Used as a key intermediate in the synthesis of conjugated organic semiconductors and porous organic frameworks. Its four aldehyde groups enable extensive Schiff base reactions, making it ideal for constructing covalent organic frameworks (COFs) with high surface area and ordered structures. Commonly applied in optoelectronic devices, including organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs), due to its rigid spirobifluorene core that enhances thermal stability and prevents aggregation. Also employed in sensor materials for detecting explosives or volatile organic compounds thanks to its fluorescence quenching properties.