双金属功能化的MOF-74合成及气体吸附性能

采用一步合成法制备了在无机构造单元金属节点上同时具有比例可调的Mn（Ⅱ）和Co（Ⅱ）的双金属MOF-74网络结构。经双金属功能化的单晶材料保持了与单金属MOF-74一致的结构及孔道,且两种金属大致均匀分布于晶格中。相对于Mn（Ⅱ）,Co（Ⅱ）在合成MOF-74的过程中具有更快的配位及结晶速率,使得其在晶体中的比例高于反应溶液。双金属在同一框架结构内的配位促进了更多晶体内部局部缺陷的产生,使得Mn_0.78Co_1.22-MOF-74的比表面积相对于单金属的MOF-74材料有10%左右的提升。     

双金属MOF-74-CoMn催化剂的制备及其CO选择性催化还原技术应用

采用水热法成功地合成了不同比例的双金属MOF-74-CoMn催化剂，并成功用于以CO为还原剂的选择性催化还原脱硝（CO-SCR）反应.实验结果表明，双金属MOF-74-CoMn催化剂的NO_x转化率普遍高于单金属MOF-74-Co催化剂，且反应温度窗口更宽，其中，MOF-74-Co1Mn2的NO_x转化率最高，在175~275 ℃的温度范围内接近100%.进而，通过X射线粉末衍射（XRD），热重分析（TGA），扫描电镜（SEM），N₂吸附/脱附，X-射线光电子光谱（XPS），氢气程序升温还原性能测试（H₂-TPR）和原位红外光谱（FTIR）技术对双金属MOF-74-CoMn催化剂进行了表征和分析，发现金属Co、Mn的协同作用可以促进不饱和金属位点和氧空位的形成，从而提高CO选择性催化还原反应（CO-SCR）的效率.     

气相色谱法研究配位化合物的热稳定性 ⅩⅧ.配位CN~-的活化加氢

根据一系列金属(Cr、Mn、Fe、Co、Ni、Cu、Zn、Ag、Sn、La)的六氰合铁(Ⅱ)、(Ⅲ)酸盐在H_2气氛中热分解时所发生的CN~-加氢反应,从晶体结构和电子结构两方面探讨了双金属双端配位对CN~-的活化作用和CN~-的加氢反应机理。研究了CN~-的活化程度与配位金属离子的还原电位及d电子组态之间的关系。     

MOF-74及其复合物:多样合成与广泛应用

MOF-74具有高密度裸露的金属位点、可调的一维孔道及高热稳定性等优点,引起了科研工作者的广泛关注与深入探索。本综述主要从以下三个方面对MOF-74的发展状况进行概括:(1)着重介绍了MOF-74及其异构体的结构及组装方法(溶剂热法、常温法、微波辅助法、干凝胶法等),此外还讨论了反应溶剂、辅助配体、调节剂等因素对目标化合物的影响;(2)考虑到复合材料之间的协同作用,还对MOF-74基复合材料的发展现状进行概括,包括材料的构筑类型及典型的合成方法;(3)进一步讨论了MOF-74具有的特殊属性如孔道性、路易斯酸碱位点、结构稳定性以及复合材料的协同性能,以及MOF-74基材料在催化、分离、检测、吸附、能量储存等各个领域广泛的应用前景。最后还对新型MOF-74异构体材料的构建提出了合理的想法。     

蒸气辅助合成PCN-6(M)双金属有机框架材料及其CH_(4)和CO_(2)吸附性能北大核心CSCD

以PCN-6(Cu_(3)TATB_(2))为母体材料,Co、Fe、Mn、Zn和Ni为第2种金属,将蒸气辅助法应用于双金属有机框架材料(MOFs)的合成中,并成功制备出PCN-6(M)(M=Co/Fe/Mn/Zn/Ni)系列双金属材料,采用粉末X射线衍射仪(PXRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、电感耦合等离子发射光谱仪(ICP-OES)和气体吸附等技术手段对合成的材料进行了结构、形貌、组成和性能的表征,结果表明制备的PCN-6(M)系列双金属材料的PXRD衍射峰和形貌与母体材料PCN-6一致,交换的金属在材料中分布均匀,交换量(质量分数)分别为Co:12.1%,Fe:22.0%,Mn:16.1%,Zn:17.5%,Ni:16.8%,远高于相同条件下溶剂热法的金属交换量(5%左右),在气体吸附性能方面,PCN-6(Zn)、PCN-6(Ni)和PCN-6(Co)这3种双金属材料对CH_(4)和CO_(2)的吸附能力优于母体材料,理想吸附溶液理论(IAST)计算表明,PCN-6(Fe)对CO_(2)/CH_(4)的吸附选择性优于母体材料。通过蒸气辅助法制备双金属MOFs材料,可以提高金属的交换量并改变MOFs材料对不同气体分子的亲合力,进而提高材料对气体的吸附性能和选择性。蒸气辅助法为双金属MOFs材料的制备提供了新的思路,且有望用应于其它材料的制备中。     

气相色谱法研究配位化合物的热稳定性XVIII: 配位CN离子的活化加氢

根据一系列金属(Cr、Mn、Fe、Co、Ni、Cu、Zn、Ag、Sn、La)的六氰合铁(II)、(III)酸盐在H2气分中热分解时所发生的CN^-加氢反应,从晶体结构和电子结构两方面探讨了双金属双端配位对CN^-的活化作用和CN^-的加氢反应机理.研究了CN^-的活化程度与配位金属离子的还原电位及d电子组态之间的关系.     

Pd/Co双金属纳米颗粒的制备及催化制氢性能

采用聚乙烯吡咯烷酮(PVP)保护的化学共还原法制备了Pd/Co双金属纳米颗粒,研究了PVP及还原剂(NaBH4)的用量、金属盐浓度、金属比例等对Pd/Co双金属纳米颗粒催化NaBH4制氢性能的影响.透射电子显微镜(TEM)的结果表明,所制备的Pd/Co双金属纳米颗粒的平均粒径在1.5-2.8 nm之间. Pd/Co双金属纳米颗粒(BNPs)的催化活性远高于Pd与Co单金属纳米颗粒的活性;当Pd/Co的理论原子比为1/9时,双金属纳米颗粒的催化活性最高可达15570 mol?mol-1?h-1(文中纳米颗粒的催化活性均为每摩尔Pd的活性).密度泛函理论(DFT)的计算结果表明, Pd 原子与Co原子之间发生电荷转移,使得 Pd 原子带负电而Co原子带正电,荷电的Pd和Co原子进而成为催化反应的活性中心.所制备的Pd/Co双金属纳米颗粒具有很好的催化耐久性,即使重复使用5次后,该催化剂仍具有较高的催化活性,且使用后的纳米颗粒催化剂也没有出现团聚现象.双金属纳米颗粒催化NaBH4水解反应的活化能约为54 kJ?mol-1.     

金刚烷胺邻香兰素Schiff碱过渡金属配合物的合成与表征

合成了金刚烷胺邻香兰素Sch iff碱配体(C18H23NO2,以L表示)与过渡金属的6种新的配合物[MC l2L](M=Mn(Ⅱ),Co(Ⅱ),N i(Ⅱ),Cu(Ⅱ),Zn(Ⅱ),Cd(Ⅱ)),用元素分析、摩尔电导、红外光谱和热重分析表征了配合物的结构;讨论了配体与中心金属离子的键合情况并推测了配合物的结构,每一中心金属离子与Sch iff碱配体中的酚羟基氧、甲氧基氧及2个氯离子发生配位,其配位数为4.     

两个Mn(Ⅱ)/Co(Ⅱ)配位聚合物的脲热合成、结构和荧光性质

通过脲热合成法合成了2个金属配位聚合物[Mn3(Hidc)3(DMI)2]n(1)(H3idc=4,5-咪唑二羧酸,DMI=1,3-二甲基-2-咪唑啉酮),[Co(tbip)(DMPU)]n(2)(H2tbip=5-叔丁基间苯二甲酸,DMPU=N,N-二甲基丙烯基脲)。通过元素分析、红外光谱、X射线粉末衍射、单晶X射线衍射等对配合物进行了结构表征。结果表明:配合物1属单斜晶系,空间群为P21/n。该配合物以DMI为模板剂,通过H3idc与Mn(Ⅱ)构筑成三维四方孔道结构,DMI填充在孔道中。配合物2属单斜晶系,空间群为P21/c。该配合物以DMPU为模板剂,通过H_2tbip与Co(Ⅱ)构筑成二维网状结构,DMPU分子通过与Co(Ⅱ)配位填充在网格中。固体荧光性能测试表明配合物1在462 nm处存在较强的荧光发射峰,说明具有良好的蓝光性质。     

配位环境可调的Cu单原子的合成及催化加氢性能研究※

具有可控配位环境的高催化活性和选择性的稳定单金属位点催化剂的合成仍然具有挑战性. 本工作采用阳离子交换策略合成了两种具有不同配位结构的Cu单原子催化材料. 该策略主要依赖于硫化物的阴离子骨架和富含 N 的聚合物壳在高温退火过程中产生大量的S和N缺陷, 精确合成了富边缘S和N双修饰的单金属Cu位点催化材料. 在这两种材料, 一种Cu单原子具有硫(S)、氮(N)双配位, 一种Cu单原子只有单一的S配位. Cu中心原子的第一壳层配位数为4, Cu-S/N-C的结构为Cu-S₁N₃, Cu-S-C的结构为Cu-S₄. 实验表明, S、N双修饰的Cu单原子材料在室温下催化硝基苯加氢过程中表现出较高活性. 反应20 min后, 在Cu-S/N-C催化下, 硝基苯加氢转化率达到100%, 循环使用5次后活性未见显著下降. 该发现为调节中心金属配位环境以提高单原子催化材料的性能提供了一种可行的方法.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.