Enhanced photocatalytic dehalogenation of aryl halides by combined poly-p-phenylene (PPP) and TiO2 photocatalysts

Abstract

Abstract The abundant energy provided by sunlight makes visible-light driven photoredox catalysis an attractive means of performing chemical transformations. Titanium dioxide (TiO2) and conjugated polymers are semiconducting materials that have been used as photoredox catalysts. Driving electron transfer process with photoredox catalysts and visible light has become a powerful method for achieving efficient chemical transformations. However, titanium dioxide does not readily absorb visible light, and conjugated polymers have not been extensively studied as photoredox catalysts for organic transformations. In this work, TiO2 and the conjugated polymer poly-p-phenylene (PPP) were successfully used as heterogeneous co-catalysts for the dehalogenation of some simple aryl halides using triethylamine as a sacrificial electron donor. While PPP alone exhibited some photocatalytic activity upon irradiation with visible light, the efficiency of dehalogenation was enhanced by the addition of titanium dioxide. No reaction was observed in the absence of both photocatalysts or when TiO2 was used as the sole photocatalyst. The optimum operating parameters were examined.