Photothermal Cocatalytic Carbonylation of Isobutyl Amine with CO₂ over Bi₂O₃ Polymorphs under Visible-Light Irradiation

Effective capture and utilization of CO2 iscriticalto reduce greenhouse gas emissions and to reach the low-carbon economytarget. Herein, bismuth oxides with four different crystallized phases(alpha-, beta-, delta-, gamma-) are successfully synthesizedand employed for the first time as photo, thermal, and photothermalcatalysts for the successful catalytic carbonylation of isobutyl aminewith CO2 to N,N '-diisobutylurea.The results displayed that the photothermal catalytic performancesof Bi2O3 polymorphs followed the order of alpha-Bi2O3 > delta-Bi2O3 >gamma-Bi2O3 > beta-Bi2O3, in whichthe conversion of i-BuNH2 and the selectivity of N,N '-diisobutylurea for alpha-Bi2O3 was 50.38% and 91.79%, respectively, using N-methyl-2-pirrolidinone (NMP) as solvent and 500 W Xe lampas the light source under the conditions of 1.0 MPa CO2 (initial pressure at room temperature) and 4 h reaction time at100 degrees C. Further characterization of Bi2O3 polymorphs including XRD, SEM, BET, XPS, EPR, TPC, PL, and UV-visabsorption spectra reveals that such differences in the photothermalcatalytic activity of Bi2O3 could be closelyrelated to the efficiencies of photoinduced carriers separation. Andthe surface oxygen vacancies rather than bulk oxygen vacancies arefavorable for the improvement of their both thermal and photothermalcatalytic performances in the carbonylation of i-BuNH2 withCO(2).