One-pot synthesis of highly substituted pyrroles using nano copper oxide as an effective heterogeneous nanocatalyst

A convenient one-pot four-component reaction of aromatic aldehydes, β-keto esters and nitromethane in the presence an amine and 10 mol% CuO nanoparticles for the synthesis of highly substituted pyrroles is described. Excellent yields, easily available and less expensive catalyst and easy work-up are the key features of the present method. The NMR spectrum was coupled with quantum chemical calculations in DFT approach using the hybrid B3LYP exchange-correlation functional to confirm the structures of (1-benzyl-4-(4-chlorophenyl)-2-methyl-1H-pyrrol-3-yl)(phenyl)methanone 14 and 1-(1-benzyl-4-(4-chlorophenyl)-2-phenyl-1H-pyrrol-3-yl)ethanone 14′.     

Magnetic methylene-based mesoporous organosilica composite-supported IL/Pd: a powerful and highly recoverable catalyst for oxidative coupling of phenols and naphthols

A novel magnetic methylene-based mesoporous organosilica composite-supported IL/Pd complex (Fe₃O₄@MePMO-IL/Pd) was synthesized and characterized, and its catalytic performance was investigated. The preparation of the Fe₃O₄@MePMO composite was achieved through coating of Fe₃O₄ nanoparticles with a mixture of tetramethoxysilane, bis(triethoxysilyl)methane, and (3-chloropropyl)-trimethoxysilane in the presence of cetyltrimethylammonium bromide surfactant. The Fe₃O₄@MePMO was then modified with alkyl imidazolium ionic liquid and palladium species to deliver the Fe₃O₄@MePMO-IL/Pd nanocatalyst. This catalyst was characterized using Fourier transform infrared, thermal gravimetric, wide-angle powder X-ray diffraction, low-angle powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, energy-dispersive X-ray, and nitrogen adsorption–desorption analyses. The Fe₃O₄@MePMO-IL/Pd was effectively used as a highly recoverable and durable catalyst for the selective oxidative coupling of phenols and 2-naphthols under aerobic conditions.     

Fabrication of carboxymethylated cellulose fibers supporting Ag NPs@MOF‐199s nanocatalysts for catalytic reduction of 4‐nitrophenol

In this work, we prepared high‐performance and recyclable nanocatalysts that consist of small and well‐dispersed silver nanoparticles (Ag NPs) immobilized onto Cu‐ based metal–organic framework (MOF‐199 s) supported by carboxymethylated cellulose fibers (CCFs). The as‐prepared green nanohybrid catalysts, namely Ag NPs@ MOF‐199 s/CCFs, were characterized using SEM, TEM, XRD and FT‐IR techniques. The catalytic performances showed that Ag NPs@ MOF‐199 s/CCFs catalysts exhibited a very high catalytic efficiency towards the reduction of 4‐nitrophenol to 4‐aminophenol. The enhanced catalytic performances are attributed to the improved dispersity, small particles of Ag NPs stabilized by the MOF‐199 s, and the porous catalyst structures. The introduction of cellulose fiber further facilitates the reuse and sustainability of the nanohybrid catalysts, showing a stable and high reusability (more than 91% of catalytic activity) even after five runs.     

L-lysine-Pd Complex Supported on Fe3O4 MNPs: a novel recoverable magnetic nanocatalyst for Suzuki C-C Cross-Coupling reaction

In this work, L-lysine-Pd Complex, immobilized onto the surface of Fe₃O₄ MNPs, was successfully prepared via simple and inexpensive procedure. The prepared nanocatalyst was considered as a robust and clean nano-reactor catalyst for the Suzuki and Heck C-C Cross-Coupling reactions in water as the green condition. This eco-friendly heterogeneous catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP), X-ray mapping, BET, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. The use of a green medium, easy separation and workup, excellent reusability of the nanocatalyst and short reaction time are some outstanding advantages of this method.     

甲烷氧化偶联锂/氧化镁催化剂和纳米催化剂

The Li/MgO catalyst and nanocatalyst were prepared by the incipient wetness impregnation and sol-gel method, respectively. The catalytic performance of the Li/MgO catalyst and nanocatalyst on oxidative coupling of methane was compared. The catalysts prepared in two ways were characterized by X-ray powder diffraction, Brunauer-Emmett-Teller surface and transmission electron microscope. The catalyst was tested at temperature of 973-1073 K with constant total pressure of 101 kPa. Experimental results showed that Li/MgO nanocatalyst in the oxidative coupling of methane would result in higher conversion of methane, higher selectivity, and higher yield of main products (ethane and ethylene) compared to ordinary catalyst. The results show the improved influence of nanoscale Li/MgO catalyst performance on oxidative coupling of methane.     

Magnetic Co‐doped NiFe2O4 Nanocomposite: A Heterogeneous and Recyclable Catalyst for the One‐Pot Synthesis of Benzimidazoles,Benzoxazoles and Benzothiazoles under Solvent‐Free Conditions

A simple and efficient procedure for the synthesis of benzimidazoles, benzoxazoles, and benzothiazoles via the condensation of o‐phenylenediamine, o‐aminophenol, and o‐aminothiophenol with various benzaldehydes by using magnetic Co‐doped NiFe₂O₄ nanoparticles has been developed. This nanocatalyst has advantages such as excellent product yields, solvent‐free conditions, and very short reaction times. After any experiment, the magnetic nanocatalyst could be easily separated with the aid of an external magnet and reused at least four times without any loss of its catalytic performance.     

氮掺杂纳米碳块的制备及氧还原的高电化学催化活性

面对全球化的能源危机,燃料电池由于其高效性和可重复使用性成为越来越具有潜力的能量转化设备.阴极发生的氧气还原反应对于燃料电池的性能十分重要,寻找高效的氧还原催化剂在很大程度上可以提高燃料电池的性能.传统的氧还原催化剂是贵金属铂,但是铂的价格十分高,较差的稳定性和选择性限制了它的商业化应用,因此找到一种廉价高效的非贵金属氧还原催化剂来代替铂基催化剂成为目前的研究热点.我们最近发现将纯的三羟甲基氨基甲烷置于管式炉中在800°C下真空烧制2 h,可以简单快捷地得到一种含 N量为4.11%的纳米碳块(标记为 NCNBs-800),该材料可用于催化电化学氧气还原反应.同样情况下在700和900°C下合成的材料标记为 NCNBs-700和 NCNBs-900.采用傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、X射线衍射(XRD)和电化学旋转圆盘方法与技术对催化剂的成分、形貌和电催化性能进行了表征. SEM表明 NCNBs-800为直径为60 nm的碳块,用 FTIR手段表征了 NCNBs-800的结构变化,三羟甲基氨基甲烷中的–OH和–NH2在高温下发生消去反应,形成了饱和度不同的 C–N键和 C–C键.这些饱和度不同的 N原子和 C原子增加了材料的缺陷结构和活性位点,进一步促进了氧还原反应的催化性能.采用 XPS分析了 NCNBs-800表面的元素,通过对 N 1s进行分峰拟合,发现 NCNBs-800含有能促进氧还原性能的吡啶-N和吡咯-N,特别是吡啶-N,它吸电子的能力很强,从而导致与它邻近的 C原子表面具有一定的正电荷,这些正电荷促进了氧气的吸附和还原,为氧气还原反应提供活性位点,促进氧气还原反应的发生. XRD结果表明,三羟甲基氨基甲烷热解前后的 XRD谱图有明显变化,热解后的三羟甲基氨基甲烷呈现两个宽峰,代表着杂化碳的存在. NCNBs-800的衍射峰强度比 NCNBs-700以及 NCNBs-900大,但是宽度则比 NCNBs-700以及 NCNBs-900小,这表明800°C有利于材料的石墨烯化及碳化过程.电化学阻抗可以表明修饰电极的表面性质,阻抗图中高频处半圆的直径大小代表电子转移阻力,低频处的线性部分代表扩散过程.阻抗数据表明, NCNBs-800的电荷转移电阻可与 Pt/C催化剂相比,但是比裸露的玻碳电极小.这表明 NCNBs-800有较好的导电性和电化学性质. CV曲线表明 NCNBs-800氧还原的起始电位是-0.05 V (vs Ag/AgCl),氧气的还原电位是0.20 V (vs Ag/AgCl),说明 NCNBs-800具有良好的电化学催化性能.旋转环盘电极仪测得的氧还原极化曲线表明,在-0.3 to-0.8 V下的 NCNBs-800氧还原的电子转移数为3.4,过氧化氢产率为52%-35%,表明 NCNBs-800呈现一个提高的四电子过程.稳定性对于燃料电池氧气还原反应也是一个十分重要的性能,通过计时电流技术在电压为-0.2 V下对 NCNBs-800与 Pt/C进行了稳定性测试.结果表明,在2500 s之后 NCNBs-800相对于它的最初催化活性损失为17.56%,而 Pt/C损失了30.71%,从而说明 NCNBs-800的稳定性优于 Pt/C.总之,我们通过一步热解的简易技术制备了一种氮掺杂纳米碳材料,该碳材料具有廉价、高效和容易制备等特点,具有良好的电化学催化性能,有望在燃料电池氧化还原反应中得到大规模应用.     

Air-Stable Fe3O4@SiO2-EDTA-Ni(0) as an Efficient Recyclable Magnetic Nanocatalyst for Effective Suzuki-Miyaura and Heck Cross-Coupling via Aryl Sulfamates and Carbamates

The synthesis of inexpensive and novel air-stable Ni(0) nanoparticles immobilized on the EDTA-modified Fe₃O₄@SiO₂ nanocatalyst was investigated in Suzuki-Miyaura and Heck cross-coupling reactions. This catalytic system displayed a greatly improved substrate scope for the carbon–carbon bond formations starting from a wide range of green and economical electrophiles aryl and heteroaryl carbamates and sulfamates via highly efficient method under mild, operationally simple reaction conditions. The synthesized heterogeneous catalyst was also fully characterized by FT-IR, TEM, XRD, DLS, FE-SEM, UV–Vis, EDX, XPS, TGA, NMR, VSM, ICP and elemental analysis techniques. The heterogeneous magnetic nanocatalyst can easily be recovered by an external magnetic field and reused for the next reactions for at least seven times with negligible leaching of catalyst and no substantial decrement in the activity. All these highlights have made the present protocol an interesting, simple and environmentally benign process with low catalyst loading and easy manipulations.     

Facile and eco-benign synthesis of a novel MnFe2O4@SiO2@Au magnetic nanocomposite with antibacterial properties and enhanced photocatalytic activity under UV and visible-light irradiations

The purpose of this research is to prepare novel, inexpensive, eco-friendly and efficient magnetic nanocomposites for degradation of pollutant from wastewater and their potential antibacterial activity. To reach this goal, we have synthesized magnetic MnFe₂O₄@SiO₂@Au (MnFe@Si@Au) nanocomposites through ultrasound assisted co-precipitation technique in presence of carbohydrate and Crataegus fruits extract, for the first time. The influence of capping agents including sucrose, glucose, PVA and reducing agents such as C. microphylla and C. pentagyna on the morphology, size, purity, photocatalytic and antibacterial behavior of magnetic nanocomposites were investigated. The FT-IR, XRD, VSM, EDS, FE-SEM, TEM and BET analysis were performed to confirm the formation of magnetic nanocomposites. MnFe@Si@Au nanocomposites have shown promising potential in degradation of organic contaminants including rhodamine b (RhB), 2-naphthol (2-NPH), methyl violet (MV), erythrosine (ER) and eriochrome black T (EBT) under both radiation conditions. The results show that degradation of the anionic contaminants is more than cationic contaminants under UV and visible irradiations. As well as, these synthesized spherical MnFe@Si@Au nanocomposites show excellent antibacterial activities against P. aeruginosa, K. pneumoniae and P. mirabilis bacteria. In addition to the features mentioned, another prominent feature of this nanocatalyst is retaining their photocatalytic activity after five cycles of utilization.     

Immobilized manganese porphyrin on functionalized magnetic nanoparticles via axial ligation: efficient and recyclable nanocatalyst for oxidation reactions

Magnetic nanoparticles (MNPs), Fe₃O₄@SiO₂, have been prepared and functionalized by 3-(chloropropyl)trimethoxysilane and then by imidazole to synthesize Fe₃O₄@SiO₂-Im. The functionalized Fe₃O₄ nanoparticles were used as a support to anchor manganese porphyrin via axial ligation. The prepared catalyst was characterized by elemental analysis, FT-IR spectroscopy, X-ray powder diffraction, UV–vis spectroscopy, and scanning electron microscopy. Application of immobilized manganese porphyrin as a heterogeneous catalyst in oxidation of alkenes and sulfides was explored. To find suitable reaction conditions, effect of different parameters such as solvent and temperature on immobilization process and also various reaction parameters (oxidant, solvent, and time) on oxidation reactions has been investigated. The results showed that the immobilized Mn-porphyrin on functionalized MNPs is an efficient and reusable catalyst for oxidation of substrates.