Aksu Gokhan Onder, Daglar Hilal, Altintas Cigdem, Keskin Seda
Department of Chemical and Biological Engineering, Koc University, Rumelifeneri Yolu, Sariyer, 34450 Istanbul, Turkey.
J Phys Chem C Nanomater Interfaces. 2020 Oct 15;124(41):22577-22590. doi: 10.1021/acs.jpcc.0c07062. Epub 2020 Sep 18.
Covalent organic frameworks (COFs) have high potential in gas separation technologies because of their porous structures, large surface areas, and good stabilities. The number of synthesized COFs already reached several hundreds, but only a handful of materials were tested as adsorbents and/or membranes. We used a high-throughput computational screening approach to uncover adsorption-based and membrane-based CO/H separation potentials of 288 COFs, representing the highest number of experimentally synthesized COFs studied to date for precombustion CO capture. Grand canonical Monte Carlo (GCMC) simulations were performed to assess CO/H mixture separation performances of COFs for five different cyclic adsorption processes: pressure swing adsorption, vacuum swing adsorption, temperature swing adsorption (TSA), pressure-temperature swing adsorption (PTSA), and vacuum-temperature swing adsorption (VTSA). The results showed that many COFs outperform traditional zeolites in terms of CO selectivities and working capacities and PTSA is the best process leading to the highest adsorbent performance scores. Combining GCMC and molecular dynamics (MD) simulations, CO and H permeabilities and selectivities of COF membranes were calculated. The majority of COF membranes surpass Robeson's upper bound because of their higher H permeabilities compared to polymers, indicating that the usage of COFs has enormous potential to replace current materials in membrane-based H/CO separation processes. Performance analysis based on the structural properties showed that COFs with narrow pores [the largest cavity diameter (LCD) < 15 Å] and low porosities (ϕ < 0.75) are the top adsorbents for selective separation of CO from H, whereas materials with large pores (LCD > 20 Å) and high porosities (ϕ > 0.85) are generally the best COF membranes for selective separation of H from CO. These results will help to speed up the engineering of new COFs with desired structural properties to achieve high-performance CO/H separations.
共价有机框架（COF）因其多孔结构、大表面积和良好的稳定性，在气体分离技术中具有很高的潜力。已合成的COF数量已达数百种，但只有少数材料被测试用作吸附剂和/或膜。我们采用高通量计算筛选方法，揭示了288种COF基于吸附和基于膜的CO/H分离潜力，这是迄今为止研究用于燃烧前CO捕集的实验合成COF的最大数量。进行了巨正则蒙特卡罗（GCMC）模拟，以评估COF在五种不同循环吸附过程中对CO/H混合物的分离性能：变压吸附、变真空吸附、变温吸附（TSA）、变压变温吸附（PTSA）和变真空变温吸附（VTSA）。结果表明，许多COF在CO选择性和工作容量方面优于传统沸石，PTSA是导致吸附剂性能得分最高的最佳过程。结合GCMC和分子动力学（MD）模拟，计算了COF膜的CO和H渗透率及选择性。大多数COF膜由于其H渗透率高于聚合物而超过了罗布森上限，这表明在基于膜的H/CO分离过程中使用COF有巨大潜力取代现有材料。基于结构性质的性能分析表明，孔径窄[最大空腔直径（LCD）<15 Å]且孔隙率低（ϕ<0.75）的COF是从H中选择性分离CO的最佳吸附剂，而孔径大（LCD>20 Å）且孔隙率高（ϕ>0.85）的材料通常是从CO中选择性分离H的最佳COF膜。这些结果将有助于加速具有所需结构性质的新型COF的工程设计，以实现高性能的CO/H分离。
