Crystalline Porous Organic Salts: From Micropore to Hierarchical Pores

Crystalline porous organic salts (CPOSs), as an emerging class of porous organic materials, combining the uniform microporous system and distinct polarized channels, have become a highly evolving field of important current interest. The unique ionic bond of a CPOS endows the confined channels with high polarity, making CPOSs distinct from other organic frameworks. CPOSs show many fascinating properties, such as proton conductivity and fast transport of polar molecules, which involve the interaction between highly polarized guest molecules and host frameworks. Substantial progress has been made in the synthesis and applications of CPOSs. Herein, an overview is provided to impart a comprehensive understanding of the link between the synthetic approaches and the resultant microporous structure, the structure–function correlation and the state-of-the-art applications of CPOSs. The enhanced mass-transport performance of hierarchically porous structure in combination with the intrinsic polarized channels of CPOSs is very promising to create new applications and contribute to a new research upsurge. The perspective to construct porous hierarchy within the crystalline porous organic salts is assessed and will open a new research avenue. In the conclusion, the current challenges on the synthesis, structural regulation, and applications of CPOSs and the future of hierarchically porous crystalline organic salts are discussed.     

刚柔嵌段共聚物自组装制备有序孔材料研究进展

综述了刚柔嵌段共聚物自组装机理，以及近年来利用刚柔嵌段共聚物自组装制备有序孔材料的发展状况，指出刚柔嵌段共聚物制备有序孔材料的影响因素，认为刚柔嵌段共聚物自组装有着广阔的应用前景。     

吲哚基掺氮分级多孔炭的制备及其对酸性橙74的吸附性能

以吲哚为碳源、氧化钙为模板耦合KOH活化并调节活化终温,制备出表面掺氮的层状分级多孔炭(HPC_T),研究了其对酸性橙74的吸附性能。结果表明：随着活化温度的提高这种多孔炭的比表面积增大,活化终温为900℃时制得的HPC₉₀₀比表面积高达1629 m²/g。这种炭材料具有相互连接的层状结构,且随着活化温度的提高炭壁层变薄。这种炭材料的表面有丰富的含氮官能团C-NH₂,随着活化温度的提高C-NH₂的含量随之提高。C-NH₂官能团与酸性橙74发生π-π堆积效应或静电相互作用,有利于提高其吸附性能。Freundlich模型能很好地描述HPC_T对染料的吸附过程,在50 mg/L的平衡浓度下HPC₉₀₀对废水中酸性橙74的吸附量超过270 mg/g;拟一级动力学方程能更好的描述HPC_T对酸性橙74的吸附过程,物理吸附为控速步骤。     

Structured Porous Materials via Colloidal Crystal Templating: From Inorganic Oxides to Metals

The formation of nanostructured materials by using colloidal crystals as templates is a relatively new but rapidly growing area of materials science. Colloid crystalline templates are three‐dimensional close‐packed crystals of submicrometer spheres, whose long‐ranged ordered structure is replicated in a solid matrix, to yield materials with ordered pores. These materials hold promise for use as photonic crystals, advanced catalysts, and in a variety of other applications. Here we review the wide range of materials that have been made following the original synthesis of structured porous silica. This method has been recently modified to produce porous metals.     

Synthesis of Engineered Zeolitic Materials: From Classical Zeolites to Hierarchical Core–Shell Materials

The term “engineered zeolitic materials” refers to a class of materials with a rationally designed pore system and active‐sites distribution. They are primarily made of crystalline microporous zeolites as the main building blocks, which can be accompanied by other secondary components to form composite materials. These materials are of potential importance in many industrial fields like catalysis or selective adsorption. Herein, critical aspects related to the synthesis and modification of such materials are discussed. The first section provides a short introduction on classical zeolite structures and properties, and their conventional synthesis methods. Then, the motivating rationale behind the growing demand for structural alteration of these zeolitic materials is discussed, with an emphasis on the ongoing struggles regarding mass‐transfer issues. The state‐of‐the‐art techniques that are currently available for overcoming these hurdles are reviewed. Following this, the focus is set on core–shell composites as one of the promising pathways toward the creation of a new generation of highly versatile and efficient engineered zeolitic substances. The synthesis approaches developed thus far to make zeolitic core–shell materials and their analogues, yolk–shell, and hollow materials, are also examined and summarized. Finally, the last section concisely reviews the performance of novel core–shell, yolk–shell, and hollow zeolitic materials for some important industrial applications.     

Emerging Hierarchical Aerogels: Self‐Assembly of Metal and Semiconductor Nanocrystals

Aerogels assembled from colloidal metal or semiconductor nanocrystals (NCs) feature large surface area, ultralow density, and high porosity, thus rendering them attractive in various applications, such as catalysis, sensors, energy storage, and electronic devices. Morphological and structural modification of the aerogel backbones while maintaining the aerogel properties enables a second stage of the aerogel research, which is defined as hierarchical aerogels. Different from the conventional aerogels with nanowire‐like backbones, those hierarchical aerogels are generally comprised of at least two levels of architectures, i.e., an interconnected porous structure on the macroscale and a specially designed configuration at local backbones at the nanoscale. This combination “locks in” the inherent properties of the NCs, so that the beneficial genes obtained by nanoengineering are retained in the resulting monolithic hierarchical aerogels. Herein, groundbreaking advances in the design, synthesis, and physicochemical properties of the hierarchical aerogels are reviewed and organized in three sections: i) pure metallic hierarchical aerogels, ii) semiconductor hierarchical aerogels, and iii) metal/semiconductor hybrid hierarchical aerogels. This report aims to define and demonstrate the concept, potential, and challenges of the hierarchical aerogels, thereby providing a perspective on the further development of these materials.     

Dependence of Ultrasonic Velocity on Porosity and Pore Shape in Sintered Materials

A new approach to predict the longitudinal and transverse ultrasonic velocities in porous materials is presented. The model is based on a previously derived Young's modulus-porosity correlation assuming spheroidal geometry of the pores. It is also assumed that the Poisson's ratio of porous materials does not change significantly with porosity. The longitudinal and transverse ultrasonic velocities are given as functions of the Young's modulus, Poisson's ratio, density of the pore-free material and of the porosity and axial ratio (z/x) of the spheroidal pores. Experimental data drawn from the literature on different porous sintered materials including SiC, Al₂O₃, YBa₂Cu₃O_7–x , porcelain, sintered iron, Si₃N₄, and sintered tungsten, were used to verify the model. A strong relationship between pore shape and the slope of the ultrasonic velocity–porosity curve was confirmed. In general, the calculated values are in fairly good agreement with the experimental data. When the actual shape (axial ratio) of the pores was known, the approach was shown to predict the experimental data better than a similar model derived by Phani. It is suggested that the present approach, coupled with the measurement of the ultrasonic velocity, may constitute a simple nondestructive technique to gain knowledge of the morphology of the porosity in sintered materials.     

Continuous Covalent Organic Frameworks Membranes: From Preparation Strategies to Applications

Covalent organic frameworks (COFs) are porous crystalline polymeric materials formed by the covalent bonding of organic units. The abundant organic units library gives the COFs species diversity, easily tuned pore channels, and pore sizes. In addition, the periodic arrangement of organic units endows COFs regular and highly connected pore channels, which has led to the rapid development of COFs in membrane separations. Continuous defect-free and high crystallinity of COF membranes is the key to their application in separations, which is the most important issue to be addressed in the research. This review article describes the linkage types of covalent bonds, synthesis methods, and pore size regulation strategies of COFs materials. Further, the preparation strategies of continuous COFs membranes are highlighted, including layer-by-layer (LBL) stacking, in situ growth, interfacial polymerization (IP), and solvent casting. The applications in separation fields of continuous COFs membranes are also discussed, including gas separation, water treatment, organic solvent nanofiltration, ion conduction, and energy battery membranes. Finally, the research results are summarized and the future prospect for the development of COFs membranes are outlined. More attention may be paid to the large-scale preparation of COFs membranes and the development of conductive COFs membranes in future research.     

介孔石墨相氮化碳吸附材料在环境中的应用

石墨相氮化碳(Graphitic carbon nitride,g-C_3N_4)是一种由碳(C)和氮(N)元素组成的共轭聚合物材料,具有平面的三嗪聚合物(Poly(tri-s-triazine))网络结构。比起大部分其他碳材料,氮化碳是富电子体,因而赋予了其特殊的性质。然而目前对于g-C_3N_4的研究主要集中在其相关催化作用(光催化,电催化和光电催化),对于g-C_3N_4的吸附作用的研究相对很少涉及。本文探讨了g-C_3N_4材料在吸附领域中的应用,简要综述了G-C_3N_4的性质、制备方法及其作为吸附材料的应用现状,最后展望了石墨型氮化碳在吸附应用领域的未来发展方向。     

Nitrogen‐Containing Microporous Conjugated Polymers via Carbazole‐Based Oxidative Coupling Polymerization: Preparation,Porosity, and Gas Uptake

Facile preparation of microporous conjugated polycarbazoles via carbazole‐based oxidative coupling polymerization is reported. The process to form the polymer network has cost‐effective advantages such as using a cheap catalyst, mild reaction conditions, and requiring a single monomer. Because no other functional groups such as halo groups, boric acid, and alkyne are required for coupling polymerization, properties derived from monomers are likely to be fully retained and structures of final polymers are easier to characterize. A series of microporous conjugated polycarbazoles ( CPOP‐2–7 ) with permanent porosity are synthesized using versatile carbazolyl‐bearing 2D and 3D conjugated core structures with non‐planar rigid conformation as building units. The Brunauer–Emmett–Teller specific surface area values for these porous materials vary between 510 and 1430 m² g^?1. The dominant pore sizes of the polymers based on the different building blocks are located between 0.59 and 0.66 nm. Gas (H₂ and CO₂) adsorption isotherms show that CPOP‐7 exhibits the best uptake capacity for hydrogen (1.51 wt% at 1.0 bar and 77 K) and carbon dioxide (13.2 wt% at 1.0 bar and 273 K) among the obtained polymers. Furthermore, its high CH₄/N₂ and CO₂/N₂ adsorption selectivity gives polymer CPOP‐7 potential application in gas separation.     

多孔竹炭/二氧化钛纳米复合材料制备及其光催化作用

本工作合成了一种具有高吸附性能和光催化性能的表面改性竹炭/二氧化钛(SMBC/TiO₂)纳米复合材料。通过湿法氧化处理廉价、天然绿色的竹炭(BC), 制备了具有良好吸附性、化学稳定性的表面改性竹炭(SMBC)。经过改性, BC表面生成大量含氧官能团, 因此SMBC粒子易分散于水中, 并且与TiO₂有较强的相互作用, 确保TiO₂均匀地负载在SMBC表面。SMBC/TiO₂比BC/TiO₂有更大的比表面积, 能提供更强的吸附性能。SMBC/TiO₂的饱和吸附容量大约是BC/TiO₂的1.6倍, 是TiO₂的12.1倍。吸附和催化的协同作用使SMBC/TiO₂复合材料降解MB具有更高的光催化活性, SMBC/TiO₂光催化降解MB的速率常数分别是BC/TiO₂ 和TiO₂的7倍和6倍。     

多级开孔壳聚糖海绵的细胞行为分析

使用冰滴为致孔剂制备表面大孔、内部孔洞相连的新型壳聚糖(HPCS)支架,将其与聚乳酸复合制备出三维蜂窝状孔洞结构的复合支架(THCP).对HPCS和THCP进行了表面形貌、力学性能、细胞相容性等方面的表征,并与常规冻干法所制备的壳聚糖(CS)海绵进行了对比.结果表明,在HPCS海绵表面均匀分布着大而开放的孔洞,大孔内部...     

Alternatives to Cryogenic Distillation: Advanced Porous Materials in Adsorptive Light Olefin/Paraffin Separations

As primary feedstocks in the petrochemical industry, light olefins such as ethylene and propylene are mainly obtained from steam cracking of naphtha and short chain alkanes (ethane and propane). Due to their similar physical properties, the separations of olefins and paraffins—pivotal processes to meet the olefin purity requirement of downstream processing—are typically performed by highly energy‐intensive cryogenic distillation at low temperatures and high pressures. To reduce the energy input and save costs, adsorptive olefin/paraffin separations have been proposed as promising techniques to complement or even replace cryogenic distillation, and growing efforts have been devoted to developing advanced adsorbents to fulfill this challenging task. In this Review, a holistic view of olefin/paraffin separations is first provided by summarizing how different processes have been established to leverage the differences between olefins and paraffins for effective separations. Subsequently, recent advances in the development of porous materials for adsorptive olefin/paraffin separations are highlighted with an emphasis on different separation mechanisms. Last, a perspective on possible directions to push the limit of the research in this field is presented.     

Space‐Confined Polymerization: Controlled Fabrication of Nitrogen‐Doped Polymer and Carbon Microspheres with Refined Hierarchical Architectures

The construction of refined architectures plays a crucial role in performance improvement and application expansion of advanced materials. The synthesis of carbon microspheres with a refined hierarchical structure is still a problem in synthetic methodology, because it is difficult to achieve the necessary delicate control of the interior structure and outer shell across the microscale to nanoscale. Nitrogen‐doped multichamber carbon (MCC) microspheres with a refined hierarchical structure are realized here via a surfactant‐directed space‐confined polymerization strategy. The MCC precursor is not the traditional phenolic resol but a new kind of 2,6‐diaminopyridine‐based multichamber polymer (MCP) with a high nitrogen content up to 20 wt%. The morphology and sizes of MCP microspheres can be easily controlled by a dual‐surfactant system. The as‐synthesized MCC with a highly microporous shell, a multichamber inner core, and beneficial N‐doping can serve as a promising supercapacitor material.     

Exploiting the Kubas Interaction in the Design of Hydrogen Storage Materials

Hydrogen adsorption and storage using solid‐state materials is an area of much current research interest, and one of the major stumbling blocks in realizing the hydrogen economy. However, no material yet researched comes close to reaching the DOE 2015 targets of 9 wt% and 80 kg m^?3 at this time. To increase the physisorption capacities of these materials, the heats of adsorption must be increased to ～20 kJ mol^?1. This can be accomplished by optimizing the material structure, creating more active species on the surface, or improving the interaction of the surface with hydrogen. The main focus of this progress report are recent advances in physisorption materials exhibiting higher heats of adsorption and better hydrogen adsorption at room temperature based on exploiting the Kubas model for hydrogen binding: (η²‐H₂)–metal interaction. Both computational approaches and synthetic achievements will be discussed. Materials exploiting the Kubas interaction represent a median on the continuum between metal hydrides and physisorption materials, and are becoming increasingly important as researchers learn more about their applications to hydrogen storage problems.     

Controlling the Length of Conical Pores Etched in Ion‐Tracked Poly(ethylene terephthalate) Membranes

An etching procedure that allows for reproducible control of the length of conically shaped pores etched into poly(ethylene terephthalate) (PET) membranes is developed. At the lower etch temperature used (20 °C), the length of the pore is found to be linearly related to etch time. At the higher etch temperature (30 °C) the etch rate is five times faster and the pores quickly propagate through the entire thickness of the PET membrane. Hence, the lower etch temperature is best for controlling the pore length. Pores etched at this temperature are used to prepare arrays of gold cones where the length of the cones is controlled from 1 to 10 µm. The track‐etch rates and the radial‐etch rates at both of the etch temperatures used are also reported.