亀山周太郎君、小森大輝君が中心となって行った疎水性表面を有するブレンステッド酸ゲル触媒に関する研究成果がJournal of the American Chemical Society誌(ACS)にAcceptされました。Our paper reporting Brønsted acid property of sulfo-functionalized siloxane gels with surface hydrophobicities was published in JACS (ACS).

「Quantitative Evaluation of the Effect of the Hydrophobicity of the Environment Surrounding Brønsted Acid Sites on Their Catalytic Activity for the Hydrolysis of Organic Molecules」Miura, Hiroki; Kameyama, Shutaro; Komori, Daiki; Shishido, Tetsuya

Journal of the American Chemical Society, 2019, 141, 1393-1796, DOI:10.1021/jacs.8b11471

Sulfo-functionalized siloxane gels with a variety of surface hydrophobicities were fabricated to elucidate the effect of the environment surrounding the Brønsted acid site on their catalytic activity for the hydrolysis of organic molecules. A detailed structural analysis of these siloxane gels by elemental analysis, X-ray photoelectron spectroscopy, Fourier-transformed infrared (FT-IR) and 29Si MAS NMR revealed the formation of gel catalysts with a highly condensed siloxane network, which enabled us to quantitatively evaluate the hydrophobicity of the environment surrounding the catalytically active sulfo-functionality. A sulfo group in a highly hydrophobic environment exhibited excellent catalytic turnover frequency for the hydrolysis of acetate esters with a long alkyl chain, whereas not only conventional solid acid catalysts but also liquid acids showed quite low catalytic activity. Detailed kinetic studies corroborated that the adsorption of oleophilic esters at the Brønsted acid site was facilitated by the surrounding hydrophobic environment, thus significantly promoting hydrolysis under aqueous conditions. Furthermore, sulfo-functionalized siloxane gels with a highly hydrophobic surface showed excellent catalytic activity for the hydrolytic deprotection of silyl ethers.