應用具耐水性金屬有機骨架（MOFs）之混合基質膜於二氧化碳選擇性分離之研究與開發

Abstract

為因應大氣中二氧化碳（CO₂）濃度持續上升的環境議題，並解決直接空氣捕捉（DAC）過程中水氣與 CO₂ 間競爭吸附的問題，本研究著重於開發具有良好耐水性、兼具高 CO₂ 滲透率與 CO₂/N₂ 選擇性的混合基質膜（mixed-matrix membranes, MMMs）。首先，透過 Monte Carlo 模擬計算 5,500 種金屬有機框架材料（MOFs）的亨利常數（KH），以篩選出對 CO₂ 與 H₂O 具中等選擇性的候選材料。最終選定 MIL-53、Al-NDC 與 Al-BDC 三種鋁系 MOFs 進行合成與水氣耐受性測試。透過接觸角量測與熱重–質譜分析（TGA-MS）進行評估，結果顯示 Al-BDC 具有最好的疏水性。接續將 Al-BDC 添加至 Pebax® MH 2030 高分子材料中，製備出MOF含量為 5–20 wt% 的混合基質膜。TGA-MS 與氣體滲透實驗結果顯示，隨著 Al-BDC 含量增加，膜中水氣吸附量下降，證實其可有效降低水氣干擾。另外，含有 15 wt% Al-BDC 的膜展現出優異的 CO₂/N₂ 分離性能（PCO₂：351.89 Barrer，αCO₂/N₂：46.10），表現已接近 Robeson 上限，優於多數文獻中已報導的 MOF–Pebax 複合膜。整體而言，該膜兼具良好的抗水性與分離效率，為未來應用於含有水氣環境下的碳捕捉膜材開發，提供了具體且可行的設計依據。

To address the pressing issue of rising atmospheric carbon dioxide (CO₂) levels and to overcome the challenge of competitive water vapor adsorption in direct air capture environments, this work focuses on the development of water-resistant mixed-matrix membranes (MMMs) with high CO₂ permeability and exceptional CO₂/N₂ selectivity. Monte Carlo simulations were used to screen 5,500 MOFs for moderate CO₂/H₂O selectivity, leading to the selection of three aluminum-based MOFs—MIL-53, Al-NDC, and Al-BDC. These MOFs were synthesized and evaluated for water resistance via contact angle measurements and TGA-MS analysis, with Al-BDC exhibiting the highest hydrophobicity. Al-BDC was subsequently incorporated into Pebax® MH 2030 to fabricate MMMs with filler loadings ranging from 5 to 20 wt%. Comprehensive characterization, including TGA-MS and gas permeability testing, confirmed that Al-BDC-based MMMs decrease water uptake with Al-BDC increasing, indicating that the incorporation of Al-BDC can effectively lower the water uptake. Notably, the 15 wt% Al-BDC membrane exhibited excellent CO₂/N₂ separation performance (PCO2 : 351.89 Barrer, αCO2/N2 : 46.10), approaching the Robeson upper bound more closely than most MOF-Pebax-based MMMs reported in the literature, marking a promising breakthrough in overcoming the traditional permeability–selectivity trade-off using a water-resistant membrane. These findings offer valuable insights for designing practical, high-performance membranes for sustainable carbon capture.