ABSTRACT
By using an asymmetrical rigid pentacarboxylic acid ligand, 2,4-di(3',5'-dicarboxylphenyl)benzoic acid (H5L), four new three-dimensional (3D) metal-organic frameworks (MOFs), namely {[Cu2(HL)(H2O)2]·2DMF·2H2O}n (1), {[Co2(L)(DMA)]·H2N(Me)2}n (2), {[Co2(L)(H2O)]·H2N(Me)2}n (3), {[Mn2(L)(DMF)(H2O)]·H2N(Me)2}n (4), were solvothermally synthesized. H5L in 1-4 shows different coordination modes and can easily form various metal clusters (secondary building units, SBUs) in the final structures. 1 is a 3D porous framework with a (4,4)-connected pts topology based on the [Cu2(COO)4] paddlewheel SBU, wherein six SBUs are connected by twelve HL4- to get an unprecedented Cu12 hendecahedron nanocage. 2-4 possess similar dinuclear [M2(COO)5] SBUs (M = Co, Mn), which are further extended by L5- to give rise to 3D frameworks with the uncommon (5,5)-connected nia-5,5-P21/c and bnn topologies. In addition, the desolvated framework of 1 contains polar channels decorated with uncoordinated carboxylate groups, leading to selective adsorption for CO2 over CH4 at 195, 273 and 298 K. Moreover, the magnetic properties of 1-4 show that there exist antiferromagnetic interactions between metal ions.
ABSTRACT
Four super water-stable isostructural lanthanide-organic frameworks, [Ln(HL)(H2O)2]n·2H2O (1-Ln) (Ln = Eu, Tb, Nd and Sm), have been successfully synthesized under hydrothermal conditions with 3,5-di(2,4-dicarboxylphenyl)pyridine (H4L) and Ln(NO3)3·6H2O. 1-Ln shows a novel 2D layered structure with uncoordinated carboxylic and pyridyl groups pointing to the interior of interlayer channels. The luminescent properties of 1-Eu in the solid state and one steeped in aqueous solution have been measured, which show excellent luminescence and good luminescent stability in water. Next 1-Eu was chosen as a probe for sensing different metal ions. Consequently, 1-Eu exhibits a highly selective response to Fe(3+) through the luminescence quenching effect in aqueous solutions. The probable mechanisms of the quenching effects have been investigated in detail.
ABSTRACT
A new 2D highly flexible and breathing porous framework [CuL(Me2NH)]·DMF·H2O () (H3L = 5-(4'-carboxylphenoxy)nicotinic acid) has been synthesized using a tritopic linker with a flexible joint. The desolvated framework, [CuL(Me2NH)] (), undergoes structural contraction, and exhibits selective and double-step hysteretic adsorption for CO2. Furthermore, on exposure to CH2Cl2 at room temperature, a unique single-crystal-to-single-crystal transformation occurred between and [Cu2L2(Me2NH)2(H2O)2]·5H2O ().
