Polymers of intrinsic microporosity (PIMs): bridging the void between microporous and polymeric materials

Novel types of microporous material are required for chemoselective adsorptions, separations and heterogeneous catalysis. This concept article describes recent research directed towards the synthesis of polymeric materials that possess microporosity that is intrinsic to their molecular structures. These polymers (PIMs) can exhibit analogous behaviour to that of conventional microporous materials, but, in addition, may be processed into convenient forms for use as membranes. The excellent performance of these membranes for gas separation and pervaporation illustrates the unique character of PIMs and suggests immediate technological applications.     

Recent progress in microporous polymers from thermally rearranged polymers and polymers of intrinsic microporosity for membrane gas separation: Pushing performance limits and revisiting trade-off lines

Polymers are promising materials for gas separation membranes. However, the trade-off relationship between gas permeability and selectivity remains an obstacle for achieving polymer membranes that exhibit high gas permeation with desirable separation efficiency. Improving polymer microporosity is of interest in gas separation membranes to enhance gas transport behavior. Polymer modifications by (a) incorporating intrinsically microporous units and/or (b) increasing chain rigidity can enhance microporosity in conventional polymer membrane materials such as polyimides. These strategies are adopted for new classes of microporous polymers, thermally rearranged (TR) polymers, and polymers with intrinsic microporosity (PIMs), to maximize gas transport properties. Their outstanding gas separation performances have redefined the traditional trade-off lines. This review aims to explore the advances in microporous polymers for gas separation applications. The approaches on TR polymers and PIMs to enhance their microporosity are listed, and their developments are evaluated in the context of revisiting performance limits for industrially relevant gas separation applications.     

多孔聚合物贮氢材料的研究进展

微孔聚合物由于具有较高的比表面积,因此可用作物理吸附贮氢材料.本文通过比较0.1MPa、77K下自具微孔聚合物、超交联聚合物等多孔聚合物与其它多孔贮氢材料(如碳材料、金属有机网络等)的贮氢性能,阐述了比表面积、孔尺寸及孔形貌、与氢气的作用力等因素对多孔聚合物贮氢量的影响,由于合成超交联聚合物的单体多且孔形貌容易控制,因此超交联聚合物成为具有发展潜力的贮氢聚合物.     

The synthesis of polymers of intrinsic microporosity (PIMs)

Polymers of intrinsic microporosity(PIMs) are a class of porous organic polymer(POP) that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to other types of POP, PIMs are not comprised of a network of cross-linked covalent bonds so that they can be dissolved in organic solvents and processed into robust films,coatings or fibres. Here, over twelve years' accumulated research on the synthesis of PIMs is reviewed. To date, three types of polymerisation reaction have been used successfully to prepare PIMs of sufficient molecular mass to form robust self-standing films. These involve the formation of dibenzodioxin, Tr鰃er抯 base and imide linkages between monomeric units. This rapid development of synthetic methods for preparing PIMs has been driven by their rich potential for numerous diverse applications and this synergistic relationship between synthesis and functionality is set to continue.     

The potential of organic polymer-based hydrogen storage materials

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.     

Microporous Polymers as Potential Hydrogen Storage Materials

Microporous organic polymers offer the possibility of storing hydrogen safely at low temperatures and moderate pressures via physisorption. A range of polymers of intrinsic microporosity (PIMs) have been studied. The best PIM to date is based on a triptycene monomer and takes up 2.7% H₂ by mass at 10 bar/77 K. Hypercrosslinked polymers (HCPs) also show promising performance, particularly at pressures >10 bar. The form of the H₂ isotherm is influenced by the micropore distribution, a higher concentration of ultramicropores (pore size <0.7 nm), as found in PIMs, being associated with enhanced low pressure adsorption. The performance of polymers relative to other microporous materials (carbons and metal‐organic frameworks) is compared and promising methods to enhance the hydrogen uptake of microporous polymers are suggested.

     

Two‐Dimensional Microporous Material‐based Mixed Matrix Membranes for Gas Separation

Since the discovery of graphene and its derivatives, the development and application of two‐dimensional (2D) materials have attracted enormous attention. 2D microporous materials, such as metal‐organic frameworks (MOFs), covalent organic frameworks (COFs), graphitic carbon nitride (g‐C₃N₄) and so on, hold great potential to be used in gas separation membranes because of their high aspect ratio and homogeneously distributed nanometer pores, which are beneficial for improving gas permeability and selectivity. This review briefly summarizes the recent design and fabrication of 2D microporous materials, as well as their applications in mixed matrix membranes (MMMs) for gas separation. The enhanced separation performances of the membranes and their long‐term stability are also introduced. Challenges and the latest development of newly synthesized 2D microporous materials are finally discussed to foresee the potential opportunities for 2D microporous material‐based MMMs.     

Dibenzomethanopentacene-Based Polymers of Intrinsic Microporosity for Use in Gas-Separation Membranes

Dibenzomethanopentacene (DBMP) is shown to be a useful structural component for making Polymers of Intrinsic Microporosity (PIMs) with promise for making efficient membranes for gas separations. DBMP-based monomers for PIMs are readily prepared using a Diels–Alder reaction between 2,3-dimethoxyanthracene and norbornadiene as the key synthetic step. Compared to date for the archetypal PIM-1, the incorporation of DBMP simultaneously enhances both gas permeability and the ideal selectivity for one gas over another. Hence, both ideal and mixed gas permeability data for DBMP-rich co-polymers and an amidoxime modified PIM are close to the current Robeson upper bounds, which define the state-of-the-art for the trade-off between permeability and selectivity, for several important gas pairs. Furthermore, long-term studies (over ≈3 years) reveal that the reduction in gas permeabilities on ageing is less for DBMP-containing PIMs relative to that for other high performing PIMs, which is an attractive property for the fabrication of membranes for efficient gas separations.     

热致相分离法制备聚烯烃微孔膜研究进展

非极性及弱极性的结晶高聚物常温下无合适的良溶剂,所以无法使用传统的非溶剂致相分离法制取微孔膜,而近年来发展的热致相分离法解决了这一问题。研究发现聚乙烯、聚丙烯、乙烯．乙烯醇共聚物、乙烯．丙烯酸共聚物、聚(4-甲基-1-戊烯)等聚烯烃是可采用热致相分离法制备微孔膜的材料。本文综述了近年来在热致相分离法制备聚烯烃微孔膜方面的研究进展,重点介绍各种制膜材料(聚合物、稀释剂、萃取剂和助剂)与各种制膜工艺对制得的聚烯烃微孔膜孔径、膜通量和非对称结构等的影响。     

多孔材料化学:从无机微孔化合物到金属有机多孔骨架

本文主要从无机微孔化合物和金属有机多孔骨架的合成化学和结构化学这两方面来介绍多孔材料化学的研究进展。多孔材料是一类具有规则孔结构的固态化合物,它们在催化、分离、离子交换等工业领域有着广泛的应用。硅铝酸盐是最为人们所熟知的微孔分子筛,经过半个多世纪的发展,人们又相继开发出磷酸盐、砷酸盐、锗酸盐、亚磷酸盐、硫酸盐、亚硒酸盐以及金属硫化物等类沸石无机微孔化合物。近十多年来,配位聚合物与金属有机多孔骨架开始大量兴起,为微孔化合物的多样化与组成的复杂性增添了新的领域。     

Effect of non-ionic surface active agents on TEOS-derived sols,gels and materials

The sol-gel process, starting from tetraethylorthosilicate precursor, is a suitable technique for the preparation of silica thin films. The use of specific organic additives, like non ionic surface-active agents, drastically modifies the gelation process and allows the preparation of microporous materials with a high microporous volume. The effects of additives on the sol, gel and material characteristics have been investigated by several methods such as ²⁹Si NMR, QELS, SAXS (for sols and gels), and N₂ adsorption, FESEM (for fired materials). It appears that the interactions of surface active agents with TEOS derived species limit condensation reactions and particle growing. A brittle gel structure is generated which leads to highly porous microporous silica after the elimination of organic chains by thermal treatment at 450°C. The material porous texture (specific surface area, pore size distribution and porous volume) can be varied especially by varying the surface active agent chain length and quantity. This kind of sol-gel system is suitable to prepare microporous silica membranes candidate for gas separation or catalytic reactor applications.     

Discovery and development of microporous metal carboxylates

We have found a form of copper(II) terephthalate that occluded an enormous amount of gases such as N2, Ar, O2, and Xe. Copper(II) terephthalate is the first metal complex found capable of adsorbing gases. This complex has opened a new field of adsorbent chemistry and is recognized as a leader in the construction of microporous metal complexes. In extending the route for the synthesis of microporous complexes, we obtained many new porous materials that are widely recognized as useful materials for applications in areas such as gas storage, molecular sieves, catalysis, inclusion complexes, and surface science.     

具有DFT拓扑结构的有机-无机杂化材料(C2N2H10)[Zn2(PO4)2]的合成与结构表征

以氯化锌和磷酸为原料, 二亚乙基三胺(DETA)为模板剂, 通过水热法合成了一种具有空旷骨架结构的有机-无机杂化磷酸锌化合物. 晶体结构分析结果表明, 该化合物属于四方晶系, P42bc空间群, 晶胞参数a=b=1.46850(2) nm, c=0.89274(2) nm, α=β=γ=90°, V=1.92519(6) nm3, Z=8, Dc=2.641 g/cm3. 并对其进行了IR光谱和TG-DTA热分析研究. 荧光光谱分析结果表明, 化合物(C2N2H10)[Zn2(PO4)2]用451 nm的光激发时, 发射峰位置在665~688 nm之间.     

热致相分离法制备聚合物微孔材料

热致相分离是一种制备聚合物微孔材料的有效方法。本文介绍了聚合物初始浓度、聚合物分子量、稀释剂、冷却速率、萃取剂、聚合物密度等因素对热致相分离法制备聚合物微孔材料的影响,并对热致相分离法制备新型微孔材料的最新研究进展进行了综述。     

微孔镧系配位聚合物

微孔配位聚合物与通常的微孔无机材料相比, 具有非常明显的优势. 而镧系离子特殊的光学和磁学性质, 更使得微孔镧系配位聚合物的研究成为热点. 本文简要地报道了微孔镧系配位聚合物的研究现状, 对一些微孔镧系配位聚合物的结构特点进行了描述, 讨论了影响微孔配位聚合物形成的主要因素. 一般来说, 线型配体往往能很好地将金属离子连接起来, 得到理想的微孔镧系配位聚合物; 选择合适的第二配体, 有利于构筑结构新颖的微孔镧系配位聚合物; 镧系收缩对能否形成微孔配位聚合物的影响并不明显, 只是轻稀土离子往往倾向于多结合一些小分子配体来满足更高的配位数.     

Microwave‐assisted Ionothermal Synthesis and Characterization of Zeolitic Imidazolate Framework‐8

The zeolitic imidazolate framework‐8 (ZIF‐8) was successfully synthesized using ionic liquids as structure‐directing agent under microwave irradiation. Ionic liquids are green solvents with low vapour pressure and good thermal stability. They are appropriate templates for microporous materials and ideal microwave absorbers. The microwave‐assisted ionothermal synthesis applied in this paper was expected to be a promising method for the preparation of microporous materials. Results showed that the as‐synthesized samples (300–500 nm in diameter) could be synthesized in a short time (60 min) and possessed regular morphology, stable structure and high thermal stability (up to 720°C in argon atmosphere). Nitrogen adsorption‐desorption test illustrated that samples produced by microwave heating had a higher surface area. Carbon dioxide adsorption test indicated that the samples synthesized by microwave heating had better carbon dioxide adsorption ability than those by conventional heating.     

Metamorphosis of ordered mesopores to micropores: periodic silica with unprecedented loading of pendant reactive organic groups transforms to periodic microporous silica with tailorable pore size

Ordered porous silicas with unprecedented loadings of pendant vinyl groups have been synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and triethoxyvinylsilane (TEVS) under basic conditions in the presence of cetyltrimethylammonium surfactant. The resulting organosilicate-surfactant composites exhibited at least one low-angle X-ray diffraction (XRD) peak up to the TEVS:TEOS molar ratio of 7:3 (70% TEVS loading) in the synthesis gel. The surfactant was removed from these composites without any structural collapse. Nitrogen adsorption provided strong evidence of the presence of uniformly sized pores and the lack of phase separation up to TEVS:TEOS ratios as high as 13:7 (65% TEVS loading), whereas (29)Si MAS NMR and high-resolution thermogravimetry showed essentially quantitative incorporation of the organosilane. Thus, a hitherto unachieved loading level for pendant groups, considered by many to be impossible to achieve for stable organosilicas because of the expected framework connectivity constraints, has been obtained. The resulting vinyl-functionalized silicas exhibited gradually decreasing pore diameter (from 2.8 to 1.7 nm for TEVS loadings of 25-65%) and pore volume as the loading of pendant groups increased, but the specific surface area was relatively constant. Because of the reactivity of vinyl groups, ordered silicas with very high loadings of these groups are expected to be robust starting materials for the synthesis of other organic-functionalized ordered microporous materials. Herein, we demonstrate that these starting materials can also be transformed via calcination into ordered microporous silicas with pore diameters tailorable from 2.5 to as little as 1.4 nm simply by using an appropriate loading of the vinyl-functionalized precursor. This ease of the micropore size adjustment and the attained degree of structural ordering (as judged from XRD) have not been reported before. The novel ordered microporous materials reported herein are promising as adsorbents and catalyst supports.     

Facile synthesis of microporous carbon through a soft-template pathway and its performance in desulfurization and denitrogenation

Wormlike/lamellar microporous carbons were prepared by using long alkyl chain primary amine hydrochloride as the template and resorcinol/formaldehyde as the carbon source under highly acidic conditions. The template can be eliminated by high temperature treatment under an inert atmosphere. The obtained carbon materials were characterized by N2 adsorption-desorption, transmission electron microscopy, thermogravimetry and scanning electron microscopy. The results show that dodecylamine hydrochloride surfactant can be used as the template of wormlike micropores structure while octadecylamine hydrochloride results in both lamellar and wormlike micropores. The obtained carbon materials have the similar pore size in the range of 0.5~0.59 nm, but with various morphologies such as monolith, spheres, and coralline. The microporous carbon obtained from dodecylamine hydrochloride surfactant shows good adsorption performance to remove the refractory sulfur compounds and nitrogen-containing compounds in fuel.     

Selective Transport of Lead(II) and Strontium(II) Through a Crown Ether-Based Polymer Inclusion Membrane Containing Dialkylnaphthalenesulfonic Acid

New polymer inclusion membranes (PIMs) containing 18-membered crownethers and dialkylnaphthalenesulfonic acid are proposed for Sr2+ and Pb2+removal from nitric acid solutions. The influence of source phasecomposition and stripping agents was characterized and permeabilitycoefficients were calculated. The PIMs are easy to prepare and may be usefulin separation and concentration procedures for these cations from complexmixtures such as nuclear waste. Long-term stability was obtained for atleast several weeks of constant use during which no significant change ofpermeability was observed.     

MICROPOROUS INORGANIC MEMBRANES

Recent development in microporous inorganic membranes represents a significant advance in materials for separation and chemical reaction applications. This paper provides an in-depth review of synthesis and properties of two groups (amorphous and crystalline) of microporous inorganic membranes. Amorphous microporous silica membranes can be prepared by the sol-gel and phase separation methods. Flat sheet, tubular and hollow fiber amorphous carbon membranes have been fabricated by various pyrolysis methods from polymer precursors. A large number of synthesis methods have been developed to prepare good quality polycrystalline zeolite membranes. Several techniques, including vapor and liquid approaches, are reviewed for pore structure modification to prepare microporous inorganic membranes from mesoporous inorganic membranes. Chemical, microstructural and permeation properties of these microporous membranes are summarized and compared among the several microporous membranes discussed in this paper. Theory for gas permeation through microporous membranes is also reviewed, with emphasis on comparison of theoretical with the experimental data. These inorganic microporous membranes offer excellent separation properties by the mechanisms of preferential adsorption, selective configurational diffusion or molecular sieving.