Photo-reduction of the riboflavins, flavin mononucleotide (FMN) and flavin adenosine dinucleotide (FAD) to FMNH₂ and FADH₂, respectively, is a well-known two-electron two-photon process. The resulting FMNH₂ and FADH₂ are involved in two-electron transfer reactions to a given substrate. Given that catalysts capable of delivering two electrons are attractive toward the dehalogenation of chlorinated ethylenes, we examined the reactivity of FMNH₂ and FADH₂ with dichloroethylene (DCE), trichloroethylene (TCE) and tetrachloroethylene (PCE) in aqueous solution. However, no products were observed after 48 hours of reactivity. On the other hand, FMNH₂ and FADH₂ anchored to nanocrystalline titanium dioxide via the phosphonic acid functional groups, reacted rapidly with DCE, TCE, and PCE. Origins of the enhanced reactivity and the reaction mechanisms of ribofalvin functionalized titanium dioxide nanoparticles with chlorinated ethylenes will be presented.