Silica Nanopowder Supported Frustrated Lewis Pairs for CO2 Capture and Conversion to Formic Acid

• DOI: 10.1021/acs.inorgchem.0c02012
• Publication Date: 2020-12-22T17:43:31Z
• Authors: Kgauhelo Mentoor; Linette Twigge; J. W. Hans Nieman...; Jannie C. Swarts; Elizabeth Erasmus
• Keywords: Frustrated Lewis pair; Attenuated total reflection; Magic angle spinning

Treatment of hydroxylated silica nanopowders S1 and allyl-functionalized S2 with 3-(diphenylborano)- or 3-bis(pentafluorophenylborano)propyltrimethoxysilane 2-(diphenylphosphino)- 2-(dicyclohexylphosphino)ethyltriethoxysilane generates nanopowder supported Lewis acids S3 bases S4. These surfaces were characterized by 13C, 11B, 31P cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR FTIR). When is combined solution-phase PR3 (R = C6F5, C6H5, mesityl), six associated frustrated pairs (FLPs) are formed. In another set reactions, the interactions between S4 BR3 R mesityl produced more FLPs. The capture CO2 these FLPs producing FLP-CO2 pair adducts S5 S6 highlighted ATR FTIR, it was found that FLP S5e C6H5 on both acid base trapped largest quantities supports. Conversion to HCOOH achieved first activating H2 generate activated FLP-H2 S7 S9. Addition then generated via FLP-HCOOH S8 S10. Qualitative identification generation FTIR measurements, surface 10b proved be most successful bound in generation. some cases, diborano formates (−BO(CH)OB−) S11 S12 also identified as side products during formation. Spectroscopic characterization purposefully synthesized included 11B CP NMR.