Metal-organic Frameworks Structures Research Articles

Metal-Organic-Frameworks Based Mixed-Matrix Membranes for CO2 Separation: An Applicable-Conceptual Approach.

A promising class of porous crystalline materials, metal-organic frameworks (MOFs), have recently emerged as a potential material in fabricating mixed matrix membranes (MMMs) for gas separation applications. Their unique chemistry and structural versatility offer substantial advantages over conventional fillers. This review gives an in-depth exploration of MOF chemistry, focusing on strategies to manipulate their adsorption behavior to enhance separation properties. We scrutinize the impact of various MOF-based MMM components, including polymer matrix, MOFs fillers and polymer/filler interface, on the overall gas separation performance. This involves a detailed analysis of key parameters associated with MMM preparation. Additionally, we offer a comprehensive overview of the determining factors in MOF-based MMM development for gas separation, including MOF structure, synthesis, and chemistry. Moreover, the most advances in modification strategies of MOF for CO2 separation, such as a wide variety of hybrid MOFs will be outlined, which opens the door to an improved CO2 separation process. Finally, the gas transport mechanisms of MMMs are thoroughly discussed to understand the factors affecting the gas permeation through the polymer matrix, MOFs and interface between them.

Electrochemical stability and superior capacitance of bismuth cobalt metal-organic framework incorporated with vanadium disulfide nanosheet for supercapacitor application

The development of a novel supercapacitor electrode material consisting of bismuth and cobalt-based metal-organic framework (MOF) intercalated on vanadium disulfide (VS2) nanosheets (BiCo-MOF@VS2). The composite combines the high porosity and tunable functionality of MOFs with excellent conductivity and high theoretical capacitance of VS2. The MOF structure is designed to incorporate bismuth and cobalt, which enhance electrochemical performance. The VS2 nanosheets provide a conductive support matrix for the MOF, facilitating electron transport and promoting fast charge-discharge rates. Researchers used a suite of techniques to characterize the fabricated electrodes to understand the relationship between material properties and performance. These techniques analyzed the morphology, crystal structure, and electrochemical properties of the materials. The electrochemical performance of BiCo-MOF@VS2 electrodes for supercapacitor applications is investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The research shows that these composite electrodes are highly promising for use in supercapacitors needing top performance. They deliver impressive capacitance, handle rapid charge and discharge cycles well, and maintain stability over time. We found that the electrochemical behavior is optimum when BiCo-MOF@VS2 is used, which is a result of the synergistic effects of VS2 dispersion and the BiCo-MOF. BiCo-MOF and VS2 have shown specific capacitance values of 282 and 199 F g−1, compared to the two electrode materials, BiCo-MOF@VS2 demonstrated an impressive specific capacitance of 472 F g−1 at 1 A g−1, and cyclic stability with 85 % retention even after 3000 cycles at 9 A g−1 current density tested in 1 M KOH solution. This novel material holds promise for developing next-generation supercapacitors with exceptional energy storage capabilities.

Hydrogen storage in M(BDC)(TED)0.5 metal-organic framework: physical insights and capacities.

Finding renewable energy sources to replace fossil energy has been an essential demand in recent years. Hydrogen gas has been becoming a research hotspot for its clean and free-carbon energy. However, hydrogen storage technology is challenging for mobile and automotive applications. Metal-organic frameworks (MOFs) have emerged as one of the most advanced materials for hydrogen storage due to their exceptionally high surface area, ultra-large and tuneable pore size. Recently, computer simulations allowed the designing of new MOF structures with significant hydrogen storage capacity. However, no studies are available to elucidate the hydrogen storage in M(BDC)(TED)0.5, where M = metal, BDC = 1,4-benzene dicarboxylate, and TED = triethylenediamine. In this report, we used van der Waals-dispersion corrected density functional theory and grand canonical Monte Carlo methods to explore the electronic structure properties, adsorption energies, and gravimetric and volumetric hydrogen loadings in M(BDC)(TED)0.5 (M = Mg, V, Co, Ni, and Cu). Our results showed that the most favourable adsorption site of H2 in M(BDC)(TED)0.5 is the metal cluster-TED intersection region, in which Ni offers the strongest binding strength with the adsorption energy of -16.9 kJ mol-1. Besides, the H2@M(BDC)(TED)0.5 interaction is physisorption, which mainly stems from the contribution of the d orbitals of the metal atoms for M = Ni, V, Cu, and Co and the p orbitals of the O, C, N atoms for M = Mg interacting with the σ* state of the adsorbed hydrogen molecule. Noticeably, the alkaline-earth metal Mg strongly enhanced the specific surface area and pore size of the M(BDC)(TED)0.5 MOF, leading to an enormous increase in hydrogen storage with the highest absolute (excess) gravimetric and volumetric uptakes of 1.05 (0.36) wt% and 7.47 (2.59) g L-1 at 298 K and 7.42 (5.80) wt% and 52.77 (41.26) g L-1 at 77 K, respectively. The results are comparable to the other MOFs found in the literature.

MOF-Based Platform for Kidney Diseases: Advances, Challenges, and Prospects.

Kidney diseases are important diseases that affect human health worldwide. According to the 2020 World Health Organization (WHO) report, kidney diseases have become the top 10 causes of death. Strengthening the prevention, primary diagnosis, and action of kidney-related diseases is of great significance in maintaining human health and improving the quality of life. It is increasingly challenging to address clinical needs with the present technologies for diagnosing and treating renal illness. Fortunately, metal-organic frameworks (MOFs) have shown great promise in the diagnosis and treatment of kidney diseases. This review summarizes the research progress of MOFs in the diagnosis and treatment of renal disease in recent years. Firstly, we introduce the basic structure and properties of MOFs. Secondly, we focus on the utilization of MOFs in the diagnosis and treatment of kidney diseases. In the diagnosis of kidney disease, MOFs are usually designed as biosensors to detect biomarkers related to kidney disease. In the treatment of kidney disease, MOFs can not only be used as an effective adsorbent for uremic toxins during hemodialysis but also as a precise treatment of intelligent drug delivery carriers. They can also be combined with nano-chelation technology to solve the problem of the imbalance of trace elements in kidney disease. Finally, we describe the current challenges and prospects of MOFs in the diagnosis and treatment of kidney diseases.

Strategies for the Preparation of Single-Atom Catalysts Using Low-Dimensional Metal-Organic Frameworks.

As single-atom catalysts are important energy materials, their preparation and synthesis methods have become particularly important. The unique structures of low-dimensional metal-organic frameworks and their derivatives provide various strategies for preparing single-atom catalysts. This paper summarizes various strategies for the preparation of single-atom catalysts based on low-dimensional metal-organic frameworks and their derivatives.

Novel Fe-doped TiO2 metal-organic framework for electrocatalytic hydrogen evolution reaction

A novel approach has been adopted to synthesize titanium oxide-based metal organic framework (MOF), which was doped with iron to increase its efficiency in hydrogen evolution reaction. Scanning electron microscopic images reveal the structure of bare titanium dioxide-based MOF as smooth and aggregated, while doping with iron renders a rough and irregular structure. Mineral phases of ferro-pseudobrookite, anatase, rutile and brookite were prevalent in the doped powder. The presence of iron and titanium in its structure is further confirmed by the deconvoluted spectra from x-ray photoelectron spectroscopy. 0.1 (M) iron doped powder showed an excellent current density of 10 mA/cm2 at an onset potential of 0.345 V, in a three-electrode system. Additionally, its Tafel slope value is 129.6 mV/dec, when compared to the undoped form (168.8 mV/dec), indicating the faster kinetics. Hydrogen evolution reaction is guided by Volmer-Heyrovsky pathway. Electrochemical active surface area of bare MOF powder is 0.62 cm2 while that for 0.1 (M) doped MOF powder is 0.965 cm2. This powder shows extremely good stability and retains its structural integrity even after 1000 linear sweep voltammetry cycles. Density functional theory calculations revealed an increase in the adsorption energy of water molecules attachment in the presence of iron, suggesting an enhanced HER activity.

Synthesis, Characterization, and Fabrication of Nickel Metal-Organic Framework-Incorporated Polymer Electrolyte Membranes for Fuel-Cell Applications.

Proton-conducting sulfonated polymer metal-organic framework (MOF)-based composite membranes were synthesized by anchoring the nickel MOF (Ni-MOF) to the aromatic sulfonated polymer backbone. In this work, we sulfonated two different polymers, poly(1,4-phenylene ether ether sulfone) (PEES) and poly ether ether ketone (PEEK), with a controllable sulfonation degree, and the synthesized Ni-MOF was incorporated into the sulfonated polymers to prepare a polymer electrolyte membrane. The effect of an MOF as a pendant moiety on the polymer backbone had a significant effect on properties such as water uptake, thermal, mechanical, and oxidative stabilities, swelling ratio, ion-exchange capacity (IEC), morphology, proton conductivity, and fuel-cell performance. The presence of an MOF structure enhanced the water retention capacity of the composite membranes. Adding Ni-MOF to the composite membrane improved the fuel-cell performance by increasing the OCV and power density. Among the synthesized electrolytes, the 3 wt % Ni-MOF-incorporated sPEEK membrane displayed a power density of 319 mW/cm2 with a cell voltage of 0.79 V, which was higher than the pure sulfonated polymer. Thus, the developed composite membranes are suitable for fuel-cell applications.

Bells and Whistles on Fertilizers: Molecular Hands to Hang Nanoporous Foliar Fertilizer Reservoirs.

Porous materials are highly explored platforms for fertilizer delivery. Among porous materials, metal-organic frameworks (MOFs) are an important class of coordination polymers in which metal ions and organic electron donors as linkers are assembled to form crystalline structures with stable nanoporosity. Selected amino acids were inherently found to have the capacity to hold the leaf cuticle. Hence, MOF synthesis was attempted in the presence of amino acids, which can act as surface terminators and can assist as hands to hold to the leaf for a controlled nutrient supply. By serendipity, the amino acids were found to act as modulators, resulting in well-stabilized porous MOF structures with iron metal nodes, which are often noted to be unstable. Thus, the composite, i.e., (MOF@aa) MOF modulated with amino acids, has efficient nutrient-feeding ability through the foliar route when compared to the control.

Structure and oxygen evolution reaction performance of Ni-supported catalysts based on steam-exploded poplar

Using renewable steam-exploded poplar (SEP) as carbon source, nickel metal doped carbon hybrid materials were designed to synthesize catalysts (Ni/SEP) with certain oxygen evolution reaction (OER) properties and were compared with nickel catalysts supported on metal organic framework structure (ZIF67-Ni). The roles of SEP support in Ni-based catalyst were considered. Scanning electron microscope (SEM) images confirmed that the fiber could better hinder the aggregation of metal particles. Fourier transform infrared spectroscopy (FT-IR) indicated the presence of surface OH groups after the reduction process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the major form of metallic Ni in the resulting Ni catalysts. Carbon materials as carriers, the synergetic effect of Ni-doped, and carbon carrier played an important role in facilitating the kinetics of OER, which was similar to the carrier of metal-organic frame material. Notably, the Ni/SEP (11.3 mF/cm-2) and ZIF67-Ni (37.2 mF/cm-2) with better OER performance exhibited a smaller double layer capacitances (Cdl), suggesting the intrinsic OER catalytic activity of the Ni/SEP and ZIF67-Ni were much higher in comparison to the ZIF67-Ni/SEP. Moreover, the inferior performance of Ni/SEP further indicated that the synergistic effect between carbon and Ni/NiO contributes to the enhanced OER activity.

Optimizing electrochemical power generation: Harnessing synergies and surface innovation in NiTe-modified MOF nanoarchitectures

Metal-organic frameworks (MOFs) are considered potential electrocatalysts due to their high specific surface area (SSA) and the facilitation of efficient synergistic interactions. In this work, we have implemented a simple and cost-effective surface modification approach to design an efficient electrocatalyst for energy-conversion technologies, specifically water splitting. This work focuses on engineering a novel NiTe functionalized MOF structure wherein NiTe within the MOF channels is the core material, intricately intertwined with highly dispersed Ni particles enveloped by Ni MOF. This fusion of MOFs and NiTe within a designed configuration produces an efficient electrocatalyst with synergistic and surface interface effects and demonstrates bifunctional activity for water splitting. Among the prepared catalysts, one of the resulting catalysts (named Ni MOF/Ni/Ni10Te8) exhibits a low overpotential of 99 mV for the hydrogen evolution reaction (HER) and 180 mV for the oxygen evolution reaction (OER), both benchmarked against RHE @10 mA cm−2. This performance remains steady, with a stability of 99 % after 15 h of continuous operation. Furthermore, the Ni MOF/Ni/Ni10Te8 catalyst also operates in seawater electrocatalysis, requiring a low overpotential of 440 mV at 10 mA cm−2 to produce 70 mL of hydrogen and 34 mL of oxygen. Equally noteworthy are the Faradaic efficiencies achieved, with hydrogen production at 95.7 % and oxygen production at 92.9 %. Developing efficient and economically viable electrocatalysts like the Ni MOF/Ni/NiTe catalyst will advance a cleaner and more sustainable future.

PACMAN: A Robust Partial Atomic Charge Predicter for Nanoporous Materials Based on Crystal Graph Convolution Networks.

We report a fast and easy method (PACMAN) to assign partial atomic charges on metal-organic framework (MOF) and covalent-organic framework (COF) crystal structures based on graph convolution networks (GCNs) trained on >1.8 million high-fidelity partial atomic charge data obtained from the Quantum Metal-Organic Framework (QMOF) database. The developed model shows outstanding performance, achieving a mean absolute error (MAE) of 0.0055 e (test set performance) while maintaining consistency with DDEC6, Bader, and CM5 charges across diverse chemistry and topologies of MOFs and COFs. We find that the new method accurately assigns partial atomic charges for ion-containing nanoporous materials, which has not been possible in previous machine learning (ML) models. Grand canonical Monte Carlo (GCMC) simulation results for CO2 and N2 uptakes and the Widom particle insertion calculation for Henry's law constant of water results based on PACMAN and the original DDEC6 charges show excellent agreements compared to other ML models reported in the literature. The runtime analysis of the new method demonstrates that the partial atomic charges of MOF and COF structures with up to 500 atoms can be obtained in less than 10 s. An easy-to-use web interface has been developed to facilitate the adoption of the developed model.

Rational Designed Metal–Organic Framework with Nanocavity Traps for Selectively Recognizing and Separating of Radioactive Thorium in Rare Earth Wastewater

AbstractFacing the complex coexistence of various metal ions in wastewater and mineral resources, metal–organic frameworks (MOFs) with diverse functionalities and tunable pores are poised to serve as distinctive solutions for efficiently recognizing and selectively separating radioactive thorium (Th(IV)). Herein, a fluorescent MOF (DBT‐DHTA‐Cd) with unique thorium nanocavity traps is rationally designed by using two rigid ligands, including azole and hydroxyl groups, respectively. Notably, the synergistic effect of the appropriate pore size and dense hydroxyl···N nanocavity traps in DBT‐DHTA‐Cd results in selective capture of Th(IV), arising from the high charge density of nano‐trap and extremely low binding energy (Eads = −602.7 KJ mol−1). The fast adsorption kinetics (30 min) and rapid fluorescence response (1 min) of DBT‐DHTA‐Cd toward Th(IV) are attributed to the stronger electron holding capacity of the d and f orbitals belonged to Th(IV), making it more prone to accepting electrons transferred from the N/O active sites in the nano‐trap. As a verification test, tailing breakthrough experiments confirm that DBT‐DHTA‐Cd can efficiently purify Th(IV) from monazite mining solid waste in one step. This work provides profound insights into relationship between structure and property of MOFs and has valuable guidance for designing materials in the radioactive purification field.

Dehydration-Induced Cluster Consolidation in a Metal-Organic Framework for Sieving Hexane Isomers.

Metal-organic frameworks (MOFs) that exhibit dynamic phase-transition behavior under external stimuli could have great potential in adsorptive separations. Here we report on a zinc-based microporous MOF (JNU-80) and its reversible transformation between two crystalline phases: large pore (JNU-80-LP) and narrow pore (JNU-80-NP). Specifically, JNU-80-LP can undergo a dehydration-induced cluster consolidation under heat treatment, resulting in JNU-80-NP with a reduced channel that allows exclusion of di-branched hexane isomers while high adsorption of linear and mono-branched hexane isomers. We further demonstrate the fabrication of MOF-polymer composite (JNU-80-NP-block) and its application in the purification of di-branched isomers from liquid-phase hexane mixtures (98 % di-branched) at room temperature, affording the di-branched hexane isomers with 99.5 % purity and close to 90 % recovery rate over ten cycles. This work illustrates an interesting dehydration-induced cluster consolidation in MOF structure and the ensuing channel shrinkage for sieving di-branched hexane isomers, which may have important implications for the development of MOFs with dynamic behavior and their potential applications in non-thermal driven separation technologies.

Tune and turn the pyrolysis of metal organic frameworks towards stable supported nickel catalysts for the dry reforming of methane

Dry reforming of methane (DRM) is an inimitable approach for eliminating both greenhouse gases, methane and CO2, while producing synthesis gas which further can be converted to added-value fuels. However, the industrialization of DRM has been limited due to sintering and coking to the catalysts under the harsh reaction conditions. Here, we propose a new methodology for producing tunable supported nickel-based catalysts for DRM using metal organic frameworks (MOFs) as precursors of the catalyst components. In particular, Ni- and La-MOFs were coalesced using sonication and then calcined at different temperatures to produce catalysts with tailored Ni metal size (5–20 nm) and tuned strong metal-support interactions (SMSI). Here, the synthesis of nickel and nickel oxide nanoparticles embedded on lanthanum-based supports by controlled calcination of the MOF structures is demonstrated; the Ni supported catalysts were then used for DRM reaction. Among the developed catalysts, the catalyst produced following calcination at 500 °C (Ni-La-500) has shown stable and high CH4 conversion rates under DRM conditions at 800 °C with negligible carbon formation at elevated gas hourly space velocities. Further, the catalytic performance of Ni-La-500 catalyst (sonicated) was compared to the physically mixed MOFs derived catalyst (Ni-La-500-PM), conventional wetness impregnated catalyst (Ni-La-500 WI), Ni-MOF derived unsupported catalyst (Ni-500), and lower Ni concentration catalyst (sonicated, 10Ni-La-500). The observed CH4 conversion rates at 50,000 mL·gcat–1·h−1 GHSV are 81.8, 67.9, 85.4, 34.7, and 57.9 % for Ni-La-500, Ni-La-500 PM, Ni-La-500 WI, Ni-500, and 10Ni-La-500 catalysts, respectively after 24 h of DRM reaction. With isotopic studies, it was found that the 18O exchange rate was higher in case of Ni-La-500-PM catalyst (8.1 mmol·g−1) as compared to Ni-La-500 catalyst (5.5 mmol·g−1). Prior interaction between MOFs, calcination temperatures, reaction conditions, and the carbon pathways during catalytic activity dictates the conversion rates and selectivity of the products. Overall, with the herein proposed approach of MOF-derived supported catalysts exceptional conversion rates and stability during the DRM reaction with nominal coking and sintering were demonstrated, solving the two major challenges faced by conventional and unsupported catalysts.

Controllable integration of nano zero-valent iron into MOFs with different structures for the purification of hexavalent chromium-contaminated water: Combined insights of scavenging performance and potential mechanism investigations

This work combined the stability of the porous structure of metal-organic frameworks with the strong reducibility of nano zero-valent iron, for the controllable integration of NZVI into MOFs to utilize the advantages of each component with enhancing the rapid decontamination and scavenging of Cr(VI) from wastewater. Hence, four kinds of MOFs/NZVI composites namely ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, were prepared for Cr(VI) capture. The results indicated that the stable structure of ZIF67, MOF74, MIL101(Fe), CuBTC, was beneficial for the dispersion of NZVI that could help more close contact between MOFs/NZVI reactive sites and Cr(VI), subsequently, MOFs/NZVI was proved to be better scavengers for Cr(VI) scavenging than NZVI alone. The Cr(VI) capture achieved the maximum adsorption capacity at pH ~ 4.0, which might be due to the participation of more H+ in the reaction and better corrosion of NZVI at lower pH. Mechanism investigation demonstrated synergy of adsorption, reduction and surface precipitation resulted in enhanced Cr(VI) scavenging, and Fe(0), dissolved and surface-bound Fe(II) were the primary reducing species. The findings of this investigation indicated that the as-prepared composites of ZIF67/NZVI, MOF74/NZVI, MIL101(Fe)/NZVI, CuBTC/NZVI, with high oxidation resistance and excellent reactivity, could provide reference for the decontamination and purification of actual Cr(VI)-containing wastewater.

An insight Into Surface and Diffusion Characteristics of UiO‐66@ZIF‐8 Core–Shell MOF for Asymmetric Supercapacitors with Unprecedented Energy Density

AbstractIn this study, nanosized zeolitic imidazolate framework‐8 (ZIF‐8) crystal has been produced on the universitetet i oslo‐66 (UiO‐66) metal–organic framework (MOF) to make core–shell structure using a layer‐by‐layer deposition method. In comparison to the pristine UiO‐66 and ZIF‐8, the core–shell MOF exhibits superior performance in terms of specific capacitance. This enhanced performance is attributed to its remarkable ability to facilitate the rapid diffusion of electrolyte ions through nanosized ZIF‐8 and enhance the electron transfer process involving the inner and outer metal ions within the UiO‐66@ZIF‐8 structure. Remarkably, the core–shell structure achieves an impressive specific capacitance of 588.8 F g−1 at a current density of 0.5 A g−1 using 1 m sulfuric acid (H2SO4) aqueous electrolyte. Additionally, the UiO‐66@ZIF‐8 core–shell material is demonstrated as a positive electrode, coupled with activated carbon (AC) derived from waste tissue paper serving as the negative electrode, in the fabrication of an asymmetric supercapacitor (ASC) device. At a power density of 400 W kg−1, this assembled asymmetric device delivers a notably high energy density of 53 Wh kg−1 along with a cyclic stability of 94.8% after 10 000 cycles. This study substantiates the superior performance of the UiO‐66@ZIF‐8 core–shell MOF structure as a highly effective supercapacitor electrode material, surpassing the performance of its pristine MOF counterparts.

Methotrexate-loaded Fe-metal organic frameworks: Synthesis, characterizations, and drug release investigations

Efficient diagnoses and effective treatment of diseases like cancer can be achieved by designing and developing targeted and controlled drug delivery systems. Metal-organic frameworks (MOFs) are promising drug delivery systems due to large surface area, tunable pore sizes, and controlled drug release. Herein, we report the loading and release of methotrexate (MTX) in MIL-101-Fe MOF as a drug delivery system. The functional groups, crystal structure, and morphology of the as-synthesized MOF was determined by Fourier transform infrared spectroscopy (FTIR), powdered X-ray diffraction and scanning electron microscopy (SEM), respectively. Interestingly, the MOF exhibited 84 % encapsulation efficiency for MTX and 62 % release in the initial 50 h at pH 5.5, which is ideal for tumor tissue. The MTX@MIL-101-Fe effectively killed the HeLa cells from human cervical cancer. Particularly noteworthy was that neither MIL-101-Fe nor MTX@MIL-101-Fe showed toxicity to healthy Vero cells. It proves that the Methotrexate was released from MTX@MIL-101-Fe in cancer cells at pH 5.5 and caused apoptosis. Theoretical studies used density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to explore three possible Methotrexate-MIL-101-Fe encapsulation complexes. The complex with the drug attached at the carboxylate-bridge site showed the highest binding. Moreover, a decrease in the calculated band gap was also observed during the encapsulation process. This study suggests that MIL-101-Fe can be a promising candidate for target-specific and efficient delivery of Methotrexate to cancer cells with reduced side effects.

Mechanistical Insights into the Ultrasensitive Detection of Radioactive and Chemotoxic UO22+ Ions by a Porous Anionic Co-Metal-Organic Framework.

Development of a simple, cost-efficient, and portable UO22+ sensory probe with high selectivity and sensitivity is highly desirable in the context of monitoring radioactive contaminants. Herein, we report a luminescent Co-based metal-organic framework (MOF), {[Me2NH2]0.5[Co(DATRz)0.5(NH2BDC)]·xG}n (1), equipped with abundant amino functionalities for the selective detection of uranyl cations. The ionic structure consists of two types of channels decorated with plentiful Lewis basic amino moieties, which trigger a stronger acid-base interaction with the diffused cationic units and thus can selectively quench the fluorescence intensity in the presence of other interfering ions. Furthermore, the limit of detection for selective UO22+ sensing was achieved to be as low as 0.13 μM (30.94 ppb) with rapid responsiveness and multiple recyclabilities, demonstrating its excellent efficacy. Density functional theory (DFT) calculations further unraveled the preferred binding sites of the UO22+ ions in the tubular channel of the MOF structure. Orbital hybridization between NH2BDC/DATRz and UO22+ together with its significantly large electron-accepting ability is identified as responsible for the luminescence quenching. More importantly, the prepared 1@PVDF {poly(vinylidene difluoride)} mixed-matrix membrane (MMM) displayed good fluorescence activity comparable to 1, which is of great significance for their practical employment as MOF-based luminosensors in real-world sensing application.

Mechanistic study of visible light driven photocatalytic degradation of clofibric acid using Fe-based metal organic frameworks (MOFs)

Although a series of past studies proved the potential usage of Fe-based metal-organic frameworks (MOFs) as photocatalysts, there remains a knowledge gap of the photocatalytic mechanism stemming from the challenge to separate the simultaneous sorption and photocatalytic degradation. Thus, this article aimed to suggest a novel approach by desorbing target molecules during photocatalysis to excavate the underlying mechanisms of sorption and photocatalytic degradation. In this study, two Fe-based MOFs, MIL-101(Fe) and MIL-101(Fe)–NH2, were selected to remove clofibric acid under visible light irradiation. Prior to photocatalysis, sorption mechanism was uncovered based on the sorption kinetic, isotherm, thermodynamic interpretation, and of its dependence on solution pH. The results inferred that the primary sorption mechanism was through the π-π interaction between the benzene ring of clofibric acid and the organic ligand of Fe-based MOFs. Based on these results, photocatalytic mechanism could be independently or jointly assessed during the photocatalytic degradation of clofibric acid. Subsequently, the application of the Tauc method and XPS spectra revealed that the bandgap structure of Fe-based MOFs had the potential to oxidize clofibric acid by producing ROS through the electron excitation upon visible-light illumination. On top of that, the amine functionalization of Fe-based MOF altered the structural moiety that led to an additional strong acid-base interaction with clofibric acid but a decrease in the bandgap limiting the ROS production during photocatalytic activity.

Understanding the adsorption properties of CO2 and N2 by a typical MOF structure: Molecular dynamics and weak interaction visualization

An extensible molecular dynamics (MD) force field for a typical metal–organic framework (MOF) has been developed and verified in comparison with experimental data. The visualization of the important weak interactions based on density functional theory (DFT) calculations is performed. The dynamic process of CO2 and N2 adsorption by MOF was then studied by MD methods. The gas adsorption and desorption during temperature and pressure swing were also investigated. It is found that the structural features of MOF have an important effect on the regional range and strength of the weak interactions, and the region of the van der Waals potential surface of the MOF can determine the gas density distribution. The adsorption is dominated by van der Waals interactions on the whole and the variation of the total weak interaction energy can reflect that of the adsorbed amount. The sorption/desorption responds more slowly to temperature swing than to pressure swing.