The high photocatalytic activity of the Mn2+ doped TiO2 with bicrystalline framework of anatase and rutile is probed for the degradation of benzene under solar light with/without applied bias. The enhanced activity is attributed to the transfer of electrons from the rutile to electron trapping/ lattice trapping sites of anatase and also to the impurity level created by the dopant which favours effective charge separation. The shallow detrapping nature of Mn2+ dopant additionally contributes to the overall enhancement in the photocatalytic activity especially in the presence of applied electric field.