RESUMO
Porous organic frameworks possessing interactive free sites in the pore have attracted much attention due to their potential to show the site-originated specific functionalities. Herein, we demonstrate that such a framework could be constructed using a concept of geometrically mismatched frameworks composed of phenanthroline-based tetratopic carboxylic acid CP-Phen. Simple recrystallization of CP-Phen yielded a solvent included porous framework CP-Phen-1, in which three of four carboxy groups form hydrogen-bonded dimer to form a ladder-shaped framework, while the remained one does not participate in framework formation due to geometrical mismatch and interacts with solvent molecules through weak hydrogen-bonding. This result implies that our proposed strategy is effective to provide free interactive sites in porous frameworks. Although CP-Phen-1 undergoes two-step structural transformation presumably accompanied by hydrogen-bond rearrangements upon loss of solvent molecules, the activate framework shows good thermal stability up to 360 °C and selective CO2 adsorption.
Assuntos
Ácidos Carboxílicos , Hidrogênio , Adsorção , Ácidos Carboxílicos/química , Hidrogênio/química , Ligação de Hidrogênio , SolventesRESUMO
Four isomorphic two-dimensional (2D) homo- and heterometallic coordination polymers (CPs), [(Cd xMn1- x)3(HEBTC)2(DMSO)6] with x = 1 (1), 1/3 (2), 0.5 (3), and 2/3 (4) were prepared by conventional one-pot self-assembly approach, using Cd2+ or mixtures of Cd2+ and Mn2+ with 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylic (H4EBTC) under solvothermal conditions. The crystal structures of four isomorphic CPs are composed of center-symmetric trinuclear metal clusters building units linked by HEBTC3- ligands, extending into (3, 6)-connected topological 2D nets. Four CPs are isomorphic to the Mn-CP, [Mn3(HEBTC)2(DMSO)6], we recently reported. The solid-state photoluminescence of 1-4 shows dual emissions at ambient condition, where the emission bands centered at ca. 390 and 562 nm in 1 are assigned to the fluorescence and phosphorescence within HEBTC3- ligand, respectively; however, the emission bands centered at around 397 and 470 nm in 2-4 are attributed to fluorescence, corresponding to electron transition within HEBTC3- ligand and MLCT transition between HEBTC3- ligand and Mn2+ ion. In addition, the origin of isomorphism between 1 and Mn-CP is also discussed.
RESUMO
Solvothermal reactions of aromatic 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylic acid (H4EBTC) and Mg2+ salts in the presence of different supporting ligands afforded the coordination polymers [Mg(H2EBTC)(DMF)2(H2O)2] (1), [Mg3(HEBTC)2(H2O)4]·solvent (2) and [Mg2(EBTC)(H2O)5]·solvent (3). The crystal structures of 1-3 were determined by the single crystal X-ray diffraction technique, where CP 1 showed a one-dimensional zigzag MgO6 coordination octahedral chain structure; 2 exhibited a two-dimensional MgO6 coordination octahedral framework with trinuclear [Mg3(COO)6] SBUs, and 3 featured a three-dimensional MgO6 coordination octahedral framework with binuclear [Mg2O(COO)2] SBUs. The various structures in CPs 1-3 of Mg2+ ions with the H4EBTC ligand were ascribed to the conformational flexibility and the coordination mode diversity of the H4EBTC ligand. Interestingly, the zwitterionic supporting ligand 2-aminoterephthalic acid or 4-aminobenzenesulphonic acid played a vital role in the initial formation process of nuclear crystals but only as a structural induction agent, which modulated the dimensionality of these Mg2+-based CPs. Additionally, the three CPs emitted bright blue luminescence at ambient conditions, and the emission lifetimes and absolute quantum yields were also investigated.
RESUMO
In this study, a new two-dimensional Pb2+-based coordination polymer (CP), [Pb2(EBTC)(DMSO)3] (1), where H4EBTC is 1,1'-ethynebenzene 3,3',5,5'-tetracarboxylic acid, was synthesized under solvothermal conditions. Structural analysis reveals that 1 crystallizes in the monoclinic space group C2/m, where two crystallographically different Pb2+ ions show a coordination geometry of bicapped trigonal prisms that are connected to a double-chain by the EBTC4- ligands through carboxylate groups along the b-axis direction, and where successive double chains are held together to form a 2D layer via the Pb1 and Pb2 bicapped trigonal prisms sharing one edge or a triangle face along the c-axis direction. Interestingly, CP 1 emitted intense and long-lived greenish phosphorescence in the solid state at ambient conditions, with a quantum yield of 1.5% and a phosphorescence lifetime of 4.17 ms, and the emission mainly arose from the electron transition within the π-type orbitals of the EBTC4- ligand. The emission bands assignment and photophysical process were further discussed according to the calculation of both the electronic band structures and density of states. This study gives a fresh impetus to achieve coordination polymer-based long-lived phosphorescence materials under ambient conditions.
RESUMO
A two-dimensional coordination polymer, [Mn3(HEBTC)2(DMSO)6] (1), has been achieved by a solvothermal reaction of Mn2+ with 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylic acid (H4EBTC). The layer of a coordination polymer is composed of trinuclear Mn2+ clusters linked by HEBTC3- ligands to form a (3,6)-connected topological net. CP 1 with paramagnetic Mn2+ ions shows dual emissions centered at 397 and 468 nm in the solid state under ambient conditions with respectable quantum yields of 15.3% (397 nm) and 12.3% (468 nm). The dual emissions arise from n â π* transition in HEBTC3- and MLCT between HEBTC3- and Mn2+ centers.