Assemblies of metal–organic frameworks based on a tetrapodal linker for luminescence sensing of tetrahydrofuran

Abstract

The solvothermal assemblies of Zn(II)/Co(II)/Ni(II) ions and a rigid silicon-centered tetrahedral ligand, tetrakis(3-carboxyphenyl)silicon (H4L), yield five metal–organic frameworks, formulated as [Zn2(OH)(dib)0.5(HL)]·H2O·2DMF (1), Zn3(OH)2(phen)2(H2L)2 (2), [Co2(OH)(H2O)3(DMF)(HL)]·H2O·2DMF (3), [Co2(OH)(H2O)(phen)(DMF)(HL)]·H2O·DMF (4) and [Ni2(OH)(H2O)2(DMF)2(HL)]·H2O·DMF (5) [phen = 1,10-phenanthroline, dib = 1,4-di(1H-imidazol-1-yl)benzene, DMF = N,N-dimethylformamide]. Single crystal X-ray diffraction analyses reveal that 1 is a three-dimensional framework structure based on 5-connected [Zn2(OH)]3+ secondary building units (SBUs) and the silicon-centred tetrahedral ligands. 2 features a one-dimensional architecture constructed from trinuclear [Zn3(OH)2(phen)2]4+ SBUs and 2-connected tetracarboxylate ligands. The structures of 3–5 are similar, which all contain dinuclear metal-based SBUs linked by 4-connected silicon ligands, resulting in layered sql nets. The syntheses, structures, thermal stabilities and photoluminescence of these compounds are studied. Further luminescence studies reveal that 1 exhibits a high-sensitivity sensing response to tetrahydrofuran.