Synthesis and Preparation of Ultralong Room-Temperature Phosphorescence Compounds Based on Pure p-Methoxybenzoic Acid Excluding Trace Impurities

Purely persistent room-temperature phosphorescence (p-RTP) materials have attracted a great deal of attention due to their extensive applications. However, trace impurities, which are formed in synthesis, may cause an unpredictable effect on the luminescence properties. In this work, we have carefully separated and purified the organic compounds to eliminate the effects of trace impurities on luminescence, and have managed to obtain three fascinating afterglow materials, (p-mba)_n (PMBA), {[Ca(p-mba)₂(H₂O)]}_n (Ca-PMBA), and [Sr(p-mba)₂(H₂O)]_n (Sr-PMBA), based on the pure p-methoxybenzoic acid (p-mba). It is found that the resulting PMBA can produce a long-lived and efficient afterglow, with τ_afterglow and Φ_afterglow reaching up to 1.08 s and 27.94%, respectively, demonstrating high performance in the field of organic phosphorescence. Additionally, Ca-PMBA and Sr-PMBA are two rare examples showing green long-afterglow of 0.95 s (Φ_Phos = 4.44%) and 0.53 s (Φ_Phos = 9.72%), respectively, and these materials rank first and third among alkaline-earth (AE) metal-based MOFs. Inspired by these distinctive properties, the potential applications for anticounterfeiting and information encryption have been explored through the utilization of these compounds. Moreover, our results clearly demonstrate that trace impurities had no remarkable effect on the phosphorescence properties of the above-mentioned compounds, which is different from previous reports, and more research data need to be accumulated and analyzed to further investigate the effect of trace impurities on phosphorescent properties.