有機金屬框架/聚醯亞胺介面之分子動力學模擬氣體輸送行為;Molecular Dynamics Simulation of Gas Transport Behavior in Metal-Organic Framework/Polyimide Interface

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Title:	有機金屬框架/聚醯亞胺介面之分子動力學模擬氣體輸送行為;Molecular Dynamics Simulation of Gas Transport Behavior in Metal-Organic Framework/Polyimide Interface
Authors:	鄔子平;Wu, Tzu-Ping
Contributors:	化學工程與材料工程學系
Keywords:	分子動力學;聚醯亞胺;有機金屬框架;混合基材薄膜;molecular dynamics simulation;polyimide;metal-organic frameworks;mixed matrix membranes
Date:	2020-07-22
Issue Date:	2020-09-02 15:04:38 (UTC+8)
Publisher:	國立中央大學
Abstract:	由於近年來溫室效應嚴重影響環境，使對於二氧化碳及其他氣體分離純化及儲存有高度的關注。為了分離工業廢氣，薄膜常被作為眾多分離材料之一，其中混合基材薄膜(mixed matrix membranes, MMMs)為研究主要重點。然而，填料與高分子基材的交互作用相對複雜，常見問題如非選擇性孔洞產生、高分子包覆性及填料吸附能力等。透過分子動力學(molecular dynamics, MD)計算，我們建構不同重量百分比填料的混和基材薄膜，並且測試薄膜的氣體滲透能力。本研究使用聚醯亞胺(6FDA-DAM)為基材，並使用有機金屬框架(UiO-66) 為填料以建構混合系統模型。其中，密度泛函理論(Density functional theory, DFT)用於有機金屬框架結構優化計算，優化後的UiO-66 結構分別以四面體結構(tetrahedral cage)和八面體結構(octahedral cage)等二級建構單元(second building units)為填料進行探討；系統性分子動力學(31-steps)用於建構混合基材薄膜系統。本研究以蒙地卡羅法(Monte Carlo method, MC)及氣體分子動力學計算分別探討薄膜氣體溶解性(solubility)和擴散(diffusivity)，同時四面體結構及八面體結構吸附性影響也進行探討。最後，實驗結果發現隨著填料比例增加，氣體溶解性和擴散性有顯著增強效果。但相對受到高分子包覆、氣體極性和大小、框架種類吸附強度不同，造成排序呈現非線性關係。;In order to separate industrial waste gas, artificial membranes are utilized to provide a barrier. The greenhouse effect has affected the environment seriously, leading to increased attention on CO2 and other gas purification and storage. Among the various film constructs for gas purification, the mixed matrix membranes (MMMs) have been researched. However, the interaction between fillers and polymers are complicated in such a construction, including the formation of nonselective voids, polymer wrapping, and the fillers adsorption ability. Through molecular dynamics (MD) simulation, we modified the MMM structures with different filler loading and tested the gas permeability. In this research, we constructed the polyimide (6FDA-DAM) and added MOF (UiO-66) as the filler to build the hybrid MMM systems. Density functional theory (DFT) calculation and molecular dynamics routines were used in building MOF and MMM structures. The optimized UiO-66 structure was divided into two significant features which are the tetrahedral cages and the octahedral cages. We tested gas transport performance of MMM by using the grand canonical Monte Carlo (GCMC) method and the gas molecular dynamics calculations, and the effect of the tetrahedral and octahedral cages are discussed. Finally, the experimental results show that the gas solubility and diffusivity are increased with the increasing proportion of fillers, and have a significant enhancement effect. However, due to polymer wrapping, gas polarity and size, tetrahedral and octahedral cages adsorption ability are different, resulting in non-linear relationship.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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