Wenliang Wang a,Wenli Zhao a,Haochun Zhang a,Xincheng Dou a,Haifeng Shi a,b,

近年来, Fenton反应由于其成本低,反应速度快,操作简单等优势受到了广泛的研究.传统的均相Fenton反应可通过H2O2氧化Fe2+产生具有强氧化性的羟基自由基,用于处理难降解的有机物.然而, Fenton反应存在两个主要问题,首先,在Fenton反应中需要加入大量的酸来维持酸性环境,以保证反应的最佳活性.其次, Fenton反应中铁离子不断流失并形成固体污泥,这严重影响了Fenton反应产生·OH的效率.目前,将光催化反应与非均相芬顿反应相结合是改善这些问题的有效方案.非均相光芬顿反应不仅能提高有机物降解的活性,而且通过光催化剂导带上的电子有效减少Fe3+的浸出和铁氢氧化物沉淀的产生.最近,作为一种可见光Fenton催化剂,α-Fe2O3可以在几乎中性的条件下发生光芬顿反应,这解决了在反应过程中需要随时调整PH值的问题.此外,光照条件下α-Fe2O3价带上的电子能跃迁至导带并将Fe3+还原成Fe2+,从而减少铁离子的损耗.然而,由于光生载流子复合率较高等问题,单一α-Fe2O3光催化剂的催化活性仍不理想.构建具有2D/2D结构的S型异质结可以缩短电子在界面间的传输距离,增大材料的活性位点,将光生电子-空穴在空间上分离,从而有效增强光生载流子的分离效率.因此,构建2D/2Dα-Fe2O3/Bi2WO6 S型异质结,并用于光芬顿反应有望进一步提高对有机污染物的降解效率.本文通过简易的水热法制备了具有2D/2D结构的α-Fe2O3/Bi2WO6 S型异质结光芬顿催化剂,并通过XRD、BET、TEM、XPS和UV-Vis等手段对催化剂的晶体结构、元素状态、微观结构、光学性质和化学组分进行了表征.通过在可见光照射下降解甲基蓝(MB),考察了α-Fe2O3/Bi2WO6的光芬顿催化活性.结果表明,由于光催化反应与Fenton反应的协同作用,α-Fe2O3/Bi2WO6表现出了明显增强的光-Fenton催化活性,最佳比例的α-Fe2O3/Bi2WO6的活性分别是单一α-Fe2O3和Bi2WO6的11.06倍和3.29倍.本文将光催化反应与Fenton反应相结合,一方面,光催化反应对Fe3+的还原有促进作用,提高了Fe2+的浓度,从而提升羟基自由基的产量;另一方面, Fenton反应对α-Fe2O3/Bi2WO6中电子的利用阻止了光生载流子的复合,进一步提高了光催化降解效率.此外,由于二维纳米片之间具有更大的接触面积, 2D/2D异质结可以缩短电荷传输时间和距离,促进了光生电子-空穴的分离.同时,具有较大比表面积的2D/2D材料可以在催化剂表面提供大量用于有机物氧化分解的活性位点.而S型异质结的构建不但促进了界面电荷的转移和分离,还能维持最佳的电荷氧化还原电位,这都提升了催化剂的光芬顿催化活性.总之,本文为合成可高效降解有机污染物的非均相光-芬顿催化剂提供了新的思路.     

Wenhua Xue a,Wenxi Chang a,Xiaoyun Hu b,Jun Fan a,#, Enzhou Liu a,

正a School of Chemical Engineering, Northwest University, Xi’an 710069, Shaanxi, China b School of Physics, Northwest University, Xi’an 710069, Shaanxi, China     

Zongpeng Wang a,b, Zhiping Lin a,c, Shijie Shen a,c, Wenwu Zhong a,c,*, Shaowen Cao b,#

伴随着人类文明的快速发展,一些危机慢慢显露出来,例如能源危机、环境污染和全球变暖.2019年5月11日, Mauna Loa天文台报告,大气中的二氧化碳水平超过415 ppm,达到人类历史上的最高记录,欧盟随后于2019年11月宣布了气候紧急状态.因此,绿色能源技术已成为迫切需求,以减少化石燃料的使用,并减少污染物的产生.光催化是直接利用太阳能的技术,可以应用于水分解产氢、CO2还原、降解有机污染物、促进有机物合成等,是解决能源和环境问题的最有前途的技术之一.光催化剂是光催化技术的核心.目前,许多半导体材料可作为光催化剂,并已被充分地研究,例如TiO2、Cd S、ZnO、Bi VO4和C3N4等.然而,单一的半导体材料具有一些缺点,阻碍了它们的实际应用.其中,限制这些半导体材料光催化活性的一个关键问题是,光生电子–空穴对容易快速复合而不是参与光催化反应.例如, ZnO中激子的寿命估计仅为数百皮秒,大多数激子来不及参与到氧化还原反应中.为了抑制电子-空穴对的复合,需要应用特殊的策略.构建异质结光催化材料已成为最有前途的方法之一.通常,可以根据相邻材料的能带结构,将异质结分为以下几种类型:PN型异质结, II型异质结, Schottky型异质结和S型异质结.以上异质结大都是由两种半导体材料复合而形成的.除此之外,还可以根据形成异质结的特殊材料,补充两种特殊的异质结类型,即晶面异质结和石墨烯基异质结.晶面异质结是由同一材料,由于暴露不同的晶面而形成的.石墨烯具有独特的能带结构、极大的比表面积及优良的导电性,可以与其他半导体形成各种类型的异质结.这些异质结材料能有效抑制电子-空穴对的复合,从而提高材料整体的光催化活性,也已成为光催化剂家族的重要分支.本文详细介绍了以上各种类型的异质结光催化剂的最新进展,概述了实现高性能异质结光催化剂的基本策略,并对异质结光催化剂未来发展方向进行了一些探讨.     

Chengying Guo a,Yanmei Shi a,Siyu Lu c,Yifu Yu a,*, Bin Zhang a,b,#

电催化水分解产氢作为一种有前途的制氢技术被全世界研究者广泛关注.然而,此领域仍然缺少一种高效、无污染的催化剂,以降低能耗,提升反应动力学,进而推进电解水的实际应用.近年来研究发现,具有短程有序、长程无序特征的非晶纳米材料在电解水领域表现出极其优异的性能.有趣的是,固有的无序结构赋予了非晶纳米材料丰富的高活性位点.鉴于此,本文综述了非晶纳米材料的制备策略以及表征方法,并且对其高活性来源进行了系统地分析.此外,本文通过分析近几十年的研究成果指出了非晶纳米材料在电解水领域面临的挑战和应用前景.非晶纳米材料的合成方法主要分为两类:直接合成和间接合成.直接合成主要包括:电沉积、光化学金属-有机沉积、气溶胶-喷雾辅助法、反胶束溶胶-凝胶法、水热法、共沉淀法和氧化还原法.其中,气溶胶-喷雾辅助技术可以通过控制母液中金属离子的浓度精准地控制非晶纳米材料中各种金属元素的组成,从而有目的地调控并优化催化活性.间接合成主要分为原位转化和非原位转化.原位转化是指晶体材料在反应过程中表面会原位转化为非晶结构作为反应的真实活性物质.非原位转化是指当纳米材料尺度非常小时,高表面能将会破坏材料的结晶度得到非晶材料.另外,非晶材料长程无序的特点给其表征带来极大挑战.目前,对于非晶材料表征的一般流程是:首先通过X射线粉末衍射确定非晶结构,并通过透射电子显微镜以及扫描电子显微镜探索其形貌结构;再通过选区电子衍射以及高角度环形暗场扫描透射电子显微镜进一步确定非晶结构;然后,通过能谱、电感耦合等离子体发射光谱和X射线光电子能谱分析其化学组成及化学态;最后,采用拉曼光谱和同步辐射数据提供晶体结构信息.本文对非晶纳米材料高活性的起源进行了探究.在电解水领域,非晶纳米材料通常表现出优于晶体材料的性能.优异的活性与活性位点数量的增多以及活性位点活性的提升有关:(1)非晶纳米材料具有长程无序的特征,可以暴露更多活性位点,并且其表面存在的大量悬挂键也可以作为活性位点;(2)非晶纳米材料的活性位点可以拓展至催化剂体相内部,大幅提升了活性位点数量;(3)非晶纳米材料结构灵活性高,活性位点在催化反应过程中可以转变成任意形状,提升了活性位点的活性;(4)非晶纳米材料的高韧性和应变能力赋予其较高的稳定性.非晶纳米材料已广泛应用于电解水领域,但仍然存在一些问题:(1)非晶纳米材料由于原子级结构不确定,其电催化机理很难探究;(2)理论模拟作为研究电化学反应途径的有力工具很难应用于非晶纳米材料的研究;(3)随着无序程度的增加,活性位点数量和活性逐渐增加,但电导率逐渐下降.尽管如此,由于非晶纳米材料结构灵活性高和自重组能力快速,人们对其在电解水领域的研究兴趣越来越大,并且该领域显示出良好的应用前景,高效非晶纳米材料的设计合成及其催化机理的研究将成为今后研究的重点.     

Hydroacridines XXV [1]. First Synthesis of (4aα,8aα,9aβ,10aβ)-Tetradecahydroacridine and New Syntheses of (4aα,8aα,9aα,10aβ)- and (4aα,8aβ,9aα,10aβ)-Tetradecahydroacridine

Summary. On heating in dry DMSO, in the presence of potassium t-butoxide, the N-nitrosamine of (4aα,8aβ,9aβ,10aα)-tetradecahydroacridine is completely converted into the N-nitrosamine of (4aα,8aα,9aα,10aβ)-tetradecahydroacridine. Under similar conditions, the N-nitrosamine of (4aα,8aα,9aβ,10aα)-tetradecahydroacridine yields a ternary equilibrium mixture containing itself (19%), and the N-nitrosamines of (4aα,8aβ,9aα,10aβ)-tetradecahydroacridine (46%) and the so far unknown (4aα,8aα,9aβ,10aβ)-tetradecahydroacridine (35%). The resulting N-nitrosamines can be smoothly denitrosated to the corresponding secondary amines.     

Molecular structure of methyl 1-isopropenyl-5a,5b,8,8,14a-pentamethyl-1,2,3,3a,4,5,5a,5b,6,7,7a,8,9,14,14a,14b,15,16,16a,16b-icosahydrocyclopenta[7,8] phenanthro[2,1-b]carbazole-3a-carboxylate

The molecular and crystal structure of methyl 1-isopropenyl-5a,5b,8,8,14a-pentamethyl-1,2,3,3a,4,5,5a,5b, 6,7,7a,8,9,14,14a,14b,15,16,16a,16b-icosahydrocyclopenta[7,8]phenenthro[2,1-b]carbazole-3a-carboxylate is determined. Compound C₃₇H₅₁NO₂ II crystallizes in the C2 chiral space group: a = 27.0380(5) ?, b = 7.9817(15) ?, c = 18.1980(3) ?, β = 123.580(3)°.     

Alizarin-s,a reagent for thorium. a gravimetric,colorimetric, and spectrophotometric study

The claim of Beck in the use of alizarin-S for separating cerite earths from thorium could not be substantiated. Detailed conditions for estimating from 0.0095 to 6.3 mg of thorium dioxide in 50 ml of solution by the method of Rao and Murthy are described. The absorption characteristics of alizarin-S and its-thorium complex have been studied in their dependance on pH. The thorium complex has been shown by adopting different optical methods to correspond to Th-Al-S (a stoichiometric ratio of 1:1) which is also confirmed from gravimetric analyses. The dissociation coefficient of the complex at pH 2.7 has been computed to be less than 1.10^-8.     

Lignin,a biomass crosslinker,in a shape memory polycaprolactone network

This work reports a new direction of natural lignin valorization, which utilizes lignin to produce crosslinked polycaprolactone (PCL) via a straightforward synthesis. Lignin's hydroxyl groups of its multibranched phenolic structure allow lignin to serve as crosslinkers, whereas the aromatic groups serve as hard segments. The modified natural lignin containing alkene terminals is crosslinked with a thiol‐terminal PCL via Ru‐catalyzed photoredox thiol‐ene reaction. The high rate of gel contents measured for all crosslinked polymers, with the least being 84% of gel content, indicates efficient crosslinking. The prepared flat rectangular shape lignin‐crosslinked PCL sample demonstrates rapid thermal responsive shape memory behavior at 10 °C and 80 °C showing interconversion between a permanent and temporary shape. The melting temperature of the lignin‐crosslinked PCL is tunable by varying the percent weight of lignin. The 11, 21, and 30 wt % lignin demonstrated T_m of 42 °C, 35 °C, and 26 °C, respectively. The role of lignin as a crosslinker presented in this work suggests that lignin can serve as an efficient biomass‐based functional additive to polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2121–2130     

Dysobinin,a tetranortriterpenoid

The planar furan ring in the title compound (6β‐acetoxy­aza­dirone, C₃₀H₃₈O₆) is twisted with respect to the steroid D ring. The crystal structure is stabilized by C—H?O hydrogen bonds and van der Waals interactions.     

1,4,4a,10b-Tetrahydro-N,N-dimethyl-4-phenanthridinamines and 1,4,4a,5,6,10b-hexahydro-N,N-dimethyl-4-phenanthridinamines

Synthetic procedures to prepare the title compounds are described. Diels-Alder cycloaddition of β-nitrostyrene derivatives 5 to N,N-dimethyl-1,3-butadien-1-amine, 6 , gave 5-aryl-N,N-dimethyl-6-nitro-2-cyclohexen-1-amines 7. Reduction of 7 with zinc in acetic acid gave the diamino derivatives 8 . Schotten-Baumann acylation of 8 gave amides 9 . Treatment of 8 with alkyl isocyanates gave the aminourea derivatives 10 . Bischler-Napieralski cyclodehydration procudure of 9 and 10 gave 1,4,4a,10b-tetrahydrophenanthridinamines 3 and N⁶-alkyl-1,4,4a,10b-tetrahydro-N⁴,N⁴-dimethyl-4,6-phenanthridinediamines 11 , respectively. Condensation of diamines 8 with aryl aldehydes under azeotropic conditions gave imines 12 which on treatment with acids yielded 6-aryl-1,4,4a,5,6,10b-hexahydro-N,N-dimethyl-4-phenanthridinamines 4 . The stereochemistry of these materials is assigned from the proton magnetic resonance studies.     

An efficient catalytic method for the synthesis of 2,7-dialkyl-2,3a,5a,7,8a,10a-hexaazaperhydropyrenes

An efficient method for the synthesis of 2,7-dialkyl-2,3a,5a,7,8a,10a-hexaazaperhydropyrenes in high yields (up to 95%) via the intermolecular cyclization of 1,4,5,8-tetraazadecalin with N,N-bis(methoxymethyl)-N-alkylamines in the presence of SmCl₃·6H₂O as the catalyst has been developed.     

Application of the Prigogine-Flory-Patterson theory part III. Mixtures of a bicyclic compound,benzene, cyclohexane,n-hexane with a cycloalkane,cyclohexene, a cycloalkadiene and benzene

The Prigogine-Flory-Patterson theory of liquid mixtures has been qpplied to the H _m ^E and V _m ^E for binary mixtures of a bicyclic compound, benzene, cyclohexane and n-hexane with a cycloalkane, cyclohexene, a cycloalkadiene and benzene. Furthermore the Prigogine-Flory theory has been used to predict activity coefficients at infinite dilution from the experimentally determined H _m ^E at 25°C for the mixtures cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene and benzene with a bicyclic compound. The predictions are compared to experimental results.     

(4aR,8aS,9aR,10aS)‐8a,9a‐Difluoro‐1,4,4a,5,8,8a,9,9a,10,10a‐decahydroanthracene‐4a,10a‐diol hemihydrate

The title compound, C₁₄H₁₈F₂O₂·0.5H₂O, a hemihydrate of a C_s‐symmetric unsaturated difluorodiol, crystallizes in the centrosymmetric space group P2/m (Z = 4). The asymmetric unit contains two crystallographically independent difluorodiol half‐molecules, occupying the mirror planes at (x, 0, z) and (x, , z), and half a molecule of water, lying on the twofold axis at (0, y, 0). Four difluorodiol molecules self‐assemble around each solvent water molecule via O—H...O hydrogen bonds in a near tetrahedral symmetry to generate a cylindrical column‐like architecture.     

Three Saponins, a Steroid, and a Flavanol Glycoside from Achyrantes aspera

Summary.  Three bisdesmosidic saponins, 20-hydroxyecdysone, and quercetin-3-O-β-D-galactoside were isolated from the methanol extract of the aerial parts of Achyranthes aspera L. (Amaranthaceae). Their structures were established on the basis of NMR spectroscopic analysis; the complete ¹H and ¹³C assignments of the compounds were achieved by means of 2D NMR studies. Received July 21, 1999. Accepted August 26, 1999