Covalent Engineering of Polyamide-6/COFs-2DPA Composites for High-Strength Room-Temperature Phosphorescence and Dual-Mode Applications

Room-temperature phosphorescent (RTP) materials have garnered significant interest for their versatile applications in optoelectronics, sensing, and information security. Polymer-based RTP composites, integrating the mechanical robustness of polymers with the unique photophysical characteristics of RTP materials, are particularly promising. However, achieving a balance among high mechanical strength, processability, and efficient RTP performance remains challenging. Herein, we developed a polyamide-6 (PA6) composite embedded with two-dimensional covalent organic framework analogues (COFs-2DPA) through in situ polymerization. COFs-2DPA, synthesized via melamine-terephthaloyl chloride condensation, features a π-conjugated architecture with amide-rich linkages, ensuring compatibility with PA6 and suppressing nonradiative decay. The resulting PA6/COFs-2DPA composites exhibit exceptional mechanical and RTP properties, including a Young’s modulus of 2.06 GPa, a phosphorescence lifetime of 612 ms, and a high quantum yield of 33.4%. Tunable fluorescence-to-phosphorescence spectral shifts with varying COFs-2DPA content enable dual-mode information encryption via binary, Morse coding and time-dependent screen printing with different RTP after glows of different components. Furthermore, the composite demonstrates humidity-responsive afterglow decay, with duration inversely proportional to environmental moisture, highlighting its potential as a reusable sensing platform. This study provides valuable insights for the development of high-performance polymer-based RTP composites for advanced applications in anticounterfeiting, environmental monitoring, and smart optoelectronics.