Highly polar solvents are generally considered to significantly quench the luminous emission of rare-earth doping luminescence materials. In this work, we reported a counterintuitive luminescence phenomenon in Dy/Eu@Gd-MOFs. Their photoluminescence (PL) behaviors in propanol/butanol isomers exhibit trends of emission intensity that inversely correlate with solvent polarity. This phenomenon should not be simplistically ascribed to quenching induced solely by reabsorption, solvent effects, or high-frequency vibrational groups. The structural differences among propanol and butanol isomers result in diversified high-frequency and fingerprint-region vibrational modes. When these vibrations resonate with the critical energy gap, they nonradiative decay in the sensitizer through vibrational coupling, thereby steering energy toward the activator. Time-resolved spectra acquired at different temperatures provide a detailed analysis and evidence for this opinion. These findings give an unconventional interpretation for solvent-induced luminescence quenching in rare-earth luminescence materials, enabling a novel route for modulating their excited states through solvent engineering.
Fan et al. (Sun,) studied this question.