A Three-dimensional Covalent Organic Framework for CO2 Uptake and Dyes Adsorption

Environmental pollution is one of the most severe problems facing today, including water pollution and the greenhouse effect. Therefore, developing materials with high-efficiency dyes adsorption and CO₂ uptake is significant. Covalent organic frameworks(COFs), as a burgeoning class of crystalline porous polymers, present a promising application potential in areas related to pollution regulation due to their exciting surface properties. Herein, we report a 3D COF with a high specific surface area(BET about 2072 m²/g) by utilizing tetrahedral and rectangle building blocks connected through[4+4] imine condensation reactions to synthesize. The obtained COF not only can separate dyes from water effectively but also shows a remarkable CO₂ uptake capacity. This research thus provides a promising material to remove dyes and adsorb CO₂ in environmental remediation.     

CO2 Capture by Hydroxylated Azine-Based Covalent Organic Frameworks

Covalent organic frameworks (COFs) RIO-13, RIO-12, RIO-11, and RIO-11m were investigated towards their CO₂ capture properties by thermogravimetric analysis at 1 atm and 40 °C. These microporous COFs bear in common the azine backbone composed of hydroxy-benzene moieties but differ in the relative number of hydroxyl groups present in each material. Thus, their sorption capacities were studied as a function of their textural and chemical properties. Their maximum CO₂ uptake values showed a strong correlation with an increasing specific surface area, but that property alone could not fully explain the CO₂ uptake data. Hence, the specific CO₂ uptake, combined with DFT calculations, indicated that the relative number of hydroxyl groups in the COF backbone acts as an adsorption threshold, as the hydroxyl groups were indeed identified as relevant adsorption sites in all the studied COFs. Additionally, the best performing COF was thoroughly investigated, experimentally and theoretically, for its CO₂ capture properties in a variety of CO₂ concentrations and temperatures, and showed excellent isothermal recyclability up to 3 cycles.     

Boron-doped Covalent Triazine Framework for Efficient CO2 Electroreduction

Converting CO₂ into chemicals with electricity generated by renewable energy is a promising way to achieve the goal of carbon neutrality. Carbon-based materials have the advantages of low cost, wide sources and environmental friendliness. In this work, we prepared a series of boron-doped covalent triazine frameworks and found that boron doping can significantly improve the CO selectivity up to 91.2% in the CO₂ electroreduction reactions(CO₂RR). The effect of different doping ratios on the activity by adjusting the proportion of doped atoms was systematically investigated. This work proves that the doping modification of non-metallic materials is a very effective way to improve their activity, and also lays a foundation for the study of other element doping in the coming future.     

Construction of a Three-dimensional Covalent Organic Framework via the Linker Exchange Strategy

Covalent organic framework(COF) is a porous crystalline material with a well-controlled structure and a wide range of potential applications. However, the construction of new COF faces huge challenges, including the design and synthesis of structural unit monomers, the choice of reaction solvent system, and the study of reaction time and temperature. So, it’s particularly important to widen the application scope of synthetic methods and further promote the development of COFs. Here, we performed structural transformations in a three-dimensional(3D) COF(COF-300), and Fourier transform infrared spectroscopy(FTIR), power X-ray diffraction analysis(PXRD) and nitrogen adsorption isotherms confirmed the chemical principles and the successful realization of these exchanges. At the same time, we found that the interpenetrating structure in 3D COF can be changed through the conversion of linkers. The structure simulation successfully proved the transformation of COF from five-fold to seven-fold interpenetration. In addition, in order to prove the versatility of this strategy, we used the same method to convert COF-300 into a high crystallinity 3D COF(TJNU-COF-302) that is also seven-fold interpenetrating and has not been reported. This simple strategy not only makes it easy to obtain a 3D COF connected with imines, which greatly promotes the development of COF, but also provides a new way to develop 3D COFs with complex interpenetrating structures.     

A Two-dimensional Dual-pore Covalent Organic Framework for Efficient Iodine Capture

Effectively capturing volatile radioiodine generated during the nuclear fission process is considered to be a safe way to the utilization of nuclear power. Here we report a new two-dimensional covalent organic framework(2D COF), ETTA-PyTTA-COF, as a highly efficient iodine adsorbent, which is constructed through the condensation reaction between 4,4’,4’’,4’’’-(ethene-1,1,2,2-tetrayl)-tetrabenzaldehyde(ETTA) and 1,3,6,8-tetrakis(4-aminophenyl)pyrene(PyTTA). The ETTA-PyTTA-COF possesses a permanent 1D channel porous structure with a high Brunauer-Emmet-Teller(BET) surface area of 1519 m²/g and excellent chemical and thermal stability. It shows ultrahigh iodine adsorption capability, which can reach up to 4.6 g/g in vapor owing to its high BET surface area, large π-conjugated structure and plenty of imine groups in the skeleton of the COF as effective iodine sorption sites.     

A Two-dimensional Covalent Organic Framework for Iodine Adsorption

Radioactive iodine is a notorious pollutant in gas radioactive nuclear waste due to its radiation hazard, volatility, chemical toxicity, and high mobility. Therefore, developing a material with high efficiency-specific iodine capture is significant. Covalent organic framework(COF) has attracted significant attention as a new crystalline porous organic material. Due to its large specific surface and high chemical stability, it is an excellent alternative to adsorbents. Herein, we report a chemically stable two-dimensional COF(termed JUC-609) with specific adsorption of iodine. Adsorption experiments show that JUC-609 has an excellent iodine adsorption capacity as high as 5.9 g/g under 353 K and normal pressure condition, and iodine adsorption after multiple cycles is still maintained. Our study thus promotes the potential application of COFs in the field of environment-related applications.     

Boosting CO2 Photoreduction via Regulating Charge Transfer Ability in a One-Dimensional Covalent Organic Framework

Two-dimensional (2D) imine-based covalent organic frameworks (COFs) hold potential for photocatalytic CO₂ reduction. However, high energy barrier of imine linkage impede the in-plane photoelectron transfer process, resulting in inadequate efficiency of CO₂ photoreduction. Herein, we present a dimensionality induced local electronic modulation strategy through the construction of one-dimensional (1D) pyrene-based covalent organic frameworks (PyTTA-COF). The dual-chain-like edge architectures of 1D PyTTA-COF enable the stabilization of aromatic backbones, thus reducing energy loss during exciton dissociation and thermal relaxation, which provides energetic photoelectron to traverse the energy barrier of imine linkages. As a result, the 1D PyTTA-COF exhibits significantly enhanced CO₂ photoreduction activity under visible-light irradiation when coordinated with metal cobalt ion, yielding a remarkable CO evolution of 1003 μmol g⁻¹ over an 8-hour period, which surpasses that of the corresponding 2D counterpart by a factor of 59. These findings present a valuable approach to address in-plane charge transfer limitations in imine-based COFs.     

Construction of Tetrathiafulvalene-based Covalent Organic Frameworks for Superior Iodine Capture

The effective capture of radioiodine species during nuclear fuel reprocessing and nuclear accidents is of primary importance but remains challenging for the sustainable development of nuclear energy. Herein, we report two newly designed two-dimensional(2D) and three-dimensional(3D) covalent organic frameworks by introducing tetrathiafulvalene functional groups into the building units for the simultaneous physisorption and chemisorption capture of iodine molecules. Remarkably, the obtained 3D TTF-TAPT-COF material exhibited a superior iodine vapor adsorption capacity of up to 5.02 g/g at 348 K and under ambient pressure and an adsorption kinetics of 0.515 g/(g∙h), surpassing most of other materials reported so far. The strong physiochemical interactions between iodine molecules and the frameworks of the obtained COFs were revealed by a set of experimental techniques. This study provides a feasible approach for the rational design and the construction of novel and effective COF-based adsorbents for iodine enrichment and related environmental remediation.     

A Triptycene-Based Porous Organic Polymer that Exhibited High Hydrogen and Carbon Dioxide Storage Capacities and Excellent CO2/N2 Selectivity

A novel porous organic polymer (POP) has been constructed through the condensation of triptycene tricatechol and 1,3,5‐benzenetris(4‐phenylboronic acid). This triptycene‐based POP exhibited high H₂ uptake (up to 1.84 wt% at 77 K, 1 bar), large CO₂ adsorption capacity (up to 18.1 wt% at 273K, 1 bar), and excellent CO₂/N₂ adsorption selectivity (up to 120/1). The influence of solvent on the gas adsorption performance of the POP has also been investigated.     

一种新型磺酸修饰的共价有机框架用于二氧化碳吸收和染料吸附

环境污染是地球现今的重要问题之一,而其中就包括水污染与温室效应.共价有机框架(covalent organic frame-works,COFs)作为一种新兴的晶态多孔聚合物,因其优异的吸附性能,在污染治理领域具有广阔的应用前景.本工作报道了一种基于β-酮胺单体通过迈克尔加成-消除反应合成的磺酸型微孔COF (JUC-...     

Mixed-metal Ionothermal Synthesis of Metallophthalocyanine Covalent Organic Frameworks for CO2 Capture and Conversion

Phthalocyanines (PCs) are intriguing building blocks owing to their stability, physicochemical and catalytic properties. Although PC-based polymers have been reported before, many suffer from relatively low stability, crystallinity, and low surface areas. Utilizing a mixed-metal salt ionothermal approach, we report the synthesis of a series of metallophthalocyanine-based covalent organic frameworks (COFs) starting from 1,2,4,5-tetracyanobenzene and 2,3,6,7-tetracyanoanthracene to form the corresponding COFs named M-pPPCs and M-anPPCs, respectively. The obtained COFs followed the Irving–Williams series in their metal contents, surface areas, and pore volume and featured excellent CO₂ uptake capacities up to 7.6 mmol g⁻¹ at 273 K, 1.1 bar. We also investigated the growth of the Co-pPPC and Co-anPPC on a highly conductive carbon nanofiber and demonstrated their high catalytic activity in the electrochemical CO₂ reduction, which showed Faradaic efficiencies towards CO up to 74 % at −0.64 V vs. RHE.     

具有高气态碘吸附的二维介孔共价有机框架

合成了一种新型的二维介孔共价有机框架(COF)材料JUC-573.粉末X射线衍射、氮气吸附-脱附和热重等表征结果表明合成的COF材料具有高结晶度、高比表面积以及良好的热稳定性.在333 K、常压条件下,该材料表现出优异的碘吸附能力,且吸附量高达4.15 g/g.这是由于在JUC-573中规则定向的垂直一维介孔孔道能够有效地避免碘吸附后的堵塞,从而优化了材料的吸附能力. JUC-573可多次循环用于气态碘的捕获且保持几乎不变的吸附量.     

Crystalline Anionic Germanate Covalent Organic Framework for High CO2 Selectivity and Fast Li Ion Conduction

The metalloid-centered covalent organic framework has attracted great interest from both its structure and application. Heavier elements have seldomly been incorporated in the covalent organic frameworks, even if they exhibit special structural features and properties. Herein, we reported the first crystalline germanate covalent organic framework with hexacoordinated germanate linked by an anthracene linker. The existence of counterion lithium ions in the framework provides a high CO₂ uptake of 88.5 cm³ g⁻¹ at 273 K and a high CO₂/N₂ selectivity of 101. A significantly improved lithium ion conductivity of 0.25 mS cm⁻¹ at room temperature was observed due to the soft germanium center.     

定向合成高效捕获CO2的新型多孔芳香材料

通过简单的离子热法,以四（4-氰基联苯基）硅烷作为四面体基块,将其与无水氯化锌在充满氩气气氛的手套箱中充分研磨后密封,分别以400和550 ℃的反应温度合成了新型多孔芳香骨架材料（PAF-51）,得到PAF-51-1（400 ℃条件下）与PAF-51-2（550 ℃条件下）的比表面积分别为720和557 m²·g^-1 （BET）.与CH₄和N₂对比,该材料对CO₂具有极好的选择性吸附能力. 273 K条件下,CO₂/N₂分离指数最高可达52.2,CO₂/CH₄分离指数也达到10.3,这一性质极有可能使得PAF-51成为捕获CO₂理想材料,并对再生能源具有潜在的应用.     

一种新型酰胺功能化的共价有机框架用于选择性染料吸附

共价有机框架(covalent organic framework, COF)是一种由轻质元素(C、H、O和N)以共价键的形式连接组成的结晶多孔聚合物,由于其具有规则的孔道、可修饰的骨架以及良好的稳定性而被广泛应用于不同的领域.尤其是将含氮的功能基团连接到COF的骨架中,可以为其吸附特定的染料提供丰富的活性位点.基于此,本工作成功制备了一种酰胺功能化的二维共价有机框架材料(JUC-578),通过一系列的表征证明了该材料具有高的结晶度、均一规整的形貌以及开放的一维介孔孔道.更重要的是,发现JUC-578可以选择性地吸附阳离子染料,并且可以多次循环利用.这主要归因于骨架中的氮作为电子给体与缺电子的染料之间的静电作用以及其他弱相互作用(氢键、偶联作用等).与此同时,JUC-578高的结晶度和有序的孔道也是实现可逆吸附染料非常重要的因素.     

Ag Nanoparticles Supported on a Resorcinol‐Phenylenediamine‐Based Covalent Organic Framework for Chemical Fixation of CO2

Covalent organic frameworks are a new class of crystalline organic polymers possessing a high surface area and ordered pores. Judicious selection of building blocks leads to strategic heteroatom inclusion into the COF structure. Owing to their high surface area, exceptional stability and molecular tunability, COFs are adopted for various potential applications. The heteroatoms lining in the pores of COF favor synergistic host–guest interaction to enhance a targeted property. In this report, we have synthesized a resorcinol‐phenylenediamine‐based COF which selectively adsorbs CO₂ into its micropores (12 Å). The heat of adsorption value (32 kJ mol^?1) obtained from the virial model at zero‐loading of CO₂ indicates its favorable interaction with the framework. Furthermore, we have anchored small‐sized Ag nanoparticles (≈4–5 nm) on the COF and used the composite for chemical fixation of CO₂ to alkylidene cyclic carbonates by reacting with propargyl alcohols under ambient conditions. Ag@COF catalyzes the reaction selectively with an excellent yield of 90 %. Recyclability of the catalyst has been demonstrated up to five consecutive cycles. The post‐catalysis characterizations reveal the integrity of the catalyst even after five reaction cycles. This study emphasizes the ability of COF for simultaneous adsorption and chemical fixation of CO₂ into corresponding cyclic carbonates.     

Selective CO2 Adsorption in a Supramolecular Organic Framework

Considering the rapidly rising CO₂ level, there is a constant need for versatile materials which can selectively adsorb CO₂ at low cost. The quest for efficient sorptive materials is still on since the practical applications of conventional porous materials possess certain limitations. In that context, we designed, synthesized, and characterized two novel supramolecular organic frameworks based on C‐pentylpyrogallol[4]arene (PgC₅) with spacer molecules, such as 4,4′‐bipyridine (bpy). Highly optimized and symmetric intermolecular hydrogen‐bonding interactions between the main building blocks and comparatively weak van der Waals interactions between solvent molecules and PgC₅ leads to the formation of robust extended frameworks, which withstand solvent evacuation from the crystal lattice. The evacuated framework shows excellent affinity for carbon dioxide over nitrogen and adsorbs ca. 3 wt % of CO₂ at ambient temperature and pressure.     

Synthesizing Interpenetrated Triazine-based Covalent Organic Frameworks from CO2

Crystalline triazine-based covalent organic frameworks (COFs) are aromatic nitrogen-rich porous materials. COFs typically show high thermal/chemical stability, and are promising for energy applications, but often require harsh synthesis conditions and suffer from low crystallinity. In this work, we propose an environmentally friendly route for the synthesis of crystalline COFs from CO₂ molecules as a precursor. The mass ratio of CO₂ conversion into COFs formula unit reaches 46.3 %. The synthesis consists of two steps; preparation of 1,4-piperazinedicarboxaldehyde from CO₂ and piperazine, and condensation of the dicarboxaldehyde and melamine to construct the framework. The CO₂-derived COF has a 3-fold interpenetrated structure of 2D layers determined by powder X-ray diffraction, high-resolution transmission electron microscopy, and select-area electron diffraction. The structure shows a high Brunauer–Emmett–Teller surface area of 945 m² g⁻¹ and high stability against strong acid (6 M HCl), base (6 M NaOH), and boiling water over 24 hours. Post-modification of the framework with oxone has been demonstrated to modulate hydrophilicity, and it exhibits proton conductivity of 2.5×10⁻² S cm⁻¹ at 85 °C, 95 % of relative humidity.