Ratiometric Fluorescent Sensor Based on Tb(III) Functionalized Metal-Organic Framework for Formic Acid

Formic acid is a common chemical raw material, the effective detection of which is of importance to food safety and environmental quality. In this work, the lanthanide functionalized dual-emission metal-organic framework (TH25) was prepared as a ratiometric fluorescent sensor for formic acid. This ratiometric sensor has a good detection performance with high selectivity, sensitivity, and reproducibility. Together with a low limit of detection of 2.1 ppm, these characters promise the ability to sense at low levels as well as a practical detection ability. This work provides ideas for the design and synthesis of effective chemical sensors for organic acids.     

Highly Proton-Conductive Zinc Metal-Organic Framework Based On Nickel(II) Porphyrinylphosphonate

The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10⁻³ S cm⁻¹ at 75 °C and 80 % relative humidity).     

Porous Anionic Co(II) Metal-Organic Framework,with a High Density of Amino Groups,as a Superior Luminescent Sensor for Turn-on Al(III) Detection

Accumulation of high concentrations of Al(III) in body has a direct impact on health and therefore, the trace detection of Al(III) has been a matter for substantial concern. An anionic metal organic framework ({[Me₂NH₂]_0.5[Co(DATRz)_0.5(NH₂BDC)] ⋅ xG}_n; 1 ; HDATRz=3,5-diamino-1,2,4-triazole, H₂NH₂-BDC=2-amino-1,4-benzenedicarboxylic acid, G=guest molecule) composed of two types of secondary building units (SBU) and channels of varying sizes was synthesized by employing a rational design mixed ligand synthesis approach. Free −NH₂ groups on both the ligands are immobilized onto the pore surface of the MOF which acts as a superior luminescent sensor for turn-on Al(III) detection. Furthermore, the large channels could allow the counter-ions to pass through and get exchanged to selectively detect Al(III) in presence of other seventeen metal ions with magnificent luminescence enhancement. The observed limit of detection is as low as 17.5 ppb, which is the lowest among the MOF-based sensors achieved so far. To make this detection approach simple, portable and economic, we demonstrate MOF filter paper test for real time naked eye observation.     

A Doubly Interpenetrated Cu(II)-based Metal-Organic Framework as a Heterogeneous Catalyst for the ipso-Hydroxylation of Arylboronic Acids

A doubly interpenetrated Cu(II)-organic framework with formula [{Cu₂( L )₂(4,4′-bpdc)₂(H₂O)₂} ⋅ 8H₂O ⋅ CH₃OH]_α ( 1 ) (where, L =N², N⁶-di(pyridin-4-yl)naphthalene-2,6-dicarboxamide and 4,4′-bpdc=[1,1′-biphenyl]-4,4′-dicarboxylate ion) has been synthesized and characterized with the help of several spectroscopic and analytical techniques including single crystal X-ray analysis. A single crystal X-ray analysis reveals that 1 exhibit interpenetrated two-dimensional sheet-like structure containing elongated channels of cross-section 11.09×31.22 Ų along the a-axis. Finally, 1 has been exploited as a heterogeneous catalyst for the ipso-hydroxylation of arylboronic acids yielding up to 99 % of the respective phenolic product. Importantly, the catalyst can be reused for five successive cycles without having a significant loss in its catalytic efficiency.     

4-苄基氨甲酰苯基苯胺三氟甲磺酸盐(BCPPAT)：一种新型高效Friedel-Crafts苄基化和环己基化反应的催化剂

首次报道了一种新型高效、可循环使用的Friedel-Crafts反应催化剂——4-苄 基氨甲酰苯基苯胺三氟甲磺酸盐(BCPPAT)，它能够有效地催化芳烃的苄基化和环己 基化反应。     

Solvothermal Preparation of a Lanthanide Metal-Organic Framework for Highly Sensitive Discrimination of Nitrofurantoin and l-Tyrosine

Metal-organic frameworks (MOFs) have been rapidly developed for their broad applications in many different chemistry and materials fields. In this work, a multi-dentate building block 5-(4-(tetrazol-5-yl)phenyl)-isophthalic acid (H₃L) containing tetrazole and carbolxylate moieties was employed for the synthesis of a two-dimensional (2D) lanthanide MOF [La(HL)(DMF)₂(NO₃)] (DMF = N,N-dimethylformamide) (1) under solvothermal condition. The fluorescent sensing application of 1 was investigated. 1 exhibits high sensitivity recognition for antibiotic nitrofurantoin (K_sv: 3.0 × 10³ M⁻¹ and detection limit: 17.0 μM) and amino acid l-tyrosine (K_sv: 1.4 × 10⁴ M⁻¹ and detection limit: 3.6 μM). This work provides a feasible detection platform of 2D MOFs for highly sensitive discrimination of antibiotics and amino acids.     

Molecular Mobility of Tert-butyl Alcohol Confined in a Breathing MIL-53 (Al) Metal-Organic Framework

We present a detailed solid-state NMR characterization of the molecular dynamics of tert-butyl alcohol (TBA) confined inside breathing metal-organic framework (MOF) MIL-53(Al). ²⁷Al MAS NMR has demonstrated that TBA adsorption induces the iX phase of MIL-53 material with partially shrunk channels. ²H solid-state NMR has shown that the adsorbed alcohol exhibits anisotropic rotations of the methyl groups around two axes and librations of the molecule as a whole about the axis passing through the TBA C−O bond. These librations are realized by two distinct ways: fast molecule orientation change during the translational jump diffusion along the channel with characteristic time τ_D of about 10⁻⁹ s at 300 K; slow local librations at a single coordination site, representing framework hydroxyl groups, with τ_l≈10⁻⁶ s at 300 K. Self-diffusion coefficient of the alcohol in the MOF has been estimated: D=3.4×10⁻¹⁰ m² s⁻¹ at 300 K. It has been inferred that both the framework flexibility and the interaction with framework hydroxyl groups define the dynamics of TBA confined in the channels of MIL-53 (Al).     

Pd/MIL-101的制备及非均相催化吲哚C-H活化

水热合成MIL-101,过量浸渍法吸附Pd(OAc)_2,原位还原Pd~(2+)制得Pd/MIL-101催化剂.采用XRD、XPS、SEM、ICP、HRTEM和N_2吸/脱附实验对其结构进行表征,催化剂Pd纳米粒子尺寸在1.5~2.5 nm之间,含量为1.5%.催化实验表明,Pd/MIL-101能高效催化吲哚C_2位芳基化,对于活性较差的溴代芳烃,也能得到中等以上的收率,催化剂循环5次后仍能保持较高的反应活性,发展了吲哚C_2位衍生物的简单、高效的合成方法.     

Nickel-Based Metal-Organic Frameworks as Electrocatalysts for the Oxygen Evolution Reaction (OER)

The exploration of earth-abundant electrocatalysts with high performance for the oxygen evolution reaction (OER) is eminently desirable and remains a significant challenge. The composite of the metal-organic framework (MOF) Ni₁₀Co-BTC (BTC = 1,3,5-benzenetricarboxylate) and the highly conductive carbon material ketjenblack (KB) could be easily obtained from the MOF synthesis in the presence of KB in a one-step solvothermal reaction. The composite and the pristine MOF perform better than commercially available Ni/NiO nanoparticles under the same conditions for the OER. Activation of the nickel-cobalt clusters from the MOF can be seen under the applied anodic potential, which steadily boosts the OER performance. Ni₁₀Co-BTC and Ni₁₀Co-BTC/KB are used as sacrificial agents and undergo structural changes during electrochemical measurements, the stabilized materials show good OER performances.     

A novel pyrrolidinium ionic liquid with 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate anion as a recyclable reaction medium and efficient catalyst for Friedel-Crafts alkylations of indoles with nitroalkenes

A series of pyrrolidinium-based salts with new fluorine-containing anions were synthesized. Different melting points could be obtained by changing the length of the fluoroalkyl chain of the anions. The pyrrolidinium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate ([C₄H₈NH₂][H(CF₂)₄O(CF₂)₂SO₃]) is highly fluid even below room temperature. It can be used both as a recyclable solvent and as an efficient catalyst for Friedel-Crafts alkylations of indoles with nitroalkenes.     

Benzoic Acid: an Efficient and Rapid Catalyst for the Synthesis of α-Hydroxyl(indolyl)ethanones from Indoles

An efficient method for regioselective Friedel-Crafts alkylations of indole using arylglyoxals in the presence of benzoic acid has been discovered. The reactions proceeded smoothly at room temperature under metalfree conditions and generated the corresponding products in good to excellent yields. This methodology has a broad substrate scope and opens up an interesting and attractive avenue for the synthesis of α-hydroxyl(indolyl)-ethanones.     

Synthesis, structural characterization of benzimidazole-functionalized Ni(II) and Hg(II) N-heterocyclic carbene complexes and their applications as efficient catalysts for Friedel-Crafts alkylations

[Ni(L₁)₂](PF₆)₂ (3a, L₁ = 3-(1-ethyl-1H-benzimidazol-2-yl)methyl)-1-((6-methylpyridin-2-yl)methyl)imidazolyl-idene), [Ni(L₂)₂(CH₃CN)](PF₆)₂ (3b, L₂ = 3-(1-ethyl-1H-benzimidazol-2-yl)methyl)-1-((6-methylpyridin-2-yl)-methyl)benzimidazolylidene), and [Hg(L₁)₂(CH₃CN)₂](PF₆)₂ (4) have been successfully prepared and fully characterized by NMR, ESI-MS spectroscopy, and X-ray diffraction analysis. The nickel complexes reveal a square-planar structure with two carbene ligands and benzimidazole groups at the cis configuration. The nickel complex 3b has been proved to be a highly efficient catalyst for Friedel-Crafts alkylation of indoles with β-nitrostyrenes at room temperature in moderate-to-excellent yields. The crystal packing structure of 4 shows that double-stranded 1D supramolecular chains are formed by inter-chain benzimidazole rings and pyridine rings face-to-face π-π stacking interactions.     

Construction of a Stable Lanthanide Metal-Organic Framework as a Luminescent Probe for Rapid Naked-Eye Recognition of Fe3+ and Acetone

Four lanthanide metal-organic frameworks (Ln-MOFs), namely {[Me₂NH₂][LnL]·2H₂O}_n (Ln = Eu 1, Tb 2, Dy 3, Gd 4), have been constructed from a new tetradentate ligand 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid (H₄L). These isostructural Ln-MOFs, crystallizing in the monoclinic P2₁/c space group, feature a 3D structure with 7.5 Å × 9.8 Å channels along the b axis and the point symbol of {4¹⁰.6¹⁴.8⁴} {4⁵.6}₂. The framework shows high air and hydrolytic stability, which can keep stable after exposed to humid air for 30 days or immersed in water for seven days. Four MOFs with different lanthanide ions (Eu³⁺, Tb³⁺, Dy³⁺, and Gd³⁺) ions exhibit red, green, yellow, and blue emissions, respectively. The Tb-MOF emitting bright green luminescence can selectively and rapidly (<40 s) detect Fe³⁺ in aqueous media via a fluorescence quenching effect. The detection shows excellent anti-inference ability toward many other cations and can be easily recognized by naked eyes. In addition, it can also be utilized as a rapid fluorescent sensor to detect acetone solvent as well as acetone vapor. Similar results of sensing experiments were observed from Eu-MOF. The sensing mechanism are further discussed.     

A Polyoxometalate‐Encapsulating Cationic Metal–Organic Framework as a Heterogeneous Catalyst for Desulfurization

A new cationic triazole‐based metal–organic framework encapsulating Keggin‐type polyoxometalates, with the molecular formula [Co(BBPTZ)₃][HPMo₁₂O₄₀]?24 H₂O [compound 1 ; BBPTZ=4,4′‐bis(1,2,4‐triazol‐1‐ylmethyl)biphenyl] is hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The structure of compound 1 contains a non‐interpenetrated 3D CdSO₄ (cds)‐type framework with two types of channels that are interconnected with each other; straight channels that are occupied by the Keggin‐type POM anions, and wavelike channels that contain lattice water molecules. The catalytic activity of compound 1 in the oxidative desulfurization reaction indicates that it is not only an effective and size‐selective heterogeneous catalyst, but it also exhibits distinct structural stability in the catalytic reaction system.     

介孔硅铝分子筛的合成、表征及其作为固体酸催化苯酚与1-辛烯的烷基化反应

以异丙醇铝、硅酸四乙酯和十六烷基三甲基溴化胺为原料,以乙酰丙酮为螯合剂,采用溶胶-凝胶法合成了硅铝比分别为25,50,100和150的介孔硅铝分子筛,并用其催化苯酚与1-辛烯的液相烷基化反应.X射线衍射、N2吸附、高分辨透射电镜及27Al核磁共振光谱表征结果表明,该介孔分子筛具有蠕虫状骨架结构.在160℃时,硅铝比为25的介孔硅铝分子筛催化剂上苯酚可以完全转化为单烷基苯酚.     

Silica Phosphoric Acid (SPA) as a Highly Active,Reusable, Heterogeneous Catalyst for the Synthesis of 2-Amino/Anilino-5-ARYL-1,3,4-Thiadiazine Bromide Derivatives

Silica phosphoric acid has been found to be an efficient catalyst for the synthesis of 2-amino/anilino-5-aryl-1,3,4-thiadiazine bromide derivatives from the reaction of thiosemicarbazide and α-bromoketones in acetonitrile at room temperature. The catalyst can be reused for four times without any significant loss of catalytic activity. The experimental procedure is simple, and the products are obtained in high yield.     

Electrochemical Determination of Aflatoxin B1 (AFB1) Using a Copper-Based Metal-Organic Framework (Cu-MOF) and Gold Nanoparticles (AuNPs) with Exonuclease III (Exo III) Assisted Recycling by Differential Pulse Voltammetry (DPV)

Abstract

A sensitive electrochemical biosensor was designed for determination of aflatoxin B1 (AFB1) using a copper-based metal-organic framework (Cu-MOF), which has strong electrochemical activity and exonuclease III (Exo III)-assisted recycling for dual signal amplification. Hairpin DNA (S1) was immobilized on the electrode. The AFB1 was recognized by aptamer DNA (S2) and complementary DNA (S3) was released. The S3 hybridized with the hairpin S1 to form the Exo III hydrolyzed double-stranded DNA, leaving a partial sequence of hairpin DNA (S1′) on the electrode and releasing S3 for the next cycle of the opening and digestion of hairpin S1. The amplified S1′ then was able to combine with more signal probes. Cu-MOF bond gold nanoparticles (AuNPs) by -NH₂ were immobilized to capture DNA (S4) to obtain Cu-MOF/AuNPs/S4. This signal probe Cu-MOF/AuNPs/S4 was able to hybridize with the electrode and generate an amplified electrochemical signal. Under the optimized conditions, this electrochemical biosensor for AFB1 exhibited a low detection limit of 6.7?×?10^?7?ng/mL at a signal-to-noise equal to 3 and a wide linear range from 10^?6 to 1?ng/mL. The biosensor was also used to analyze AFB1-spiked beer sample with recovery values between 96% and 103%. This method has the potential to become a valuable technology for detecting various toxins by the selection of the appropriate aptamer DNA.     

A Zn(II)-Based Sql Type 2D Coordination Polymer as a Highly Sensitive and Selective Turn-On Fluorescent Probe for Al3+

A luminescent coordination polymer with the overall formula {[Zn(tr₂btd)(bpdc)]∙DMF}_n (where tr₂btd = 4,7-di(1H-1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole; bpdc = 4,4′-biphenyldicarboxylate) was synthesized and characterized by single-crystal and powder X-ray diffraction, thermogravimetric, infrared spectroscopy, and elemental analyses. Luminescent properties of the obtained compound were studied in detail both in the solid state and as a suspension in N,N-dimethylacetamide (DMA). It was found that {[Zn(tr₂btd)(bpdc)]∙DMF}_n exhibits bright turquoise luminescence with excellent quantum efficiency and demonstrates turn-on fluorescence enhancement effect upon soaking in DMA Al³⁺ solution. Fluorescence titration experiments were carried out and the detection limit for Al³⁺ ions was calculated to be 120 nM, which is among the lowest reported values for similar materials. Moreover, compound demonstrated excellent selectivity and reusability, and the mechanism of the response is discussed. These results indicate that {[Zn(tr₂btd)(bpdc)]∙DMF}_n is a promising probe for sensitive fluorescent Al³⁺ detection.     

Nanoscaled Copper Metal–Organic Framework (MOF) Based on Carboxylate Ligands as an Efficient Heterogeneous Catalyst for Aerobic Epoxidation of Olefins and Oxidation of Benzylic and Allylic Alcohols

Aerobic epoxidation of olefins at a mild reaction temperature has been carried out by using nanomorphology of [Cu₃(BTC)₂] (BTC=1,3,5‐benzenetricarboxylate) as a high‐performance catalyst through a simple synthetic strategy. An aromatic carboxylate ligand was employed to furnish a heterogeneous copper catalyst and also serves as the ligand for enhanced catalytic activities in the catalytic reaction. The utilization of a copper metal–organic framework catalyst was further extended to the aerobic oxidation of aromatic alcohols. The shape and size selectivity of the catalyst in olefin epoxidation and alcohol oxidation was investigated. Furthermore, the as‐synthesized copper catalyst can be easily recovered and reused several times without leaching of active species or significant loss of activity.