Nitrogen ligands in two-dimensional covalent organic frameworks for metal catalysis

We introduced bipyridine ligands into a series of two‐dimensional （2D） covalent organic frame‐works （COFs） using 2,2’‐bipyridine‐5,5’‐dicarbaldehyde （2,2’‐BPyDCA） as a component in the mixed building blocks. The framework of the COFs was formed by the linkage of imine groups. The ligand content in the COFs was synthetically tuned by the content of 2,2’‐BPyDCA, and thus the amount of metal, palladium（II） acetate, bonded to the nitrogen ligands could be manipulated. Both the bipyri‐dine ligands and imine groups can coordinate with Pd（II） ions, but the loading position can be var‐ied, with one ligand favoring binding in the space between adjacent COFs’ layers and the other lig‐and favoring binding within the pores of the COFs. The Pd（II）‐loaded COFs exhibited good catalytic activity for the Heck reaction.

Metal-organic frameworks with mixed-ligands strategy as heterogeneous nucleation center to assist crystallization for efficient and stable perovskite solar cells

Deep-level defects and random oriented configuration in perovskite crystallization process would cause the nonradiative recombination and further affect the performance of perovskite solar cells(PSCs).Herein,two metal-organic frameworks(MOFs)with tunable Lewis-base passivation sites have been constructed(Cd-Httb and Cd-Httb-BDC,Httb=5-(4-(1H-1,2,4-triazole-1-yl)benzyl)-1h-tetrazole,BDC=1,4-dicarboxybenzene)to eliminate deep-level defects and simultaneously as nanostructured heterogeneous nucleation seed to assist the growth of large-grained perovskite films.Compared with the control and Cd-Httb,Cd-Httb-BDC designed with mix-ligands strategy exhibited the enhanced inducted effect on the crystallization and nucleation of high-quality perovskite films during annealing process.Consequently,the resultant Cd-Httb-BDC-modified device achieved higher power conversion efficiency(PCE)(22.18%)than the control(20.89%)and Cd-Httb(21.56%).Meanwhile,the unencapsulated Cd-Httb-BDC-modified device still maintained 90%of initial PCE after 1500 h in ambient conditions and exhibited enhanced thermal stability(85℃ in N_(2) atmosphere).This work presented a successful example of mixligands strategy on construction of high-quality MOF-assisted perovskite films for high-efficient and stable PSCs.

Synthesis, Crystal Structure, and Magnetic Properties of a Co Metal-organic Framework with Mixed Dicarboxylate and Tricarboxylate Ligands

One new mixed-ligand coordination polymer,namely[Co2（btc）（bpdc）（0.5）（py）3]n（1）,was hydrothermally synthesized using biphenyl-2,4,4＇-tricarboxylic acid（H3btc） as a main building block,along with two auxiliary ligands（H2bpdc = 2,2＇-bipyridine-5,5＇-dicarboxylic acid and py =pyridine）.The product 1 was characterized by IR spectroscopy,elemental,thermogravimetric,and single-crystal X-ray diffraction analyses.Single-crystal X-ray diffraction studies show that compound 1 possesses an intricate 3D metal-organic framework based on tetracobalt（Ⅱ） units.Magnetic susceptibility measurement indicates that compound 1 shows an antiferromagnetic coupling between the Co（Ⅱ） ions.

Synthesis and Characterization of a Metal-Organic Framework Bridged by Long Flexible Ligand

3D supramolecular network with considerable volume pores was created via hydrogen bond & C-H--π. By tightening of The metal-organic frameworks (MOF) namely [Ni(μ-pmb)2(H2O)2]n (pmb = 3,5-bis(4-pyridylmethylenoxyl) benzoate, that have been synthesized by hydrothermal method. Complex 1 crystallizes in triclinic P-1 space group and consists of 1D semi zigzag chain.

Synthesis and Characterization of a Water-stable Metal-organic Framework Based on Mixed Ligands

A new water-stable metal-organic framework,[Cu_2（bdc）_2（tpt）_3]·2H_2O（1,H_2 bdc = terephthalic acid,tpt = 2,4,6-tri（4-pyridinyl）-1,3,5-triazine）,has been synthesized and characterized by elemental analysis,infrared（IR） spectrum,thermogravimetric analysis（TGA）,powder X-ray diffraction（PXRD） and single-crystal X-ray diffraction. Compund 1 crystalizes in monoclinic,space group C2/c with a = 30.147（5）,b = 11.0548（17）,c = 20.867（4） ？,β = 115.035（2）o,C_（70）H_（48）Cu_2N_（18）O_（10）,Mr = 1428.34,V = 6301.0（18） ？~3,Z = 8,D_c = 1.506 g/cm^3,μ = 0.754 mm^（–1）,F（000） = 2928,GOOF = 1.058,λ（MoK α） = 0.71073 ？,the final R = 0.0387 and wR = 0.1091 for 6230 observed reflections with I 〉 2σ（I）. In compound 1,the half metallacycles [Cu_2（tpt）_3] are linked by the bdc2-ligands to form a 1D bent ladder-like chain featured with a nano-sized channel,and these chains link each other via intermolecular hydrogen bonds and π-π stacking interactions to form a 3D supramolecular architecture with the voids filled with free water molecules. In addition,the water stability of 1 was investigated by PXRD patterns,which indicate that compound 1 keeps its structural integrity in boiling water for at least three days.

Comparative Study of the Efficacy of Metal Removal from Contaminated Aqueous Solutions by Solid Bidentate Ligands&Liquid Plant Materials

Heavy metal contaminated water sources pose serious health risks for humans,animals,and plants.Exposure to and ingestion of heavy metals have been associated to liver,kidney,and brain function.Objective:The aim of this research is to comparatively examine the metal removal efficacy of three solid bidentate chemicals and four plant materials.Study Design&Methods:Standard solutions of zinc(II)and lead(II)ions with concentrations of 1,000 ppm were respectively treated with OA(Oxalic Acid),dibasic bidentate ligands(sodium hydrogen phosphate and sodium carbonate).Then,the solutions were placed on a shaker for 15 h,centrifuged,and the supernatant was analyzed using ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectrometry).Results:All the solid bidentate adsorbents were very effective in removing zinc and lead(>90%).However,more lead than zinc was removed across all adsorbents except for lemon where equal percent of zinc and lead(49%)were removed.OA and Na2HPO4 removed about equal amount of lead(>99%).The plant materials(SP(Spinach),bell pepper and GBP(Green Bell Pepper)),respectively and preferentially removed more lead(98.9%,98.3%,81.5%)than zinc(91.7%,46%,46%).Conclusion:Although plant materials have gained attraction for the remediation of heavy metal,however,some bidentate chemical ligands such as OA,sodium carbonate and sodium hydrogen phosphates are even more effective in removing these metals from contaminated water.Furthermore,heavier metals are preferentially removed than lighter metals.

Two Zinc Architectures:A Mononuclear Complex and a 2D Wave-like Organic-inorganic Hybrid Layer

Self-assembly of Zn（NO3）2·6H2O and 2,3,5,6-tetrabromoterephthalic acid（H2TBTA） gave rise to two new zinc metal-organic frameworks,Zn（HTBTA）2（phen）2·H2O（1） and Zn（TBTA）1/2（μ2-OH）（H2O）·0.25EtOH（2）.Complex 1 is a mononuclear molecule.The hydrogen bonding interactions further connect the mononuclear molecules to generate a 2D supramolecular architecture.Complex 2 is a 2D organic-inorganic hybrid layer framework constructed from 1D rod-shaped secondary building units.

Tuning the surface electronic structure of noble metal aerogels to promote the electrocatalytic oxygen reduction

The sluggish kinetics of the oxygen reduction reaction(ORR)is the bottleneck for various electrochemical energy conversion devices.Regulating the electronic structure of electrocatalysts by ligands has received particular attention in deriving valid ORR electrocatalysts.Here,the surface electronic structure of Ptbased noble metal aerogels(NMAs)was modulated by various organic ligands,among which the electron-withdrawing ligand of 4-methylphenylene effectively boosted the ORR electrocatalysis.Theoretical calculations suggested the smaller energy barrier for the transformation of O^(*) to OH^(*) and downshift the d-band center of Pt due to the interaction between 4-methylphenylene and the surface metals,thus enhancing the ORR intrinsic activity.Both Pt3Ni and Pt Pd aerogels with 4-methylphenylene decoration performed significant enhancement in ORR activity and durability in different media.Remarkably,the 4-methylphenylene modified Pt Pd aerogel exhibited the higher halfwave potential of 0.952 V and the mass activity of 10.2 times of commercial Pt/C.This work explained the effect of electronic structure on ORR electrocatalytic properties and would promote functionalized NMAs as efficient ORR electrocatalysts.

面向工业烟道气CO_(2)捕获的基于廉价配体金属有机骨架材料的研究进展

利用高效绿色材料捕获CO_(2)有助于减少人为向大气中排放CO_(2)。目前,面向工业烟道气CO_(2)捕获的高性能金属有机骨架(MOF)材料的设计与合成研究已步入应用驱使的新阶段。研发和制备具有优越综合性能的CO_(2)捕获MOF材料是一项重要挑战。本综述重点关注面向工业烟道气CO_(2)捕获的基于廉价配体MOF材料的研究现状,总结并讨论了其结构、水/热/化学稳定性、吸附量与选择性、吸附能力受湿气的影响、多轮循环使用性、再生性及宏量制备等性能。

Sn基双配体金属有机骨架光催化性能与机理研究

以对苯二甲酸(PTA)和二甲基咪唑(2-MI)为竞争配体,采用溶剂热法制备了新型Sn基双配体金属有机骨架光催化剂(Sn-PTA-MI)。利用XRD、SEM、FT-IR、DRS和电化学测试对制备的光催化剂进行形貌、结构表征以及能带分析。以阳离子型染料罗丹明B(Rh B)为目标污染物,考察了不同因素对光催化剂活性的影响。结果表明,当PTA和2-MI的投加摩尔比为2∶3、催化剂投加质量浓度为1.50 g/L时,光催化40 min后Rh B的去除率达到99%以上,并且反应受pH影响较小。参与催化降解反应的主要活性组分为·O_(2)^(-),其次是h^(+)。

Ni/Co bimetallic organic frameworks nanospheres for highperformance electrochemical energy storage

In addition to their many well-known advantages(e.g.,ultra-high porosity,good pore size distribution,easy functionalization,and structural tolerability),metal-organic frameworks(MOFs)are a new class of advanced functional materials.However,their backbones are highly susceptible to deformation after exposure to acidic or alkaline conditions.As a result of lithium-ion batteries embedding or detaching directly from MOFs,they irreversibly collapse.As a result,they fail to maintain their electrochemical performance.These factors have hindered the development of MOFs as direct electrode materials,making the design of MOF materials with controlled morphology and stable dimensions a new challenge.In this study,we adopted a versatile and effective method to synthesize a novel MOF material(NiCo-BP(BP=BTC/phen and BTC=1,3,5-benzenetricarboxylic acid))using the rigid ligands 1,10-phenanthroline and homobenzotrizoic acid,and the emergence of the Ni-O/N and Co-O/N coordination layers was observed by extended X-ray absorption fine structure(EXAFS)tests,indicating that Ni and Co were coordinated with heterocyclic N-given atoms to form a stable p-πconjugated structure.Meanwhile,the metal-ion is attached to the carboxylic acid ligand on the other side,making the metal-organic skeleton complete and robust.The nanosphere structure of NiCo-BP(~400 nm)allows for full exposure and utilisation of the active sites,especially the Ni,Co,and phenanthroline units,and exhibit impressively high specific capacity and cycling stability.At a high current density of 1.0 A·g^(−1),a high discharge specific capacity of 631.6 mAh·g^(−1)was obtained after 1000 cycles.The co-participation of two organic ligands in the coordination is in accordance with the theory of soft and hard acids and bases,which contributes to the ability of the material to maintain a high capacity in cycling as well as its cyclic stability.

A Hierarchically Porous Metal-Organic Framework from Semirigid Ligand for Gas Adsorption

Hierarchically porous materials play an important role in facilitating mass transport and improving efficiency of adsorption and separation processes. In this paper, a new strategy is proposed to realize a hierarchically porous metal-organic framework （[Cu2（OH）（L）]＇（DMF）0.8 （FJU-11, H3L=3,5-（4-carboxybenzyloxy）benzoic acid, DMF= N,N-dimethylformamide） via using semi-rigid multi-carboxylic acids. Interestingly, FJU-11 possesses the large adsorption capacities and small isosteric heats toward CO2. The column breakthrough experiment for FJU-11 highlights its potential application in the separation of the flue gas.

Two New Cadmium Metal-organic Frameworks Based on a Mixed-donor Ligand

The self-assembly of a prominent mixed-donor ligand, 5-[4-（1H-tetrazolyl）phen]isophthalic acid（H3TZPl）, with a Cd2＋ center generates two new metal-organic frameworks： [Cd（H2TZPI）2（H2O）2]n（JUC-163） and [Cd2（TZPI）（μ3-OH）（H2O）2]-H2O.DMF（JUC-164）. The two complexes demonstrate different structures for the ligand＇s different coordination modes and configurations. JUC-163 shows a 2D layer structure and further forms into a 3D supramolecular framework by noncovalent interactions（C--H…O, O--H…N and π…π interactions）, whereas JUC-164 exhibits a fascinating 3D framework for the outstanding coordination modes and configurations of the ligand, which are fit for the complex structure. And also, the factor of different cadmium salts（chloride and nitrate） which are used in synthesis progress is worth to notice for the construction of the two distinct structures. The luminescent properties of these metal-organic frameworks were also investigated.

Two New Supramolecular Hybrids Based on Bi-capped Keggin {PMo12V2O42} Clusters and Transition Metal Mixed-organic-ligand Complexes

Two supramolecular compounds [Cu（imz）2][Cu（phen）（imz）]2{[Cu（phen）]2[PMo6^VIMo6^VV2^IVO42]}（1） and [Co2（2,2＇-bpy）4（C2O4）][Co（2,2＇-bpy）3][PMo7^VIMo5^VV2^IVO42]（2,2＇-bpy）0.5.H2O（2）（phen=1,10＇-phenanthroline, imz= imidazole, 2,2＇-bpy=2.2＇-bipyridine） have been synthesized hydrothermally and characterized by elemental analyses, infrared spectrum, UV-Vis, X-ray photoelectron spectroscopy（XPS）, electron spin resonance（ESR） spectra, thermogravimetry analyses and single crystal X-ray diffraction analyses. Single-crystal X-ray diffraction analyses revealed that both the compounds represent the examples of compounds based on the bi-capped Keggin polyoxoanion {PMo12V2O42} and transition metal mixed-organic-ligand coordination complexes. Compound 1 consists of bi-capped Keggin polyoxoanion [PMo12V2O42]5 supported copper coordination groups, which are further interconnected with two types of copper complex fragments forming a 3D supramolecular framework via π-π stacking, C-H…O and N-H…-O hydrothermal bonding interactions. Compound 2 is a new hybrid consisted of polyoxoanion [PMo12V2O42]^4-, [Co2（2,2＇-bpy）4（C2O4）]^2＋ and [Co（2,2＇-bpy）3]^2＋. There are no direct interactions in compound 2, but the polyoxoanions together with two different cobalt complex groups construct a 3D supramolecular network through C-H…O hydrogen bonding interactions.

A Novel 3D Metal Organic Framework Based on an Azolate Ligand

Metal organic frameworks（MOFs） have attracted much attention over the world during the last several decades[1-3].Constructed from metal ions and organic building units,MOFs have great properties in gas adsorption[4],catalysis[5],luminescence[6] and magnetism[7].By varying the metal salts and organic building units,numerous MOF structures with designed functionalities and expected properties can be obtained.Among them,zeolitic imidazolate frameworks（ZIFs） have been investigated greatly due to their high thermal and chemical stabilities and tunable porosities[8].ZIFs can be obtained with imidazolate compounds as organic building units,such as imidazole,benzimidazole and 2-methylimidazole[9].Zeolite structures are composed of tetrahedral Si（Al）O4 units,with Si-O-Si angle ca.145°.ZIFs possess imidazole,with M-IM-M（M-metal,IM=imidazole） angle close to 145°,resembling zeolite（Scheme 1）[10].

基于对苯二甲酸的MOFs对含氧阴离子的吸附及光降解研究

以对苯二甲酸为配体与金属盐反应得到两个金属-有机框架材料Cd-MOF和UiO-66,通过X射线粉末衍射仪(XRD)、热分析仪(TG)以及氮气吸脱附对两种MOFs材料进行表征,测试材料的纯度、热稳定性以及多孔性。用所合成的材料进行吸附和光催化降解含氧阴离子实验。结果表明:Cd-MOF对MnO^(-)_(4)、Cr_(2)O_(7)^(2-)和CrO_(4)^(2-)的吸附率分别可以达到100%、57%、62%,经过光降解后的去除率可达到100%、84%、87%,UiO-66对MnO^(-)_(4)、Cr_(2)O_(7)^(2-)、CrO_(4)^(2-)的吸附率分别可以达到66%、25%、60%,经过光降解后的去除率可达到99%、40%、87%。相对于吸附能力,两种MOFs材料对含氧阴离子尤其是含Cr阴离子均表现出更好的光催化降解能力,Cd-MOF对含氧阴离子的去除率优于UiO-66。机理研究表明,在光催化降解过程中产生了活性物质·O^(-)_(2)和·OH,它们的产生有助于提高降解效率。

基于一种唑类羧酸配体的两种配合物的合成、结构及染料吸附性能研究

以1-(3,5-二羧基苄基)-1,2,4-1H-三唑-3-羧酸(H_(3)L1)为有机配体,选择Cu^(2+)和Pb^(2+)为金属中心,通过溶剂热反应制备得到两种新的配合物[Cu(L1)·(CH_(3)CN)_(2)]·H_(2)O(1)和[Pb(L2)](2),H_(2)L_(2)为H_(3)L1原位脱羧产物,并通过单晶X-射线衍射、红外光谱、X-射线粉末衍射、热重分析等对配合物进行表征和分析.染料吸附实验结果表明,配合物1对亚甲基蓝的吸附效率为84.0%,而配合物2对结晶紫的吸附效率为60.2%.

基于3,3′,5,5′-四咪唑基联苯配体的Zn(Ⅱ)金属有机骨架及其吸附性能

选用刚性3,3′,5,5′-四咪唑基联苯(L)作为主配体,分别辅以4,4′-联苯二羧酸(4,4′-H_(2)BPDC)和4,4′-氧二苯甲酸(H_(2)OBA)为第二配体,在水热条件下,成功制备了2种基于Zn的金属有机骨架,即[Zn_(2)(L)(BPDC)_(2)]·H_(2)O(1)和[Zn_(2)(L)(OBA)_(2)]·6H_(2)O(2)。单晶X射线衍射表征结构显示:1和2均为(4,4)-连接的二节点的双重贯穿的新型3D孔道结构,其中2具有一定的孔隙率。活化的2(2′)的吸附性质表明其对H_(2)O和EtOH具有选择性吸附。

钇锆双金属MOFs对有机膦阻垢剂HEDP的吸附研究

采用溶剂热法首次合成了新型钇锆双金属有机框架(YZr-MOF)吸附材料,并对其结构和表面性质进行了表征,研究了YZr-MOF对有机膦阻垢剂羟基亚乙基二膦酸(HEDP)的吸附行为和性质。实验结果表明,YZr-MOF呈现出大小均匀的球形颗粒结构,比表面积为912.862 m^(2)/g;在298 K时,YZr-MOF理论最大吸附量为66.293 mg/g(以P计)。吸附过程符合准二级动力学和Langmuir模型,吸附过程为吸热过程,温度升高有利于YZr-MOF吸附HEDP。在吸附实验中,YZr-MOF的最佳质量浓度为0.2 g/L;YZr-MOF在较宽的pH范围内有着良好的稳定性,并且经过6次循环后,仍保持显著的吸附率。结合相关实验和FTIR、XPS的表征结果表明,静电作用和配体交换为主要吸附机理。

多元介孔MOFs:通过调节表面亲水/疏水性实现酶固定化的多功能平台

作为高效的生物催化剂,酶在食品加工、医药制造、化学工业和能源开发等众多领域发挥着重要作用.然而,游离状态的酶由于存在稳定性差、易失活、难以回收利用及不适用于连续化生产等问题,限制了其广泛应用.为了解决上述难题,人们探索发展了固定化酶技术.固定化酶不仅保留了原有的催化活性,而且在稳定性方面有了显著提升,从而极大地提高了酶的利用效率.随着固定化酶材料和酶工程领域的不断发展,固定化酶技术为酶的应用开辟了更广阔的前景.沸石-咪唑骨架材料-8(ZIF-8)作为一种金属-有机骨架(MOFs)材料,因其独特的结构特性而被广泛用作酶固定化载体.然而,ZIF-8的微孔结构和固有的疏水性,以及前体物2-甲基咪唑(2-MeIm)的质子化现象,常常影响固定化酶的活性.为克服这些限制,本文采用多元配体竞争和孔隙工程相结合的策略,设计并制备了一种具有可调节亲水/疏水表面的新型多元介孔MOFs(mMOFs),并用作酶固定化载体.在mMOFs的制备过程中,采用亲水性和配位能力更强的3-甲基-1H-1,2,4-三唑(3-MTZ)和5-甲基四唑(5-MTA)配体,以部分替代传统的2-MeIm配体.随后,这些多元配体(包括2-MeIm,3-MTZ和5-MTA)与七水硫酸锌结合,在甲醇溶液中通过自凝聚作用形成透明的胶体溶液,进而完全溶解在水中.在此过程中,七水硫酸锌发挥了软模板的作用,引导介孔的形成,从而成功制备出新型多元介孔mMOFs.接着,利用这些mMOFs作为酶固定化的载体,固定了辣根过氧化物酶(HRP)和葡萄糖氧化酶(GOx),并详细研究了其催化性能.结果表明,与传统的ZIF-8载体相比,以mMOFs为载体的固定化酶展现出了更高的酶活性和稳定性.催化性能提升主要归因于mMOFs的亲水性和介孔结构改善了酶和底物间的传质,同时2-MeIm的质子化效应减弱也为酶提供了优良的微环境,稳定了酶的构象.综上,本文采用多元配体竞争与孔隙工程相结合的策略,成功构建了一种具有可调节亲水/疏水表面的新型多元介孔mMOFs,并用于酶固定化,所得固定化酶表现出较好的催化性能.通过深入的研究,揭示了该固定化酶表现出良好催化性能的作用机制,为可控设计制备性能优越的、以MOFs为载体的固定化酶提供了新思路,并为进一步拓宽MOFs材料的应用范围提供了参考.