The low energy CT band in the absorption spectra of both 2CzPN and 4CzIPN is significantly blue-shifted after irradiation, consistent with photosubstitution studies previously reported by us and others. In particular, the work of Kwon et al. revealed that one of the cyano groups can be substituted by an alkyl group when the cyanoarene-based PCs are irradiated in the presence of DIPEA; in the case of 4CzIPN, the nitrile was photosubstituted by an ethyl group as the major product, and a methyl group as the minor product. Although 4CzIPN is observed to photodegrade similarly in all four solvents, the absorption spectra of 2CzPN are considerably less changed in THF relative to DCM, DMF, and MeCN. This observation is consistent with 2CzPN achieving a higher yield in THF of 31% compared to the 2-11% yield in the other solvents, implying that the photodegradation occurring in the other solvents inhibits the photocatalysis, likely due to the poorer spectral overlap with the 456 nm excitation source.