Jing-Bo Tan

Tubular metal-organic framework-based capillary gas chromatography column for separation of alkanes and aromatic positional isomers.

In this work, a tubular metal-organic framework, MOF-CJ3, with a large one-dimensional channel was chosen as stationary phase to prepare a capillary gas chromatographic column via a verified dynamic coating procedure. The column offered good separations of linear and branched alkanes, as well as aromatic positional isomers (ethylbenzene, xylene, cresol, hydroquinone, dichlorobenzene, bromobenzonitrile, chloronitrobenzene, and nitrotoluene) based on a combination of host-guest interactions and adsorption effects. Elution sequence of most of the analytes followed an increasing order of their boiling points, except for the separation of n-heptanes/isooctane, cresol, and hydroquinone isomers. Separation behavior of the column upon different organic substances may be related to the tubular pore structure of MOF-CJ3, in which the van der Waals forces between the alkanes and the hydrophobic inner surfaces might have great effect on separation of n-heptanes and isooctane, whereas the separation of cresol and hydroquinone isomers were affected by (OH⋯O) hydrogen bonds formed between the analytes and the 1,3,5-benzenetricarboxylate ligands on the pore wall. The effects of temperature on separation of aromatic positional isomers were investigated to elucidate entropy and enthalpy controlling of the separation process.

An unprecedented (3,4,14)-connected 3D metal–organic framework based on planar octanuclear lead(II) clusters as a secondary building unit

An unprecedented trinodal (3,4,14)-connected 3D metal–organic framework formed by planar octanuclear lead(II) clusters as 14-connected nodes and 2-(Pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate ligands as 3- and 4-connected nodes has been hydrothermally made. It provides a novel topological structure of metal–organic frameworks.

Anion-dependent assembly and solvent-mediated structural transformations of three Cd(II) coordination polymers based on 1H-imidazole-4-carboxylic acid

Three new Cd(II) coordination polymers with 1H-imidazole-4-carboxylic acid (Himc), [Cd(Himc)2(H2O)]n (1), [Cd(Himc)2]n (2) and [Cd2(Himc)2(SO4)(H2O)2]n (3) were perpared by solvothermal reactions and structurally characterized, which all comprised metal–negative ligand systems. Compound 1 exhibit a 1D zigzag chain; compound 2 features a 3D diamondoid work; while compound 3 possesses a 2D layer structure consisting of rhomboid grids. When 1 or 2 was left in a water/ethanolic solution of Na2SO4, their 1D or 3D framework was transformed into a 2D framework of 3. All compounds also displayed structure-related photoluminescent properties in the solid state.

Assembly of Cd(II) coordination polymers: structural variation, supramolecular isomers, and temperature/anion-induced solvent-mediated structural transformations

The reactions of Cd(II) salts and 5-(3-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (3-HIPT) resulted in eight new coordination polymers (CPs), namely, {[Cd(3-IPT)2(H2O)2]·H2O}n (1 and 2), {[Cd(3-IPT)2(H2O)2]·2H2O}n (3), [Cd(3-IPT)(H2O)Cl]n (4), [Cd(3-IPT)Cl]n (5), [Cd(3-HIPT)I2]n (6), [Cd(3-IPT)I]n (7), and [Cd(3-HIPT)2]n (8). Single-crystal X-ray analysis revealed that compound 1 is a 1D beaded chain, whereas compounds 2 and 3 are made of 2D networks. Compounds 1–3 are supramolecular isomers; their synthesis can be controlled under different temperatures and concentrations. The results showed that compounds 1 and 3 are the most thermodynamically and kinetically favored products, respectively. The thermodynamic stability of compound 1 may be attributed to the formation of the smallest M2L2 ring in the compound. Compounds 4–7 were obtained at higher Cl−/I− concentrations. Compound 4 is a 2D net composed of 1D [Cd(3-IPT)]n chains and μ2-Cl and μ2-H2O connectors. Compound 5 is a (3,6)-connected 3D framework with rtl topology. Compound 6 possesses a 1D chain with 3-HIPT ligands on both sides. Compound 7 is a 2D (4·82) net. Compound 8, a 3D pcu framework based on trinuclear linear SBUs, was formed when Cd(CF3CO2)2 was introduced at 170 °C. Based on a temperature-changing cycle, compounds 1 and 3 display crystal-to-amorphous-to-crystal phase transitions accompanying the dehydration–rehydration process, whereas compound 2 only displays crystal-to-amorphous phase transition when the temperature is increased and cannot go back to the crystal phase again. Interestingly, solvent-mediated structural transformations were accomplished among the selected compounds. When compounds 2, 3, 6, 7, or 8 were left in a water and NaCl solution at 170 °C, they were partly/fully transformed into compounds 1 and 5, respectively. When compound 5 was recrystallized in water at 120 and 170 °C, it was partly and fully transformed into compounds 2 and 1, respectively. Such transformations were induced by the temperature or an anion. In addition, the thermal stabilities and luminescence properties of selected compounds have also been studied in detail. The complexes exhibit intense solid-state fluorescence emission at room temperature.

An unprecedented supramolecular network with channels filled by 1D coordination polymer chains: Cocrystallization of Ag(I)-4,4′-bipyridine and Ag(I)-benzimidazole complexes

An unprecedented supramolecular network formed by [Ag(4,4′-bipyridine)]n chains and [Ag(NO3)4]3− anions via Ag⋯O interaction shows four types of channels filled by [Ag(4,4′-bipyridine)]n chains, [Ag(benzimidazole)]n chains and water molecules, representing the first example of cocrystallization of two 1D infinite coordination polymer chains.

Spontaneous resolution of a coordination polymer containing stereogenic five-coordinate Zn(II) centers and achiral ligands with axially chiral conformation

A pair of chiral coordination polymers, [Zn(HPyIDC)]n (1a and 1b, H3PyIDC = 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate), were assembled from an achiral precursor, H3PyIDC and Zn(II) ions via spontaneous resolution under solvothermal conditions. Crystal structure analysis showed that they are chiral three-dimensional (3D) coordination polymers based on the interconnection of six types of one-dimensional (1D) helical chains. They exhibit an intrinsic chiral (10,3)-a network. The chirality comes from both the stereogenic five-coordinate Zn(II) ions and the axially chiral ligands. Solid-state circular dichroism (CD) spectra measurements confirmed the occurrence of spontaneous resolution of [Zn(HPyIDC)]n and demonstrated that the resulting crystal of [Zn(HPyIDC)]n is a racemic mixture. Compound 1 showed strong fluorescence emission at room temperature.

Construction of six new luminescent Ln(III)–Zn(II) heterometallic coordination polymers based on heterometallic secondary building units

Six new d–f heterometallic Ln(III)–Zn(II) coordination polymers (CPs), namely, {[EuZn(NIPH)1.5(INC)(H2O)(OH)]·0.5H2O}n (1), [LnZn(NIPH)2(INC)(H2O)]n [Ln = Eu (2), Tb (3)], [EuZn2(NIPH)2.5(INC)2]n (4) and [LnZn(NIPH)2(NC)(H2O)]n [Ln = Eu (5), Tb (6)] [H2NIPH = 5-nitroisophthalate, HINC = isonicotinate, and HNC = nicotinate], were obtained under hydrothermal conditions. All the compounds are based on well-defined heterometallic secondary building units (SBUs). Compound 1 is a 3D network with pcu topology, which was generated from tetragonal tetranuclear heterometallic [Eu2Zn2(NIPH)4(INC)2(OH)2] SBUs connected by NIPH2− and INC− ligands. Compounds 2 and 3 are isostructural and exhibit 3D heterometallic frameworks with bcu topology constructed by the linkage of 2D layers containing linear tetranuclear heterometallic [Eu2Zn2(NIPH)6(INC)2] SBUs and INC− anions. Compound 4 possesses 7-connected 3D frameworks with the Schlafli symbol of (33·411·56·6) constructed by the interconnection of linear trinuclear heterometallic [EuZn2(NIPH)4(INC)4] SBUs, NIPH2− ligands and INC− anions. In compounds 5 and 6, 3D networks are formed through the linkage among linear tetranuclear [Ln2Zn2(NIPH)8(NC)2] SBUs, NIPH2− ligands and NC− anions. All the compounds represent examples of 3D lanthanide–transition heterometallic–organic coordination polymers with two types of metal ions and two organic carboxylates. Furthermore, their solid-state fluorescence properties have been investigated at room temperature.