Accelerated FeIII/FeII redox cycle of Fenton reaction system using Pd/NH2-MIL-101(Cr) and hydrogen

In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH₂-MIL-101(Cr) was constructed based on H₂ and Pd/NH₂-MIL-101(Cr). The improved system would result in an accelerated reduction in Fe^III, and provide a continuous and fast degradation efficiency of the 10 mg L^-1 4-chlorophenol which was the model contaminant by using only trace level Fe^II. The activity of Pd/NH₂-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH₂-MIL-101(Cr).     

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.     

Highly efficient protection of alcohols and phenols catalysed by tin porphyrin supported on MIL‐101

The catalytic activity of 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], supported on chloromethylated MIL‐101, was investigated in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) and also their tetrahydropyranylation with 3,4‐dihydro‐2H‐pyran. Excellent yields, mild reaction conditions, short reaction times and reusability of the catalyst without significant decrease in its initial activity are noteworthy advantages of this supported catalyst. Copyright © 2015 John Wiley & Sons, Ltd.     

Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

A heterogeneous catalyst was synthesized by encapsulation of a Keggin‐type heteropolytungstate, potassium dodecatungstocobaltate trihydrate, K₅[CoW₁₂O₄₀]·(Co‐POM), into chromium(III) terephthalate (MIL‐101). Encapsulation was achieved via a ‘build bottle around ship’ strategy in aqueous media, following a hydrothermal method. The structure of the resulting crystalline solid was characterized using X‐ray diffraction, correlated with Fourier transform infrared and UV–visible spectroscopy. The metal content was analysed using optical emission spectroscopy. Transmission electron microscopy was used to measure particle size and N₂ adsorption in a Brunauer–Emmett–Teller instrument to characterize the specific surface area. The catalytic activity was investigated using methanolysis of epoxides under mild conditions as a test reaction. The turnover frequency of the heterogeneous Co‐POM@MIL‐101 catalyst was more than 20 times higher than that of the homogeneous Co‐POM catalyst. The Co‐POM@MIL‐101 catalyst was reused several times with negligible leaching of Co‐POM and with no considerable loss of its initial efficiency. The simplicity of preparation, extraordinary stability and high reactivity make Co‐POM@MIL‐101 an exceptional catalytic matrix that is easily separable from reaction media.     

Metal–organic framework MIL‐125(Ti) for efficient adsorptive removal of Rhodamine B from aqueous solution

A metal–organic framework material, MIL‐125(Ti), was solvothermally prepared and characterized using X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and surface area measurements. MIL‐125(Ti) was then used as an adsorbent for Rhodamine B (RhB) removal in aqueous solution. The adsorption kinetics, adsorption mechanism, adsorption isotherm, activation energy and various thermodynamic parameters were studied in detail. The maximum adsorption capacity of MIL‐125(Ti) for RhB was 59.92 mg g^?1. MIL‐125(Ti) appears to be a promising material for RhB adsorption from aqueous solutions. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Preparation of BiVO4/MIL‐125(Ti) composite with enhanced visible‐light photocatalytic activity for dye degradation

Because of their desired features, including very specific surface areas and designable framework architecture together with their possibility to be functionalized, Metal Framework (MOF) is a promising platform for supporting varied materials in respect of catalytic applications in water treatment. In this work, a novel visible‐light‐responsive photocatalyst that comprised BiVO₄ together with MIL‐125(Ti), was synthesized by a two‐step hydrothermal approach. The characterization of as‐obtained samples as performed by X‐ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscope, X‐ray photoelectron spectroscopy and ultraviolet‐visible diffuse reflection spectra. Rhodamine B was selected being a target for the evaluation of the photocatalytic function of as‐developed photocatalyst. The photocatalytic reaction parameters, for example, the content of BiVO₄ as well as initial concentration of Rhodamine B was researched. The composite photocatalyst possessing Bi:Ti molar ratio of 3:2 brought to light the fact that the greatest photocatalytic activity had the ability to degrade 92% of Rhodamine B in 180 min. In addition to that, the BiVO₄/MIL‐125(Ti) composite could keep its photocatalytic activity during the recycling test. The phenomenon of disintegration of the photo‐generated charges in the BiVO₄/MIL‐125(Ti) composite was brought to discussion as well.     

五乙烯六胺改性金属有机骨架材料MIL-101(Cr)对CO_2的吸附性能

采用溶剂热法合成金属有机骨架材料MIL-101(Cr),用回流法将五乙烯六胺(PEHA)负载到MIL-101(Cr)孔道中的不饱和金属位点上,使用扫描电镜、粉末X射线衍射、氮气物理吸附、元素分析和傅里叶变换红外光谱等表征手段考察材料的结构和形貌,测试氨基改性前后的MIL-101(Cr)在25℃、不同压力下对CO_2的吸附效果。结果表明,负载0.24 m L五乙烯六胺后的MIL-101(Cr)对CO_2的吸附效果最好,在25℃、常压下对CO_2的饱和吸附量可达58.944 mg/g,相比未负载五乙烯六胺的MIL-101(Cr)吸附量(CO_2饱和吸附量为44.208 mg/g)增加了33%。随着吸附压力的增加,MIL-101(Cr)和0.24PEHAM IL-101(Cr)对CO_2的饱和吸附量逐渐增加,当吸附压力为1.1 MPa时,两者的吸附量分别为1 147.59和1 256.74 mg/g,表明该类材料在高压下对CO_2有着良好的吸附效果。     

Development and validation of a LC method for the separation and determination of the anticancer‐active FeIII(4‐methoxy‐salophene) using the new second‐generation monolith

LC method with the newly introduced second‐generation monolithic silica RP‐18e column has been developed for the separation of Fe^III(salophene) and four methoxy‐substituted Fe^III(salophene) complexes. The method has been validated for the quantitation of Fe^III(4‐OMe‐salophene), a highly active anticancer substance in vitro, bound to serum albumin. Our routinely used high‐resolution continuum‐source atomic absorption spectroscopy method based on the determination of the central iron atom was unsuitable in this case because serum originally contains significant amounts of iron as revealed by a blank sample of serum albumin. The developed LC method depends on detecting the whole complex rather than the bound iron. Two morphologically different first‐ and second‐generation HPLC monolithic columns have been compared for this purpose. The newly introduced second‐generation monolithic silica column Chromolith® HighResolution RP‐18e column (100 × 4.6 mm, Merck) separated the mixture successful within 13 min. A mobile phase consisting of 25 mM phosphate buffer pH 3/methanol (60:40, v/v) was used at a flow rate of 1 mL/min. The dynamic linear working range of the calibration curve for Fe^III(4‐OMe‐salophene) was found to be between 1 and 200 μg/mL. Detection and quantitation limits were 0.3 and 1 μg/mL, respectively.     

Development of a new catalytic and sustainable methodology for the synthesis of benzodiazepine triazole scaffold using magnetically separable CuFe2O4@MIL-101(Cr) nano-catalyst in aqueous medium

Magnetically retrieval CuFe₂O₄@MIL-101(Cr) metal–organic framework was successfully prepared from easily available starting materials and characterized using various spectroscopic and analytical techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, elemental mapping, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, vibrating sample magnetometer, and inductively coupled plasma optical emission spectroscopy. The catalyst was then used in the synthesis of benzodiazepines containing a triazole moiety in water. The advantages of this protocol include high yields, reusability of the catalyst, and gram-scale synthesis.     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上, 制备了Pt/MIL-101(Cr)催化剂, 并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明, Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0wt%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能, 在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上,制备了Pt/MIL-101(Cr)催化剂,并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明,Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能,在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Decomposition of poly(4‐hydroxystyrene sulfone) in alkaline aqueous solutions

It was confirmed by ¹H NMR measurements that poly(4‐hydroxystyrene sulfone) (PHOSS) was decomposed in dissolving in a deuterium oxide solution of sodium deuteroxide to give trans‐2‐(4‐hydroxyphenyl)ethenesulfinic acid (HESA) and 4‐hydroxystyrene (HOSt) quantitatively. HESA and HOSt were formed in the mole ratio of about 2:3. The amount of each product was almost independent of the alkaline concentration ranging from 1 to 12 w/v %. The mole ratio of monomeric units of decomposed PHOSS to NaOD was estimated to be 0.64. A possible decomposition mechanism was discussed. The initiation reaction was the abstraction of a methylene proton anti to a sulfonyl group by alkali, followed by the main chain scission of the polymer. The resonance structure stabilizing a terminal phenolate anion possibly enhanced the elimination of HESA, so that it was produced in quantity comparable to HOSt. The decomposition of PHOSS in alkaline aqueous solutions was a conformation‐determined polymer degradation following Hofmann's rule. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2760–2766, 2000     

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.     

Aminated metal-organic framework (NH2-MIL-101(Cr)) incorporated polyvinylidene (PVDF) hybrid membranes: Synthesis and application in efficient removal of Congo red from aqueous solution

The efficient treatment of wastewater containing organic dyes generated in diverse industrial processes has become more crucial owing to increasing environmental concerns. In this paper, we incorporated the aminated functional NH₂-MIL-101(Cr) into the porous polyvinylidene fluoride (PVDF) to fabricate the MOFs/polymer hybrid membranes, which combined the surface activity of MOFs and the membrane's filtration plus the adsorption process, and can be used in the high-efficient removal of congo red (CR) from aqueous solution. Two synthesis strategies were employed, and both of which are useful in fabricating the NH₂-MIL-101(Cr)@PVDF hybrid membranes. The NH₂-MIL-101(Cr) particles are mainly incorporated into the pores of PVDF, and thus enhance the hydrophilicity, water flux as well as porosity of the hybrid membranes. In the adsorption experiments, the influences of various conditions including the solution pH, adsorption time, adsorption isotherms, reusability, and the filtration performances were investigated systematically, and all the hybrid membranes show evidently improved adsorption performances compared to original PVDF films. The adsorption thermal and dynamics analyses indicate that the adsorption process is mainly featured in Langmuir monolayer adsorption and chemical adsorption. The hydrogen bonding at the interface of CR/NH₂-MIL-101(Cr) is responsible for the selective adsorption of CR. The excellent reusability and the dynamic adsorption performances determine the potential applications of MOF-based hybrid membranes in the membrane separation of CR from practical waste water.     

Synthesis of Some Quinazoline‐2(1H),4(3H)‐dione Derivatives

Several quinazoline‐2(1H),4(3H)‐dione derivatives were synthesized from pyrimidine‐2(1H),4(3H)‐dione derivative.     

Metal–organic framework derived Pd/ZrO2@CN as a stable catalyst for the catalytic hydrogenation of 2,3,5‐trimethylbenzoquinone

Metal–organic frameworks (MOFs) have recently been identified as versatile sacrificing templates to construct functional nanomaterials for heterogeneous catalysis. Herein, we report a thermal transformation strategy to directly fabricate metal Pd nanoclusters inlaid within a ZrO₂@nitrogen‐doped porous carbon (Pd/ZrO₂@CN) composite using Pd@NH₂‐UiO‐66(Zr) as a precursor that was pre‐synthesized by a one‐pot hydrothermal method. The developed Pd/ZrO₂@CN as a robust catalyst delivered remarkable stability and activity to the catalytic hydrogenation of 2,3,5‐trimethylbenzoquinone (TMBQ) to 2,3,5‐trimethylhydroquinone (TMHQ), a key reaction involved in vitamin E production. The hydrogenation was carried out at 110 °C with 1.0 MPa H₂, and it resulted in 98% TMHQ yield as the sole product over five consecutive cycles, outperforming the analogue Pd/ZrO₂@C without nitrogen doping templated from Pd@UiO‐66(Zr). The excellent catalytic properties of Pd/ZrO₂@CN likely originated from the highly stable ultrafine Pd nanoclusters inlaid within ZrO₂@CN matrix on account of the strong interaction between N and Pd, as well as on the Lewis acidity of ZrO₂, which was beneficial to the hydrogenation.     

MIL‐53(Fe) Metal–Organic Frameworks (MOFs) as an Efficient and Reusable Catalyst for the One‐Pot Four‐Component Synthesis of Pyrano[2,3‐c]‐pyrazoles

A novel and simple approach for the efficient and rapid synthesis of pyrano[2,3‐c]‐pyrazoleshas been accomplished via the four‐component condensation reaction of malononitrile, hydrazine hydrate, ethyl acetoacetate, and substituted aldehydes using MIL‐53(Fe) metal–organic framework (MOF) as a catalyst in ethanol at room temperature. Recycling studies have shown that the MIL‐53(Fe) can be readily recovered and reused six times without significant loss of its activity. The present protocol offers the advantages including short reaction times, simple workup, high yields, elimination of toxic solvents, no chromatographic purification and recoverability of the catalyst. Also, the catalyst was fully characterized by SEM, EDX, FT‐IR, XRD, TGA and TEM analysis.     

Ring Opening of 2‐(Benzylamino)‐2H‐1,4‐benzoxazin‐3(4H)‐ones and 2‐Bromo‐2H‐1,4‐benzoxazin‐3(4H)‐ones

Substituted 2‐(benzylamino)‐2H‐1,4‐benzoxazin‐3(4H)‐ones are unstable under alkaline and acidic conditions, undergoing opening of the benzoxazinone ring. 2‐Bromo‐2H‐1,4‐benzoxazin‐3(4H)‐ones show similar degradation under alkaline conditions, while replacement of Br at C(2) to give 2‐hydroxy‐2H‐1,4‐benzoxazin‐3(4H)‐ones was observed only under mild alkaline conditions. Mechanisms of ring opening and degradation to 2‐aminophenol derivatives are proposed.     

Synthesis of nanoscale titania embedded in MIL‐101 for the adsorption and degradation of volatile pollutants with thermal desorption gas chromatography and mass spectrometry detection

Nanoscale anatase titania was embedded within the porous chromium terephthalate MIL‐101 under low‐temperature hydrothermal treatment. The metal–organic framework shell acting as host matrix can effectively prevent the titania nanoparticles from aggregating and enable a good dispersion of these nanoparticles. The X‐ray diffraction spectra, transmission electron micrography and X‐ray photoelectron spectra clearly showed successful impregnation of the nano‐sized anatase titania within the body of MIL‐101. The resulting TiO₂/MIL‐101 nanocomposite was considered as bifunctional material with abundant adsorptive domains and catalytic domains, and was packed in a quartz tube as a convenient trapping and photocatalytic reactor for hazardous volatile pollutants. The composite showed great potential for adsorptive and photocatalytic degradation of these volatile pollutants, such as formaldehyde and o‐xylene, which were online monitored by thermal desorption gas chromatography with mass spectrometric detection.