MOFs基材料制备混合基质膜用于O2/N2分离的研究进展

金属有机框架（metal-organic frameworks,MOFs）材料具有多孔、孔径易于调节、高的比表面积等优点，用于改善传统聚合物膜的缺点，制得的混合基质膜具有较好的气体分离性能。混合基质膜中的填料和聚合物基质的性质、填料和聚合物基质间的界面相互作用等影响着膜的气体渗透性和选择性，本文着重介绍混合基质膜中填料尺寸、形貌和聚合物性质对混合基质膜气体分离性能的影响，以及相应的改性方法，为氧氮分离的MOFs基混合基质膜提供新的思路。     

MOF基混合基质气体分离膜界面作用调控研究进展

混合基质膜结合了无机填充材料和聚合物组分的双重优势，被认为是一种可同时增加渗透性和选择性的新型方法，有望解决传统聚合物膜的Trade-off效应。混合基质膜的气体分离性能主要依赖无机填充材料的分子筛分性质和高分子本身的化学结构，因此适当选择无机填充材料对于制备高性能的混合基质膜十分重要。金属有机骨架(MOF)作为一种新型多孔填料，具有比表面积大、密度小、孔隙率高和孔尺寸可调等优点，因此在气体吸附分离和气体储存等领域应用广泛，为新型混合基质膜带来良好的发展机遇。但混合基质膜的分离性能并不是简单地两相性能相加，在大多数情况下分离性能远低于材料模拟的预测理论值，造成这种非理想性的关键因素之一是MOF晶体和聚合物之间的界面缺陷，这可能导致界面非选择性空隙的形成、聚合物硬化和孔隙堵塞等界面问题，降低膜的分离性能。因此，实现MOF-聚合物基质间的界面作用调控以改善界面相容性是充分发挥MOF基混合基质膜气体分离潜力的关键。本工作综述了MOF基混合基质膜近五年关于不同类型界面作用调控的方法及策略，及其对气体分离性能的影响。最后，总结构建的界面作用对于混合基质膜性能的正面影响并提出当中存在的问题，为混合...     

功能化Zr-MOF强化混合基质膜CO2分离

混合基质膜（MMMs）在气体分离领域具有良好的应用前景,金属有机框架（MOFs）由于具有高孔隙率和有机连接基团,常被用作填料制备MMMs。但由于MOFs与聚合物的界面相容性问题,MMMs的气体分离性能提升受到限制。本文合成了功能化的Zr-MOF（UiO-66-AC）,并利用其与聚醚共聚酰胺（Pebax）共同制备了混合基质膜。填料中引入的羰基和羧基等基团提供了MOFs与聚合物基质之间较强的界面相互作用。与纯Pebax膜相比,UiO-66-AC/Pebax MMMs的气体渗透性能得到了显著提高。当填料质量分数为6%时,膜的CO₂渗透系数为102.4 Barrer,CO₂/N₂和CO₂/CH₄选择性分别为90.6和26.0,CO₂/N₂分离性能突破了Robeson上限(2008),表明该混合基质膜在CO₂的分离应用上具有潜力。     

混合基质膜在碳捕集领域的研究进展

膜分离技术因其低成本、低能耗及高效率的优势被认为是最具有前景的碳捕集技术之一。混合基质膜结合了有机材料与无机材料两方面的优势，是同时提升渗透性和选择性的有效手段。本文从气体在混合基质膜中的传递机制出发，以常见的无孔型与多孔型无机填料为基础，总结了近年来混合基质膜在二氧化碳捕集领域的研究进展，介绍了不同类型的填料在高分子基质中所起到的微结构调节作用，并着重阐述了在混合基质膜制备过程中无机填料与高分子基质之间所存在的相容性问题及其解决方法。最后，提出混合基质膜应在继续致力于填料结构设计、填料分散、构效关系等方面的同时，加强二维填料、微囊填料和促进传递机制等方面的研究。     

含开放金属位点MIL-101(Cr)掺杂的混合基质膜制备及其CO2分离性能

以结构中含有开放金属位点的MIL-101（Cr）作为填料与3种不同的聚合物复合制备了混合基质膜,从填料结构、聚合物性质及填料-聚合物界面状况等角度对混合基质膜的CO₂分离性能进行了分析。结果表明,由于MIL-101（Cr）较大的孔道尺寸以及结构中开放金属Cr（Ⅲ）位点与CO₂分子间的Lewis酸碱作用,其掺杂能够同时显著提高PSF膜的CO₂通量及分离因子。而当聚合物渗透性及选择性较高时,MIL-101（Cr）的掺杂仅提高了气体通量,CO₂分离因子则略有降低。当聚合物分子链柔性较大时,MIL-101（Cr）的表面孔道会被分子链堵塞,造成混合基质膜气体通量的显著下降。     

Pebax/a-MoS2/MIP-202混合基质膜的制备及CO2分离性能

为了获得高性能的CO₂/N₂分离膜,把空气中氧刻蚀的二硫化钼（a-MoS₂）和金属有机框架材料MIP-202通过机械力化学反应制备的双功能填料作为分散相,聚醚嵌段酰胺（Pebax-1657）作为连续相,采用溶液浇铸法制备了Pebax/a-MoS₂/MIP-202混合基质膜。采用FT-IR表征了填料的化学结构,借助ATR-FTIR、SEM、TG和力学性能测试表征了混合基质膜的化学结构、微观形貌结构、热稳定性和物理力学性能。研究了水含量、双功能填料配比、含量、膜两侧压差和操作温度对膜气体分离性能的影响,并考察了模拟烟道气（CO₂/N₂体积比15/85）条件下混合基质膜的长时间运行稳定性。结果表明：在温度为25℃、膜两侧压差为0.1 MPa的操作条件下,a-MoS₂与MIP-202质量比为5∶5和双功能填料含量为6%（质量）时,膜的气体分离性能达到最优,CO₂渗透性和CO₂/N₂选择性分别为380 Barrer和124.7,超过了2019年McKeown等提出的上限值。连续测试360 h后,混合基质膜的性能没有明显降低,其平均CO₂渗透性和CO₂/N₂选择性分别为358 Barrer和120.1。这主要是由于a-MoS₂和MIP-202协同提高了膜的气体分离性能。     

Pebax/a-MoS2/MIP-202混合基质膜的制备及CO2分离性能

为了获得高性能的CO₂/N₂分离膜,把空气中氧刻蚀的二硫化钼（a-MoS₂）和金属有机框架材料MIP-202通过机械力化学反应制备的双功能填料作为分散相,聚醚嵌段酰胺（Pebax-1657）作为连续相,采用溶液浇铸法制备了Pebax/a-MoS₂/MIP-202混合基质膜。采用FT-IR表征了填料的化学结构,借助ATR-FTIR、SEM、TG和力学性能测试表征了混合基质膜的化学结构、微观形貌结构、热稳定性和物理力学性能。研究了水含量、双功能填料配比、含量、膜两侧压差和操作温度对膜气体分离性能的影响,并考察了模拟烟道气（CO₂/N₂体积比15/85）条件下混合基质膜的长时间运行稳定性。结果表明：在温度为25℃、膜两侧压差为0.1 MPa的操作条件下,a-MoS₂与MIP-202质量比为5∶5和双功能填料含量为6%（质量）时,膜的气体分离性能达到最优,CO₂渗透性和CO₂/N₂选择性分别为380 Barrer和124.7,超过了2019年McKeown等提出的上限值。连续测试360 h后,混合基质膜的性能没有明显降低,其平均CO₂渗透性和CO₂/N₂选择性分别为358 Barrer和120.1。这主要是由于a-MoS₂和MIP-202协同提高了膜的气体分离性能。     

GO-TSC/聚酰亚胺混合基质膜的制备及气体分离性能研究

使用氨基硫脲（TSC）对氧化石墨烯（GO）进行改性,制备GO-TSC层状复合材料。随后,将该复合材料加入到Matrimid^®5218（PI）基质中,制备用于二氧化碳分离的混合基质膜（MMMs）。通过TGA、SEM及气体分离性能测试考察了GO-TSC对膜热稳定性、结构和气体分离性能等的影响。SEM结果显示GO-TSC可均匀分散在聚合物基质上并与基质紧密结合;TGA结果显示混合基质膜在250 ℃以上仍保持稳定。与纯PI膜相比,MMMs显著增强了二氧化碳的渗透性。GO-TSC中所含的氨基与二氧化碳具有良好的亲和力,增加的碱性位点可以有效地转运二氧化碳。GO-TSC的层状结构增加了气体的传输路径,不利于大动态直径气体（甲烷、氮气）的通过,从而提高了分离性能。GO-TSC负载量为0.75%（质量分数）时混合基质膜的分离性能最佳。相比较纯PI膜,混合基质膜的二氧化碳渗透系数和二氧化碳/甲烷、二氧化碳/氮气分离系数分别提高了42.16%、95.79%和83.72%。     

金属有机骨架混合基质水处理分离膜研究进展

金属有机骨架（MOFs）晶体由无机金属离子和有机配体通过自组装合成,具有高的孔隙率和可调节的窗口尺寸,可使MOFs混合基质膜在水处理时同步获得高通量和高截留率,有望突破传统分离膜的渗透性和选择性之间此消彼长的trade-off效应。本文综述了MOFs的典型构造、影响MOFs混合基质膜性能的关键因素、MOFs混合基质膜的制备方法、MOFs颗粒改善混合基质膜水传输和溶质分离性能的原理以及MOFs混合基质膜在水处理微滤/超滤、纳滤/反渗透和正渗透领域的最新研究进展。最后总结了MOFs混合基质膜在水处理领域的未来发展亟待解决的关键问题,主要包括高性能、低成本膜的可控制备、膜结构和性能之间定量构效关系的深入探索以及如何拓宽其应用范围等,对加快MOFs混合基质膜的产业化进程具有指导意义。     

金属有机框架/聚酰亚胺混合基质膜的研究进展

聚酰亚胺是一种具有高热稳定性和良好成膜性的高分子材料,但聚酰亚胺膜在气体分离方面的应用效果较差。金属有机框架材料在气体分离中有较好的应用前景。用两者制备的混合基质膜,可以综合其各自的优点,提高对气体的选择渗透性。本文综述了采用金属有机框架材料、金属有机框架材料改性以及添加其他聚合物基底制备混合基质膜,对气体分离效果的影响,并对这种混合基质膜在气体分离领域的使用效果进行了分析,对这种混合基质膜面临的挑战进行了讨论与展望。     

Zeolite imidazolate framework (ZIF)-based mixed matrix membranes for CO2 separation: A review

Mixed matrix membranes (MMMs), which combine the good separation performance of inorganic materials with the low cost of polymers, have emerged as a research hotspot for gas separation membranes. Zeolite imidazolate frameworks (ZIFs) are widely used as fillers to prepare MMMs owing to their advantageous characteristics, such as adjustable pore channels, unsaturated sites, and easy functionalization. For MMMs, three directions can be employed as criteria for improvement compared with pristine polymeric membranes. In this article, the progress of ZIF-based MMMs is reviewed from the aspects of sole-ZIF-based MMMs and modified ZIF-based MMMs. Both strategies improve the separation performance through different improvement directions and mechanisms. Our analysis shows that the synergistic effect of the modified filler can change the structure of the membranes, such as by improving the filler–polymer interface voids, which provides a foundation to overcome the trade-off effect to a certain extent. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48968.     

Perspective of mixed matrix membranes for carbon capture

Polymeric membrane-based gas separation has found wide applications in industry, such as carbon capture, hydrogen recovery, natural gas sweetening, as well as oxygen enrichment. Commercial gas separation membranes are required to have high gas permeability and selectivity, while being cost-effective to process. Mixed matrix membranes (MMMs) have a composite structure that consists of polymers and fillers, therefore featuring the advantages of both materials. Much effort has been made to improve the gas separation performance of MMMs as well as general membrane properties, such as mechanical strength and thermal stability. This perspective describes potential use of MMMs for carbon capture applications, explores their limitations in fabrication and methods to overcome them, and addresses their performance under industry gas conditions.     

An atomistic simulation towards molecular design of silica polymorphs nanoparticles in polysulfone based mixed matrix membranes for CO2/CH4 gas separation

Incorporation of inorganic fillers into Polysulfone (PSF) to constitute mixed matrix membranes (MMMs) has become a viable solution to prevail over limitations of the pristine materials in natural gas sweetening process. Nevertheless, preparation of MMMs without defects and empirical investigation of membrane that exhibits characteristic of improved CO₂/CH₄ separation performance at experimental scale are difficult that require prior knowledge on compatibility between the filler and polymer. A computational framework has been conducted to construct validated PSF based MMMs using silica (SiO₂) as inorganic fillers. It is known that nanosized SiO₂ can coexist in varying polymorph configurations (ie, α-Quartz, α-Cristobalite, α-Tridymite) but molecular simulation study of SiO₂ polymorphs to form MMMs is limited. Therefore, this work is a pioneering study to elucidate feasibility in facile utilization of polymorphs to improve gas separation performance of MMMs. Physical properties and gas transport behavior of the simulated PSF based MMMs with different SiO₂ polymorphs and loadings have been elucidated. The optimal MMM has been found to be PSF/25 wt% α-Cristobalite at 55°C. The success in molecular simulation has shed light on how computational tools can provide understandings at molecular level to elucidate compatibility between varying pristine materials to MMMs for natural gas processing.     

Synthesis and Characterization of Polyimide Mixed Matrix Membranes

Polyimides of Matrimid 5218 and P84 as backbone and different fillers including silica aerosil, zeolite 4A, carbon nanotubes, and carbon molecular sieves were used to synthesize flat mixed matrix membranes (MMMs). Effects of different polymer types and concentrations, different filler types and contents, and fabrication procedure were investigated. Scanning Electron Microscopy (SEM) analysis showed acceptable connections between the two phases and the MMMs performed higher performance compared to the polymeric membranes. Thermal treatment of the MMMs, as a defect repairing technique, was found very effective. Performed pervaporation and gas permeation experiments showed better separation performances of the MMMs with respect to those of the neat polymeric membranes. The results showed up to seven and two times increment in separation factors of MMMs regarding to neat polymeric membranes for pervaporation and gas separation experiments, respectively, while permeation rates nearly remained constant indicating effectiveness of the proper filler incorporation within polymer matrices approach.     

Various Techniques for Preparation of Thin‐Film Composite Mixed‐Matrix Membranes for CO2 Separation

The application of thin‐film composite mixed‐matrix membranes (TFC‐MMMs) for gas separation is widely considered as an efficient separation technology. The principal methods for the preparation of TFC‐MMMs are dip‐coating, phase inversion, and interfacial polymerization comprising different types of support layers. These methods influence the CO₂ permeation over the selective and support layers. A comprehensive review is provided for capturing new details of progress achieved in developing TFC‐MMMs with detailed performance of gas separation in the previous few years. Various preparation techniques of TFC‐MMMs and their effect on the gas separation performance of the prepared membranes are described.     

Investigation of the effect of functionalized carbon nanotube and graphene oxide in guar gum-based mixed matrix membrane for gas separation application

The present study deals with preparing mixed matrix membranes (MMMs), a new polysaccharide-based natural polymer used as a matrix with functionalized carbon nanotubes (FCNTs) and graphene oxide (GO) used as an inorganic filler. This work identified the effect of the inorganic fillers (FCNTs or GO) with naturally occurring polymer for gas separation. The incorporation of fillers improves the gas separation performance of MMMs. In GG/FCNTs MMMs, the selectivities of CO₂/N₂ and CO₂/H₂ were enhanced by 55.24% and 57.89%, respectively. Moreover, in GG/GO MMMs, the selectivities of CO₂/N₂ and CO₂/H₂ were improved by 99.50% and 50%, respectively. The membrane was characterized by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The SEM analysis of GG/GO MMMs reveals layered structure, and GG/FCNTs MMMs create passages to transport gases. The Universal testing machine (UTM) is used to analyze the mechanical properties of pristine and modified membranes.     

Membranes for CO2 /CH4 and CO2/N2 Gas Separation

Membrane technology has emerged as a leading tool worldwide for effective CO₂ separation because of its well-known advantages, including high surface area, compact design, ease of maintenance, environmentally friendly nature, and cost-effectiveness. Polymeric and inorganic membranes are generally utilized for the separation of gas mixtures. The mixed-matrix membrane (MMM) utilizes the advantages of both polymeric and inorganic membranes to surpass the trade-off limits. The high permeability and selectivity of MMMs by incorporating different types of fillers exhibit the best performance for CO₂ separation from natural gas and other flue gases. The recent progress made in the field of MMMs having different types of fillers is emphasized. Specifically, CO₂/CH₄ and CO₂/N₂ separation from various types of MMMs are comprehensively reviewed that are closely relevant to natural gas purification and compositional flue gas treatment     

Construction of molecule-selective mixed matrix membranes with confined mass transfer structure

Extraordinary mass transfer phenomenon is usually found when the small molecules pass through a confined structure, whose effective size is commensurate with the mean free path of the molecules. Small changes in the confined mass transfer structure (including size, morphology and properties) will lead to significant fluctuations of the mass transfer coefficient. The mass transfer of the penetrant molecules in the dense membranes for pervaporation, gas separation and so on, is located in the scope of confined mass transfer. Incorporating nanofillers into polymer matrix to construct mixed matrix membranes (MMMs) is an effective approach to tune the confined mass transfer structure and enhance the performance of the widely used polymeric membranes. This reviewfocuses on the construction andmanipulation of the confined structure in the polymeric membranes via incorporating one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) fillers.The comparison of the MMMs for pervaporation is summarized, and the research prospective of the MMMs is provided.