As-prepared Metal-organic Frameworks Research Articles

Near infrared light and tumor microenvironment multi-sensitive “Yolk-Shell MOF Nanoreactor” for synergistic treatment of cervical cancer

Developing novel and efficient multimodal nanomaterial-based anticancer agents to meet complex clinical demands is an urgent challenge. Herein, novel graphene quantum dots (GQDs) doped Cu2S@ZIF-8 yolk-shell Metal-Organic Frameworks (MOFs) was firstly constructed by a simple and mild wet-chemical method at room temperature. The MOFs possessed exiting photothermal performance and catalytic activities, which were further enhanced greatly upon near infrared light irradiation or in tumor microenvironment (TME) due to their unique composition and structure. The possible mechanism was discussed. The introduction of GQDs played a key role because it could effectively absorb NIR light and convert partial Cu2S nanodots to CuS nanodots, thus further increase NIR light absorption and generate cascaded electron transport effects, which will enhanced the photothermal performance and catalytic activities of yolk-shell MOFs. After small molecules drugs doxorubicin (DOX) and folic acid (FA) were loaded and conjugated, the as-prepared MOFs could be expected as efficient nanoplatform for cervical cancer synergistic therapy. These prominent intelligent laser and tumor microenvironment (TME)-responsive features of yolk-shell nanocomposite provide an innovative paradigm to explore nanoplatform for tumor therapy.

Decorating Cage-Shaped Cavities with Carboxyl Groups on Two-Dimensional MOF Nanosheet for Trace Uranium(VI) Trapping.

The efficient and complete extraction of uranium from aqueous solutions is crucial for safeguarding human health from potential radiotoxicity and chemotoxicity. Herein, an ultrathin 2D metal-organic framework (MOF) nanosheet with cavity structures was elaborately constructed, based on a calix[4]arene ligand. The large molecular skeleton and cup-shaped feature of the calix[4]arene enabled the as-prepared MOFs with large layer separations, which can be readily delaminated into ultrathin single-layer (∼1.25 nm) nanosheets. The incorporation of permanent cavity structures to the MOF nanosheets can fully utilize their structural features of readily accessible adsorption groups and exposed surface area in uranium removal, reaching ultrafast adsorption kinetics; the functionalized cavity structure endowed MOF nanosheets with the ability to preconcentrate and extract uranium from aqueous solutions with ultrahigh efficiencies, even at extremely low concentrations. As a result, relatively high removal ratios (>95%) can be achieved for uranium within 5 min, even in the ultralow concentration range of 75-250 ppb, and the residual uranium was reduced to below 4.9 ppb. The MOF nanosheets also exhibited extremely high anti-interference ability, which could efficiently remove the low-level uranium (∼150 ppb) from various real samples. The characterizations and density functional theory calculations demonstrated that the synergistic effects of multiple interactions between the carboxylate groups and cage-like cavities with uranyl ions can be responsible for the efficient and selective uranium extraction.

Performance of ionic liquid functionalized metal organic frameworks in the adsorption process of phenol derivatives.

The growth of industrial activities has produced a significant increase in the release of toxic organic pollutants (OPs) to the environment from industrial wastewater. On this premise, this study reports the use of metal organic frameworks (MOFs) impregnated with various ionic liquids (ILs) in the adsorption of phenol derivatives, i.e., 2,6-dimethylphenol and 4,4'-dihydroxybiphenyl. MOFs were prepared starting from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) with divalent (Co, Ni, Cu) and trivalent (Ce) metal salts in mild hydrothermal conditions using water as a green solvent. Imidazolium base ionic liquids, namely 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium chloride, and 1-hexyl-3-methyl-imidazolium chloride, were used to modify MOFs, leading to composite materials (IL@MOF), which show the structural characteristics of MOFs, and complement the advantages of ILs. SEM, EDX images, and TG data indicate that the IL is just attached on the surface of the adsorbent material, with no changes in crystal size or morphology, but with slightly altered thermal stabilities of IL@MOF composites compared to the original ILs and MOFs, pointing to some interionic interaction between IL and MOF. This research consists of equilibrium experiments, studying the effect of the initial concentration of OPs on the adsorption efficiency of the as-prepared MOFs and IL@MOF, in order to determine the influence of the nature of the adsorbent on its developed adsorption capacity and to investigate the performance of both ILs and MOFs. To determine the maximum adsorption capacity, several empirical isotherms were used: Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich. The characteristic parameters for each isotherm and the correlation coefficient (R2) were identified. The IL modification of MOFs increased the adsorption capacity of IL@MOF for the removal of phenol derivatives from aqueous solution. The adsorption capacity function of the MOF structure follows the trend CeHEDP > CoHEDP > NiHEDP > CuHEDP. The best performance was achieved by adsorbent materials based on Ce.

Microwave-assisted production of metal-organic frameworks for water purification: A mini-review

Metal-organic frameworks (MOFs) have been demonstrated to be the “star” functional materials for pollutants elimination from wastewater. The microwave (MW)-assisted method can accomplish higher MOFs yield within shorter time than conventional approaches, which can produce desired MOFs with the larger BET surface area and higher catalytic performance. Herin, the various MW-assisted methods, and the corresponding influences of various factors (including synthesis time, solvent, temperature) on the yields and physicochemical properties of the as-prepared MOFs were summarized and discussed in detail. Moreover, the adsorption, catalytic oxidation and catalytic reduction performances of as-prepared MOFs were highlighted. Finally, the future challenges and opportunities of MOFs prepared via MW-assisted method for water purification are proposed, which might provide useful information for designing and producing the versatile MOFs via MW-assisted methods.

An yttrium-organic framework for effective iodine capture and sensing of Cr6+ ions

For environmental protection, it is essential to effectively capture radioiodine that is produced or released as a result of nuclear fission. In this situation, metal–organic frameworks (MOFs) may be effective materials to help with the challenging environmental problem. The solvothermal reaction of Yttrium metal ions (Y3+) with trimesic acid (H3BTC, benzene-1,3,5-tricarboxylic acid) in H2O and ethanol in a 1:1 ratio builds a novel MOF, C9H5O7Y or [(BTC)Y]n (YS-1). According to single crystal XRD, YS-1 has a 3D framework with rare rnb topology of MOF with SBUs: C6H3, C, H2OY. The as-prepared MOF was carefully characterized, and UV–Vis spectroscopy was used to investigate its iodine adsorption in the vapor and solution phases. This revealed that the MOF had a very high adsorption capacity. YS-1 has a maximum sorption capacity of around 142 mg/g and 114.56 mg/g in the vapor and solution phases, respectively. Iodine binds to MOF in the forms of I2 and I3− species, according to Raman spectra. It is interesting to note that the YS-1 has the highest fluorescence potential and is the most sensitive to Cr6+ ions in a liquid medium. As a result, the current MOF functions as a promising material for greater iodine uptake as well as Cr6+ ions sensing.

Metal organic frameworks with carbon black for the enhanced electrochemical detection of 2,4,6-trinitrotoluene

The sensing of explosives such as 2,4,6-trinitrotoluene (TNT) directly at an explosion site requires a fast, simple and sensitive detection method, to which electrochemical techniques are well suited. Herein, we report an electrochemical sensor material for TNT based on an ammonium hydroxide (NH4OH) sensitized zinc-1,4–benzenedicarboxylate Zn(BDC) metal organic framework (MOF) mixed with carbon black on a glassy carbon electrode. In the solvent modulation mechanism, by merely changing the concentration of NH4OH during synthesis, two Zn(BDC) MOFs with novel morphologies were fabricated via a hydrothermal approach. The as-prepared MOFs were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution field emission electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). The different morphologies of the MOFs, and their impact on the performance of the modified electrodes towards the electrochemical detection of TNT was investigated. Under optimum conditions, 0.7–Zn(BDC) demonstrated the best electrochemical response for TNT detection using square wave voltammetry (SWV) with a linear calibration response in the range of 0.3–1.0 μM, a limit of detection (LOD) of 0.042 μM, a limit of quantification (LOQ) of 0.14 μM and a high rate of repeatability. Atomic-scale simulations based on density functional theory authenticated the efficient sensing properties of Zn(BDC) MOF towards TNT. Furthermore, the promising response of the sensors in real sample matrices (tap water and wastewater) was demonstrated, opening new avenues towards the real-time detection of TNT in real environmental samples.

Design, transport efficiency and structure-activity relationship of sulfonated poly (aryl ether ketone) proton exchange membrane based on multi-functional MOFs

In this paper, two kinds of metal-organic frameworks (MOFs) with proton conduction capability were successfully prepared and added into sulfonated poly (ether ketone sulfone) (C-SPAEKS) by organic-inorganic blending. Then two different series of proton exchange membranes (PEMs) were fabricated. The template used in MOFs was UiO-66-NH2 (UN), by introducing sulfonic acid groups and imidazole groups on the template, additional proton sources and proton transport sites were constructed. Such multifunctional MOFs contributed greatly to the proton transport efficiency and structure-activity relationship of C-SPAEKS. The sulfonic acid functionalized MOFs (USN), sulfonic-acid-imidazole bifunctional MOFs (IUSN) and composite PEMs were characterized by XRD, XPS, FT-IR, 1H NMR and SEM. The prepared PEMs all have excellent proton conductivity, in which the proton conductivity of C-SPAEKS/IUSN-3% could reach 0.234 S cm−1 (80 °C and 100% relative humidity). Nafion117 had a conductivity of 0.105 S cm−1 (80 °C and 100% relative humidity), so C-SPAEKS/IUSN-3% exhibited a great enhancement on proton conductivity. Moreover, the oxidation stability of C-SPAEKS/IUSN-3% membrane was 96.97%, which was 39.32% higher than that of C-SPAEKS. These results all indicated that the as-prepared MOFs have made great contribution to improving the comprehensive properties of the sulfonated poly (aryl ether ketone) proton exchange membrane.

Fabrication of granular MOF@γ-Al2O3 composites as promising dual-function adsorbents for the efficient capture of iodine and dyes

As reported herein, we have designed an effective way to achieve in-situ loading of metal-organic frameworks (MOFs) into the pores of activated γ-Al2O3 particles to prepare low-cost, easy-to-obtain and high-yield granular MOFs composites (GMCs). MOF-5, ZIF-8, Ni-BTC, and Co-BTC have been selected to prepare GMCs via in-situ synthesis methods, thereby leading to the GMCs MOF-5-X@γ-Al2O3, ZIF-8-X@γ-Al2O3, Ni-BTC-X@γ-Al2O3, and Co-BTC-X@γ-Al2O3 (X = NO3 or OAc), respectively. The physical and chemical properties of the as-prepared MOF@γ-Al2O3 GMCs were characterized in detail. The results show that MOF-5-X@γ-Al2O3 and ZIF-8-X@γ-Al2O3 exhibit selective adsorption behavior for anionic dye. The adsorption capacities of MOF-5-X@γ-Al2O3 are 1388.01 mg g−1 (for CR and X = NO3), 1431.25 mg g−1 (for CR and X = OAc), 406.50 mg g−1 (for MO and X = NO3), and 234.16 mg g−1 (for MO and X = OAc), respectively, while the adsorption capacities of ZIF-8-X@γ-Al2O3 are 1426.85 mg g−1 (for CR and X = NO3), 1543.91 mg g−1 (for CR and X = OAc), 477.03 mg g−1 (for MO and X = NO3), and 451.02 mg g−1 (for MO and X = OAc), respectively. Moreover, ZIF-8-X@γ-Al2O3 has high adsorption performance for iodine molecules in solution, and the adsorption capacity reaches 630.63 mg g−1 for ZIF-8-NO3@γ-Al2O3 and 583.92 mg g−1 for ZIF-8-OAc@γ-Al2O3, respectively. This method is universal and can be used as an effective approach to prepare GMCs. In addition, the materials prepared by this method can be widely used in the adsorption of small molecules.

Deployment of Superhydrophilic and Super-antifouling Cr-soc-MOF-1-Based Membrane for Ultrafast Separation of Stabilized Oil-in-Water Emulsions.

In spite of massive progress in oil-water separation, attributable to the use of advanced materials, the separation process faces challenges such as low permeance and fouling problems. Therefore, superwettable materials used in several fields are considered potential candidates for oily wastewater treatment. Metal-organic frameworks (MOFs) are receiving more and more interest in various separation applications due to their wide potential applications. Nevertheless, MOFs have been rarely explored for separating stabilized oil-in-water emulsions due to the difficulty in finding highly hydrolytic stable MOF candidates for this application. Furthermore, oil can clog water-stable materials owing to its high density, causing the degradation of MOF particles. As a result, there is a need to develop better MOF materials that can fulfill these requirements. Herein, we have explored Cr-soc-MOF-1 as a candidate for this application and deployed it as a membrane, which exhibited superhydrophilicity and underwater superoleophobicity for separating stabilized oil-in-water emulsions. The Cr-soc-MOF-1 membranes were synthesized by assembling the as-prepared MOF particles on a mixed cellulose ester substrate using a vacuum-assisted self-assembly technique. The Cr-soc-MOF-1 membrane exhibited ultrahigh water permeance (7465.9 L·m-2·h-1·bar-1), very high oil rejection (99.9%), and excellent anti-oil-fouling properties. The Cr-soc-MOF-1 membranes also exhibited excellent recyclability over 10 continuous separation cycles. Further, they exhibited an outstanding performance in separating various surfactant-stabilized oil-in-water emulsions. Thus, the Cr-soc-MOF-1 membranes exhibit a high potential in treating oily wastewater.

Construction of dual-hydrophilic metal-organic framework with hierarchical porous structure for efficient glycopeptide enrichment

As an important role in life activities, it is necessary and important to study protein glycosylation. The pre-enrichment of N-glycopeptides is a significant step in glycoproteomics research. According to the inherent size, hydrophilicity and other properties of N-glycopeptides, affinity materials designed to match them will be able to separate N-glycopeptides from complex samples. In this work, we designed and prepared dual-hydrophilic hierarchical porous metal-organic frameworks (MOFs) nanospheres by metal-organic assembly (MOA) based template method and post-synthesis modification strategy. The hierarchical porous structure significantly improved the diffusion rate and binding sites for N-glycopeptide enrichment. Furthermore, the combination of hydrophilic MOFs and small molecules endowed the as-prepared MOFs nanospheres excellent hydrophilicity, which is conducive to the enrichment of N-glycopeptides based on hydrophilic interaction liquid chromatography (HILIC). Therefore, the nanospheres showed surprising enrichment ability for N-glycopeptides such as excellent selectivity (1/500, human serum immunoglobulin G/bovine serum albumin, m/m) and extremely low detective limitation (0.5 fmol). Meanwhile, 550 N-glycopeptides were identified from rat liver samples, proving its application potential in glycoproteomics research and providing design idea for porous affinity materials.

Synthesis of 2D Metal-Organic Nanosheets (MONs) by Liquid Phase Exfoliation: Applications in Effective Delivery of Antiulcer Drugs and Selective Adsorption and Removal of Cationic Dyes.

Nowadays, the fabrication of 2D metal-organic nanosheets (2D MONs) has entered the research arena fascinating researchers worldwide. However, a lack of efficient and facile methods has remained a bottleneck for the manufacturing of these 2D MONs. Herein, a 2D metal-organic framework (MOF), i.e., 2D Cu-MOF, was synthesized using a facile and convenient stirring method by using 4,4'-trimethylenedipyridine (TMDP) as an organic linker. The as-prepared MOF was characterized in detail and based on single crystal X-ray diffraction analysis, it was established that tangled layers in the 2D Cu-MOF are interconnected to produce thick strands. These tangled layers could be easily separated via ultrasonication-induced liquid phase exfoliation (UILPE) to give the 2D Cu-MON as illustrated through Tyndall light scattering and exhaustive microscopic exploration such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The application of this 2D Cu-MON was assessed in the field of drug delivery revealing exceptional drug loading for the drug lansoprazole (LPZ) by 2D Cu-MONs as well as drug release in the acidic and neutral medium demonstrating that the 2D Cu-MON is an excellent carrier for antiulcer drug delivery. For environmental protection, the application of 2D Cu-MON was also examined toward the removal of various cationic and anionic dyes with excellent selectivity toward cationic dye removal. The plausible mechanism for dye removal indicated the involvement of cation-π and π-π interactions, for the effective adsorption of cationic dyes as well as a increase in the surface area of 2D Cu-MON by UILPE. Remarkably, the high drug loading and dye removal are imputed to the increase in surface area by UILPE. In a nutshell, the developed 2D Cu-MON will prove to be beneficial for application in the field of drug delivery as well as for wastewater treatment.

Efficient photocatalytic degradation of petroleum oil spills in seawater using a metal-organic framework (MOF)

Photocatalysis is a green approach that has appeared to be a viable option for the degradation of a variety of organic contaminants. This work outlines the process of preparing the titanium-based metal-organic framework (MIL-125) photocatalysts using a simple solvothermal method. Structural, morphological, and optical analysis of samples (MT18 and MT48) was carried out by XRD, FT-IR, Raman, SEM, TGA, BET, and UV–Vis. Results indicated that the sample prepared at 150 °C and reaction time of 48 h (MT48) has a low crystal size of 7 nm with an optical band gap of 3.2 eV and a surface area of 301 m2 g−1. Under UV–visible light irradiation, the as-prepared MOFs proved to upgrade photocatalytic activity in degrading crude oil spills in saltwater. Effects of catalyst dosage and exposure time on the degradation of an oil spill in seawater were studied and analyzed using UV–Vis spectrophotometry and gas chromatography (GC–MS) which emphasized that the use of 250 ppm of MT48 photocatalyst under UV–Vis irradiation can degrade about 99% of oil spills in water after 2 h of exposure. The study's data revealed that MIL-125 could be used to photocatalyzed the cleanup of crude oil spills.

Mechanochemistry Milling of Waste Poly(Ethylene Terephthalate) into Metal-Organic Frameworks.

Converting poly(ethylene terephthalate) (PET) into metal-organic frameworks (MOFs) has emerged as a promising innovation for upcycling of waste plastics. However, previous solvothermal methods suffer from toxic solvent consumption, long reaction time, high pressure, and high temperature. Herein, a mechanochemical milling strategy was reported to transform waste PET into a series of MOFs with high yields. This strategy had the merits of solvent-free conditions, ambient reaction temperature, short running time, and easy scale-up for large-scale production of MOFs. The as-prepared MOFs exhibited definite crystal structure and porous morphology composed of agglomerated nanoparticles. It was proven that, under mechanochemical milling, PET was firstly decomposed into 1,4-benzenedicarboxylate, which acted as linkers to coordinate with metal ions for forming fragments, followed by the gradual arrangement of fragments into MOFs. This work not only promotes high value-added conversion of waste polyesters but also offers a new opportunity to produce MOFs in a green and scalable manner.

Using 2D-Phthalocyanine Metal Organic Framework-Based Catalysts for Oxygen Reduction Reaction in Alkaline Media

Developing high performance electrocatalysts to improve the sluggish kinetics of oxygen reduction reaction (ORR) at the cathode is essential in expanding fuel cell applications. Metal organic frameworks (MOFs), given their high surface area, tunable pore size, and diverse metal choices, are promising candidates to catalyze such a reaction. Herein, we report a family of nine 2D-phthalocyanine MOF-based catalysts for alkaline ORR, where M = Co, Ni, Cu. Structurally, these bimetallic materials have two distinct metal sites, where M1 is a phthalocyanine moiety and M2 is a node, existing as M-N4 moiety. X-ray Diffraction (XRD) shows that all as-prepared MOFs have similar structures and inter-layer spacing. X-ray Photoelectron Spectroscopy (XPS) shows slight shifts in binding energy when the same element is placed in a M1 or M2 site, which indicates that the M1 and M2 sites are chemically distinct.Through cyclic voltammetry we evaluate the role of the metal sites for ORR activity and selectivity in 0.1 M KOH. All materials are active for alkaline ORR, while Ni (M1) – Co (M2) has the best overall kinetic activity performance of - 5 mA cm-2 at 0.7 V vs. RHE. Cu – Cu, on the other hand, is the least active combination under the same testing conditions. Within composition series where M2 = Co, the activity trend for M1 is Ni > Cu ~ Co. From a 2-electron selectivity perspective, M1 = Ni > Cu > Co. From these general trends we hypothesize that Co M2 and Ni M1 sites are essential in promoting 4- and 2-electron selectively, respectively. On average we find a nominal ORR performance trend where M2 = Co > Cu > Ni. Interestingly, we note that the M1 identity also plays a non-linear role in activity and selectivity modulation. Though we identify one of the metal sites (M1 or M2) as the dominating site for activity and/or selectivity, the other site also contributes to the total performance. The density functional theory (DFT) calculation supports our experimental results and finds out that Ni as M1 is highly selective for H2O2 formation whereas Co as M2 shows excellent activity for ORR. Our predicted volcano plot shows that MOF with Ni – Co and Cu – Co combinations at Co active site offering lowest ORR overpotential among all other combinations, which is also in good agreement with experimental findings.By evaluating different metal sites performance through electrochemical testing, we can better understand the active species in the MOF catalytic system. By pairing theory with experiment, we gain active site insight to design new specific enhanced active motifs. We believe that these performance trends can assist in better designing efficient MOF-based ORR catalysts that can lead to advances in clean energy technology for sustainable development.

A Hexagonal Nut-Like Metal-Organic Framework and Its Conformal Transformation.

Hollow structured metal-organic frameworks (MOFs) and their derivatives are desired in catalysis, energy storage, etc. However, fabrication of novel hollow MOFs and revelation of their formation mechanisms remain challenging. Herein, open hollow 2D MOFs in the form of hexagonal nut are prepared through self-template method, which can be readily scaled up at gram scale in a one-pot preparation. The evolution from the initial superstructure to the final stable MOFs is tracked by wide-angle X-ray scattering, transforming from solid hexagon to open hollow hexagon. More importantly, this protocol can be extended to synthesizing a series of open hollow structured MOFs with sizes ranging from ≈120 to ≈1200nm. Further, open hollow structured cobalt/N-doped porous carbon composites are realized through conformal transformation of the as-prepared MOFs, which demonstrates promising applications in sustainable energy conversion technologies. This study sheds light on the kinetically controlled synthesis of novel 2D MOFs for their extended utilizations.

High-performance Hf/Ti-doped defective Zr-MOFs for cefoperazone adsorption: Behavior and mechanisms

Due to the excessive use, cephalosporin antibiotics have been detected in various aquatic environments, which may result in environmental and health concern. In this study, bimetallic metal–organic frameworks (MOFs), Hf-UiO-66 and Ti-UiO-66, were successfully designed and obtained via post-synthetic method from UiO-66 for the adsorption of cefoperazone. A serious of adsorption experiments were investigated. The adsorption kinetics and isotherms demonstrated that the adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. Hf/Ti-UiO-66 exhibited much better adsorption performance than the undoped UiO-66. Particularly, Hf-UiO-66 had the highest adsorption capacity (346.0 mg g−1). With the introduction of Hf or Ti, the chemical coordination environment changed, which resulted in defective structures of MOFs. Such defective structures increased the adsorption active sites, changed the surface charges and enlarged pores. Based on the characterization by FT-IR, XPS, and zeta potential, it was identified that the electrostatic attraction, π-π stacking, hydrogen bonding and metal complexation were the driving force for the high adsorption capacity of the bimetallic MOFs. The as-prepared MOFs displayed good stability and reusability. This work provides a great prospect for the design and application of bimetallic defective MOFs in cephalosporins removal in environmental water.

Functional metal–organic framework as high-performance adsorbent for selective enrichment of pharmaceutical contaminants in aqueous samples

Facile and sensitive analysis methods for pharmaceutical contaminants in aqueous environment are of vital importance for water safety, especially when large amounts of anti-viral drugs are being used, discharged and accumulated. In this work, we used functional metal–organic framework (MOF) as high-performance adsorbent for selective enrichment of such pharmaceutical contaminants in aqueous samples. The MOF was synthesized via a new synthesis method previously developed by our group and immobilized on paper membrane to be used in solid-phase extraction (SPE) device. Different metal ions were anchored by MOF to screen out the adsorbent with the best affinity. The targets were a potential anti-COVID-19 drug favipiravir, and its structural and functional analogues (ingredients or intermediates, other anti-viral drugs). To deeply understand the adsorption mechanisms, quantum calculation and computational fluid dynamics (CFD) simulation were both applied. The experimental and in-silico results together demonstrated that the as-prepared MOF adsorbent possessed high affinity and fast dynamics. The established SPE-based liquid chromatography (LC) method worked well in the range of 10–1000 ng/mL, with only 3 mg of adsorbent per device and 5 mL sample needed, and no mass spectrometer (MS) included, which was very efficient compared to commercial adsorbents. The results met the current detection needs in the application scenario, and inspirable for later design of well-behaved adsorbents.

Two-stage ligand exchange in Mn(III)-based porphyrinic metal−organic frameworks for fluorescence water sensing

Metal−organic frameworks (MOFs) have emerged as promising materials for smart sensing and imaging applications. Here, a novel micron-biscuit Mn(III)-based porphyrinic MOF is synthesized with the modulation of 4,4′-biphenyldicarboxylic acid (BPDC). The anisotropic growth of MOF is induced by the increased steric hindrance, yielding micron-biscuit Mn-TCPP(BPDC) MOF crystals. Mn(III), as a sealer, quenched the intrinsic fluorescence of porphyrin because of the ligand-to-metal charge transfer (LMCT) effect, and this disappeared fluorescence can be regularly restored and enhanced due to LMCT effect inhibition and release of free porphyrin derived from the water-induced two-stage ligand exchange (TSLE) between BPDC, porphyrin and water. The as-prepared MOF acts as an excellent “signal-on” luminescent water-sensing probe with low amount (2.5 μg/mL) that can efficiently realize the trace detection of water in various organic media with high sensitivity, especially in dimethyl sulfoxide (DMSO), the detection limit is as low as 0.04% (v/v). Moreover, Mn-TCPP(BPDC) was successfully used for sensing water content in real commercial samples. This MOF with the guest-induced TSLE not only provides inspiration for the design of new luminescent materials, but also widens the path for smart sensing.

On the use of metal-organic framework-based adsorbent from recycled PET bottles for Eriochrome Black T removal

In this study, a metal–organic framework (MOF) adsorbent from recycled polyethylene terephthalate (PET) bottles was developed to effectively remove Eriochrome Black T (EBT) dye present in synthetic wastewater. A sustainable, “greener” route of MOF synthesis was adopted involving microwave-enabled depolymerization of PET to terephthalic acid (TPA) and conversion of the latter to its organic salt linker form. Results from differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) not only revealed the structure of the as-prepared MOF, but also proved the presence of EBT molecules on the adsorbent during the dye removal process. A ∼77% maximum removal was reached after 90 min and the adsorption was best explained by Langmuir model having 82.5 mg/g maximum monolayer capacity. Kinetic studies also showed the adsorption to be pseudo-second order with a two-stage intraparticle diffusion process. The effective performance of MOF on EBT removal was also verified by the presence of potential adsorbent-adsorbate interactions such as ionic, hydrogen bonding, and π–π stacking. Thus, the as-fabricated PET-derived MOF is considered a decent, value–added material acting as a sustainable adsorbent for organic dyes present in contaminated water.

Radioactive iodine capture by metal organic frameworks in liquid and vapour phases: An experimental, kinetic and mechanistic study

For environmental protection, the effectual capture of radioiodine produced or released as nuclear fission products, is of utmost importance. In this aspect, metal-organic frameworks (MOFs) may be a kind of promising material to address this hazardous environmental issue. Herein, four different MOFs, [Co1.5(PhCOO)3(bpy)0.5]n (KQ-1), [Co(HCOO)2(bpy)]n (KQ-2), [Co(HCOO)2]n (KQ-3) and [Mn(HCOO)2]n (KQ-4) have been synthesized via solvothermal method by using benzoic acid (PhCOOH) or formic acid (HCOOH) as organic linker, 4,4′-bipyridine (bpy) as spacer and salts of Co(II) and Mn(II). The as-prepared MOFs were characterized in detail and their iodine (I2) adsorption/release performance was also investigated in vapor and solution phase by UV-Vis spectroscopy with the adsorption capacity being KQ-1 >KQ-2 >KQ-3 ≈ KQ-4. The highest sorption capacity of about 551 and 131.05 mg/g was observed for KQ-1 in vapor and solution phase, respectively, and with recyclability upto five cycles. Raman and XPS spectra indicate that iodine binds to MOF as I2 and I3- species. The plenty of aromatic rings form iodine-π charge transfer complex thus stabilizing the interaction to effect the iodine sorption (as evidenced in KQ-1). Henceforth, the iodine sorption is observed to depend on the presence of aromatic rings in the structure of MOFs.