Luminescent Li-Based Metal–Organic Framework Tailored for the Selective Detection of Explosive Nitroaromatic Compounds: Direct Observation of Interaction Sites

A luminescent lithium metal–organic framework (MOF) is constructed from the solvothermal reaction of Li⁺ and a well-designed organic ligand, bis­(4-carboxyphenyl)-<i>N</i>-methylamine (H₂CPMA). A Li-based MOF can detect an explosive aromatic compound containing nitro groups as an explosophore, by showing a dramatic color change with concurrent luminescence quenching in the solid state. The detection sites are proven directly through single-crystal-to-single-crystal transformations, which show strong interactions between the aromatic rings of the electron-rich CPMA^2– molecules and the electron-deficient nitrobenzene