Electroactive Metalorganic Frameworks

Crystalline and porous framework materials with appreciable charge carrier mobility hold promise as a new semiconducting platform. Through the concepts of reticular chemistry, numerous two- and three-dimensional crystalline and porous frameworks with encoded properties enabling significant electrical conductivity are in reach. Prominent members of this group are the metal-organic frameworks (MOFs), which recently created scientific excitement as highly conductive materials. Herein, we discuss the recent prominent examples reported for electrically conducting MOFs with regards to their synthesis, structural and electronic properties and possible applications. We frame our discussion according to structural features of the MOFs, covering both layered 2D and 3D frameworks.     

Advances in the Structural Strategies of the Self-Assembly of Photoresponsive Supramolecular Systems

Photosensitive supramolecular systems have garnered attention due to their potential to catalyze highly specific tasks through structural changes triggered by a light stimulus. The tunability of their chemical structure and charge transfer properties provides opportunities for designing and developing smart materials for multidisciplinary applications. This review focuses on the approaches reported in the literature for tailoring properties of the photosensitive supramolecular systems, including MOFs, MOPs, and HOFs. We discuss relevant aspects regarding their chemical structure, action mechanisms, design principles, applications, and future perspectives.     

MOF复合材料在气体吸附分离中的研究进展

作为一种新型多孔材料,金属有机骨架（metal-organic framework, MOF）材料因其具有高孔隙率、大比表面积、孔尺寸高度可调、结构多样等优点,近年来在气体吸附与分离领域显示出广阔的应用前景。然而,在MOF材料的工业化进程中,仍存在稳定性差等问题需要解决。将MOF材料与其他功能材料进行复合,实现不同材料间的协同效应,在保证吸附分离性能的同时,显著提升MOF材料的结构稳定性。本综述概述了MOF基复合材料的构筑策略,与MOFs构筑复合材料的材料,包括碳基材料、离子液体、MOFs、分子筛等。分析了各种MOF复合材料在气体吸附与分离领域的应用进展,并对该研究方向进行了展望。     

Progress of superhydrophobic porous materials

Porous materials such as metal organic framework materials (MOFs), covalent organic framework materials (COFs), organic porous polymers (POPs), etc., have been used widely used in the fields of separation, catalysis, gas storage and drug release due to their diversity, designability, controllability and functionalization of pores. Despite these promising applications, some of the porous materials suffer from moisture-sensitivity and instability in aqueous media due to their inherent structural features. To overcome this problem, endowing them with hydrophobicity is an effective strategy. However, designing superhydrophobic porous materials has certain challenges. In this work, the progress of MOFs, COFs and POPs with (super-)hydrophobic property is introduced. Issues related to their design strategy, structures, and practical applications such as catalysis, oil/water separation and gas storage and separation were analyzed. Additionally, the current problems and the future research directions of the hydrophobic porous materials were discussed.     

超疏水多孔材料的研究进展

多孔材料如金属有机框架材料（MOFs）、共价有机框架材料（COFs）、有机多孔聚合物（POPs）等由于构筑单元的多样性、可设计性,孔道的可调控性和功能化,已经被广泛用于分离、催化、气体储存以及药物释放等领域。尽管如此,这些多孔材料固有的结构特征让它们普遍对水气非常敏感,最严重时多孔结构在水溶液环境下会坍塌。为解决此类问题,制备疏水的多孔材料是一个非常好的策略。然而,设计超疏水多孔材料具有一定的挑战。介绍了具有（超）疏水性能的MOFs、COFs和POPs的发展现状,对超疏水多孔材料合成思路和结构特点进行了分析,对这类材料在催化、油水分离、气体吸附和分离等方面的应用进行了总结,并进一步探讨了此类材料存在的问题和发展方向。     

Tuning the topology and functionality of metal-organic frameworks by ligand design

Metal-organic frameworks (MOFs)-highly crystalline hybrid materials that combine metal ions with rigid organic ligands-have emerged as an important class of porous materials. The organic ligands add flexibility and diversity to the chemical structures and functions of these materials. In this Account, we summarize our laboratory's experience in tuning the topology and functionality of MOFs by ligand design. These investigations have led to new materials with interesting properties. By using a ligand that can adopt different symmetry conformations through free internal bond rotation, we have obtained two MOFs that are supramolecular stereoisomers of each other at different reaction temperatures. In another case, where the dimerized ligands function as a D(3)-Piedfort unit spacer, we achieve chiral (10,3)-a networks. In the design of MOF-based materials for hydrogen and methane storage, we focused on increasing the gas affinity of frameworks by using ligands with different geometries to control the pore size and effectively introduce unsaturated metal centers (UMCs) into the framework. Framework interpenetration in PCN-6 (PCN stands for porous coordination network) can lead to higher hydrogen uptake. Because of the proper alignment of the UMCs, PCN-12 holds the record for uptake of hydrogen at 77 K/760 Torr. In the case of methane storage, PCN-14 with anthracene-derived ligand achieves breakthrough storage capacity, at a level 28% higher than the U.S. Department of Energy target. Selective gas adsorption requires a pore size comparable to that of the target gas molecules; therefore, we use bulky ligands and network interpenetration to reduce the pore size. In addition, with the help of an amphiphilic ligand, we were able to use temperature to continuously change pore size in a 2D layer MOF. Adding charge to an organic ligand can also stabilize frameworks. By ionizing the amine group within mesoMOF-1, the resulting electronic repulsion keeps the network from collapsing, giving rise to the first case of mesoporous MOF that demonstrates the type IV isotherm. We use dendritic hexacarboxylate ligands to synthesize an isoreticular series of MOFs with (3,24)-connected network topology. The cuboctahedral cages serve as building blocks that narrow the opening of the mesocavities into microwindows and stabilize these MOFs. The resulting materials have exceptionally high surface areas and hydrogen uptake capacities. Despite the many achievements in MOF development, there is still ample opportunity for further exploration. We will be continuing our efforts and look forward to contributing to this blossoming field in the next decade.     

sp2-碳共价有机框架材料的研究进展

共价有机框架材料是一类晶态高分子材料,通过定向的拓扑聚合将有机结构单元聚合为高度有序和延伸的二维或者三维框架材料.近5年来,合成化学的进展很大程度上促进了共价有机框架材料的结构设计与合成,实现了完全共轭的具有大π体系的sp2-碳共价有机框架材料的构筑.主要介绍了近年来通过不同的设计原则和合成策略来构筑基于sp2-碳共价...     

A computational study of water in UiO-66 Zr-MOFs: Diffusion,hydrogen bonding network,and confinement effect

For chemical warfare agent removal, the humidity emerges as an unavoidable challenge that significantly affects the performance of metal–organic frameworks. In this work, via density functional theory calculations, ab initio molecular dynamics and classical molecular dynamics simulations, we investigate the structural and diffusion properties of water in the pristine defect-free UiO-66, one Zr-based metal–organic framework. Through the detailed analyses of the distribution probability of water in two different cages of UiO-66, the binding interaction between water and UiO-66, the hydrogen bonding networks and resulted localized water clusters, we gain a fundamental understanding of structural and dynamics properties as well as the concentration dependence of water in UiO-66. We anticipate those theoretical results could provide insight to the competitive adsorption of water and chemical warfare agents, which eventually shows the utmost importance for the design and development of the next generation porous materials with appropriate water properties in real-life applications.     

Bilayer and 3-D open framework: Pillared metal-organic frameworks based on zinc and cadmic (6,3)-layers

The (6,3)-layers of transition metals and 3,5-pyridinecarboxylate (3,5-PDC) containing terminal coordinated molecules offer a great potential for obtained porous frameworks via the “pillaring” approach. In this work, we have successfully obtained two porous frameworks based on the zinc and cadmic (6,3)-layers (compounds 1 and 2, respectively) pillared by 4,4′-pyridine (bipy). Interestingly, different metal centers of Zn(II) and Cd(II) in the (6,3)-layers lead to the pillared frameworks into bilayers with {6³}{6⁶} topology (compound 3) and 3-D open framework with {6³}{6⁹·8} hms topology (compound 4), respectively. It is believed that this work deserves further focus to enrich the design strategy of novel porous crystalline metal-organic frameworks (MOFs).     

Tube Formation in Nanoscale Materials

The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb₂O₅ nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities.     

Design, chirality, and flexibility in nanoporous molecule-based materials

Scientific and technological interest in porous materials with molecule-sized channels and cavities has led to an intense search for controlled chemical routes to systems with specific properties. This Account details our work on directing the assembly of open-framework structures based on molecules and investigating how the response of nanoporous examples of such materials to guests differs from classical rigid porous systems. The stabilization of chiral nanoporosity by a hierarchy of interactions that both direct and maintain a helical open-framework structure exemplifies the approach.     

纳米结构多孔固体在二氧化碳吸附分离中的应用

二氧化碳（CO2）的双重角色（温室气体及一碳化工原料）使其吸附分离研究具有重要学术及社会经济意义。本文以多孔吸附材料为主线,系统评述了多孔炭、分子筛、有机金属骨架类材料及多孔聚合物等的CO2吸附分离最新研究进展。这些吸附材料的特点：多孔炭的微观及宏观形貌可控,孔结构可调,稳定性好;分子筛的具有丰富的微孔,孔径分布集中;有机金属骨架及多孔聚合物的种类多样,代表一类新兴的CO2吸附材料。分析了多孔固体应用于CO2吸附分离所涉及的关键科学问题,即高效吸附材料立体设计及影响选择性和吸附量等重要参数。提出澄清微孔/介孔/大孔比例以及表面基团种类和数量对CO2吸附贡献的定量关系的必要性,对材料的定向合成与优化有重要指导意义。     

高效分离乙烷/乙烯的烷烃选择性吸附剂研究进展

乙烯是石油化学工业的基础原材料,聚合级乙烯工业纯化的关键挑战是去除其中的乙烷杂质,这一步骤难度大、能耗高。近年来,以乙烷选择性吸附剂为核心的吸附分离纯化技术快速发展,并得到学术界和工业界的关注。该技术可在温和工况下高选择性分离出乙烯中的乙烷杂质,显现出巨大潜力。本文总结了近年来乙烷选择性吸附剂（特别是乙烷选择性MOFs）的研究进展,并归纳阐释其选择性吸附机理。同时,在前人研究成果的基础上,总结可行的乙烷选择性吸附剂的设计策略,指出当前开发高效乙烷选择性吸附剂面临的挑战和未来的研究方向。     

多级孔COFs材料的设计、合成及应用

共价有机框架（covalent organic frameworks,COFs）是一类通过共价键连接有机构筑单元设计组装而成的具有周期性二维（2D）或三维（3D）网状结构的多孔有机聚合物,具有高比表面积、低密度、高度有序的周期性结构和易于功能化等特点。与单一孔COFs相比,多级孔COFs具有分级的孔道结构、不同的孔环境、极易接近的活性位、优异的传质和扩散性能,在气体分离和储存、环境治理、光电、生物医药、催化等领域具有更为广阔的应用前景。但由于多级孔COFs合成条件苛刻,其结构多样性仍然十分有限。本文从反应类型、设计策略、合成方法、功能化修饰、应用领域等方面系统地综述了多级孔COFs的研究进展,提出开发更多的单体、键合类型、拓扑结构,拓展更多的修饰手段,充分发挥多级孔结构优势的发展趋势。未来通过不断探索与研究,一定能开发出更多具有新的拓扑结构、不断提高的性能及更多新的应用的多级孔COFs材料,实现多级孔COFs快速、高效、低成本的加工成型,使其在能源、生物、环境、催化等领域发挥出不可替代的作用。     

高效分离乙烷/乙烯的烷烃选择性吸附剂研究进展

乙烯是石油化学工业的基础原材料,聚合级乙烯工业纯化的关键挑战是去除其中的乙烷杂质,这一步骤难度大、能耗高。近年来,以乙烷选择性吸附剂为核心的吸附分离纯化技术快速发展,并得到学术界和工业界的关注。该技术可在温和工况下高选择性分离出乙烯中的乙烷杂质,显现出巨大潜力。本文总结了近年来乙烷选择性吸附剂（特别是乙烷选择性MOFs）的研究进展,并归纳阐释其选择性吸附机理。同时,在前人研究成果的基础上,总结可行的乙烷选择性吸附剂的设计策略,指出当前开发高效乙烷选择性吸附剂面临的挑战和未来的研究方向。     

水分子在多孔炭材料上的吸附行为研究进展

多孔炭材料具有较大的比表面积和发达的孔隙结构,是吸附有毒有害气体的关键材料,备受环境、化工、军事化学等领域的关注。多孔炭材料对有毒有害气体的吸附性能受气氛中水分子竞争吸附的影响,研究多孔炭材料对水分子的吸附行为是复杂环境下吸附分离有毒有害气体的基础,对改进多孔炭材料的表面官能团组成和孔结构具有重要的指导意义。基于此,本文综述了国内外关于水分子在多孔炭材料上吸附的机理、过程和影响因素,探讨了水分子作为示踪分子用于多孔炭材料结构表征的潜在可能,并对未来吸附理论的研究方向和指导新型吸附材料设计的应用前景进行展望。     

Ordered macroporous bimetallic nanostructures: design, characterization, and applications

Ordered porous metal nanomaterials have current and future potential applications, for example, as catalysts, as photonic crystals, as sensors, as porous electrodes, as substrates for surface-enhanced Raman scattering (SERS), in separation technology, and in other emerging nanotechnologies. Methods for creating such materials are commonly characterized as "templating", a technique that involves first the creation of a sacrificial template with a specific porous structure, followed by the filling of these pores with desired metal materials and finally the removal of the starting template, leaving behind a metal replica of the original template. From the viewpoint of practical applications, ordered metal nanostructures with hierarchical porosity, namely, macropores in combination with micropores or mesopores, are of particular interest because macropores allow large guest molecules to access and an efficient mass transport through the porous structures is enabled while the micropores or mesopores enhance the selectivity and the surface area of the metal nanostructures. For this objective, colloidal crystals (or artificial opals) consisting of three-dimensional (3D) long-range ordered arrays of silica or polymer microspheres are ideal starting templates. However, with respect to the colloidal crystal templating strategies for production of ordered porous metal nanostructures, there are two challenging questions for materials scientists: (1) how to uniformly and controllably fill the interstitial space of the colloidal crystal templates and (2) how to generate ordered composite metal nanostructures with hierarchical porosity. This Account reports on recent work in the development and applications of ordered macroporous bimetallic nanostructures in our laboratories. A series of strategies have been explored to address the challenges in colloidal crystal template techniques. By rationally tailoring experimental parameters, we could readily and selectively design different types of ordered bimetallic nanostructures with hierarchical porosity by using a general template technique. The applications of the resulting nanostructures in catalysis and as substrates for SERS are described. Taking the ordered porous Au/Pt nanostructures as examples for applications as catalysts, the experimental results show that both the ordered hollow Au/Pt nanostructure and the ordered macroporous Au/Pt nanostructure exhibit high catalytic ability due to their special structural characteristics, and their catalytic activity is component-dependent. As for SERS applications, primary experimental results show that these ordered macroporous Au/Ag nanostructured films are highly desirable for detection of DNA bases by the SERS technique in terms of a high Raman intensity enhancement, good stability, and reproducibility, suggesting that these nanostructures may find applications in the rapid detection of DNA and DNA fragments.     

Postsynthetic Covalent Modification in Covalent Organic Frameworks

The modification of covalent organic frameworks (COFs) based on postsynthetic covalent linkages is discussed in this review. In this strategy, the COF is preparedas scaffold and then assembled with functional groups with preservation of structural skeleton. Recent studies indicate that a number of COFs, such as COF-5 and 3D-OH-COOF, are controllable to postsynthetic modification. Furthermore, covalentmodifications including triazole, ester, amide, sulfide, o-carbamate, ether, and oxime are suitable for postsynthetic functionalization. The rapid development of postsynthetic modification demonstrates that this approach will provide a general platform to create COFs as robust functional porous materials for wide applications.     

多孔炭材料设计合成及电化学储能应用

多孔炭材料具有导电性好、结构稳定、资源丰富、价格低廉的天然优势，既可直接作为电极材料，构建炭基电化学储能器件，又可与非炭电活性材料复合，起到传输电子、缓冲体积膨胀及调节界面反应的作用，在电化学储能器件中一直发挥着不可或缺的作用。结合本文作者课题组的研究工作，本文总结了多孔炭制备及孔结构和形貌的调控方法，分析了各方法的优缺点；并以超级电容器、锂离子/钠离子电池和锂硫电池为代表，阐述了多孔炭材料在电化学储能领域的作用及应用研究现状，讨论了电化学储能器件对多孔炭材料的结构与性能要求，指出了多孔炭在电化学储能应用中存在的局限性，并对多孔炭在这些储能领域的研究和发展趋势做出展望。