Dual-Phase High-Emission Fan-Shaped Donor–Acceptor Molecules for Multiple-Scenario VOC Sensing

Donor–acceptor fluorophores often suffer from low luminescent efficiency in either solution or solid states due to nonradiative decay and aggregation-caused quenching. This study reports the rational design of two novel fan-shaped fluorophores ( 1 and 2 ) that achieve ultrahigh photoluminescence in both phases (Φ DIO = 0.99 and Φ solid = 0.92). This dual-state emission is enabled by a strategic structure incorporating bulky carbazole/triphenylamine branches. These groups effectively restrict intramolecular motion in solution to suppress energy loss, while their steric hindrance prevents detrimental π–π stacking in aggregates, conferring distinct aggregation-induced emission characteristics. The compounds exhibit pronounced intramolecular charge transfer, enabling solvent polarity sensing and visual gasoline grade discrimination. Furthermore, self-assembled aggregates of molecule 2 function as an exceptional fluorescent sensor for benzene derivative vapors, demonstrating high sensitivity (detection limits down to 84 ppb for benzene), a rapid response (∼2.44 s), and excellent selectivity. This work provides a viable molecular design strategy for high-performance dual-phase emissive materials with significant potential in environmental sensing.