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991.
A Hexagonal Covalent Porphyrin Framework as an Efficient Support for Gold Nanoparticles toward Catalytic Reduction of 4‐Nitrophenol 下载免费PDF全文
Zheng‐Dong Ding Yu‐Xia Wang Sai‐Fei Xi Prof. Dr. Yunxing Li Prof. Dr. Zaijun Li Prof. Dr. Xuehong Ren Prof. Dr. Zhi‐Guo Gu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):17029-17036
A hexagonal porphyrin‐based porous organic polymer, namely, CPF‐1, was constructed by 3+2 ketoenamine condensation of the C2‐symmetric porphyrin diamine 5,15‐bis(4‐aminophenyl)‐10,20‐diphenylporphyrin and 1,3,5‐triformylphloroglucinol. This material exhibits permanent porosity and excellent thermal and chemical stability. CPF‐1 can be employed as a superior supporting substrate to immobilize Au nanoparticles (NPs) as a result of the strong interactions between Au NPs and the CPF support. An Au@CPF‐1 hybrid was synthesized by an interfacial solution infiltration method with NaBH4 as reducing agent. Au NPs (5 nm) grew on CPF‐1 and were distributed without aggregation. Moreover, Au@CPF‐1 exhibits superior catalytic activity compared to many other reported Au‐based catalysts for the reduction of 4‐nitrophenol in the presence of NaBH4. In addition, Au@CPF‐1 has excellent stability and recyclability, and it can be reused for three successive reaction cycles without loss of activity. The dense distribution of phenyl rings on the channel walls of the CPF support can reasonably be regarded as the active sites that adsorb the 4‐nitrophenol molecule through hydrogen‐bonding and C?H ??? π interactions, as was confirmed by the X‐ray structure of model compound DAPP‐Benz. 相似文献
992.
价廉易得的L-亮氨酸先以苄基同时保护氨基及羧基得(S)-2-(二苄胺基)-4-甲基戊酸苄酯,进而在碱性条件下与乙腈发生亲核取代反应得(S)-4-(二苄胺基)-6-甲基-3-氧代庚腈,再经硼氢化钠选择性还原羰基得(3S,4S)-4-(二苄胺基)-3-羟基-6-甲基庚腈,用双氧水氧化得(3S,4S)-4-(二苄胺基)-3-羟基-6-甲基庚酸,最后在Pd(OH)2/C-H2作用下脱掉苄基得到(3S,4S)-4-氨基-3-羟基-6-甲基庚酸,即(3S,4S)-statine。整个合成路线总产率为33.6%。 相似文献
993.
994.
995.
Chen Yang Ying Chen Dan Liu Jinfeng Wang Cheng Chen Jiemin Wang Ye Fan Shaoming Huang Weiwei Lei 《Frontiers of Physics》2018,13(4):138101
Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH3 adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH3 adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH3 molecules and the edge groups (-OH) further improve the capture ability of the nanosheets. 相似文献
996.
Xiaqi Ding 《数学物理学报(B辑英文版)》2012,(1):209-218
This paper gives some estimates of a quadratic functional related with Riemann Hypothesis. 相似文献
997.
A 2-dimensional gradual period photonic heterostructure was made with holography by use of non-uniform swelling effect of dichromated gelatin during processing. In this structure, the symmetric point group of triangle lattice was debased to C2V from C6V. Theoretical analysis and experimental results show that omnidirectional band gap in visible range can be achieved with this kind of heterostructure made by low refractive index materials. 相似文献
998.
This study aims to reveal the laws of the relationship between fractional-order system and integer-order system. Meanwhile, delayed feedback control is introduced to control the fractional-order PMSG (permanent magnet synchronous generator) model of a wind turbine. First, the fractional-order mathematical model of PMSG is established. Next, numerical simulations under different system orders are given and the system dynamic behaviors are analyzed in detail. Then, the delayed feedback control method is introduced to control the fractional-order PMSG and the control results when different parameters vary are analyzed. Complex dynamics are presented and some interesting phenomena are discovered. It is found that the system order influences the dynamics of the system in many aspects such as chaos pattern, bifurcation behavior, period window, shape and size of strange attractor. The delayed time, feedback gain, feedback limitation, system order can obviously influence the control result except the initial state of the system. Moreover, the feedback limitation has a minimum to successfully control the system to stable states and the system order also has a maximum to do so. 相似文献
999.
1000.
We present some necessary and sufficient conditions for positive semi-compact operators being L-weakly compact and M-weakly
compact respectively. 相似文献