Effect of space linkers in dinuclear copper cryptates on the efficiency of atmospheric CO2 uptake: a DFT study
Effect of space linkers in dinuclear copper cryptates on the efficiency of atmospheric CO2 uptake: a DFT study
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DOI：
10.1039/c3cy20608d
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发表时间：
2013-08
影响因子：
5
通讯作者：
Morad M. El-Hendawy;S. Bandaru;Niall J. English;D. Mooney
中科院分区：
文献类型：
--
作者：
Morad M. El-Hendawy;S. Bandaru;Niall J. English;D. Mooney
近年来，双核铜隐酸盐作为大气中二氧化碳的固定催化剂受到了广泛的关注。在这种情况下，催化剂通常通过对二氧化碳中相对不活跃的碳原子进行亲核攻击，将二氧化碳水合成碳酸氢盐。本研究试图通过用其他芳香族或杂环单元取代头基间苯来改变空间连接基，从而开发这种模型的催化剂。将密度泛函理论(DFT)应用于相关的级联反应机理，考察了这些新型催化剂的效率。计算了吉布斯自由能分布，以考察沿途所有驻点的能级和几何构型。最重要的结果是，与含有噻吩环的双核隐酸盐相连的隐酸盐被预测为吸收二氧化碳的最有效催化剂。因此，建议测试这种隐酸盐作为二氧化碳固定的受体。在这项研究中，我们首先测试了四个DFT函数，即M06L，B97D MPW1K和B3LYP，在实验中发现了呋喃连接的加密中间体。在这些函数中，M06L得到的几何参数最接近于实验结晶学研究得到的几何参数。我们还研究了[Cu2-m-ben]4+的分子内H2O加成反应，并根据计算的活化势垒和pKA计算解释了质子消除步骤。在M06L理论水平上考察了两种不同的(间-木基和硫代)双核隐酸盐连接的间隔基对CO2固定反应途径的影响。
In recent years, dinuclear copper cryptates have been investigated for their ability as catalysts for the fixation of atmospheric CO2. In this context, the catalyst normally hydrates CO2 to its bicarbonate form via nucleophilic attack on the relatively inactive carbon atom in CO2. The present study attempts to develop this model of catalyst by changing the space linker via replacement of the head unit, meta-benzene, with other aromatic or heterocyclic units. The efficiency of these novel catalysts is examined by Density Functional Theory (DFT) applied to the associated cascade-reaction mechanism. The Gibbs free energy profiles are computed to examine the energetics and geometries of all stationary points along the pathway. The most significant result is that cryptates linked to the dinuclear cryptate involving thiophene rings are predicted to be the most efficient catalyst in the uptake of CO2. Consequently, testing of this cryptate as a receptor for CO2 fixation is to be recommended. In this present study, we initially tested four DFT functions i.e. M06L, B97D MPW1K and B3LYP on experimentally found furano-linked cryptate intermediates. Among these functions, M06L proves to yield geometrical parameters closest to those obtained from experimental crystallographic studies. We also examine the intramolecular H2O addition to [Cu2-m-ben]4+ and the proton elimination steps are explained based on computed activation energy barriers and pKa calculations. Two different (m-xylyl and thio) dinuclear cryptate-linked spacers for CO2 fixation reaction pathways are examined at the M06L level of theory.