Eu3+ or Sm3+-Doped terbium-trimesic acid MOFs: Highly efficient energy transfer anhydrous luminophors

Abstract [Tb(TMA):RE3+] MOFs (MOF: Metal Organic Framework; TMA: trimesic acid or 1,3,5-benzenetricarboxylic acid, RE3+: Eu and Sm) with tunable color were synthesized by aqueous coprecipitation method. Using a chemical artifice, lanthanide cationic radius contraction, it was possible to obtain only anhydrous MOFs, a very important characteristic in luminescent compounds. TMA3− anions triplet states present higher energy levels compared to the main emitting states of Eu3+ (5D0), Tb3+ (5D4) and Sm3+ (4G5/2), supplying an efficient antenna effect. Based on the spectroscopic investigation, i.e. excitation/emission spectra and lifetimes of the excited states, the material shows a high quantum efficiency (η = 83–86%) due to the very efficient energy transfer process TMA→Tb→Eu, combined to the presence of this high energy absorption ligand and the absence of water molecules.