Nitrogen ligands in two-dimensional covalent organic frameworks for metal catalysis

We introduced bipyridine ligands into a series of two‐dimensional （2D） covalent organic frame‐works （COFs） using 2,2’‐bipyridine‐5,5’‐dicarbaldehyde （2,2’‐BPyDCA） as a component in the mixed building blocks. The framework of the COFs was formed by the linkage of imine groups. The ligand content in the COFs was synthetically tuned by the content of 2,2’‐BPyDCA, and thus the amount of metal, palladium（II） acetate, bonded to the nitrogen ligands could be manipulated. Both the bipyri‐dine ligands and imine groups can coordinate with Pd（II） ions, but the loading position can be var‐ied, with one ligand favoring binding in the space between adjacent COFs’ layers and the other lig‐and favoring binding within the pores of the COFs. The Pd（II）‐loaded COFs exhibited good catalytic activity for the Heck reaction.

Split Addition of Nitrogen-Rich Substrate at Thermophilic and Mesophilic Stages of Composting: Effect on Green House Gases Emission and Quality of Compost

Composting as a solution to the increasing generation of municipal solid waste (MSW), also contribute to GHGs emission when not controlled and could lack some basic nutrients, especially nitrogen. This study assessed the split-additions of nitrogen-rich substrate to composting materials and their effect on GHGs emissions as well as the quality of the composts. Nitrogen-rich substrates formulated from pig and goat manure were co-composted with MSW for a 12-weeks period by split adding at mesophilic (˚C) and thermophilic (>50˚C) stages in five different treatments. Representative samples from the compost were taken from each treatment for physicochemical, heavy metals and bacteriological analysis. In-situ CH4, CO2, N2O gas emissions were also analyzed weekly during composting. It was observed that all the treatments showed significant organic matter decomposition, reaching thermophilic temperatures in the first week of composting. The absence affects the suitable agronomic properties. All nitrogen-rich substrate applied at thermophilic stage (Treatment two) recorded the highest N, P and K concentrations of 1.34%, 0.97% and 2.45%, respectively with highest nitrogen retention. In terms of GHG emissions, CO2 was highest at the thermophilic stage when N-rich substrate was added in all treatment, while CH4 was highest in the mesophilic stage with N-rich substrate addition. N2O showed no specific trend in the treatments. Split addition of the N-rich substrate for co-composting of MSW produced compost which is stable, has less nutrient loss and low GHG emissions. Split addition of a nitrogen-rich substrate could be an option for increasing the fertilizer value of MSW compost.

Dimerization of Propylene by Nickel (Ⅱ) and Cobalt (Ⅱ) Catalysts Based on Bidentate Nitrogen-phosphino Chelating Ligands

The catalytic property of propylene dimerization by several nickel (Ⅱ), cobalt (Ⅱ) complexes containing N-P bidentate ligands was studied in combination with organoaluminum co-catalysts. The effects of the type of aluminum co-catalysts and its relative amount, the nature of precursors in terms of ligand backbone and metal center were investigated. The results indicated that precursor I (N,N-dimethyl-2-(diphenylphosphino)aniline nickel (Ⅱ) dichloride) exhibited high activity in propylene dimerization in the presence of the strong Lewis acid Et3Al2Cl3, whereas low productivity by its cobalt analogues was observed under identical reaction conditions.

Premature thermal decomposition behavior of 3,4-dinitrofurazanfuroxan with certain types of nitrogen-rich compounds

3,4-Dinitrofurazanfuroxan(DNTF),as a high-energy-density material,features good thermal stability and wide applications.This study aimed to elucidate the thermal decomposition mechanism of DNTF combined with nitrogen-rich compounds containing N-H.The thermal stabilities of DNTF and its hybrid systems were investigated using differential thermal analysis/thermogravimetry(TG),vacuum stability test,and accelerating rate calorimetry under isothermal,non-isothermal,and adiabatic conditions,respectively.Results showed that the thermal stability and thermal safety of DNTF significantly decreased after combining with nitrogen-rich compounds containing N-H.Calculation results showed that the activation energy of the DNTF hybrid systems was significantly lower than that of DNTF.The TGIR was used to monitor the generation of fugitive gases during the thermal decomposition of the DNTF/5-aminotetrazole(5-ATZ)hybrid.Moreover,the nitrogen-rich molecules containing N-H interacted extensively with DNTF,and this interaction accelerated the thermal degradation of DNTF.

SVNTHESES AND CHARACTERIZATION OF TWO HIGH VALENCE VANADIUM COMPLEXES (?) SCHIFF-BASE LIGAND WITH RICH PHENOLATE OXVGEN AND THEIR CONVERSION

Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other is a novel dinuclear V(V,V)complex with an oxo bridge.The conversion between the two complexes had been discussed.

Thermal Behavior,Sensitivity,Detonation Velocity and Pressure of a Nitrogen-Rich Compound

The nitrogen content of tetrazolo triazines is 68.9%.In this paper,tetrazolotriazines was synthetized.The TG-DSC test indicated its decomposition process in detail.The non-isothermal kinetic parameters were speculated by Kissinger and Ozawa methods.It revealed the mechanism function of thermal decomposition.The impact and friction sensitivity were tested.The detonation pressure and velocity were calculated.It has a wide range of potential applications as a kind of energetic material.

Impact of nitrogen addition on plant community in a semi-arid temperate steppe in China

Increased nitrogen （N） deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels （0, 3, 6, 12, 24, and 48 g N/（m2-a）） were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/（m2.a） above ambient N deposition （1.2 g N/（m2.a））, led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses （PB） but decrease perennial forbs （PF）, and induce a slight change in the biomass of shrubs and semi-shrubs （SS）. The biomass of annuals （AS） and perennial rhizome grasses （PR） accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups.

Temporal stability of aboveground net primary production in northern Tibet alpine steppe in response to nitrogen addition

The mechanism that sustains the temporal stability of aboveground net primary production(ANPP)respond to nitrogen deposition is still controversial.Consequently,we investigated the mechanism of temporal stability of ANPP through the effect of N addition on diversity,species asynchrony andportfolio effects in northern Tibet alpine steppe over a period of three years.Our results showed that the community temporal stability did not significantly correlate with the species richness and Shannon–Wiener diversity.Species asynchrony and stability was also not significantly affected by N addition(p>0.05).Furthermore,there was no significant relationship between species asynchrony and temporal stability.Although the value of portfolio effects(z)(z=1.304,95%confidence intervals:1.029–1.597)was more than 1,the portfolio effects was not a primary driver of temporal stability due to the biodiversity being unaffected.The above results suggested that the richness,species asynchrony and portfolio effect could not support for mechanism of stability at the alpine steppe.From the results of path analysis,species temporal stability positively supports the community temporal stability in the alpine steppe ecosystem.According to the character of environment and vegetation of alpine steppe at North Tibet,we inferred that dominance species stability is more important than species richness for the community temporal stability.

Characterization and catalytic performance of CeO_2-Co/SiO_2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor

The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.

One-pot synthesis of Ag-rich AgPd alloy nanoactiniae and their enhanced electrocatalytic activity toward oxygen reduction

The electro-catalytic properties can be effectively optimized by designing bimetallic alloy nanoparticles with high-content less-active metal to enhance the competence of more-active noble metal. Herein, a one-pot hydrothermal approach is demonstrated for the controllable synthesis of Ag-rich Ag_9Pd_1 alloy nanoactiniae with obviously enhanced electro-catalytic activity(2.23 mA cm^(-2) at 0.85 V) and stability for oxygen reduction reaction. In alkaline solution, the ORR onset potential and half-wave potential of the Ag_9Pd_1 alloy nanoactiniae can reach a value of 1.02 V and 0.89 V, respectively, which origin from strong ligand and ensemble effects between Pd element and Ag element. The nanocrystals are uniformly alloyed, displaying a Ag_9Pd_1 combination, as displayed by an assembly of X-ray diffraction(XRD) spectrum,energy dispersive X-ray(EDX) analysis, and cyclic voltammetry(CV). This concept of tuning bimetallic alloy nanocrystals with low concentrations of more precious metal may be a promising approach to be applicable to a wide range of alloy nanocrystals.

泛癌分析揭示SREK1在低级别胶质瘤中促进CD274表达

目的剪接调节谷氨酸和富赖氨酸的蛋白质1(SREK1)在多种肿瘤中的泛癌分析,揭示SREK1在泛癌中的作用。方法利用在线数据库GEPIA 2、TIMER 2.0、TISIDB和cBioPortal分析SREK1表达对肿瘤患者预后的影响、在低级别胶质瘤(LGG)肿瘤组织中的表达、遗传变异的特征及其表达对肿瘤组织中免疫细胞的浸润和免疫—肿瘤靶基因的相关性分析。结果LGG肿瘤组织中,SREK1表达与记忆B细胞、活化的CD4+T细胞、Th2细胞、中性粒细胞、NKT细胞以及单核细胞和CD56dimNK细胞的浸润存在相关性(P均<0.05)。SREK1与免疫—肿瘤靶基因如信号传导及转录激活蛋白3(STAT3)、Ⅰ型干扰素受体1(IFNAR1)、核受体亚家族3C组成员1(NR3C1)和表皮生长因子受体(EGFR)、表面抗原分化簇274(CD274)等表达在LGG中均呈正相关(P均<0.05)。结论SREK1是LGG患者的危险因子之一,可能通过促进CD274的表达来加剧LGG的进展。

3,5,7-三氨基-[1,2,4]三唑并[4,3-a][1,3,5]三嗪五唑盐的合成与性能

以五唑银为原料与3,5,7-三氨基-[1,2,4]三唑并[4,3-a][1,3,5]三嗪盐酸盐通过复分解反应合成了一种新型非金属五唑盐——3,5,7-三氨基-[1,2,4]三唑并[4,3-a][1,3,5]三嗪五唑盐(4)。通过X-射线单晶衍射、红外光谱(IR)、元素分析(EA)、核磁共振(NMR)对合成的新型五唑盐进行了结构表征,并采用热重分析(TG)和差示扫描量热分析(DSC)测试其热分解行为。使用原子化法计算了化合物4的生成焓,使用EXPLO5预测了爆轰性能,并采用BAM方法测试其撞击感度和摩擦感度。测试结果显示,化合物4的晶体密度为1.644 g·cm^(-3),属单斜晶系,P21/n空间群,氮含量77%,热分解温度113.8℃,生成焓491.5 kJ·mol^(-1),爆速7913 m·s^(-1),爆压19.6 GPa,撞击感度>40 J,摩擦感度>360 N。

含氟富氮多孔有机聚合物的合成及其对水中全氟辛酸的去除

全氟辛酸(PFOA)在自然环境中难以降解,会通过富集渗透污染水体和土壤,从而对自然环境和人体健康造成影响。开发成本低、效率高、环保的吸附剂实现环境水体中PFOA的高效吸附去除是解决PFOA污染的有效途径之一。本研究采用无溶剂一锅法设计、制备了一种含氟富氮多孔有机聚合物(POP-3F),通过引入氟原子增加了材料的疏水性,增加了主客体分子间的疏水作用、氟-氟相互作用,提升了材料对PFOA的吸附效果。使用扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、X-射线衍射仪(XRD)、固体核磁(ssNMR)、X射线光电子能谱仪(XPS)、热分析系统(TGA)等对POP-3F进行了表征。结合液相色谱-串联质谱法(LC-MS/MS),研究了POP-3F在不同pH、盐浓度和腐植酸条件下对PFOA的吸附性能。在pH值为2时,POP-3F对PFOA的去除率最高达到98.6%,可用于去除酸性工业废水中的PFOA。并且POP-3F对于PFOA的去除率几乎不受NaCl和腐植酸浓度的影响,在加入NaCl后,POP-3F表面会形成双电层,可以削弱POP-3F与PFOA之间的静电相互作用,去除率仅下降了1%。腐植酸与PFOA存在竞争吸附,在高浓度腐植酸条件下,POP-3F对PFOA的去除率仅下降了0.73%。在最佳pH条件下考察了吸附等温线和吸附动力学,通过数学模型拟合了实验结果,探究了吸附机理。结果显示,POP-3F的理论容量为191 mg/g,高于活性炭和其他多数吸附剂,表现出较高的吸附容量。此外,POP-3F对PFOA的吸附去除几乎不受基质种类的影响,在模拟自然水中吸附效果略有降低(仅降低0.1%),经过5次吸附-解吸循环后,对PFOA的去除率仅微幅下降(降低0.67%),表明其具有循环使用和可再生性,在实际PFOA污染废水处理中具有广阔的应用前景。

淬熄高度和空气分配比例对RQL燃烧室燃烧特性的影响

基于富油/淬熄/贫油(RQL)技术原理,设计一种燃气轮机低排放燃烧室.在保持燃烧室进口参数不变的前提下,研究不同淬熄结构高度及空气流量分配比例对燃烧室内流场、温度场及污染物生成特性的影响.结果表明:淬熄结构高度和空气分配比例是影响燃烧室燃烧性能的重要参数,随着淬熄结构高度的降低,燃烧室出口氮氧化物NO_(x)的排放量增加;随着富油区主燃孔与淬熄空气质量流量的空气分配比例降低,燃烧室出口NO_(x)的排放量先降低后增加,存在一个最佳的空气分配比例使NO_(x)排放量最低;热力型NO_(x)的生成量与温度高于1900 K的区域大小和最高燃气温度存在直接关系.基于此设计的燃烧室在所研究的工况下,最低NO_(x)排放量可低于35 mg/m^(3),达到了低污染燃烧室排放标准.

基于Noradamantane的高能量密度富氮笼型含能分子设计与性能预估

研究提出一种通过化学键键能差进行能量密度快速估算的方法,和一种利用拉普拉斯键级和分子片段键离解能相结合快速判断笼型结构稳定性的方法。通过穷举法构建了基于Noradamantane的所有富氮骨架及其435种硝基衍生物,应用上述计算方法筛选兼具高能量密度和稳定性的分子结构,并采用量子化学能量计算和过渡态反应势垒计算验证筛选结果的可靠性。计算发现了两种兼顾高能量密度和结构稳定性的硝基化合物,其爆热、爆速、爆压和金属加速能力的理论计算最大值分别达到7.77 k J·g^(-1)、10.1 km·s^(-1)、47 GPa和1.14倍HMX的金属加速能力,且结构分解反应势垒≥96 k J·mol^(-1)。本研究所建立的含能分子能量密度和稳定性快速筛选方法,可为高能稳定的含能分子设计提供参考。

应用于适配器分离增程的富氮化合物推力器研究

推力器采用富氮化合物五氨基四唑作为主要产气装药,并利用贮气室高压环境和收缩扩张喷管形成超声速气体射流,进而获得有效的推力,提升火箭导弹发射时适配器的分离距离。结合滑行滚动发电供电装置及推力器试制,开展了推力器的静力测试和动态分力测试,测试结果表明该推力器能够有效实现适配器的分离增程,且结构简单,适应能力强,能够为相关研究和应用提供参考。

电化学合成偶氮桥连富氮杂环含能化合物的研究进展

偶氮桥连富氮杂环含能化合物在含能材料领域应用广泛。传统构建偶氮桥连化合物通常采用氧化偶联法,存在安全风险高和环境污染严重等问题。电化学合成方法由于其高效、可控和环境友好等优点备受研究者青睐。本文围绕近年来呋咱、吡唑、三唑、四唑等偶氮桥连富氮杂环含能材料的电化学合成研究,介绍了电解质和电极等条件对反应的影响,总结了不同偶氮桥连富氮杂环含能化合物的电化学合成机理,提出了未来的研究方向,如采用电化学制备传统方法无法合成的含能分子,利用电化学方法实现氮-氮单键、碳-氮单键、分子内偶氮键等化学键的构建,和探索稠环以及连环等复杂含能材料的电化学合成以及电化学合成方法的工程化放大研究等,为电化学合成偶氮桥连富氮含能分子的研究和采用电化学方法制备含能材料提供参考。未来研究中可以通过电化学方法实现已知含能材料的绿色合成,并且定制化生产和开发传统有机合成方法无法制备的高性能新含能材料。

富氮多环含能离子盐的合成和性能

以多氨基稠环化合物6,7-二氨基-3亚氨基-[1,2,4]三唑并[1,2,4]三唑连四唑(TATOT-T)为原料,经过高锰酸钾氧化偶联和高氯酸成盐等步骤,合成了一种偶氮桥联的富氮多环含能化合物2,2′-二四唑基-3,6-二氨基-7,7′-偶氮基-[1,2,4]三唑并[1,2,4]三唑高氯酸盐(2)。采用傅里叶红外光谱、核磁共振、元素分析、X-射线单晶衍射技术,以及差示扫描量热法(DSC)和热重分析(TG)对化合物2进行结构表征和热性能分析,结合高斯软件计算的生成焓,使用EXPLO5软件计算了其爆轰性能。结果表明,所得化合物2晶体属于单斜晶系,晶体密度为1.750 g·cm^(-3),每个晶胞中包含4个分子,起始热分解温度为232.6℃,理论爆速为8373 m∙s-1,爆压为29.05 GPa,撞击感度为40 J,摩擦感度为360 N,对外界机械刺激钝感,具有良好综合性能。

两种富氮稠环型1,2,5-噁二唑类含能盐的合成及性能

以5,6-二肼基-[1,2,5]噁二唑并[3,4-b]吡嗪(1)为原料合成了5,5′-(肼-1,2-二亚基亚胺)双(5,7-2H‑[1,2,5]噁二唑并[3,4-e][1,2,4]三唑并[4,3-a]吡嗪-8(4H)-亚胺)高氯酸盐(2)和5,5′-(二氮烯-1,2-二亚基)双([1,2,5]噁二唑并[3,4-e][1,2,4]三唑并[4,3-a]吡嗪-8(7H)-亚胺)硝酸盐(3)两种富氮含能盐。采用核磁共振(NMR)、傅里叶红外光谱(FT-IR)、元素分析(EA)、X-射线单晶衍射(XRD)等多种手段对含能离子盐2和3的结构进行了表征,利用差示扫描量热法(DSC)研究其热分解行为,运用BAM标准测试方法获得摩擦感度和撞击感度,同时基于等键反应方程与EXPLO5软件预测其爆轰性能。结果表明,化合物2和3的晶体均属于单斜晶系,分别属于Pn和P21/n空间群,二者的晶体结构中阳离子部分具有良好的平面性,晶体堆积图中观察到了大量氢键。化合物2和3的热分解温度分别为154℃和130℃,理论爆速分别为7722 m·s^(-1)和8008 m·s^(-1),理论爆压分别为26.3 GPa和28.4 GPa,摩擦感度均为360 N,撞击感度均大于40 J。化合物2和3在爆轰性能、摩擦感度、撞击感度性能上均优于传统炸药TNT。