聚醚–聚醯胺嵌段共聚物／二硫化鉬混合基質薄膜於二氧化碳分離效能提升之分子模擬解析

近年來，二維材料已被廣泛的填充至高分子基質中製備高效能的混合基質膜。二硫化鉬因研究指出其對二氧化碳具有高親和力，被認為具有潛力製備出高滲透性和選擇性的二氧化碳分離薄膜。然而，由於二硫化鉬的複雜結構，要使用分子模擬技術來預估含二硫化鉬之混合基質薄膜的效能至今仍然是一個挑戰。因此，本研究的目的為提出可以合理模擬含二硫化鉬混合基質薄膜之方法，並同時預測其氣體分離效能。本研究透過修改商業軟體Materials Studio 2017 R2中PCFF的力場參數並結合約束方法以更適當地描述二硫化鉬奈米片結構。接著，運用前述方法建構了一系列含不同二硫化鉬添加量（0wt%至20wt%）之Pebax-1657／二硫化鉬混合基質薄膜模型，並透過分子動力學模擬與蒙地卡羅模擬技術，分別預測二氧化碳和氮氣在薄膜中的擴散係數和溶解係數，進而計算氣體分子滲透性以及解析薄膜之分離機制。結果顯示，溶解步驟主導了此複合薄膜的溶解擴散分離機制。於低二硫化鉬添加量的情況下，薄膜對二氧化碳之溶解度有顯著的提升，然而隨著二硫化鉬添加量高至20wt%，二氧化碳之溶解度的上升趨勢有漸緩的現象。隨著二硫化鉬添加量從0wt%增加至20wt%，二氧化碳的滲透率從32.05顯著提升至129.64 Barrer，同時維持對二氧化碳／氮氣之高滲透選擇性。因此，我們的結果顯示，在適當的二硫化鉬添加量情況下，二硫化鉬的摻入可以提高Pebax-1657薄膜的二氧化碳捕捉性能。本研究提供了一種方法來構建含二硫化鉬之混合基質膜模型並預測其校能，模擬結果可以幫助未來更有效地進行實驗設計，此模擬方法也可用於評估二硫化鉬與其他聚合物基質所形成的複合薄膜之表現。

關鍵字

分子動態力學；薄膜氣體分離；混合基質膜；二維材料

並列摘要

In recent years, two-dimensional materials have widely been used to replace traditional fillers in mix matrix membranes (MMMs). With high affinity for carbon dioxide (CO2), molybdenum disulfide (MoS2) provides great potential to produce MMMs with high permeability and sufficient selectivity in gas separation application. However, it is still a challenge to estimate the performance of using MoS2 as functional fillers in MMMs due to the complex structure. An aim of our study is to develop a methodology to appropriately simulate MoS2-contained MMMs system and also predict the separation performance. We modified the force field parameters in PCFF, which is built in commercial software Materials Studio 2017 R2, and applied the restraint method for a better description of MoS2 nanosheet structure. In this study, Pebax-1657 was chosen as the polymer matrix and a series of MMMs models with MoS2 loading ranging from 0wt% to 20wt% were constructed. By applying molecular dynamics (MD) and Monte Carlo (MC) simulations, we respectively determined the diffusivity and solubility coefficient of CO2 and N2 within the MMMs. Then, to investigate the influence of MoS2 loading on the performance, the permeability via the solution-diffusion mechanism for each gas as well as the ideal gas selectivity for binary gas mixtures were examined. The results reveal that the addition of MoS2 could significant increase the solubility of CO2 at low loading and the upward trend seems to level off with additional loading to 20wt%. Compared to the results of diffusivity, it was found that the solution step dominates the solution-diffusion process. By increasing the MoS2 loading from 0wt% to 20wt%, the permeability of CO2 significantly increased from 32.05 to 129.64 Barrer without sacrificing the permeability selectivity of CO2/N2. Therefore, our results indicate that, at appropriate MoS2 loading, the incorporation of MoS2 could enhance the CO2 capture performance of Pebax-1657 membrane. Our study provides a method to build representative MoS2-contained MMMs models and predict the performance. The results can help followers to efficiently conduct the experiment and design MMMs of other polymer bases as well.

並列關鍵字

Molecular Dynamics ； Membrane Gas Separation ； Mixed Matrix Membranes ； Two-dimensional Material

參考文獻

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聚醚–聚醯胺嵌段共聚物／二硫化鉬混合基質薄膜於二氧化碳分離效能提升之分子模擬解析

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