以計算化學方法研究金屬錯合物在 MOF-253 下吸附相異 η 構型 CO2 後與頁岩氣做羥基化反應

Abstract

近年來多數研究顯示透過過渡金屬加入到有機金屬框架(Metal Organic Frameworks, MOF)被認為是具有提高各類化學反應之催化性的方法，尤其在CO2 Reduction Reaction (CO2RR) 反應更是廣泛的被討論。在本篇論文中使用有機金屬框架MOF-253在聯吡啶 (bipyridine) 鉗合位上加入過渡金屬，然後使這過渡金屬用來做吸附CO2的活性位點，並且探討過渡金屬吸附CO2時所產生的兩種η構型─η1-CO2、η2-CO2。後續深入研究過渡金屬之活性位點吸附η1-CO2、η2-CO2後與頁岩氣(Shale Gas)主要成分─甲烷、乙烷、丙烷，進行羥基化反應(Hydroxylation) 探討其反應機制，而這些過渡金屬的篩選及反應機構探討都將會透過電子密度泛函理論 (Density Functional Theory,DFT) 下進行計算模擬，綜合上述之反應機構的探討及過渡金屬在MOF-253立體障礙的限制，研究結果顯示第四周期到第六周期的過渡金屬中(鑭系元素、和鉿元素除外)，Ru金屬的CO2吸附結構為η1-CO2類型，而其他金屬則較偏向η2-CO2的吸附結構，MOF-253在嵌合後不論是吸附CO2亦或是頁岩氣的羥基化都有不錯的反應性。

Adding transition metals to metal organic frameworks (MOFs) is considered a way to improve the catalytic ability of MOFs. In the study, MOF-253 is chosen by containing the bipyridine coordination sites and then the transition metal is chelated in bipyridine coordination sites to adsorb CO2. There are two η configurations called η1- CO2 and η2- CO2 we will discuss the active sites of transition metals that adsorb η1- CO2 and η2- CO2. After adsorbing CO2, we discuss the shale gas (methane, ethane, and propane) hydroxylation mechanistic steps. Importantly, all of metal elements of the 4th – 6th periods are taken into account as the catalytic sites in the current Density Functional Theory (DFT) calculations, except Lanthanides and Hafnium. In the end, the best transition metal is Vanadium in adsorbing η1 -CO2, the other one is Ruthenium in adsorbing η2 -CO2. Both of them have good effects in the adsorption of CO2 and the hydroxylation of shale gas.