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。     

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.     

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.     

Hydrogen storage on Li-doped single-walled carbon nanotubes: Computer simulation using the density functional theory

The first principal calculation based on the density functional theory was performed to investigate the hydrogen storage behavior of Li-doped single-walled carbon nanotubes (SWCNTs). It was found that, through Li-doping, two new adsorption sites for hydrogen molecules are created in addition to the inherent three adsorptive sites which are exterior, interior and interstitial regions of pristine SWCNTs: the first site (denoted ‘region 1’) is the nanotube's sidewall whose electronic distribution status is influenced by the doped Li atoms. The second site (denoted ‘region 2’) exists on the positively charged Li atoms which result from the transfer of electrons from the Li atoms to the SWCNTs. The calculations show that although the adsorption energy in region 1 increases somewhat, the adsorption behavior of hydrogen is marginally different from that of pristine SWCNTs. However, in region 2, at least three hydrogen molecules can be adsorbed by each charged Li-atom, and based on the maximum Langmuir coverage (of 0.55), 1.1 hydrogen molecules can be adsorbed onto each charged Li-atom. When this result is considered together with the effective specific surface area, the hydrogen storage capacities of Li-doped SWCNTs with the doping ratio of LiC₁₅ are approximately 0.1 wt% in region 1 and 1.17 wt% in region 2 at 10 MPa and 300 K so that the total H₂ storage capability is 1.27 wt%, which agrees well with previously reported results.     

新型金属-有机骨架配位聚合物（MOF）的研究龈

金属有机骨架配位聚合物结构多样,性质独特,具有广泛的应用前景,它已成为近几年来一个热门的研究领域,如今它因H2存储方面的潜力受到广泛关注。本文简要介绍该类配位聚合物作为一种新型的多孔材料,在结构和性能方面的研究进展。     

金属有机框架材料的绿色合成

金属有机框架化合物（Metal-organic frameworks,简称MOFs）是由金属离子（或簇）与有机配体配位并经由自组装而形成的一类多孔材料^[1]。MOFs具有极其发达的孔道结构,比表面积和孔容远超其他多孔材料。有机/无机杂化这一特点也赋予了MOFs其他材料（例如沸石、活性炭等）所不具备的无限结构功能可调性^[2]。此外,MOFs具有移除客体分子而主体框架完好保持的持久孔道或孔穴,这使得MOFs具有超乎寻常的化学及物理稳定性。正是基于以上这些特点,MOFs在许多领域有着丰富的应用^[3-4],例如催化^[5]、H₂储存^[6]、CO₂捕集^[7]、药物运输^[8]、污染物吸附^[9]、生物医学成像^[10]等方面。MOFs的商业化探索成为了目前的热点。MOFs的很多应用都与可持续发展及“绿色材料”有关,但MOFs本身的合成过程也需要考虑可持续性和环境影响。金属有机化学所面临的环境挑战是独特的,因为它将金属离子、有机配体的危害联系在一起,且合成过程大多需要大量能耗。主要介绍了金属有机框架材料的绿色可持续合成,主要分为4个方面：1）使用更安全或生物相容性的配体;2）使用更绿色、低成本的金属源;3）绿色溶剂的开发;4）无溶剂合成法。     

有机液体载体储氢催化剂的研究

介绍了6种常用的储氢方法:加压压缩储氢技术、液化储氢技术、储氢合金储氢、碳质材料储氢、金属有机骨架储氢、有机液态氢化物可逆储放氢技术等,并对诸项技术的优点以及存在的问题进行了评述。重点介绍了有机液态氢化物可逆储放氢技术的原理和特点,综述了国内外研究现状并提出了使用廉价的液体储氢原料和提高催化剂活性、稳定性的新思路。     

计算化学在多孔储氢材料研究中的应用

计算化学方法在多孔储氢材料的应用主要有4个方面:1)研究多孔材料的储氢性能;2)研究多孔材料对氢气的吸附热;3)研究储氢机理;4)设计新型多孔储氢材料。综述了计算化学方法在多孔储氢材料研究中取得的成果和最新进展,展望了计算化学方法在储氢领域的应用前景。     

Solid‐state Materials and Methods for Hydrogen Storage: A Critical Review

Hydrogen is important as a new source of energy for automotive applications. It is clear that the key challenge in developing this technology is hydrogen storage. Current methods for hydrogen storage have yet to meet all the demands for on‐board applications. High‐pressure gas storage or liquefaction cannot fulfill the storage criteria required for on‐board storage. Solid‐state materials have shown potential advantages for hydrogen storage in comparison to other storage methods. In this article, the most popular solid‐state storage materials and methods including carbon based materials, metal hydrides, metal organic frameworks, hollow glass microspheres, capillary arrays, clathrate hydrates, metal nitrides and imides, doped polymer and zeolites, are critically reviewed. The survey shows that most of the materials available with high storage capacity have disadvantages associated with slow kinetics and those materials with fast kinetics have issues with low storage capacity. Most of the chemisorption‐based materials are very expensive and in some cases, the hydrogen absorption/desorption phenomena is irreversible. Furthermore, a very high temperature is required to release the adsorbed hydrogen. On the other hand, the main drawback in the case of physisorption‐based materials and methods is their lower capacity for hydrogen storage, especially under mild operating conditions. To accomplish the requisite goals, extensive research studies are still required to optimize the critical parameters of such systems, including the safety (to be improved), security (to be available for all), cost (to be lowered), storage capacity (to be increased), and the sorption‐desorption kinetics (to be improved).     

多孔吸附储氢材料研究进展

综述了氢存储研究的重要性和国内外多孔吸附储氢材料的研究工作,对碳基多孔材料、纳米管材料、多孔矿物材料和金属有机物多孔材料在锗氢中的研究热点和存在问题进行了详细介绍,并对未来多孔吸附储氢材料的研究工作进行了展望。     

Simulation on hydrogen storage properties of metal‐organic frameworks Cu‐BTC at 77–298 K

In recent years, many researchers have studied on the hydrogen storage properties of metal‐organic frameworks (MOFs) by grand canonical Monte Carlo (GCMC) simulation. At present, the GCMC studies of Cu‐BTC (BTC: benzene‐1,3,5‐tricarboxylate) which is a prototypical metal‐organic framework mainly adopt the classical force fields, the simulation temperatures are mainly focus on 298 and 77 K, and most researchers did not consider the effects of quantum effects at low temperature. Therefore, we used the quantum effects to correct the classical force fields and the force fields with more accurate simulation results were used to simulate the hydrogen adsorption performances of Cu‐BTC in the temperature range of 77–298 K and the pressure range of 1–8 MPa at each temperature. The results show that the effects of quantum effects on the hydrogen storage of Cu‐BTC cannot be neglected and the corrected Dreiding force field can simulate hydrogen adsorption performances of Cu‐BTC more accurately at low temperature. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1383–1388, 2018     

有机液体储氢材料的研究进展

氢气是一种清洁、高效的能量,被视为最具发展潜力的清洁能源,其存储和运输是影响氢能大规模应用的关键问题。常用的储氢方法有高压气态储氢、液化储氢、金属合金储氢和有机液体氢化物储氢等,本文综述了其中受到广泛关注的有机液体储氢材料,分析了多种有机液体储氢材料的储氢原理与特点,认为有机液体储氢容量大,可循环使用,更加高效安全。主要介绍了环己烷、甲基环己烷、十氢萘、咔唑和乙基咔唑等,重点对目前的国内外研究现状进行了阐述。根据分析结果,对其发展前景进行了展望,指出如果利用工业上能够大规模获取的化学原料,如萘系多环芳烃,开发高效低成本加氢脱氢催化剂,研究最适宜的加氢与脱氢条件,可大幅降低储氢成本,有利于氢能的大规模应用与发展。     

Synthesis of three-dimensional hierarchically porous reduced graphene oxide–TiO2 nanocomposite for enhanced hydrogen storage

Three-dimensional hierarchically porous graphene-TiO₂ (3D-HPGT) nanocomposites were synthesized through electrostatic assembly method. The obtained 3D-HPGT nanocomposites exhibited hierarchically porous structure with multi-level pores (macro-, meso- and micropores), high specific surface area (705?m²/g), large pore volume (0.41?cm³/g) and higher hydrogen storage capacity. At the pressure of 5?bar, 3D-HPGT nanocomposite showed a maximum hydrogen capacity of 4.11 and 1.48?wt% at 77 and 298?K, respectively, which were much higher than those of previously reported graphene-based materials. The enhanced hydrogen storage capacities were attributed to the three-dimensional hierarchically porous structure, evenly distributed TiO₂ nanoparticles on the graphene nanosheets, strong attachment of TiO₂ nanoparticles to the underlying graphene nanosheets, and hydrogen spillover effect originated from TiO₂ nanoparticles.     

Hydrogen adsorption in different carbon nanostructures

Hydrogen adsorption in different carbonaceous materials with optimized structure was investigated at room temperature and 77 K. Activated carbon, amorphous carbon nanotubes, SWCNTs and porous carbon samples all show the same adsorption properties. The fast kinetics and complete reversibility of the process indicate that the interaction between hydrogen molecules and the carbon nanostructure is due to physisorption. At 77 K the adsorption isotherm of all samples can be explained with the Langmuir model, while at room temperature the storage capacity is a linear function of the pressure. The surface area and pore size of the carbon materials were characterized by N₂ adsorption at 77 K and correlated to their hydrogen storage capacity. A linear relation between hydrogen uptake and specific surface area (SSA) is obtained for all samples independent of the nature of the carbon material. The best material with a SSA of 2560 m²/g shows a storage capacity of 4.5 wt% at 77 K.     

H2 sorption in HCl-treated polyaniline and polypyrrole

Hydrogen sorption in conducting polymers was investigated in order to determine their potential as hydrogen storage media. The conducting polymers, polyaniline and polypyrrole, were treated with an acid, which resulted in an exceptionally high hydrogen sorption, 6 and 8 wt% at room temperature and under 9.3 MPa. Both the molecular effect and electrical effects by the conducting polymers appear to play an important role in hydrogen sorption. This paper presents the preliminary results of hydrogen sorption in a conducting polymer along with its characterization by XRD, scanning electron microscopy, TGA, and conductivity measurement using a four-probe method. A possible mechanism for the extraordinarily high hydrogen storage is suggested.     

Application of Danckwerts-type boundary conditions to the modeling of the thermal behavior of metal hydride reactors

The paper presents a model-based investigation of a metal hydride reactor applied as a solid state hydrogen storage device. The elements of a metal hydride reactor are hydrogen supply duct, internal hydrogen distribution, hydride bed, reactor shell and the flow domain of the heat transfer fluid. Internal hydrogen distribution and hydride bed are porous media. Therefore, hydrogen flows through non-porous and porous regions during its reversible exothermic absorption and endothermic desorption, respectively. The interface between porous and non-porous regions is a discontinuity with respect to energy transport mechanisms. Hence, Danckwerts-type boundary conditions for the energy balance equation are introduced. Application of the first and second law of thermodynamics to the interface reveals that temperature jumps may occur at the hydrogen inlet but are not allowed at the hydrogen outlet. Exemplarily the loading behavior of a metal hydride storage tank based on sodium alanate is analyzed. It is demonstrated and experimentally validated that only Danckwerts-type boundary conditions predict the important cooling effect of the inlet hydrogen on the exothermic absorption process correctly.     

金属有机框架光催化剂微环境调控研究进展

金属有机框架材料（MOFs）是一类无机金属中心和有机配体自组装形成的晶体多孔材料,既有无机材料高结晶度、高电子迁移率等特点,又兼具有机材料高比表面积、高孔隙率、强可修饰性等特点,在光催化领域显示出广阔的应用前景。围绕物理化学微环境调控,对近年来MOFs光催化材料的研究进行了详细综述。其中,物理微环境的调控重点介绍了微观形貌调控、贵金属沉积和异质结构建三个方面;化学微环境调控重点介绍了金属位点调控与有机配体调控两个方面。此外,对MOFs光催化材料的未来发展进行展望,以期为高性能MOFs光催化剂的理性设计和可控制备等方面的研究提供思路。     

新型储氢材料研究进展

氢能作为一种环保可再生的新型能源,生产技术逐渐走向成熟,成本大幅度下降,将迎来快速发展的机遇期。氢能被广泛利用的关键在于是否能够实现高效储存。本文重点讨论了四类新型储氢材料,即金属络合氢化物储氢材料、碳纳米管储氢材料、沸石以及新型沸石类材料、有机液态储氢材料。文章指出：金属络合氢化物储氢材料储存压力低但循环稳定性差;碳纳米管储氢材料已经有很长的发展历史,安全性高且易脱氢,然而目前对其储氢机理认识不够成熟;沸石以及新型沸石类材料价格低廉,但是对反应条件的要求高;有机液态储氢材料被认为是大规模储存和运输的可行选择,然而昂贵的成本和苛刻的反应条件限制了其发展。文章指出后续需要改进并开发具有较高存储容量和具有经济价值的储氢材料。     

Multi-scale theoretical investigation of hydrogen storage in covalent organic frameworks

The quest for efficient hydrogen storage materials has been the limiting step towards the commercialization of hydrogen as an energy carrier and has attracted a lot of attention from the scientific community. Sophisticated multi-scale theoretical techniques have been considered as a valuable tool for the prediction of materials storage properties. Such techniques have also been used for the investigation of hydrogen storage in a novel category of porous materials known as Covalent Organic Frameworks (COFs). These framework materials are consisted of light elements and are characterized by exceptional physicochemical properties such as large surface areas and pore volumes. Combinations of ab initio, Molecular Dynamics (MD) and Grand Canonical Monte-Carlo (GCMC) calculations have been performed to investigate the hydrogen adsorption in these ultra-light materials. The purpose of the present review is to summarize the theoretical hydrogen storage studies that have been published after the discovery of COFs. Experimental and theoretical studies have proven that COFs have comparable or better hydrogen storage abilities than other competitive materials such as MOF. The key factors that can lead to the improvement of the hydrogen storage properties of COFs are highlighted, accompanied with some recently presented theoretical multi-scale studies concerning these factors.