employed phenanthridine to extend the conjugation of the COT core , where the three-arm structure with a benzene core exhibited a highly rigid, planar 2D structure, leading to ACQ behavior, whereas the four-arm structures (17) displayed significant AIE effects due to the tub-to-tub inversion of the flexible COT core. Based on extensive work, Wang's group proposed four molecular design methods to enhance the luminescence of COTh core derivatives: branching, aromatization, introduction of heterocycles, and thiophene sulfonation. Due to its exceptional functional properties, the COTh core has been applied in various specialized material designs, including microbial imaging , fluorescence probes suitable for diverse microenvironments , and responsive stimuli gels .