金属有机骨架及其复合材料基于筛分复合效应的C2分离的研究进展

精细化分离是石油化工生产的关键技术及研究热点之一, 其中C₂ (C₂H₂/C₂H₄和C₂H₄/C₂H₆)的高效精细分离更是现代化工过程中高质量生产的难点和新挑战. 传统的热驱动分离过程(如精馏分离和选择性催化加氢分离)存在能耗高、经济效益低的缺陷, 而采用非热驱动分离过程(如吸附分离和膜分离)可大幅度节能降耗. 在众多吸附分离材料中, 金属有机骨架(MOF)材料拥有庞大的组分/结构单元库, 其组成和孔结构的可控、可调特性为C₂的精细化高效分离带来了新的机遇. 以此为导向, 整理并归纳了近年来MOF⁺材料(MOF及其复合材料)的晶体和孔道参数, 分析其在高效分离C₂方面的科学研究成果, 针对MOF⁺材料的设计、可控制备、孔径调控机制等关键科学问题, 提出了未来MOF⁺材料的研究趋势.     

CeO2对CuCl/活性炭吸附剂C2H4/C2H6吸附分离性能促进作用

通过等体积浸渍方法制备了添加CeO₂助剂的用于C₂H₄/C₂H₆吸附分离的CuCl/活性炭(AC)吸附剂,使用氮气吸附-脱附曲线、X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、能量分散X射线光谱(EDX)等分析方法对吸附剂进行了表征.结果表明,吸附剂表面Cu(II)在氮气气氛焙烧过程中被部分还原成Cu(I).重点研究了Ce元素的添加对于吸附剂的C₂H₄/C₂H₆吸附分离性能的影响,等温吸附曲线结果表明添加了CeO₂的吸附剂通过降低乙烷的吸附容量从而显著提高了吸附分离性能. XRD及XPS结果表明,和未添加助剂样品相比,其表面晶体团簇较小,分散性更好, Cu(II)还原程度更高.添加CeO₂的吸附剂样品5Ce50Cu(CeO₂和CuCl2的质量分数(w)分别为5%和50%)获得了最好的吸附分离效果,相对于未添加CeO₂的样品50Cu,其在660 kPa下的吸附选择性由4.2提升到8.7.     

C40H2各种可能异构体稳定性的理论研究

采用AM1和PM3两种半经验方法,对D_5d对称性的C₄₀及C₄₀H₂所有可能异构体的几何构型进行了非限制对称性全优化,得到51种稳定异构体,在此基础上研究了氢的加成反应规律及本体C₄₀和最稳定及最不稳定C₄₀H₂异构体的红外光谱,讨论了影响C₄₀(D_5d)氢加成异构体稳定性及加成位置选择性的三种主要因素:(1)C₄₀本体几何结构;(2)共轭效应;(3)电荷分布影响.     

CO2/C3H6O在金属氧化物耦合吡咯氮生物炭表面的共/竞吸附机理研究

本研究采用密度泛函理论,通过比较吸附量、吸附能以及态密度和电荷差分密度的分析,探究了不同金属氧化物耦合吡咯氮生物炭(CN5@MO_x,MO_x=ZnO、CaO、Na₂O)表面CO₂与C₃H₆O(CO₂&C₃H₆O)的吸附机理。首先从CO₂/C₃H₆O单组分方面计算了其在CN5@MO_x表面吸附量和吸附能,计算结果表明,在333 K、100 kPa时CN5@Na₂O表面对CO₂/C₃H₆O单组分吸附量分别为3.65、15.34 mmol/g,吸附能分别为-145.86、-132.47 kJ/mol,均高于CO₂/C₃H₆O单组分在CN5@CaO及CN5@...     

C59(C6H4OCH3)N的结构、光谱和二阶非线性光学性质的理论研究

用INDO系列方法对由(C₅₉N)₂和苯甲醚合成的衍生物C₅₉(C₆H₄OCH₃)N进行了理论研究,得到了分子的稳定构型.结果表明,C₅₉(C₆H₄OCH₃)N具有C_s对称性.以优化构型为基础讨论了分子的UV-Vis光谱、NMR谱线数,结果与实验符合得很好.本文还计算了C₅₉(C₆H₄OCH₃)N的二阶非线性光学系数β_μ,结果表明这种物质具有较大的二阶非线性光学系数.     

266 nm激光光解C2H5SSC2H5产物的激光诱导荧光光谱

有机硫化物是大气主要污染物之一,其在大气中的光解产物还将造成二次污染,除了存在于有机硫化物中, S―S键还存在于胱氨酸等蛋白质中, S―S键的形成和断裂决定该类蛋白质的活性.本工作中,我们研究了用实验室常见的Nd:YAG激光器的四倍频266 nm激光光解C₂H₅SSC₂H₅过程,通过激光诱导荧光(LIF)光谱方法检测乙硫自由基C₂H₅S等光解产物.实验表明266 nm激光主要光解C₂H₅SSC₂H₅的S―S键产生C₂H₅S自由基.本文应用密度泛函理论的Becke3-Lee-Yang-Parr泛函(B3LYP方法)得到C₂H₅SSC₂H₅的S―S键、C―S键和C―C键的解离势能曲线,可知在266 nm光解条件下, C₂H₅SSC₂H₅在基态能够发生S―S键、C―S键解离, C―C键不发生解离.本文采用全活化空间自洽场(CASSCF)方法优化得到态和态的C₂H₅S自由基结构及其跃迁的绝热激发能,以辅助解析实验检测的C₂H₅S自由基的LIF光谱.实验结合理论计算最终得出,本实验266 nm光解条件下, C₂H₅SSC₂H₅主要发生S―S键解离,不排除少量分子发生C―S键解离的可能性.     

C36H2异构体的稳定性及其加成位置选择性的研究

使用AM1和PM3两种半经验方法,对所有的C₃₆H₂异构体实行非对称性限制的全优化,并结合频率分析及HF/6-31G单点能计算,确定了各异构体的基态结构及其相对稳定性.在此基础上,通过分析加成位置与异构体稳定性之间的关系,得出三条加成位置选择性的规律.最后,利用π-轨道轴矢量(POAV)方法计算了反应前后碳笼中张力的变化.张力与键级分析的结果表明加成位置选择性的规律不是由碳笼释放的张力决定的,而是由C₃₆H₂体系的总共轭性质决定的.     

富勒烯C36及其衍生物C36H2n的量子化学研究

应用密度泛函B₃LYP方法和从头算(abinitio)HF方法,在3-21G理论水平上,对具有C_2v,D_2d,D_3h和D_6h对称性的四种C₃₆异构体以及在保持D_2d,D_3h和D_6h对称性条件下形成的不同氢化物进行了量子化学计算,研究了它们在不同量子态时的分子几何构型和电子结构.结果表明,电子相关效应在C₃₆簇化合物的电子结构中起着重要作用.它们最稳定的结构是C₃₆的³A_2u量子态D_6h异构体,而C₃₆的氢化物是在D_3h异构体的C₂位置等同碳原子上形成的¹A_1'量子态氢化物C₃₆H₁₂.     

H2,C2H4在铂及铂锡合金上化学吸附的量子化学计算

本文详尽地分析了推广的休克尔分子轨道理论方法(EHMO)中参量化过程。借助于计算双原子体系选择出合理的经验参数和近似方式,引进了过渡金属内层原子轨道排斥作用项。分别计算了H,H₂,C₂H₄和C₂H₃在铂及铂锡合金上化学吸附键能,计算结果表明,同铂金属比较,在铂锡合金上H原子,C₂H₄分子的化学吸附键变弱在锡富集的铂锡合金上单个的铂原子不能解离吸附H₂分子,在铂锡合金上C₂H₄脱氢反应较难进行。     

高通量筛选金属-有机框架:分离天然气中的硫化氢和二氧化碳

采用分子模拟高通量筛选的方法研究了6013种实验已经合成的金属-有机框架（MOFs）对天然气五元混合物（CH₄,C₂H₆,C₃H₈,H₂S和CO₂）中H₂S和CO₂的吸附分离性能.为了综合吸附量和选择性这两项指标,我们首先比较了三种权衡方法[权衡α法（Tradeoff between S_{H2S+CO2/C1-C3} and N_H2S+CO2,TSN）,标准值法（Standard normal method,SNM）和权衡β法（Tradeoff between selectivity and capacity,TSC）].接着,针对四种MOF描述符[最大孔径（LCD）,孔隙率（φ）,比表面积（VSA）和吸附热（Q_st⁰）],通过Pearson相关系数分析了每种描述符分别对三种权衡变量的相关性,结果显示TSC法与四种MOF描述符的相关性最佳.然后,使用多元线性回归方法定量地分析了四种MOF描述符分别对TSC的影响程度;而决策树模型则被用于规划性能高效MOFs的设计路径.最后,20种性能最优MOFs从数据库中脱颖而出,它们将为净化天然气技术的发展提供坚实的理论指导.     

Crossover Sorption of C2H2/CO2 and C2H6/C2H4 in Soft Porous Coordination Networks

Porous sorbents are materials that are used for various applications, including storage and separation. Typically, the uptake of a single gas by a sorbent decreases with temperature, but the relative affinity for two similar gases does not change. However, in this study, we report a rare example of “crossover sorption,” in which the uptake capacity and apparent affinity for two similar gases reverse at different temperatures. We synthesized two soft porous coordination polymers (PCPs), [Zn₂(L1)(L2)₂]_n (PCP-1) and [Zn₂(L1)(L3)₂]_n (PCP-2) (L1= 1,4-bis(4-pyridyl)benzene, L2=5-methyl-1,3-di(4-carboxyphenyl)benzene, and L3=5-methoxy-1,3-di(4-carboxyphenyl)benzene). These PCPs exhibits structural changes upon gas sorption and show the crossover sorption for both C₂H₂/CO₂ and C₂H₆/C₂H₄, in which the apparent affinity reverse with temperature. We used in situ gas-loading single-crystal X-ray diffraction (SCXRD) analysis to reveal the guest inclusion structures of PCP-1 for C₂H₂, CO₂, C₂H₆, and C₂H₄ gases at various temperatures. Interestingly, we observed three-step single-crystal to single-crystal (sc-sc) transformations with the different loading phases under these gases, providing insight into guest binding positions, nature of host–guest or guest-guest interactions, and their phase transformations upon exposure to these gases. Combining with theoretical investigation, we have fully elucidated the crossover sorption in the flexible coordination networks, which involves a reversal of apparent affinity and uptake of similar gases at different temperatures. We discovered that this behaviour can be explained by the delicate balance between guest binding and host–guest and guest-guest interactions.     

Sieving Effect for the Separation of C2H2/C2H4 in an Ultrastable Ultramicroporous Zinc-Organic Framework

The separation of C₂H₂ from C₂H₄ is one of the most challenging tasks due to the similarity of their physical properties. In addition, green synthetic protocol and adsorbent's stability are also the major concerns during the separation. Herein, under hydrothermal green synthesis conditions, an ultrastable ultramicroporous Zn-MOF was designed and synthesized with a high yield. The pore diameter of the Zn-MOF is 3.6 Å, which lies in between the diameters of C₂H₂ (3.3 Å) and C₂H₄ (4.2 Å) molecules, leading to an efficient separation of the C₂H₂/C₂H₄ mixtures by the sieving effect. The practical separation performance of C₂H₂/C₂H₄ was confirmed by the dynamic breakthrough experiments. Moreover, the high stability enables the adsorption capacity of the Zn-MOF to C₂H₂, which can be maintained under a wide range of pH (1–13). Molecular simulations were also performed to identify the different C₂H₂- and C₂H₄-binding sites in Zn-MOF.     

A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2H6/C2H4 Separation

Developing adsorptive separation processes based on C₂H₆-selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C₂H₄ purification from C₂H₄/C₂H₆ mixtures, which however remains challenging. During our studies on two isostructural metal–organic frameworks ( Ni-MOF 1 and Ni-MOF 2 ), we found that Ni-MOF 2 exhibited significantly higher performance for C₂H₆/C₂H₄ separation than Ni-MOF-1 , as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C−H⋅⋅⋅π with C₂H₆ over C₂H₄ while the suitable pore spaces enforce its high C₂H₆ uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg⁻¹ of polymer-grade C₂H₄ product from equimolar C₂H₆/C₂H₄ mixtures at ambient conditions.     

Theoretical and kinetic study of the H + C2H5CN reaction

The reaction of H radical with C₂H₅CN has been studied using various quantum chemistry methods. The geometries were optimized at the B3LYP/6‐311+G(d,p) and B3LYP/6‐311++G(2d,2p) levels. The single‐point energies were calculated using G3 and BMC‐CCSD methods based on B3LYP/6‐311++G(2d,2p) geometries. Four mechanisms were investigated, namely, hydrogen abstraction, C‐addition/elimination, N‐addition/elimination and substitution. The kinetics of this reaction were studied using the transition state theory and multichannel Rice‐Ramsperger‐Kassel‐Marcus methodologies over a wide temperature range of 200–3000 K. The calculated results indicate that C‐addition/elimination channel is the most feasible over the whole temperature range. The deactivation of initial adduct C₂H₅CHN is dominant at lower temperature with bath gas H₂ of 760 Torr; whereas C₂H₅+HCN is the dominant product at higher temperature. Our calculated rate constants are in good agreement with the available experimental data. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Thermal decomposition of Pr[(C_5H_8NS_2)_3(C_(12)H_8N_2)]

The thermal behavior of the complex Pr[(C5H8NS2)3(C12H8N2)] in a dry nitrogen flow was examined by TG-DTG analysis. The TG-DTG investigations indicated that Pr[(C5H8NS2)3-(C12H8N2)] was decomposed into Pr2S3 and deposited carbon in one step where Pr2S3 predominated in the final products. The results of non-isothermal kinetic calculations showed that the decomposition stage was the random nucleation and subsequent growth mechanism (n = 2/3), the corresponding apparent activation energy ?was 115.89 kJ·mol-1 and the pre-expo-nential constant ln[A/s] was 7.8697. The empirical kinetics model equation was proposed as/(α) =3/2(1-α)[-ln(1-α)]1/3.The X-ray powder diffraction patterns of the thermal decomposition products at 800℃under N2 atmosphere show that the product can be indexed to the cubic Pr2S3 phase. The transmission electron microscopy (TEM) of the final product reveals the particle appearance of a diameter within 40 nm. The experimental results show that the praseodymium sulfide nanocrystal can be prepared from thermal decomposition of Pr[(C5H8NS2)3(C12H8N2)].     

Ultramicroporous Covalent Organic Framework Nanosheets with Functionality Pair for Membrane C2H2/C2H4 Separation

Gas separation efficiency of covalent organic framework (COF) membrane can be greatly elevated through precise functionalization. A pair-functionalized COF membrane of 1,3,5-triformylphloroglucinol (TP) and isoquinoline-5,8-diamine (IQD) monomers in two and three nodes is designed and synthesized. TP-IQD is crystallized in a two-dimensional structure with a pore size of 6.5 Å and a surface area of 289 m² g⁻¹. This COF possesses N−O paired groups which cooperatively interact with C₂H₂ instead of C₂H₄. TP-IQD nanosheets of ≈10 μm in width and ≈4 nm in thickness are prepared by mechanical exfoliation; they are further processed with 6FDA-ODA polymer into a hybrid membrane. High porosity and functionality pair of TP-IQD offer the membrane with significantly increased C₂H₂ permeability and C₂H₂/C₂H₄ selectivity which are 160 % and 430 % higher of pure 6FDA-ODA. The boosted performance demonstrates high efficiency of the pair-functionality strategy for the synthesis of separation-led COFs.     

On the interaction of Mo and Mo2 with NH3, C2H4, and C3H6

The reactivity of Mo and Mo₂ with ammonia, ethene, and propene molecules has been investigated by using Density Functional Theory. Different gradient‐corrected and hybrid exchange‐correlation functionals have been employed. Coordination modes, binding energies, geometrical structures, vibrational frequencies have been computed and compared with the available experimental counterparts. The results obtained show that the molybdenum atom is able to react with C₂H₄ and C₃H₆, and binds weakly with NH₃. The dimer Mo₂ gives a stable complexes with ammonia, ethene, and propene. For the Mo₂NH₃ complex, all the employed levels of theory give binding energies in good agreement with the experimental value, while in the case of the MoC₂H₄ system, the use of model core potentials coupled with gradient‐corrected exchange‐correlation functionals overestimates the binding energies. For MoC₃H₆, Mo₂C₂H₄, and Mo₂C₃H₆ we predict a binding energy of 14–15, 20–24, and 18–20 kcal/mol, respectively. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1557–1564, 2001     

C–H Arylation of Benzene with Aryl Halides using H2 and a Water-Soluble Rh-Based Electron Storage Catalyst

This paper reports the first example of C−H arylation of benzene under mild conditions, using H₂ as an electron source {turnover numbers (TONs)=0.7–2.0 for 24 h}. The reaction depends on a Rh-based electron storage catalyst, and proceeds at room temperature and in aqueous solution. Furthermore, the H₂ is inactive during the radical transfer step, greatly reducing unwanted side reactions.     

1H and 13C spectral assignment of 2(1H)-pyridone derivatives

1H and 13C NMR spectroscopic data for 4-aryl-3,4-dihydro-6-methyl-2(1H)pyridone derivatives were fully assigned by a combination of one- and two- dimensional experiments (DEPT, HMBC, HMQC, COSY, NOE).     

不饱和类硅烯H2C=SiNaF的DFT研究

用密度泛函理论方法, 在B3LYP/6-31+G(d, p)水平上研究了不饱和类硅烯H2C=SiNaF的结构. 结果表明, 不饱和类硅烯H2C=SiNaF共有四种平衡构型, 其中非平面的p-配合物型构型能量最低, 是不饱和类硅烯H2C=SiNaF存在的主要构型. 对平衡构型间异构化反应的过渡态进行了计算, 求得了转化势垒. 计算预言了最稳定构型的振动频率和红外强度.