Photochemical reactions are significantly affected by the electronic configuration of materials when exposed to light irradiation. This study employs rapid density functional theory (DFT) calculations, as implemented in the deMon2k package, to investigate photoinduced charge transfer in functionalized carbon-based materials. An analysis of frontier molecular orbitals, HOMO–LUMO energy gaps, and charge density distributions is conducted to elucidate light-induced electron excitation and reactivity. The findings indicate that basic molecular functionalization can efficiently adjust the electronic response during photoexcitation. The deMon2k method's efficiency enables rapid calculations at a minimal computational expense, rendering this approach appropriate for the swift screening of photoactive materials. This study demonstrates that rapid simulations can provide reliable photochemical insights and facilitate the development of experimental and industrial materials. Moreover, the computational workflow is deliberately simplified by employing established exchange–correlation functionals and compact basis sets accessible in deMon2k. This facilitates the rapid completion of geometry optimization and electronic structure analysis using standard computing resources. This expedited simulation approach is especially advantageous for initial material selection, where numerous candidate systems require efficient evaluation. This methodology can be readily expanded to investigate light–matter interactions pertinent to photocatalysis, chemical sensing, and environmental remediation, thereby underscoring the practical significance of rapid theoretical photochemistry.