A three-dimensional metal–organic framework for selective sensing of nitroaromatic compounds

A 3D metal–organic framework [NH2(CH3)2][Cd6(L)4(DMF)6(HCOO)](DMF = N,N-dimethylformamide) (1) has been synthesized using a tripodal ligand H3L (2,4,6-tris[1-(3-carboxylphenoxy)ylmethyl]mesitylene). The obtained complex exhibits a 3D framework containing hexanuclear {Cd6} building units formed by two trinuclear {Cd3} clusters that are connected via HCOO− anions. For complex 1, the participation of the fluorescent ligand H3L not only gives rise to a strong photoluminescence emission as expected, but more interestingly, that ligand originated characteristic band could be quenched selectively by nitrobenzene with a low detection limit, showing its potential as a highly sensitive and selective sensor for nitrobenzene. Based on an electron transfer quenching mechanism, the fluorescence sensing ability of 1 is also applicable for other electron-deficient nitroaromatic compounds with high selectivity and sensitivity, i.e., 1,4-dinitrobenzene, 1,3-dinitrobenzene, 2,4-dinitrotoluene, and 4-nitrotoluene, suggesting 1 a promising fluorescence sensor for detecting and recognizing the same kind of chemicals