A Cu2I2 cluster bearing MOF as a fluorescence-sensing material for the visual detection of methanol

Abstract

Due to their wide applications with regard to health and safety, sensitive and selective detection and distinguishing of alcohol molecules (e.g., methanol in counterfeit wine) is very important. Fluorescence (FL)-sensing materials towards probing alcohol molecules have been extensively developed based on their advantages of economy, convenience, and rapid detection. Herein, a fluorescent metal–organic framework (FL MOF) Cu₂I₂(pdc)₄Sr₄(DMF)₆ (Sr-CuI-MOF, H₂pdc = 3,5-pyridinedicarboxylic acid) featuring a three-dimensional (3D) structure was characterized. Sr-CuI-MOF exhibited a thermally activated delayed fluorescence arising from the Cu₂I₂-pdc motif. Upon exposure to methanol, Sr-CuI-MOF showed a sensitive and selective fluorescence redshift, characterized by a pronounced solvatochromism. Consequently, Sr-CuI-MOF could be used to accurately detect methanol by analyzing the linear relationship between the shift in emission wavelength or percentage of the fluorescence intensity quenching and methanol concentration. It represents the first CuI-bearing MOF with fluorescence detection of methanol. This work presents a novel approach to design FL-sensing MOFs that can be seen by the naked eye utilizing CuI-ligand motifs as building blocks and emission centers.