Synthesizing a luminescent copper metal-organic framework and utilizing it for the fluorescent detection and discrimination of ethanol and methanol.

A crystalline two-dimensional (2D) network structure of a thermally stable luminescent copper metal-organic framework (Cu-PA) was synthesized by a liquid diffusion method and utilized for alcohol sensing. A single crystal of the Cu-PA coordination polymer network was obtained by layering an acetonitrile solution of copper iodide onto a solution of 4-picolylamine (PA) in an acetonitrile-dichloromethane mixture. Solid-state structural analysis showed a 2D network structure via bidentate coordination of a 4-picolylamine ligand and bridged coordination of iodide. BET analysis revealed that Cu-PA has a surface area of 10.077 m2 g-1 and a pore diameter of 1.38 nm, indicating that Cu-PA possesses well-defined porosity. Cu-PA exhibited strong solid-state fluorescence at 540 nm, resulting from the ligand-to-metal charge transfer (LMCT) phenomenon. Notably, when immersed in methanol and ethanol at pH 8.20, Cu-PA displayed distinct fluorescence, enabling clear differentiation between the two alcohols. This finding suggests its potential use as a fluorescence sensor for the selective detection and differentiation of environmentally significant volatile organic compounds (VOCs), specifically methanol and ethanol.