Tuning the Anion Deficiency of the Bifunctional Bi 2 O 3 Catalyst for the Highly Selective Synthesis of Methyl N -Phenyl Carbamate

In this study, methyl N -phenyl carbamate was synthesized using aniline and dimethyl carbonate with a Bi 2 O 3 catalyst. The catalysts were synthesized using various methods, and their physicochemical properties were determined by techniques such as XRD, N 2 -sorption, FTIR, NH 3 -TPD, CO 2 -TPD, H 2 -TPR, O 2 -TPO, XPS, and EPR. The variations in the catalyst preparation procedure resulted in different crystal facets, as observed by XRD. The optimized catalyst preparation method resulted in mainly cubic crystal phases of Bi 2 O 3 with balanced medium acid and basic surface sites, minimum oxygen vacancy, and redox potential, which promoted the carboxylation pathway and suppressed side-products, achieving 98.5% aniline conversion and 94.3% MPC selectivity at 200 °C with 7.5 wt % catalyst loading with a high productivity of 20.1 g g (cat) –1 h –1 . The catalytic reaction kinetics at different temperatures followed a pseudo-first-order kinetic model with an activation energy of 185 kJ mol –1 . Furthermore, calculations using the DFT method also showed that the optimal adsorption energetics are a result of balanced acid–base sites that are responsible for the catalytic selectivity, as per the Sabatier principle. These results demonstrated that the preparation method, calcination temperature, and acid–base tuning critically govern the active site dispersion and redox behavior, thereby increasing the conversion, selectivity, and overall yield of methyl N -phenyl carbamate synthesis.