MIL-53(Al)衍生的Rh单原子催化剂在间氯硝基苯选择性加氢制间氯苯胺反应中的应用

卤代苯胺是化学工业中重要的中间体,主要用于制造药物、聚合物、染料等含氮化学品,用多相金属催化剂催化卤代硝基芳烃加氢制备卤代苯胺是一种高效,绿色和可持续发展的生产工艺.该过程需要选择性加氢硝基基团,同时避免卤素基团的脱卤副反应发生.然而,化学选择性加氢存在巨大的挑战,难点在于催化剂的精准设计,一方面要求具备对硝基基团合适的加氢能力,另一方面要阻止对卤素基团的脱卤副反应发生.基于此,研制高效多相金属催化剂用于卤代硝基芳烃选择性加氢制备卤代苯胺反应引起了高度关注.近年来,单原子金属催化剂受到越来越多的关注,并在卤代硝基芳烃选择性加氢制备卤代苯胺反应中显现出极大的潜力.本文通过在金属有机骨架材料MIL-53(Al)自组装的过程中将金属Rh原位嫁接其骨架结构中,继而通过限域热解的方法制备了Rh@Al2O3@C单原子催化剂,其在间氯硝基苯(m-CNB)加氢制间氯苯胺(m-CAN)反应中显现了高效催化选择性.球差校正高角度环形暗场模式的透射电镜,CO作为探针分子的红外光谱和X射线光电子能谱等结果发现,Rh是以单原子的形式均匀的分布在Al2O3上并被无定型碳包覆,且Rh化学价态呈正价.而27Al固体核磁共振与密度泛函理论计算的结果则进一步确定Al2O3@C载体中存在的五配位的Al物种(AlV)是锚定Rh单原子的主要位点,AlV的不饱和的配位结构可以有效地稳定Rh单原子,对形成Rh位点的单原子分散至关重要.在间氯硝基苯选择性加氢制间氯苯胺反应中,与等体积浸渍法制备的Rh/C和Rh/γ-Al2O3纳米催化剂相比,Rh@Al2O3@C单原子催化剂表现出优异催化性能:其在313 K,氢气压力为20 bar的温和条件下转换频率(TOF)高达2317 molm-CNB·molRh-1·h-1,优于已报道的多相金属催化剂,是目前的最高值.此外,该催化剂展现出极佳的稳定性能,经过五次循环后,该催化剂对m-CAN的选择性仍旧保持在98％左右.Rh@Al2O3@C单原子催化剂的优异催化性能源自于金属单原子结构的形成对于金属位点电子结构的有效调节,进而调控催化剂加氢性能并实现对加氢脱卤副反应的抑制;与此同时,Rh@Al2O3@C催化剂增进了酸位点的可及性,从而促进了其串联步骤中包含的脱水反应的发生,进而有效提高催化剂的反应活性.     

TiO2晶面依赖的Ir-TiOx相互作用对Ir/TiO2催化剂巴豆醛选择性加氢性能的影响

α,β-不饱和醇是一类重要的精细化学品,主要通过α,β-不饱和醛选择性加氢获得.由于α,β-不饱和醛分子中含有共轭的C=C键和C=O键,且后者键能更大,在热力学和动力学上均不利于C=O键的选择性加氢生成α,β-不饱和醇.因此,提高α,β-不饱和醛中C=O的加氢选择性是催化领域中一项挑战性的课题.巴豆醛属于典型的α,β-不饱和醛,研究其选择性加氢生成巴豆醇具有广泛的代表意义;Ir负载在具有还原性载体(如TiO2)上时,表现出很好的C=O加氢选择性,因此,成为近年来的研究热点.由于暴露不同晶面的TiO2具有不同的形貌和电子结构,因此研究Ir-TiO2相互作用的晶面依赖性及其对巴豆醛选择性加氢反应的影响具有重要意义.本文以分别暴露{101}、{100}和{001}晶面的锐钛矿TiO2纳米晶为载体,制备了负载型Ir/TiO2催化剂,系统研究了催化剂经过不同的预处理过程(在不同温度下H2还原和O2再氧化)后对巴豆醛的气相选择性加氢的性能.利用高分辨透射电镜、原位X射线光电子能谱和原位漫反射红外光谱及氨程序升温脱附等技术研究发现,预处理条件显著改变了Ir-TiOx的相互作用,包括Ir金属的几何、电子性质及催化剂表面酸性.这种相互作用与TiO2的暴露晶面密切相关,从而改变了不同Ir/TiO2催化剂上不同加氢反应行为.研究结果表明,经300℃预还原的Ir/TiO2-{101}催化剂催化性能最好,在80℃下初始反应速率为166.1 μmol g-Ir-1 s-1,巴豆醇的生成转化频率为0.022 s-1.与其他催化剂相比,Ir/TiO2-{101}催化剂表面Ir0浓度最高,表面酸度适中,因此表现出最佳的催化性能.同时Ir-TiOx界面在反应中的协同作用,对H2和巴豆醛分子中C=O键的吸附和活化起到了关键作用.然而当催化剂经过400℃的H2预还原后,由于产生了强的金属-载体相互作用使得TiOx对Ir粒子进行了包裹从而导致Ir-TiOx界面缺失,因而催化剂催化巴豆醛加氢性能降低.本文为理解金属-载体相互作用对巴豆醛选择性加氢反应的影响提供了新的见解,并为设计高性能α,β-不饱和醛选择性加氢催化剂提供了理论依据.     

Sarcaglarols A—D,Lindenane−Monoterpene Heterodimers from Sarcandra glabra Based on Molecular Networks

Sarcaglarols A—D ( 1 — 4 ), two pairs of lindenane?monoterpene heterodimers fused by a 1,2‐dioxane moiety, were discovered and isolated from the leaves of Sarcandra glabra guided by MS/MS molecular networking‐based strategy. Their planar structures, absolute configurations of basic skeleton and flexible polyhydric side chain were established by analysis of HRESIMS, NMR spectroscopic data, ECD spectrum, and the X‐ray diffraction study of isopropylidene derivatives. An intermolecular [2+2+2] cycloaddition may play a key role in the biosynthesis pathway of the 1,2‐dioxane moiety fused lindenane?monoterpene heterodimer skeleton, which can be recognized as the biogenetic precursors of our previous reported lindenane?normonoterpene conjugates. In addition, compounds 1 , 3 and 4 exhibited moderate inhibitory effects of lipid accumulation in free fatty acid‐exposed L02 cells.     

全无机卤化铅钙钛矿的结构、热力学稳定性和电子性质

有机-无机杂化卤化铅钙钛矿因具有独特的电子和光学特性,已经成为光电领域最有前途的材料。但是,有机-无机钙钛矿材料及器件稳定性差,限制了其实际应用。与杂化钙钛矿相比,全无机卤化物钙钛矿CsPbX₃(X=Cl,Br,I)显示出更强的热稳定性。全无机卤化物钙钛矿CsPbX₃具有多个晶型,在不同的温度下呈不同相结构。目前,关于CsPbX₃的结构和物理性质仍存在争议。本文我们针对三个晶相α-,β-和γ-CsPbX₃的结构,热力学稳定性和电子性质进行了全面的理论研究。第一性原理计算表明,从高温α相到低温β相,然后再到γ相的相变伴随着PbX₆八面体的畸变。零温形成能计算表明,γ相最稳定,这与实验中γ相为低温稳定相的结论一致。电子性质计算表明,所有CsPbX₃钙钛矿都表现出直接带隙性质,并且带隙值从α相到β相再到γ相逐渐增加。这是由于相变发生时,Pb-X成键强度逐渐减弱,使价带顶能量降低,进而带隙增加。在所有相中,α相结构中较强的Pb-X相互作用,导致了较强的带边色散,使其具有较小的载流子有效质量。     

An interlocked coordination cage based on aromatic amide ligands

An interlocked M_4 L_8 coordination cage was synthesized by coordination-driven self-assembly of palladium(Ⅱ) ions with aromatic amide bidentate ligands.The reaction of the ligand and the metal at 2:1 ratio led to the monomeric M_2 L_4 cage as the kinetic product,while the thermodynamic product M_4 L_8 cage was obtained by prolongating the reaction.This conve rsion and the interlocked structure was clearly revealed by using ~1 H NMR,mass spectrometry and X-ray crystallography.The driving force of interlocking was mainly attributed to the interactions(hydrogen bonding,aromatic stacking and electrostatic interaction) arising from the aptitude of flexibility of the amide ligand.     

Copper-cobalt-nickel oxide nanowire arrays on copper foams as self-standing anode materials for lithium ion batteries

Numerous scientists are in the pursuit of energy storage materials with high energy and high power density by assembly of electrochemically active materials into conductive scaffolds, owing to the emerging need for next-generation energy storage devices. In this architectures, the active materials bonded to the conductive scaffold can provide a robust and free-standing structure, which is crucial to the fabrication of materials with high gravimetric capacity. Thus, hierarchical copper-cobalt-nickel ternary oxide (CuCoNi-oxide) nanowire arrays grown from copper foam were successfully fabricated as free-standing anode materials for lithium ion batteries (LIBs). CuCoNi-oxide nanowire arrays could provide more active sites owing to the hyperbranched structure, leading to a better specific capacity of 1191 mAh/g, cycle performance of 73% retention in comparison to CuO nanowire structure, which exhibited a specific capacity of 1029 mAh/g and capacity retention of 43%, respectively.     

Three-dimensional porous photo-thermal fiber felt with salt-resistant property for high efficient solar distillation

The urgent need for fresh water resource is a public issue facing the world. Solar distillation for seawater desalination is a promising freshwater production method. Interfacial solar evaporation systems based on 2D photo-thermal membranes have been widely studied, but salt pollution is one of the main challenges for solar distillation. In order to solve this problem, a hydrophilic three-dimensional (3D) porous photo-thermal fiber felt (PFF) was obtained by one-step method, through a simple polydopamine (PDA) coating method with hydrophobic graphite felt as a substrate. The PFF had a good evaporation rate of 1.48 kg m^?2 h^-1 and its corresponding light-vapor conversion efficiency reached 87.4%. In addition, the PFF exhibited an excellent salt-resistant ability when applied to photo-thermal evaporation of high-salinity seawater with 10 wt% NaCl, owing to its intrinsic 3D macroporous structure for the migration circulation of salt ions. The development of the PFF offers a new route for the exploration of salt-resistant photo-thermal materials and is promising for the practical application of solar distillation.     

Dinitrile compound containing ethylene oxide moiety with enhanced solubility of lithium salts as electrolyte solvent for high-voltage lithium-ion batteries

A dinitrile compound containing ethylene oxide moiety (4,7-dioxa-1,10-decanedinitrile, NEON) is synthesized as an electrolyte solvent for high-voltage lithium-ion batteries. The introduction of ethylene oxide moiety into the conventional aprotic aliphatic dinitrile compounds improves the solubility of lithium hexafluorophosphate (LiPF₆) used commercially in the lithium-ion battery industry. The electrochemical performances of the NEON-based electrolyte (0.8 M LiPF₆?+?0.2 M lithium oxalyldifluoroborate in NEON:EC:DEC, v:v:v?=?1:1:1) are evaluated in graphite/Li, LiCoO₂/Li, and LiCoO₂/graphite cells. Half-cell tests show that the electrolyte exhibits significantly improved compatibility with graphite by the addition of vinylene carbonate and lithium oxalyldifluoroborate and excellent cycling stability with a capacity retention of 97 % after 50 cycles at a cutoff voltage of 4.4 V in LiCoO₂/Li cell. A comparative experiment in LiCoO₂/graphite full cells shows that the electrolyte (NEON:EC:DEC, v:v:v?=?1:1:1) exhibits improved cycling stability at 4.4 V compared with the electrolyte without NEON (EC:DEC, v:v?=?1:1), demonstrating that NEON has a great potential as an electrolyte solvent for the high-voltage application in lithium-ion batteries.