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.本文报道了两种具有结构多样性的金属有机框架(metal–organic frameworks, MOFs)，分别为[Ni(DTP)(H₂O)]ₙ (I)与[Cd₂(DTP)₂(bibp)₁.₅]ₙ (II)，其中配体H₂DPT为4′-(4-(3,5-二羧基苯氧基)苯基)-4,2′:6′,4″-三联吡啶，bibp为1,3-二(1H-咪唑-1-基)丙烷，二者均经由溶剂热法合成。单晶X射线衍射分析结果表明：配合物I由{NiN₂O₄}次级构筑单元构成，配合物II则包含{CdO₄N₂}与{CdO₃N₃}两种次级构筑单元；上述次级构筑单元进一步通过多羧酸配体H₂DPT桥联，构筑得到微孔三维框架结构。该类框架结构的显著特征为：配合物II可作为针对硝基苯与Cu²+离子的高选择性、高灵敏度双功能荧光传感器。配合物II因硝基苯引发的荧光猝灭机制，可归因于电子从富电子的配合物II转移至缺电子的硝基苯，该结论亦可通过密度泛函理论(density functional theory, DFT)验证。此外，本文还对Ni基MOF（配合物I）的反铁磁性与电化学性质展开了研究。