Sulfonated Metal-Oxide Surfaces: What Makes them So Acidic?

Abstract

ABSTRACTWhile some metal-oxide surfaces can be classified as acidic, after reacting with H2SO4 their acidity can be even higher than the parent sulfuric acid. In this paper, ab initio electronic structure calculations (3-21G+*//3-21G*) were performed on a series of model surfaces to examine these sulfonated species as strong, possibly even superacids. Our results indicate that the polarizing nature of the metal-oxide / sulfonate interaction stabilizes strong Bronsted and Lewis acid sites at the M-O surface and the sulfur center. Thermodynamic analysis has been performed to provide information for experimental verification.