Highly Efficient Hydrogenation of CO2 to Formic Acid over Palladium Supported on Dication Poly(ionic liquid)s

Carbon dioxide (CO2) emissions from the burning of fossil fuels have seriously aggravated the global greenhouse effect, leading to extreme environmental problems. Thus, the sufficient and effective use of CO2 resources has always been an urgent issue. Herein, dication poly(ionic liquid)s (PILs)-supported palladium nanoparticles (Pd NPs) were designed to catalyze the hydrogenation of CO2 to formic acid (FA) under mild conditions. The prepared catalysts were characterized by FT-IR, ICP, SEM, TEM, XPS, and other techniques. Results indicate that due to the strong metal-support interactions in the resultant catalysts, PILs are constructed by the IL units comprising dications and hydrophobic anions (bis(trifluoromethanesulfonyl)amide, Tf2N-) that can uniformly disperse Pd NPs and enhance the catalytic hydrogenation of CO2 to FA. The effect of various factors on CO2 conversion is also investigated. Turnover frequency (TOF) can reach as high as 13.32 s(-1) when using 1%Pd/PIL-2-Tf2N as a catalyst under the conditions of 80 degrees C, 1 h, 2 MPa pressure of CO2, and 0.88 M sodium borohydride aqueous solution, and the maximum amount of the obtained FA can reach up to 82% of the theoretical value. A possible mechanism of catalytic hydrogenation of CO2 to FA is proposed according to the product analysis. This study highlights that PIL, as support, can promote the catalytic performance, and the resulting catalyst has potential application value for the CO2 industry.

Automated summary

This study designed dication PILs-supported Pd NPs for catalyzing the hydrogenation of CO2 to FA, showing the potential of PILs to enhance catalytic performance.