Zr-MOF空心纳米球固载离子液体对CO2环加成反应的催化性能

通过后合成修饰方法(PSM)构筑了空心纳米球(Void@UiO-66-Ⅰ)和实心块(UiO-66-Ⅰ) 2种形貌的季铵盐功能化UiO-66-NH₂(Zr), 得到兼具酸碱活性位点和氢键给体的新型功能化金属-有机框架材料. 通过一系列表征证明2种催化剂的成功合成, 并将它们用于催化转化CO₂和氧化苯乙烯的环加成反应. 由于Void@UiO-66-Ⅰ催化剂的季铵盐部分含有大量的羟基和卤素阴离子, 可以通过氢键和亲核攻击与环氧化合物连接, 诱导环氧化合物开环, 促使反应顺利进行, 且催化剂的中空结构有利于物质进出催化剂, 起到加快反应速率的作用, 使得该催化剂在CO₂与氧化苯乙烯环加成反应中表现出比实心块UiO-66-Ⅰ催化剂更好的催化性能. Void@UiO-66-Ⅰ催化剂在120 ℃, CO₂压力为1.2 MPa, 反应时间为6 h, 无溶剂和助催化剂的反应条件下, 碳酸苯乙烯酯的收率和选择性分别为85.5%和95%.     

吡啶-2-甲醛共价接枝UiO-66-NH2负载铁系催化剂的合成及催化乙烯齐聚性能

以金属有机骨架UiO-66-NH2和吡啶-2-甲醛为原料,经后合成修饰法,合成出吡啶-2-甲醛共价接枝UiO-66-NH2配体,然后利用吡啶-2-甲醛作为桥联基将FeCl2负载到UiO-66-NH2上,制备出一种新型吡啶-2-甲醛共价接枝UiO-66-NH2负载铁系催化剂。傅里叶红外变换光谱(FT-IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、电感耦合等离子体质谱(ICP)和氮气吸附-脱附等分析方法证实合成出产物的结构与理论设计的结构相符。在合成与表征的基础上,对其催化乙烯齐聚性能进行研究。实验结果表明,随反应温度和Al/Fe摩尔比升高,催化活性先升高后降低,丁烯选择性升高;随乙烯压力增加,催化活性持续升高,丁烯选择性降低。最佳反应条件下,该催化剂的活性可达6.43×104 g·(mol Fe·h)-1,丁烯的选择性高达91.01%以上。     

UiO-66-NH2接枝吡啶亚胺钴系催化剂的合成及催化乙烯齐聚性能

以金属有机骨架(MOFs)UiO-66-NH2和吡啶-2-甲醛为原料,采用后合成修饰法制备一种UiO-66-NH2接枝吡啶亚胺配体,然后以UiO-66-NH2接枝吡啶亚胺配体和CoCl2·6H2O为原料,经配合反应,合成出一种UiO-66-NH2接枝吡啶亚胺钴系催化剂.采用傅里叶红外变换光谱(FT-IR)、X射线衍射(...     

钯-高分子载体催化剂对糠醛加氢液相反应的研究

以弱碱性苯乙烯系阴离子交换树脂[D392,-NH₂,D382,-NHCH₃,D301R,-NH(CH₃)₂],强碱性苯乙烯系阴离子交换树脂[201×7DVB,-NH⁺(CH₃)₃]和弱碱性环氧系阴离子交换树脂(701,-NH₂)为载体制备了3种钯-高分子载体催化剂.考察了反应条件、高分子载体的种类、钯含量和催化剂用量对糠醛催化加氢生成四氢糠醇反应及催化性能的影响.在体积分数为50%的乙醇-水溶液和水中对糠醛常压液相加氢反应,钯-高分子载体(阴离子交换树脂D392,-NH₂,D382,-NHCH₃)催化剂均可使糠醛的加氢反应转化率达100%,生成四氢糠醇的选择性达98%以上,而用金属钯为催化剂的转化率达70%以上,选择性达97%以上.同时用XPS分析了高分子载体催化剂的结构与催化加氢反应性能的关系.     

氟改性UiO-66固载钼基过氧化物催化氧化含硫化合物

采用预修饰方法对UiO-66进行配体官能团改性, 通过引入—F调控UiO-66的表面亲疏水性质; 其次, 通过引入—NH₂在UiO-66骨架上锚定MoO(O₂)₂. 接触角测试表明, 氟的引入有效地提高了载体表面的疏水性; 热重分析证明, 氟修饰的UiO-66骨架上存在更多配体缺失, 从而有效提高了整体MOF骨架的Lewis酸性. 以二苯并噻吩(DBT)氧化为氧化脱硫模型反应, 过氧化氢异丙苯(CHP)为氧化剂, 采用正交实验考察了反应温度、 氧硫比及催化剂用量对催化性能的影响, 其中氧硫比是影响DBT转化率的决定性因素. 经过氟改性后的催化剂经过5次催化反应循环后其催化活性未见明显变化, 且骨架仍保持稳定.     

苯酚加氢制环己酮用高效Pd/MgAl-LDO@Al2O3催化剂的制备及性能研究

环己酮是合成尼龙等材料的重要中间体, 但苯酚直接加氢反应制备环己酮容易生成环己醇而降低收率. 采用原位生长策略制备Pd/MgAl-LDO@Al₂O₃催化剂, 并用于苯酚选择性加氢反应, 获得的催化剂在高底物比条件具有良好的催化性能, 相较于Pd/Al₂O₃催化剂, Pd/MgAl-LDO@Al₂O₃催化剂使苯酚转化率显著增加, 苯酚转化率在97%时环己酮选择性可达88%. 利用X射线衍射(XRD)、程序升温脱附(TPD)、高分辨透射电子显微镜(HRTEM)和X射线光电子能谱(XPS)等手段对催化剂结构进行表征发现在氧化铝上原位生长类水滑石结构能够优化催化剂孔结构并提高活性组分分散度, 且增加了载体表面碱位点的强度, 碱位点的存在影响了苯酚的吸附形式, 从而大幅增加环己酮的选择性. 此外, 当将Ni引入层状结构时, 通过NaBH₄的还原可获得PdNi合金结构. 动力学研究表明, 由于PdNi合金的形成, Pd/NiAl-LDO@Al₂O₃催化剂苯酚加氢反应的能垒低于Pd/MgAl-LDO@Al₂O₃, 同时合金结构导致环己酮选择性的明显降低.     

新型金属有机气凝胶的合成、 表征及气体吸附性能

利用高稳定性的UiO-66系列金属有机骨架多孔材料制备金属有机气凝胶材料, 制得的UiO-66系列金属有机气凝胶材料具有多级孔结构和较高的比表面积, 在气体吸附分离领域具有较大应用潜力. 气体吸附实验结果表明, UiO-66-NH₂金属有机气凝胶材料具有极佳的CO₂吸附性能和CO₂/CH₄分离性能, 通过理想吸附溶液理论计算得出其吸附选择性高达18.3.     

UiO-66-NH2/wood的设计构筑及高效去除水中微量重金属离子性能

矿山开采、 金属冶炼、 新型金属材料的发展以及城市供水系统老化所造成的重金属(铅、 镉、 汞、 砷、 铬、 铜及锌等)污染问题已日趋严重. 传统的水处理方法很难有效地去除低浓度的重金属污染物. 本文以天然木材为载体, 采用溶剂热合成法, 在木材三维孔道中原位合成UiO-66-NH₂金属有机框架材料(MOFs)纳米颗粒, 制备了UiO-66-NH₂/wood复合膜材料. 该复合膜材料对去除水中微量重金属离子(Hg²⁺, Cu²⁺)表现出优异的性能. 当处理速率为1.1×10² L?m^-2?h^-1时, 该复合膜材料去除水中微量重金属离子的效率仍可达到90%以上, 且处理后水中重金属离子含量低于国家饮用水标准. 这可归因于木材本身独特的三维孔道结构, 在提高水通量的同时, 还可以增加水溶液中重金属离子与MOFs颗粒的接触机会, 以及孔道内均匀分布的UiO-66-NH₂ MOFs颗粒中的—NH₂可以与重金属离子通过配位作用相结合. 该UiO-66-NH₂/wood复合膜材料还具有良好的重复利用性, 在连续6次循环使用后其去除效率无明显变化, 有望进行实际应用.     

Pd基多相催化剂上CO2加氢反应的研究进展

随着二氧化碳(CO₂)排放量的不断增加, 全球变暖和气候变化的加剧对人类的生存环境产生了巨大的影响. CO₂作为廉价、 可再生的碳氧资源, 将其转化为高附加值化学品是绿色化学及能源领域的重要研究课题之一, 受到广泛关注. Pd基催化剂由于具有优异的加氢能力以及良好的抗烧结、 抗毒化性能, 作为CO₂催化转化最有前途的催化剂被广泛应用和研究. 本文主要对Pd基催化剂上CO₂加氢制备HCOOH, CO, CH₄和甲醇等小分子能源化合物的研究进展进行综合评述, 重点关注Pd基催化剂上CO₂分子的吸附/活化位点、 催化剂的金属-载体强相互作用及表界面组成等对催化剂活性和选择性的影响以及催化反应机理.     

贫燃/富燃循环气氛下原位活化Pd负载钙钛矿催化剂促进NOx还原消除

稀燃发动机通过提高空燃比来改善燃油经济性,减少CO2排放.但由于空燃比较高,稀燃发动机尾气中的NO_x无法通过传统的三效催化技术有效消除.为了解决这一问题,适用于稀燃条件的NO_x储存还原(NSR)技术得到了开发和应用.传统的NSR催化剂以贵金属Pt作为其氧化还原活性中心.Pt基催化剂具有较高的NO_x消除活性,然而热稳定性差,高温下易团聚失活.据报道,Pd具有比Pt更好的热稳定性和抗硫性,且能够在更低的温度下活化还原剂,促进NO_x还原.但De-NO_x反应中的活性Pd物种至今仍无定论,这对设计高效的Pd基NSR催化剂提出了挑战.本文设计制备了具有高活性的Pd负载型钙钛矿催化剂(Pd-La_0.7Sr_0.3MnO₃).其中钙钛矿组分的加入提高了Pd基催化剂的NO氧化能力和热稳定性,并提供了可用于NO_x储存的碱性位点.通过调节金属-载体相互作用,使Pd催化剂在NSR反应气氛下发生了自活化现象,活化后催化剂的NO_x消除活性由56.1%提高到90.1%,同时副产物N2O的选择性降低.XRD、XAFS和XPS等表征结果显示,在反应气氛下催化剂中的Pd²⁺被部分还原为高活性的Pd0物种.相较于Pd²⁺,Pd0表现出更强的活化C3H6的性能,从而提高了催化剂在富燃阶段的NO_x还原效率.结合XPS、CO化学吸附和动力学的实验结果,计算得出Pd0位点的NO_x还原速率是Pd²⁺位点的8倍,从实验现象和动力学计算两个角度分别证明Pd0物种具有更优异的NO_x还原活性.然而,Pd0物种的生成需要适当强度的金属-载体相互作用.通过与传统的Pd/BaO/Al₂O₃催化剂进行对比研究,发现金属-载体相互作用过强时,在富燃阶段Pd2+物种难以被还原,且还原得到的Pd0物种并不稳定,会在随后的贫燃阶段被快速重新氧化为Pd²⁺.强相互作用虽然可以降低Pd物种粒径,提高Pd的分散度,但由于无法产生高活性的Pd0物种,催化剂的NO_x消除性能显著降低.此外,相较于传统的Pd/BaO/Al₂O₃和Pt/BaO/Al₂O₃催化剂,Pd负载型钙钛矿催化剂具有更为优异的NO氧化能力,且储存位碱性适中,因而表现出更强的抗H₂O、CO₂和SO₂的性能,具有良好的应用前景.本文的结果说明了金属-载体相互作用对催化剂活性的显著影响,同时也为理解和设计应用于动态氧化/还原气氛的金属催化剂提供了新的思路.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.