Yoshimoto Yuta, Tomita Yuiko, Sato Kohei, Higashi Shiori, Yamato Masafumi, Takagi Shu, Kawakami Hiroyoshi, Kinefuchi Ikuya
Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo 192-0397, Japan.
Langmuir. 2022 Jun 21;38(24):7567-7579. doi: 10.1021/acs.langmuir.2c00661. Epub 2022 Jun 6.
We investigate the adsorption and diffusion behaviors of CO, CH, and N in interfacial systems composed of a polymer of intrinsic microporosity (PIM-1) and amorphous silica using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. We build model systems of mixed matrix membranes (MMMs) with PIM-1 chains sandwiched between silica surfaces. Gas adsorption analysis using GCMC simulations shows that gas molecules are preferentially adsorbed in microcavities distributed near silica surfaces, resulting in an increase in the solubility coefficients of CO, CH, and N compared to bulk PIM-1. In contrast, diffusion coefficients obtained from MD simulations and then calibrated using the dual-mode sorption model show different tendencies depending on gas species: CO diffusivity decreases in MMMs compared to PIM-1, whereas CH and N diffusivities increase. These differences are attributed to competing effects of silica surfaces: the emergence of larger pores as a result of chain packing disruption, which enhances gas diffusion, and a quadrupole-dipole interaction between gas molecules and silica surface hydroxyl groups, which retards gas diffusion. The former has a greater impact on CH and N diffusivities, whereas the latter has a greater impact on CO diffusivity due to the strong quadrupole-dipole interaction between CO and surface hydroxyls. These findings add to our understanding of gas adsorption and diffusion behaviors in the vicinity of PIM-1/silica interfaces, which are unobtainable in experimental studies.
我们使用巨正则蒙特卡罗（GCMC）和分子动力学（MD）模拟，研究了由固有微孔聚合物（PIM-1）和无定形二氧化硅组成的界面系统中CO、CH和N的吸附与扩散行为。我们构建了混合基质膜（MMM）的模型系统，其中PIM-1链夹在二氧化硅表面之间。使用GCMC模拟进行的气体吸附分析表明，气体分子优先吸附在二氧化硅表面附近分布的微腔中，与本体PIM-1相比，导致CO、CH和N的溶解度系数增加。相比之下，从MD模拟获得并随后使用双模吸附模型校准的扩散系数根据气体种类显示出不同的趋势：与PIM-1相比，MMM中CO的扩散率降低，而CH和N的扩散率增加。这些差异归因于二氧化硅表面的竞争效应：链堆积破坏导致出现更大的孔隙，这增强了气体扩散；以及气体分子与二氧化硅表面羟基之间的四极-偶极相互作用，这阻碍了气体扩散。前者对CH和N的扩散率影响更大，而后者由于CO与表面羟基之间强烈的四极-偶极相互作用，对CO的扩散率影响更大。这些发现增进了我们对PIM-1/二氧化硅界面附近气体吸附和扩散行为的理解，这在实验研究中是无法获得的。
