Syntheses, crystal structures and photoluminescence properties of five Cd/Zn–organic frameworks

Abstract

Luminescent metal–organic frameworks (MOFs) have displayed extensively potential applications for photocatalysis, photoluminescence, electroluminescence, chemical sensors et al. Herein, five new Cd/Zn−organic frameworks of [Cd(HL)C2H5OH] (1), [Cd(HL)(2,2′-Bpy)H2O] (2), [Cd2(HL)2(Phen)2] (3), [Zn(HL)BIMB] (4), [Cd3(HL)3(4,4′-Bpy)DMF]·(H2O) (5) have been deliberately constructed via solvothermal reactions of d10 transition metal salts, i.e. Cd(NO3)2∙4H2O or Zn(NO3)2·6H2O, and a V-shaped semi-rigid organic linker of 4,4'-(hydroxymethanediyl) dibenzoic acid (H3L) along with the auxiliary poly-nitrogen ligands of 2,2′-Bpy(2,2′-bipyridine), Phen(phenanthroline), BIMB(1,1′-benzene-1,4-diyldimethanediyl-bis-1H-imidazole) and 4,4′-Bpy(4,4′-bipyridine). The crystal structures of compounds 1–5 were precisely determined by single-crystal X-ray diffraction (SC-XRD), Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and Thermogravimetic analysis (TGA). As revealed by SC-XRD, the isolated 1 presents a 2-periodic framework encompassing side-by-side channel-typed helical tubes. Compounds 2–4 display Z-shaped 1-periodic single chains, concomitant with twin chains and tubular structure, respectively. Interestingly, compound 5 demonstrates a two-fold interpenetrated 3-periodic skeleton in the presence of a rigid pillar of 4,4′-Bpy. Additionally, photoluminescence properties of 1–5 were lastly investigated.