Ma Denghui, Li Jianming, Cao Zexing
School of New Energy, Ningbo University of Technology, Ningbo 315336, P. R. China.
State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 360015, P. R. China.
Inorg Chem. 2024 Nov 4;63(44):21110-21120. doi: 10.1021/acs.inorgchem.4c03309. Epub 2024 Oct 24.
Acetic acid (CHCOOH), as an industrially important petrochemical product, is predominantly produced via multistep energy-intensive processes. The development of a rhodium single-site heterogeneous catalyst has received considerable attention due to its potential to transform CH into CHCOOH in a single step. Herein, the reaction mechanism for the generation of CHCOOH from CH, CO, and HO catalyzed by Rh-functionalized metal-organic framework (MOF) UiO-67 and the selectivity of products CHCOOH, formic acid (HCOOH), methanol (CHOH), and acetaldehyde (CHCHO) under the oriented external electric fields (OEEFs) were systematically explored by density functional theory (DFT) calculations. The results reveal that the insertion of CO into Rh-CH is the rate-determining step with a free energy barrier of 21.0 kcal/mol in CH carbonylation to CHCOOH. Upon applying an OEEF of = +0.0050 au along the C-C bond, the rate-determining step shifts toward HO decomposition with the barrier of 19.6 kcal/mol, significantly improving the selectivity for CHCOOH production, compared to the major competitive HCOOH route. The Brønsted-Evans-Polanyi (BEP) relationships between key transition states, field strength, and NPA charge transfer were established. This study may guide the rational design of atomically dispersed MOF catalysts for the selective coconversion of CH and CO to CHCOOH using HO as the oxidant under the OEEF.
乙酸（CH₃COOH）作为一种具有重要工业价值的石化产品，主要通过多步耗能工艺生产。铑单中心多相催化剂的开发因其有望一步将CH₄转化为CH₃COOH而备受关注。在此，通过密度泛函理论（DFT）计算，系统地探索了由铑功能化金属有机框架（MOF）UiO - 67催化CH₄、CO和H₂O生成CH₃COOH的反应机理，以及在定向外部电场（OEEF）下产物CH₃COOH、甲酸（HCOOH）、甲醇（CH₃OH）和乙醛（CH₃CHO）的选择性。结果表明，在CH₄羰基化生成CH₃COOH的过程中，CO插入Rh - CH₃是速率决定步骤，自由能垒为21.0 kcal/mol。当沿C - C键施加 = +0.0050 au的OEEF时，速率决定步骤转变为H₂O分解，能垒为19.6 kcal/mol，与主要竞争的HCOOH路径相比，显著提高了CH₃COOH生成的选择性。建立了关键过渡态、场强和NPA电荷转移之间的布朗斯特 - 埃文斯 - 波拉尼（BEP）关系。该研究可为在OEEF下以H₂O为氧化剂将CH₄和CO选择性共转化为CH₃COOH的原子分散MOF催化剂的合理设计提供指导。
