Bello T O, Alvim R S, Bresciani A E, Nascimento C A O, Alves R M B
Department of Chemical Engineering, Escola Politécnica, Universidade de São Paulo, São Paulo, Brazil.
J Mol Model. 2024 Jun 27;30(7):231. doi: 10.1007/s00894-024-06013-z.
The conversion of carbon dioxide (CO) to formic acid (FA) through hydrogenation using 1-ethyl-2,3- dimethyl imidazolium nitrite (EDIN) ionic liquid was studied to understand the catalytic roles within EDIN. CO hydrogenation in various solvents has been explored, but achieving high efficiency and selectivity remains challenging due to the thermodynamic stability and kinetic inertness of CO. This study explored two mechanistic pathways through theoretical calculations, revealing that the nitrite (NO) group is the most active site. The oxygen site on nitrite favorably activates H2, while the nitrogen site shows a minor activation barrier of 108.90 kJ/mol. The Gibbs energy variation indicates stable FA formation via EDIN, suggesting effective hydrogen (H) activation and subsequent CO conversion. These insights are crucial for developing improved catalytic sites and processes in ionic liquid catalysts for CO hydrogenation.
Quantum chemical calculations were conducted using the ORCA software package at the Restricted Hartree-Fock (RHF) and density functional theory (DFT) levels. The RHF method, known for its predictive abilities in simpler systems, provided a baseline description of electronic structures. In contrast, DFT was employed for its effectiveness in complex interactions involving significant electron correlation. A valence triple-zeta polarization (def2-TZVPP) basis set was employed for both RHF and DFT, ensuring accurate and correlated calculations. The B3LYP functional was utilized for its rapid convergence and cost-efficiency in larger molecules. Dispersion corrected functionals (DFT-D) addressed significant dispersion forces in ionic liquids, incorporating Grimme's D2, D3, and D4 corrections. Geometry optimizations, kinetics, and thermodynamic calculations were performed in the gas phase. The Nudged Elastic Band Transition State (NEB-TS) approach, combining Climbing Image-NEB (CINEB) and Eigenvector-Following (EF) methods, was used to find the minimum energy path (MEP) between reactants and products. Thermochemical analyses based on vibrational frequency calculations evaluated properties such as Enthalpy, Entropy, and Gibbs energy using ideal gas statistical mechanics.
研究了使用1-乙基-2,3-二甲基咪唑鎓亚硝酸盐（EDIN）离子液体通过氢化将二氧化碳（CO）转化为甲酸（FA）的过程，以了解EDIN中的催化作用。已经探索了在各种溶剂中的CO氢化反应，但由于CO的热力学稳定性和动力学惰性，实现高效率和高选择性仍然具有挑战性。本研究通过理论计算探索了两条反应机理途径，揭示了亚硝酸盐（NO）基团是最活跃的位点。亚硝酸盐上的氧位点有利于活化H2，而氮位点显示出108.90 kJ/mol的较小活化能垒。吉布斯自由能变化表明通过EDIN形成FA是稳定的，这表明有效的氢（H）活化以及随后的CO转化。这些见解对于开发用于CO氢化的离子液体催化剂中改进的催化位点和过程至关重要。
使用ORCA软件包在受限哈特里-福克（RHF）和密度泛函理论（DFT）水平上进行量子化学计算。RHF方法以其在较简单体系中的预测能力而闻名，它提供了电子结构的基线描述。相比之下，DFT因其在涉及显著电子相关性的复杂相互作用中的有效性而被采用。RHF和DFT均采用价三重ζ极化（def2-TZVPP）基组，以确保准确且相关的计算。B3LYP泛函因其在较大分子中的快速收敛性和成本效益而被使用。色散校正泛函（DFT-D）考虑了离子液体中的显著色散力，纳入了Grimme的D2、D3和D4校正。在气相中进行几何优化、动力学和热力学计算。采用将爬山图像弹性带（CINEB）和本征向量跟踪（EF）方法相结合的推挤弹性带过渡态（NEB-TS）方法来寻找反应物和产物之间的最小能量路径（MEP）。基于振动频率计算的热化学分析使用理想气体统计力学评估诸如焓、熵和吉布斯自由能等性质。
