Impact of molecular flexibility on binding strength and self-sorting of chiral π-surfaces

In this work, we have explored for the first time the influence of conformational flexibility of π-core on chiral self-sorting properties of perylene bisimides (PBIs) that are currently one of the most prominent classes of functional dyes. For this purpose, two series of chiral macrocyclic PBIs 3a-c and 4a-c comprising oligoethylene glycol bridges of different lengths at the 1,7 bay positions were synthesized and their atropo-enantiomers (P and M enantiomers) were resolved. Single crystal analysis of atropo-enantiomerically pure (P)-3a not only confirmed the structural integrity of the ethylene glycol bridged macrocycle but also illustrated the formation of π-stacked dimers with left-handed supramolecular helicity. Our detailed studies with the series of highly soluble chiral PBIs 4a-c by 1- and 2-D (1)H NMR techniques, and temperature- and concentration-dependent UV/vis absorption and circular dichroism (CD) spectroscopy revealed that in π-π-stacking dimerization of these PBIs chiral self-recognition (i.e., PP and MM homodimer formation) prevails over self-discrimination (i.e., PM heterodimer formation). Our studies clearly showed that with increasing conformational flexibility of PBI cores imparted by longer bridging units, the binding strength for the dimerization process increases, however, the efficiency for chiral self-recognition decreases. These results are rationalized in terms of an induced-fit mechanism facilitating more planarized π-scaffolds of PBIs containing longer bridging units upon π-π-stacking.     

Quantum chemical investigations on the structure–property relationship of aminopolynitrotriazoles

Density functional theory (DFT) has been employed to study the geometric and electronic structures, band gap, thermodynamic properties, density, and performance properties of a series of polynitrotriazoles at the B3LYP/aug-cc-pVDZ level. The detonation performances were evaluated by the Kamlet–Jacobs semi-empirical equations based on the calculated densities and heats of reaction. It has been found that the model compounds with the predicted densities of 1.8 g/cm³, detonation velocities of 8.8 km/s, and detonation pressures of 35 GPa may be novel potential candidates of high energy density materials. The discrepancies in the performance properties, stabilities or sensitivities among isomers are caused by the relative position of NH₂ and NO₂ groups.     

Hydrothermal synthesis, structure and photocatalytic property of nano-TiO_2-MnO_2

TiCI4 and MnSO4.H2O as raw materials are hydrolyzed stiochiometrically, following the intermediate of oxide hydrating reacts at 150℃, 0.5 MPa in high-pressure reactor, after filtering, washing and drying, nanometric TiO2-MnO2 (Ti1-xMnxO2) is prepared. The effects of the reaction temperature and time on nanometric TiO2-MnO2 are also discussed. XRD shows that the product is TiO2-MnO2 with amorphous phase. After being sintered at above 780℃, it transfers into Ti1-xMnxO2 with a rutile structure. TEM shows that TiO2-MnO2 is the spherical particle. And the average diameter of the particles is 20 nm. The optical absorbance was determined by UV-265 spec-trophotometer after dispersing the sample in the mixture of water and glycerol with the ratio of 1 : 1 equably. It is found that the nano-material possesses the advantages of both nano-TiO2 and nano-MnO2, and it has strong absorption in the UV and visible region. Photodegradation of dyes in an aqueous solution is investigated using nanometricTiO2-MnO2 as a pho     

Effect of Dissolved CO_2 and Tetrahydrofuran on the Polymerization of Acrylic Acid

Recently,c0mpressedgaseshavebeenusedins0megasantisolventprocesses,suchasfractionati0n0fnaturaIproducts,recrystallization0forganicandin0rganicmaterials,andpolymerpr0cessing'2.WestudiedtheeffectofthedissovledsupercriticaICO=andTHFonthep0lymerizati0n0fAA.Itwasn0tfoundintheliterature.ExperimentalOnemlacrylicacidmonomer,O.O20ginitiator2,2'-azobis(is0butyronitrile)(AlBN),anddesiredam0unt0fTHFwereaddedintoanopticalcelloflOml.CO,wascharged,stirreduntilvap0r-liquidequilibriumwasreachedatabout30…     

Influence of the surface structure of β-cyclodexrin-containing silica on the adsorption of mercury nitrate from dilute solutions

The construction of adsorption sites for mercury(II) by chemical immobilization of β-cyclodextrin and its functional derivatives on a surface of macroporous amorphous silica is proposed. It is shown that the adsorption of mercury(II) is adequately described by the Langmuir isotherm equation for monolayer adsorption on localized sites of energetically homogeneous surfaces. It is established that the considerably increased sorption of mercury nitrate on silica modified by different β-cyclodextrins is due to the formation of 1: 1 β-cyclodextrin-nitrate ion inclusion complexes on the surface and the participation of side functional groups of the upper edge of immobilized β-cyclodextrin molecules in the formation of mixed-ligand mercury(II) complexes.     

Influence of swallowing Aids on the adsorption and palatability of Kremezin®

The purpose of this study was to evaluate the effect of three swallowing aids on the adsorbent properties and palatability of a mixture of the oral charcoal adsorbent, Kremezin?. None of the swallowing aids had any effect on the adsorption of indole by Kremezin?, either in vitro and in vivo. In gustatory sensation tests of the palatability of the swallowing aids with Kremezin?, 14 items were evaluated according to the semantic differential (SD) method. Factor analysis of the results identified two main factors 'Remaining after removing from mouth' and 'Sense of holding in mouth' as predominantly determining the palatability. The swallowing aid with the highest viscosity allowed the best dispersion of Kremezin?, and also improved the palatability of Kremezin? the most.     

Electronic structure and property studies of the first crowned [60] fulleropyrrolidine

The computations of the electronic structures and properties of a novel crowned [60] fulleropyrrolidine (CFP) were performed by means of AM1 methods. It has been indicated that CFP has four isomers in which the dihedral angle between phenyl group and pyrrolidine ring is around ±90°. The study of electronic structures showed that the energy levels of frontier orbitals are determined mainly by C_(60). C_(60) acted as an electronic acceptor, whereas crown ether acted as an electronic donor, which implies that there exists intramolecular charge transfer effect in this molecule. The study of nonlinear optical properties implied that the hyperpolarizability of CFP can match that of p-nitroaniline. In the meantime, the hyperpolarizability properties of CFP could be influenced by the orientation of crown ether moiety.     

Theoretical studies of adsorption property on Ir_4/MgO and Ir_4/γ-Al_2O_3

The adsorption properties of atomic and molecular species on Ir4/MgO and Ir4/γ-Al2O3 have been systematically studied by means of planewave density functional theory(DFT)calculations using the periodic boundary conditions.The binding energies of these species were ordered as follows:H2O相似文献   

Plastics of the Future? The Impact of Biodegradable Polymers on the Environment and on Society

In recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in both research and the news. Biodegradable polymers like poly(lactic acid) are seen as a suitable alternative to commodity plastics. However, poly(lactic acid) is basically non‐degradable in seawater. Similarly, the degradation rate of other biodegradable polymers also crucially depends on the environments they end up in, such as soil or marine water, or when used in biomedical devices. In this Minireview, we show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.     

Separation of CO_2–N_2 using zeolite NaKA with high selectivity

The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO_2. Using the ion exchange method, different zeolites Na KA varying in K+content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO_2 and little N_2. On the zeolite Na KA with 14.7 at.% K+, the adsorption capacity for pure CO_2 is over 3.10 mmol g~(-1) and the CO_2–N_2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO_2–N_2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO_2 and N_2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO_2/N_2(20:80, v/v). If the pressure has been increased higher than 0.1 MPa, CO_2 would break through the bed much slower than N_2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.     

Li4SiO4对CO2捕集性能的实验研究

以Li₂CO₃和SiO₂为原料,通过高温固相合成法合成了CO₂捕集剂Li₄SiO₄,并用X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)对所合成的材料在CO₂捕集前后的晶相变化以及微观结构进行了表征。通过热重分析仪(TGA)研究了Li₄SiO₄材料吸附CO₂的性能,并在小型热态实验台架上进行了CO₂热态捕集实验。实验结果表明,Li₄SiO₄对CO₂的捕集性能受Li₄SiO₄合成温度、CO₂的吸附温度以及气体中CO₂含量的影响,在700 ℃下制得的Li₄SiO₄具有最佳的CO₂吸附特性,最大吸附增量可达34%。Li₄SiO₄的吸附能力随着CO₂含量和吸附时间的增加而增加,当CO₂浓度分别为75%、67%、60%时,700 ℃ Li₄SiO₄对CO₂最大吸附量分别可达6.68 mmol/g、3.37 mmol/g、2.02 mmol/g (理论量8.33 mmol/g)。     

[CuO-ZnO-Al2O3]/[HZSM-5]核壳双功能催化剂的制备、结构及其CO2+H2直接合成二甲醚反应性能

利用水热合成法制备了一系列不同晶化时间的核壳结构双功能催化剂[CuO-ZnO-Al₂O₃]/[HZSM-5],通过X射线衍射(XRD)、扫描电镜(SEM)和能量分散谱(EDS)对催化剂结构进行了表征,并考察了核壳催化剂CO₂加氢直接合成二甲醚的反应性能。结果表明,通过水热合成法可在甲醇合成催化剂CuO-ZnO-Al₂O₃表面包覆一层完整的HZSM-5分子筛膜,形成核壳结构,并且调节晶化时间可以控制分子筛晶粒尺寸及膜厚。与物理混合法制备的传统双功能催化剂相比,核壳结构催化剂合成二甲醚的选择性显著提高,其中晶化时间为3d的催化剂反应性能最为理想,CO₂转化率为38.9%,二甲醚选择性达到77.0%。     

CO_2在三聚氰胺酚醛纤维上的吸附分离

以三聚氰胺、间苯三酚和甲醛为原料,通过水热缩聚反应合成了三聚氰胺酚醛纤维(PMF),考察了温度对PMF合成的影响。以扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N_2吸脱附和傅里叶变换红外(FT-IR)光谱等表征了PMF的形貌和结构,并采用体积法测定不同温度下CO_2和N_2在PMF上的单组分吸附平衡等温线。结果表明,在393 K下合成的PMF具有较大的比表面积(64 m2/g)和较高的CO_2吸附量(1.83 mmol/g,298 K、118 k Pa)。穿透柱实验表明,在298 K、200-600 k Pa,CO_2-N_2混合气在PMF上均可实现有效分离。将PMF在873 K下,N_2、H2及水蒸气等多种气氛中进行后处理,其比表面积和微孔孔容均显著增加,其中,在15%H_2O气氛中处理后,样品CO_2吸附量提高至2.83 mmol/g(298 K、118 k Pa)。     

氨基修饰的金属有机框架Cu_3(BTC)_2的制备及其CO_2吸附性能研究

首先制备了嫁接氨基的均苯三甲酸,同时以其为原料通过溶剂热法合成了金属有机框架材料Cu_3(NH_2BTC)_2,利用XRD、N_2吸附-脱附、热重、红外、原位红外分析等表征手段对吸附剂进行了表征,并通过固定床测量穿透曲线的方法研究其CO_2吸附性能。结果表明,氨基被成功引入Cu_3(BTC)_2骨架中。氨基修饰的Cu_3(BTC)_2对CO_2有着较高的吸附容量,在10 kPa,50℃的条件下CO_2吸附量为1.41 mmol/g,这源于材料对于CO_2同时存在着物理吸附和化学吸附。     

CaO对Cu-ZnO-ZrO_2催化CO_2加H_2合成甲醇性能影响

用CaO作为改性助剂,采用并流共沉淀法制备了CuO∶ZnO∶ZrO_2为5∶4∶1(物质的量比),CaO添加量为0、1%、2%、4%、8%、16%(摩尔分数)的六组催化剂。用X射线衍射(XRD)、微商热重(TG-DTG)、傅里叶红外(FT-IR)、N2吸附脱附(BET)、X射线光电子能谱(XPS)、氢气程序升温还原(H_2-TPR)、CO_2程序升温脱附(CO_2-TPD)、NH_3程序升温脱附(NH_3-TPD)对催化剂进行了表征。用自制固定床评价了催化剂活性。结果表明,添加CaO后,催化剂路易斯酸性和表面碱性增强;催化剂母体中高温碳酸盐含量增加,热稳定性增强,CuO颗粒粒径变小,Cu-Zn协同作用增强,Cu比表面积增大,分散性变好。催化剂活性受到表面酸碱性、铜比表面积、Cu-Zn协同作用和铜分散性共同影响。当CaO为2%时,铜比表面积为79.3 m2/g、铜分散度为34.8%、CO_2转化率为24.55%、甲醇选择性为19.01%、甲醇收率为0.044 g/(gcat·h),催化剂活性最好。过量CaO占据催化剂孔道和覆盖表面活性位,使催化剂路易斯酸性和表面碱性过强,CuO与H_2有效接触减少,CO_2难以脱附,催化活性下降。因此,适量CaO(2%)添加可促进CO_2加氢反应合成甲醇。     

不同有机胺修饰MCM-41的CO2吸附性能和热稳定性

将乙二胺(EDA,60 g/mol)、四乙烯五胺(TEPA,189 g/mol)和两种聚乙烯亚胺600(PEI600g/mol; PEI1800g/mol)分别负载在MCM-41上制备氨基功能化介孔材料,研究其对CO₂的吸附性能和热稳定性.结果表明,除了EDA-MCM41,其他三种材料随着胺分子量增大CO₂吸附性能下降,但是热稳定性却有所提高,其中,TEPA-MCM41的吸附容量最大,达到2.7 mmol/g.同时发现,乙二胺在制备过程中随溶剂挥发而难以完全负载在MCM-41上.在纯N₂气氛和再生温度100 ℃条件下,经10次循环实验后,TEPA-MCM41的吸附能力下降了7.4%,而PEI600-MCM41和PEI1800-MCM41吸附能力保持不变,且质量变化在1%以内,表现出良好的再生稳定性.采用80%CO₂/20%N₂对吸附饱和的材料进行再生,四种材料的再生温度将提高到160 ℃以上,高分子量PEI600-MCM41和PEI1800-MCM41相比于TEPA-MCM41具有更好的热稳定性.     

CH_4和CO_2在油页岩中矿物质结构内部吸附的分子模拟

利用Materials Studio2017模拟软件构建了蒙脱石、高岭石、方解石和生石膏四种矿物质分子模型。采用巨正则蒙特卡洛(GCMC)方法和分子动力学(MD)方法对四种模型的吸附量和吸附热进行了模拟计算。研究表明,相同温度和压力条件下四种矿物质对CH_4和CO_2分子吸附量大小为:蒙脱石高岭石生石膏方解石;CH_4和CO_2分子的单组分吸附量随压力的增大而增大,两种气体吸附均符合Langmuir吸附规律;四种矿物质对CH_4和CO_2分子的等量吸附热均小于42 k J/mol,即为物理吸附;随着温度的升高,CH_4和CO_2分子的吸附量和吸附热均减小,且CH_4和CO_2分子的等量吸附热和等温吸附量之间呈良好的正相关。     

温和条件下CO2为原料电合成碳酸二甲酯

常温常压下, 研究了以CO₂和甲醇为原料电合成碳酸二甲酯的反应. 在四乙基溴化铵为支持电解质的乙腈溶液中, 通过恒电流电解得到了唯一的产物碳酸二甲酯. 为了优化电解条件, 分别考察了工作电极、电流密度、支持电解质、通电量以及电解前后加入甲醇顺序的不同等因素对该反应的影响. 以铜为工作电极, 石墨为对电极, 在17 mA•cm^－2的电流密度下恒电流电解, 当通过2 F•mol^－1的电量后, 碳酸二甲酯的产率可达74%, 大大高于文献报道值.     

In[NC5H3(CO2)2](OH2)F: A new layered indium-organic framework material (NC5H3(CO2)2=2,6-pyridinedicarboxylate)

A new layered indium-organic framework material, In[NC₅H₃(CO₂)₂](OH₂)F has been synthesized by a hydrothermal reaction using In₂O₃, NH₄F, 2,6-NC₅H₃(CO₂H)₂ (2,6-pyridinedicarboxylic acid), HF, and water at 200 °C. Single-crystal X-ray diffraction was used to determine the structure of the reported material. In[NC₅H₃(CO₂)₂](OH₂)F has a novel layered structure consisting of InO₅NF polyhedra and the pyridinedicarboxylate organic linker. Detailed structural analyses with full characterization including infrared spectrum, thermogravimetric analysis, elemental analysis, exchange reactions for the coordinated water molecule, and gas adsorption experiments are reported.