Chemoselective C–C bond cleavage remains a challenge for the degradation of polymers because of the relatively high bond dissociation energy of C–C σ-bonds at room temperature. Organic molecular-based dye-sensitized photoelectrochemical cells (DSPECs) could offer a means of using renewable solar energy to drive energetically demanding chemoselective C–C bond cleavage reaction. This study reports the solar light-driven activation of a bicyclic aminoxyl mediator to achieve C–C bond cleavage in the aryl-ether linkage of a lignin model compound (LMC) at room temperature using a donor–π-conjugated bridge–acceptor (D–π–A) organic dye-based DSPEC system. The 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (DPTC) D–π–A organic dye was investigated along with a bicyclic aminoxyl radical mediator (9-azabicyclo[3,3,1]nonan-3-one-9-oxyl, KABNO) in solution and at the interface of a mesoporous structured TiO2 substrate in the presence of LMC. Photophysical studies of DPTC with KABNO were carried out to show intermolecular energy/electron transfer under 1 sun illumination (100 mW·cm− 2). The D–π–A type DPTC sensitized mesoporous TiO2 photoanode in the presence of KABNO can facilitate the generation of the reactive oxoammonium species KABNO+ as a strong oxidizing agent, which plays an important role in the photocatalytic oxidative C–C bond cleavage of LMC. The photoelectrochemical oxidative reaction in a complete DSPEC with KABNO afforded the chemoselective C–C bond cleavage products 2-(2-methoxyphenoxy)acrylaldehyde (94%) and 2,6-dimethoxy-1,4-benzoquinone (66%). This process provides a first report utilizing a D–π–A type organic dye in combination with a bicyclic nitroxyl radical mediator for heterogeneous photoelectrolytic oxidative cleavage of C–C σ-bonds, modeled on those found in lignin, at room temperature.