4-Formylphthalonitrile is primarily used as a key intermediate in the synthesis of phthalocyanine dyes and pigments. These dyes are widely applied in the textile industry for coloring fabrics due to their excellent stability and vibrant colors. Additionally, it plays a crucial role in the production of organic semiconductors, which are utilized in electronic devices such as solar cells, transistors, and light-emitting diodes (LEDs). Its application extends to the field of photodynamic therapy, where it is used to create photosensitizers for cancer treatment. The compound's reactivity also makes it valuable in organic synthesis for constructing complex molecules in pharmaceutical research.