Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, 19716, USA.
Catalysis Center for Energy Innovation, University of Delaware, Newark, DE, 19716, USA.
Nat Commun. 2023 Apr 21;14(1):2293. doi: 10.1038/s41467-023-37962-3.
Oxygen-containing carbons are promising supports and metal-free catalysts for many reactions. However, distinguishing the role of various oxygen functional groups and quantifying and tuning each functionality is still difficult. Here we investigate the role of Brønsted acidic oxygen-containing functional groups by synthesizing a diverse library of materials. By combining acid-catalyzed elimination probe chemistry, comprehensive surface characterizations, N isotopically labeled acetonitrile adsorption coupled with magic-angle spinning nuclear magnetic resonance, machine learning, and density-functional theory calculations, we demonstrate that phenolic is the main acid site in gas-phase chemistries and unexpectedly carboxylic groups are much less acidic than phenolic groups in the graphitized mesoporous carbon due to electron density delocalization induced by the aromatic rings of graphitic carbon. The methodology can identify acidic sites in oxygenated carbon materials in solid acid catalyst-driven chemistry.
含氧碳是许多反应中很有前途的支持物和无金属催化剂。然而，区分各种含氧官能团的作用并量化和调整每种官能团的作用仍然很困难。在这里，我们通过合成各种材料来研究 Brønsted 酸性含氧官能团的作用。通过结合酸催化消除探针化学、全面的表面特性、N 同位素标记乙腈吸附与魔角旋转核磁共振、机器学习和密度泛函理论计算，我们证明了酚类是气相化学中主要的酸位，而令人惊讶的是，在石墨化介孔碳中，由于石墨碳的芳环引起的电子密度离域，羧酸基团的酸性远低于酚类基团。该方法可用于识别固体酸催化剂驱动化学中含氧碳材料中的酸性位。
