金屬有機骨架疏水修飾及二氧化碳捕捉應用研究

Abstract

金屬有機骨架(Metal Organic Framework, MOF) 是一種常見的功能性孔洞材料，因其製備方法簡單、官能基可設計性、可調節的孔徑且具有高比表面積等優點使其成為研究中常見的材料。由於其微孔尺寸窄且具有路易斯鹼性位點可以作為二氧化碳捕捉的優良固體吸附劑。本研究以簡單的矽烷偶合反應使親水性MOF具有疏水性，成功解決濕度敏感MOF的水穩定性問題。疏水修飾後MOF的水接觸角顯著提高，A520(Al) C1-S 128∘、MOF-303(Al) C1-S 136∘、MIL-101-NH2(Al) C1-S 133∘、MOF-74(Mg) C1-S 98∘。經過疏水修飾後的MOF仍然保持著二氧化碳吸能力，A520(Al) C1-S 2.4 mmol/g、MOF-303(Al) C1-S 4.4 mmol/g， MOF-74(Mg) C1-S 4.5 mmol/g、MIL-101-NH2(Al) C1-S 3.4 mmol/g。研究結果顯示，具有Al-OH結構的MOF是製備矽烷疏水修飾MOF的關鍵條件，透過形成Si-O-Al鍵結，在MOF表面建立疏水塗層，降低與二氧化碳競爭吸附的水氣吸附量。

Metal-organic frameworks (MOFs) are widely studied functional porous materials due to their simplicity of synthesis, designable functional groups, tunable pore sizes, and high surface areas. They are particularly attractive for their potential application as solid adsorbents for carbon dioxide (CO2) capture. However, MOFs can be sensitive to moisture, which influences their stability and performance.In this study, a simple and effective approach was employed to address the moisture sensitivity of MOFs. By utilizing a silane coupling reaction, hydrophilic MOFs were transformed into hydrophobic materials. After hydrophobic modification increased the water contact angles of the MOFs, as demonstrated by the observed values of A520(Al) C1-S at 128°, MOF-303(Al) C1-S at 136°, MIL-101-NH2(Al) C1-S at 133°, and MOF-74(Mg) C1-S at 98°.Importantly, the hydrophobic modification did not compromise the CO2 adsorption capacity of the MOFs. The modified MOFs retained their ability to capture CO2, with adsorption capacities of A520(Al) C1-S at 2.4 mmol/g, MOF-303(Al) C1-S at 4.4 mmol/g, MOF-74(Mg) C1-S at 4.5 mmol/g, and MIL-101-NH2(Al) C1-S at 3.4 mmol/g.The results revealed that the presence of an Al-OH structure in the MOFs played a crucial role in the successful hydrophobic modification. Through the formation of Si-O-Al bonds, a hydrophobic coating was created on the surface of the MOFs, which effectively reduced the moisture adsorption competing with CO2 adsorption.Overall, this study demonstrates the successful transformation of hydrophilic MOFs into hydrophobic materials through a simple silane coupling reaction. The hydrophobic modification improved the water stability of the MOFs while preserving their CO2 adsorption capacity, thereby expanding their potential applications in CO2 capture and separation processes.