Facile and Large-Scale Syntheses of Nanocrystal Rare Earth Metal–Organic Frameworks at Room Temperature and Their Photoluminescence Properties

Magnetic Switching of Second-Harmonic Generation from Single Cerium-Based Coordination Polymer Microcrystals

Conventional access and modulation of second-harmonic generation (SHG) require precise control of crystal orientation, which faces great mechanical challenges in the case of micro/nanocrystals. Here, we demonstrate the magnetic-field-tunable SHG performance of lanthanide coordination polymer (Ce-BTC CP) microcrystals through field-aligned orientations. The coordination of Ce ions and organic ligands constructs a noncentrosymmetric structure, which not only contributes to a favorable powder SHG efficiency 3.2 times larger than that of the benchmark KH2PO4 (KDP) but also endows the microcrystals with strong magnetic anisotropy. The SHG efficiency (∼0 to 10 × KDP) depends on the orientation of the crystallographic c-axis, whereas magnetic anisotropy always aligns the c-axis with the magnetic field at a specific angle. Accordingly, the SHG can be magnetically switched by field-induced alignments. The adsorption of dyes by Ce-BTC CPs further facilitates the magnetic switching of multicolor fluorescence that can be excited by the SHG. Our work provides a new pathway for achieving SHG modulation at the microscopic level.

Constructing oxygen vacancy-rich MXene @Ce-MOF composites for enhanced energy storage and conversion

Oxygen vacancies can regulate the coordination structure and electronic states of atoms, thus promoting the formation of surface-active sites and increasing the conductivity of the electrode material. This work presents a design for MXene@Ce-MOF composites with abundant oxygen vacancies. The hydroxyl groups on the surface of monolayer MXene attract cerium ions, which create surface defects in Ce-MOF and further promote the formation of oxygen vacancies. This results in a significant improvement in energy storage capacity, as well as performance in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The MXene@Ce-MOF composite exhibits a specific capacity of 496 F g^-1, which is 1.8 times higher than that of pure Ce-MOF and 3.5 times higher than MXene alone. At a current density of 10 mA cm^-2, the overpotential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is as low as 270 and 220 mV, respectively, and the composite exhibits excellent cycling stability. Oxygen vacancy-based MOF composites play a crucial role in electrocatalysis and energy conversion.

Optimization and Synthesis of a La-TMA MOF with Some Improvements in Its Properties

A La-TMA metal-organic framework (MOF) made up of benzene-1,3,5-tricarboxylate and La(III) was synthesized by a different methodology compared to those in previous reports. By using various approaches, the structural characteristics and physical properties of the La-TMA MOF were analyzed. Eventually, the results showed micro-hexagonal hollow tubes with a high crystallinity grade and thermal stability (up to 400 °C) and a higher surface area compared with those from earlier reports. The BET surface area of a similar previous MOF was about 14.8 m²/g; however, in the current project, the BET surface area increased to about 34.49 m²/g and the Langmuir surface area to 42.3 m²/g.

Construction of trifunctional electrode material based on Pt-Coordinated Ce-Based metal organic framework

The main challenge hindering the use of Pt nanoparticles (Pt NPs) for electrochemical applications is their high cost and agglomeration. Herein, a trifunctional electrode material based on a two-dimensional cerium-based metal organic framework (2D Ce-MOF) decorated with Pt NPs is constructed. The large specific surface area of the 2D Ce-MOF can effectively prevent the phenomenon of Pt NPs reaction. The strong synergy between Pt NPs and the 2D Ce-MOF not only significantly enhances electron transport efficiency, but also increases the number of electrochemically reaction reactive sites. As a result, the Ce-MOF@Pt presents excellent performance in the HER (Hydrogen Evolution Reaction), OER (Oxygen Evolution Reaction) and supercapacitor reactions. The Tafel slopes of OER and HER are 47.9 and 188.1 mV dec^-1, respectively. Meanwhile, Ce-MOF@Pt-0.05 shows a specific capacity of 1894F g^-1 at a current density of 1 A g^-1 and remains at 111.5% of the initial capacitance after 3000 cycles. In general, this study highlights the importance of Pt NPs in promoting the electrochemical performance of MOFs and reveals a new way to reduce electrocatalyst prices.

Co-Quenching Effect between Lanthanum Metal-Organic Frameworks Luminophore and Crystal Violet for Enhanced Electrochemiluminescence Gene Detection

Exploring new electrochemiluminescence (ECL) luminophores to construct high-efficiency sensing systems is always a hot direction for developing ECL sensors. Compared with other luminophores, metal-organic frameworks (MOFs) exhibit high mass transfer ability for accelerating the reactivity in its pore channels, which is conducive to improving the performance of ECL sensors. In this work, La³⁺ -BTC MOFs (LaMOFs) are prepared as the highly active reactor and novel ECL luminophore. On this basis, a novel co-quenching effect mechanism is proposed based on double-stranded DNA (dsDNA) triggered cooperation between LaMOFs and crystal violet (CV) molecules. Under the confined pore channels of LaMOFs, CV can play an important role as the photon-acceptor due to the matched absorption spectrum with the ECL spectrum of LaMOFs, and the electron-acceptor on account of its lowest unoccupied molecular orbital level. Based on the proposed co-quenching effect mechanism, a constructed ECL gene sensor shows good assay performance toward p53 gene in the detection range of 1 pm to 100 nm with a detection limit of 0.33 pm. The co-quenching effect integrating LaMOFs with CV is expected to be a versatile approach in the construction of ECL gene sensor, which has good prospect in expanding the application range of ECL technology.

Ultrasound-Assisted Synthesis of Luminescent Micro- and Nanocrystalline Eu-Based MOFs as Luminescent Probes for Heavy Metal Ions

The luminescent coarse-, micro- and nanocrystalline europium(III) terephthalate tetrahydrate (Eu₂bdc₃·4H₂O) metal-organic frameworks were synthesized by the ultrasound-assisted wet-chemical method. Electron micrographs show that the europium(III) terephthalate microparticles are 7 μm long leaf-like plates. According to the dynamic light scattering technique, the average size of the Eu₂bdc₃·4H₂O nanoparticles is equal to about 8 ± 2 nm. Thereby, the reported Eu₂bdc₃·4H₂O nanoparticles are the smallest nanosized rare-earth-based MOF crystals, to the best of our knowledge. The synthesized materials demonstrate red emission due to the ⁵D₀–⁷F_J transitions of Eu³⁺ upon 250 nm excitation into ¹ππ* state of the terephthalate ion. Size reduction results in broadened emission bands, an increase in the non-radiative rate constants and a decrease in both the quantum efficiency of the ⁵D₀ level and Eu³⁺ and the luminescence quantum yields. Cu²⁺, Cr³⁺, and Fe³⁺ ions efficiently and selectively quench the luminescence of nanocrystalline europium(III) terephthalate, which makes it a prospective material for luminescent probes to monitor these ions in waste and drinking water.

Bi Metal-Organic Framework (Ce/Ni-BTC) as Heterogeneous Catalyst for the Green Synthesis of Substituted Chromeno[4, 3-b]quinolone under Solvent Free Condition

AIMS

Novel bi metal organic framework (b-MOF) is synthesized and used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot and solvent-free, four-component reaction of dimedone, aromatic aldehydes, 4-hydroxycoumarin and ammonium acetate at 110°C.

BACKGROUND

b-MOFs can be used as a heterogeneous catalyst in the synthesis of many organic compounds. The active and multi-purpose sites in b-MOFs provide a varied function in their catalytic applications. In this paper, reductive CES method is applied for the synthesis of Ce_0.47/Ni_0.53-BTC b-MOF. The resulting b-MOF was used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone via one-pot and solvent-free, fourcomponent reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate at 110 °C.

METHOD

Ce_0.47/Ni_0.53-BTC was synthesized in an electrochemical cell composed of a stainless steel foil with a size of 5cm×5cm centered between two 5cm×5cm sized graphite plates as the anodes by the cathodic current density of 0.2 A/dm² and placed in a solution of cerium nitrate (0.3 g), nickel nitrate (0.3 g), H₃BTC (0.2 g) and NaNO₃ (0.1 g) in ethanol (500 mL). Ce_0.47/Ni_0.53-BTC (10 mg) was added to a mixture of dimedone (1 mmol), aromatic aldehyde (1 mmol), hydroxycoumarin (1 mmol) and ammonium acetate (1.5 mmol) and stirred at 110 °C under solvent-free conditions for 45 min. The reaction evolution was controlled by the TLC (hexane:ethyl acetate, 4:1). Then, boiling ethanol was added to the reaction mixture and stirred at room temperature for 15 min. After the reaction completion, the catalyst was separated by centrifuge. Finally, the reaction mixture was placed in an ice bath, which resulted in a white solid product and recrystallized from ethanol to give the pure product.

RESULT

The b-MOF catalyst showed very good efficiency in the synthesis of the desired compounds and can be easily recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

CONCLUSION

In this report, a novel bi metal-organic framework (Ce0.47/Ni0.53-BTC) is synthesized via the cathodic electrosynthesis method. The synthesized b-MOF is fully characterized by several characterization methods. The catalytic activity of Ce0.47/Ni0.53-BTC is investigated in the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot four-component reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate. The reaction optimization results showed that the highest isolated yield was obtained when the reaction was performed in solvent-free conditions at 110 °C. The catalyst showed to be highly efficient in the synthesis of the desired compounds and performing the reaction utilizing various starting materials gave the products in good isolated yields, which proves the generality and the scope of the method. The catalyst could easily be recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

Fast and efficient aqueous arsenic removal by functionalized MIL-100(Fe)/rGO/δ-MnO2 ternary composites: Adsorption performance and mechanism

Because of its significant toxicological effects on the environment and human health, arsenic (As) is a major global issue. In this study, an Fe-based metal-organic framework (MOF) (Materials of Institut Lavoisier: MIL-100 (Fe)) which was impregnated with reduced graphene oxide (rGO) by using a simple hydrothermal method and coated with birnessite-type manganese oxide (δ-MnO₂) using the one-pot reaction process (MIL-100(Fe)/rGO/δ-MnO₂ nanocomposites) was synthesized and applied successfully in As removal. The removal efficiency was rapid, the equilibrium was achieved in 40 min and 120 min for As(III) and As(V), respectively, at a level of 5 mg/L. The maximum adsorption capacities of As(III) and As(V) at pH 2 were 192.67 mg/g and 162.07 mg/g, respectively. The adsorbent revealed high stability in pH range 2-9 and saturated adsorbent can be fully regenerated at least five runs. The adsorption process can be described by the pseudo-second-order kinetic model and Langmuir monolayer adsorption. The adsorption mechanisms consisted of electrostatic interaction, oxidation and inner sphere surface complexation.

3D Printing of Mixed Matrix Films Based on Metal-Organic Frameworks and Thermoplastic Polyamide 12 by Selective Laser Sintering for Water Applications

The fabrication of metal-organic framework (MOF)-based macro-materials is considered as a promising strategy toward the practical applications of powdered MOF crystals. In this study, selective laser sintering (SLS), an advanced three-dimensional (3D) powder printing technique, has been employed to fabricate MOF-polymer mixed matrix films (MMFs) by using thermoplastic polyamide 12 (PA12) powder as the matrix material and five types of MOFs including ZIF-67, NH₂-MIL-101(Al), MOF-801, HKUST-1, and ZIF-8 crystals as the fillers. A three-layer HKUST-1-PA12 complex with a grid pattern is fabricated to demonstrate the printability of 3D MOF-polymer structure. Single-layer MMFs with grid patterns are printed by using the five types of MOF fillers with different mass loadings to study their free-standing characteristic, thickness, specific surface area, hydrophilia, water permeate flux, and mechanical stability. The methylene blue (MB) adsorption tests are conducted using the NH₂-MIL-101(Al)-PA12 MMFs with different grid patterns to exemplify the applications of the MMFs for water purification. It is confirmed that the MOF components retain their high maximum adsorption capacity, and the printed MMFs can be conveniently regenerated for cyclic utilization. This work provides an insight into the utilization of advanced 3D printing technology to manufacture macro-MOF-polymer materials for practical applications.

Sonochemical synthesis of amide-functionalized metal-organic framework/graphene oxide nanocomposite for the adsorption of methylene blue from aqueous solution

Graphene oxide-[Zn₂(oba)₂(bpfb)]·(DMF)₅ metal-organic framework nanocomposite (GO-TMU-23; H₂oba=4,4'-oxybisbenzoic acid, bpfb=N,N'-bis-(4-pyridylformamide)-1,4-benzenediamine, DMF=N,N-dimethylformamide) is prepared through a simple and large-scale sonochemical preparation method at room temperature. The obtained nanocomposite is characterized by Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction (PXRD) and FT-IR spectroscopy. Additionally, the absorption ability of GO-TMU-23 nanocomposite toward cationic dye methylene blue was also performed. Significantly, GO-TMU-23 nanocomposite exhibits remarkably accelerated adsorption kinetics for methylene blue in comparison with the parent materials. The adsorption process shows that 90% of the dye has been removed and the equilibrium status has been reached in 2min by using the nanocomposites as the adsorbent.

Heterostructured Au NPs/CdS/LaBTC MOFs Photoanode for Efficient Photoelectrochemical Water Splitting: Stability Enhancement via CdSe QDs to 2D-CdS Nanosheets Transformation

The electrochemical stability of MOFs in aqueous medium is most essential for MOFs based electrocatalysts for hydrogen production via water splitting. Since most MOFs suffer from instability issues in aqueous systems, there is enormous demand for electrochemically stable MOFs catalysts. Herein, we have developed a simple postsynthesis surface modification protocol for La (1,3,5-BTC) (H2O)6 metal-organic frameworks (LaBTC MOFs) using Mercaptopropionic acid (MPA), to attain electrochemical stability in aqueous mediums. The MPA treated LaBTC MOFs exhibited better stability than the bare LaBTC. Further, to facilitate light harvesting properties of LaBTC MOFs, Au nanoparticles (NPs) and CdSe quantum dots (QDs) are functionalized on LaBTC. The sensitization of LaBTC with Au NPs and CdSe QDs enhances the light harvesting properties of LaBTC in the visible region of solar spectrum. Using as a photoanode, the electrode generates the current density of ∼80 mA/cm(2) at 0.8 V (vs Ag/AgCl) during photoelectrochemical water splitting. The heterostructured LaBTC photoanode demonstrates the long-term stability for the period of 10 h. The electrode post-mortem analysis confirms the conversion of CdSe QDs into single crystalline 2D-CdS nanosheets. The present investigation reveals that CdS nanosheets together with SPR Au NPs improve the photoelectrochemical water splitting activity and stability of LaBTC MOFs.

One-step growth of isoreticular luminescent metal–organic frameworks on cotton fibers

A series of isoreticular lanthanide metal–organic frameworks, Ln-MOFs (Ln = Eu, Gd, and Tb), were directly grown on cotton fibers using a room temperature water-based direct precipitation method.

Graphene oxide-rare earth metal-organic framework composites for the selective isolation of hemoglobin

Graphene oxide-La(BTC)(H2O)6 (H3BTC=1,3,5-benzenetricarboxylic acid) metal organic framework composites (LaMOF-GOn, n = 1-6, corresponding to the percentage of GO at 1, 2, 3, 4, 5, and 10%) are prepared through a simple and large-scale method at room temperature. The obtained composites are characterized by ATR-FTIR spectra, SEM, XRD, TGA, and N2 adsorption-desorption isotherm. The presence of GO significantly changes the morphologies of the composites from spindly rectangular rods to irregular thick blocks and increases their surface area from 14.8 cm(2) g(-1) (LaMOFs) to 26.6 cm(2) g(-1) (LaMOF-GO3), whereas at the same time, the crystalline structure of La(BTC)(H2O)6 is maintained. As a novel solid-phase adsorbent the LaMOF-GO composite exhibits outstanding adsorption properties for proteins. The strong hydrophobic interaction, especially π-π interaction between protein and the composite, is the main driving force for protein adsorption. In particular, highly selective isolation of hemoglobin (Hb) is achieved by using LaMOF-GO3 composite as sorbent in 4 mM B-R buffer containing 0.05 mol L(-1) NaCl at pH 8. The retained Hb could be effectively recovered with a 1 mM B-R buffer at pH 10, giving rise to a recovery of 63%. The practical applicability of the LaMOF-GO3 composite is demonstrated by the selective adsorption of Hb from human whole blood, and SDS-PAGE assays indicate that Hb could be selectively isolated with high purity from biological samples of complex matrixes.