Electrocatalytic reduction of low concentration CO2 was selectively and efficiently carried out by using a Re(I) complex with high CO2-capturing ability.
To reduce anthropogenic carbon dioxide (CO2) emissions, it is desirable to develop reactions that can efficiently convert low concentrations of CO2, present in exhaust gases and ambient air, into industrially important chemicals, without involving any expensive separation, concentration, compression, and purification processes. Here, we present an efficient method for synthesizing urea derivatives from alkyl ammonium carbamates. The carbamates can be easily obtained from low concentrations of CO2 as present in ambient air or simulated exhaust gas. Reaction of alkyl ammonium carbamates with 1,3-dimethyl-2-imidazolidinone solvent in the presence of a titanium complex catalyst inside a sealed vessel produces urea derivatives in high yields. This reaction is suitable for synthesizing ethylene urea, an industrially important chemical, as well as various cyclic and acyclic urea derivatives. Using this methodology, we also show the synthesis of urea derivatives directly from low concentration of CO2 sources in a one-pot manner.
Organic
syntheses, such as that of N-substituted
carbamic acid esters (CAEs), utilizing low purity and low concentrations
of CO2 directly, may help achieve two important goalsreducing
CO2 emission and producing useful core chemicals without
the energy-consuming processes of purifying and concentrating CO2. Here, we demonstrate a new synthetic approach for CAEs that
uses a combination of two types of CO2 capture mechanisms,
which are constituted by combining an amine and 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU), and an alcohol and DBU, to form a protonated DBU carbamate
salt and a protonated DBU alkyl carbonate salt, respectively. This
new approach of CAE synthesis can be applied even to the simulated
exhaust gas from fire-power plants, such as 3 vol % of CO2 in N2 or 15 vol % of CO2 in N2,
also containing SO2, NO2, and CO.
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