiazolo‐[5,4‐d]thiazole, DMF=N, N′‐dimethyl formamide) are considered for this, whose intra‐dimer distance of redox‐active DPTTZ ligands differs ca. 1 Å from one system to another. Spectroelectrochemical study detects the formation of IVCT band at the NIR region between cofacially oriented DPTTZ molecules in both MOFs. Transient spectroscopy shows faster charge separation as well as charge recombination when intra‐dimer distance is lesser (in MOF 2) due to stronger electronic coupling. We quantify the extent of IVCT by charge transfer integral calculation; and also by optical pump terahertz probe spectroscopy, where MOF 2 shows three times higher carrier mobility due to lesser inter‐DPTTZ distance than MOF 1. These findings reveal a more localized aspect of through‐space IVCT between cofacially organized redox‐active pair in a three‐dimensional framework.

Influence of Molecular Separation on Through-Space Intervalence Transient Charge Transfer in Metal-Organic Frameworks with Cofacially arranged Redox Pairs.

We demonstrate direct evidence of photoinduced through-space intervalence charge transfer (IVCT) between two cofacially arranged redox-active pairs in metal-organic frameworks and their dynamic variation with their molecular separation. Two homologous MOFs [Co2 (NDC)2 (DPTTZ)2 ]. DPTTZ. DMF, 1 and [Co2 (BDC)2 (DPTTZ)2 ]. DMF, 2 (where NDC=naphthalene dicarboxylate, BDC=benzene dicarboxylate, DPTTZ=N, N'-di(4-pyridyl)thiazolo-[5,4-d]thiazole, DMF=N, N'-dimethyl formamide) are considered for this, whose intra-dimer distance of redox-active DPTTZ ligands differs ca. 1 Å from one system to another. Spectroelectrochemical study detects the formation of IVCT band at the NIR region between cofacially oriented DPTTZ molecules in both MOFs. Transient spectroscopy shows faster charge separation as well as charge recombination when intra-dimer distance is lesser (in MOF 2) due to stronger electronic coupling. We quantify the extent of IVCT by charge transfer integral calculation; and also by optical pump terahertz probe spectroscopy, where MOF 2 shows three times higher carrier mobility due to lesser inter-DPTTZ distance than MOF 1. These findings reveal a more localized aspect of through-space IVCT between cofacially organized redox-active pair in a three-dimensional framework.

Design of Pore Properties of an Al-Based Metal-Organic Framework for the Separation of an Ethane/Ethylene Gas Mixture via Ethane-Selective Adsorption.

A series of Al-based isomorphs (CAU-10H, MIL-160, KMF-1, and CAU-10pydc) were synthesized using isophthalic acid (ipa), 2,5-furandicarboxylic acid (fdc), 2,5-pyrrole dicarboxylic acid (pyrdc), and 3,5-pyridinedicarboxylic acid (pydc), respectively. These isomorphs were systematically investigated to identify the best adsorbent for effectively separating C2H6/C2H4. All CAU-10 isomorphs exhibited preferential adsorption of C2H6 over that of C2H4 in mixture. CAU-10pydc exhibited the best C2H6/C2H4 selectivity (1.68) and the highest C2H6 uptake (3.97 mmol g-1) at 298 K and 1 bar. In the breakthrough experiment using CAU-10pydc, 1/1 (v/v) and 1/15 (v/v) C2H6/C2H4 gas mixtures were successfully separated into high-purity C2H4 (>99.95%), with remarkable productivities of 14.0 LSTP kg-1 and 32.0 LSTP kg-1, respectively, at 298 K. Molecular simulations revealed that the exceptional separation performance of CAU-10pydc originated from the increased porosity and reduced electron density of the pyridine ring of pydc, leading to a relatively larger decrease in π-π interactions with C2H4 than in the C-H···π interactions with C2H6. This study demonstrates that the pore size and geometry of the CAU-10 platform are modulated by the inclusion of heteroatom-containing benzene dicarboxylate or heterocyclic rings of dicarboxylate-based organic linkers, thereby fine-tuning the C2H6/C2H4 separation ability. CAU-10pydc was determined to be an optimum adsorbent for this challenging separation.

The Use of Copper Terephthalate for the Determination and Separation of Organic Dyes via Solid-Phase Extraction with Spectrophotometric Detection

In this work, a metal–organic framework (MOF), copper benzene dicarboxylate (Cu-MOF), was tested for the adsorptive recovery of organic dyes (Sunset Yellow FCF, Tartrazine, Orange II, and Methyl Orange) from aqueous solutions. Studies were also carried out to determine the effects of various parameters, and isothermal and kinetic models were proposed. The adsorption capacity of Cu-MOF was much higher than that of activated carbon. The experimental data are best described by the Langmuir isotherm model (R2 > 0.997) and show the ability of Cu-MOF to adsorb 435 mg/g of the dye under optimal conditions. The study of the kinetics of the dye adsorption process followed a pseudo-second-order kinetic model indicating the coexistence of physical and chemisorption, with diffusion within the particles being the rate-limiting step. Thermodynamic studies were also carried out, and they led to the conclusion that the adsorption of the dye was a feasible, spontaneous, and exothermic process (−25.53 kJ mol−1). The high organic dye recovery shows that Cu-MOF can be used as an efficient and reusable adsorbent for the extraction of dyes from aqueous solutions. These studies may lead to economic interest in this adsorbent material for environmental purposes.

Guest molecular guided syntheses of 2-dimensional uranyl complexes with rigid benzenedicarboxylate ligands

Two new heterometallic uranyl-organic frameworks (UOFs), [Cd(phen)2(H2O)2][(UO2)2(BDC)3]·2H2O (1) and [Ni(phen)3][(UO2)2(BDC)3]·2H2O (2), were obtained under hydrothermal conditions. Both crystal structures were characterized by single-crystal X-ray diffraction analyses and the results indicate that both complexes feature a similar 2D honeycomb framework that is connected by rigid benzenedicarboxylate (BDC) ligands and uranyl units. BDC works as a linker to bridge neighboring UO2 2+ units, where UO2 2+ is tris-chelated. Different guest molecules guided the stacking of 2D layers and lead into their 3D supramolecular crystal structures with different space groups. As a result, 1 crystallized in a polar space group Cc, whereas 2 belongs to a chiral space group P6122. Thermogravimetric measurements were performed to study their thermal stability. UV-visible diffuse reflectance spectroscopy measurements indicate an experimental optical bandgap of 3.87 eV and 3.63 eV, respectively, for 1 and 2. Luminescent studies of both samples show strong green light emissions.

Fabrication of Porous Fe-Based Metal-Organic Complex for the Enhanced Delivery of 5-Fluorouracil in In Vitro Treatment of Cancer Cells.

Metal-organic complexes are one of the most studied materials in the last few decades, which are fabricated from organic ligands and metal ions to form robust frameworks with porous structures. In this work, iron-1,4-benzenedicarboxylic-polyethylene glycol (Fe-BDC-PEG) with a porous structure was successfully constructed by an iron(III) benzene dicarboxylate and polyethylene glycol diacid. The drug-delivery properties of the resultant Fe-BDC-PEG were tested for the loading and release of the 5-fluorouracil compound. The maximal loading capacity of Fe-BDC-PEG for 5-fluorouracil was determined to be 348.22 mg/g. The drug release of 5-fluorouracil-loaded Fe-BDC-PEG after 7 days was 92.69% and reached a maximum of 97.52% after 10 days. The 7 day and acute oral toxicity of Fe-BDC-PEG in mice were studied. The results show that no reasonable change or mortality was observed upon administration of Fe-BDC-PEG complex in mice at 10 g/kg body weight. When the uptake of Fe-BDC-PEG particles in mice was continued for 7 consecutive days, the mortality, feed consumption, body weight, and daily activity were negligibly changed.

Nonredox CO2 Fixation in Solvent-Free Conditions Using a Lewis Acid Metal-Organic Framework Constructed from a Sustainably Sourced Ligand.

CO2 epoxidation to cyclic carbonates under mild, solvent-free conditions is a promising pathway toward sustainable CO2 utilization. Metal-organic frameworks (MOFs) explored for such applications so far are commonly composed of nonrenewable ligands such as benzene dicarboxylate (BDC) or synthetically complex linkers and therefore are not suitable for commercial utilization. Here, we report new yttrium 2,5-furandicarboxylate (FDC)-based MOFs: "UOW-1" and "UOW-2" synthesized via solvothermal assembly, with the former having a unique structural topology. The FDC linker can be derived from biomass and is a green and sustainable alternative to conventionally used BDC ligands, which are sourced exclusively from fossil fuels. UOW-1, owing to unique coordination unsaturation and a high density of Lewis active sites, promotes a high catalytic activity (∼100% conversion; ∼99% selectivity), a high turnover frequency (70 h-1), and favorable first-order kinetics for CO2 epoxidation reactions using an epichlorohydrin model substrate under solvent-free conditions within 6 h and a minimal cocatalyst amount. A systematic catalytic study was carried out by broadening the epoxide substrate scope to determine the influence of electronic and steric factors on CO2 epoxidation. Accordingly, higher conversion efficiencies were observed for substrates with high electrophilicity on the carbon center and minimal steric bulk. The work presents the first demonstration of sustainable FDC-based MOFs used for efficient CO2 utilization.

Propargyl carbamate-functionalized Cu(II)-metal organic framework after reaction with chloroauric acid: An x-ray photoelectron spectroscopy data record

A copper-containing metal organic framework was prepared using the new organic linker 5-(2-{[(prop-2-yn-1-yloxy)carbonyl]-amino}ethoxy)isophthalic acid [1,3-H2YBDC (where Y = alkYne and BDC = Benzene DiCarboxylate)] and functionalized with gold particles by reaction with HAuCl4 under thermal treatment in methanol. The resulting system was investigated by complementary techniques to obtain information on its structure and morphology. In the present work, x-ray photoelectron spectroscopy (XPS) was employed to analyze the chemical composition of a representative specimen. Besides wide scan spectra, data obtained by the analysis of the C 1s, O 1s, N 1s, Cu 2p, and Au 4f signals are presented and critically discussed. The results highlight the reduction of Au(III) to mostly Au(I) species. Overall, the data presented herein may act as useful guidelines for the eventual tailoring of material properties and their possible implementation toward functional applications in heterogeneous catalysis.

Catalytic activity and stability of sulfonic-functionalized UiO-66 and MIL-101 materials in friedel-crafts acylation reaction

Sulfonic-containing UiO-66 and MIL-101 MOF materials, prepared by direct synthesis with a sulfonic acid-including benzene dicarboxylate (SO3H-BDC) linker, have been evaluated as acid catalysts in Friedel–Crafts acylation of anisole with acetic anhydride. The catalytic activity of these materials was compared to other conventional acidic sulfonic heterogeneous catalysts, such as commercial Nafion-SAC-13 and Amberlyst-15. The catalytic performance of MOF materials was significantly dependent on their textural properties and the availability of sulphonic acid groups. MIL-101-SO3H material displayed a remarkable anisole conversion and specific activity per sulfonic acid centre due to its open structure and multimodal pore size distribution. The inherent properties of MIL-101-SO3H material allowed a more sustainable catalyst regeneration than those used for conventional heterogeneous catalysts due to the deposition of reagents and products, in particular poly-acetylated compounds. MIL-101-SO3H proved an easy recovery and reusability in successive runs without any loss of activity. These promising results evidenced the potential of MIL-101-SO3H as an alternative catalyst for acid-catalyzed reactions.

Crystal structure and magnetic properties of the layered hybrid organic–inorganic compounds M 2(OH)2(C14H8O4) (M = Mn, Fe)

The structure of M 2(OH)2(bpdc) (bpdc = biphenyl dicarboxylate, C14H8O4) is distinct from that of the isoreticular compounds M 2(OH)2(bdc) (bdc = benzene dicarboxylate, C8H4O4) (M = Mn, Fe), in the sense that no disorder of the bpdc molecules from one layer to the other needs to be considered. The global symmetry is lower in the bpdc compounds (P 1) than in the bdc compounds (C2/m). Both Mn2(OH)2(bpdc) and Fe2(OH)2(bpdc) order magnetically at 36.8 and 46.5 K, respectively, and can be considered as uncompensated antiferromagnets, whereas Mn2(OH)2(bdc) (Néel temperature T N = 38.5 K) and Fe2(OH)2(bdc) (T N = 66 K) are compensated antiferromagnets.

The effect of cavity size on ruthenium (II) tris-(2,2-bipyridine) photophysics encapsulated within zirconium based metal organic frameworks

Metal organic frameworks (MOFs) are well known for their exceptionally large surface areas and high porosity making them ideal candidates for gas storage and adsorption, drug delivery systems, and light harvesting platforms. A class of MOF’s that have gained much attention for their exceptional hydrothermal stability are the zirconium oxide MOF’s. One in particular is Uio-66 which is composed of Zr6O8 clusters connected by benzene dicarboxylate linkers. One important characteristic of the Uio-66 series of MOFs is that extension of organic linkers results in a systematic increase in cavity size while retaining the same overall framework topology. This property affords the opportunity to examine the effects of cavity size on the photophysics of encapsulated guests. Here a comparison of the photophysics of ruthenium (II) tris-(2,2′-bipyridine) (RuBpy) encapsulated within three Zr-based MOF’s Uio-66, Uio-67, and Uio-68 is presented. All three RuBpy@Uio-xx (xx = 66, 67 or 68) materials display a bathochromic shift in the steady state spectra and an emission lifetimes that fit to a biexponential decay function. Both RuBpy@Uio-66 and RuBpy@Uio-67 exhibit extended emission lifetimes which is characteristic of deactivation of the higher energy triplet ligand field state (3LF) and depopulation from a higher energy metal-to-ligand charge transfer state (3MLCT). Interestingly, RuBpy@Uio-68 exhibits a solution like emission lifetime that would be consistent with the larger cavity providing sufficient volume for access to the 3LF state. However, closer examination of the photophysics reveals that even the larger cavity imposes a significant level of confinement although lesser than that observed for the RuBpy@Uio-66 and RuBpy@Uio-67 systems.

Lab-on-Eyeglasses to Monitor Kidneys and Strengthen Vulnerable Populations in Pandemics: Machine Learning in Predicting Serum Creatinine Using Tear Creatinine.

The serum creatinine level is commonly recognized as a measure of glomerular filtration rate (GFR) and is defined as an indicator of overall renal health. A typical procedure in determining kidney performance is venipuncture to obtain serum creatinine in the blood, which requires a skilled technician to perform on a laboratory basis and multiple clinical steps to acquire a meaningful result. Recently, wearable sensors have undergone immense development, especially for noninvasive health monitoring without a need for a blood sample. This article addresses a fiber-based sensing device selective for tear creatinine, which was fabricated using a copper-containing benzenedicarboxylate (BDC) metal-organic framework (MOF) bound with graphene oxide-Cu(II) and hybridized with Cu2O nanoparticles (NPs). Density functional theory (DFT) was employed to study the binding energies of creatinine toward the ternary hybrid materials that irreversibly occurred at pendant copper ions attached with the BDC segments. Electrochemical impedance spectroscopy (EIS) was utilized to probe the unique charge-transfer resistances of the derived sensing materials. The single-use modified sensor achieved 95.1% selectivity efficiency toward the determination of tear creatinine contents from 1.6 to 2400 μM of 10 repeated measurements in the presence of interfering species of dopamine, urea, and uric acid. The machine learning with the supervised training estimated 83.3% algorithm accuracy to distinguish among low, moderate, and high normal serum creatinine by evaluating tear creatinine. With only one step of collecting tears, this lab-on-eyeglasses with disposable hybrid textile electrodes selective for tear creatinine may be greatly beneficial for point-of-care (POC) kidney monitoring for vulnerable populations remotely, especially during pandemics.