共价有机框架材料在多相催化领域的研究进展（英文）

共价有机框架(COFs)材料是近年来在拓扑学基础上发展起来的一类新型有机多孔聚合物,是有机单体通过可逆共价键连接而形成的晶型多孔材料,具有拓扑结构"可设计"、比表面积大、结构规整、孔道均一、孔径可调节以及易于修饰和功能化等优点.与金属有机框架材料(MOFs)相比,由于COFs是以共价键连接形成空间网络结构,具有较好的热稳定性和化学稳定性,又被称为"有机分子筛".COFs的构筑单体为有机小分子,有机小分子来源广泛而且种类繁多,使得构筑单体多样化,便于通过构筑单体来调控目标材料的结构和功能.自2005年首次报道以来,COFs以其独特的结构和优越的性能,吸引了广大科研工作者的极大兴趣,对其结构设计、可控合成、结构解析以及功能探索成为了研究热点,在气体吸附与分离、光电材料等领域展现出了广阔的应用前景.特别是在催化领域,由于COFs材料的多孔性、敞开的孔道结构、良好的稳定性以及易于修饰的特点,采用COFs作为催化剂以及催化剂载体受到了人们普遍的关注.作为催化剂,COFs可分为本征型催化剂和负载型催化剂.本征型催化剂的设计方法是基于"自下而上"策略将催化活性中心嵌入材料骨架之中;负载型催化剂的设计方法是以COFs为载体,通过后修饰方式负载金属颗粒或离子来构建多相催化剂.本征型COFs催化剂是在分子水平上引入催化活性中心,具有活性位点均匀分散、数量可控的特点,而且COFs规整均一的孔道结构有利于底物的传质,也为择形催化提供了可能;负载型催化剂通过后修饰方式引入催化活性中心,由于COFs以共价键连接,催化剂稳定性较高.COFs载体具有较大的比表面积,使得催化活性位点分散性好,也有利于底物与催化活性位点的结合.本文综述了COFs作为多相催化剂在催化领域的发展状况,按照COFs引入催化活性位点的类别,如单催化位点、双催化位点以及负载的金属纳米粒子进行了细致的阐述,重点讨论了COFs催化剂的设计理念、制备方式、功能化策略、材料的稳定性、催化活性以及选择性等内容.此外,对COFs作为光催化剂以及电催化剂方面的研究也进行了详细的介绍.最后,我们讨论了COFs在未来催化领域所面临的问题及挑战,并展望了COFs在超分子催化以及酶催化等方面的应用前景.     

手性共价有机框架材料的研究进展与应用

共价有机框架材料(covalent organic frameworks, COFs)是一类是由各种有机小分子单体通过共价键有序连接而成的有机多孔材料.手性是一种在自然界中普遍存在的现象,手性化合物在医学、药学、农业等方面有重要应用.近几年,手性COFs引起了广大科研工作者的注意.手性COFs由于具有永久多孔、隧道型孔道、结构可预测、结构稳定、可循环利用等特点,在手性催化、手性分离等领域具有广泛的潜在应用.合成手性COFs材料的一种方案是通过各种不同的手性构筑单元直接连接而成,所以通过设计不同结构的手性构筑单元和合成具有功能性基团的手性单体可以得到结构多样的手性COFs材料.手性COFs材料的另一种合成方案是利用后修饰的方法将金属粒子或者有机小分子修饰到手性COFs骨架上从而对结构进行功能性调控.     

三维共价有机框架的后合成修饰

三维共价有机框架(3D COFs)是一种由有机构筑基元通过共价键连接而成的三维网状晶态有机多孔材料,具有高比表面积、复杂孔道结构和大量开放功能位点,在气体吸附与分离及催化等领域展现出了独特的应用前景.由功能基团构筑3D COFs可赋予其特征的性质及功能,然而普遍采用的直接构筑法可能存在合成困难、功能基团不兼容及结构解析...     

共价有机框架材料催化研究进展

共价有机框架材料（COFs）是一类具有高比表面积、高孔隙率、高结晶度的结构多样性多孔材料.由于COFs具有可设计性、易功能化的特点，可通过“自上而下”或者后修饰策略将具有催化活性的官能团或金属颗粒嵌入到材料骨架当中，从而设计出高效催化剂.COFs已逐渐在多相催化及其它催化领域展现出非常大的应用价值.本文综述了COFs作为催化剂载体在多种催化反应中的合成策略与应用，对COFs催化剂的现状进行了总结与展望，同时指出该领域面临的问题与挑战.     

共价有机框架材料的离子化改性及其催化合成环碳酸酯的性能研究（英文）

共价有机框架(COFs)材料是继金属-有机框架材料之后,在拓扑学基础上发展起来的又一类多孔材料.这类材料是由轻质元素(C,H,O,N,B,Si等)通过可逆共价键连接而成的结晶性有机多孔聚合物,具有比表面积大、骨架密度低、孔道结构规整、可人为设计以及表面易修饰改性等特点,自2005年首次报道以来就引起了人们的广泛关注.经过十多年的发展,COFs材料已经被广泛用于气体吸附/分离、光电、能量存储、非均相催化等研究领域.由于材料的多孔性以及相对稳定的特点,近年来COFs材料作为催化剂或催化剂载体用于多相催化反应已经成为该领域的一个研究热点.但是到目前为止,COFs材料的离子化改性用于异相催化相关研究还相对较少.本文选择二维骨架中含有羟基基团的H2P-DHPhCOF作为载体,通过两步接枝反应成功地将咪唑型离子液体引入到COF材料的孔道中;采用红外光谱、核磁共振、粉末X射线衍射、热失重分析等方法详细地表征了COF材料在后修饰过程中的变化.研究发现,1,4-二溴丁烷与N-甲基咪唑基团的引入占据了部分孔道,导致框架材料的孔径和孔容减小.同时,我们还将该改性后的离子型COF材料在DMSO/盐酸溶液中消解,利用核磁共振波谱计算了离子化程度.实验结果表明,N-甲基咪唑的接枝率约为4.9wt%.在既定的反应条件下,将该离子化的COF材料作为多相催化剂用于CO2和环氧化合物之间的环加成反应.以环氧氯丙烷作为测试底物,发现该离子型催化剂的催化性能与H2P-DHPhCOF相比有大副度提高,转化率达到了91%(120°C,24 h,CO2压力位1.0 MPa).在相同的条件下,该催化剂还对其他的环氧化合物具有一定的催化效果,其中环氧丙烷的转化率高达95%,且目标产物碳酸丙烯酯的选择性为100%.然而,对于大分子的环氧化合物,转化率和产率均较低,表明催化剂具有明显的尺寸选择性.此外,我们还以环氧氯丙烷的环加成反应为例考察了催化剂的循环稳定性,经过连续的5次循环,催化剂的催化活性得到了有效保持.我们的研究表明COF材料作为异相催化剂用于多相催化具有潜在的应用前景.而且,由于离子型多孔材料具有可交换的性质,我们可以通过将不同功能的反离子交换到孔道中,从而得到具有不同功能特性的多孔材料.因此,离子化共价有机框架材料是一类集多孔、高比表面积、可人为设计等性质于一体的新型多孔材料,有望应用于更加广泛的研究领域.     

基于有机硼酸的共价键有机框架研究进展

共价键有机框架(Covalent Organic Frameworks,COFs)是具有明确孔径分布的多孔晶体材料,在气体贮藏、催化、分离、光学器件和化学传感等方面均有应用前景。有机硼酸中硼原子最外层空的p轨道能与π键产生特殊的轨道作用,也可与路易斯碱发生配位作用。上述特点使其能够作为结构和功能导向的基元而用于构筑共价键有机框架。本文从合成、结构以及性质等方面对有机硼酸构筑的共价键有机框架进行了介绍。     

共价有机框架新应用: 选择性水解二维共价有机框架制备有机纳米管

共价有机框架(covalent organic frameworks,COFs)是一类晶态有机多孔聚合物,它们通过多官能团有机单体分子缩聚形成共价键连接的二维或三维拓展网格结构[1].遵循“框架化学”构筑原理[2],COFs的结构可被预先设计并精确构筑.这类新颖材料的显著特点是其内部分布高度有序的纳米孔道且孔道形状和大小可通过改变聚合单体的对称性和尺寸进行精确调节.此外,从构效关系的角度考虑,多孔和共轭结构特征[3]使其在物质吸附、储存与分离、催化、光电和传感检测等领域均得到了引人注目的应用[4].尽管如此,开辟COFs新应用的需求仍然十分迫切.     

有机多孔催化研究进展

有机多孔材料POPs (Porous Organic Polymers)成为近年来的研究前沿之一. 有机多孔材料包括非晶型(如CMP, HCP, PIM等)和晶型(比如COFs等)有机多孔材料两类, 它们具有优异的孔性质、较大的比表面积、稳定性好、重量轻以及易于功能化等诸多优点, 被广泛应用于气体存储分离、传感、有机光电和多相催化等重要领域. 这里对有机多孔材料在多相催化领域中的应用做一综述. 目前, 有机多孔催化领域的研究工作主要有三类: 一类是通过“自下而上”策略将金属-配体类催化剂嵌入有机多孔骨架来构建多相催化剂; 另一类是将有机多孔材料作为载体, 通过后修饰方式负载金属纳米颗粒构建多相催化剂; 最后一类是通过“自下而上”策略将不含金属的有机小分子催化剂嵌入材料骨架来构建多孔有机催化剂. 受益于其结构的优越性, 有机多孔材料在多相催化中表现出优异的催化性能. 借鉴于均相催化的发展, 具有催化活性的有机多孔材料在多相催化领域中的应用也将会有更大的发展空间.     

共价有机骨架材料设计及其在分离领域的应用

共价有机骨架(COFs)材料是由有机小分子单体通过共价键连接形成的结晶多孔聚合物。与传统的线性聚合物不同的是,COFs可以在二维和三维空间上对其骨架结构进行控制,从而合成具有高度有序的刚性多孔结构,并且能够调节骨架的化学和物理性质。这种由COF形成的纳米级孔道和空间为分子存储、释放和分离提供了理想的环境。因此它在能量储存、分离、催化等领域有着广泛的应用前景。本文综述了近年来COFs材料的研究进展,主要包括材料的合成策略及其在分离领域的应用,并对COFs材料未来的发展方向进行了展望。     

亚胺类共价有机骨架材料在样品前处理中的应用

亚胺类共价有机骨架(I-COFs)是有机单体根据席夫碱(Schiff-base)反应原理缩合形成的一类新型多孔晶体有机材料.I-COFs具有骨架密度低、比表面积大、孔隙率高、单体种类丰富、孔径尺寸可控、结构可功能化、合成方法多样和物化稳定性好等优点.近年来,I-COFs已成为材料科学领域的研究前沿,并广泛用于气体吸附、...     

Postsynthetic Functionalization of Three‐Dimensional Covalent Organic Frameworks for Selective Extraction of Lanthanide Ions

Chemical functionalization of covalent organic frameworks (COFs) is critical for tuning their properties and broadening their potential applications. However, the introduction of functional groups, especially to three‐dimensional (3D) COFs, still remains largely unexplored. Reported here is a general strategy for generating a 3D carboxy‐functionalized COF through postsynthetic modification of a hydroxy‐functionalized COF, and for the first time exploration of the 3D carboxy‐functionalized COF in the selective extraction of lanthanide ions. The obtained COF shows high crystallinity, good chemical stability, and large specific surface area. Furthermore, the carboxy‐functionalized COF displays high metal loading capacities together with excellent adsorption selectivity for Nd³⁺ over Sr²⁺ and Fe³⁺ as confirmed by the Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. This study not only provides a strategy for versatile functionalization of 3D COFs, but also opens a way to their use in environmentally related applications.     

Stable 2D Heteroporous Covalent Organic Frameworks for Efficient Ionic Conduction

Two‐dimensional (2D) covalent organic frameworks (COFs) feature open and ordered one‐dimensional column nanochannels which offer immense possibilities for incorporation of various guests for specific functions. However, the relatively low chemical stability of most COFs originating from the dynamic covalent linkages hinders their practical application. In this work, a highly crystalline and heteroporous dibenzo[g,p]chrysene‐based COF (DBC‐2P) was synthesized and served as a host material for ionic conduction. DBC‐2P exhibits excellent stability both in strong acid and base due to the large conjugated DBC‐based knot that reinforces the interlayer interactions. Subsequent encapsulation of linear polyethylene glycol (PEG) and PEG‐LiBF₄ salt into the nanochannels of DBC‐2P affords a hybrid material with a high ionic conductivity of 2.31×10^?3 S cm^?1. This work demonstrates an efficient post‐synthetic strategy for the development of new COF–polymer composites with intriguing properties.     

Adsorption Properties of Hydrated Cr3+ Ions on Schiff‐base Covalent Organic Frameworks: A DFT Study

Considering the superior physiochemical property, increasing efforts have been devoted to exploiting the covalent organic frameworks (COFs) materials on the environmental remediation of heavy metal ions. Water pollution caused by Cr³⁺ metal ions is of special concern for scientists and engineers. Notwithstanding all the former efforts made, it is surprising that very little is known about the interaction mechanisms between the hydrated Cr³⁺ metal ions and COF materials. In present context, density functional theory (DFT) method is used to elucidate geometric and electronic properties with the purpose of putting into theoretical perspective the application values and interaction mechanisms for COF materials on Cr³⁺ capture. The results showed that all the five selected Schiff‐base COFs materials displayed good adsorption performance on Cr³⁺ removal while the phenazine‐linked and imine‐COFs possessed the most favorable adsorption capacity due to the optimal chemical units and frameworks. The hydration effect was found to play a two‐side role in the adsorption process and interaction mechanisms, involving coordination, hydrogen bonds, as well as weak non‐covalent interactions, have been illuminated to explain the observed different adsorption behaviors. This study provides a general guidance for the design and selection of efficient COF materials as high‐capacity Cr³⁺ adsorbents.     

sp2 carbon-conjugated covalent organic frameworks for efficient photocatalytic degradation and visualized pH detection

The design and fabrication of versatile covalent organic frameworks (COFs) with multiple properties for diverse applications is highly desirable. Here, the difunctional COFs material g–C₁₈N₃–COF was prepared and modified to be applied for efficient photocatalytic degradation of Rhodamine B (RhB) and pH detection, respectively. Owing to the triazine unit which was suitable for photocatalyst construction, g–C₁₈N₃–COF was sensitive to visible light and exhibited excellent photocatalysis capability toward RhB. Specially, the photocatalytic degradation of RhB with a high concentration of 300 ppm using g–C₁₈N₃–COF reached equilibrium within 6 h. Moreover, g–C₁₈N₃–COF was further grown in-situ onto the filter paper to generate a novel composite material g–C₁₈N₃–COF@Paper with bright yellow fluorescence. g–C₁₈N₃–COF@Paper could visualize the pH detection by remarkable changes in its fluorescent intensity and color in the range of pH value from 1 to 5, on account of the protonation of the nitrogen atoms from the triazine ring in g–C₁₈N₃–COF. The triazine-based sp² carbon-conjugated g–C₁₈N₃–COF, respectively, used as photocatalyst and sensor in this work offers a new strategy to construct the versatile COFs material, facilitating the application of functional COFs in the environmental protection field.     

Nanoparticle Size-Fractionation through Self-Standing Porous Covalent Organic Framework Films

Covalent organic frameworks (COFs) have attracted attention due to their ordered pores leading to important industrial applications like storage and separation. Combined with their modular synthesis and pore engineering, COFs could become ideal candidates for nanoseparations. However, the fabrication of these microcrystalline powders as continuous, crack-free, robust films remains a challenge. Herein, we report a simple, slow annealing strategy to construct centimeter-scale COF films ( Tp-Azo and Tp-TTA ) with micrometer thickness. The as-synthesized films are porous (SA_BET=2033 m² g⁻¹ for Tp-Azo ) and chemically stable. These COFs have distinct size cut-offs (ca. 2.7 and ca. 1.6 nm for Tp-Azo and Tp-TTA , respectively), which allow the size-selective separation of gold nanoparticles. Unlike, other conventional membranes, the durable structure of the COF films allow for excellent recyclability (up to 4 consecutive cycles) and easy recovery of the gold nanoparticles from the solution.     

Vinylene‐Linked Covalent Organic Frameworks by Base‐Catalyzed Aldol Condensation

Two 2D covalent organic frameworks (COFs) linked by vinylene (?CH=CH?) groups (V‐COF‐1 and V‐COF‐2) are synthesized by exploiting the electron deficient nature of the aromatic s‐triazine unit of C₃‐symmetric 2,4,6‐trimethyl‐s‐triazine (TMT). The acidic terminal methyl hydrogens of TMT can easily be abstracted by a base, resulting in a stabilized carbanion, which further undergoes aldol condensation with multitopic aryl aldehydes to be reticulated into extended crystalline frameworks (V‐COFs). Both V‐COF‐1 (with terepthalaldehyde (TA)) and V‐COF‐2 (with 1,3,5‐tris(p‐formylphenyl)benzene (TFPB)) are polycrystalline and exhibit permanent porosity and BET surface areas of 1341 m² g^?1 and 627 m² g^?1, respectively. Owing to the close proximity (3.52 Å) of the pre‐organized vinylene linkages within adjacent 2D layers stacked in eclipsed fashion, [2+2] photo‐cycloadditon in V‐COF‐1 formed covalent crosslinks between the COF layers.     

Pore Geometry and Surface Engineering of Covalent Organic Frameworks for Anhydrous Proton Conduction

Developing new materials for anhydrous proton conduction under high-temperature conditions is significant and challenging. Herein, we create a series of highly crystalline covalent organic frameworks (COFs) via a pore engineering approach. We simultaneously engineer the pore geometry (generating concave dodecagonal nanopores) and pore surface (installing multiple functional groups such as −C=N−, −OH, −N=N− and −CF₃) to improve the utilization efficiency and host–guest interaction of proton carriers, hence benefiting the enhancement of anhydrous proton conduction. Upon loading with H₃PO₄, COFs can realize a proton conductivity of 2.33×10⁻² S cm⁻¹ under anhydrous conditions, among the highest values of all COF materials. These materials demonstrate good stability and maintain high proton conductivity over a wide temperature range (80–160 °C). This work paves a new way for designing COFs for anhydrous proton conduction applications, which shows great potential as high-temperature proton exchange membranes.     

Docking Site Modulation of Isostructural Covalent Organic Frameworks for CO2 Fixation

Three isostructural covalent organic frameworks (COFs) with either methoxyl, hydroxyl, or both groups on the channel wall, are synthesized and served as metal-free heterogeneous catalysts for chemical fixation of CO₂. Among them, the COF decorated with both hydroxyl and methoxyl groups named OMe-OH-TPBP-COF exhibits the highest catalytic activity and efficiency for CO₂ cycloaddition under mild conditions.     

3D Microporous Base‐Functionalized Covalent Organic Frameworks for Size‐Selective Catalysis

The design and synthesis of 3D covalent organic frameworks (COFs) have been considered a challenge, and the demonstrated applications of 3D COFs have so far been limited to gas adsorption. Herein we describe the design and synthesis of two new 3D microporous base‐functionalized COFs, termed BF‐COF‐1 and BF‐COF‐2, by the use of a tetrahedral alkyl amine, 1,3,5,7‐tetraaminoadamantane (TAA), combined with 1,3,5‐triformylbenzene (TFB) or triformylphloroglucinol (TFP). As catalysts, both BF‐COFs showed remarkable conversion (96 % for BF‐COF‐1 and 98 % for BF‐COF‐2), high size selectivity, and good recyclability in base‐catalyzed Knoevenagel condensation reactions. This study suggests that porous functionalized 3D COFs could be a promising new class of shape‐selective catalysts.