Nanozyme-induced deep learning-assisted smartphone integrated colorimetric and fluorometric dual-mode for detection of tetracycline analogs

In this work, a colorimetric and fluorescent dual-mode probe controlled by NH2-MIL-88 B (Fe, Ni) nanozymes was developed to visually detect tetracycline antibiotics (TCs) residues quantitatively, as well as accurately distinguish the four most widely used tetracycline analogs (tetracycline (TC), chrycline (CTC), oxytetracycline (OTC), and doxycycline (DC)). Colorless substrate 3,3',5,5'-tetramethylbenzidine (TMB) may be oxidized to blue oxidized TMB by the Fe Fenton reaction, which was catalyzed by the NH2-MIL-88 B (Fe, Ni) nanozyme with POD-like activity. The colorimetric detection system allows TCs to interact with NH2-MIL-88 B (Fe, Ni). This inhibits the production of ·OH, weakens the oxidation process of TMB, and ultimately lightens the blue color in the system by blocking the electron transfer between NH2-MIL-88 B (Fe, Ni) and H2O2. Furthermore, TCs can interact with NH2-MIL-88 B (Fe, Ni) as a result of the internal filtering effect, which causes the fluorescence intensity to decrease as TCs concentration increases. Additionally, a portable instrument that combines a smartphone sensing platform with colorimetric and fluorescent signals was created for the quick, visual quantitative detection of TCs. The colorimetric and fluorescent dual-mode nano platform enables color change, with detection limits (LODs) of 0.182 μM and 0.0668 μM for the spectrometer and smartphone sensor, respectively, based on the inhibition of fluorescence and enzyme-like activities by TCs. Overall, the colorimetric and fluorescence dual-mode sensor has good stability, high specificity, and an efficient way to eliminate false-positive issues associated with a single detection mode.

A colorimetric and SERS dual-mode aptasensor for the detection of Shiga toxin type II based on Mn/Fe-MIL(53)@AuNSs

Shiga toxin type II (Stx2), the major virulence component of enterohemorrhagic Escherichia coli, is strongly associated with the life-threatening hemolytic uremic syndrome thus posing a substantial risk to food safety and human health. In this work, a dual-mode aptasensor with colorimetric and surface-enhanced Raman scattering was developed for Stx2 specific detection based on noble metal nanoparticles and Raman reporter loaded metal-organic framework (Mn/Fe-MIL(53)@AuNSs-MBA). The Mn/Fe-MIL(53)@AuNSs could catalyze the H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), thereby enabling visual detection. Meanwhile, the SERS signal from MBA can be enhanced by the decorated AuNSs. Under optimal conditions, a linear range of 0.05-500 ng/mL with limit of detection (LOD) of 26 pg/mL was achieved in colorimetric mode and a linear range of 5-1000 ng/mL with LOD of 0.82 ng/mL in SERS mode, in which the dual-mode results complement each other, widening the linear range, increasing the accuracy and reliability of the detection. The method was further applied to the detection of Stx2 in milk with average recovery of 101.1 %, demonstrating its superior potential for bacterial toxin monitoring.

Ultrarapid and Sustainable Synthesis of Trimetallic-Based MOF (CrNiFe-MOF) from Stainless Steel and Disodium Terephthalate-Derived PET Wastes

Designing easy and sustainable strategies for the synthesis of metal-organic frameworks (MOFs) from organic and inorganic wastes with the efficient removal of phosphate from water remains a challenge. The majority of the reported works have utilized costly precursors and nonsoluble ligands for the synthesis of MOFs. Herein, we have developed a low-cost, simple, and sustainable alternative approach using the coprecipitation method in water at room temperature for the synthesis of a new adsorbent-based trimetallic MOF. Poly(ethylene terephthalate) and stainless steel wastes were used as sources of water-soluble disodium terephthalate ligand and three metallic species (chromium, nickel, and iron salts) for the fabrication of trimetallic MOF (CrNiFe-MOF), respectively. The newly developed MOF demonstrates a superior space-time yield of 5760 g m-3 day-1, reaching a level allowing the industrialization production of this sustainable MOF. The scanning electron microscopy and adsorption studies revealed that the developed trimetallic MOF consists of aggregated nanoparticles and the presence of defective as well as mesoporous structures. This MOF showed an enhanced adsorption capacity of phosphate from real eutrophic water samples and higher stability in a range of pHs. The density functional theory calculations evidenced that the phosphate ions preferentially adsorb over H2O toward the metal oxo-trimers, with the adsorption energies increasing from H3PO4 to PO43- species in line with an improvement of the adsorption performance of CrNiFe-MOF when the pH increases, i.e., when HPO42- and PO43- become more predominant. These calculations also supported that the incorporation of Cr metal sites in the oxo-trimer is expected to boost the phosphate affinity of the MOF. Finally, our work provides an easy and eco-friendly approach for MOF designing to enhance phosphate removal from water.

Direct Synthesis of Mixed-Metal Paddle-Wheel Metal-Organic Frameworks with Controlled Metal Ratios under Ambient Conditions

Currently, synthesizing mixed-metal metal-organic frameworks (MM-MOFs) in a single step remains a challenge due to the varying reactivities of different metal cations. This often results in the formation of mixtures of monometallic MOFs or MM-MOFs with nonstoichiometric metal ratios. A promising approach to overcoming this issue is the controlled precursor method, which uses prebuilt polynuclear complexes with structures similar to the secondary building units (SBUs) of the desired MOFs. In this study, we report that metal acetates can serve as natural prebuilt SBUs, enabling the controlled synthesis of MBDs ([M2(BDC)2DABCO]n, M = metal, BDC = 1,4-benzenedicarboxylic acid, DABCO = 1,4-diazabicyclo[2,2,2]octane) under ambient conditions. By exploiting the fact that metal acetates readily form soluble paddle-wheel dimers similar to the SBUs of MBDs, we achieve the direct synthesis of mixed-metal MBDs at room temperature. The metal ratios (Zn, Co, and Ni) in the resulting MBDs are controllable, and the production yields exceed 90%. The use of metal acetates facilitates the fast and uniform nucleation of MBDs, regardless of the metal cations involved. This similarity in nucleation rates leads to the formation of bimetallic and trimetallic MBDs with predefined metal ratios and homogeneous metal distribution while maintaining the quality of the MOFs. Importantly, this strategy offers an efficient pathway for synthesizing mixed metal MBDs using stoichiometric amounts of metal salts without toxic additives, high energy consumption, and complex synthesis steps.

Metal-ion doping in metal-organic-frameworks: modulating the electronic structure and local coordination for enhanced oxygen evolution reaction activity

The doping of metal-organic frameworks (MOFs) with metal-ions has emerged as a powerful strategy for enhancing their catalytic performance. Doping allows for the tailoring of the electronic structure and local coordination environment of MOFs, thus imparting on them unique properties and enhanced functionalities. This frontier article discusses the impact of metal-ion doping on the electronic structure and local coordination of MOFs, highlighting the effects on their electrocatalytic properties in relation to the oxygen evolution reaction (OER). The fundamental mechanisms underlying these modifications are explored, while recent advances, challenges, and prospects in the field are discussed. In addition, experimental techniques that can be applied to tackle the realization of effective metal-ion doping of MOFs are also noted briefly.

Moisture-enhanced trace chloroalkanes detection in bimetallic metal-organic frameworks 3-dimensional photonic crystal

Chloroalkanes have long been a threat to environmental protection and human health, however, rapid and efficient detection of chloroalkanes remains challenging. Herein, 3-dimensional photonics crystals (3-D PCs) based on bimetallic materials of institute lavoisier frameworks-127 (MIL-127, Fe₂M, M = Fe, Ni, Co, Zn) demonstrate the great potential of chloroalkanes sensing. Particularly, at temperature of 25 °C and dry conditions, the 3-D PC consisting of MIL-127 (Fe₂Co) shows optimal selectivity and high concentration sensitivity of 0.0351 ± 0.00007 nm ppm^-1 to carbon tetra-chloride (CCl₄), and the limit of detection (LOD) can reach 2.85 ± 0.01 ppm. Meanwhile, MIL-127 (Fe₂Co) 3-D PC sensor presents a rapid response of 1 s and recovery time of 4.5 s for CCl₄ vapor, and can maintain excellent sensing performance under heat-treatment of 200 °C or in the long-term storage (30 days). Mechanism studies indicated that the excellent sensing property derived from the doping of transition metals. Moreover, the moisture-enhanced adsorption of CCl₄ for the MIL-127 (Fe₂Co) 3-D PC sensor is also observed. H₂O molecule can remarkably enhance the adsorption of MIL-127 (Fe₂Co) to CCl₄. The MIL-127 (Fe₂Co) 3-D PC sensor shows the highest concentration sensitivity of 0.146 ± 0.00082 nm ppm^-1 to CCl₄ and the lowest limit of detection (LOD) of 685 ± 4 ppb under the pre-adsorption of 75 ppm H₂O. Our results provide an insight for a trace gas detection using metal-organic frameworks (MOFs) in the optical sensing field.

Metal-Organic Framework with a Redox-Active Bridge Enables Electrochemically Highly Selective Removal of Arsenic from Water

Selective removal of trace, highly toxic arsenic from water is vital to ensure an adequate and safe drinking water supply for over 230 million people around the globe affected by arsenic contamination. Here, we developed an Fe-based metal-organic framework (MOF) with a ferrocene (Fc) redox-active bridge (termed Fe-MIL-88B-Fc) for the highly selective removal of As(III) from water. At a cell voltage of 1.2 V, Fe-MIL-88B-Fc can selectively separate and oxidize As(III) into the less harmful As(V) state in the presence of a 100- to 1250-fold excess of competing electrolyte, with an uptake capacity of >110 mg-As g^-1 adsorbent. The high affinity between the uncharged As(III) and the μ₃-O trimer (-36.55 kcal mol^-1) in Fe-MIL-88B-Fc and the electron transfer between As(III) and redox-active Fc⁺ synergistically govern the selective capture and conversion of arsenic. The Fe-based MOF demonstrates high selectivity and capacity to remediate arsenic-contaminated natural water at a low energy cost (0.025 kWh m^-3). This study provides valuable guidance for the tailoring of effective and robust electrodes, which can lead to a wider application of electrochemical separation technologies.

Boosting the Adsorption Performance of Thiophenic Sulfur Compounds with a Multimetallic Dual Metal-Organic Framework Composite

Adsorptive desulfurization over metal-organic frameworks (MOFs) remains a challenge in maintaining good performance in the presence of water. Herein, multimetallic Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) is first achieved through phase-competition-driven growth technology. The adsorption performance of thiophene (Th), benzothiophene (BT), and dibenzothiophene (DBT) in model fuels is systematically investigated at mild temperature and follows the order Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) > MOF-5 > MIL-88B. Excellent adsorptive activity is mainly ascribed to the associative effects of multimetal active sites, suitable pore sizes and shapes, acid-base interactions, and complexation. Meanwhile, MIL-88B exhibits a "brick-wall" effect and effectively enhances the water stability of Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) more than does MOF-5. Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) exhibits superior stability even after being immersed in water for 5 days, maintaining 77, 77, and 81% of the initial DBT, BT, and Th uptake capacities. After five periods of regeneration, more than 90% of the desulfurization capacity of Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) was recovered. This work provides a new strategy for the synthesis of desirable MOF-on-MOF, promoting its potential application to adsorption desulfurization.

A quest for cytocompatible metal organic frameworks in non-viral gene therapy: Relevance of zeolitic imidazolate framework-8

Metal-organic frameworks (MOFs) are an emerging group of nanomaterials for successful biomedical applications in gene therapy. The most commonly biocompatible MOFs are zinc-based ZIFs, zirconium-based UiOs, and iron-based MILs. However, despite increasing applications, a comparative study to underscore the critical factors for determining effective gene delivery by such MOFs is lacking. Herein, we evaluate the potential of UiO-66 and MIL-88B and ZIF-8 for gene therapeutics delivery; revealing the comparative importance of ZIF-8. Cytotoxicity assays proved insufficient for selecting the ideal gene delivery MOF vehicle. Synthesis conditions such as ability of the MOF scaffold to envelop the gene during in-situ synthesis, post-treatment such as washing, and gene loading efficiency proved to be the critical factors in determining the favourable MOF from the material selection perspective. Rapid in-situ synthesis under physiological conditions, successful gene loading, and low concentration requirements favour ZIF MOFs as gene delivery vehicles. Impact on cellular physiology, metabolism, and architecture revealed neutrality of the delivery system; and relative effects on pro-inflammatory and anti-inflammatory cytokines suggest immunomodulatory impact.

Programmable Drug Release from a Dual-Stimuli Responsive Magnetic Metal-Organic Framework

Along with the increasing incidence of cancer and drawbacks of traditional drug delivery systems (DDSs), developing novel nanocarriers for sustained targeted-drug release has become urgent. In this regard, metal-organic frameworks (MOFs) have emerged as potential candidates due to their structural flexibility, defined porosity, lower toxicity, and biodegradability. Herein, a FeMn-based ferromagnetic MOF was synthesized from a preassembled Fe₂Mn(μ₃-O) cluster. The introduction of the Mn provided the ferromagnetic character to FeMn-MIL-88B. 5-Fluoruracil (5-FU) was encapsulated as a model drug in the MOFs, and its pH and H₂S dual-stimuli responsive controlled release was realized. FeMn-MIL-88B presented a higher 5-FU loading capacity of 43.8 wt % and rapid drug release behavior in a tumor microenvironment (TME) simulated medium. The carriers can rapidly release loaded drug of 70% and 26% in PBS solution (pH = 5.4) and NaHS solution (500 μM) within 24 h. The application of mathematical release models indicated 5-FU release from carriers can be precisely fitted to the first-order, second-order, and Higuchi models of release. Moreover, the cytotoxicity profile of the carrier against human embryonic kidney cells (HEK293T) suggests no adverse effects up to 100 μg/mL. The lesser toxic effect on cell viability can be attributed to the low toxicity values [LD₅₀ (Fe) = 30 g·kg^-1, (Mn) = 1.5 g·kg^-1, and (terephthalic acid) = 5 g·kg^-1] of the MOFs structural components. Together with dual-stimuli responsiveness, ferromagnetic nature, and low toxicity, FeMn-MIL-88B MOFs can emerge as promising carriers for drug delivery applications.

Facile Fabrication of Novel NiFe2O4@Carbon Composites for Enhanced Adsorption of Emergent Antibiotics

Water purification is becoming one of the most pertinent environmental issues throughout the world. Among common types of water pollution involving heavy metals, pharmaceutical drugs, textile dyes, personal care products, and other persistent organic pollutants, the pollution of antibiotic drugs is increasingly emerging due to their adverse effects on microorganisms, aquatic animals, and human health. Therefore, the treatment of such contaminants is very necessary to reduce the concentration of antibiotic pollutants to permissible levels prior to discharge. Herein, we report the use of NiFe₂O₄@C composites from a bimetallic-based metal-organic framework Ni-MIL-88B(Fe) for removal of ciprofloxacin (CFX) and tetracycline (TCC). The effect of production temperatures (600–900 °C), solution pH (2–10), NiFe₂O₄@C dose (0.05–0.2 g/L), concentration of antibiotics (10–60 mg/L), and uptake time (0–480 min) was investigated systematically. Response surface methodology and central composite design were applied for quadratic models to discover optimum conditions of antibiotic adsorption. With high coefficients of determination (R² = 0.9640–0.9713), the proposed models were significant statistically. Under proposed optimum conditions, the adsorption capacity for CFX and TCC were found at 256.244, and 105.38 mg/g, respectively. Recyclability study was employed and found that NiFe₂O₄@C-900 could be reused for up to three cycles, offering the potential of this composite as a good adsorbent for removal of emergent antibiotics.

A universal route to fabricate bacterial cellulose-based composite membranes for simultaneous removal of multiple pollutants

A self-standing, robust bacterial cellulose (BC)-based multifunctional composite membrane embedded with desirable nano-adsorbents has been successfully fabricated via a facile versatile strategy. As expected, the developed BC-based composite membrane enables the simultaneous and efficient removal of multiple co-existing pollutants.

Improved photodegradation of anionic dyes using a complex graphitic carbon nitride and iron-based metal-organic framework material

Introducing heterostructures to graphitic carbon nitrides (g-C3N4) can improve the activity of visible-light-driven catalysts for the efficient treatment of multiple toxic pollutants in water. Here, we report for the first time that a complex material can be constructed from oxygen-doped g-C3N4 and a MIL-53(Fe) metal-organic framework using facile hydrothermal synthesis and recycled polyethylene terephthalate from plastic waste. The novel multi-walled nanotube structure of the O-g-C3N4/MIL-53(Fe) composite, which enables the unique interfacial charge transfer at the heterojunction, showed an obvious enhancement in the separation efficiency of the photochemical electron-hole pairs. This resulted in a narrow bandgap energy (2.30 eV, compared to 2.55 eV in O-g-C3N4), high photocurrent intensity (0.17 mA cm-2, compared to 0.12 mA cm-2 and 0.09 mA cm-2 in MIL-53(Fe) and O-g-C3N4, respectively) and excellent catalytic performance in the photodegradation of anionic azo dyes (95% for RR 195 and 99% for RY 145 degraded after 4 h, and only a minor change in the efficiency observed after four consecutive tests). These results demonstrate the development of new catalysts made from waste feedstocks that show high stability, ease of fabrication and can operate in natural light for environmental remediation.

Electrocatalytic performance of NiNH2BDC MOF based composites with rGO for methanol oxidation reaction

Present work comprehensively investigated the electrochemical response of Nickel-2 Aminoterephthalic acid Metal-Organic Framework (NiNH2BDC) and its reduced graphitic carbon (rGO) based hybrids for methanol (CH3OH) oxidation reaction (MOR) in an alkaline environment. In a thorough analysis of a solvothermally synthesized Metal-Organic Frameworks (MOFs) and its reduced graphitic carbon-based hybrids, functional groups detection was performed by FTIR, the morphological study by SEM, crystal structure analysis via XRD, and elemental analysis through XPS while electrochemical testing was accomplished by Chronoamperometry (CA), Cyclic Voltametric method (CV), Electrochemically Active Surface Area (EASA), Tafel slope (b), Electron Impedance Spectroscopy (EIS), Mass Activity, and roughness factor. Among all the fabricated composites, NiNH2BDC MOF/5 wt% rGO hybrid by possessing an auspicious current density (j) of 267.7 mA/cm2 at 0.699 V (vs Hg/HgO), a Tafel slope value of 60.8 mV dec-1, EASA value of 15.7 cm2, and by exhibiting resistance of 13.26 Ω in a 3 M CH3OH/1 M NaOH solution displays grander electrocatalytic activity as compared to state-of-the-art platinum-based electrocatalysts.

Bimetallic Coordination in Two-Dimensional Metal–Organic Framework Nanosheets Enables Highly Efficient Removal of Heavy Metal Lead (II)

Two-dimensional (2D) metal–organic frameworks (MOFs) have emerged as intriguing 2D materials because of their specific features of 2D morphology and designable skeletons, which have elicited great interest in environment remediation. In this work, 2D MOF nanosheets are fabricated via a mixed-solvent solvothermal method, and a regulation strategy of metal inorganic clusters on MOFs is used to construct two different 2D MOFs with monometallic and bimetallic coordination, that is, Ni-MOF and Ni/Cd-MOF. Binary metal coordination renders more crystal defects and vacancies in the framework; thus, compared to monometallic Ni-MOF, bimetallic Ni/Cd-MOF exhibits fewer layers (4∼5 layers), higher specific surface area, larger pore size, and higher surface electronegativity, which leads to its excellent adsorption removal for Pb2+, with higher adsorption rate and affinity, and superior adsorption capacity (950.61 mg/g, almost twice as high as that of monometallic Ni-MOF). Besides, the adsorption mechanism further confirmed that the carboxyl groups (−COO−) from organic linker on 2D MOFs serve as the main binding sites for Pb2+ coordination, and bimetallic Ni/Cd-MOF has more active −COO− sites for Pb2+ capture. Thus, the bimetallic Ni/Cd-MOF regulated by heterogeneous metal atoms shows promising application for highly efficient adsorption of heavy metal ions.

Single- and mixed-metal–organic framework photocatalysts for carbon dioxide reduction

This review focuses on the important roles of varied metal types over MOF-based photocatalysts. The basic principles, types of MOF photocatalysts and roles of the reaction system to achieve efficient MOFs for CO₂ photoreduction are discussed.

Bimetallic metal-organic frameworks anchored corncob-derived porous carbon photocatalysts for synergistic degradation of organic pollutants

Metal-organic frameworks (MOFs) are promising for photocatalysis owing to their excellent structure and performance. Unfortunately, poor stability in both aqueous solutions and high temperatures and lack of adsorption centers during reactions limit their practical applications. Herein, a bimetallic MOF anchored corncob calcined derived activated carbon (CCAC) was successfully prepared by a one-step solvothermal method. Benefiting from unique structures and synergetic effect, the porous carbon provided a high specific surface area for stable MOF support and served as an organic pollutant buffer-reservoir, which was advantageous for efficient photocatalytic degradation of organic pollutants. The optimized MOF/CCAC-5 samples possessed excellent visible light degradation rate, i.e., 100% for Rh B, more than 96% for six mixed dyes, and 98% for tetracycline. This prominent photocatalytic activity was caused by active species, including photoelectrons (e^-), photo-holes (h⁺) and superoxide free radicals (•O^2-). The transient photocurrent response and electrochemical impedance tests showed that MOF/CCAC-5 exhibited a relatively high charge separation and low carrier recombination rate. Cyclic and simulation experiments indicated high reusability, stability and universality of the composite photocatalysts. These exciting results provide new pathways for the fabrication of MOFs anchored porous carbon materials.

Metal-Organic Framework-Derived NiS/Fe3O4 Heterostructure-Decorated Carbon Nanotubes as Highly Efficient and Durable Electrocatalysts for Oxygen Evolution Reaction

Because of the sluggish oxygen evolution kinetics, it is extremely important but still challenging to develop low-cost, efficient, and stable electrocatalysts for oxygen evolution reaction (OER) to enhance the efficiency of water electrolysis. Herein, for the first time, we present a novel heterostructure catalyst, constructed by ultrafine NiS/Fe₃O₄ heterostructural nanoparticles decorated on a carbon nanotube (CNT) matrix (NiS/Fe₃O₄ HNPs@CNT), which is synthesized by a facile hydrothermal reaction and subsequent sulfurization process. The NiS/Fe₃O₄ HNPs@CNT hybrid delivers superior OER activity in alkaline medium: it delivers a current density of 10 mA cm^-2 at an ultralow overpotential of 243 mV with a small Tafel slope of 44.2 mV dec^-1, which outperforms the benchmark RuO₂ electrocatalyst; moreover, it exhibits terrific long-term stability over 36 h without any noticeable performance decay. The exceptional OER performance can be attributed to the unique nanoarchitecture, high conductivity of the CNT matrix, and particularly, the interaction between the Ni and Fe species in NiS/Fe₃O₄ heterostructural nanoparticles. This work introduces a sensible nanoarchitecture design with a facile and novel fabrication strategy to attain nonprecious metal-based composite catalysts with high OER performance and outstanding long-term stability.

Fe–Ni metal–organic frameworks with prominent peroxidase-like activity for the colorimetric detection of Sn2+ ions

The synthesized Fe–Ni-MOF could oxidize TMB to produce oxTMB with blue color. The presence of Sn²⁺ ions could make the oxTMB color lighter, hence colorimetric detection of Sn²⁺ ions is realized.

Nature-mimic fabricated polydopamine/MIL-53(Fe): efficient visible-light responsive photocatalysts for the selective oxidation of alcohols

PDA/MIL-53(Fe) nanocomposites prepared via a nature-mimicking method were efficient catalysts towards the photocatalytic selective oxidation of alcohols to aldehydes or ketones by a direct holeoxidation process under visible-light illuminated conditions.

The Synthesis of N-(Pyridin-2-yl)-Benzamides from Aminopyridine and Trans-Beta-Nitrostyrene by Fe2Ni-BDC Bimetallic Metal–Organic Frameworks

A bimetallic metal–organic framework material, which was generated by bridging iron (III) cations and nickel (II) cations with 1,4-Benzenedicarboxylic anions (Fe2Ni-BDC), was synthesized by a solvothermal approach using nickel (II) nitrate hexahydrate and iron (III) chloride hexahydrate as the mixed metal source and 1,4-Benzenedicarboxylic acid (H2BDC) as the organic ligand source. The structure of samples was determined by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and nitrogen physisorption measurements. The catalytic activity and recyclability of the Fe2Ni-BDC catalyst for the Michael addition amidation reaction of 2-aminopyridine and nitroolefins were estimated. The results illustrated that the Fe2Ni-BDC catalyst demonstrated good efficiency in the reaction under optimal conditions. Based on these results, a reaction mechanism was proposed. When the molar ratio of 2-aminopyridine and trans-β-nitrostyrene was 1:1, and the solvent was dichloromethane, the isolated yield of pyridyl benzamide reached 82%; at 80 °C over 24 h. The catalyst can be reused without a substantial reduction in catalytic activity with 77% yield after six times of reuse.

In Situ Confined Bimetallic Metal-Organic Framework Derived Nanostructure within 3D Interconnected Bamboo-like Carbon Nanotube Networks for Boosting Electromagnetic Wave Absorbing Performances

Metal-organic framework (MOFs) derived magnetic nanoparticles/porous carbon (M/C) composites featuring efficient interfacial engineering and spatially continuous three-dimensional (3D) networks are desirable electromagnetic wave (EMW) absorbing materials due to multiple transmission path and well impedance matching. However, it is challenging to construct such 3D interconnected carbon networks from a single MOF precursor. Herein, FeNi₃ and N embedded 3D carbon networks comprising bamboo-like carbon nanotubes connected carbon nanorods (FeNi@CNT/CNRs) were prepared via one-step pyrolyzing of the composite of melamine and FeNi-MIL-88B. Attributed to the synergistic contributions of 3D interconnected carbon nanotube networks and MOFs derived M/C for multiple transmission path, impedance matching, and dielectric loss (especially for multiple polarization and micro-current), the FeNi@CNT/CNRs nanoarchitectures have demonstrated superior EMW absorbing performance. In particular, the optimized FeNi@CNT/CNR-0.9 has exhibited strong absorption (-47.0 dB, 2.3 mm in thickness) and broadband effective absorption (4.5 GHz, 1.6 mm in thickness). This attractive strategy holds promise as a general approach to fabricate the carbon hybrid network constituted of MOFs derived nanopolyhedron and CNTs for the target application.

Mixed-Metal MOFs: Unique Opportunities in Metal-Organic Framework (MOF) Functionality and Design

Mixed-metal metal-organic frameworks (MM-MOFs) can be considered to be those MOFs having two different metals anywhere in the structure. Herein we summarize the various strategies for the preparation of MM-MOFs and some of their applications in adsorption, gas separation, and catalysis. It is shown that compared to homometallic MOFs, MM-MOFs bring about the opportunity to take advantage of the complexity and the synergism derived from the presence of different metal ions in the structure of MOFs. This is reflected in a superior performance and even stability of MM-MOFs respect to related single-metal MOFs. Emphasis is made on the use of MM-MOFs as catalysts for tandem reactions.

Replacement of Chromium by Non-Toxic Metals in Lewis-Acid MOFs: Assessment of Stability as Glucose Conversion Catalysts

The metal–organic framework MIL-101(Cr) is known as a solid–acid catalyst for the solution conversion of biomass-derived glucose to 5-hydroxymethyl furfural (5-HMF). We study the substitution of Cr3+ by Fe3+ and Sc3+ in the MIL-101 structure in order to prepare more environmentally benign catalysts. MIL-101(Fe) can be prepared, and the inclusion of Sc is possible at low levels (10% of Fe replaced). On extended synthesis times the polymorphic MIL-88B structure instead forms.Increasing the amount of Sc also only yields MIL-88B, even at short crystallisation times. The MIL-88B structure is unstable under hydrothermal conditions, but in dimethylsulfoxide solvent, it provides 5-HMF from glucose as the major product. The optimum material is a bimetallic (Fe,Sc) form of MIL-88B, which provides ~70% conversion of glucose with 35% selectivity towards 5-HMF after 3 hours at 140 °C: this offers high conversion compared to other heterogeneous catalysts reported in the same solvent.

Benzoic acid as a selector-modulator in the synthesis of MIL-88B(Cr) and nano-MIL-101(Cr)

The concentration of benzoic acid was found to exercise efficient control over the formation of either MIL-101(Cr) or MIL-88B(Cr) under otherwise similar hydrothermal synthetic conditions. Nanocrystals of MIL-101(Cr) with ∼100 nm average size and excellent SBET = 3467 m2 g-1 are obtained at lower concentrations of benzoic acid, while at higher concentrations the microparticulated MIL-88B(Cr) product is formed. Hereby a new efficient synthetic method towards the elusive MIL-88B(Cr), yet reported only once without synthetic details, is proposed. The obtained MIL-88B(Cr) has an interesting and potentially valuable property of retaining its high-volume form (Vcell ∼ 2000 Å3) after thermal activation. The degassing of MIL-88B(Cr) in a vacuum at 250 °C yields a porous material with a SBET area of 1136 m2 g-1, which is around the theoretical maximum. The transition to the denser 'closed' form (Vcell ∼ 1500 Å3) occurs only at 350 °C, when all of the benzoate/benzoic acid, hindering the process, is removed.

Role of MIL-53(Fe)/hydrated–dehydrated MOF catalyst for electrochemical hydrogen evolution reaction (HER) in alkaline medium and photocatalysis

The role of breathing behavior in hydrated and dehydrated forms of MIL-53(Fe) is investigated here.

Multimetal organic frameworks as drug carriers: aceclofenac as a drug candidate

BACKGROUND

Multimetal organic frameworks (M-MOFs) were synthesized by including a second metal ion with the main base metal in the synthesis process to enhance their applications for drug delivery. Aceclofenac (ACF), a nonsteroidal anti-inflammatory analgesic drug of low aqueous solubility, was selected as a candidate for the drug delivery system.

PURPOSE

This study aimed to evaluate the loading capacity (LC) and entrapment efficiency (EE) percentages of multi-Material of Institute Lavoisier (MIL)-100(Fe) (M-MIL-100(Fe)) for ACF.

MATERIALS AND METHODS

Hydrothermal synthesis procedure was used to prepare multi-MIL-100(Fe) samples (Zn I-MIL-100(Fe), Zn II-MIL-100(Fe), Ca I-MIL-100(Fe), Ca II-MIL-100-(Fe), Mg I-MIL-100(Fe), Mg II-MIL-100(Fe), Mn I-MIL-100(Fe), and Mn II-MIL-100(Fe)). The characterization of M-MIL-100(Fe) samples was evaluated by X-ray powder diffraction (XRD), Fourier transform infrared spectra, scanning electron microscope (SEM), TGA, and N2 adsorption isotherms. The LC of M-MIL-100(Fe) and EE of ACF were determined. Nuclear magnetic resonance (NMR) and zeta-potential analyses were employed to confirm qualitatively the drug loading within M-MIL-100(Fe).

RESULTS

The ACF LC of MIL-100(Fe) was 27%, whereas the LC of M-MIL-100(Fe) was significantly increased and ranged from 37% in Ca I-MIL-100(Fe) to about 57% and 59% in Mn II-MIL-100(Fe) and Zn II-MIL-100(Fe), respectively. The ACF@M-MOFs release profiles showed slow release rates in phosphate buffer solutions at pH 6.8 and 7.4 as compared to the ACF@MIL-100(Fe).

CONCLUSION

Therefore, M-MOFs showed a significant potential as a carrier for drug delivery systems.

Effective Photocatalytic Activity of Mixed Ni/Fe-Base Metal-Organic Framework under a Compact Fluorescent Daylight Lamp

Mixed Ni/Fe-base metal-organic framework (Ni/Fe-MOF) with different molar ratios of Ni2+/Fe3+ have been successfully produced using an appropriate solvothermal router. Physicochemical properties of all samples were characterized using X-ray diffraction (XRD), Raman, field emission scanning electron microscopes (FE-SEM), fourier-transform infrared spectroscopy (FT-IR), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectra (PL). The photocatalytic degradation performances of the photocatalysts were evaluated in the decomposition of rhodamine B (RhB) under a compact fluorescent daylight lamp. From XRD, IR, XPS, and Raman results, with the presence of mixed ion Fe3+ and Ni2+, MIL-88B (MIL standing for Materials of Institut Lavoisier) crystals based on the mixed metal Fe2NiO cluster were formed, while MIL-53(Fe) was formed with the presence of single ion Fe3+. From UV-Vis DRS results, Ni/Fe-MOF samples exhibited the absorption spectrum up to the visible region, and then they showed the high photocatalytic activity under visible light irradiation. A Ni/Fe-MOF sample with a Ni2+/Fe3+ molar ratio of 0.3 showed the highest photocatalytic degradation capacity of RhB, superior to that of the MIL-53(Fe) sample. The obtained result could be explained as a consequence of the large surface area with large pore volumes and pore size by the Ni2+ incorporating into the MOF’s structure. In addition, a mixed metal Fe/Ni-based framework consisted of mixed-metal cluster Fe2NiO with an electron transfer effect and may enhance the photocatalytic performance.