Highly Selective Bifunctional Luminescent Sensor toward Nitrobenzene and Cu2+ Ion Based on Microporous Metal–Organic Frameworks: Synthesis, Structures, and Properties

Two metal–organic frameworks (MOFs), namely, [Ni­(DTP)­(H2O)]n (I) and [Cd2(DTP)2(bibp)1.5]n (II) (H2DPT = 4′-(4-(3,5-dicarboxylphenoxy) phenyl)-4,2′:6′,4″-terpyridine; bibp = 1,3-di­(1H-imidazol-1-yl)­propane), that present structural diversity were solvothermally prepared. Single-crystal X-ray diffraction analysis indicates that they consist of {NiN2O4} building units (for I) and {CdO4N2} and {CdO3N3} building units (for II), which are further linked by multicarboxylate H2DPT to construct microporous three-dimensional frameworks. The remarkable character of these frameworks is that coordination polymer II demonstrates highly selective and sensitive bifunctional luminescent sensor toward nitrobenzene and Cu2+ ion. The fluorescence quenching mechanism of II caused by nitrobenzene is ascribed to electron transfer from electron-rich (II) to electron-deficient nitrobenzene. The result was also evidenced by the density functional theory. Furthermore, anti-ferromagnetic as well as electrochemical characters of Ni-MOF (I) were also investigated in this paper.