Ortho-Alkoxy-benzamide Directed Formation of a Single Crystalline Hydrogen-bonded Crosslinked Organic Framework and Its Boron Trifluoride Uptake and Catalysis

Boron trifluoride (BF₃) is a highly corrosive gas widely used in industry. Confining BF₃ in porous materials ensures safe and convenient handling and prevents its degradation. Hence, it is highly desired to develop porous materials with high adsorption capacity, high stability, and resistance to BF₃ corrosion. Herein, we designed and synthesized a Lewis basic single-crystalline hydrogen-bond crosslinked organic framework (H_COF-50) for BF₃ storage and its application in catalysis. Specifically, we introduced self-complementary ortho-alkoxy-benzamide hydrogen-bonding moieties to direct the formation of highly organized hydrogen-bonded networks, which were subsequently photo-crosslinked to generate H_COFs. The H_COF-50 features Lewis basic thioether linkages and electron-rich pore surfaces for BF₃ uptake. As a result, H_COF-50 shows a record-high 14.2 mmol/g BF₃ uptake capacity. The BF₃ uptake in H_COF-50 is reversible, leading to the slow release of BF₃. We leveraged this property to reduce the undesirable chain transfer and termination in the cationic polymerization of vinyl ethers. Polymers with higher molecular weights and lower polydispersity were generated compared to those synthesized using BF₃ ⋅ Et₂O. The elucidation of the structure–property relationship, as provided by the single-crystal X-ray structures, combined with the high BF₃ uptake capacity and controlled sorption, highlights the molecular understanding of framework-guest interactions in addressing contemporary challenges.     

β-Silylacrylate as a Multipurpose Reagent in Organic Synthesis

Acrylates are well known electrophilic alkenes having multitude of applications in organic synthesis. They are very good acceptors in Michael addition reactions and are good enophile/dienophile/dipolarophile partners in cycloaddition reactions. Replacing the β-alkyl/aryl groups in acrylates by a silicon group would be interesting. In addition to the conventional reactions displayed by acrylates, β-silylacrylates (β-SAs) can show reactivity specifically related to the silicon group. Many conventional organic reactions such as hydrodimerization, organocatalytic asymmetric Michael additions, inter- and intra-molecular Diels–Alder reactions, and asymmetric 1,3-dipolar cycloadditions have been used to generate the complex chemical entities from β-SAs. Some of the reaction outcomes were vastly influenced by the silicon substituent. This review describes the practical synthesis β-SAs and their use as starting point in complex molecule generation including total synthesis of some natural products/bioactive molecules.     

Insights into stretching ratio and velocity slip on MHD rotating flow of Maxwell nanofluid over a stretching sheet: Semi-analytical technique OHAM

Main core part of the research is to develop a novel mathematical model of MHD-Maxwell nanofluid over a stretching and shrinking surface. The stretching ratio, velocity slip and convective boundary conditions are also incorporated. The PDE's with associative boundary conditions are deduced into coupled highly non-linear ODE's by utilizing suitable transformations. The deduced dimensionless sets of Ordinary differential equations are solved by Optimal-Homotopy Analysis Method (OHAM). Behavior of pertinent parameters on the velocity, temperature and concentration fields as well as important aspects skin friction, Nusselt number and Sherwood number are recorded in Table 2. Outcomes declared that role of stretching ratio plays a prominent role in stretching surfaces its clearly recorded in Table 1(a & b).     

MPKin-YSTR: Interpretation of Y chromosome STR haplotypes for missing persons cases

Y chromosome Short Tandem Repeat (STR) haplotypes have been used in assisting forensic investigations primarily for identification and male lineage determination. The current SWGDAM interpretation guidelines for Y-STR typing provide helpful guidance on those purposes but do not address the issue of kinship analysis with Y-STR haplotypes. Because of the high mutation rate of Y-STRs, there are complex missing person cases in which inconsistent Y-STR haplotypes between true paternal lineage relatives will arise and cases with two or more male references in the same lineage and yet differ in their haplotypes. Therefore, more useful methods are needed for interpreting the Y-STR haplotype data. Computational methods and interpretation guidelines have been developed specifically addressing this issue, either using a mismatch-based counting method or a pedigree likelihood ratio method. In this study, a software program, MPKin-YSTR, was developed by implementing those more sophisticated methods. This software should be able to improve the interpretation of complex cases with Y-STR haplotype evidence. Thus, more biological evidence will be interpreted, which in turn will result in more investigation leads to help solve crimes.     

Hair analysis as a new tool to monitor adherence to long-term therapy to statins

Statins are cholesterol-lowering medications which are widely prescribed as first-line treatment for hyperlipidemia, against high blood cholesterol aimed at reducing the risk of atherosclerotic diseases. Notwithstanding their undoubted efficacy, the needed long-term treatment with these drugs is characterized by a high percentage of dropout. Consequently, an effective tool to verify the patients’ compliance to statin therapy is needed. In this context, the analysis for drugs and drug metabolites in the hair may represent an almost ideal tool because, according to a sound body of forensic toxicological literature, concentrations in the hair matrix reflect the chronic intake of drugs and pharmaceuticals. In this light, in the present study, a novel, specific and sensitive ultra-performance liquid chromatography–tandem mass spectrometry method has been developed to determine six statins and their metabolites (namely atorvastatin, (p)α-OH-atorvastatin-lactone, (o)α-OH-atorvastatin-lactone, rosuvastatin, N-desmethyl rosuvastatin and pravastatin) in human hair. After optimization, the method was successfully validated in terms of selectivity, linearity, sensitivity, precision, accuracy, stability and matrix effect. Moreover, the practical applicability of this method for verifying adherence to statin therapy was assessed by testing samples of hair collected from subjects under long-term therapy with statins.     

对称季铵碱的烷基链长度对草酸电还原反应的影响

研究了四种不同烷基链长度的对称季铵碱对草酸电还原制备乙醛酸反应的影响。线性扫描测试考察了添加剂对铅电极上阴极反应的影响,结果表明对称季铵碱在电极表面的吸附对析氢反应的抑制程度大于其对草酸电还原反应的抑制程度,且随着对称季铵碱中烷基链长度的增加,添加剂抑制析氢反应效果更明显。计时安培法的结果证明添加剂可影响草酸向电极表面的扩散,随着对称季铵碱中烷基链长度的增加,草酸的扩散系数呈现出先增加后减小的趋势。恒流电解实验结果表明,添加剂能有效提高草酸电还原反应的电流效率,且提高效果随对称季铵碱所含烷基链长度的增加而增强。因此,添加剂的吸附对阴极表面析氢反应的抑制作用是草酸电还原反应电流效率提高的主要原因。本研究表明,四丁基氢氧化铵为添加剂时,草酸还原为乙醛酸的电流效率最高。     

Fluidization characteristics of sawdust in a cold flow fluidized bed

India has abundance of biomass such as rice husk, bagasse, wheat straw, sawdust etc. which is used as a main or auxiliary fuel in the fluidized bed combustor, gasifier and pyrolizer. Design of such fluidized bed equipments require the knowledge of minimum fluidization velocity (U_mf), complete fluidization velocity (U_cf) and transport disengagement height (TDH). The present work reports the fluidization characteristic, U_mf, U_cf and TDH of the individual size groups of sawdust and mixture thereof. The results indicate that the U_mf and U_cf have a tendency to increase with increase in particle diameter, however the TDH shows the reverse trend. The sawdust particle size of 925 and 1200 ​μm showed significant difference between their U_mf and U_cf, an essential parameter for controlled fluidization. Based on the experimental work new correlations for the prediction of U_mf, U_cf and TDH for sawdust sample are proposed. The proposed correlations of U_mf, U_cf and TDH are in good agreement with experimental values and the deviations found within the range of nearly ±10% for all the samples.     

ZSM-5分子筛酸位分布及其甲醇制烯烃催化性能的定向管理与调控

ZSM-5分子筛在甲醇制烯烃(MTO)过程中的催化性能和反应机理与其孔道中酸位点分布位置紧密相关. 本文证明在水热合成过程中加入适量的钠离子(Na⁺)可以增加ZSM-5分子筛交叉腔酸位点比例; 从而促进高级甲基苯的生成并加速芳烃循环, 有利于乙烯生成. 相反, 在合成过程中不添加钠离子, 所制备的ZSM-5分子筛直孔道和正弦孔道酸位点比例明显提高, 有利于促进烯烃循环并提高丙烯和C₃₊烯烃选择性.     

具有光控氧空缺的钼掺杂Bi5O7Br纳米片用于光催化氮气合成氨

氨(NH3)作为合成燃料、化肥和潜在能源载体的重要前体,是现代化学工业中最重要的化学品之一.工业中主要通过高能耗的Haber-Bosch工艺在高温高压下将氮气和氢气转化为NH3,而原料氢气由天然气蒸汽获得,因而不仅消耗大量能源,而且导致温室气体二氧化碳的大量排放,对环境造成危害.光催化固氮以光能为驱动力,以水为质子源,为合成NH3提供了一种温和、绿色和可持续的方法.然而,传统固氮催化剂具有与N2结合弱、成键难以及电子转移效率低的缺点.为了克服上述问题,在催化剂中引入氧空缺和过渡金属作为给电子中心和活性位点的策略被广泛研究.本文以半导体Bi5O7Br纳米片作为研究对象,通过在水热合成过程中添加Na2MoO4前驱盐在Bi5O7Br中掺杂钼元素,合成了不同摩尔含量的钼掺杂Bi5O7Br(Mo-Bi5O7Br)纳米片,并将其应用于光催化N2还原反应,发现Mo-Bi5O7Br的光催化固氮性能显著优于空白Bi5O7Br的催化性能.扫描电镜、透射电镜、能量色散X射线元素映射以及X射线光电子能谱的结果表明,掺杂过程不会影响Bi5O7Br纳米片的晶相和形貌,掺杂后钼元素均匀地分布在Bi5O7Br纳米片晶格中.采用紫外可见漫反射光谱、电子自旋共振光谱、氮气程序升温脱附谱以及光电化学测试等方法研究了Mo-Bi5O7Br相较于空白Bi5O7Br纳米片在光催化N2还原反应中催化性能提升的原因.UV-vis DRS结果表明,钼掺杂对Bi5O7Br可见光吸收能力具有增强作用.以催化NH3产率最高的Mo-Bi5O7Br-1(Mo摩尔百分含量为1％)为研究样本,EPR结果表明,在黑暗条件下,只有Mo-Bi5O7Br-1样品可以检测到明显的表面氧空位(OVs)信号;在光照条件下,Bi5O7Br和Mo-Bi5O7Br-1两种样品都出现OVs的信号峰,但同等光照时间下的Mo-Bi5O7Br-1具有更高的信号强度.此外,OVs信号会随着光照时间的延长逐渐增强;当移除光源后,信号强度逐渐降低.这表明Mo-Bi5O7Br-1在光照下会产生更高浓度的表面光控OVs.N2-TPD结果表明,光控OVs作为活性位点促进催化剂对N2的吸附.关闭光源后,OVs被环境中的水或氧气中的氧原子重新填充,避免了OVs易被氧化而导致反应失活的缺点,有助于保持Mo-Bi5O7Br-1催化N2还原反应的活性和稳定性.光电化学表征结果表明,Mo-Bi5O7Br-1中的光生载流子的分离和迁移效率明显提高.以上结果表明,掺杂过渡金属钼有助于Bi5O7Br纳米片表面光控OVs的生成,光控OVs作为活性位点提升了Bi5O7Br吸附和活化N2的能力,钼掺杂和光控OVs协同提高Bi5O7Br内部光生载流子的分离迁移效率,增强Bi5O7Br光催化固氮合成氨的反应性能.     

State-crossing from a Locally Excited to an Electron Transfer State(SLEET) Model Rationalizing the Aggregation-induced Emission Mechanism of (Bi)piperidylanthracenes

Luminogens with aggregation-induced emission(AIE)characteristics(or AIEgens)have been widely used in various applications due to their excellent luminescent properties in molecular aggregates and the solid state.A deep understanding of the AIE mechanism is critical for the rational development of AIEgens.In this work,the“state-crossing from a locally excited to an electron transfer state”(SLEET)model is employed to rationalize the AIE phenomenon of two(bi)piperidylanthracenes.According to the SLEET model,an electron transfer(ET)state is formed along with the rotation of the piperidyl group in the excited state of(bi)piperidylan-thracene monomers,leading to fluorescence quenching.In contrast,a bright state exists in the crystal and molecular aggregates of these compounds,as the intermolecular interactions restrict the formation of the dark ET state.This mechanistic understanding could inspire the deployment of the SLEET model in the rational designs of various functional AIEgens.