Adsorption and Reactions on TiO2: Comparison of N,N‑Dimethylformamide and Dimethylamine

Fourier transform infrared spectroscopy has been employed to study the adsorption and reactions of N,N-dimethylformamide (DMF) and dimethylamine (DMA) on powdered TiO2. DMF can be adsorbed in molecular form with the carbonyl interacting with the surface Lewis site (Ti4+) or in dissociative form of OCN(CH3)2. Theoretical adsorption study of rutile (110) points out that the C* and O atoms of OC*N(CH3)2 are bonded at a two-fold-coordinated O site and a five-fold-coordinated Ti site, respectively. The thermal products of DMF/TiO2 are found to be CO and DMA. Photochemical reaction of DMF on TiO2 in O2 generates CO2, HCOO, and NCO. O2 participates in the reaction with its oxygen atoms incorporated into the three products. DMA can be adsorbed in molecular form and imine species on TiO2. Photoirradiation of DMA/TiO2 in O2 generates CO2, HCOO, NCO, and imine species. Interestingly, DMF and OCN(CH3)2 are produced after postirradiation thermal treatment of DMA on TiO2, possibly from the reaction between residual DMA and HCOO photoproduct.