Jian-Bin Lin

Metal azolate frameworks: from crystal engineering to functional materials.

2.1.2. Low Topology/Framework Density 1003 2.1.3. Side Group Directed Superstructures 1003 2.2. Synthesis Considerations 1003 2.3. Special Properties 1004 3. Metal Imidazolate Frameworks 1004 3.1. Chains and Rings 1004 3.2. Zeolitic and Zeolite-like Frameworks 1006 3.2.1. SOD-Type Zinc(II) 2-Methylimidazolate 1007 3.3. Nonporous 4-Connected Networks 1010 3.4. Polyimidazolates 1011 4. Metal Pyrazolate Frameworks 1011 4.1. Clusters and Chains 1011 4.2. 3D Networks Based on Polypyrazolates 1012 5. Metal 1,2,4-Triazolate Frameworks 1014 5.1. Simple 3-Connected Networks 1015 5.2. Quasi-Imidazolates 1018 5.3. With Coordinative Substituents 1019 5.4. With Secondary Counterions and/or Ligands 1021 6. Metal 1,2,3-Triazolate Frameworks 1023 7. Metal Tetrazolate Frameworks 1025 7.1. Univalent Coinage-Metal Tetrazolate Frameworks 1025

Nonclassical Active Site for Enhanced Gas Sorption in Porous Coordination Polymer

Gas sorption experiments and grand canonical Monte Carlo simulations for two isostructural microporous metal azolate frameworks show that even partially exposed uncoordinated nitrogens can effectively increase gas binding affinity and overcome the pore size confinement effect.

Geometry analysis and systematic synthesis of highly porous isoreticular frameworks with a unique topology

Porous coordination polymers are well known for their easily tailored framework structures and corresponding properties. Although systematic modulations of pore sizes of binary prototypes have gained great success, simultaneous adjustment of both pore size and shape of ternary prototypes remains unexplored, owing to the difficulty in controlling the self-assembly of multiple molecular building blocks. Here we show that simple geometry analysis can be used to estimate the influence of the linker lengths and length ratios on the synthesis/construction difficulties and framework stabilities of a highly symmetric, ternary prototype composed of a typical trinuclear metal cluster and two types of bridging carboxylate ligands. As predicted, systematic syntheses with 5×5 ligand combinations produced 13 highly porous isoreticular frameworks, which show not only systematic adjustment of pore volumes (0.49–2.04 cm3 g−1) and sizes (7.8–13.0 Å; 5.2–12.0 Å; 7.4–17.4 Å), but also anisotropic modulation of the pore shapes.

A Porous Coordination Polymer Assembled from 8-Connected {CoII3(OH)} Clusters and Isonicotinate: Multiple Active Metal Sites, Apical Ligand Substitution, H2 Adsorption, and Magnetism

A microporous coordination polymer, namely, [Co(3)(ina)(4)(OH)(C(2)H(5)OH)(3)](NO(3))·C(2)H(5)OH·(H(2)O)(3) (1, or MCF-38, ina = isonicotinate), with 8-connected {Co(3)(OH)} clusters as the structural secondary building units, has been solvothermally synthesized. The hydroxo-centered Co(II) cluster involves multiple active metal sites. The interesting apical ligand substitutions have been directly observed, and the corresponding products of [Co(3)(ina)(4)(OH)(G)(x)(H(2)O)(n)](NO(3))·G·(H(2)O)(m) (1 ⊃ PrOH, G = PrOH, x = 2, n = 1, m = 3; 1 ⊃ BuOH, G = BuOH, x = 2, n = 1, m = 1, and 1 ⊃ MeOH, G = MeOH, x = 3, n = 0, m = 7) have also been obtained by solvothermal syntheses or crystal-to-crystal transformations. High-pressure H(2) adsorption measurement at 77 K reveals that activated 1 can absorb 2.2 wt % H(2) at 5 bar. The relative H(2) absorption at low pressure (86% of the storage capacity at 1 bar) is higher than the corresponding values reported for some typical porous coordination polymers. The magnetic studies of 1 show a dominant antiferromagnetic coupling between Co(II) ions of intra- and inter-cluster.

A flexible metal azolate framework with drastic luminescence response toward solvent vapors and carbon dioxide

1H-Imidazo[4,5-f][1,10]phenanthroline (Hip) can be deprotonated to bridge Zn(II) ions, giving a flexible porous metal azolate framework [Zn7(ip)12](OH)2 (MAF-34) which shows not only drastic structural and luminescent changes for different solvent vapors, but also strong adsorption and quantitative luminescence response for low-pressure CO2.

Isomeric Zinc(II) Triazolate Frameworks with 3-Connected Networks : Syntheses, Structures, and Sorption Properties

Two pairs of supramolecular isomers based on ternary zinc(II)/triazolate/X (triazolate = 3,5-dimethyl-1,2,4-triazolate (Hdmtz), X = HCOO(-), F(-)) metal azolate frameworks, namely, [Zn(dmtz)(HCOO)] x H(2)O (MAF-X3, 1a), [Zn(dmtz)(HCOO)] x (1/6Me(2)NH)(1/4H(2)O) (MAF-X4, 1b), [Zn(dmtz)F] (MAF-X5, 2a), and [Zn(dmtz)F] (MAF-X6, 2b), have been synthesized via variations of the reaction conditions. The 3-connected Zn(dmtz) networks in 1a, 1b, 2a, and 2b can be described as rarely observed 4.8(2), 4.12(2), (8,3)-b, and 8(2).10-a, respectively. Besides the mu(3)-dmtz, tetrahedral and trigonal-bipyramidal/square-pyramidal coordination of the Zn ions are accomplished by monodentate formate and mu-F, respectively. While 1a and 2b are nonporous structures, 1b and 2a exhibits 1D nanotubular hydrophilic (d 3.2 A) and hydrophobic (d 3.6 A) channels, respectively. Thermogravimetric analysis shows that the stabilities of 2a and 2b are much better than those of 1a and 1b, which may be ascribed to different coordination numbers of zinc atoms. Moreover, 1b and 2a with different pore properties show selective sorption behavior.

Porous manganese(II) 3-(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazolate frameworks: rational self-assembly, supramolecular isomerism, solid-state transformation, and sorption properties.

Reactions of 3-(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (Hdpt24) with Mn(OAc)(2) under different conditions give two mononuclear complexes, [Mn(dpt24)(2)(MeOH)(2)] (1) and [Mn(dpt24)(2)(H(2)O)(2)] x 6 H(2)O (2), and three isomeric two-dimensional (2D) coordination polymers alpha-[Mn(dpt24)(2)] (3a), beta-[Mn(dpt24)(2)] x g (3b x g, g = DMF and H(2)O), and gamma-[Mn(dpt24)(2)] x g (3c x g, g = toluene and MeOH). Their structures were characterized by single-crystal and powder X-ray diffractions. In these compounds, four coordination sites of each octahedrally coordinated Mn(II) ion are chelated by two dpt24 ligands in the trans and/or cis configurations. While the two remaining coordination sites are occupied by solvent molecules in 1 and 2, they are occupied by pyridyl nitrogens from neighboring Mn(dpt24)(2) units in 3, forming 4-connected 2D (4,4) networks. The Mn(II) ions in both 3a and 3b are uniquely chelated by dpt24 in the trans or cis configurations, respectively, but Mn(dpt24)(2) in 3c possesses both the trans and cis configurations. The packing fashions of these (4,4) layers in the three isomers of 3 are also different, in which 3a has a close packing structure, while 3b exhibits unique one-dimensional (1D) channels and 3c exhibits two distinct types of 1D channels. As revealed by powder X-ray diffractions, crystals of 1 and 2 can reversibly transform to each other when in contact with the corresponding solvent vapor (H(2)O/MeOH). The gas and vapor sorption studies for porous 3b revealed interesting sorption behaviors. Nitrogen adsorption for 3b was observed at 195 K rather than 77 K, demonstrating the temperature-controlled framework flexibility. It also exhibited high selectivity and storage capacity for carbon dioxide over methane and nitrogen at room temperature. Moreover, 3b also demonstrated potential to separate organic chemicals with similar boiling points, such as benzene and cyclohexane, via pressure swing adsorption process.

Chemical/Physical Pressure Tunable Spin-Transition Temperature and Hysteresis in a Two-Step Spin Crossover Porous Coordination Framework

A two-dimensional (2D) square-grid type porous coordination polymer [Fe(bdpt)(2)]·guest (1·g, Hbdpt = 3-(5-bromo-2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole) with isolated small cavities was designed and constructed as a spin-crossover (SCO) material based on octahedral Fe(II)N(6) units and an all-nitrogen ligand. Three guest-inclusion forms were successfully prepared for 1·g (1·EtOH for g = ethanol, 1·MeOH for g = methanol, 1 for g = Null), in which the guest molecules interact with the framework as hydrogen-bonding donors. Magnetic susceptibility measurements showed that 1·g exhibited two-step SCO behavior with different transition temperatures (1·EtOH < 1·MeOH < 1) and hysteresis widths (1·EtOH > 1·MeOH > 1 ≈ 0). Such guest modulation of two-step spin crossover temperature and hysteresis without changing two-step state in a porous coordination framework is unprecedented. X-ray single-crystal structural analyses revealed that all two-step SCO processes were accompanied with interesting symmetry-breaking phase transitions from space group of P2(1)/n for all high-spin Fe(II), to P1 for ordered half high-spin and half low-spin Fe(II), and back to P2(1)/n for all low-spin Fe(II) again by lowering temperature. The different SCO behaviors of 1·g were elucidated by the steric mechanism and guest-host hydrogen-bonding interactions. The SCO behavior of 1·g can be also controlled by external physical pressure.

Syntheses, structures and sorption properties of two framework-isomeric porous copper-coordination polymers†

Solvothermal and solution reactions of a V-shaped organic ligand 4,4′-oxybis(benzoic acid) (H2oba) and Cu(NO3)2 yield two porous coordination polymers, namely [Cu(oba)(dmso)] (MCF-21) and [Cu2(oba)2(dmf)(C2H5OH)]·(dmf)2(H2O) (MCF-22·guest) (dmso = dimethyl sulfoxide, dmf = dimethylformamide), respectively. Single-crystal X-ray analyses reveal that the metal carboxylate backbones of MCF-21 and MCF-22·guest are framework-isomeric as two uninodal four-connected nets, i.e. a two-dimensional (2-D) 44 layer and a 3-fold interpenetrated lvt (4284) three-dimensional (3-D) network, respectively. After removing the solvent molecules, MCF-21 retains a rigid 2-D framework, but MCF-22·guest exhibits either rigid or dynamic behavior depending on the degree of desolvation, which is confirmed by powder X-ray diffraction and sorption isotherms. Meanwhile, the different sorption behavior of the framework-isomeric materials is elucidated by the discrepancies of their pore dimensions and framework rigidities.

3D geometrically frustrated magnets assembled by transition metal ion and 1,2,3-triazole-4,5-dicarboxylate as triangular nodes†

Three new chiral metal–organic frameworks, (H2NMe2)[M(tzdc)]·0.5H2O [MCo(II) (1), Mn(II) (2)] and (NH4)[Mn(tzdc)]·2.6H2O (3) (tzdc3− = 1,2,3-triazole-4,5-dicarboxylate), have been solvothermally synthesized. In the frameworks of 1–3, the ratio of metal and tzdc3− is 1 : 1. Each metal ion is chelated by three tzdc3− ligands, and each tzdc3− connects three metal ions, resulting in three-dimensional, 3-connected anionic frameworks. 1 and 2 are isomorphous, and both crystallize in the cubic space groupP213. With the template of H2NMe2+ cations, the frameworks of 1 and 2 have a well-known, porous (10,3)-a network. In contrast, 3 can be obtained by replacing the H2NMe2+ with smaller NH4+ cations, which leads to a significant topological change to a unique uniform etd (8,3) network as well as the change of the space group to P61. Magnetic studies show dominated antiferromagnetic interactions in 1–3 with θ = −46.8(1), −22.3(1) and −25.8(1) K for 1, 2 and 3, respectively. Due to the triangular arrangement of the metal centres, geometrically spin-frustrated magnetism is a characteristic behaviour of 1–3. For 1, spin-glassy behaviour with a freezing temperature Tf of 2.4 K was distinctly observed, and an empirical factor f = |θ |/Tf ≈ 20 > 10 indicates strong spin-frustration effect. For both 2 and 3, no obvious long-range magnetic ordering and/or spin–glassy behaviour was observed down to 2.0 K, which might indicate the f values in them being also larger than 10. By contrast, the observed spin-glassy behaviour above 2.0 K in 1 is probably due to the stronger magnetic anisotropy of Co(II) ion and the stronger antiferromagnetic interactions in 1.