中央研究院 原子與分子科學研究所

We have shown that ³¹P solid-state nuclear magnetic resonance (SS-NMR) of adsorbed trialkylphosphine oxides (R₃PO) is capable of providing important acid properties, viz. types (Brønsted vs. Lewis acids), location, strength, and concentration, of acid sitesin solid acids. In continuing of such a R&D endeavor, we have also adopted density functional theory (DFT) calculations to confirm that ³¹PNMRchemical shifts of adsorbed R₃POprobe molecules increase linearly with the acidic strength (J. Phys. Chem. B 112, 4496, 2008；J. Phys. Chem. A 112, 7349, 2008), as been demonstrated by a variety of different solid acid systems, such as zeolites, metal oxides, and heteropolyacids(HPAs；J. Phys. Chem. C 114, 15464, 2010). It has been shown that such acidity characterization technique not only capable of identifying solid acids with a wide variety of acidic strengths covering from weak, medium, strong, to super acids, but also applicable for liquid acids. The ³¹P chemical shifts of the adsorbed R₃POtherefore offer a reliable and revolutionary acidity scale for both solid as well as liquid acids; more details may be found in recent review articles (Chin. J. Magn. Reson. 27, 485, 2010; Phys. Chem. Chem. Phys. 13, 14889, 2011).