基于金属有机框架化合物纳米电催化剂的研究进展

金属有机框架化合物具有比表面积大、孔隙率高、结构有序可控等特点,近年来作为电催化材料在电化学能源储存和转化应用中备受关注。本文从金属有机框架化合物作为前驱体制备电催化剂的独特优点入手,总结了目前该类材料在电催化领域的最新研究进展,并对其今后的发展趋势以及面临的机遇和挑战进行了简单的展望。     

用于电解水制氢的过渡金属有机骨架基催化剂

金属有机骨架(MOFs)材料因具有无机和有机的杂合性质、高度有序的多孔性、结构可修饰性、比表面积大和孔隙率高等特点,在催化领域具有广阔的应用前景。本文从氢能的开发利用角度出发,在纯MOFs、MOFs复合及衍生材料三个方面对近十年来过渡金属MOFs基催化剂在电解水制氢方面的重要研究进展进行了综述,着重针对材料的合成进行了探讨,以及在基础研究和产业应用的角度指出当前过渡金属MOFs基制氢催化剂面临的挑战和机遇,对其应用前景进行展望。     

金属有机框架化合物为前驱体制备MgO微粒

在溶剂热条件下,以氯化镁与3-(吡啶-3-甲氧基)邻苯二甲酸为原料,成功合成了一个镁和甲酸根构筑的三维金属有机框架化合物,X射线单晶衍射确定了其晶体结构.通过对所合成的配合物高温煅烧,得到了氧化镁微粒,应用红外光谱、粉末衍射和扫描电子显微镜等对其结构和形貌进行了表征,结果表明,合成的氧化镁纯度高,晶型完整,颗粒分布较为均匀,粒径约为50μm.     

基于金属有机骨架的纳米酶及其应用研究进展

金属有机骨架（MOFs）具有大量的活性位点,且其框架结构可以保护其中包裹的天然酶不被破坏,从而具有模拟天然酶的性质。因此,基于MOF的纳米酶被认为具有良好的发展潜力。MOF基纳米酶分为四大类：分别是单纯MOFs、改性MOFs、与天然酶复合的MOFs以及MOF衍生物。种类的多样性同时也造就了制备、性能以及应用的多样性,这些内容在此综述中将被详细阐述。     

金属有机骨架材料负载镍纳米颗粒催化硝基苯加氢

以MIL-53(Al)、MIL-96(Al)和MIL-120(Al) (MIL: Material Institute of Lavorisier)三种金属有机骨架材料为载体, 采用浸渍法制备了负载廉价金属镍纳米颗粒的催化剂. 将其用于催化硝基苯加氢合成苯胺反应, 发现以MIL-53(Al)为载体制得的催化剂表现出优异的催化性能. 采用不同的镍前驱体, 如硝酸镍、醋酸镍、乙二胺合镍, 制备了一系列Ni/MIL-53(Al)催化剂. 通过X射线衍射、傅里叶变换红外光谱、电感耦合等离子体、N₂物理吸附、H₂程序升温还原、透射电镜等技术对其进行了表征, 研究了镍前驱体对金属-载体相互作用、镍颗粒尺寸以及分散程度的影响.结果表明:以乙二胺合镍为镍前驱体制得的催化剂具有金属-载体相互作用适中、镍纳米颗粒更小(4-5 nm)和分布更均匀的特点, 在硝基苯加氢反应中表现出优异的催化性能, 硝基苯转化率达到100%.回收重复使用5次后, 此催化剂仍保持催化活性,硝基苯转化率达92%.     

金属有机骨架基催化剂在加氢反应中的应用

加氢是现代化工产业中的一类主干反应,广泛应用于精细化学品、药物、食品、染料、功能聚合物及香料等制造产业中.高效催化剂的引入使得加氢反应能够在相对温和的条件下还原各类不饱和化合物.金属催化剂在加氢反应中活性高,所需的反应温度较低,适用性广,但是容易和S,N,As和P等元素结合而"中毒"失去反应活性.金属氧化物催化剂和金属硫化物催化剂具有一定的抗毒性,但活性相对较差,通常需要采用高温高压的反应条件,对催化剂本身和反应器的要求较为苛刻.传统催化剂在反应中具有一定的局限性,所以亟需开发新一代高效的加氢催化剂,在保证高活性和高选择性催化效果的同时,降低对能源的消耗和对环境的负面影响.金属有机骨架(MOFs)作为一种新型的多孔材料在过去二十年中受到相当大的关注,并在催化、气体存储和分离、传感器、发光材料和药物输送等众多领域的应用中表现出卓越的性能.利用MOF材料良好的相容性,将MOF和其它功能材料结合形成新的复合材料可以在更大程度上扩大MOF材料的应用领域.与传统的催化剂相比,MOF基材料具有优异的物理化学特性和结构可调性,通过合理的设计能够满足不同的催化加氢过程:(1)MOF基催化剂具有多样且特异性的活性位点.除了组成MOF材料的金属离子/簇和功能有机配体之外,MOF材料可通过封装其他活性物质或者被活性物质包裹等方式引入其他类型的催化位点,进一步扩大MOF基催化剂在不同催化加氢中的适应性.此外,不同的活性位点之间的协同作用又能特异性地促进反应的进行,对提高反应的选择性起到重要的作用.(2)活性位点的尺寸大小和空间分布可以被有效控制.这能影响到催化剂在催化反应过程中的活性和选择性,并且通过MOF材料的限域效应,同时能增强活性位点的稳定性和耐久性.(3)高比表面积能提高MOF基催化剂的催化活性.这种结构特性不仅可以增加MOF基催化剂的活性位点,而且能够吸附反应物和还原剂达到扩大其局部浓度的效果.(4)反应分子的扩散可通过调节MOF基催化剂的结构实现控制.通过调整MOF材料的孔窗口和通道的尺寸,能够改变反应物在催化剂内部的扩散途径,影响底物和活性位点的接触,能进一步影响反应的活性和选择性.本文总结了近几年来MOF基材料在不同的催化加氢反应中的应用,其中包括烯烃、炔烃、芳硝基化合物、肉桂醛、糠醛和苯等化合物的加氢反应.首先介绍了MOF基材料中不同类型的活性位点,除了MOF材料自身的金属离子/簇和功能有机配体外,MOF基复合材料中的金属纳米颗粒?金属硫化物?金属氧化物?均相催化剂等活性位点可以通过封装或包裹的方式引入.在不同加氢反应中,着重介绍了MOF基催化剂中不同类型活性位点的加氢过程中的催化方式、催化剂本身的结构优化及催化剂与反应底物之间的相互作用,以及这些因素之间的协同作用对反应活性和选择性的影响.最后,讨论了MOF基材料在加氢反应中应用存在的问题以及未来发展展望.     

表面硫化和磷化提升钼酸镍的析氢性能

首先通过水热过程在泡沫镍（NF）上生长出钼酸镍纳米棒阵列（NMO/NF）,再依次利用水热硫化和气相磷化法改性钼酸镍纳米棒阵列获得三维自支撑析氢电催化剂（PS-NMO/NF）。研究表明,硫化作用诱导钼酸镍纳米棒阵列向类珊瑚球结构转变并形成具有高电化学活性表面积的无定形硫化物壳层,显著提高钼酸镍析氢反应（HER）活性。进一步磷化处理,表面形成的无定形磷酸盐与硫化物形成丰富的异质界面,促进了电子转移,进一步提升了电极的HER性能。在1 mol·L^-1 KOH电解液中,电流密度为10 mA·cm^-2时,PS-NMO/NF所对应的析氢过电势为93 mV; 100 mA·cm^-2的电流密度所对应的析氢过电势仅为180mV,Tafel斜率为67 mV·dec^-1,而且在20 h内可稳定运行,无明显衰减。     

羧基配体金属有机骨架材料作为催化剂的研究进展

<正>金属有机骨架材料(MOFs)是由无机金属中心与多齿有机配体通过配位键形成的立体网络结构多孔晶体材料[1].MOFs具有多孔性、大比表面积、结构规整、有机配体的可修饰性、金属离子的可选择性等特点,在气体吸附、气体分离、磁性材料、光学材料和催化剂等领域得到广泛的应用[2-6].尤其是在催化方面,MOFs结合了金属有机配合物和分子筛的优点,可以直接用作催化剂,也可作为催化剂载体使用.     

原位配体功能化策略制备共价金属有机骨架促进其析氢反应

新型多孔材料在诸多领域具有广阔的应用前景,其发展引起了研究者较大关注.在过去的十年中,大量的先进多孔材料被设计并应用于不同领域.其中,共价有机骨架(COFs)和金属有机骨架(MOFs)材料由于具有结构多样、孔隙可调以及功能多样等独特性质,得到了广泛研究.为了有效地结合各个组分的优点以获得最优性能,科研工作者投入了大量的...     

以金属有机骨架为前驱体的高活性氧还原非贵金属催化剂制备

The development of a non‐precious metal electrocatalyst (NPME) with a performance superior to commercial Pt/C for the oxygen reduction reaction (ORR) is important for the commercialization of fuel cells. We report the synthesis of a NPME by heat‐treating Co‐based metal organic frameworks (ZIF‐67) with a small average size of 44 nm. The electrocatalyst pyrolyzed at 600 °C showed the best performance and the performance was enhanced when it was supported on BP 2000. The resulting electrocatalyst was composed of 10 nm Co nanoparticles coated by 3–12 layers of N doped graphite layers which as a whole was embedded in a carbon matrix. The ORR performance of the electrocatalyst was tested by rotating disk electrode tests in O2‐saturated 0.1 mol/L KOH under ambient conditions. The electrocatalyst (1.0 mg/cm2) showed an onset potential of 1.017 V (vs. RHE) and a half‐wave potential of 0.857 V (vs. RHE), which showed it was as good as the commer‐cial Pt/C (20μgPt/cm2). Furthermore, the electrocatalyst possessed much better stability and re‐sistance to methanol crossover than Pt/C.     

One‐Step Synthesis of Self‐Supported Nickel Phosphide Nanosheet Array Cathodes for Efficient Electrocatalytic Hydrogen Generation

Nickel phosphide is an emerging low‐cost, earth‐abundant catalyst that can efficiently reduce water to generate hydrogen. However, the synthesis of nickel phosphide catalysts usually involves multiple steps and is laborious. Herein, a convenient and straightforward approach to the synthesis of a three‐dimensional (3D) self‐supported biphasic Ni₅P₄‐Ni₂P nanosheet (NS) array cathode is presented, which is obtained by direct phosphorization of commercially available nickel foam using phosphorus vapor. The synthesized 3D Ni₅P₄‐Ni₂P‐NS array cathode exhibits outstanding electrocatalytic activity and long‐term durability toward the hydrogen evolution reaction (HER) in acidic medium. The fabrication procedure reported here is scalable, showing substantial promise for use in water electrolysis. More importantly, the approach can be readily extended to synthesize other self‐supported transition metal phosphide HER cathodes.     

基于金属有机框架衍生的Fe-N-C纳米复合材料作为高效的氧还原催化剂

Environmentally friendly and renewable energy technologies, such as fuel cells and metal-air batteries, hold great promise for solving current energy and environmental challenges. The oxygen reduction reaction (ORR) plays a pivotal role in this top-drawer question. However, the sluggish kinetics of the ORR and prohibitive costs limit the global scalability of such devices. Traditionally, platinum-based electrocatalysts exhibit the best performance for ORRs in both acid and alkaline electrolytes. However, to significantly reduce the cost and realize sustainable development, utilization of Pt must be replaced or significantly reduced in the ORR cathode for fuel cell applications. Therefore, developing earth-abundant and high-performance non-precious metal catalysts (NPMCs) for ORR is of critical importance for the commercialization of fuel cells. In comparison to traditional catalysts, metal-organic frameworks (MOFs) are ideal precursors that integrate metal, nitrogen, and carbon functionalities together into one ordered 3D crystal structure. MOFs, assembled by secondary building of units comprised of metals and organic linkers with strong bonding, have received significant research attention because they possess permanent porosity, a three-dimensional (3D) structure, and can be prepared using a diversity of metals and organic linkers. High surface area, and microporous carbon materials can be easily obtained by carbonization of MOFs at high temperatures. In particular, MOF-derived carbon nanocomposites, which were prepared from transition metals, and have the form M-N-C (M = Fe or Co), have demonstrated remarkably improved catalytic activity and stability. Herein, we report an NPMC material consisting of Fe₃C nanoparticles encapsulated in mesoporous N-doped carbon (Fe-N-C), synthesized by a simple strategy involving physical mixing of MIL-100(Fe) with glucose and urea, and subsequent pyrolysis under inert atmosphere. The strong interaction between metal atoms and nitrogen atoms is beneficial in generating more active sites, and sites with a higher intrinsic catalytic activity, via carbonization. The as-obtained catalysts exhibit remarkable ORR activity in alkaline media, with the best catalyst (Fe-N-C-900, which is synthesized at 900 ℃) featuring a more positive onset potential (0.96 V vs the reversible hydrogen electrode (RHE)), a more positive half-wave potential (0.83 V vs RHE), a much higher diffusion limiting current density (6.28 mA·cm^-2) and a larger electron-transfer number (n), even at low overpotentials, compared with other contrast materials. Fe-N-C-900's excellent catalytic activity and stability in ORR are due to its large BET surface area, its large total pore volume, its nitrogen dopants, its active Fe₃C nanoparticles and the cooperative effects among its reactive functionalities.     

负载镍的金属有机骨架化合物在温和条件下的储氢性能

利用传统的浸渍法在一种金属有机骨架化合物MIL-101(Cr3F(H2O)2O[(O2C)-C6H4-(CO2)]3.nH2O,n≈25)上负载金属镍,制备了Ni/MIL-101复合材料.通过采用不同的浸渍手段(过量浸渍,等体积浸渍)和不同的还原方法(液相化学还原,固相加氢还原)制得了不同的Ni/MIL-101样品,并考察了这些样品在温和条件(25~100℃,0.01~4MPa)下的储氢性能.结果表明,Ni/MIL-101样品的储氢性能均比MIL-101的储氢性能有所改善.其中,采用过量浸渍和液相化学还原相结合制备的Ni/MIL-101样品的储氢性能最佳,储氢量可达1.02%.     

Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles

Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H₂SO₄, pH 0.3). Uniform, multi‐faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm^?2 mass loading) produced a cathodic current density of 20 mA cm^?2 at an overpotential of ?85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H₂SO₄. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long‐term viability under operating conditions. CoP is therefore amongst the most active, acid‐stable, earth‐abundant HER electrocatalysts reported to date.     

Nickel-Based Metal-Organic Frameworks as Electrocatalysts for the Oxygen Evolution Reaction (OER)

The exploration of earth-abundant electrocatalysts with high performance for the oxygen evolution reaction (OER) is eminently desirable and remains a significant challenge. The composite of the metal-organic framework (MOF) Ni₁₀Co-BTC (BTC = 1,3,5-benzenetricarboxylate) and the highly conductive carbon material ketjenblack (KB) could be easily obtained from the MOF synthesis in the presence of KB in a one-step solvothermal reaction. The composite and the pristine MOF perform better than commercially available Ni/NiO nanoparticles under the same conditions for the OER. Activation of the nickel-cobalt clusters from the MOF can be seen under the applied anodic potential, which steadily boosts the OER performance. Ni₁₀Co-BTC and Ni₁₀Co-BTC/KB are used as sacrificial agents and undergo structural changes during electrochemical measurements, the stabilized materials show good OER performances.     

Selenium‐Enriched Nickel Selenide Nanosheets as a Robust Electrocatalyst for Hydrogen Generation

To address the urgent need for clean and sustainable energy, the rapid development of hydrogen‐based technologies has started to revolutionize the use of earth‐abundant noble‐metal‐free catalysts for the hydrogen evolution reaction (HER). Like the active sites of hydrogenases, the cation sites of pyrite‐type transition‐metal dichalcogenides have been suggested to be active in the HER. Herein, we synthesized electrodes based on a Se‐enriched NiSe₂ nanosheet array and explored the relationship between the anion sites and the improved hydrogen evolution activity through theoretical and experimental studies. The free energy for atomic hydrogen adsorption is much lower on the Se sites (0.13 eV) than on the Ni sites (0.87 eV). Notably, this electrode benefits from remarkable kinetic properties, with a small overpotential of 117 mV at 10 mA cm^?2, a low Tafel slope of 32 mV per decade, and excellent stability. Control experiments showed that the efficient conversion of H⁺ into H₂ is due to the presence of an excess of selenium in the NiSe₂ nanosheet surface.     

磷化镍/介孔TiO_2催化剂的制备及其催化加氢脱硫性能

以介孔TiO2(m-TiO2)为载体,采用程序升温还原法制备了Ni2P/m-TiO2催化剂,考察了不同起始Ni/P摩尔比及活性组分负载量对该催化剂结构及其催化加氢脱硫(HDS)性能的影响.结果表明,当Ni/P摩尔比为1.25时,活性组分以Ni2P为主,催化剂的最佳Ni负载量为10%.采用X射线衍射、低温N2吸附-脱附、场发射扫描电镜和程序升温还原等技术表征了m-TiO2及其它不同载体负载的Ni2P催化剂.结果表明,高结晶度m-TiO2载体使Ni和P物种的还原温度大幅度降低,在450～600oC还原制得的Ni2P/m-TiO2催化剂的结构参数基本一致,比表面积均为90m2/g左右,具有很高的热稳定性和对二苯并噻吩的HDS催化性能.在相同的反应条件下,m-TiO2负载的Ni2P催化剂HDS性能最好,各载体负载的Ni2P催化剂活性大小顺序为Ni2P/m-TiO2Ni2P/SiO2Ni2P/P25.     

Au/MOF催化剂的制备、表征及其催化三组分偶联反应

采用后合成共价修饰法和一锅法分别制备了催化剂IRMOF-3-SI-Au(PS)和IRMOF-3-SI-Au(OP),运用X射线衍射、红外光谱、热重-差热分析、透射电镜以及程序升温还原对催化剂进行了表征,探索了这两种催化剂在醛、炔和胺三组分偶联反应中的催化性能,并推测了可能的反应机理.结果表明,两种催化剂对醛、炔和胺三组分偶联反应均具有较高的催化活性,产物炔丙基胺类选择性为100%,且可循环使用;结晶度较低的IRMOF-3-SI-Au(PS)的活性高于结晶度较高的IRMOF-3-SI-Au(OP);催化剂对芳香醛和脂肪醛以及环状胺均具有较高的催化活性,且对带有吸电子基团的芳香醛的活性高于带有供电子基团的.     

一种新型高活性加氢脱硫催化剂:二氧化硅担载的磷化镍

 以硝酸镍和磷酸氢二铵为原料,采用程序升温还原方法在823 K和氢气气氛中制备了纯相和 二氧化硅担载的磷化镍催化剂,并采用类似的方法制备了纯相和二氧化硅担载的磷化钼和 镍钼磷新型磷化物. 对这些磷化物及其相应硫化物的加氢脱硫活性进行了考察. 结果表明,Ni2P/SiO2催化剂具有相对较高的二苯并噻吩转化率和联苯选择性, Ni2P/SiO2对二苯并噻吩加氢脱硫的催化活性甚至高于硫化态的Ni-Mo催化剂.