The incorporation of the flavin derivative 8‐(dimethylamino)‐10‐methylisoalloxazine (DAMI) into the Al‐based metal‐organic frameworks (MOFs) DUT‐4, DUT‐5, and MIL‐53 by a postsynthetic method was investigated. DAMI shows no fluorescence in the neat solid state, only in solution and when incorporated into a MOF as “solid solution.” The fluorescence of the DAMI@MOF composites responded sensitively to the adsorption of guest molecules. Compounds containing methyl groups or chlorine enhanced the fluorescence intensity, whereas nitro compounds (nitrobenzene, 4‐nitrotoluene, 4‐nitrophenol) quenched the fluorescence. This behavior is attributed to the energy alignment between dye and guest orbitals, which enables photoinduced electron transfer (PET) from excited DAMI to electron‐withdrawing nitro compounds, resulting in fluorescence quenching, whereas excited electron‐donating guests yield PET to DAMI and lead to fluorescence enhancement. Among the tested compounds, nitrobenzene quenched 99% of the fluorescence of solid DAMI@MOF under a saturated‐air atmosphere at 25°C, corresponding to a vapor phase concentration of approximately 14 µg/L generated from a 0.1 mg/mL nitrobenzene solution.
Vollrath et al. (Sun,) studied this question.