Formation, Location, and Photocatalytic Reactivity of Methoxy Species on Keggin 12-H3PW12O40: A Joint Solid-State NMR Spectroscopy and DFT Calculation Study

Abstract

Solid-state NMR experiments and quantum chemical Density Functional Theory (DFT) calculations were employed to investigate the formation, location, and photocatalytic reactivity of methoxy species on anhydrous 12-H3PW12O40. Two different types of methoxy species were identified on the methanol-adsorbed 12-H3PW12O40 catalyst. Rotational Echo DOuble Resonance (REDOR) NMR experiments combined with quantum chemical DFT calculations demonstrated that the two corresponding methyl groups reside on the O-c and O-d atoms of the Keggin anion, forming the surface OcCH3 and OdCH3 species. Photocatalytic experiments further indicated that the two methoxy species are both photochemically reactive species with the OdCH3 species being much more reactive, and the methoxy species are preferentially mineralized to the final product CO2 directly.