Viologen-based Ln-MOF material with photochromicity and photoluminescence for anticounterfeiting.

Viologen-based photochromic materials with photochromicity and photoluminescence have great advantages in anti-counterfeiting applications. Two novel viologen-based multifunctional Ln-MOFs Eu₂Cl(m-bpybdc)L₂(NO₃)₂·(H₂O)₅ (1) and Tb₂Cl(m-bpybdc)L₂(NO₃)₂·(H₂O)₆ (2) (m-bpybdc = 1,1′-bis(3-carboxyphenyl)-4,4′-bipyridinium and H₂L = isophthalic acid) with three-dimensional structures were synthesized solvothermally. Both compounds exhibited reversible discoloration in response to external light and electrical stimulation. Notably, compound 1 presented strong fluorescence under ultraviolet light, showing the characteristic red emission of Eu³⁺. We further explored the application of these compounds in the field of anti-counterfeiting. These results provide useful data on the structure, luminescence, and light response of viologen-based lanthanide coordination polymers for their effective application. [ABSTRACT FROM AUTHOR]