Biomimetic [MFe3S4]3+ Cubanes (M = V/Mo) as Catalysts for a Fischer–Tropsch-like Hydrocarbon SynthesisA Computational Study

Nitrogenase is the enzyme primarily responsible for reducing atmospheric nitrogen to ammonia. There are three general forms of nitrogenase based on the metal ion present in the cofactor binding site, namely, molybdenum-dependent nitrogenases with the iron–molybdenum cofactor (FeMoco), the vanadium-dependent nitrogenases with FeVco, and the iron-only nitrogenases. It has been shown that the vanadium-dependent nitrogenases tend to have a lesser efficacy in reducing dinitrogen but a higher efficacy in binding and reducing carbon monoxide. In biomimetic chemistry, [MFe3S4] (M = Mo/V) cubanes have been synthesized, studied, and shown to be promising mimics of some of the geometric and electronic properties of the nitrogenase cofactors. In this work, a density functional theory (DFT) study is presented on Fischer–Tropsch catalysis by these cubane complexes by studying CO binding and reduction to hydrocarbons. Our work implies that molybdenum has stronger binding interactions with the iron–sulfur framework of the cubane, which results in easier reduction of substrates like N2H4. However, this inhibits the binding and activation of CO, and hence, the molybdenum-containing complexes are less suitable for Fischer–Tropsch catalysis than vanadium-containing complexes.固氮酶（Nitrogenase）是介导大气双氮还原为氨的核心酶类。根据辅因子结合位点所含金属离子的差异，固氮酶可分为三大类别：携带铁钼辅因子（FeMoco）的钼依赖型固氮酶、携带FeVco的钒依赖型固氮酶，以及仅含铁的固氮酶。已有研究证实，钒依赖型固氮酶在还原双氮的效能上相对较弱，但在结合与还原一氧化碳方面的表现更为优异。在仿生化学领域，[MFe3S4]（M = Mo/V）立方烷配合物已被成功合成与研究，且被证明可有效模拟固氮酶辅因子的部分几何与电子特性。本研究针对此类立方烷配合物开展了密度泛函理论（DFT）研究，聚焦其催化费托（Fischer–Tropsch）过程中一氧化碳的结合与还原为烃类的反应。研究结果表明，钼与立方烷的铁硫骨架之间具有更强的结合作用，这使得肼（N2H4）等底物的还原过程更为便捷。但该特性会抑制一氧化碳的结合与活化，因此含钼的立方烷配合物相较含钒的同类配合物，更不适用于费托催化反应。