Insight into Relationship between the Products Distribution and Molecular Properties in Carboxylation between Benzene Polycarboxylic Acids and CO₂

CO₂ is an important carbon resource, which could be chemically utilized by carboxylation. In this paper, the carboxylation between benzene polycarboxylic acids (BPCAs) and CO₂ was conducted using Cs₂CO₃ as a catalyst. The relationship between the product distribution and Mulliken charge at the reaction site of BPCAs was explored by combining experiments and quantum chemical calculations of molecular properties in the reaction of carboxylation between BPCAs and CO₂. The negative Mulliken charge was found to facilitate carboxylation at the reaction site of BPCAs. Hydrogen abstraction was the rate-determining step for carboxylation, and its energy barrier was calculated for different C–H in the BPCA molecule. The results showed that the C–H bond with the more negative Mulliken charge was more easily deprotonated, which further verified the above conclusion. The study provides a convenient approach to predict a product distribution for carboxylation between BPCAs and CO₂ according to the Mulliken charge of BPCAs.