Rational synthesis, crystal structure, and sensing and adsorption properties of luminescent metal–organic frameworks
Five novel Cd(II) metal–organic frameworks (Cd-MOFs), namely [Cd6(L)4(1,3-bit)2(H2O)4]n (1), [Cd(HL)(4,4′-bbibp)]n (2), [Cd3(L)2(1,4-bimb)2(H2O)2]n (3), [Cd(HL)(4,4′-bidpe)]n (4) and [Cd3(L)2(1,1′-bbi)(H2O)4]n (5) (flexible H3L = 5-(2-carboxylphenoxy)isophthalic acid, rigid 1,3-bit = 1,3-bis(l-imidazoly)toluene, rigid 4,4′-bbibp = 4,4′-bis(benzoimidazo-1-ly)biphenyl, semi-flexible 1,4-bimb = 1,4-bis(imidazol-l-ylmethyl)benzene, semi-flexible 4,4′-bidpe = 4,4′-bis(imidazolyl)diphenyl ether, and flexible 1,1′-bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) were synthesized employing a rational design approach under solvothermal conditions and further characterized by elemental analysis, IR spectra, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. Diversity architectural topologies have been generated by adjusting the N-donor ligands. They exhibit varied structures: 1 displays an unprecedented 6-nodal (3,3,4,4,8,8)-c 3D topology framework with the point Schläfli symbol of (3·4·5)2(32·42·52·66·78·87·9)(32·63·7)(4·64·8)(410·611·87)(43)2; 2 shows a 2-fold interpenetrating 4-connected cds topology with the point Schläfli symbol of (65·8); 3 exhibits an unprecedented 2-nodal (3,8)-c 3D topology network with the point Schläfli symbol of (42·5)2(44·56·610·75·82·9); 4 shows a 4-connected sql topology with the point Schläfli symbol of (44·62); 5 displays a tfz-d topology 2-nodal (3,8)-c 3D network with the point Schläfli symbol of (43)2(46·618·84). The luminescence studies reveal that MOFs 1–5 display highly sensitive and selective fluorescence sensing towards Fe3+ cations, CrO42− anions and molecular acetone. Meanwhile, the targeted dye adsorption properties of MOFs 1–5 are investigated.