CH Carbonylation to Acetic Acid Using HO as an Oxidant on a Rh-Functionalized UiO-67 Combined with Oriented External Electric Fields: Selectivity and Mechanistic Insights from DFT Calculations.

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.