In this work, a new series of coordination polymers (CPs) 1–8 were designed and successfully synthesized; they displayed typical afterglow at room temperature under ambient conditions. In 1–4, single green phosphorescence was observed, where the T₂ (π, π*) state was stabilized by the π-stacking interactions of the phosphorescent group tynca⁻, which contributed to enhancing their luminescence lifetimes. In contrast, when the π-stacking interaction of the phosphorescent group tynca⁻ was absent in the rigid matrix, 5–8 exhibited an intriguing time-resolved afterglow modulation, in which yellow [T₁ (n, π*), short lifetime] and green [T₂ (π, π*), long lifetime] phosphorescences were sequentially observed during the decay process when the common UV light was turned off. As one of the representatives of long-lived dual phosphorescent CPs, the promising optical properties of 8 allowed it to be used in logos for advanced anti-counterfeiting systems. To the best of our knowledge, this special and rare afterglow modulation has not been reported in the literature for persistent RTP (p-RTP) CP systems, and further exploration in this area may open a new door for newly emerging technologies such as optical recording and encryption or multimodal bio-imaging.

Organic solid-state materials with p-RTP (persistent room-temperature phosphorescence) properties have made infusive achievements. However, research on metal–organic hybrids with p-RTP is limited, of which dual phosphorescent ones are relatively rare. Herein, three light-emitting compounds Himpc·HNO₃ (Himpc-HNO₃), Cd(impc)₂(H₂O)₂ (Cd-impc) and [Zn(impc)₂(H₂O)₄]·2H₂O·(Zn-impc) were deliberately synthesized, based on Himpc [5-(1H-1,2,4-imidazol-1-yl)nicotinic acid] phosphor via a solvothermal method, and all displayed different room-temperature phosphorescence performances. It is noteworthy to mention that time-resolved color-changing afterglow phenomenon, which arises from different triplet states, was evidently observed in both Cd-impc and Zn-impc. Particularly, Zn-impc is a rare example of a metal–organic hybrid material showing novel color-changing afterglow performance [yellow light (∼580 nm, 84 ms) and green light (∼504 nm, 405 ms)], which can be utilized in special security systems. By means of single-crystal structural comparison, we revealed that a well-organized molecular arrangement is responsible for the enhancement of emission. Moreover, strong π⋯π interactions in H-aggregated molecules prominently increase the phosphorescence lifetime.