Three Pbx(COO)y Cluster Frameworks Based on a Flexible Triazinetricarboxylic Acid Ligand: Syntheses, Structures, and Fluorescent Sensing Application for Nitrophenols

Three new metal–organic frameworks (MOFs), namely, [Pb7(TTPCA)4Cl2]·3H2O (1), [Pb7(TTPCA)4(DMA)2(HCOO)2]·H2O (2), and [Pb4(TTPCA)3]·3DMF·2H2O·H3O (3), were synthesized by the H3TTPCA ligand [H3TTPCA = 1,1′,1″-(1,3,5-triazine-2,4,6-triyl)-tripiperidine-4-carboxylic acid], with lead(II) nitrate under solvothermal conditions. They were characterized by CHN analysis, IR spectroscopy, UV–vis spectroscopy, and single-crystal and powder X-ray diffraction. In addition, their thermogravimetric analysis and fluorescence properties were studied. Compounds 1–3 were 3D MOF structures with different Pbx(COO)y clusters: ([Pb7(COO)12Cl2]), ([Pb7(COO)12]), and [Pb8(COO)18]. Fluorescence detection of compounds 1–3 shows that they can act as excellent sensors of nitrophenols with a low limit of detection and a high quenching constant.