There has been growing interest in the CO₂ capture and reduction by transition-metal-free catalysts. Here we performed a proof-of-concept study using an ab initio valence bond method called the block-localized wave function (BLW) method. The integrated BLW and density function theory (DFT) computations demonstrated that heterobimetallic Ae⁺/Al(I) (Ae represents alkaline earth metals Mg and Ca) Lewis acid/base combinations without transition metals can facilely capture and activate CO₂. There are two remarkable findings in this study. The first concerns the ionic nature of the metal–metal bonds. The experimentally synthesized low valent aluminum compound with a bidentate β-diketiminate (BDI) ligand, or (BDI)Al(I) in brief, is a Lewis base due to the lone pair on the aluminum cation though overall Al(I) is positively charged. Al(I) can form ionic metal–metal bonds with the alkaline earth metals of the positively charged Lewis acids (BDI)Ae⁺. This type of ionic metal–metal bonds is counterintuitive and antielectrostatic as both metals carry positive charges. The second finding is the CO₂ activation mechanism. (BDI)Al(I) can effectively bind and activate CO₂ by transferring one electron to CO₂, and the resulting complex can be best expressed as [(BDI)Al(I)]⁺[CO₂]⁻. The participation of (BDI)Ae⁺ further enhances the capture and activation of CO₂ by (BDI)Al(I).

中文翻译：

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可激活 CO2 的抗静电主族金属-金属键

人们对通过无过渡金属催化剂捕获和还原CO _{2 的}兴趣越来越大。在这里，我们使用称为块局域波函数 (BLW) 方法的从头价键方法进行了概念验证研究。集成的 BLW 和密度函数理论 (DFT) 计算表明，异质双金属 Ae ⁺ /Al(I)（Ae 代表碱土金属 Mg 和 Ca）路易斯酸/碱组合没有过渡金属可以轻松捕获和激活 CO ₂. 这项研究有两个显着的发现。第一个涉及金属-金属键的离子性质。实验合成的具有双齿 β-二酮亚胺 (BDI) 配体的低价铝化合物，或简称 (BDI)Al(I)，由于铝阳离子上的孤对是路易斯碱，尽管整体 Al(I) 是正的带电。Al(I) 可以与带正电的路易斯酸 (BDI)Ae ⁺的碱土金属形成离子金属-金属键。这种类型的离子金属 - 金属键是违反直觉和抗静电的，因为这两种金属都带有正电荷。第二个发现是CO ₂活化机制。（BDI）的Al（I）可以有效结合并激活CO ₂通过一个电子转移到CO ₂，并且得到的复合物可以最好地表示为 [(BDI)Al(I)] ⁺ [CO ₂ ] ^-。(BDI)Ae ⁺的参与进一步增强了(BDI)Al(I)对CO ₂的捕获和活化。