Hydrogen Storage in Metal-Organic Frameworks

Recent decades have witnessed the explosive emergence of metal organic frameworks (MOFs) as functional ultrahigh surface area materials. Categorized as an intriguing class of hybrid materials, MOFs exhibit infinite crystalline lattices with inorganic vertices and molecular-scale organic linkers. Fortunately, the large internal surface areas and overall pore volumes, adjustable pore sizes, ultralow densities, and tunable framework–adsorbate interaction by ligand functionalization and metal choice, enable MOFs to be promising materials for wide applications. In particular, these remarkable properties render MOFs potential hydrogen storage materials. By virtue of their exceptionally high surface areas, unparalleled tenability and structural diversity, MOFs have become a hotspot of research within the scientific community. This paper reviews the different methods used for the synthesis of MOFs, the relationship between structural features and hydrogen adsorption, the strategies for hydrogen uptake improvement as well as the molecular simulation.     

Reticular Chemistry of Multifunctional Metal-Organic Framework Materials

Metal-organic frameworks (MOFs) are crystalline solids constructed by means of reticular chemistry (refers to the connection of molecular building units via strong bonds to make extended structures), which is currently one of the most rapidly expanding platforms for new functional materials. Rational combinations of various building units enable MOFs to show tailorable pore structures. Based on well-established approaches, including the control over pore size and pore chemistry, immobilization of functional sites, post-synthetic modification, and multivariate complex, multifunctional MOFs can be readily synthesized. In this brief review, we summarize and highlight our research progress in MOF chemistry on applications including gas storage, gas separations, optical response, chemical sensing, proton conduction, and molecular recognitions.     

Classical density functional theory for methane adsorption in metal‐organic framework materials

Natural gas is considered as a promising alternative to petroleum as the next generation of primary transportation fuel owing to relatively smaller carbon footprint and lower SO_x/NO_x emissions and to fast developments of shale gas in recent years. Since the volumetric energy density of methane amounts to only about 1% of that of gasoline at ambient conditions, natural gas storage represents one of the key challenges for prevalent deployment of natural gas vehicles. In this work, we present a molecular thermodynamic model potentially useful for high‐throughput screening of nanoporous materials for natural gas storage. We investigate methane adsorption in a large library of metal‐organic frameworks (MOFs) using four versions of classical density functional theory (DFT) and calibrate the theoretical predictions with extensive simulation data for total gas uptake and delivery capacity. In combination with an extended excess entropy scaling method, the classical DFT is also used to predict the self‐diffusion coefficients of the confined gas in several top‐ranked MOFs. The molecular thermodynamic model has been used to identify promising MOF materials and possible variations of operation parameters to meet the Advanced Research Projects Agency‐Energy (ARPA‐E) target set by the U.S. Department of Energy for natural gas storage. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3012–3021, 2015     

Emerging Synthetic Methods and Applications of MOF-Based Gels in Supercapacitors,Water Treatment,Catalysis, Adsorption,and Energy Storage

Metal–organic frameworks (MOFs), which are synthesized through the self-assembly of organic ligands and inorganic metals, have drawn considerable research interest owing to their unique properties and attractive structures. Many studies on various MOF derivatives, such as MOFs and cellulose aerogels, hydrogel composite materials, and bimetallic-centered MOF materials, have provided the potential for wide application of MOFs. However, MOFs mostly exist in the form of powder particles, which are difficult to form. In addition, MOFs have problems with structural instability. MOF-based gels can overcome this problem. MOF-based gels also have significant advantages in secondary processing. In this review, synthetic methods for MOF-based gels, particularly the synergistic effect with other materials, are introduced. The applications of MOF-based hydrogels and aerogels in supercapacitors, water treatment, catalysis, adsorption, and energy storage are also discussed.     

Computational screening of metal‐organic frameworks for xenon/krypton separation

A variety of metal‐organic frameworks (MOFs) with varying linkers, topologies, pore sizes, and metal atoms were screened for xenon/krypton separation using grand canonical Monte Carlo (GCMC) simulations. The results indicate that small pores with strong adsorption sites are desired to preferentially adsorb xenon over krypton in multicomponent adsorption. However, if the pore size is too small, it can significantly limit overall gas uptake, which is undesirable. Based on our simulations, MOF‐505 was identified as a promising material due to its increased xenon selectivity over a wider pressure range compared with other MOFs investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Molecular simulation studies of separation of CH4/H2 mixture in metal-organic frameworks with interpenetration and mixed-ligand

In our previous work, we have investigated the adsorption selectivity of CH₄/H₂ in three pairs of isoreticular metal-organic frameworks (IRMOFs) with and without interpenetration to study the effect of interpenetration on gas mixture separation through Monte Carlo simulation. In addition, the self-diffusivities and the diffusion mechanism of single H₂ and CH₄ in these MOFs were examined by molecular dynamics simulations. In this work, we extend our previous work to mixed-ligand MOFs to investigate the effects of interpenetration as well as mixed-ligand on both equilibrium-based and kinetic-based gas mixture separation. We found that methane adsorption selectivity is much enhanced in the selected mixed-ligand interpenetrated MOFs compared with their non-interpenetrated counterparts, similar to what we found before for IRMOFs with single-ligand. At room temperature and atmospheric pressure, molecular-level segregation was observed in the mixed-ligand MOFs, and the extent of the effects of interpenetration is comparable for single-ligand and mixed-ligand MOFs. In addition, we found that the diffusion selectivity in the interpenetrated MOFs is similar to the one in their non-interpenetrated counterparts, while the permeation selectivity in the former is much higher than that in the latter, which corroborates our expectation that interpenetration is a good strategy to improve the overall performance of a material as a membrane in separation applications based only on the single component diffusion results. Furthermore, the CH₄ permeability of the selected MOF membrane was also evaluated.     

金属有机骨架材料（MOFs）用于气态轻烃的高效分离研究进展

气态轻烃（C₁～C₃）如甲烷、乙烯、丙烯分别作为应用最广的清洁燃料和大宗化工产品,在国民经济中占据重要的地位。然而,在其生产过程中广泛存在着分离与提纯能耗较高的问题。金属有机骨架材料（MOFs）作为第三代新型多孔材料,近年来在轻烃分离领域显示出巨大的应用潜力。本文综述了MOFs用于气态轻烃分离的现状和机理,总结了本文作者课题组针对不同轻烃产物的分离要求,对MOFs进行了精确的孔径调控、配体功能化修饰、构筑吸附位点、调变柔性结构“开口压力”等,实现了多种气态轻烃组分的高效分离。最后,针对低碳烃工业分离过程中存在的关键问题,对MOFs材料的吸附分离机理进行了深入分析,以及MOFs工业化应用所面临的结构稳定性与分离工艺匹配等进行了展望。     

多级孔金属有机骨架材料的合成及其在生物医药中的应用研究进展

金属有机骨架（metal-organic frameworks,MOFs）是多孔材料领域的研究热点之一。MOFs具有高比表面积和孔道均一等特点,但微孔MOFs在大分子应用领域受到限制。本文介绍了延长配体法、模板剂法和聚合物法等多种制备多级孔MOFs的方法,合成后的多级孔MOFs兼具微孔、介孔和大孔,能够参与大分子反应,同时具有水热稳定性和化学稳定性,在催化、气体吸附分离、储能材料等诸多领域表现出优异性能。本文重点介绍了多级孔MOFs在生物医药领域的研究进展,结果表明多级孔MOFs是一种孔道可调节、可在特定条件下分解的生物相容性材料,用于固定化酶和负载医药分子均表现出良好性能。最后讨论了多级孔MOFs材料制备和应用目前存在的问题与挑战,展望了多级孔MOFs材料作为一类新型功能化多孔材料的应用前景。     

金属有机框架材料的绿色合成

金属有机框架化合物（Metal-organic frameworks,简称MOFs）是由金属离子（或簇）与有机配体配位并经由自组装而形成的一类多孔材料^[1]。MOFs具有极其发达的孔道结构,比表面积和孔容远超其他多孔材料。有机/无机杂化这一特点也赋予了MOFs其他材料（例如沸石、活性炭等）所不具备的无限结构功能可调性^[2]。此外,MOFs具有移除客体分子而主体框架完好保持的持久孔道或孔穴,这使得MOFs具有超乎寻常的化学及物理稳定性。正是基于以上这些特点,MOFs在许多领域有着丰富的应用^[3-4],例如催化^[5]、H₂储存^[6]、CO₂捕集^[7]、药物运输^[8]、污染物吸附^[9]、生物医学成像^[10]等方面。MOFs的商业化探索成为了目前的热点。MOFs的很多应用都与可持续发展及“绿色材料”有关,但MOFs本身的合成过程也需要考虑可持续性和环境影响。金属有机化学所面临的环境挑战是独特的,因为它将金属离子、有机配体的危害联系在一起,且合成过程大多需要大量能耗。主要介绍了金属有机框架材料的绿色可持续合成,主要分为4个方面：1）使用更安全或生物相容性的配体;2）使用更绿色、低成本的金属源;3）绿色溶剂的开发;4）无溶剂合成法。     

金属有机框架光催化剂微环境调控研究进展

金属有机框架材料（MOFs）是一类无机金属中心和有机配体自组装形成的晶体多孔材料,既有无机材料高结晶度、高电子迁移率等特点,又兼具有机材料高比表面积、高孔隙率、强可修饰性等特点,在光催化领域显示出广阔的应用前景。围绕物理化学微环境调控,对近年来MOFs光催化材料的研究进行了详细综述。其中,物理微环境的调控重点介绍了微观形貌调控、贵金属沉积和异质结构建三个方面;化学微环境调控重点介绍了金属位点调控与有机配体调控两个方面。此外,对MOFs光催化材料的未来发展进行展望,以期为高性能MOFs光催化剂的理性设计和可控制备等方面的研究提供思路。     

疏水性金属-有机骨架材料的研究进展

金属-有机骨架（metal-organic frameworks, MOFs）材料是一种由金属离子和有机配体通过自组装形成的新型多孔材料,具有优异的物理及化学性能,因而在气体吸附储存、气体分离以及工业催化等方面表现出良好的应用潜力。但在应用的过程中,无处不在的水分子会影响MOFs骨架的稳定性和吸附性能,极大地制约了其实际应用。本文介绍了近年来疏水性MOFs材料的研究进展,重点论述了金属离子和有机配体对调控MOFs亲疏水性的影响以及通过配体后修饰和疏水性物质复合等提高疏水性的方法,分析了MOFs材料的亲疏水性机理,同时提出了实验结合计算机模拟技术筛选疏水性MOFs的手段。最后,指出目前疏水性MOFs材料合成存在的问题及解决方法,期望为今后拓宽MOFs材料在高湿环境中的应用提供一些有用的参考。     

纳米MOFs及其衍生物在超级电容器中的研究进展

金属有机框架（MOFs）材料因其大的比表面积、可调控的孔道结构和丰富的活性位点引起了国内外学者们的广泛关注。近年来MOFs基材料广泛应用于能量储存与转化领域,但大多数MOFs基材料的低稳定性和低导电性等缺陷限制了其实际应用。通过对MOFs基材料进行改性,如采用共轭度高的有机配体以增加MOFs材料的稳定性,或MOFs衍生物以提高其氧化还原活性位点和导电性,从而达到提高MOFs基电极材料的电化学性能。主要介绍了原始MOFs及其衍生材料如碳材料、金属氧化物、金属硫化物、金属氢氧化物和金属磷化物等在超级电容器电极材料中的最新研究进展。研究表明,多金属MOFs材料或多金属MOFs衍生物有利于提高电极材料的电化学性能,而导电MOFs材料或MOFs衍生物中的碳材料有利于提高电极材料的导电性。最后对MOFs基电极材料在电化学储能领域中的研究做出了展望,指出MOFs基材料的形貌、组分和导电性是未来研究的发展方向。     

构筑手性金属有机骨架的方法及其在不对称催化中的应用

手性金属有机骨架(MOF)具有独特的结构、不对称催化和手性拆分等性能,引起了催化学者的极大重视.系统地介绍了国内外有关手性MOF的合成方法,即:①非手性物质在晶体生长过程中自组装;②使用手性化合物来诱导合成;③通过手性有机基团与金属离子配位将手性成分嵌入金属有机骨架;④表面修饰的方法,第3种方法是最常用的合成手性MOF的方法.重点阐述了近年来手性MOF在不对称催化领域的最新研究成果,希望能为手性MOF研究者设计、合成更优良的手性MOF催化剂提供参考.未来手性MOF催化的主要目标在于合成性能更加高效、稳定的新型手性MOF催化剂,并应用于大规模工业生产中,在温和条件下实现较高的转化数和对映体选择性.     

Research on synthesis and application of metal-organic frame composites in supercapacitors

Electrode material is a key component of supercapacitors (SCs). As a porous material, metal-organic frameworks (MOFs) have attracted much attention in the field of SCs electrode materials due to their high specific surface area, controllable structure, and adjustable pore size. The low conductivity and stability of MOFs are still the main challenges in practical applications. MOF composite materials are a type of composite materials composed of MOFs and one or more different materials. They can effectively combine the advantages of MOFs with the advantages of other functional materials, such as excellent electrical conductivity and unique electrochemical properties. Therefore, MOF composite materials can achieve high reversible capacity and excellent cycle performance, overcome the shortcomings of MOFs materials, and have broad application prospects in the field of SCs electrode materials. According to the dimensional classification of the materials combined with MOFs, they can be divided into four types of composite materials: 0D, 1D, 2D, and 3D MOFs. The composition and synthesis methods of these four types of composite materials are reviewed. The application of MOF composite materials in the field of SCs is systematically introduced. Furthermore, its development prospects are prospected.     

金属有机框架复合材料在超级电容器中的合成及应用研究

电极材料是超级电容器（SCs）的关键部件,金属有机框架（MOFs）作为一种多孔材料,由于其具有比表面积大、结构可控、孔径可调等优点在SCs电极材料领域得到诸多关注,而MOFs的低导电性和稳定性仍然是实际应用中的主要挑战。MOF复合材料是一类由MOFs与一种或多种不同材料组成的复合材料,它可以有效地结合MOFs和其他功能材料的优势,例如优良的导电性和独特的电化学性质等。因此,MOF复合材料可以实现高可逆容量和优良的循环性能,克服MOFs材料的缺点,在超级电容器电极材料领域具有广阔的应用前景。根据与MOFs复合的材料维度分类,可分为0D、1D、2D和3D MOFs四类复合材料,重点综述了这四类复合材料的组成及合成方法,并系统介绍了MOF复合材料的SCs应用,对其发展前景进行展望。     

稀有气体Xe/Kr吸附分离研究进展

稀有气体Xe/Kr的高效捕集分离是气体工业、核环境监测和乏燃料处理等领域的重要分离过程之一。氙与氪结构与极化率相似,传统低温精馏方法借助氙与氪的沸点差异实现二者分离,能耗巨大,吸附分离是较为理想的替代分离技术。以金属有机框架材料为代表的新型多孔材料具有结构多样性与高度可设计性,通过调节材料微孔表面的极化环境与孔道窗口结构,借助氙与氪极化率的微小差异,可实现对二者的精准辨识,有良好的吸附分离性能与应用前景。重点综述了金属有机框架材料在氙氪分离中的研究进展,归纳了材料的极化环境、孔道结构、框架柔性等因素对氙氪吸附分离性能的影响规律,探讨了金属有机框架材料在氙氪吸附分离研究中存在的问题和局限,并对未来发展方向进行了展望。     

金属-有机框架在二次电池中的储能机制研究进展

金属-有机框架（MOFs）具有多孔、大比表面积和结构与功能可调控等特点,已被广泛用作二次电池电极材料。本文重点介绍了MOFs作为二次电池电极材料的储能机制研究进展,主要分为转化储能机制、脱嵌储能机制、物理吸脱附储能机制等,并分析了各类储能机理的储能特点及对电化学性能的影响,探究了MOFs在较大离子半径的钠、钾离子电池中的应用特点及发展潜力。最后简要讨论了MOFs作为电极材料的设计思路为兼顾各类储能机制的优点,即选用较多储能位点的结构及较稳定的金属离子作为有机配体的连接点。     

Renaissance of the Methane Adsorbents

Clean vehicles empowered by natural gas is an immediate solution to meet the demands of the cut off of CO₂ emission, energy crisis, and air-pollution control. To boost the on-board storage capacity, safety and efficiency, great efforts have been made in developing advanced porous materials as methane adsorbents to store more gas under lower pressure or in a more compact space so-called adsorbed natural gas (ANG) technique. A blooming of methane adsorbents and the competition of methane storage records have been therefore awakened by the reticular chemistry of metal-organic frameworks (MOFs), through which the adsorption sites, functionalities, and nano-confinement space can be then controlled and manipulated. In this personal account, we walk through the research paradigm shifts in MOFs for on board methane storage. Furthermore, inspiration and considerations are also discussed, which can be further transferred into the discovery of other methane adsorbents.     

金属有机骨架材料用于吸附分离CH4和N2的研究进展

非常规天然气的利用不仅可以有效缓解常规天然气不足带来的能源问题,而且可以降低其肆意排放带来的温室效应,无论是低浓度煤层气的提浓还是低品质天然气的提质都需要解决甲烷与氮气的分离难题。基于金属有机骨架（MOFs）材料结构和功能均呈多样化的特色,本文主要从CH₄选择型MOFs吸附材料和N₂选择型MOFs吸附材料两个方面,综述了近年来MOFs材料在CH₄与N₂吸附分离方面的研究进展,讨论了影响二者分离的影响因素,并对吸附与分离机理与MOFs结构和性能关联进行了详细的总结与分析,提出了CH₄与N₂选择性提升的方法,即需要合适的孔道尺寸与弱极性表面性质或有利骨架结构的协同作用,最后展望了MOFs材料在甲烷富集和纯化领域的应用前景和发展趋势。