Authors: Shuai Li | Liang Qiao | Yan Cui | Kebin Chi
Source: Chinese Science Bulletin (Chinese Version) (article, 2024-07-01)
Field: Materials Science — Materials Chemistry

用于碳烃分离的共价有机框架 <p indent="0mm">The efficient separation and purification of hydrocarbon mixtures poses critical challenges in the petrochemical industry owing to their structural and physicochemical similarities. Traditional separation technologies, such as distillation and extraction, have long been used. However, these methods are increasingly viewed as unsustainable given their high energy consumption and substantial capital investment requirements. Consequently, adsorptive separation technology based on porous materials is being developed to meet the demands of creating an economical and sustainable petrochemical industry. Covalent organic frameworks (COFs) is a novel and highly promising class of porous materials that have garnered substantial attention owing to their structural flexibility and functional diversity and have distinct advantages over conventional materials such as zeolites and carbon-based adsorbents. The unique combination of periodic porosity, abundant surface chemistry, and high chemical stability of COFs enables them to achieve superior adsorption capacities and selectivities for hydrocarbon separation processes. This review begins by outlining the key attributes of COFs that are particularly advantageous for hydrocarbon separation, including the pore size, surface polarity, and stability. These features can be precisely engineered using strategies such as structural predesign and post-synthetic modifications. By carefully selecting and assembling monomers and functional groups, researchers can optimize the pore architecture and surface characteristics of COFs to enhance their separation efficiency. Furthermore, the stability of COFs can be significantly improved by constructing more robust covalent bonds or incorporating hydrogen bonds to further increase their practical utility in demanding industrial applications where durability is essential. In addition, the optimization of the delicate balance between periodicity, surface chemistry, and stability by precisely controlling the experimental parameters to maximize the separation performance is discussed. Next, the application of COFs in the separation of various hydrocarbon mixtures, including olefins/alkenes, alkenes/alkynes, hexane isomers, aromatics/cycloalkanes, and C<sub>8</sub> alkylaromatics, is comprehensively discussed. This review provides a detailed analysis of the adsorptive capacity and selectivity of COFs for each hydrocarbon system, elucidating the underlying separation mechanisms and molecular interactions that drive these processes. The key separation mechanisms, including the enhancement of molecular sieving effects through the downsizing of pores to the sub-nanometer range, are thoroughly examined. This enhancement is achieved through techniques such as pore partitioning, topological structure design, and interlayer stacking adjustments. The thermodynamic aspects of separation are enhanced by modulating the chemical environments within COFs, such as by incorporating metal or Lewis base sites, and strengthening host–guest interactions, including C–H···π, C–H···N, or π···π interactions. Additionally, this review highlights the unique gate-opening effect that arises from the intrinsic structural flexibility of COFs, emphasizing their potential for the stimuli-responsive capture of target molecules under varying conditions. The conclusion highlights the tunable pore structures, modular characteristics, and functional versatility of COFs that make them outstanding platforms for advancing hydrocarbon separation technologies. However, despite their potential, further technological advancements are necessary to fully realize their industrial applicability. Improvements in the high-quality synthesis, scaled-up production, and material shaping are required to bridge the gap between laboratory research and industrial implementation. Emerging technologies like <italic>in-situ</italic>/operando characterization techniques, artificial intelligence, and high-throughput experimentation can play a pivotal role in elucidating the structure-property relationships of COFs. These advances are expected to accelerate the development and application of COFs in the petrochemical industry, ultimately driving innovation, efficiency, and sustainability. Medicine Covalent Organic Framework Applications ; Catalysis and Hydrodesulfurization Studies ; Mesoporous Materials and Catalysis