Operando DRIFTS and NMR Spectroscopy Study of Hydrolytic and Photoinduced Transformations of Dimethyl Succinate on TiO ₂ and CeO ₂

Dimethyl succinate (DMS), a common component of dibasic esters (DBEs) widely used as solvent mixtures in the paint and polymer industries, may contribute to total indoor volatile organic compound (VOC) emissions, prompting the investigation of its fate and transformations. As shown here by operando DRIFTS and NMR spectroscopy, DMS interacts strongly with titania- and ceria-based materials, leading to spontaneous and sustained hydrolytic decomposition, which is realized through carboxyl ester bond hydrolysis. The main degradation products are surface-bound succinate and methanol, which can also be slowly desorbed from the surface. Solar light photodecomposition of adsorbed species, especially methoxy species preformed by hydrolysis, can lead to the formation of secondary products, such as surface-bound formates, formaldehyde, or formic acid on titania, while on nanoceria, mainly formates and carbonates are formed. As demonstrated, although DMS is not considered toxic, its interaction with reactive and photoactive surfaces may lead to secondary potentially hazardous products, and the fate and potential risks of new VOC and semivolatile VOC (SVOC) compounds in indoor air should be carefully considered.