Design of a pillar-layered metal-organic framework as high-performance fluorescence sensor for nitroaromatic compounds

Abstract A ternary luminescent cadmium-triazolate-carboxylate framework, [(CH3)2NH2][Cd(1245-BTC)0.5(3S-TRZ)] (SNNU-111, 1245-BTC ​= ​1245-benzenetetra- carboxylic acid, 3S-TRZ ​= ​3-mercaptotriazole) was successfully designed in this work. X-ray single crystal diffraction results show that Cd atoms are connected by 3S-TRZ ligands to form 2D wave-like layers, which are further extended by 1245-BTC linkers to generate the 3D pillar-layered architecture of SNNU-111. Solid-state and solution photoluminescence both showed that the emissions of SNNU-111 was ascribed to the intraligand charge transfer in 1245-BTC. Benefited from this process, SNNU-111 MOF can act as excellent fluorescence sensor to quantitatively detect involved nitroaromatics including nitrobenzene (NB), 1,2-dinitrobenzene (1,2-DNB), 1,3-dinitrobenzene (1,3-DNB), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and 2,4,6-trinitrophenol (PA) through the fluorescence quenching. The corresponding quenching coefficient (Ksv) values are of 1.0 ​× ​104-1.7 ​× ​104 ​M−1, which surpass the performance of many reported sensors. Specially, the Ksv value of 1.2 ​× ​104 ​M−1 for NB is nearly the highest one among all MOF sensors up to now. On the other hand, SNNU-111 sensor also exhibits good sensitivity to nitroaromatics with the detection limits as low as 1.61–5.77 ​ppm. Overall, the definite pillar-layered structure, fast response and high sensitivity make SNNU-111 a promising fluorescent sensor to detect nitroaromatic compounds.