擁有分子篩機制的薄膜在氣體分離方面有許多顯著的突破，本研究以 模擬輔佐實驗探討氣體分離之機制為動機，與京都大學物質 -細胞綜合系統研究所Sivaniah Group合作並探討兩種薄膜類型，分別為 鋯金屬有機框架與石墨烯薄膜。第一種研究的薄膜為鋯金屬有機框架，為了探討不同配位機對於氣體分離在通透量與選擇性的影響，本研究從X光繞射的結晶數據得到原始數據，並系統性的清理得到最穩定的結構。在定義氣體路徑後利用基於密度泛涵理論之nudged elastic band計算其能量路徑，並比較不同配位機 的能量路徑與實驗測量到的選擇性。數據顯示，不同配位機的形成的窗口大小影響了氣體的選擇性，也說明了分子篩薄膜中氣體分離的機制。 第二個研究探討了石墨烯層間厚度與氣體分離的關係。本研究採取兩種 分析手法，分別為非平衡系統分子動力學與勻相薄膜 分析 進行模擬。 從勻相薄膜分析得出，證明了層間厚度影響吸附能之重要性。而從非平衡系統分子動力學所模擬數據也符合實驗測量之選擇性，也根據氣體位置，了解氣體通透薄膜的詳細過程。;Possessing both high permeability and selectivity, inorganic membranes with molecular sieving mechanism are raising attention among researchers. In collaboration with iCeMS Sivaniah group, two types of molecular sieving membranes were investigated with computational methods. In our first project, to understand how different ligands affect the selectivity in UiO-66 based MOFs, we constructed the models from XRD data. Nudged elastic band (NEB) method is then implemented for the diffusion pathway to calculate the energy barrier difference. Our results matched the selectivity measured in experiment, which indicates the molecular sieving mechanism from different degree of gate restriction. The second project involves simulations on graphene membrane due to its outstanding permeability and selectivity measured from experiment, we discussed how the interlayer spacing of graphene affects the permeability. Non-equilibrium molecular dynamics and confined membrane simulation were carried out in this study. A critical interspacing of 6.375 Å was detected, where the adsorption energy of CH4 surpasses N2 when we gradually increase the thickness. The calculated selectivities from NEMD simulation also agree well with experimental results. Snapshots of NEMD simulation are taken to analyze the gas position as a function of simulation time.
