功能化MOFs及MOFs/聚合物复合膜在有机染料和重金属离子吸附分离中的应用

全球工业的发展带来了严重的水污染问题,对含各类有机和无机污染物工业废水的处理也成为了重要研究课题。金属-有机骨架(Metal-Organic Frameworks, MOFs)化合物由于其大比表面积、高孔隙率、有序孔道结构及可调节孔道物理化学性质、热稳定性高、易于合成和丰富的开放活性位点等特点,在诸多领域得到广泛应用,其中在固相吸附/分离领域,特别是吸附水中污染物方面展现出良好应用前景。通过合成后改性、使用含取代基配体原位合成、与特定功能材料复合等方法实现MOFs功能化,可有效增加MOFs材料的吸附活性位点,提高吸附性能和吸附选择性。与MOFs颗粒相比较,MOFs/聚合物复合膜结合了MOFs颗粒的结构与物理化学特性以及聚合物薄膜优秀的分离/载体性能,在有机染料及重金属离子的吸附中表现出优秀的吸附/分离性能。本文重点综述了以染料和重金属离子为代表的有机、无机污染物的吸附去除为目标的MOFs功能化方法,以及MOFs/聚合物复合膜的制备方法,并对未来研究方向和研究前景进行展望。     

锆基MOF孔道限域强化及其低碳烃吸附分离性能

从天然气中回收C2/C3低碳烃组分以及乙烯/乙烷、丙烯/丙烷的分离纯化具有重要的工业价值,吸附分离技术可以在常温常压下高效分离低碳烃。对金属有机骨架(Metal-Organic Framework,MOF)材料进行次级结构单元(Second Building Units,SBU)调控,构筑限域强化的碱性孔道化学微环境并引入新的吸附位点,可以提升其吸附分离性能。文章用三乙烯二胺(TED)取代Zr-TBAPy中SBU配位的水分子,制备了具有更大烷烃吸附容量和选择性的TED@Zr-TBAPy。其中,TED_1/3@Zr-TBAPy表现出优先吸附烷烃的特征,丙烷/丙烯、乙烷/乙烯的理想吸附溶液理论(Ideal Adsorption Solution Theory,IAST)选择性分别为1.32、1.49,比Zr-TBAPy提高了15.7%和3.5%。常温常压下,丙烷/甲烷和乙烷/甲烷的IAST选择性分别达到287和14,比Zr-TBAPy提高了116%和19.7%,超过大部分已报道的同类材料。机理研究表明,TED的引入提高了孔道的限域吸附作用,同时引入对烷烃具有更强吸附作用...     

金属有机骨架材料在吸附分离大气污染物中的应用

大气污染问题是关系人民生命健康和经济社会和谐发展的重大问题.因此需要开发高效的吸附材料用于大气污染物的吸附和分离.金属有机骨架材料(MOFs)是一类新型的多孔材料,该材料具有结构多样、孔结构有序、大比表面积和高孔隙率等结构特点.MOFs通过调节有机配体的长度和官能团调节孔径和孔道尺寸,并进行功能化修饰在孔道中引入功能性...     

基于金属有机骨架材料固定相的气相色谱分离应用

金属有机骨架材料(MOFs)是一类由有机配体和金属离子(或金属簇)自组装形成的新型多功能材料。MOFs具有孔隙度高、比表面积大、孔径可调、化学和热稳定性高等特点,被广泛应用于吸附、分离、催化等多个领域。近年来,MOFs作为新型气相色谱固定相用于分离异构体受到了广泛关注。与传统无机多孔材料相比,MOFs在结构和功能上展现出高度的可调性,通过合理地选择配体和金属中心,可以设计合成具有不同孔道大小和孔道环境的MOFs,从而分别从热力学和动力学角度优化色谱分离效果,有效提高分离选择性。该文结合MOFs的结构,讨论了MOFs气相色谱固定相分离不同类型分析物的分离机理。分离机理主要包括MOFs孔道的分子筛效应或形状选择性,MOFs不饱和的金属位点与分析物中不同的官能团之间产生的相互作用,分析物与MOFs孔道之间产生的不同范德华力、π-π相互作用和氢键相互作用。此外,MOFs的手性分离可能主要依赖于外消旋体与手性MOFs中手性活性位点之间的相互作用。该文也对不同分析目标物进行了归类,综述了多种MOFs气相色谱固定相对烷烃、二甲苯异构体和乙基甲苯、外消旋体、含氧有机物、环境有机污染物的气相色谱分离效果。最后,该文还对MOFs在该领域的应用进行了总结与展望,旨在为MOFs气相色谱高效分离的研究提供参考。     

金属-有机骨架材料及其在催化反应中的应用

金属-有机骨架(metal-organic frameworks, MOFs)材料是由金属离子和有机配体通过自组装而成的具有多孔结构的特殊晶体材料。由于其种类的多样性、孔道的可调性和结构的易功能化,已在气体的吸附和分离、催化、磁学、生物医学等领域表现出了诱人的应用前景。本文介绍了MOFs材料的类型和常用的合成方法,综述了近年来MOFs材料在催化领域的应用,特别是以MOFs材料中骨架金属作为活性中心、骨架有机配体作为活性中心和负载催化活性组分的催化反应,并对MOFs材料的催化应用趋势做了展望,以期对MOFs材料的催化性能有比较全面的认识。     

金属有机骨架材料在吸附分离研究中的应用进展

作为一种新型的纳米多孔材料,金属有机骨架材料（Metal-Organic Frameworks,MOFs）在近二十余年中得到了飞速的发展.MOFs材料由无机金属离子和有机配体通过自组装形成,具有许多优于传统多孔材料的特性.超高的比表面积、较高的孔隙率、可调的孔道尺寸、良好的热稳定性和化学稳定性使得MOFs材料在多个领域中展现出了广阔的应用前景.随着研究的不断深入,MOFs材料被广泛应用于催化反应、吸附分离、生物医学等领域中,并表现出了优异的效果.本文着力于近年来MOFs材料在吸附分离研究中的进展,重点介绍了这类材料在能源气体贮存、碳捕获、膜分离、液相吸附、色谱的分离净化方面的应用,并对其今后的发展进行了展望.     

离子液体修饰金属有机骨架复合材料的制备及其在分离分析中的应用

金属有机骨架(MOFs)是一类新型多孔材料,具有孔径均匀、孔结构可调、易于合成和结构多样等特点。用离子液体(ILs)修饰MOFs构建的ILs/MOFs复合材料,在保留MOFs的结构特点外,还兼具ILs物化性质可调控和稳定性高等优点,在分离分析领域具有较大的发展潜力,引起了研究者的极大兴趣。本文主要综述了近五年来ILs/MOFs复合材料的制备方法及其在分离分析中的研究和应用进展,包括在吸附/萃取、色谱分离以及光谱和电化学分析中的应用研究,并对其发展趋势进行了展望。     

核壳结构金属-有机骨架的研究

核壳结构(core-shell)金属-有机骨架(metal-organic frameworks,MOFs)是多功能MOFs复合材料中最为典型的一类构型,是由MOFs材料和另一种材料(如MOFs、碳材料、无机化合物、有机聚合物等)组装形成的核壳结构,其中MOFs既可作核,亦可作壳。因结合了核层和壳层两种材料,核壳结构MOFs展现出了优于核层或者壳层的独特性能,例如结构稳定、选择性分离、气体吸附等,为MOFs材料实现工业化应用带来了新的潜力。本文综述了近年来核壳结构MOFs材料的研究进展,介绍了各类构型核壳结构MOFs材料(例如MOF@MOF、MOF@carbon、metal oxide@MOF、polymer@MOF等)的合成方法及应用研究,并对其今后的发展进行了展望。     

手性金属有机骨架材料的合成及其在对映异构体选择性分离中的应用

手性现象在自然界中广泛存在,手性分离在药物研发、农用化学、药理学、环境科学和生物学等诸多领域具有重要意义。手性金属有机骨架化合物材料(MOFs)是一类具有特殊拓扑结构和可设计的孔道结构的新型多孔材料,加之其比表面积高、孔隙率大、热稳定性良好和溶剂耐受性好等特性,使得MOFs在分析化学领域的应用与研究日益深入。本文简要综述了手性MOFs的合成方法,着重讨论了手性MOFs在对映异构体选择性分离方面的应用及相关机理,最后对该类材料的发展前景做了展望。     

水分子对金属有机骨架材料结构及性能的影响

金属有机骨架材料(Metal-Organic Frameworks,MOFs)是一种新型有机-无机杂化材料,其在气体的吸附分离、催化、磁学、生物医学等领域表现出诱人的应用前景。但是,在水分子存在的情况下MOFs结构及性能会受到很大的影响,极大的阻碍了其工业化进程。本文系统介绍了水分子对MOFs结构的破坏机理,并从金属和配体两方面总结了在水分子存在的情况下MOFs的稳定性问题;阐述了水分子的吸附机理以及吸附水分子后MOFs性能的变化;并且对水分子影响问题的研究趋势做了展望,以期为今后的研究提供参考。     

Adsorption of ethane, ethylene, propane, and propylene on a magnesium-based metal-organic framework

Separation of olefin/paraffin is an energy-intensive and difficult separation process in petrochemical industry. Energy-efficient adsorption process is considered as a promising alternative to the traditional cryogenic distillation for separating olefin/paraffin mixtures. In this work, we explored the feasibility of adsorptive separation of olefin/paraffin mixtures using a magnesium-based metal-organic framework, Mg-MOF-74. Adsorption equilibria and kinetics of ethane, ethylene, propane, and propylene on a Mg-MOF-74 adsorbent were determined at 278, 298, and 318 K and pressures up to 100 kPa. A dual-site Sips model was used to correlate the adsorption equilibrium data, and a micropore diffusion model was applied to extract the diffusivities from the adsorption kinetics data. A grand canonical Monte Carlo simulation was conducted to calculate the adsorption isotherms and to elucidate the adsorption mechanisms. The simulation results showed that all four adsorbate molecules are preferentially adsorbed on the open metal sites where each metal site binds one adsorbate molecule. Propylene and propane have a stronger affinity to the Mg-MOF-74 adsorbent than ethane and ethylene because of their significant dipole moments. Adsorption equilibrium selectivity, combined equilibrium and kinetic selectivity, and adsorbent selection parameter for pressure swing adsorption processes were estimated. The relatively high values of adsorption selectivity suggest that it is feasible to separate ethylene/ethane, propylene/propane, and propylene/ethylene pairs in a vacuum swing adsorption process using Mg-MOF-74 as an adsorbent.     

Modeling adsorption in metal-organic frameworks with open metal sites: propane/propylene separations

We present a new approach for modeling adsorption in metal-organic frameworks (MOFs) with unsaturated metal centers and apply it to the challenging propane/propylene separation in copper(II) benzene-1,3,5-tricarboxylate (CuBTC). We obtain information about the specific interactions between olefins and the open metal sites of the MOF using quantum mechanical density functional theory. A proper consideration of all the relevant contributions to the adsorption energy enables us to extract the component that is due to specific attractive interactions between the π-orbitals of the alkene and the coordinatively unsaturated metal. This component is fitted using a combination of a Morse potential and a power law function and is then included into classical grand canonical Monte Carlo simulations of adsorption. Using this modified potential model, together with a standard Lennard-Jones model, we are able to predict the adsorption of not only propane (where no specific interactions are present), but also of propylene (where specific interactions are dominant). Binary adsorption isotherms for this mixture are in reasonable agreement with ideal adsorbed solution theory predictions. We compare our approach with previous attempts to predict adsorption in MOFs with open metal sites and suggest possible future routes for improving our model.     

金属有机骨架材料在轻烃分离中的应用

金属有机骨架材料(metal-organic frameworks,MOFs)是一种由金属离子或金属簇通过与有机配体自组装而形成的新型材料。近年来,金属有机骨架材料在轻烃(包括甲烷、乙炔、乙烯、乙烷、丙烯和丙烷)分离方面引起了广泛兴趣。本文简要地介绍了多种金属有机骨架材料分离不同轻烃气体的最新研究进展,并对影响分离效果的因素与研究前景进行了总结和展望。     

新型金属有机气凝胶的合成、 表征及气体吸附性能

利用高稳定性的UiO-66系列金属有机骨架多孔材料制备金属有机气凝胶材料, 制得的UiO-66系列金属有机气凝胶材料具有多级孔结构和较高的比表面积, 在气体吸附分离领域具有较大应用潜力. 气体吸附实验结果表明, UiO-66-NH₂金属有机气凝胶材料具有极佳的CO₂吸附性能和CO₂/CH₄分离性能, 通过理想吸附溶液理论计算得出其吸附选择性高达18.3.     

Light Hydrocarbon Separations Using Porous Organic Framework Materials

Light hydrocarbons (C₁–C₃) are used as basic energy feedstocks and as commodity organic compounds for the production of many industrially necessary chemicals. Due to the nature of the raw materials and production processes, light hydrocarbons are generated as mixtures, but the high-purity single-component products are of vital importance to the petrochemical industry. Consequently, the separation of these C₁–C₃ products is a crucial industrial procedure that comprises a significant share of the total global energy consumption per year. As a complement to traditional separation methods (distillation, partial hydrogenation, etc.), adsorptive separations using porous solids have received widespread attention due to their lower energy costs and higher efficiency. Extensive research has been devoted to the use of porous materials such as zeolites and metal-organic frameworks (MOFs) as solid adsorbents for these key separations, owing to the high porosity, tunable pore structures, and unsaturated metal sites present in these materials. Recently, porous organic framework (POF) materials composed of organic building blocks linked by covalent bonds have also shown excellent properties in light hydrocarbon adsorption and separation, sparking interest in the use of these materials as adsorbents in separation processes. This Minireview summarizes the recent advances in the use of POFs for light hydrocarbon separations, including the separation of mixtures of methane/ethane, methane/propane, ethylene/ethane, acetylene/ethylene, and propylene/propane, while highlighting the relationships between the structural features of these materials and their separation performances. Finally, the difficulties, challenges, and opportunities associated with leveraging POFs for light hydrocarbon separations are discussed to conclude the review.     

Liquid-phase adsorption on metal-organic frameworks

This work is focusing on the potential application of metal-organic frameworks as porous materials in heterogeneous catalysis where the substrate is in solution. The understanding of such a liquid-phase heterogeneous catalytic process requires adsorption equilibrium data in solution. For this purpose several metal-organic frameworks were synthesized as reference materials and tested as adsorbents for the adsorption of substrate molecules such as styrene or ethylcinnamate from the liquid phase. The adsorption capacity strongly depends on the polarity of the substrate with respect to the solvent. In several instances solvent and polarity effects are heavily superimposed on the pore size effects. Adsorption isotherms, rates and hydrogenation of the substrates are reported and discussed.     

Host-Guest Interaction in Ethylene and Ethane Separation on Zeolitic Imidazolate Frameworks as Revealed by Solid-State NMR Spectroscopy

The separation of ethane/ethylene mixture by using metal-organic frameworks (MOFs) as adsorbents is strongly associated with the pore size-sieving effect and the adsorbent-adsorbate interaction. Herein, solid-state NMR spectroscopy is utilized to explore the host-guest interaction and ethane/ethylene separation mechanism on zeolitic imidazolate frameworks (ZIFs). Preferential access to the ZIF-8 and ZIF-8-90 frameworks by ethane compared to ethylene is directly visualized from two-dimensional ¹H-¹H spin diffusion MAS NMR spectroscopy and further verified by computational density distributions. The ¹H MAS NMR spectroscopy provides an alternative for straightforwardly extracting the adsorption selectivity of ethane/ethylene mixture at 1.1∼9.6 bar in ZIFs, which is consistent with the IAST predictions.     

New pi-complexation adsorbents for propane-propylene separation

New adsorbents were prepared and tested for the separation of propane-propylene mixtures by adsorption. The ordered mesoporous material SBA-15 was used as the starting material for silver-ion deposition for pi-complexation with propylene. Two different loadings of silver were evaluated. Adsorption equilibrium and kinetic measurements of propane and propylene in the matrix (pure SBA-15) and the silver-modified adsorbents were performed at 323, 343, and 373 K. In this temperature range, the selectivity of propylene in one of the materials (Ag/SBA-15 = 0.5) is in the range 13-22 because the amount of propane adsorbed is very small, 0.095 mmol/g of propane versus 1.12 mmol/g of propylene at 100 kPa and 343 K. The diffusivity of both hydrocarbons is not seriously affected by the introduction of silver into the mesoporous structure.     

Olefin adsorption on silica-supported silver salts--a DFT study

Recent experiments have shown that silver salts supported on mesoporous silicas display excellent adsorption selectivities of ethylene over ethane and propylene over propane. Employing the techniques of density functional theory, we have investigated the fundamental bases of this separation process by examining silver salts dispersed on model silica surfaces. Our model system includes Ag+ cations, their counteranions, silica supports, and surface silanols. Both adsorption geometries and energetics of ethylene and propylene were explored. Our results indicate that the nature of the Ag-olefin interaction is predominantly hybridization between Ag d and olefin pi states, which is supported by analyses of electron density difference plots and density of states. The counteranions, such as NO3- were found to interact strongly with surface silanols through multiple hydrogen bonds but have limited effect on the adsorption energy of olefins on the Ag+ cations. The current work supports recent experiments, which indicate that Ag-salt/silica may be a very promising adsorbent for olefin/paraffin separation.     

Propane/propylene separation by selective olefin adsorption on Cu/SBA-15 mesoporous silica

Samples of mesoporous silica, SBA-15, were prepared under hydrothermal conditions and Cu cations were incorporated into the framework by two different impregnation techniques. The corresponding adsorption/desorption isotherms of propylene, propane, and N₂ were measured to evaluate the material's effectiveness in the separation of propane/propylene mixtures. Adsorption uptake of propylene increased and that of propane decreased in Cu containing samples as compared to the uptakes observed in undoped SBA-15 samples. It was demonstrated that the presence of Cu atoms in the adsorbent lattice led to a greater selectivity towards propylene. Furthermore, the highest level of Cu(I) were obtained in samples prepared by equilibrium impregnation, which in turn improved the olefin/paraffin uptake ratio. Under some working conditions, the amount of propylene adsorbed in selected samples is totally reversible while propane uptake was negligible.