Used primarily in organic synthesis and materials science, 9-Ethynylphenanthrene serves as a building block for creating complex organic molecules. Its ethynyl group enables it to participate in click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), making it valuable in the development of polymers and advanced materials. It is also explored in the design of organic semiconductors due to its conjugated structure, which can enhance electronic properties. Additionally, it finds applications in the study of photophysical processes and as a precursor in the synthesis of fluorescent dyes and probes for biological imaging.