Enhanced photocatalytic degradation of π-donor organic compounds by N,N′-dialky 1-4,4′-bipyridinium-modified TiO₂ particles

TiO₂ powders (Degussa P-25) were modified by a bipyridinium V²⁺ monolayer. The resulting modified V²⁺-TiO₂ photocatalyst reveals enhanced activities for the light-induced degradation of the series of organic compounds, 1,4-dimethoxybenzene (1), 1,2-dimethoxybenzene (veratrole) (2), indole (3) and eosin (4), exhibiting electron donor properties. Photodegradation of p-chlorobenzaldehyde (5) which lacks electron donor properties is inhibited in the presence of the modified photocatalyst V²⁺-TiO₂, whereas it degrades in the presence of unmodified TiO₂. The enhanced photodegradation of the series of electron-rich compounds is attributed to the formation of a supramolecular donor-acceptor complex with the bipyridinium units at the semiconductor surface. Concentration of the organic materials at the s.c. surface leads to effective utilization of photogenerated O₂^.- and effective mineralization.