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)-N-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.