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

Abstract

Effective capture and utilization of CO2 is critical to reduce greenhouse gas emissions and to reach the low-carbon economy target. Herein, bismuth oxides with four different crystallized phases (α-, β-, δ-, γ-) are successfully synthesized and employed for the first time as photo, thermal, and photothermal catalysts for the successful catalytic carbonylation of isobutyl amine with CO2 to N,N′-diisobutylurea. The results displayed that the photothermal catalytic performances of Bi2O3 polymorphs followed the order of α-Bi2O3 > δ-Bi2O3 > γ-Bi2O3 > β-Bi2O3, in which the conversion of i-BuNH2 and the selectivity of N,N′-diisobutylurea for α-Bi2O3 was 50.38% and 91.79%, respectively, using N-methyl-2-pirrolidinone (NMP) as solvent and 500 W Xe lamp as the light source under the conditions of 1.0 MPa CO2 (initial pressure at room temperature) and 4 h reaction time at 100 °C. Further characterization of Bi2O3 polymorphs including XRD, SEM, BET, XPS, EPR, TPC, PL, and UV–vis absorption spectra reveals that such differences in the photothermal catalytic activity of Bi2O3 could be closely related to the efficiencies of photoinduced carriers separation. And the surface oxygen vacancies rather than bulk oxygen vacancies are favorable for the improvement of their both thermal and photothermal catalytic performances in the carbonylation of i-BuNH2 with CO2.