Synthesis of Luminescent Covalent–Organic Polymers for Detecting Nitroaromatic Explosives and Small Organic Molecules

Three porous luminescent covalent‐‐organic polymers (COPs) have been synthesized through self‐polycondensation of the monomers of tris(4‐bromophenyl)amine, 1,3,5‐tris(4‐bromophenyl)benzene, and 2,4,6‐tris‐(4‐bromo‐phenyl)‐[1,3,5]triazine by using Ni‐catalyzed Yamamoto reaction. All the COP materials possess not only high Brunauer–Emmett–Teller (BET) specific surface area of about 2000 m² g⁻¹, high hydrothermal stability, but also graphene‐like layer texture. Interestingly, COP‐3 and COP‐4 show very fast responses and high sensitivity to the nitroaromatic explosives, and also high selectivity for tracing picric acid (PA) and 2,4,6‐trinitrotoluene (TNT) at low concentration (<1 ppm). In short, the COPs may be a new kind of material for detecting explosives and small organic molecules.     

A Pyrolysis‐Free Covalent Organic Polymer for Oxygen Reduction

Highly efficient electrocatalysts derived from metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) for oxygen reduction reaction (ORR) have been developed. However, the subsequent pyrolysis is often needed owing to their poor intrinsic electrical conductivity, leading to undesirable structure changes and destruction of the original fine structure. Now, hybrid electrocatalysts were formed by self‐assembling pristine covalent organic polymer (COP) with reduced graphene oxide (rGO). The electrical conductivity of the hybridized COP/rGO materials is increased by more than seven orders of magnitude (from 3.06×10^?9 to 2.56×10^?1 S m^?1) compared with pure COPs. The ORR activities of the hybrid are enhanced significantly by the synergetic effect between highly active COP and highly conductive rGO. This COP/rGO hybrid catalyst exhibited a remarkable positive half‐wave (150 mV).     

Metal–Organic Organopolymeric Hybrid Framework by Reversible [2+2] Cycloaddition Reaction

Organic polymers are usually amorphous or possess very low crystallinity. The metal complexes of organic polymeric ligands are also difficult to crystallize by traditional methods because of their poor solubilities and their 3D structures can not be determined by single‐crystal X‐ray crystallography owing to a lack of single crystals. Herein, we report the crystal structure of a 1D Zn^II coordination polymer fused with an organic polymer ligand made in situ by a [2+2] cycloaddition reaction of a six‐fold interpenetrated metal–organic framework. It is also shown that this organic polymer ligand can be depolymerized in a single‐crystal‐to‐single‐crystal (SCSC) fashion by heating. This strategy could potentially be extended to make a range of monocrystalline metal organopolymeric complexes and metal–organic organopolymeric hybrid materials. Such monocrystalline metal complexes of organic polymers have hitherto been inaccessible for materials researchers.     

Synthesis of Unsymmetric Bipyridine–PtII–Alkynyl Complexes through Post‐Click Reaction with Emission Enhancement Characteristics and Their Applications as Phosphorescent Organic Light‐Emitting Diodes

Two unsymmetric bipyridine–platinum(II)–alkynyl complexes have been synthesised by a post‐click reaction. These metal complexes are found to exhibit emission enhancement properties. The photoluminescence quantum yield can be significantly increased from 0.03 in solution to 0.72 in solid‐state thin films. Efficient solution‐processable organic light‐emitting diodes have been fabricated by utilizing these complexes as phosphorescent dopants. A high external quantum efficiency of up to 5.8 % has been achieved.     

Construction of Covalent‐Organic Frameworks (COFs) from Amorphous Covalent Organic Polymers via Linkage Replacement

Covalent‐organic frameworks (COFs) as porous crystalline materials show promising potential applications. However, developing facile strategies for the construction of COFs directly from amorphous covalent organic polymers (COPs) is still a great challenge. To this end, we report a novel approach for easy preparation of COFs from amorphous COPs through the linkage replacement under different types of reactions. Four COFs with high crystallinity and porosity were constructed via the linkage substitution of polyimide‐linked COPs to imine‐linked COFs as well as imine‐linked COPs to polyimide‐linked COFs. The realization of the linkage substitution would significantly expand the research scope of COFs.     

A Novel Strategy for the Construction of Covalent Organic Frameworks from Nonporous Covalent Organic Polymers

The field of covalent organic frameworks (COFs) has been developed significantly in the past decade on account of their important characteristics and vast application potential. On the other hand, the discovery of novel synthetic methodology is still a challenging task to further promote the preparation of COFs. Herein, an interesting protocol for the conversion of amorphous nonporous covalent organic polymers (COPs) to COFs was established, affording four COFs with high crystallinity and porosity. Specifically, imine‐linked amorphous COP‐1 was successfully converted to COF‐1–4 by replacing one type of linker with other organic building blocks. The realization of this conversion provides a facile method for constructing COFs from COPs.     

Chemistry in Confinement: Copper and Palladium Catalyzed Ecofriendly Organic Transformations within Porous Frameworks

A concise account on the use of transition metals copper (Cu) and palladium (Pd), as their cations as well as nanoparticles exchanged/immobilized onto porous frameworks such as zeolites, metal organic frameworks (MOFs), covalent organic polymers (COPs) and hollow nanostructures, functioning as catalysts in organic synthesis is presented. This biomimetic account, “focusing on catalytic systems in confinement” within zero‐dimensional microenvironments and second sphere coordination covers primarily results from our group on N‐sulfonylketenimine mediated cycloaddition, hydrogenation and C−C bond forming reactions, thus providing an interesting insight into the versatility and utility of these Cu and Pd catalysts. Other significant advantages and green credentials of confinement such as stability, selectivity, reusability, promotion of multicomponent reactions, use of green solvents, atom economy, and use of ambient conditions are highlighted at appropriate places. In the final section, our views on the current achievements and the future prospects in this area are summarized.     

用于食品安全分析样品前处理的共价有机聚合物的制备及应用进展

食品安全关系身体健康和生命安全,是全球关注的热点之一。食品基质复杂,痕量有毒有害物质分析之前必须经过有效的前处理。目前发展的前处理技术如固相萃取、磁固相萃取、固相微萃取等,其关键是吸附介质。共价有机聚合物是一类通过共价键连接而成的有机多孔材料,具有质轻、稳定性好、比表面积大、结构可控、易于修饰等特性,是一类优异的新型吸附材料。该文综述了近年来共价有机聚合物(COPs)在食品安全分析前处理中的应用进展。共价有机聚合物及其功能化复合材料通过简单的装填、聚合反应或化学键合固定到小柱或毛细管柱中用作固相萃取的吸附介质;通过一锅法、原位还原法、原位生长法或共沉淀法生成具有磁性的固相萃取吸附介质;或者通过物理涂覆、化学键合、溶胶凝胶法及原位生长法制备固相微萃取纤维。基于以上高吸附容量共价有机聚合物的样品前处理技术,食品中农残兽残、添加剂、环境污染物及生物毒素等得到了有效富集。最后,展望了COPs在食品分析样品前处理应用中的发展方向:简单高效绿色制备方法的开发,功能化COPs的设计合成;萃取机理的研究;高通量、高灵敏度分析方法研究。这些研究将促进COPs在样品前处理领域获得更广泛的应用。     

卟啉框架材料在光催化领域的应用

卟啉分子对可见光具有较强吸收能力,被广泛应用于光催化和光敏化材料的设计开发。 基于卟啉单元设计构筑框架结构材料,可以借助框架结构的大比表面积和可调控孔结构,实现对卟啉单元光物理化学性质的修饰和调控,达到提高材料光催化量子产率和光催化选择性的目的。 本文综述了卟啉基金属有机框架材料(MOFs)、卟啉基共价有机框架材料(COFs)、以及卟啉基多孔共价有机聚合物(COPs)在光催化领域的研究进展,通过归纳需要解决的关键问题,对卟啉框架材料的未来发展进行了展望。     

Volatile Organic Compound Sensing by Quartz Crystal Microbalances Coated with Nanostructured Macromolecular Metal Complexes

We report the construction of a molecular recognition layer composed of polyelectrolyte brushes and metal complexes on the surface of a quartz crystal microbalance (QCM) and the sensing abilities for various volatile organic compounds (VOCs). Atom‐transfer radical polymerization of 2‐(dimethylamino)ethyl acrylate from an initiator‐terminated self‐assembled monolayer yielded polyelectrolyte brushes on the surface of a weight‐detectable quartz crystal microbalance. One end of a poly[(2‐dimethylamino)ethyl methacrylate] brush was covalently attached onto the surface of a sensor. We found that metallophthalocyanines with four bulky pentaphenylbenzene substituents could adsorb volatile organic compounds selectively into their cavities. Macromolecular metal complexes were prepared by immersing polymer‐brush‐modified QCMs into an aqueous solution of sterically protected cobalt phthalocyanine. Anionic cobalt phthalocyanine was trapped in the polymer brushes and acted as a molecular receptor for the sensing of VOC molecules.     

Flexible,Luminescent Metal–Organic Frameworks Showing Synergistic Solid‐Solution Effects on Porosity and Sensitivity

Mixing molecular building blocks in the solid solution manner is a valuable strategy to obtain structures and properties in between the isostructural parent metal–organic frameworks (MOFs). We report nonlinear/synergistic solid‐solution effects using highly related yet non‐isostructural, phosphorescent Cu^I triazolate frameworks as parent phases. Near the phase boundaries associated with conformational diversity and ligand heterogeneity, the porosity (+150 %) and optical O₂ sensitivity (410 times, limit of detection 0.07 ppm) can be drastically improved from the best‐performing parent MOFs and even exceeds the records hold by precious‐metal complexes (3 ppm) and C₇₀ (0.2 ppm).     

The First One‐Pot Synthesis of Metal–Organic Frameworks Functionalised with Two Transition‐Metal Complexes

The synthesis of a metal–organic framework (UiO‐67) functionalised simultaneously with two different transition metal complexes (Ir and Pd or Rh) through a one‐pot procedure is reported for the first time. This has been achieved by an iterative modification of the synthesis parameters combined with characterisation of the resulting materials using different techniques, including X‐ray absorption spectroscopy (XAS). The method also allows the first synthesis of UiO‐67 with a very wide range of loadings (from 4 to 43 mol %) of an iridium complex ([IrCp*(bpydc)(Cl)Cl]^2?; bpydc=2,2′‐bipyridine‐5,5′‐dicarboxylate, Cp*=pentamethylcyclopentadienyl) through a pre‐functionalisation methodology.     

Pyrene‐cored covalent organic polymers by thiophene‐based isomers,their gas adsorption,and photophysical properties

Two new pyrene‐cored covalent organic polymers (COPs), CK‐COP‐1 and CK‐COP‐2 , were synthesized via the one‐step polymerization of two thiophene‐based isomers, 1,3,6,8‐tetra(thiophene‐2‐yl) pyrene ( L₁ ) and 1,3,6,8‐tetra(thiophene‐3‐yl) pyrene ( L₂ ). The resulting pyrene‐cored COPs exhibit rather different surface areas of 54 m² g^?1 and 615 m²g^?1 for CK‐COP‐1 and CK‐COP‐2 , respectively. The CO₂ uptake capacities of CK‐COP‐1 and CK‐COP‐2 also show different values of 2.85 and 9.73 wt % at 273 K, respectively. Furthermore, CK‐COP‐2 offers not only a larger CO₂ adsorption capacity but also a better CO₂/CH₄ selectivity at 273 K compared with CK‐COP‐1 . CK‐COP‐1 and CK‐COP‐2 also exhibit considerable differences in their photophysical property. The different structure and properties of CK‐COPs could be attributed to the isomer effect of their corresponding thiophene‐based monomers. © 2017 Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2383–2389     

Metal–Organic Coordination Strategy for Obtaining Metal-Decorated Mo-Based Complexes: Multi-dimensional Structural Evolution and High-Rate Lithium-Ion Battery Applications

Multi-dimensional metal oxides have attracted great attention in diverse applications due to their intriguing performances. However, their structural design remains challenging, particularly that based on organic chelation chemistry. Although metal–organic complexes with different architectures have been reported, their structure formation mechanisms are not well understood because of the complex chelation processes. Herein, we introduce a new metal–organic coordination strategy to construct metal-decorated (Ni, Co, Mn) Mo-based complexes ranging from 2D nanopetals to 3D microflowers. The chelating process of the metal–organic complex can be tuned by a surfactant, giving rise to different structures, and then a further metal can be appended. Thus, different metal (oxide)-decorated MoO₂/C-N structures were designed, enabling an extremely high lithium storage capability of 1018 mA h g⁻¹ and rate capacities of up to 10 A g⁻¹ over 1000 cycles. Relationships between electrochemical behavior and structure have been analyzed kinetically. A high-rate lithium-ion battery has been assembled from Ni-MoO₂/C-N and an Ni-rich layered oxide as the anode and cathode, respectively. We believe that this general metal–organic coordination strategy should be applicable to other multi-functional materials with superior capabilities.     

Composite Material that Comprised Metal–Organic Nanotubes and a Sponge as a High‐Performance Adsorbent for the Extraction of Pharmaceuticals and Personal Care Products from Environmental Water Samples

A composite material that comprised metal–organic nanotubes (MONTs) and a sponge, Cu?MONTs?sponge, was synthesized by using a rapid and convenient surfactant‐assisted dip‐coating method and used as a high‐performance adsorbent for the solid‐phase extraction of pharmaceuticals and personal care products (PPCP) from environmental water samples. By adjusting the surfactant concentration, a composite material that contained metal–organic nanotubes and a macroporous 3D porous sponge was constructed. This modified sponge achieved outstanding reproducibility as an adsorbent, with the adsorption of trace or ultratrace amounts of contaminants. Moreover, this composite material was conveniently recycled and its extraction efficiency only decreased by 6.3–12.1 % after 30 adsorption/desorption cycles. The resulting composite exhibited excellent adsorption capacity for PPCPs, which was attributed to its unique porous structure, natural hydrophobicity, and electrostatic interactions between the metal–organic nanotubes and analyte molecules. This Cu?MONTs?sponge material is an ideal adsorbent for the extraction of trace amounts of PPCPs from environmental water samples.     

Sophisticated Design of Covalent Organic Frameworks with Controllable Bimetallic Docking for a Cascade Reaction

Precise control of the number and position of the catalytic metal ions in heterogeneous catalysts remains a big challenge. Here we synthesized a series of two‐dimensional (2D) covalent organic frameworks (COFs) containing two different types of nitrogen ligands, namely imine and bipyridine, with controllable contents. For the first time, the selective coordination of the two nitrogen ligands of the 2D COFs to two different metal complexes, chloro(1,5‐cyclooctadiene)rhodium(I) (Rh(COD)Cl) and palladium(II) acetate (Pd(OAc)₂), has been realized using a programmed synthetic procedure. The bimetallically docked COFs showed excellent catalytic activity in a one‐pot addition–oxidation cascade reaction. The high surface area, controllable metal‐loading content, and predesigned active sites make them ideal candidates for their use as heterogeneous catalysts in a wide range of chemical reactions.     

Stabilizing Metal–Organic Polyhedra (MOP): Issues and Strategies

Metal–organic polyhedra (MOPs) are discrete, metal–organic molecular entities composed of edge‐sharing molecular polygons or connected molecular vertices. Unlike the infinite metal–organic coordination networks popularized by metal–organic frameworks (MOFs), spherical MOPs, also known as nanocages, nanospheres, nanocapsules, or nanoballs, are obtained through the self‐organization of metal–carboxylate or metal–pyridine/pyrimidine links to afford cage‐like nanoarchitectures. MOPs offer much promise as porous materials owing to their well‐defined structures and solution processability. However, these advantages become moot if their poor aqueous stability and/or guest‐removal‐induced aggregation handicaps remain unaddressed. The concise premise of this contribution limits our discussion to the design principles in action behind recent developments in stable carboxylate MOPs. To highlight the structure–property relationships between the structural and compositional features of these metal carboxylate polyhedra, related scientific challenges and state‐of‐the‐art research directions for further exploration are presented in brief.     

Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility

The construction of highly stable metal–porphyrinic frameworks (MPFs) is appealing as these materials offer great opportunities for applications in artificial light‐harvesting systems, gas storage, heterogeneous catalysis, etc. Herein, we report the synthesis of a novel mesoporous metal–porphyrinic framework (denoted as NUPF‐1) and its catalytic properties. NUPF‐1 is constructed from a new porphyrin linker and a Zr₆O₈ structural building unit, possessing an unprecedented doubly interpenetrating scu net. The structure exhibits not only remarkable chemical and thermal stabilities, but also a distinct structural flexibility, which is seldom seen in metal–organic framework (MOF) materials. By the merit of high chemical stability, NUPF‐1 could be easily post‐metallized with [Ru₃(CO)₁₂], and the resulting {NUPF‐1–RuCO} is catalytically active as a heterogeneous catalyst for intermolecular C(sp³)?H amination. Excellent yields and good recyclability for amination of small substrates with various organic azides have been achieved.     

Directing the Structural Features of N2‐Phobic Nanoporous Covalent Organic Polymers for CO2 Capture and Separation

A family of azo‐bridged covalent organic polymers (azo‐COPs) was synthesized through a catalyst‐free direct coupling of aromatic nitro and amine compounds under basic conditions. The azo‐COPs formed 3D nanoporous networks and exhibited surface areas up to 729.6 m² g^?1, with a CO₂‐uptake capacity as high as 2.55 mmol g^?1 at 273 K and 1 bar. Azo‐COPs showed remarkable CO₂/N₂ selectivities (95.6–165.2) at 298 K and 1 bar. Unlike any other porous material, CO₂/N₂ selectivities of azo‐COPs increase with rising temperature. It was found that azo‐COPs show less than expected affinity towards N₂ gas, thus making the framework “N₂‐phobic”, in relative terms. Our theoretical simulations indicate that the origin of this unusual behavior is associated with the larger entropic loss of N₂ gas molecules upon their interaction with azo‐groups. The effect of fused aromatic rings on the CO₂/N₂ selectivity in azo‐COPs is also demonstrated. Increasing the π‐surface area resulted in an increase in the CO₂‐philic nature of the framework, thus allowing us to reach a CO₂/N₂ selectivity value of 307.7 at 323 K and 1 bar, which is the highest value reported to date. Hence, it is possible to combine the concepts of “CO₂‐philicity” and “N₂‐phobicity” for efficient CO₂ capture and separation. Isosteric heats of CO₂ adsorption for azo‐COPs range from 24.8–32.1 kJ mol^?1 at ambient pressure. Azo‐COPs are stable up to 350 °C in air and boiling water for a week. A promising cis/trans isomerization of azo‐COPs for switchable porosity is also demonstrated, making way for a gated CO₂ uptake.     

A Mixed Molecular Building Block Strategy for the Design of Nested Polyhedron Metal–Organic Frameworks

A mixed molecular building block (MBB) strategy for the synthesis of double‐walled cage‐based porous metal–organic frameworks (MOFs) is presented. By means of this method, two isostructural porous MOFs built from unprecedented double‐walled metal–organic octahedron were obtained by introducing two size‐matching C₃‐symmetric molecular building blocks with different rigidities. With their unique framework structures, these MOFs provide, to the best of our knowledge, the first examples of double‐walled octahedron‐based MOFs.