Elimination of 4‐chlorophenol in aqueous solution by the Novel Pd/MIL‐101(Cr)‐Hydrogen‐Accelerated catalytic fenton system

Excessive consumption of Fe (II) and massive generation of sludge containing Fe (III) from classic Fenton process remains a major obstacle for its poor recycling of Fe (III) to Fe (II). Therefore, the MHACF‐MIL‐101(Cr) system, by introducing H₂, Pd⁰ and MIL‐101(Cr) into Fenton reaction system, was developed at normal temperature and pressure. In this system, the reduction of Fe^III back to Fe^II by solid catalyst Pd/MIL‐101(Cr) for the storage and activation of H₂, was accelerated significantly by above 10‐fold and 5‐fold controlled with the H₂‐MIL‐101(Cr) system and H₂‐Pd⁰ system, respectively. However, the concentration of Fe (II) generated by the reduction of Fe (III) could not be detected with the only input of H₂ and without the addition of MOFs material. In addition, the apparent consumption of Fe (II) in MHACF‐MIL‐101(Cr) system was half of that in classical Fenton system, while more Fe (II) might be reused infinitely in fact. Accordingly, only trace amount of Fe (II) vs H₂O₂ concentration was needed and hydroxyl radicals through the detection of para‐hydroxybenzoic acid (p‐HBA) as the oxidative product of benzoic acid (BA) by·OH could be continuously generated for the effective degradation of 4‐chlorophenol(4‐CP). The effects of initial pH, concentration of 4‐CP, dosage of Fe²⁺, H₂O₂ and Pd/MIL‐101(Cr) catalyst, Pd content and H₂ flow were investigated, combined with systematic controlled experiments. Moreover, the robustness and morphology change of Pd/MIL‐101(Cr) were thoroughly analyzed. This study enables better understanding of the H₂‐mediated Fenton reaction enhanced by Pd/MIL‐101(Cr) and thus, will shed new light on how to accelerate Fe (III)/Fe (II) redox cycle and develop more efficient Fenton system.     

The synthesis of metal–organic framework Al‐MIL‐53‐derived Brønsted acid catalyst and its application in the Mannich reaction

A metal–organic framework Al‐MIL‐53‐NH₂‐derived Brønsted acid catalyst (Al‐MIL‐53‐RSO₃H) has been synthesized employing a post‐synthetic modification strategy under mild conditions. The Al‐MIL‐53‐RSO₃H catalyst was successfully utilized in the nitro‐Mannich reaction taking advantage of its strong Brønsted acidity. Good to excellent yields of Mannich adducts were achieved for a variety of acylimine substrates in the presence of 0.1 mol% Al‐MIL‐53‐RSO₃H. Furthermore, the Al‐MIL‐53‐RSO₃H catalyst can be recycled five times without decreasing the yield and selectivity of Mannich adducts.     

Fabrication of AgI/MIL‐53(Fe) Composites with Enhanced Photocatalytic Activity for Rhodamine B Degradation under Visible Light Irradiation

AgI/MIL‐53(Fe) composites were fabricated through a simple solution method, and their photocatalytic activities on Rhodamine B (RhB) degradation were investigated. The results demonstrated that the introduction of AgI into the MIL‐53(Fe) was beneficial to the enhanced visible light response. Under visible light irradiation, almost 100 % RhB was bleached over AgI/MIL‐53(Fe) composites after 180 min. The promising photocatalytic performance was ascribed to three points: the existence of AgI helped to generate easily the electrons and holes in the composites; an intimate interfacial contact between MIL‐53 (Fe) and AgI offered the path for the charge carries transport; MIL‐53 (Fe) could fast transfer the excited electrons due to its inherent nature. Thus, these results were responsible for the effective inhibition of charge carrier recombination, resulting in an improved photocatalytic activity.     

Effective removal of 2,4,6‐trinitrophenol over hexagonal metal–organic framework NH2‐MIL‐88B(Fe)

A nanostructured organic–inorganic framework, hexagonal NH₂‐MIL‐88B, has been prepared through a facile one‐pot reflux reaction and then it was characterized using various techniques. The as‐prepared sample with high specific surface area (414 m² g^?1) showed excellent adsorption for 2,4,6‐trinitrophenol (TNP) in the liquid phase. Detailed studies of the adsorption kinetics, adsorption mechanism, adsorption isotherm, activation energy and various thermodynamic parameters were conducted. The adsorption mechanism of NH₂‐MIL‐88B for TNP may be ascribed to hydrogen bond interaction, and the complexation between ─OH in TNP and unsaturated Fe(III) on the surface of NH₂‐MIL‐88B. The maximum adsorption capacity of NH₂‐MIL‐88B for TNP based on the Langmuir isotherm was 163.66 mg g^?1. The as‐prepared NH₂‐MIL‐88B adsorbent seems to be a promising material in practice for TNP removal from aqueous solution.     

Enhancing photocatalytic activity of titanium dioxide through incorporation of MIL‐53(Fe) toward degradation of organic dye

Photocatalytic activity of titanium(IV) oxide (TiO₂) can be enhanced through modification of its surface‐active sites. Here, iron(III) carboxylate [MIL‐53[Fe]]‐incorporated TiO₂ (as MIL‐53(Fe)/TiO₂) was prepared using a hydrothermal method. This material was then calcined at 500°C to obtain a MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ photocatalyst. A photocatalytic study of MIL‐53(Fe)/TiO₂ and MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ toward cationic methylene blue (MB) and anionic methyl orange (MO) showed that MIL‐53(Fe)/TiO₂ (0.25 wt%) and MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ (0.75 wt%) resulted the best degree of dye degradation. The MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ (0.75 wt%) composite for instance is capable of degrading almost 100% of 20‐ppm MB and MO, respectively, within 6 hr. Photocatalytic degradation of MB and MO was well fitted to the Langmuir‐Hinshelwood pseudo‐first order kinetics model, which indicates physisorption as the key partway that facilitates dye decomposition on the surface of a photocatalyst under UV‐A irradiation. This study provides new insights into the exploration of MILs/TiO₂ materials for the environmental remediation and pollution control.     

A Convenient Method for the Preparation of 1,5‐Diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones

A simple and eco‐friendly method for the preparation of 1,5‐diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones via the cyclo‐condensation reaction of aldehydes, amines and ethyl pyruvate in the presence of silica supported ferric chloride (SiO₂‐FeCl₃) as reusable heterogeneous catalyst is described. The present methodology offers several advantages such as excellent yields, simple procedure and short reaction times.     

Study on the mechanism of catalytic synthesis of dimethyldichlorosilane by AlCl3/MIL‐53(Al)@γ‐Al2O3

Dimethyldichlorosilane, one of the most consumed organosilicon monomers in the industry, can be prepared in a highly efficient and environmentally friendly synthesis method of disproportionating methylchlorosilanes. However, the internal mechanism of the reaction remains unclear. In this paper, the mechanism catalyzed by AlCl₃/MIL‐53(Al) and AlCl₃/MIL‐53(Al)@γ‐Al₂O₃ catalysts was calculated at B3LYP/6‐311++G(3df, 2pd) level by using the density functional theory (DFT). The results showed that although the two catalysts had similar active structures, the catalytic effects were significantly different. The Lewis acid center on the surface of γ‐Al₂O₃ in the core‐shell catalyst is complementary to the classic Lewis acid AlCl₃ through the spatial superposition effect, which greatly improves the Lewis acid catalytic activity of AlCl₃/MIL‐53(Al)@γ‐Al₂O₃.     

Efficient One‐pot Synthesis of Alkyl 3‐(alkyl)‐4‐methyl‐2‐thioxo‐2,3‐dihydrothiazole‐5‐carboxylates in a Multi Component Reaction

A simple and efficient one‐pot synthesis of alkyl 2‐(alkyl)‐4‐methyl‐2‐thioxo‐2,3‐dihydrothiazole‐5‐carboxylates from the reaction of primary alkylamines and carbon disulfide in the presence of 2‐chloro‐1,3‐dicarbonyl compounds is described. This new protocol has several advantages such as lack of necessity of the catalyst, good yields, mild conditions and short times for reaction.     

Fe3O4/MIL‐101(Fe) nanocomposite as an efficient and recyclable catalyst for Strecker reaction

A highly porous metal‐organic framework, MIL‐101(Fe), was prepared by a solvothermal method in the presence of amino‐modified Fe₃O₄@SiO₂ nanoparticles, in order to achieve Fe₃O₄/MIL‐101(Fe) nanocomposite, which was characterized by XRD, FT‐IR, SEM, TEM, BET, and VSM. This hybrid magnetic nanocomposite was employed as heterogeneous catalyst for α‐amino nitriles synthesis through three‐component condensation reaction of aldehydes (ketones), amines, and trimethylsilyl cyanide in EtOH, at room temperature. The recoverability and reusability was admitted for the heterogeneous magnetic catalyst; no significant reduction of catalytic activity was observed even after five consecutive reaction cycles.     

Facile fabrication of g‐C3N4/MIL‐53(Al) composite with enhanced photocatalytic activities under visible‐light irradiation

A novel visible‐light‐driven g‐C₃N₄/MIL‐53(Al) composite photocatalyst was successfully prepared using a facile stirring method at room temperature. The g‐C₃N₄/MIL‐53(Al) composites were characterized and their effects on the photocatalytic activities for rhodamine B degradation were investigated. The g‐C₃N₄(20 wt%)/MIL‐53(Al) photocatalyst displayed optimal photocatalytic degradation efficiency, which was about five times higher than the photocatalytic activity of pure g‐C₃N₄. The improved photocatalytic performance of the g‐C₃N₄/MIL‐53(Al) photocatalyst was predominantly attributed to the efficient separation of electron–hole pairs and the low charge‐transfer resistance. g‐C₃N₄/MIL‐53(Al) also exhibited excellent stability and reusability. A proposed mechanism for the enhanced photocatalytic activity is also discussed based on the experimental results. Copyright © 2015 John Wiley & Sons, Ltd.     

Metal–organic framework of amine‐MIL‐53(Al) as active and reusable liquid‐phase reaction inductor for multicomponent condensation of Ugi‐type reactions

Metal–organic framework of NH₂‐MIL‐53(Al), with coordinative unsaturated aluminium sites, has been shown to be active in the Groebke–Blackburn–Bienaymé multicomponent coupling reaction based on Ugi‐type amine and aldehyde condensation over isocyanide and then a cyclization process. Interestingly this reaction occurred under solvent‐free conditions with high yield, in which the NH₂‐MIL‐53(Al) could be recovered and reused for five reaction cycles, giving a total turnover number of 455.     

A Ga‐MIL‐53‐type Framework based on 1,4‐Phenylenediacetate Showing Subtle Flexibility

The new MOF Ga‐MIL‐53‐PDA [Ga(OH)(O₂C‐C₈H₈‐CO₂)] · H₂O ( 1 ) was synthesized by a hydrothermal reaction of gallium nitrate, 1,4‐phenylenediacetic acid (H₂PDA) and sodium hydroxide at 100 °C for 24 h. The product is a structural analogue of the archetypical MIL‐53 framework. Its crystal structure was determined by Rietveld refinement of powder X‐ray diffraction (PXRD) data. Furthermore 1,4‐phenylenedipropionic acid (H₂PDP) was employed for further synthesis, which resulted in the dense layered coordination polymers [Ga₂(OH)₄(O₂C‐C₁₀H₁₂‐CO₂)] ( 2 ) and [Ga(OH)(O₂C‐C₁₀H₁₂‐CO₂)] ( 3 ), for which accurate structural models could be established. All compounds were fully characterized and tested regarding potential breathing behavior. Most remarkably, Ga‐MIL‐53‐PDA showed a subtle flexibility upon de/‐rehydration also confirming its porosity, but no drastic structural changes were observed.     

Efficient One‐Pot Synthesis of Bis(4‐hydroxycoumarin)methanes in the Presence of Sulfonic Acid Functionalized Nanoporous Silica (SBA‐Pr‐SO3H)

An efficient and simple method for the synthesis of bis(4‐hydroxycoumarin)methanes has been achieved through a one‐pot condensation of aryl aldehydes and 4‐hydroxycoumarin in the presence of nanoporous solid acid catalyst of SBA‐Pr‐SO₃H with pore size of 6 nm. Excellent yields, short reaction times, reusability of the catalyst and simple workup are advantages of this synthetic procedure.     

Three‐component One‐pot Synthetic Route to Functionalized N‐Phenyl‐ and N,N‐(1,4‐phenylene)‐2‐alkylimino‐2,3‐dihydrothiazoles under Mild,Solvent‐ and Catalyst‐free Conditions

A simple and efficient one‐pot synthesis of alkyl‐2‐(alkylimino)‐4‐methyl‐3‐phenyl‐2,3‐dihydrothiazole‐5‐carboxylate and dialkyl 3,3′‐(1,4‐phenylene)‐bis‐[2‐(alkylimino)‐4‐methyl‐2,3‐dihydrothiazole‐5‐carboxylate] derivatives from the reaction of phenylisothiocyanate (and also 1,4‐phenylene diisothiocyanate) and primary alkylamines in the presence of 2‐chloro‐1,3‐dicarbonyl compounds is described. This new protocol has several advantages such as lack of necessity of the catalyst and solvent, good yields,mild conditions and short times for reaction.     

Coordination Polymer Nanobamboos of {FexIn1−x}‐MIL‐88B: Induced Formation of a Virtual In‐MIL‐88B

A precise fabrication of nanobamboo structures made from hybrid coordination polymers of the type {Fe_xIn_1?x}‐MIL‐88B is demonstrated. The compositions of the hybrid coordination polymer nanobamboos of {Fe_xIn_1?x}‐MIL‐88B (x=0.06, 0.19, or 0.75) are regulated by altering the amount of metal ions used in the reactions. Interestingly, the formation of a virtual In‐MIL‐88B (precise structure, {Fe_0.06In_0.94}‐MIL‐88B), which cannot be created in a typical reaction, is induced by the assistance of a Fe‐MIL‐88B structure. The a and c cell parameters of {Fe_0.06In_0.94}‐MIL‐88B are calculated at 10.95 and 19.86 Å, respectively. These values of {Fe_0.06In_0.94}‐MIL‐88B are larger than those of pure Fe‐MIL‐88B owing to the large ionic size of In³⁺ within the framework.     

Design and Application of a Non‐enzymatic Sensor Based on Metal‐organic Frameworks for the Simultaneous Determination of Carbofuran and Carbaryl in Fruits and Vegetables

A novel, stable and sensitive non‐enzymatic sensor was developed with metal‐organic frameworks (MOFs) that have attracted great attention in electrochemical sensors applications in recent years. The pore structures of MIL (Fe)‐101 and MIL (Fe)‐53 are the families of MOFs that were constructed via a simple solvothermal procedure. The 35MIL‐101(Fe)‐reduced graphene oxide nanocomposite has been used for modification of glassy carbon electrode for the determination of carbofuran (CBF) and carbaryl (CBR). The porosity of the composites increased the voltammetric responses significantly for CBF and CBR in a mixed solution that makes the simultaneous determination of both carbamate pesticides possible. Characterization of MIL (Fe)‐101 and MIL (Fe)‐53 were performed with FT‐IR, XRD, BET and SEM. Finally, the introduced sensor under the optimal conditions showed low detection limits of 1.2 and 0.5 nM within the linear ranges of 5.0–200.0 nM and 1.0–300.0 nM for CBF and CBR, respectively. The non‐enzymatic sensor was successfully used to monitoring of carbamates residue in vegetable and fruit samples.     

Three‐component solventless Strecker synthesis of α‐aminonitriles catalysed by a renewable sulfonated nanoporous carbon catalyst (CMK‐5‐SO3H)

The one‐pot three‐component synthesis of a variety of α‐aminonitriles has been studied using a catalytic amount of a sulfonic acid‐functionalized ordered nanoporous carbon catalyst, CMK‐5‐SO₃H, at room temperature under solvent‐free reaction conditions. The heterogeneous catalyst could be readily isolated from the reaction mixture and reused at least ten times without significant loss in activity. A clean, rapid and simple method for the preparation of α‐aminonitriles using the recoverable CMK‐5‐SO3H catalyst is described.     

Magnetic iron(III)‐based framework composites for the magnetic solid‐phase extraction of fungicides from environmental water samples

We adopted a facile hydrofluoric acid‐free hydro‐/solvothermal method for the preparation of four magnetic iron(III)‐based framework composites (MIL‐101@Fe₃O₄‐COOH, MIL‐101‐NH₂@Fe₃O₄‐COOH, MIL‐53@Fe₃O₄‐COOH, and MIL‐53‐NH₂@Fe₃O₄‐COOH). The obtained four magnetic iron(III)‐based framework composites were applied to magnetic separation and enrichment of the fungicides (prochloraz, myclobutanil, tebuconazole, and iprodione) from environmental samples before high‐performance liquid chromatographic analysis. MIL‐101‐NH₂@Fe₃O₄‐COOH showed more remarkable pre‐concentration ability for the fungicides as compared to the other three magnetic iron(III)‐based framework composites. The extraction parameters affecting enrichment efficiency including extraction time, sample pH, elution time, and the desorption solvent were investigated and optimized. Under the optimized conditions, the standard curve of correlation coefficients were all above 0.991, the limits of detection were 0.04–0.4 μg/L, and the relative standard deviations were below 10.2%. The recoveries of two real water samples ranged from 71.1–99.1% at the low spiking level (30 μg/L). Therefore, the MIL‐101‐NH₂@Fe₃O₄‐COOH composites are attractive for the rapid and efficient extraction of fungicides from environmental water samples.     

Synthesis of “Clickable” Nano Metal‐organic Framework by Generic Postsynthetic Modification Route

Organic azides have been somewhat popularized due to their pivotal role in the emerging field of “click chemistry”. A simple approach has been used for the synthesis of uniform nano Fe‐MIL‐88B‐NH₂, and a generic postsynthetic modification route has been developed for the synthesis of azide‐modified nano Fe‐MIL‐88B‐N₃. The approach also has been used to synthesize the azide‐modified IRMOF‐3(‐N₃). These new azide‐modified Fe‐MIL‐88B‐N₃ nanocrystals hold promising potential for the applications in the fields of “click chemistry”, nanotechnology devices and nano composite membranes.     

N,N′‐Bis(arylmethylidene)arylmethanediamines: Suitable Precursors for the Synthesis of 1‐Pyrroline Derivatives

A simple and appropriate procedure for the synthesis of 4,5‐dihydro‐5‐hydroxy‐3H‐pyrrole‐3,3‐dicarbonitrile derivatives is reported. The advantages of this method are one‐pot conditions, high yield of products, short reaction times, and no need of metal catalyst. The structures are confirmed spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this reaction is proposed (Scheme 2).